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Diffstat (limited to 'Documentation/admin-guide/LSM/SafeSetID.rst')
| -rw-r--r-- | Documentation/admin-guide/LSM/SafeSetID.rst | 29 |
1 files changed, 20 insertions, 9 deletions
diff --git a/Documentation/admin-guide/LSM/SafeSetID.rst b/Documentation/admin-guide/LSM/SafeSetID.rst index 7bff07ce4fdd..0ec34863c674 100644 --- a/Documentation/admin-guide/LSM/SafeSetID.rst +++ b/Documentation/admin-guide/LSM/SafeSetID.rst @@ -3,9 +3,9 @@ SafeSetID ========= SafeSetID is an LSM module that gates the setid family of syscalls to restrict UID/GID transitions from a given UID/GID to only those approved by a -system-wide whitelist. These restrictions also prohibit the given UIDs/GIDs +system-wide allowlist. These restrictions also prohibit the given UIDs/GIDs from obtaining auxiliary privileges associated with CAP_SET{U/G}ID, such as -allowing a user to set up user namespace UID mappings. +allowing a user to set up user namespace UID/GID mappings. Background @@ -98,10 +98,21 @@ Directions for use ================== This LSM hooks the setid syscalls to make sure transitions are allowed if an applicable restriction policy is in place. Policies are configured through -securityfs by writing to the safesetid/add_whitelist_policy and -safesetid/flush_whitelist_policies files at the location where securityfs is -mounted. The format for adding a policy is '<UID>:<UID>', using literal -numbers, such as '123:456'. To flush the policies, any write to the file is -sufficient. Again, configuring a policy for a UID will prevent that UID from -obtaining auxiliary setid privileges, such as allowing a user to set up user -namespace UID mappings. +securityfs by writing to the safesetid/uid_allowlist_policy and +safesetid/gid_allowlist_policy files at the location where securityfs is +mounted. The format for adding a policy is '<UID>:<UID>' or '<GID>:<GID>', +using literal numbers, and ending with a newline character such as '123:456\n'. +Writing an empty string "" will flush the policy. Again, configuring a policy +for a UID/GID will prevent that UID/GID from obtaining auxiliary setid +privileges, such as allowing a user to set up user namespace UID/GID mappings. + +Note on GID policies and setgroups() +==================================== +In v5.9 we are adding support for limiting CAP_SETGID privileges as was done +previously for CAP_SETUID. However, for compatibility with common sandboxing +related code conventions in userspace, we currently allow arbitrary +setgroups() calls for processes with CAP_SETGID restrictions. Until we add +support in a future release for restricting setgroups() calls, these GID +policies add no meaningful security. setgroups() restrictions will be enforced +once we have the policy checking code in place, which will rely on GID policy +configuration code added in v5.9. |