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authorTyler Hicks <tyhicks@canonical.com>2017-08-11 07:33:54 +0300
committerKees Cook <keescook@chromium.org>2017-08-14 23:46:45 +0300
commit0ddec0fc8900201c0897b87b762b7c420436662f (patch)
treed860565f915e9adcd57e113befc3d3bba7b3c085 /Documentation/userspace-api
parentd612b1fd8010d0d67b5287fe146b8b55bcbb8655 (diff)
downloadlinux-0ddec0fc8900201c0897b87b762b7c420436662f.tar.xz
seccomp: Sysctl to configure actions that are allowed to be logged
Adminstrators can write to this sysctl to set the seccomp actions that are allowed to be logged. Any actions not found in this sysctl will not be logged. For example, all SECCOMP_RET_KILL, SECCOMP_RET_TRAP, and SECCOMP_RET_ERRNO actions would be loggable if "kill trap errno" were written to the sysctl. SECCOMP_RET_TRACE actions would not be logged since its string representation ("trace") wasn't present in the sysctl value. The path to the sysctl is: /proc/sys/kernel/seccomp/actions_logged The actions_avail sysctl can be read to discover the valid action names that can be written to the actions_logged sysctl with the exception of "allow". SECCOMP_RET_ALLOW actions cannot be configured for logging. The default setting for the sysctl is to allow all actions to be logged except SECCOMP_RET_ALLOW. While only SECCOMP_RET_KILL actions are currently logged, an upcoming patch will allow applications to request additional actions to be logged. There's one important exception to this sysctl. If a task is specifically being audited, meaning that an audit context has been allocated for the task, seccomp will log all actions other than SECCOMP_RET_ALLOW despite the value of actions_logged. This exception preserves the existing auditing behavior of tasks with an allocated audit context. With this patch, the logic for deciding if an action will be logged is: if action == RET_ALLOW: do not log else if action == RET_KILL && RET_KILL in actions_logged: log else if audit_enabled && task-is-being-audited: log else: do not log Signed-off-by: Tyler Hicks <tyhicks@canonical.com> Signed-off-by: Kees Cook <keescook@chromium.org>
Diffstat (limited to 'Documentation/userspace-api')
-rw-r--r--Documentation/userspace-api/seccomp_filter.rst18
1 files changed, 18 insertions, 0 deletions
diff --git a/Documentation/userspace-api/seccomp_filter.rst b/Documentation/userspace-api/seccomp_filter.rst
index 35fc7cbf1d95..2d1d8ab04ac5 100644
--- a/Documentation/userspace-api/seccomp_filter.rst
+++ b/Documentation/userspace-api/seccomp_filter.rst
@@ -187,6 +187,24 @@ directory. Here's a description of each file in that directory:
program was built, differs from the set of actions actually
supported in the current running kernel.
+``actions_logged``:
+ A read-write ordered list of seccomp return values (refer to the
+ ``SECCOMP_RET_*`` macros above) that are allowed to be logged. Writes
+ to the file do not need to be in ordered form but reads from the file
+ will be ordered in the same way as the actions_avail sysctl.
+
+ It is important to note that the value of ``actions_logged`` does not
+ prevent certain actions from being logged when the audit subsystem is
+ configured to audit a task. If the action is not found in
+ ``actions_logged`` list, the final decision on whether to audit the
+ action for that task is ultimately left up to the audit subsystem to
+ decide for all seccomp return values other than ``SECCOMP_RET_ALLOW``.
+
+ The ``allow`` string is not accepted in the ``actions_logged`` sysctl
+ as it is not possible to log ``SECCOMP_RET_ALLOW`` actions. Attempting
+ to write ``allow`` to the sysctl will result in an EINVAL being
+ returned.
+
Adding architecture support
===========================