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3.6 Security

Security in HTCondor is a broad issue, with many aspects to consider. Because HTCondor's main purpose is to allow users to run arbitrary code on large numbers of computers, it is important to try to limit who can access an HTCondor pool and what privileges they have when using the pool. This section covers these topics.

There is a distinction between the kinds of resource attacks HTCondor can defeat, and the kinds of attacks HTCondor cannot defeat. HTCondor cannot prevent security breaches of users that can elevate their privilege to the root or administrator account. HTCondor does not run user jobs in sandboxes (standard universe jobs are a partial exception to this), so HTCondor cannot defeat all malicious actions by user jobs. An example of a malicious job is one that launches a distributed denial of service attack. HTCondor assumes that users are trustworthy. HTCondor can prevent unauthorized access to the HTCondor pool, to help ensure that only trusted users have access to the pool. In addition, HTCondor provides encryption and integrity checking, to ensure that data (both HTCondor's data and user jobs' data) has not been examined or tampered with while in transit.

Broadly speaking, the aspects of security in HTCondor may be categorized and described:

Users
Authorization or capability in an operating system is based on a process owner. Both those that submit jobs and HTCondor daemons become process owners. The HTCondor system prefers that HTCondor daemons are run as the user root, while other common operations are owned by a user of HTCondor. Operations that do not belong to either root or an HTCondor user are often owned by the condor user. See Section 3.6.13 for more detail.

Authentication
Proper identification of a user is accomplished by the process of authentication. It attempts to distinguish between real users and impostors. By default, HTCondor's authentication uses the user id (UID) to determine identity, but HTCondor can choose among a variety of authentication mechanisms, including the stronger authentication methods Kerberos and GSI.

Authorization
Authorization specifies who is allowed to do what. Some users are allowed to submit jobs, while other users are allowed administrative privileges over HTCondor itself. HTCondor provides authorization on either a per-user or on a per-machine basis.

Privacy
HTCondor may encrypt data sent across the network, which prevents others from viewing the data. With persistence and sufficient computing power, decryption is possible. HTCondor can encrypt the data sent for internal communication, as well as user data, such as files and executables. Encryption operates on network transmissions: unencrypted data is stored on disk.

Integrity
The man-in-the-middle attack tampers with data without the awareness of either side of the communication. HTCondor's integrity check sends additional cryptographic data to verify that network data transmissions have not been tampered with. Note that the integrity information is only for network transmissions: data stored on disk does not have this integrity information.


3.6.1 HTCondor's Security Model

At the heart of HTCondor's security model is the notion that communications are subject to various security checks. A request from one HTCondor daemon to another may require authentication to prevent subversion of the system. A request from a user of HTCondor may need to be denied due to the confidential nature of the request. The security model handles these example situations and many more.

Requests to HTCondor are categorized into groups of access levels, based on the type of operation requested. The user of a specific request must be authorized at the required access level. For example, executing the condor_status command requires the READ access level. Actions that accomplish management tasks, such as shutting down or restarting of a daemon require an ADMINISTRATOR access level. See Section 3.6.7 for a full list of HTCondor's access levels and their meanings.

There are two sides to any communication or command invocation in HTCondor. One side is identified as the client, and the other side is identified as the daemon. The client is the party that initiates the command, and the daemon is the party that processes the command and responds. In some cases it is easy to distinguish the client from the daemon, while in other cases it is not as easy. HTCondor tools such as condor_submit and condor_config_val are clients. They send commands to daemons and act as clients in all their communications. For example, the condor_submit command communicates with the condor_schedd. Behind the scenes, HTCondor daemons also communicate with each other; in this case the daemon initiating the command plays the role of the client. For instance, the condor_negotiator daemon acts as a client when contacting the condor_schedd daemon to initiate matchmaking. Once a match has been found, the condor_schedd daemon acts as a client and contacts the condor_startd daemon.

HTCondor's security model is implemented using configuration. Commands in HTCondor are executed over TCP/IP network connections. While network communication enables HTCondor to manage resources that are distributed across an organization (or beyond), it also brings in security challenges. HTCondor must have ways of ensuring that commands are being sent by trustworthy users. Jobs that are operating on sensitive data must be allowed to use encryption such that the data is not seen by outsiders. Jobs may need assurance that data has not been tampered with. These issues can be addressed with HTCondor's authentication, encryption, and integrity features.


3.6.1.1 Access Level Descriptions

Authorization is granted based on specified access levels. This list describes each access level, and provides examples of their usage. The levels implement a partial hierarchy; a higher level often implies a READ or both a WRITE and a READ level of access as described.

READ
This access level can obtain or read information about HTCondor. Examples that require only READ access are viewing the status of the pool with condor_status, checking a job queue with condor_q, or viewing user priorities with condor_userprio. READ access does not allow any changes, and it does not allow job submission.

WRITE
This access level is required to send (write) information to HTCondor. Examples that require WRITE access are job submission with condor_submit and advertising a machine so it appears in the pool (this is usually done automatically by the condor_startd daemon). The WRITE level of access implies READ access.

ADMINISTRATOR
This access level has additional HTCondor administrator rights to the pool. It includes the ability to change user priorities with the command condor_userprio, as well as the ability to turn HTCondor on and off (as with the commands condor_on and condor_off). The ADMINISTRATOR level of access implies both READ and WRITE access.

SOAP
This access level is required for the authorization of any party that will use the Web Services (SOAP) interface to HTCondor. It is not a general access level to be used with the variety of configuration variables for authentication, encryption, and integrity checks.

CONFIG
This access level is required to modify a daemon's configuration using the condor_config_val command. By default, this level of access can change any configuration parameters of an HTCondor pool, except those specified in the condor_config.root configuration file. The CONFIG level of access implies READ access.

OWNER
This level of access is required for commands that the owner of a machine (any local user) should be able to use, in addition to the HTCondor administrators. An example that requires the OWNER access level is the condor_vacate command. The command causes the condor_startd daemon to vacate any HTCondor job currently running on a machine. The owner of that machine should be able to cause the removal of a job running on the machine.

DAEMON
This access level is used for commands that are internal to the operation of HTCondor. An example of this internal operation is when the condor_startd daemon sends its ClassAd updates to the condor_collector daemon (which may be more specifically controlled by the ADVERTISE_STARTD access level). Authorization at this access level should only be given to the user account under which the HTCondor daemons run. The DAEMON level of access implies both READ and WRITE access. Any setting for this access level that is not defined will default to the corresponding setting in the WRITE access level.

NEGOTIATOR
This access level is used specifically to verify that commands are sent by the condor_negotiator daemon. The condor_negotiator daemon runs on the central manager of the pool. Commands requiring this access level are the ones that tell the condor_schedd daemon to begin negotiating, and those that tell an available condor_startd daemon that it has been matched to a condor_schedd with jobs to run. The NEGOTIATOR level of access implies READ access.

ADVERTISE_MASTER
This access level is used specifically for commands used to advertise a condor_master daemon to the collector. Any setting for this access level that is not defined will default to the corresponding setting in the DAEMON access level.

ADVERTISE_STARTD
This access level is used specifically for commands used to advertise a condor_startd daemon to the collector. Any setting for this access level that is not defined will default to the corresponding setting in the DAEMON access level.

ADVERTISE_SCHEDD
This access level is used specifically for commands used to advertise a condor_schedd daemon to the collector. Any setting for this access level that is not defined will default to the corresponding setting in the DAEMON access level.

CLIENT
This access level is different from all the others. Whereas all of the other access levels refer to the security policy for accepting connections from others, the CLIENT access level applies when an HTCondor daemon or tool is connecting to some other HTCondor daemon. In other words, it specifies the policy of the client that is initiating the operation, rather than the server that is being contacted.

The following is a list of registered commands that daemons will accept. The list is ordered by daemon. For each daemon, the commands are grouped by the access level required for a daemon to accept the command from a given machine.

ALL DAEMONS:

WRITE

The command sent as a result of condor_reconfig to reconfigure a daemon.

STARTD:

WRITE

All commands that relate to a condor_schedd daemon claiming a machine, starting jobs there, or stopping those jobs.

The command that condor_checkpoint sends to periodically checkpoint all running jobs.

READ

The command that condor_preen sends to request the current state of the condor_startd daemon.

OWNER
The command that condor_vacate sends to cause any running jobs to stop running.

NEGOTIATOR
The command that the condor_negotiator daemon sends to match a machine's condor_startd daemon with a given condor_schedd daemon.

NEGOTIATOR:

WRITE
The command that initiates a new negotiation cycle. It is sent by the condor_schedd when new jobs are submitted or a condor_reschedule command is issued.

READ
The command that can retrieve the current state of user priorities in the pool, sent by the condor_userprio command.

ADMINISTRATOR
The command that can set the current values of user priorities, sent as a result of the condor_userprio command.

COLLECTOR:

ADVERTISE_MASTER
Commands that update the condor_collector daemon with new condor_master ClassAds.

ADVERTISE_SCHEDD
Commands that update the condor_collector daemon with new condor_schedd ClassAds.

ADVERTISE_STARTD
Commands that update the condor_collector daemon with new condor_startd ClassAds.

DAEMON
All other commands that update the condor_collector daemon with new ClassAds. Note that the specific access levels such as ADVERTISE_STARTD default to the DAEMON settings, which in turn defaults to WRITE.

READ
All commands that query the condor_collector daemon for ClassAds.

SCHEDD:

NEGOTIATOR
The command that the condor_negotiator sends to begin negotiating with this condor_schedd to match its jobs with available condor_startds.

WRITE
The command which condor_reschedule sends to the condor_schedd to get it to update the condor_collector with a current ClassAd and begin a negotiation cycle.

The commands which write information into the job queue (such as condor_submit and condor_hold). Note that for most commands which attempt to write to the job queue, HTCondor will perform an additional user-level authentication step. This additional user-level authentication prevents, for example, an ordinary user from removing a different user's jobs.

READ
The command from any tool to view the status of the job queue.

The commands that a condor_startd sends to the condor_schedd when the condor_schedd daemon's claim is being preempted and also when the lease on the claim is renewed. These operations only require READ access, rather than DAEMON in order to limit the level of trust that the condor_schedd must have for the condor_startd. Success of these commands is only possible if the condor_startd knows the secret claim id, so effectively, authorization for these commands is more specific than HTCondor's general security model implies. The condor_schedd automatically grants the condor_startd READ access for the duration of the claim. Therefore, if one desires to only authorize specific execute machines to run jobs, one must either limit which machines are allowed to advertise themselves to the pool (most common) or configure the condor_schedd's ALLOW_CLIENT setting to only allow connections from the condor_schedd to the trusted execute machines.

MASTER: All commands are registered with ADMINISTRATOR access:

restart
: Master restarts itself (and all its children)
off
: Master shuts down all its children
off -master
: Master shuts down all its children and exits
on
: Master spawns all the daemons it is configured to spawn


3.6.2 Security Negotiation

Because of the wide range of environments and security demands necessary, HTCondor must be flexible. Configuration provides this flexibility. The process by which HTCondor determines the security settings that will be used when a connection is established is called security negotiation. Security negotiation's primary purpose is to determine which of the features of authentication, encryption, and integrity checking will be enabled for a connection. In addition, since HTCondor supports multiple technologies for authentication and encryption, security negotiation also determines which technology is chosen for the connection.

