Thread (30 messages) 30 messages, 4 authors, 2017-09-20
STALE3232d REVIEWED: 1 (0M)
Revisions (6)
  1. v3 [diff vs current]
  2. v3 [diff vs current]
  3. v3 [diff vs current]
  4. v4 [diff vs current]
  5. v4 current
  6. v5 [diff vs current]

[PATCH V4 06/10] capabilities: move audit log decision to function

From: Kees Cook <hidden>
Date: 2017-09-08 18:23:50

On Mon, Sep 4, 2017 at 11:46 PM, Richard Guy Briggs [off-list ref] wrote:
Move the audit log decision logic to its own function to isolate the
complexity in one place.

Suggested-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Richard Guy Briggs <redacted>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Acked-by: James Morris <redacted>
Acked-by: Kees Cook <redacted>

-Kees
quoted hunk ↗ jump to hunk
---
 security/commoncap.c |   50 ++++++++++++++++++++++++++++++--------------------
 1 files changed, 30 insertions(+), 20 deletions(-)
diff --git a/security/commoncap.c b/security/commoncap.c
index d37ebec..eae7431 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -527,6 +527,32 @@ static inline bool __is_setuid(struct cred *new, const struct cred *old)
 static inline bool __is_setgid(struct cred *new, const struct cred *old)
 { return !gid_eq(new->egid, old->gid); }

+/*
+ * Audit candidate if current->cap_effective is set
+ *
+ * We do not bother to audit if 3 things are true:
+ *   1) cap_effective has all caps
+ *   2) we are root
+ *   3) root is supposed to have all caps (SECURE_NOROOT)
+ * Since this is just a normal root execing a process.
+ *
+ * Number 1 above might fail if you don't have a full bset, but I think
+ * that is interesting information to audit.
+ */
+static inline bool nonroot_raised_pE(struct cred *cred, kuid_t root)
+{
+       bool ret = false;
+
+       if (__cap_grew(effective, ambient, cred)) {
+               if (!__cap_full(effective, cred) ||
+                   !__is_eff(root, cred) || !__is_real(root, cred) ||
+                   !root_privileged()) {
+                       ret = true;
+               }
+       }
+       return ret;
+}
+
 /**
  * cap_bprm_set_creds - Set up the proposed credentials for execve().
  * @bprm: The execution parameters, including the proposed creds
@@ -604,26 +630,10 @@ int cap_bprm_set_creds(struct linux_binprm *bprm)
        if (WARN_ON(!cap_ambient_invariant_ok(new)))
                return -EPERM;

-       /*
-        * Audit candidate if current->cap_effective is set
-        *
-        * We do not bother to audit if 3 things are true:
-        *   1) cap_effective has all caps
-        *   2) we are root
-        *   3) root is supposed to have all caps (SECURE_NOROOT)
-        * Since this is just a normal root execing a process.
-        *
-        * Number 1 above might fail if you don't have a full bset, but I think
-        * that is interesting information to audit.
-        */
-       if (__cap_grew(effective, ambient, new)) {
-               if (!__cap_full(effective, new) ||
-                   !__is_eff(root_uid, new) || !__is_real(root_uid, new) ||
-                   !root_privileged()) {
-                       ret = audit_log_bprm_fcaps(bprm, new, old);
-                       if (ret < 0)
-                               return ret;
-               }
+       if (nonroot_raised_pE(new, root_uid)) {
+               ret = audit_log_bprm_fcaps(bprm, new, old);
+               if (ret < 0)
+                       return ret;
        }

        new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
--
1.7.1


-- 
Kees Cook
Pixel Security
--
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