LSM: add SafeSetID module that gates setid calls
This change ensures that the set*uid family of syscalls in kernel/sys.c
(setreuid, setuid, setresuid, setfsuid) all call ns_capable_common with
the CAP_OPT_INSETID flag, so capability checks in the security_capable
hook can know whether they are being called from within a set*uid
syscall. This change is a no-op by itself, but is needed for the
proposed SafeSetID LSM.
Signed-off-by: Micah Morton <mortonm@chromium.org>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: James Morris <james.morris@microsoft.com>
diff --git a/include/linux/capability.h b/include/linux/capability.h
index f640dcb..c3f9a4d 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -209,6 +209,7 @@
extern bool capable(int cap);
extern bool ns_capable(struct user_namespace *ns, int cap);
extern bool ns_capable_noaudit(struct user_namespace *ns, int cap);
+extern bool ns_capable_setid(struct user_namespace *ns, int cap);
#else
static inline bool has_capability(struct task_struct *t, int cap)
{
@@ -240,6 +241,10 @@
{
return true;
}
+static inline bool ns_capable_setid(struct user_namespace *ns, int cap)
+{
+ return true;
+}
#endif /* CONFIG_MULTIUSER */
extern bool privileged_wrt_inode_uidgid(struct user_namespace *ns, const struct inode *inode);
extern bool capable_wrt_inode_uidgid(const struct inode *inode, int cap);