Security negotiation is a completely separate process from matchmaking, and should not be confused with any specific function of the condor_negotiator daemon. Security negotiation occurs when one HTCondor daemon or tool initiates communication with another HTCondor daemon, to determine the security settings by which the communication will be ruled. The condor_negotiator daemon does negotiation, whereby queued jobs and available machines within a pool go through the process of matchmaking (deciding out which machines will run which jobs).


3.6.2.1 Configuration

The configuration macro names that determine what features will be used during client-daemon communication follow the pattern:

    SEC_<context>_<feature>

The <feature> portion of the macro name determines which security feature's policy is being set. <feature> may be any one of

    AUTHENTICATION
    ENCRYPTION
    INTEGRITY
    NEGOTIATION

The <context> component of the security policy macros can be used to craft a fine-grained security policy based on the type of communication taking place. <context> may be any one of

    CLIENT
    READ
    WRITE
    ADMINISTRATOR
    CONFIG
    OWNER
    DAEMON
    NEGOTIATOR
    ADVERTISE_MASTER
    ADVERTISE_STARTD
    ADVERTISE_SCHEDD
    DEFAULT

Any of these constructed configuration macros may be set to any of the following values:

    REQUIRED
    PREFERRED
    OPTIONAL
    NEVER

Security negotiation resolves various client-daemon combinations of desired security features in order to set a policy.

As an example, consider Frida the scientist. Frida wants to avoid authentication when possible. She sets

    SEC_DEFAULT_AUTHENTICATION = OPTIONAL
The machine running the condor_schedd to which Frida will remotely submit jobs, however, is operated by a security-conscious system administrator who dutifully sets:
    SEC_DEFAULT_AUTHENTICATION = REQUIRED
When Frida submits her jobs, HTCondor's security negotiation determines that authentication will be used, and allows the command to continue. This example illustrates the point that the most restrictive security policy sets the levels of security enforced. There is actually more to the understanding of this scenario. Some HTCondor commands, such as the use of condor_submit to submit jobs always require authentication of the submitter, no matter what the policy says. This is because the identity of the submitter needs to be known in order to carry out the operation. Others commands, such as condor_q, do not always require authentication, so in the above example, the server's policy would force Frida's condor_q queries to be authenticated, whereas a different policy could allow condor_q to happen without any authentication.

Whether or not security negotiation occurs depends on the setting at both the client and daemon side of the configuration variable(s) defined by SEC_*_NEGOTIATION. SEC_DEFAULT_NEGOTIATION is a variable representing the entire set of configuration variables for NEGOTIATION. For the client side setting, the only definitions that make sense are REQUIRED and NEVER. For the daemon side setting, the PREFERRED value makes no sense. Table 3.1 shows how security negotiation resolves various client-daemon combinations of security negotiation policy settings. Within the table, Yes means the security negotiation will take place. No means it will not. Fail means that the policy settings are incompatible and the communication cannot continue.


Table 3.1: Resolution of security negotiation.
  Daemon Setting
  NEVER OPTIONAL REQUIRED
Client NEVER No No Fail
Setting REQUIRED Fail Yes Yes


Enabling authentication, encryption, and integrity checks is dependent on security negotiation taking place. The enabled security negotiation further sets the policy for these other features. Table 3.2 shows how security features are resolved for client-daemon combinations of security feature policy settings. Like Table 3.1, Yes means the feature will be utilized. No means it will not. Fail implies incompatibility and the feature cannot be resolved.


Table 3.2: Resolution of security features.
  Daemon Setting
  NEVER OPTIONAL PREFERRED REQUIRED
  NEVER No No No Fail
Client OPTIONAL No No Yes Yes
Setting PREFERRED No Yes Yes Yes
  REQUIRED Fail Yes Yes Yes


The enabling of encryption and/or integrity checks is dependent on authentication taking place. The authentication provides a key exchange. The key is needed for both encryption and integrity checks.

Setting SEC_CLIENT_<feature> determines the policy for all outgoing commands. The policy for incoming commands (the daemon side of the communication) takes a more fine-grained approach that implements a set of access levels for the received command. For example, it is desirable to have all incoming administrative requests require authentication. Inquiries on pool status may not be so restrictive. To implement this, the administrator configures the policy:

SEC_ADMINISTRATOR_AUTHENTICATION = REQUIRED
SEC_READ_AUTHENTICATION          = OPTIONAL

The DEFAULT value for <context> provides a way to set a policy for all access levels (READ, WRITE, etc.) that do not have a specific configuration variable defined. In addition, some access levels will default to the settings specified for other access levels. For example, ADVERTISE_STARTD defaults to DAEMON, and DAEMON defaults to WRITE, which then defaults to the general DEFAULT setting.


3.6.2.2 Configuration for Security Methods

Authentication and encryption can each be accomplished by a variety of methods or technologies. Which method is utilized is determined during security negotiation.

The configuration macros that determine the methods to use for authentication and/or encryption are

SEC_<context>_AUTHENTICATION_METHODS
SEC_<context>_CRYPTO_METHODS

These macros are defined by a comma or space delimited list of possible methods to use. Section 3.6.3 lists all implemented authentication methods. Section 3.6.5 lists all implemented encryption methods.


3.6.3 Authentication

The client side of any communication uses one of two macros to specify whether authentication is to occur:

    SEC_DEFAULT_AUTHENTICATION
    SEC_CLIENT_AUTHENTICATION

For the daemon side, there are a larger number of macros to specify whether authentication is to take place, based upon the necessary access level:

    SEC_DEFAULT_AUTHENTICATION
    SEC_READ_AUTHENTICATION
    SEC_WRITE_AUTHENTICATION
    SEC_ADMINISTRATOR_AUTHENTICATION
    SEC_CONFIG_AUTHENTICATION
    SEC_OWNER_AUTHENTICATION
    SEC_DAEMON_AUTHENTICATION
    SEC_NEGOTIATOR_AUTHENTICATION
    SEC_ADVERTISE_MASTER_AUTHENTICATION
    SEC_ADVERTISE_STARTD_AUTHENTICATION
    SEC_ADVERTISE_SCHEDD_AUTHENTICATION

As an example, the macro defined in the configuration file for a daemon as

SEC_WRITE_AUTHENTICATION = REQUIRED
signifies that the daemon must authenticate the client for any communication that requires the WRITE access level. If the daemon's configuration contains
SEC_DEFAULT_AUTHENTICATION = REQUIRED
and does not contain any other security configuration for AUTHENTICATION, then this default defines the daemon's needs for authentication over all access levels. Where a specific macro is defined, the more specific value takes precedence over the default definition.

If authentication is to be done, then the communicating parties must negotiate a mutually acceptable method of authentication to be used. A list of acceptable methods may be provided by the client, using the macros

    SEC_DEFAULT_AUTHENTICATION_METHODS
    SEC_CLIENT_AUTHENTICATION_METHODS
A list of acceptable methods may be provided by the daemon, using the macros
    SEC_DEFAULT_AUTHENTICATION_METHODS
    SEC_READ_AUTHENTICATION_METHODS
    SEC_WRITE_AUTHENTICATION_METHODS
    SEC_ADMINISTRATOR_AUTHENTICATION_METHODS
    SEC_CONFIG_AUTHENTICATION_METHODS
    SEC_OWNER_AUTHENTICATION_METHODS
    SEC_DAEMON_AUTHENTICATION_METHODS
    SEC_NEGOTIATOR_AUTHENTICATION_METHODS
    SEC_ADVERTISE_MASTER_AUTHENTICATION_METHODS
    SEC_ADVERTISE_STARTD_AUTHENTICATION_METHODS
    SEC_ADVERTISE_SCHEDD_AUTHENTICATION_METHODS
The methods are given as a comma-separated list of acceptable values. These variables list the authentication methods that are available to be used. The ordering of the list defines preference; the first item in the list indicates the highest preference. As not all of the authentication methods work on Windows platforms, which ones do not work on Windows are indicated in the following list of defined values:
    GSI       (not available on Windows platforms)
    SSL
    KERBEROS
    PASSWORD
    FS        (not available on Windows platforms)
    FS_REMOTE (not available on Windows platforms)
    NTSSPI
    CLAIMTOBE
    ANONYMOUS

For example, a client may be configured with:

SEC_CLIENT_AUTHENTICATION_METHODS = FS, GSI
and a daemon the client is trying to contact with:
SEC_DEFAULT_AUTHENTICATION_METHODS = GSI

Security negotiation will determine that GSI authentication is the only compatible choice. If there are multiple compatible authentication methods, security negotiation will make a list of acceptable methods and they will be tried in order until one succeeds.

As another example, the macro

SEC_DEFAULT_AUTHENTICATION_METHODS = KERBEROS, NTSSPI
indicates that either Kerberos or Windows authentication may be used, but Kerberos is preferred over Windows. Note that if the client and daemon agree that multiple authentication methods may be used, then they are tried in turn. For instance, if they both agree that Kerberos or NTSSPI may be used, then Kerberos will be tried first, and if there is a failure for any reason, then NTSSPI will be tried.

An additional specialized method of authentication exists for communication between the condor_schedd and condor_startd. It is especially useful when operating at large scale over high latency networks or in situations where it is inconvenient to set up one of the other methods of strong authentication between the submit and execute daemons. See the description of SEC_ENABLE_MATCH_PASSWORD_AUTHENTICATION on [*] for details.

If the configuration for a machine does not define any variable for SEC_<access-level>_AUTHENTICATION, then HTCondor uses a default value of OPTIONAL. Authentication will be required for any operation which modifies the job queue, such as condor_qedit and condor_rm. If the configuration for a machine does not define any variable for SEC_<access-level>_AUTHENTICATION_METHODS, the default value for a Unix machine is FS, KERBEROS, GSI. This default value for a Windows machine is NTSSPI, KERBEROS, GSI.


3.6.3.1 GSI Authentication

The GSI (Grid Security Infrastructure) protocol provides an avenue for HTCondor to do PKI-based (Public Key Infrastructure) authentication using X.509 certificates. The basics of GSI are well-documented elsewhere, such as http://www.globus.org/.

A simple introduction to this type of authentication defines HTCondor's use of terminology, and it illuminates the needed items that HTCondor must access to do this authentication. Assume that A authenticates to B. In this example, A is the client, and B is the daemon within their communication. This example's one-way authentication implies that B is verifying the identity of A, using the certificate A provides, and utilizing B's own set of trusted CAs (Certification Authorities). Client A provides its certificate (or proxy) to daemon B. B does two things: B checks that the certificate is valid, and B checks to see that the CA that signed A's certificate is one that B trusts.

For the GSI authentication protocol, an X.509 certificate is required. Files with predetermined names hold a certificate, a key, and optionally, a proxy. A separate directory has one or more files that become the list of trusted CAs.

