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diff --git a/modules/pam_namespace/README b/modules/pam_namespace/README new file mode 100644 index 0000000..106a073 --- /dev/null +++ b/modules/pam_namespace/README @@ -0,0 +1,227 @@ +pam_namespace — PAM module for configuring namespace for a session + +━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ + +DESCRIPTION + +The pam_namespace PAM module sets up a private namespace for a session with +polyinstantiated directories. A polyinstantiated directory provides a different +instance of itself based on user name, or when using SELinux, user name, +security context or both. If an executable script /etc/security/namespace.init +exists, it is used to initialize the instance directory after it is set up and +mounted on the polyinstantiated directory. The script receives the +polyinstantiated directory path, the instance directory path, flag whether the +instance directory was newly created (0 for no, 1 for yes), and the user name +as its arguments. + +The pam_namespace module disassociates the session namespace from the parent +namespace. Any mounts/unmounts performed in the parent namespace, such as +mounting of devices, are not reflected in the session namespace. To propagate +selected mount/unmount events from the parent namespace into the disassociated +session namespace, an administrator may use the special shared-subtree feature. +For additional information on shared-subtree feature, please refer to the mount +(8) man page and the shared-subtree description at http://lwn.net/Articles/ +159077 and http://lwn.net/Articles/159092. + +OPTIONS + +debug + + A lot of debug information is logged using syslog + +unmnt_remnt + + For programs such as su and newrole, the login session has already setup a + polyinstantiated namespace. For these programs, polyinstantiation is + performed based on new user id or security context, however the command + first needs to undo the polyinstantiation performed by login. This argument + instructs the command to first undo previous polyinstantiation before + proceeding with new polyinstantiation based on new id/context + +unmnt_only + + For trusted programs that want to undo any existing bind mounts and process + instance directories on their own, this argument allows them to unmount + currently mounted instance directories + +require_selinux + + If selinux is not enabled, return failure + +gen_hash + + Instead of using the security context string for the instance name, + generate and use its md5 hash. + +ignore_config_error + + If a line in the configuration file corresponding to a polyinstantiated + directory contains format error, skip that line process the next line. + Without this option, pam will return an error to the calling program + resulting in termination of the session. + +ignore_instance_parent_mode + + Instance parent directories by default are expected to have the restrictive + mode of 000. Using this option, an administrator can choose to ignore the + mode of the instance parent. This option should be used with caution as it + will reduce security and isolation goals of the polyinstantiation + mechanism. + +unmount_on_close + + Explicitly unmount the polyinstantiated directories instead of relying on + automatic namespace destruction after the last process in a namespace + exits. This option should be used only in case it is ensured by other means + that there cannot be any processes running in the private namespace left + after the session close. It is also useful only in case there are multiple + pam session calls in sequence from the same process. + +use_current_context + + Useful for services which do not change the SELinux context with setexeccon + call. The module will use the current SELinux context of the calling + process for the level and context polyinstantiation. + +use_default_context + + Useful for services which do not use pam_selinux for changing the SELinux + context with setexeccon call. The module will use the default SELinux + context of the user for the level and context polyinstantiation. + +mount_private + + This option can be used on systems where the / mount point or its submounts + are made shared (for example with a mount --make-rshared / command). The + module will mark the whole directory tree so any mount and unmount + operations in the polyinstantiation namespace are private. Normally the + pam_namespace will try to detect the shared / mount point and make the + polyinstantiated directories private automatically. This option has to be + used just when only a subtree is shared and / is not. + + Note that mounts and unmounts done in the private namespace will not affect + the parent namespace if this option is used or when the shared / mount + point is autodetected. + +DESCRIPTION + +The pam_namespace.so module allows setup of private namespaces with +polyinstantiated directories. Directories can be polyinstantiated based on user +name or, in the case of SELinux, user name, sensitivity level or complete +security context. If an executable script /etc/security/namespace.init exists, +it is used to initialize the namespace every time an instance directory is set +up and mounted. The script receives the polyinstantiated directory path and the +instance directory path as its arguments. + +The /etc/security/namespace.conf file specifies which directories are +polyinstantiated, how they are polyinstantiated, how instance directories would +be named, and any