[PATCH v1] keys: Restrict KEYCTL_SESSION_TO_PARENT according to ptrace_may_access()
Mickaël Salaün
mic at digikod.net
Mon Jul 29 12:58:46 UTC 2024
A process can modify its parent's credentials with
KEYCTL_SESSION_TO_PARENT when their EUID and EGID are the same. This
doesn't take into account all possible access controls.
Enforce the same access checks as for impersonating a process.
The current credentials checks are untouch because they check against
EUID and EGID, whereas ptrace_may_access() checks against UID and GID.
Cc: David Howells <dhowells at redhat.com>
Cc: Günther Noack <gnoack at google.com>
Cc: James Morris <jmorris at namei.org>
Cc: Jann Horn <jannh at google.com>
Cc: Jarkko Sakkinen <jarkko at kernel.org>
Cc: Kees Cook <kees at kernel.org>
Cc: Paul Moore <paul at paul-moore.com>
Fixes: ee18d64c1f63 ("KEYS: Add a keyctl to install a process's session keyring on its parent [try #6]")
Signed-off-by: Mickaël Salaün <mic at digikod.net>
Link: https://lore.kernel.org/r/20240729125846.1043211-1-mic@digikod.net
---
security/keys/keyctl.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index ab927a142f51..511bf79fa14c 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -21,6 +21,7 @@
#include <linux/security.h>
#include <linux/uio.h>
#include <linux/uaccess.h>
+#include <linux/ptrace.h>
#include <keys/request_key_auth-type.h>
#include "internal.h"
@@ -1687,6 +1688,10 @@ long keyctl_session_to_parent(void)
!gid_eq(pcred->sgid, mycred->egid))
goto unlock;
+ /* The child must be allowed to impersonate its parent process. */
+ if (!ptrace_may_access(parent, PTRACE_MODE_ATTACH_REALCREDS))
+ goto unlock;
+
/* the keyrings must have the same UID */
if ((pcred->session_keyring &&
!uid_eq(pcred->session_keyring->uid, mycred->euid)) ||
base-commit: 8400291e289ee6b2bf9779ff1c83a291501f017b
--
2.45.2
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