Allowing HTCondor to do this GSI authentication requires knowledge of the locations of the client A's certificate and the daemon B's list of trusted CAs. When one side of the communication (as either client A or daemon B) is an HTCondor daemon, these locations are determined by configuration or by default locations. When one side of the communication (as a client A) is a user of HTCondor (the process owner of an HTCondor tool, for example condor_submit), these locations are determined by the pre-set values of environment variables or by default locations.

GSI certificate locations for HTCondor daemons

For an HTCondor daemon, the certificate may be a single host certificate, and all HTCondor daemons on the same machine may share the same certificate. In some cases, the certificate can also be copied to other machines, where local copies are necessary. This may occur only in cases where a single host certificate can match multiple host names, something that is beyond the scope of this manual. The certificates must be protected by access rights to files, since the password file is not encrypted.

The specification of the location of the necessary files through configuration uses the following precedence.

  1. Configuration variable GSI_DAEMON_DIRECTORY gives the complete path name to the directory that contains the certificate, key, and directory with trusted CAs. HTCondor uses this directory as follows in its construction of the following configuration variables:
    GSI_DAEMON_CERT           = $(GSI_DAEMON_DIRECTORY)/hostcert.pem
    GSI_DAEMON_KEY            = $(GSI_DAEMON_DIRECTORY)/hostkey.pem 
    GSI_DAEMON_TRUSTED_CA_DIR = $(GSI_DAEMON_DIRECTORY)/certificates
    

    Note that no proxy is assumed in this case.

  2. If the GSI_DAEMON_DIRECTORY is not defined, or when defined, the location may be overridden with specific configuration variables that specify the complete path and file name of the certificate with
    GSI_DAEMON_CERT
    the key with
    GSI_DAEMON_KEY
    a proxy with
    GSI_DAEMON_PROXY
    the complete path to the directory containing the list of trusted CAs with
    GSI_DAEMON_TRUSTED_CA_DIR
  3. The default location assumed is /etc/grid-security. Note that this implemented by setting the value of GSI_DAEMON_DIRECTORY.

When a daemon acts as the client within authentication, the daemon needs a listing of those from which it will accept certificates. This is done with GSI_DAEMON_NAME. This name is specified with the following format

GSI_DAEMON_NAME = /X.509/name/of/server/1,/X.509/name/of/server/2,...

HTCondor will also need a way to map an X.509 distinguished name to an HTCondor user id. There are two ways to accomplish this mapping. For a first way to specify the mapping, see section 3.6.4 to use HTCondor's unified map file. The second way to do the mapping is within an administrator-maintained GSI-specific file called an X.509 map file, mapping from X.509 Distinguished Name (DN) to HTCondor user id. It is similar to a Globus grid map file, except that it is only used for mapping to a user id, not for authorization. If the user names in the map file do not specify a domain for the user (specification would appear as user@domain), then the value of UID_DOMAIN is used. Entries (lines) in the file each contain two items. The first item in an entry is the X.509 certificate subject name, and it is enclosed in double quote marks (using the character "). The second item is the HTCondor user id. The two items in an entry are separated by tab or space character(s). Here is an example of an entry in an X.509 map file. Entries must be on a single line; this example is broken onto two lines for formatting reasons.

"/C=US/O=Globus/O=University of Wisconsin/
OU=Computer Sciences Department/CN=Alice Smith" asmith

HTCondor finds the map file in one of three ways. If the configuration variable GRIDMAP is defined, it gives the full path name to the map file. When not defined, HTCondor looks for the map file in

$(GSI_DAEMON_DIRECTORY)/grid-mapfile
If GSI_DAEMON_DIRECTORY is not defined, then the third place HTCondor looks for the map file is given by
/etc/grid-security/grid-mapfile

GSI certificate locations for Users

The user specifies the location of a certificate, proxy, etc. in one of two ways:

  1. Environment variables give the location of necessary items.

    X509_USER_PROXY gives the path and file name of the proxy. This proxy will have been created using the grid-proxy-init program, which will place the proxy in the /tmp directory with the file name being determined by the format:

      /tmp/x509up_uXXXX
    
    The specific file name is given by substituting the XXXX characters with the UID of the user. Note that when a valid proxy is used, the certificate and key locations are not needed.

    X509_USER_CERT gives the path and file name of the certificate. It is also used if a proxy location has been checked, but the proxy is no longer valid.

    X509_USER_KEY gives the path and file name of the key. Note that most keys are password encrypted, such that knowing the location could not lead to using the key.

    X509_CERT_DIR gives the path to the directory containing the list of trusted CAs.

  2. Without environment variables to give locations of necessary certificate information, HTCondor uses a default directory for the user. This directory is given by
    $(HOME)/.globus
    

Example GSI Security Configuration

Here is an example portion of the configuration file that would enable and require GSI authentication, along with a minimal set of other variables to make it work.

SEC_DEFAULT_AUTHENTICATION = REQUIRED
SEC_DEFAULT_AUTHENTICATION_METHODS = GSI
SEC_DEFAULT_INTEGRITY = REQUIRED
GSI_DAEMON_DIRECTORY = /etc/grid-security
GRIDMAP = /etc/grid-security/grid-mapfile

# authorize based on user names produced by the map file
ALLOW_READ = *@cs.wisc.edu/*.cs.wisc.edu
ALLOW_DAEMON = condor@cs.wisc.edu/*.cs.wisc.edu
ALLOW_NEGOTIATOR = condor@cs.wisc.edu/condor.cs.wisc.edu, \
                   condor@cs.wisc.edu/condor2.cs.wisc.edu
ALLOW_ADMINISTRATOR = condor-admin@cs.wisc.edu/*.cs.wisc.edu

# condor daemon certificate(s) trusted by condor tools and daemons
# when connecting to other condor daemons
GSI_DAEMON_NAME = /C=US/O=Condor/O=UW/OU=CS/CN=condor@cs.wisc.edu

# clear out any host-based authorizations
# (unnecessary if you leave authentication REQUIRED,
#  but useful if you make it optional and want to
#  allow some unauthenticated operations, such as
#  ALLOW_READ = */*.cs.wisc.edu)
HOSTALLOW_READ =
HOSTALLOW_WRITE =
HOSTALLOW_NEGOTIATOR =
HOSTALLOW_ADMINISTRATOR =

The SEC_DEFAULT_AUTHENTICATION macro specifies that authentication is required for all communications. This single macro covers all communications, but could be replaced with a set of macros that require authentication for only specific communications.

The macro GSI_DAEMON_DIRECTORY is specified to give HTCondor a single place to find the daemon's certificate. This path may be a directory on a shared file system such as AFS. Alternatively, this path name can point to local copies of the certificate stored in a local file system.

The macro GRIDMAP specifies the file to use for mapping GSI names to user names within HTCondor. For example, it might look like this:

"/C=US/O=Condor/O=UW/OU=CS/CN=condor@cs.wisc.edu" condor@cs.wisc.edu

Additional mappings would be needed for the users who submit jobs to the pool or who issue administrative commands.


3.6.3.2 SSL Authentication

SSL authentication is similar to GSI authentication, but without GSI's delegation (proxy) capabilities. SSL utilizes X.509 certificates.

All SSL authentication is mutual authentication in HTCondor. This means that when SSL authentication is used and when one process communicates with another, each process must be able to verify the signature on the certificate presented by the other process. The process that initiates the connection is the client, and the process that receives the connection is the server. For example, when a condor_startd daemon authenticates with a condor_collector daemon to provide a machine ClassAd, the condor_startd daemon initiates the connection and acts as the client, and the condor_collector daemon acts as the server.

The names and locations of keys and certificates for clients, servers, and the files used to specify trusted certificate authorities (CAs) are defined by settings in the configuration files. The contents of the files are identical in format and interpretation to those used by other systems which use SSL, such as Apache httpd.

The configuration variables AUTH_SSL_CLIENT_CERTFILE and AUTH_SSL_SERVER_CERTFILE specify the file location for the certificate file for the initiator and recipient of connections, respectively. Similarly, the configuration variables AUTH_SSL_CLIENT_KEYFILE and AUTH_SSL_SERVER_KEYFILE specify the locations for keys.

The configuration variables AUTH_SSL_SERVER_CAFILE and AUTH_SSL_CLIENT_CAFILE each specify a path and file name, providing the location of a file containing one or more certificates issued by trusted certificate authorities. Similarly, AUTH_SSL_SERVER_CADIR and AUTH_SSL_CLIENT_CADIR each specify a directory with one or more files, each which may contain a single CA certificate. The directories must be prepared using the OpenSSL c_rehash utility.


3.6.3.3 Kerberos Authentication

If Kerberos is used for authentication, then a mapping from a Kerberos domain (called a realm) to an HTCondor UID domain is necessary. There are two ways to accomplish this mapping. For a first way to specify the mapping, see section 3.6.4 to use HTCondor's unified map file. A second way to specify the mapping defines the configuration variable KERBEROS_MAP_FILE to define a path to an administrator-maintained Kerberos-specific map file. The configuration syntax is

KERBEROS_MAP_FILE = /path/to/etc/condor.kmap

Lines within this map file have the syntax

   KERB.REALM = UID.domain.name

Here are two lines from a map file to use as an example:

   CS.WISC.EDU   = cs.wisc.edu
   ENGR.WISC.EDU = ee.wisc.edu

If a KERBEROS_MAP_FILE configuration variable is defined and set, then all permitted realms must be explicitly mapped. If no map file is specified, then HTCondor assumes that the Kerberos realm is the same as the HTCondor UID domain.

The configuration variable KERBEROS_SERVER_PRINCIPAL defines the name of a Kerberos principal. If KERBEROS_SERVER_PRINCIPAL is not defined, then the default value used is host. A principal specifies a unique name to which a set of credentials may be assigned.

HTCondor takes the specified (or default) principal and appends a slash character, the host name, an '@' (at sign character), and the Kerberos realm. As an example, the configuration

KERBEROS_SERVER_PRINCIPAL = condor-daemon
results in HTCondor's use of
condor-daemon/the.host.name@YOUR.KERB.REALM
as the server principal.

Here is an example of configuration settings that use Kerberos for authentication and require authentication of all communications of the write or administrator access level.

SEC_WRITE_AUTHENTICATION                 = REQUIRED
SEC_WRITE_AUTHENTICATION_METHODS         = KERBEROS
SEC_ADMINISTRATOR_AUTHENTICATION         = REQUIRED
SEC_ADMINISTRATOR_AUTHENTICATION_METHODS = KERBEROS

Kerberos authentication on Unix platforms requires access to various files that usually are only accessible by the root user. At this time, the only supported way to use KERBEROS authentication on Unix platforms is to start daemons HTCondor as user root.


3.6.3.4 Password Authentication

The password method provides mutual authentication through the use of a shared secret. This is often a good choice when strong security is desired, but an existing Kerberos or X.509 infrastructure is not in place. Password authentication is available on both Unix and Windows. It currently can only be used for daemon-to-daemon authentication. The shared secret in this context is referred to as the pool password.

Before a daemon can use password authentication, the pool password must be stored on the daemon's local machine. On Unix, the password will be placed in a file defined by the configuration variable SEC_PASSWORD_FILE . This file will be accessible only by the UID that HTCondor is started as. On Windows, the same secure password store that is used for user passwords will be used for the pool password (see section 7.2.3).