users for whom polyinstantiation would not be performed. + +When someone logs in, the file namespace.conf is scanned. Comments are marked +by # characters. Each non comment line represents one polyinstantiated +directory. The fields are separated by spaces but can be quoted by " characters +also escape sequences \b, \n, and \t are recognized. The fields are as follows: + +polydir instance_prefix method list_of_uids + +The first field, polydir, is the absolute pathname of the directory to +polyinstantiate. The special string $HOME is replaced with the user's home +directory, and $USER with the username. This field cannot be blank. + +The second field, instance_prefix is the string prefix used to build the +pathname for the instantiation of <polydir>. Depending on the polyinstantiation +method it is then appended with "instance differentiation string" to generate +the final instance directory path. This directory is created if it did not +exist already, and is then bind mounted on the <polydir> to provide an instance +of <polydir> based on the <method> column. The special string $HOME is replaced +with the user's home directory, and $USER with the username. This field cannot +be blank. + +The third field, method, is the method used for polyinstantiation. It can take +these values; "user" for polyinstantiation based on user name, "level" for +polyinstantiation based on process MLS level and user name, "context" for +polyinstantiation based on process security context and user name, "tmpfs" for +mounting tmpfs filesystem as an instance dir, and "tmpdir" for creating +temporary directory as an instance dir which is removed when the user's session +is closed. Methods "context" and "level" are only available with SELinux. This +field cannot be blank. + +The fourth field, list_of_uids, is a comma separated list of user names for +whom the polyinstantiation is not performed. If left blank, polyinstantiation +will be performed for all users. If the list is preceded with a single "~" +character, polyinstantiation is performed only for users in the list. + +The method field can contain also following optional flags separated by : +characters. + +create=mode,owner,group - create the polyinstantiated directory. The mode, +owner and group parameters are optional. The default for mode is determined by +umask, the default owner is the user whose session is opened, the default group +is the primary group of the user. + +iscript=path - path to the instance directory init script. The base directory +for relative paths is /etc/security/namespace.d. + +noinit - instance directory init script will not be executed. + +shared - the instance directories for "context" and "level" methods will not +contain the user name and will be shared among all users. + +mntopts=value - value of this flag is passed to the mount call when the tmpfs +mount is done. It allows for example the specification of the maximum size of +the tmpfs instance that is created by the mount call. In addition to options +specified in the tmpfs(5) manual the nosuid, noexec, and nodev flags can be +used to respectively disable setuid bit effect, disable running executables, +and disable devices to be interpreted on the mounted tmpfs filesystem. + +The directory where polyinstantiated instances are to be created, must exist +and must have, by default, the mode of 0000. The requirement that the instance +parent be of mode 0000 can be overridden with the command line option +ignore_instance_parent_mode + +In case of context or level polyinstantiation the SELinux context which is used +for polyinstantiation is the context used for executing a new process as +obtained by getexeccon. This context must be set by the calling application or +pam_selinux.so module. If this context is not set the polyinstatiation will be +based just on user name. + +The "instance differentiation string" is <user name> for "user" method and +<user name>_<raw directory context> for "context" and "level" methods. If the +whole string is too long the end of it is replaced with md5sum of itself. Also +when command line option gen_hash is used the whole string is replaced with +md5sum of itself. + +EXAMPLES + +These are some example lines which might be specified in /etc/security/ +namespace.conf. + + + # The following three lines will polyinstantiate /tmp, + # /var/tmp and user's home directories. /tmp and /var/tmp + # will be polyinstantiated based on the security level + # as well as user name, whereas home directory will be + # polyinstantiated based on the full security context and user name. + # Polyinstantiation will not be performed for user root + # and adm for directories /tmp and /var/tmp, whereas home + # directories will be polyinstantiated for all users. + # + # Note that instance directories do not have to reside inside + # the polyinstantiated directory. In the examples below, + # instances of /tmp will be created in /tmp-inst directory, + # where as instances of /var/tmp and users home directories + # will reside within the directories that are being + # polyinstantiated. + # + /tmp /tmp-inst/ level root,adm + /var/tmp /var/tmp/tmp-inst/ level root,adm + $HOME $HOME/$USER.inst/inst- context + + +For the <service>s you need polyinstantiation (login for example) put the +following line in /etc/pam.d/<service> as the last line for session group: + +session required pam_namespace.so [arguments] + +This module also depends on pam_selinux.so setting the context. + |