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security: Add LSM hook to setgroups() syscall

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Give the LSM framework the ability to filter setgroups() syscalls. There
are already analagous hooks for the set*uid() and set*gid() syscalls.
The SafeSetID LSM will use this new hook to ensure setgroups() calls are
allowed by the installed security policy. Tested by putting print
statement in security_task_fix_setgroups() hook and confirming that it
gets hit when userspace does a setgroups() syscall.

Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Micah Morton <mortonm@chromium.org>
This commit is contained in:
Micah Morton 2022-06-08 20:57:11 +00:00
parent a1732d6898
commit fcfe0ac2fc
5 changed files with 33 additions and 0 deletions
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1
include/linux/lsm_hook_defs.h
View file

@ -201,6 +201,7 @@ LSM_HOOK(int, 0, task_fix_setuid, struct cred *new, const struct cred *old,
int flags)
LSM_HOOK(int, 0, task_fix_setgid, struct cred *new, const struct cred * old,
int flags)
LSM_HOOK(int, 0, task_fix_setgroups, struct cred *new, const struct cred * old)
LSM_HOOK(int, 0, task_setpgid, struct task_struct *p, pid_t pgid)
LSM_HOOK(int, 0, task_getpgid, struct task_struct *p)
LSM_HOOK(int, 0, task_getsid, struct task_struct *p)

7
include/linux/lsm_hooks.h
View file

@ -702,6 +702,13 @@
* @old is the set of credentials that are being replaced.
* @flags contains one of the LSM_SETID_* values.
* Return 0 on success.
* @task_fix_setgroups:
* Update the module's state after setting the supplementary group
* identity attributes of the current process.
* @new is the set of credentials that will be installed. Modifications
* should be made to this rather than to @current->cred.
* @old is the set of credentials that are being replaced.
* Return 0 on success.
* @task_setpgid:
* Check permission before setting the process group identifier of the
* process @p to @pgid.

7
include/linux/security.h
View file

@ -415,6 +415,7 @@ int security_task_fix_setuid(struct cred *new, const struct cred *old,
int flags);
int security_task_fix_setgid(struct cred *new, const struct cred *old,
int flags);
int security_task_fix_setgroups(struct cred *new, const struct cred *old);
int security_task_setpgid(struct task_struct *p, pid_t pgid);
int security_task_getpgid(struct task_struct *p);
int security_task_getsid(struct task_struct *p);
@ -1098,6 +1099,12 @@ static inline int security_task_fix_setgid(struct cred *new,
return 0;
}
static inline int security_task_fix_setgroups(struct cred *new,
const struct cred *old)
{
return 0;
}
static inline int security_task_setpgid(struct task_struct *p, pid_t pgid)
{
return 0;

13
kernel/groups.c
View file

@ -134,13 +134,26 @@ EXPORT_SYMBOL(set_groups);
int set_current_groups(struct group_info *group_info)
{
struct cred *new;
const struct cred *old;
int retval;
new = prepare_creds();
if (!new)
return -ENOMEM;
old = current_cred();
set_groups(new, group_info);
retval = security_task_fix_setgroups(new, old);
if (retval < 0)
goto error;
return commit_creds(new);
error:
abort_creds(new);
return retval;
}
EXPORT_SYMBOL(set_current_groups);

5
security/security.c
View file

@ -1803,6 +1803,11 @@ int security_task_fix_setgid(struct cred *new, const struct cred *old,
return call_int_hook(task_fix_setgid, 0, new, old, flags);
}
int security_task_fix_setgroups(struct cred *new, const struct cred *old)
{
return call_int_hook(task_fix_setgroups, 0, new, old);
}
int security_task_setpgid(struct task_struct *p, pid_t pgid)
{
return call_int_hook(task_setpgid, 0, p, pgid);