Under Unix, the password file can be generated by using the following command to write directly to the password file:

condor_store_cred -f /path/to/password/file

Under Windows (or under Unix), storing the pool password is done with the -c option when using to condor_store_cred add. Running

condor_store_cred -c add
prompts for the pool password and store it on the local machine, making it available for daemons to use in authentication. The condor_master must be running for this command to work.

In addition, storing the pool password to a given machine requires CONFIG-level access. For example, if the pool password should only be set locally, and only by root, the following would be placed in the global configuration file.

ALLOW_CONFIG = root@mydomain/$(IP_ADDRESS)

It is also possible to set the pool password remotely, but this is recommended only if it can be done over an encrypted channel. This is possible on Windows, for example, in an environment where common accounts exist across all the machines in the pool. In this case, ALLOW_CONFIG can be set to allow the HTCondor administrator (who in this example has an account condor common to all machines in the pool) to set the password from the central manager as follows.

ALLOW_CONFIG = condor@mydomain/$(CONDOR_HOST)
The HTCondor administrator then executes
condor_store_cred -c -n host.mydomain add
from the central manager to store the password to a given machine. Since the condor account exists on both the central manager and host.mydomain, the NTSSPI authentication method can be used to authenticate and encrypt the connection. condor_store_cred will warn and prompt for cancellation, if the channel is not encrypted for whatever reason (typically because common accounts do not exist or HTCondor's security is misconfigured).

When a daemon is authenticated using a pool password, its security principle is condor_pool@$(UID_DOMAIN), where $(UID_DOMAIN) is taken from the daemon's configuration. The ALLOW_DAEMON and ALLOW_NEGOTIATOR configuration variables for authorization should restrict access using this name. For example,

ALLOW_DAEMON = condor_pool@mydomain/*, condor@mydomain/$(IP_ADDRESS)
ALLOW_NEGOTIATOR = condor_pool@mydomain/$(CONDOR_HOST)
This configuration allows remote DAEMON-level and NEGOTIATOR-level access, if the pool password is known. Local daemons authenticated as condor@mydomain are also allowed access. This is done so local authentication can be done using another method such as FS.

Example Security Configuration Using Pool Password
The following example configuration uses pool password authentication and network message integrity checking for all communication between HTCondor daemons.

SEC_PASSWORD_FILE = $(LOCK)/pool_password
SEC_DAEMON_AUTHENTICATION = REQUIRED
SEC_DAEMON_INTEGRITY = REQUIRED
SEC_DAEMON_AUTHENTICATION_METHODS = PASSWORD
SEC_NEGOTIATOR_AUTHENTICATION = REQUIRED
SEC_NEGOTIATOR_INTEGRITY = REQUIRED
SEC_NEGOTIATOR_AUTHENTICATION_METHODS = PASSWORD
SEC_CLIENT_AUTHENTICATION_METHODS = FS, PASSWORD, KERBEROS, GSI
ALLOW_DAEMON = condor_pool@$(UID_DOMAIN)/*.cs.wisc.edu, \
               condor@$(UID_DOMAIN)/$(IP_ADDRESS)
ALLOW_NEGOTIATOR = condor_pool@$(UID_DOMAIN)/negotiator.machine.name

Example Using Pool Password for condor_startd Advertisement

One problem with the pool password method of authentication is that it involves a single, shared secret. This does not scale well with the addition of remote users who flock to the local pool. However, the pool password may still be used for authenticating portions of the local pool, while others (such as the remote condor_schedd daemons involved in flocking) are authenticated by other means.

In this example, only the condor_startd daemons in the local pool are required to have the pool password when they advertise themselves to the condor_collector daemon.

SEC_PASSWORD_FILE = $(LOCK)/pool_password
SEC_ADVERTISE_STARTD_AUTHENTICATION = REQUIRED
SEC_ADVERTISE_STARTD_INTEGRITY = REQUIRED
SEC_ADVERTISE_STARTD_AUTHENTICATION_METHODS = PASSWORD
SEC_CLIENT_AUTHENTICATION_METHODS = FS, PASSWORD, KERBEROS, GSI
ALLOW_ADVERTISE_STARTD = condor_pool@$(UID_DOMAIN)/*.cs.wisc.edu


3.6.3.5 File System Authentication

This form of authentication utilizes the ownership of a file in the identity verification of a client. A daemon authenticating a client requires the client to write a file in a specific location (/tmp). The daemon then checks the ownership of the file. The file's ownership verifies the identity of the client. In this way, the file system becomes the trusted authority. This authentication method is only appropriate for clients and daemons that are on the same computer.


3.6.3.6 File System Remote Authentication

Like file system authentication, this form of authentication utilizes the ownership of a file in the identity verification of a client. In this case, a daemon authenticating a client requires the client to write a file in a specific location, but the location is not restricted to /tmp. The location of the file is specified by the configuration variable FS_REMOTE_DIR .


3.6.3.7 Windows Authentication

This authentication is done only among Windows machines using a proprietary method. The Windows security interface SSPI is used to enforce NTLM (NT LAN Manager). The authentication is based on challenge and response, using the user's password as a key. This is similar to Kerberos. The main difference is that Kerberos provides an access token that typically grants access to an entire network, whereas NTLM authentication only verifies an identity to one machine at a time. NTSSPI is best-used in a way similar to file system authentication in Unix, and probably should not be used for authentication between two computers.


3.6.3.8 Claim To Be Authentication

Claim To Be authentication accepts any identity claimed by the client. As such, it does not authenticate. It is included in HTCondor and in the list of authentication methods for testing purposes only.


3.6.3.9 Anonymous Authentication

Anonymous authentication causes authentication to be skipped entirely. As such, it does not authenticate. It is included in HTCondor and in the list of authentication methods for testing purposes only.


3.6.4 The Unified Map File for Authentication

HTCondor's unified map file allows the mappings from authenticated names to an HTCondor canonical user name to be specified as a single list within a single file. The location of the unified map file is defined by the configuration variable CERTIFICATE_MAPFILE ; it specifies the path and file name of the unified map file. Each mapping is on its own line of the unified map file. Each line contains 3 fields, separated by white space (space or tab characters):

  1. The name of the authentication method to which the mapping applies.
  2. A regular expression representing the authenticated name to be mapped.
  3. The canonical HTCondor user name.

Allowable authentication method names are the same as used to define any of the configuration variables SEC_*_AUTHENTICATION_METHODS, as repeated here:

    GSI
    SSL
    KERBEROS
    PASSWORD
    FS
    FS_REMOTE
    NTSSPI
    CLAIMTOBE
    ANONYMOUS

The fields that represent an authenticated name and the canonical HTCondor user name may utilize regular expressions as defined by PCRE (Perl-Compatible Regular Expressions). Due to this, more than one line (mapping) within the unified map file may match. Look ups are therefore defined to use the first mapping that matches.

A regular expression may need to contain spaces, and in this case the entire expression can be surrounded by double quote marks. If a double quote character also needs to appear in such an expression, it is preceded by a backslash.

The default behavior of HTCondor when no map file is specified is to do the following mappings, with some additional logic noted below:

FS (.*) \1
FS_REMOTE (.*) \1
GSI (.*) GSS_ASSIST_GRIDMAP
SSL (.*) ssl@unmapped
KERBEROS ([^/]*)/?[^@]*@(.*) \1@\2
NTSSPI (.*) \1
CLAIMTOBE (.*) \1
PASSWORD (.*) \1

For GSI (or SSL), the special name GSS_ASSIST_GRIDMAP instructs HTCondor to use the GSI grid map file (configured with GRIDMAP as shown in section 3.6.3) to do the mapping. If no mapping can be found for GSI (with or without the use of GSS_ASSIST_GRIDMAP), the user is mapped to gsi@unmapped.

For Kerberos, if KERBEROS_MAP_FILE is specified, the domain portion of the name is obtained by mapping the Kerberos realm to the value specified in the map file, rather than just using the realm verbatim as the domain portion of the condor user name. See section 3.6.3 for details.

If authentication did not happen or failed and was not required, then the user is given the name unauthenticated@unmapped.

With the integration of VOMS for GSI authentication, the interpretation of the regular expression representing the authenticated name may change. First, the full serialized DN and FQAN are used in attempting a match. If no match is found using the full DN and FQAN, then the DN is then used on its own without the FQAN. Using this, roles or user names from the VOMS attributes may be extracted to be used as the target for mapping. And, in this case the FQAN are verified, permitting reliance on their authenticity.


3.6.5 Encryption

Encryption provides privacy support between two communicating parties. Through configuration macros, both the client and the daemon can specify whether encryption is required for further communication.

The client uses one of two macros to enable or disable encryption:

    SEC_DEFAULT_ENCRYPTION
    SEC_CLIENT_ENCRYPTION

For the daemon, there are seven macros to enable or disable encryption:

    SEC_DEFAULT_ENCRYPTION
    SEC_READ_ENCRYPTION
    SEC_WRITE_ENCRYPTION
    SEC_ADMINISTRATOR_ENCRYPTION
    SEC_CONFIG_ENCRYPTION
    SEC_OWNER_ENCRYPTION
    SEC_DAEMON_ENCRYPTION
    SEC_NEGOTIATOR_ENCRYPTION
    SEC_ADVERTISE_MASTER_ENCRYPTION
    SEC_ADVERTISE_STARTD_ENCRYPTION
    SEC_ADVERTISE_SCHEDD_ENCRYPTION

As an example, the macro defined in the configuration file for a daemon as

SEC_CONFIG_ENCRYPTION = REQUIRED
signifies that any communication that changes a daemon's configuration must be encrypted. If a daemon's configuration contains
SEC_DEFAULT_ENCRYPTION = REQUIRED
and does not contain any other security configuration for ENCRYPTION, then this default defines the daemon's needs for encryption over all access levels. Where a specific macro is present, its value takes precedence over any default given.

If encryption is to be done, then the communicating parties must find (negotiate) a mutually acceptable method of encryption to be used. A list of acceptable methods may be provided by the client, using the macros

    SEC_DEFAULT_CRYPTO_METHODS
    SEC_CLIENT_CRYPTO_METHODS
A list of acceptable methods may be provided by the daemon, using the macros
    SEC_DEFAULT_CRYPTO_METHODS
    SEC_READ_CRYPTO_METHODS
    SEC_WRITE_CRYPTO_METHODS
    SEC_ADMINISTRATOR_CRYPTO_METHODS
    SEC_CONFIG_CRYPTO_METHODS
    SEC_OWNER_CRYPTO_METHODS
    SEC_DAEMON_CRYPTO_METHODS
    SEC_NEGOTIATOR_CRYPTO_METHODS
    SEC_ADVERTISE_MASTER_CRYPTO_METHODS
    SEC_ADVERTISE_STARTD_CRYPTO_METHODS
    SEC_ADVERTISE_SCHEDD_CRYPTO_METHODS

The methods are given as a comma-separated list of acceptable values. These variables list the encryption methods that are available to be used. The ordering of the list gives preference; the first item in the list indicates the highest preference. Possible values are

    3DES
    BLOWFISH


3.6.6 Integrity

An integrity check assures that the messages between communicating parties have not been tampered with. Any change, such as addition, modification, or deletion can be detected. Through configuration macros, both the client and the daemon can specify whether an integrity check is required of further communication.

The client uses one of two macros to enable or disable an integrity check:

    SEC_DEFAULT_INTEGRITY
    SEC_CLIENT_INTEGRITY

For the daemon, there are seven macros to enable or disable an integrity check:

    SEC_DEFAULT_INTEGRITY
    SEC_READ_INTEGRITY
    SEC_WRITE_INTEGRITY
    SEC_ADMINISTRATOR_INTEGRITY
    SEC_CONFIG_INTEGRITY
    SEC_OWNER_INTEGRITY
    SEC_DAEMON_INTEGRITY
    SEC_NEGOTIATOR_INTEGRITY
    SEC_ADVERTISE_MASTER_INTEGRITY
    SEC_ADVERTISE_STARTD_INTEGRITY
    SEC_ADVERTISE_SCHEDD_INTEGRITY

As an example, the macro defined in the configuration file for a daemon as

SEC_CONFIG_INTEGRITY = REQUIRED
signifies that any communication that changes a daemon's configuration must have its integrity assured. If a daemon's configuration contains
SEC_DEFAULT_INTEGRITY = REQUIRED
and does not contain any other security configuration for INTEGRITY, then this default defines the daemon's needs for integrity checks over all access levels. Where a specific macro is present, its value takes precedence over any default given.

A signed MD5 check sum is currently the only available method for integrity checking. Its use is implied whenever integrity checks occur. If more methods are implemented, then there will be further macros to allow both the client and the daemon to specify which methods are acceptable.


3.6.7 Authorization

Authorization protects resource usage by granting or denying access requests made to the resources. It defines who is allowed to do what.

Authorization is defined in terms of users. An initial implementation provided authorization based on hosts (machines), while the current implementation relies on user-based authorization. Section 3.6.9 on Setting Up IP/Host-Based Security in HTCondor describes the previous implementation. This IP/Host-Based security still exists, and it can be used, but significantly stronger and more flexible security can be achieved with the newer authorization based on fully qualified user names. This section discusses user-based authorization.

The authorization portion of the security of an HTCondor pool is based on a set of configuration macros. The macros list which user will be authorized to issue what request given a specific access level. When a daemon is to be authorized, its user name is the login under which the daemon is executed.

These configuration macros define a set of users that will be allowed to (or denied from) carrying out various HTCondor commands. Each access level may have its own list of authorized users. A complete list of the authorization macros:

    ALLOW_READ
    ALLOW_WRITE
    ALLOW_ADMINISTRATOR
    ALLOW_CONFIG
    ALLOW_SOAP
    ALLOW_OWNER
    ALLOW_NEGOTIATOR
    ALLOW_DAEMON
    DENY_READ
    DENY_WRITE
    DENY_ADMINISTRATOR
    DENY_SOAP
    DENY_CONFIG
    DENY_OWNER
    DENY_NEGOTIATOR
    DENY_DAEMON

In addition, the following are used to control authorization of specific types of HTCondor daemons when advertising themselves to the pool. If unspecified, these default to the broader ALLOW_DAEMON and DENY_DAEMON settings.

    ALLOW_ADVERTISE_MASTER
    ALLOW_ADVERTISE_STARTD
    ALLOW_ADVERTISE_SCHEDD
    DENY_ADVERTISE_MASTER
    DENY_ADVERTISE_STARTD
    DENY_ADVERTISE_SCHEDD

Each client side of a connection may also specify its own list of trusted servers. This is done using the following settings. Note that the FS and CLAIMTOBE authentication methods are not symmetric. The client is authenticated by the server, but the server is not authenticated by the client. When the server is not authenticated to the client, only the network address of the host may be authorized and not the specific identity of the server.

  ALLOW_CLIENT
  DENY_CLIENT

The names ALLOW_CLIENT and DENY_CLIENT should be thought of as ``when I am acting as a client, these are the servers I allow or deny.'' It should not be confused with the incorrect thought ``when I am the server, these are the clients I allow or deny.''

All authorization settings are defined by a comma-separated list of fully qualified users. Each fully qualified user is described using the following format:

    username@domain/hostname
The information to the left of the slash character describes a user within a domain. The information to the right of the slash character describes one or more machines from which the user would be issuing a command. This host name may take the form of either a fully qualified host name of the form
bird.cs.wisc.edu
or an IP address of the form
128.105.128.0

An example is

zmiller@cs.wisc.edu/bird.cs.wisc.edu

Within the format, wild card characters (the asterisk, *) are allowed. The use of wild cards is limited to one wild card on either side of the slash character. A wild card character used in the host name is further limited to come at the beginning of a fully qualified host name or at the end of an IP address. For example,

*@cs.wisc.edu/bird.cs.wisc.edu
refers to any user that comes from cs.wisc.edu, where the command is originating from the machine bird.cs.wisc.edu. Another valid example,
zmiller@cs.wisc.edu/*.cs.wisc.edu
refers to commands coming from any machine within the cs.wisc.edu domain, and issued by zmiller. A third valid example,
*@cs.wisc.edu/*
refers to commands coming from any user within the cs.wisc.edu domain where the command is issued from any machine. A fourth valid example,
*@cs.wisc.edu/128.105.*
refers to commands coming from any user within the cs.wisc.edu domain where the command is issued from machines within the network that match the first two octets of the IP address.

If the set of machines is specified by an IP address, then further specification using a net mask identifies a physical set (subnet) of machines. This physical set of machines is specified using the form

network/netmask
The network is an IP address. The net mask takes one of two forms. It may be a decimal number which refers to the number of leading bits of the IP address that are used in describing a subnet. Or, the net mask may take the form of
a.b.c.d
where a, b, c, and d are decimal numbers that each specify an 8-bit mask. An example net mask is
255.255.192.0
which specifies the bit mask
11111111.11111111.11000000.00000000

A single complete example of a configuration variable that uses a net mask is

ALLOW_WRITE = joesmith@cs.wisc.edu/128.105.128.0/17
User joesmith within the cs.wisc.edu domain is given write authorization when originating from machines that match their leftmost 17 bits of the IP address.

This flexible set of configuration macros could used to define conflicting authorization. Therefore, the following protocol defines the precedence of the configuration macros.

1. DENY_* macros take precedence over ALLOW_* macros where there is a conflict. This implies that if a specific user is both denied and granted authorization, the conflict is resolved by denying access.
2. If macros are omitted, the default behavior is to grant authorization for every user.

In addition, there are some hard-coded authorization rules that cannot be modified by configuration.

  1. Connections with a name matching *@unmapped are not allowed to do any job management commands (e.g. submitting, removing, or modifying jobs). This prevents these operations from being done by unauthenticated users and users who are authenticated but lacking a name in the map file.

  2. To simplify flocking, the condor_schedd automatically grants the condor_startd READ access for the duration of a claim so that claim-related communications are possible. The condor_shadow grants the condor_starter DAEMON access so that file transfers can be done. The identity that is granted access in both these cases is the authenticated name (if available) and IP address of the condor_startd when the condor_schedd initially connects to it to request the claim. It is important that only trusted condor_startds are allowed to publish themselves to the collector or that the condor_schedd's ALLOW_CLIENT setting prevent it from allowing connections to condor_startds that it does not trust to run jobs.

  3. When SEC_ENABLE_MATCH_PASSWORD_AUTHENTICATION is true, execute-side@matchsession is automatically granted READ access to the condor_schedd and DAEMON access to the condor_shadow.


3.6.7.1 Example of Authorization Security Configuration

An example of the configuration variables for the user-side authorization is derived from the necessary access levels as described in Section 3.6.1.

ALLOW_READ            = *@cs.wisc.edu/*
ALLOW_WRITE           = *@cs.wisc.edu/*.cs.wisc.edu
ALLOW_ADMINISTRATOR   = condor-admin@cs.wisc.edu/*.cs.wisc.edu
ALLOW_CONFIG          = condor-admin@cs.wisc.edu/*.cs.wisc.edu
ALLOW_NEGOTIATOR      = condor@cs.wisc.edu/condor.cs.wisc.edu, \
                        condor@cs.wisc.edu/condor2.cs.wisc.edu
ALLOW_DAEMON          = condor@cs.wisc.edu/*.cs.wisc.edu

# Clear out any old-style HOSTALLOW settings:
HOSTALLOW_READ =
HOSTALLOW_WRITE =
HOSTALLOW_DAEMON =
HOSTALLOW_NEGOTIATOR =
HOSTALLOW_ADMINISTRATOR =
HOSTALLOW_OWNER =

This example configuration authorizes any authenticated user in the cs.wisc.edu domain to carry out a request that requires the READ access level from any machine. Any user in the cs.wisc.edu domain may carry out a request that requires the WRITE access level from any machine in the cs.wisc.edu domain. Only the user called condor-admin may carry out a request that requires the ADMINISTRATOR access level from any machine in the cs.wisc.edu domain. The administrator, logged into any machine within the cs.wisc.edu domain is authorized at the CONFIG access level. Only the negotiator daemon, running as condor on the two central managers are authorized with the NEGOTIATOR access level. And, the last line of the example presumes that there is a user called condor, and that the daemons have all been started up as this user. It authorizes only programs (which will be the daemons) running as condor to carry out requests that require the DAEMON access level, where the commands originate from any machine in the cs.wisc.edu domain.

In the local configuration file for each host, the host's owner should be authorized as the owner of the machine. An example of the entry in the local configuration file:

ALLOW_OWNER           = username@cs.wisc.edu/hostname.cs.wisc.edu
In this example the owner has a login of username, and the machine's name is represented by hostname.


3.6.7.2 Debugging Security Configuration

If the authorization policy denies a network request, an explanation of why the request was denied is printed in the log file of the daemon that denied the request. The line in the log file contains the words PERMISSION DENIED.

To get HTCondor to generate a similar explanation of why requests are accepted, add D_SECURITY to the daemon's debug options (and restart or reconfig the daemon). The line in the log file for these cases will contain the words PERMISSION GRANTED. If you do not want to see a full explanation but just want to see when requests are made, add D_COMMAND to the daemon's debug options.

If the authorization policy makes use of host or domain names, then be aware that HTCondor depends on DNS to map IP addresses to names. The security and accuracy of your DNS service is therefore a requirement. Typos in DNS mappings are an occasional source of unexpected behavior. If the authorization policy is not behaving as expected, carefully compare the names in the policy with the host names HTCondor mentions in the explanations of why requests are granted or denied.


3.6.8 Security Sessions

To set up and configure secure communications in HTCondor, authentication, encryption, and integrity checks can be used. However, these come at a cost: performing strong authentication can take a significant amount of time, and generating the cryptographic keys for encryption and integrity checks can take a significant amount of processing power.

The HTCondor system makes many network connections between different daemons. If each one of these was to be authenticated, and new keys were generated for each connection, HTCondor would not be able to scale well. Therefore, HTCondor uses the concept of sessions to cache relevant security information for future use and greatly speed up the establishment of secure communications between the various HTCondor daemons.

A new session is established the first time a connection is made from one daemon to another. Each session has a fixed lifetime after which it will expire and a new session will need to be created again. But while a valid session exists, it can be re-used as many times as needed, thereby preventing the need to continuously re-establish secure connections. Each entity of a connection will have access to a session key that proves the identity of the other entity on the opposing side of the connection. This session key is exchanged securely using a strong authentication method, such as Kerberos or GSI. Other authentication methods, such as NTSSPI, FS_REMOTE, CLAIMTOBE, and ANONYMOUS, do not support secure key exchange. An entity listening on the wire may be able to impersonate the client or server in a session that does not use a strong authentication method.

Establishing a secure session requires that either the encryption or the integrity options be enabled. If the encryption capability is enabled, then the session will be restarted using the session key as the encryption key. If integrity capability is enabled, then the check sum includes the session key even though it is not transmitted. Without either of these two methods enabled, it is possible for an attacker to use an open session to make a connection to a daemon and use that connection for nefarious purposes. It is strongly recommended that if you have authentication turned on, you should also turn on integrity and/or encryption.

The configuration parameter SEC_DEFAULT_NEGOTIATION will allow a user to set the default level of secure sessions in HTCondor. Like other security settings, the possible values for this parameter can be REQUIRED, PREFERRED, OPTIONAL, or NEVER. If you disable sessions and you have authentication turned on, then most authentication (other than commands like condor_submit) will fail because HTCondor requires sessions when you have security turned on. On the other hand, if you are not using strong security in HTCondor, but you are relying on the default host-based security, turning off sessions may be useful in certain situations. These might include debugging problems with the security session management or slightly decreasing the memory consumption of the daemons, which keep track of the sessions in use.

Session lifetimes for specific daemons are already properly configured in the default installation of HTCondor. HTCondor tools such as condor_q and condor_status create a session that expires after one minute. Theoretically they should not create a session at all, because the session cannot be reused between program invocations, but this is difficult to do in the general case. This allows a very small window of time for any possible attack, and it helps keep the memory footprint of running daemons down, because they are not keeping track of all of the sessions. The session durations may be manually tuned by using macros in the configuration file, but this is not recommended.


3.6.9 Host-Based Security in HTCondor

This section describes the mechanisms for setting up HTCondor's host-based security. This is now an outdated form of implementing security levels for machine access. It remains available and documented for purposes of backward compatibility. If used at the same time as the user-based authorization, the two specifications are merged together.

The host-based security paradigm allows control over which machines can join an HTCondor pool, which machines can find out information about your pool, and which machines within a pool can perform administrative commands. By default, HTCondor is configured to allow anyone to view or join a pool. It is recommended that this parameter is changed to only allow access from machines that you trust.

This section discusses how the host-based security works inside HTCondor. It lists the different levels of access and what parts of HTCondor use which levels. There is a description of how to configure a pool to grant or deny certain levels of access to various machines. Configuration examples and the settings of configuration variables using the condor_config_val command complete this section.

Inside the HTCondor daemons or tools that use DaemonCore (see section 3.9 for details), most tasks are accomplished by sending commands to another HTCondor daemon. These commands are represented by an integer value to specify which command is being requested, followed by any optional information that the protocol requires at that point (such as a ClassAd, capability string, etc). When the daemons start up, they will register which commands they are willing to accept, what to do with arriving commands, and the access level required for each command. When a command request is received by a daemon, HTCondor identifies the access level required and checks the IP address of the sender to verify that it satisfies the allow/deny settings from the configuration file. If permission is granted, the command request is honored; otherwise, the request will be aborted.

Settings for the access levels in the global configuration file will affect all the machines in the pool. Settings in a local configuration file will only affect the specific machine. The settings for a given machine determine what other hosts can send commands to that machine. If a machine foo is to be given administrator access on machine bar, place foo in bar's configuration file access list (not the other way around).

The following are the various access levels that commands within HTCondor can be registered with:

READ
Machines with READ access can read information from the HTCondor daemons. For example, they can view the status of the pool, see the job queue(s), and view user permissions. READ access does not allow a machine to alter any information, and does not allow job submission. A machine listed with READ permission will be unable join an HTCondor pool; the machine can only view information about the pool.

WRITE
Machines with WRITE access can write information to the HTCondor daemons. Most important for granting a machine with this access is that the machine will be able to join a pool since they are allowed to send ClassAd updates to the central manager. The machine can talk to the other machines in a pool in order to submit or run jobs. In addition, any machine with WRITE access can request the condor_startd daemon to perform periodic checkpoints on an executing job. After the checkpoint is completed, the job will continue to execute and the machine will still be claimed by the original condor_schedd daemon. This allows users on the machines where they submitted their jobs to use the condor_checkpoint command to get their jobs to periodically checkpoint, even if the users do not have an account on the machine where the jobs execute.

IMPORTANT: For a machine to join an HTCondor pool, the machine must have both WRITE permission AND READ permission. WRITE permission is not enough.

ADMINISTRATOR
Machines with ADMINISTRATOR access are granted additional HTCondor administrator rights to the pool. This includes the ability to change user priorities with the command condor_userprio, and the ability to turn HTCondor on and off using condor_on and condor_off. It is recommended that few machines be granted administrator access in a pool; typically these are the machines that are used by HTCondor and system administrators as their primary workstations, or the machines running as the pool's central manager.

IMPORTANT: Giving ADMINISTRATOR privileges to a machine grants administrator access for the pool to ANY USER on that machine. This includes any users who can run HTCondor jobs on that machine. It is recommended that ADMINISTRATOR access is granted with due diligence.

OWNER
This level of access is required for commands that the owner of a machine (any local user) should be able to use, in addition to the HTCondor administrators. For example, the condor_vacate command causes the condor_startd daemon to vacate any running HTCondor job. It requires OWNER permission, so that any user logged into a local machine can issue a condor_vacate command.

NEGOTIATOR
This access level is used specifically to verify that commands are sent by the condor_negotiator daemon. The condor_negotiator daemon runs on the central manager of the pool. Commands requiring this access level are the ones that tell the condor_schedd daemon to begin negotiating, and those that tell an available condor_startd daemon that it has been matched to a condor_schedd with jobs to run.

CONFIG
This access level is required to modify a daemon's configuration using the condor_config_val command. By default, machines with this level of access are able to change any configuration parameter, except those specified in the condor_config.root configuration file. Therefore, one should exercise extreme caution before granting this level of host-wide access. Because of the implications caused by CONFIG privileges, it is disabled by default for all hosts.

DAEMON
This access level is used for commands that are internal to the operation of HTCondor. An example of this internal operation is when the condor_startd daemon sends its ClassAd updates to the condor_collector daemon (which may be more specifically controlled by the ADVERTISE_STARTD access level). Authorization at this access level should only be given to hosts that actually run HTCondor in your pool. The DAEMON level of access implies both READ and WRITE access. Any setting for this access level that is not defined will default to the corresponding setting in the WRITE access level.

ADVERTISE_MASTER
This access level is used specifically for commands used to advertise a condor_master daemon to the collector. Any setting for this access level that is not defined will default to the corresponding setting in the DAEMON access level.

ADVERTISE_STARTD
This access level is used specifically for commands used to advertise a condor_startd daemon to the collector. Any setting for this access level that is not defined will default to the corresponding setting in the DAEMON access level.

ADVERTISE_SCHEDD
This access level is used specifically for commands used to advertise a condor_schedd daemon to the collector. Any setting for this access level that is not defined will default to the corresponding setting in the DAEMON access level.

CLIENT
This access level is different from all the others. Whereas all of the other access levels refer to the security policy for accepting connections from others, the CLIENT access level applies when an HTCondor daemon or tool is connecting to some other HTCondor daemon. In other words, it specifies the policy of the client that is initiating the operation, rather than the server that is being contacted.

ADMINISTRATOR and NEGOTIATOR access default to the central manager machine. OWNER access defaults to the local machine, as well as any machines given with ADMINISTRATOR access. CONFIG access is not granted to any machine as its default. These defaults are sufficient for most pools, and should not be changed without a compelling reason. If machines other than the default are to have to have OWNER access, they probably should also have ADMINISTRATOR access. By granting machines ADMINISTRATOR access, they will automatically have OWNER access, given how OWNER access is set within the configuration.


3.6.10 Examples of Security Configuration

Here is a sample security configuration:

ALLOW_ADMINISTRATOR = $(CONDOR_HOST)
ALLOW_OWNER = $(FULL_HOSTNAME), $(ALLOW_ADMINISTRATOR)
ALLOW_READ = *
ALLOW_WRITE = *
ALLOW_NEGOTIATOR = $(COLLECTOR_HOST)
ALLOW_NEGOTIATOR_SCHEDD = $(COLLECTOR_HOST), $(FLOCK_NEGOTIATOR_HOSTS)
ALLOW_WRITE_COLLECTOR = $(ALLOW_WRITE), $(FLOCK_FROM)
ALLOW_WRITE_STARTD    = $(ALLOW_WRITE), $(FLOCK_FROM)
ALLOW_READ_COLLECTOR  = $(ALLOW_READ), $(FLOCK_FROM)
ALLOW_READ_STARTD     = $(ALLOW_READ), $(FLOCK_FROM)
ALLOW_CLIENT = *

This example configuration presumes that the condor_collector and condor_negotiator daemons are running on the same machine.

For each access level, an ALLOW or a DENY may be added.

Multiple machine entries in the configuration files may be separated by either a space or a comma. The machines may be listed by

To resolve an entry that falls into both allow and deny: individual machines have a higher order of precedence than wild card entries, and host names with a wild card have a higher order of precedence than IP subnets. Otherwise, DENY has a higher order of precedence than ALLOW. This is how most people would intuitively expect it to work.

In addition, the above access levels may be specified on a per-daemon basis, instead of machine-wide for all daemons. Do this with the subsystem string (described in section 3.3.1 on Subsystem Names), which is one of: STARTD, SCHEDD, MASTER, NEGOTIATOR, or COLLECTOR. For example, to grant different read access for the condor_schedd:

ALLOW_READ_SCHEDD = <list of machines>

Here are more examples of configuration settings. Notice that ADMINISTRATOR access is only granted through an ALLOW setting to explicitly grant access to a small number of machines. We recommend this.


3.6.11 Changing the Security Configuration

A new security feature introduced in HTCondor version 6.3.2 enables more fine-grained control over the configuration settings that can be modified remotely with the condor_config_val command. The manual page for condor_config_val on page [*] details how to use condor_config_val to modify configuration settings remotely. Since certain configuration attributes can have a large impact on the functioning of the HTCondor system and the security of the machines in an HTCondor pool, it is important to restrict the ability to change attributes remotely.

For each security access level described, the HTCondor administrator can define which configuration settings a host at that access level is allowed to change. Optionally, the administrator can define separate lists of settable attributes for each HTCondor daemon, or the administrator can define one list that is used by all daemons.

For each command that requests a change in configuration setting, HTCondor searches all the different possible security access levels to see which, if any, the request satisfies. (Some hosts can qualify for multiple access levels. For example, any host with ADMINISTRATOR permission probably has WRITE permission also). Within the qualified access level, HTCondor searches for the list of attributes that may be modified. If the request is covered by the list, the request will be granted. If not covered, the request will be refused.

The default configuration shipped with HTCondor is exceedingly restrictive. HTCondor users or administrators cannot set configuration values from remote hosts with condor_config_val. Enabling this feature requires a change to the settings in the configuration file. Use this security feature carefully. Grant access only for attributes which you need to be able to modify in this manner, and grant access only at the most restrictive security level possible.

The most secure use of this feature allows HTCondor users to set attributes in the configuration file which are not used by HTCondor directly. These are custom attributes published by various HTCondor daemons with the <SUBSYS>_ATTRS setting described in section 3.3.5 on page [*]. It is secure to grant access only to modify attributes that are used by HTCondor to publish information. Granting access to modify settings used to control the behavior of HTCondor is not secure. The goal is to ensure no one can use the power to change configuration attributes to compromise the security of your HTCondor pool.

The control lists are defined by configuration settings that contain SETTABLE_ATTRS in their name. The name of the control lists have the following form:

<SUBSYS>.SETTABLE_ATTRS_<PERMISSION-LEVEL>

The two parts of this name that can vary are the <PERMISSION-LEVEL> and the <SUBSYS>. The <PERMISSION-LEVEL> can be any of the security access levels described earlier in this section. Examples include WRITE, OWNER, and CONFIG.

The <SUBSYS> is an optional portion of the name. It can be used to define separate rules for which configuration attributes can be set for each kind of HTCondor daemon (for example, STARTD, SCHEDD, and MASTER). There are many configuration settings that can be defined differently for each daemon that use this <SUBSYS> naming convention. See section 3.3.1 on page [*] for a list. If there is no daemon-specific value for a given daemon, HTCondor will look for SETTABLE_ATTRS_<PERMISSION-LEVEL> .

Each control list is defined by a comma-separated list of attribute names which should be allowed to be modified. The lists can contain wild cards characters (*).

Some examples of valid definitions of control lists with explanations:


3.6.12 Using HTCondor w/ Firewalls, Private Networks, and NATs

This topic is now addressed in more detail in section 3.7, which explains network communication in HTCondor.


3.6.13 User Accounts in HTCondor on Unix Platforms

On a Unix system, UIDs (User IDentification numbers) form part of an operating system's tools for maintaining access control. Each executing program has a UID, a unique identifier of a user executing the program. This is also called the real UID. A common situation has one user executing the program owned by another user. Many system commands work this way, with a user (corresponding to a person) executing a program belonging to (owned by) root. Since the program may require privileges that root has which the user does not have, a special bit in the program's protection specification (a setuid bit) allows the program to run with the UID of the program's owner, instead of the user that executes the program. This UID of the program's owner is called an effective UID.

HTCondor works most smoothly when its daemons run as root. The daemons then have the ability to switch their effective UIDs at will. When the daemons run as root, they normally leave their effective UID and GID (Group IDentification) to be those of user and group condor. This allows access to the log files without changing the ownership of the log files. It also allows access to these files when the user condor's home directory resides on an NFS server. root can not normally access NFS files.

If there is no condor user and group on the system, an administrator can specify which UID and GID the HTCondor daemons should use when they do not need root privileges in two ways: either with the CONDOR_IDS environment variable or the CONDOR_IDS configuration variable. In either case, the value should be the UID integer, followed by a period, followed by the GID integer. For example, if an HTCondor administrator does not want to create a condor user, and instead wants their HTCondor daemons to run as the daemon user (a common non-root user for system daemons to execute as), the daemon user's UID was 2, and group daemon had a GID of 2, the corresponding setting in the HTCondor configuration file would be CONDOR_IDS = 2.2.

On a machine where a job is submitted, the condor_schedd daemon changes its effective UID to root such that it has the capability to start up a condor_shadow daemon for the job. Before a condor_shadow daemon is created, the condor_schedd daemon switches back to root, so that it can start up the condor_shadow daemon with the (real) UID of the user who submitted the job. Since the condor_shadow runs as the owner of the job, all remote system calls are performed under the owner's UID and GID. This ensures that as the job executes, it can access only files that its owner could access if the job were running locally, without HTCondor.

On the machine where the job executes, the job runs either as the submitting user or as user nobody, to help ensure that the job cannot access local resources or do harm. If the UID_DOMAIN matches, and the user exists as the same UID in password files on both the submitting machine and on the execute machine, the job will run as the submitting user. If the user does not exist in the execute machine's password file and SOFT_UID_DOMAIN is True, then the job will run under the submitting user's UID anyway (as defined in the submitting machine's password file). If SOFT_UID_DOMAIN is False, and UID_DOMAIN matches, and the user is not in the execute machine's password file, then the job execution attempt will be aborted.


3.6.13.1 Running HTCondor as Non-Root

While we strongly recommend starting up the HTCondor daemons as root, we understand that it is not always possible to do so. The main problems of not running HTCondor daemons as root appear when one HTCondor installation is shared by many users on a single machine, or if machines are set up to only execute HTCondor jobs. With a submit-only installation for a single user, there is no need for or benefit from running as root.

The effects of HTCondor of running both with and without root access are classified for each daemon:

condor_startd
An HTCondor machine set up to execute jobs where the condor_startd is not started as root relies on the good will of the HTCondor users to agree to the policy configured for the condor_startd to enforce for starting, suspending, vacating, and killing HTCondor jobs. When the condor_startd is started as root, however, these policies may be enforced regardless of malicious users. By running as root, the HTCondor daemons run with a different UID than the HTCondor job. The user's job is started as either the UID of the user who submitted it, or as user nobody, depending on the UID_DOMAIN settings. Therefore, the HTCondor job cannot do anything to the HTCondor daemons. Without starting the daemons as root, all processes started by HTCondor, including the user's job, run with the same UID. Only root can switch UIDs. Therefore, a user's job could kill the condor_startd and condor_starter. By doing so, the user's job avoids getting suspended or vacated. This is nice for the job, as it obtains unlimited access to the machine, but it is awful for the machine owner or administrator. If there is trust of the users submitting jobs to HTCondor, this might not be a concern. However, to ensure that the policy chosen is enforced by HTCondor, the condor_startd should be started as root.

In addition, some system information cannot be obtained without root access on some platforms. As a result, when running without root access, the condor_startd must call other programs such as uptime, to get this information. This is much less efficient than getting the information directly from the kernel, as is done when running as root. On Linux, this information is available without root access, so it is not a concern on those platforms.

If all of HTCondor cannot be run as root, at least consider installing the condor_startd as setuid root. That would solve both problems. Barring that, install it as a setgid sys or kmem program, depending on whatever group has read access to /dev/kmem on the system. That would solve the system information problem.

condor_schedd
The biggest problem with running the condor_schedd without root access is that the condor_shadow processes which it spawns are stuck with the same UID that the condor_schedd has. This requires users to go out of their way to grant write access to user or group that the condor_schedd is run as for any files or directories their jobs write or create. Similarly, read access must be granted to their input files.

Consider installing condor_submit as a setgid condor program so that at least the stdout, stderr and user log files get created with the right permissions. If condor_submit is a setgid program, it will automatically set its umask to 002 and create group-writable files. This way, the simple case of a job that only writes to stdout and stderr will work. If users have programs that open their own files, they will need to know and set the proper permissions on the directories they submit from.

condor_master
The condor_master spawns both the condor_startd and the condor_schedd. To have both running as root, have the condor_master run as root. This happens automatically if the condor_master is started from boot scripts.

condor_negotiator and condor_collector
There is no need to have either of these daemons running as root.

condor_kbdd
On platforms that need the condor_kbdd, the condor_kbdd must run as root. If it is started as any other user, it will not work. Consider installing this program as a setuid root binary if the condor_master will not be run as root. Without the condor_kbdd, the condor_startd has no way to monitor USB mouse or keyboard activity, although it will notice keyboard activity on ttys such as xterms and remote logins.

If HTCondor is not run as root, then choose almost any user name. A common choice is to set up and use the condor user; this simplifies the setup, because HTCondor will look for its configuration files in the condor user's directory. If condor is not selected, then the configuration must be placed properly such that HTCondor can find its configuration files.

If users will be submitting jobs as a user different than the user HTCondor is running as (perhaps you are running as the condor user and users are submitting as themselves), then users have to be careful to only have file permissions properly set up to be accessible by the user HTCondor is using. In practice, this means creating world-writable directories for output from HTCondor jobs. This creates a potential security risk, in that any user on the machine where the job is submitted can alter the data, remove it, or do other undesirable things. It is only acceptable in an environment where users can trust other users.

Normally, users without root access who wish to use HTCondor on their machines create a condor home directory somewhere within their own accounts and start up the daemons (to run with the UID of the user). As in the case where the daemons run as user condor, there is no ability to switch UIDs or GIDs. The daemons run as the UID and GID of the user who started them. On a machine where jobs are submitted, the condor_shadow daemons all run as this same user. But, if other users are using HTCondor on the machine in this environment, the condor_shadow daemons for these other users' jobs execute with the UID of the user who started the daemons. This is a security risk, since the HTCondor job of the other user has access to all the files and directories of the user who started the daemons. Some installations have this level of trust, but others do not. Where this level of trust does not exist, it is best to set up a condor account and group, or to have each user start up their own Personal HTCondor submit installation.

When a machine is an execution site for an HTCondor job, the HTCondor job executes with the UID of the user who started the condor_startd daemon. This is also potentially a security risk, which is why we do not recommend starting up the execution site daemons as a regular user. Use either root or a user such as condor that exists only to run HTCondor jobs.


3.6.13.2 Running Jobs as the Nobody User

Under Unix, HTCondor runs jobs either as the user that submitted the jobs, or as the user called nobody. HTCondor uses user nobody if the value of the UID_DOMAIN configuration variable of the submitting and executing machines are different or if STARTER_ALLOW_RUNAS_OWNER is false or if the job ClassAd contains RunAsOwner=False. Under Windows, HTCondor by default runs jobs under a dynamically created local account that exists for the duration of the job, but it can optionally run the job as the user account that owns the job if STARTER_ALLOW_RUNAS_OWNER is True and the job contains RunAsOwner=True.

When HTCondor cleans up after executing a vanilla universe job, it does the best that it can by deleting all of the processes started by the job. During the life of the job, it also does its best to track the CPU usage of all processes created by the job. There are a variety of mechanisms used by HTCondor to detect all such processes, but, in general, the only foolproof mechanism is for the job to run under a dedicated execution account (as it does under Windows by default). With all other mechanisms, it is possible to fool HTCondor, and leave processes behind after HTCondor has cleaned up. In the case of a shared account, such as the Unix user nobody, it is possible for the job to leave a lurker process lying in wait for the next job run as nobody. The lurker process may prey maliciously on the next nobody user job, wreaking havoc.

HTCondor could prevent this problem by simply killing all processes run by the nobody user, but this would annoy many system administrators. The nobody user is often used for non-HTCondor system processes. It may also be used by other HTCondor jobs running on the same machine, if it is a multi-processor machine.

HTCondor provides a two-part solution to this difficulty. First, create user accounts specifically for HTCondor to use instead of user nobody. These can be low-privilege accounts, as the nobody user is. Create one of these accounts for each job execution slot per computer, so that distinct users can be used for concurrent processes. This prevents malicious behavior between processes running on distinct slots. Section 3.5.10 details slots. For a sample machine with two compute slots, create two users that are intended only to be used by HTCondor. As an example, call them cndrusr1 and cndrusr2. Tell HTCondor about these users with the SLOT<N>_USER configuration variables, where <N> is replaced with the slot number. In this example:

   SLOT1_USER = cndrusr1
   SLOT2_USER = cndrusr2

Then tell HTCondor that these accounts are intended only to be used by HTCondor, so HTCondor can kill all the processes belonging to these users upon job completion. The configuration variable DEDICATED_EXECUTE_ACCOUNT_REGEXP is introduced and set to a regular expression that matches the account names we have just created.

   DEDICATED_EXECUTE_ACCOUNT_REGEXP = cndrusr[0-9]+

Finally, tell HTCondor not to run jobs as the job owner:

   STARTER_ALLOW_RUNAS_OWNER = False

Notes:

  1. Currently, none of these configuration settings apply to standard universe jobs. Normally, standard universe jobs do not create additional processes.

  2. On Windows, SLOT<N>_USER will only work if the credential of the specified user is stored on the execute machine using condor_store_cred. See the condor_store_cred manual page (in section 11) for details of this command. However, the default behavior in Windows is to run jobs under a dynamically created dedicated execution account, so just using the default behavior is sufficient to avoid problems with lurker processes.
  3. You can tell if the starter is in fact treating the account as a dedicated account, because it will print a line such as the following in its log file:

    Tracking process family by login "cndrusr1"
    


3.6.13.3 Working Directories for Jobs

Every executing process has a notion of its current working directory. This is the directory that acts as the base for all file system access. There are two current working directories for any HTCondor job: one where the job is submitted and a second where the job executes. When a user submits a job, the submit-side current working directory is the same as for the user when the condor_submit command is issued. The initialdir submit command may change this, thereby allowing different jobs to have different working directories. This is useful when submitting large numbers of jobs. This submit-side current working directory remains unchanged for the entire life of a job. The submit-side current working directory is also the working directory of the condor_shadow daemon. This is particularly relevant for standard universe jobs, since file system access for the job goes through the condor_shadow daemon, and therefore all accesses behave as if they were executing without HTCondor.

There is also an execute-side current working directory. For standard universe jobs, it is set to the execute subdirectory of HTCondor's home directory. This directory is world-writable, since an HTCondor job usually runs as user nobody. Normally, standard universe jobs would never access this directory, since all I/O system calls are passed back to the condor_shadow daemon on the submit machine. In the event, however, that a job crashes and creates a core dump file, the execute-side current working directory needs to be accessible by the job so that it can write the core file. The core file is moved back to the submit machine, and the condor_shadow daemon is informed. The condor_shadow daemon sends e-mail to the job owner announcing the core file, and provides a pointer to where the core file resides in the submit-side current working directory.


3.6.14 Privilege Separation

Section 3.6.13 discusses why, under most circumstances, it is beneficial to run the HTCondor daemons as root. In situations where multiple users are involved or where HTCondor is responsible for enforcing a machine owner's policy, running as root is the only way for HTCondor to do its job correctly and securely.

Unfortunately, this requirement of running HTCondor as root is at odds with a well-established goal of security-conscious administrators: keeping the amount of software that runs with superuser privileges to a minimum. HTCondor's nature as a large distributed system that routinely communicates with potentially untrusted components over the network further aggravates this goal.

The privilege separation (PrivSep) effort in HTCondor aims to minimize the amount of code that needs root-level access, while still giving HTCondor the tools it needs to work properly. Note that PrivSep is currently only available for execute side functionality, and is not implemented on Windows.

In the PrivSep model, all logic in HTCondor that requires superuser privilege is contained in a small component called the PrivSep Kernel. The HTCondor daemons execute as an unprivileged account. They explicitly request action from the PrivSep Kernel whenever root-level operations are needed.

The PrivSep model then prevents the following attack scenario. In the attack scenario, an attacker has found an exploit in the condor_startd that allows for execution of arbitrary code on that daemon's behalf. This gives the attacker root access and therefore control over any machine on which the condor_startd is running as root and the exploit can be exercised. Under the PrivSep model, the condor_startd no longer runs as root. This prevents the attacker from taking arbitrary action as root. Further, limits on requested actions from the PrivSep Kernel contain and restrict the attacker's sphere of influence.

The following section describes the configuration necessary to enable PrivSep for an execute-side HTCondor installation. After this is a detailed description of the services that the PrivSep Kernel provides to HTCondor, and how it limits the allowed root-level actions.

3.6.14.1 PrivSep Configuration

The PrivSep Kernel is implemented as two programs: the condor_root_switchboard and the condor_procd. Both are contained in the sbin directory of the HTCondor distribution. When HTCondor is running in PrivSep mode, these are to be the only two HTCondor daemons that run with root privilege.

Each of these binaries must be accessible on the file system via a trusted path. A trusted path ensures that no user (other than root) can alter the binary or path to the binary referred to. To ensure that the paths to these binaries are trusted, use only root-owned directories, and set the permissions on these directories to deny write access to all but root. The binaries themselves must also be owned by root and not writable by any other. The condor_root_switchboard program additionally is installed with the setuid bit set. The following command properly sets the permissions on the condor_root_switchboard binary:

chmod 4755 /opt/condor/release/sbin/condor_root_switchboard

The PrivSep Kernel has its own configuration file. This file must be /etc/condor/privsep_config. The format of this file is different than an HTCondor configuration file. It consists of lines with ``key = value'' pairs. Lines with only white space or lines with ``#'' as the first non-white space character are ignored.

In the PrivSep Kernel configuration file, some configuration settings are interpreted as single values, while others are interpreted as lists. To populate a list with multiple values, use multiple lines with the same key. For example, the following configures the valid-dirs setting as a list with two entries:

valid-dirs = /opt/condor/execute_1
valid-dirs = /opt/condor/execute_2
It is an error to have multiple lines with the same key for a setting that is not interpreted as a list.

Some PrivSep Kernel configuration file settings require a list of UIDs or GIDs, and these allow for a more specialized syntax. User and group IDs can be specified either numerically or textually. Multiple list entries may be given on a single line using the : (colon) character as a delimiter. In addition, list entries may specify a range of IDs using a - (dash) character to separate the minimum and maximum IDs included. The * (asterisk) character on the right-hand side of such a range indicates that the range extends to the maximum possible ID. The following example builds a complex list of IDs:

valid-target-uids = nobody : nfsuser1 : nfsuser2
valid-target-uids = condor_run_1 - condor_run_8
valid-target-uids = 800 - *

If condor_run_1 maps to UID 701, and condor_run_8 maps to UID 708, then this range specifies the 8 UIDs of 701 through 708 (inclusive).

The following settings are required to configure the PrivSep Kernel:

Here is an example of a full privsep_config file. This file gives the condor account access to the PrivSep Kernel. HTCondor's use of this execute machine will be restricted to a set of eight dedicated accounts, along with the users group. HTCondor's $(EXECUTE) directory and the condor_procd executable are also specified, as required.

valid-caller-uids = condor
valid-caller-gids = condor
valid-target-uids = condor_run_1 - condor_run_8
valid-target-gids = users : condor_run_1 - condor_run_8
valid-dirs = /opt/condor/local/execute
procd-executable = /opt/condor/release/sbin/condor_procd

Once the PrivSep Kernel is properly installed and configured, HTCondor's configuration must be updated to specify that PrivSep should be used. The HTCondor configuration variable PRIVSEP_ENABLED is a boolean flag serving this purpose. In addition, HTCondor must be told where the condor_root_switchboard binary is located using the PRIVSEP_SWITCHBOARD setting. The following example illustrates:

PRIVSEP_ENABLED = True
PRIVSEP_SWITCHBOARD = $(SBIN)/condor_root_switchboard

Finally, note that while the condor_procd is in general an optional component of HTCondor, it is required when PrivSep is in use. If PRIVSEP_ENABLED is True, the condor_procd will be used regardless of the USE_PROCD setting. Details on these HTCondor configuration variables are in section 3.3.27 for PrivSep variables and section 3.3.18 for condor_procd variables.

3.6.14.2 PrivSep Kernel Interface

This section describes the root-enabled operations that the PrivSep Kernel makes available to HTCondor. The PrivSep Kernel's interface is designed to provide only operations needed by HTCondor in order to function properly. Each operation is further restricted based on the PrivSep Kernel's configuration settings.

The following list describes each action that can be performed via the PrivSep Kernel, along with the limitations enforced on how it may be used. The terms valid target users, valid target groups, and valid directories refer respectively to the settings for valid-target-uids, valid-target-gids, and valid-dirs from the PrivSep Kernel's configuration.

After launching a program as a valid target user, the PrivSep Kernel allows HTCondor limited control over its execution. The following operations are supported on a program executed via the PrivSep Kernel:

By sufficiently constraining the valid target accounts and valid directories to which the PrivSep Kernel allows access, the ability of a compromised HTCondor daemon to do damage can be considerably reduced.


3.6.15 Support for glexec

glexec is a tool that provides a sudo-like capability in a grid environment. glexec takes an X.509 proxy and a command to run as inputs, and maps the proxy to a local identity (that is, a Unix UID), which it then uses to execute the command. Like the condor_root_switchboard command, which provides similar functionality for HTCondor's PrivSep mode (see section 3.6.14), glexec must be installed as a root-owned setuid program. See http://www.nikhef.nl/grid/lcaslcmaps/glexec/ for more information about glexec.

HTCondor can interoperate with glexec, using it in a similar way to how the condor_root_switchboard is used when running HTCondor in PrivSep mode. The condor_starter uses glexec when launching a job, in order to give the job a separate UID from that of the HTCondor daemons. glexec is also used when performing maintenance actions such as cleaning up a job's files and processes, which cannot be done well directly under the HTCondor daemons' UID due to permissions. A consequence of this type of integration with glexec is that the execution of a single HTCondor job results in several glexec invocations, and each must map the proxy to the same UID. It is thus important to ensure that glexec is configured to provide this guarantee.

Configuration for glexec support is straightforward. The boolean configuration variable GLEXEC_JOB must be set True on execute machines where glexec is to be used. HTCondor also must be given the full path to the glexec binary using the GLEXEC configuration variable. Note that HTCondor must be started as a non-root user when glexec is used. This is because when HTCondor runs as root, it can perform actions as other UIDs arbitrarily, and glexec's services are not needed. Finally, for a job to execute properly in the mode utilizing glexec, the job must be submitted with a proxy specified via the x509userproxy command in its submit description file, since a proxy is needed as input to glexec.

Earlier versions of HTCondor employed a different form of glexec support, where the condor_starter daemon ran under the same UID as the job. This feature was enabled using the GLEXEC_STARTER configuration variable. This configuration variable is no longer used, and it is replaced by the GLEXEC_JOB configuration variable, to enable usage of glexec.


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