Per Andrew Morgan's request, add a securebit to allow admins to
disable PR_CAP_AMBIENT_RAISE. This securebit will prevent processes
from adding capabilities to their ambient set.
For simplicity, this disables PR_CAP_AMBIENT_RAISE entirely rather
than just disabling setting previously cleared bits.
Requested-by: Andrew G. Morgan <mor...@kernel.org>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Christoph Lameter <c...@linux.com>
Cc: Serge Hallyn <serge.hal...@canonical.com>
Cc: Andy Lutomirski <l...@amacapital.net>
Cc: Jonathan Corbet <cor...@lwn.net>
Cc: Aaron Jones <aaronmdjo...@gmail.com>
CC: Ted Ts'o <ty...@mit.edu>
Cc: linux-security-mod...@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-...@vger.kernel.org
Cc: a...@linuxfoundation.org
Cc: Andrew G. Morgan <mor...@kernel.org>
Cc: Mimi Zohar <zo...@linux.vnet.ibm.com>
Cc: Austin S Hemmelgarn <ahferro...@gmail.com>
Cc: Markku Savela <m...@moth.iki.fi>
Cc: Jarkko Sakkinen <jarkko.sakki...@linux.intel.com>
Cc: Michael Kerrisk <mtk.manpa...@gmail.com>
Signed-off-by: Andy Lutomirski <l...@kernel.org>
---
include/uapi/linux/securebits.h | 11 ++++++++++-
security/commoncap.c | 3 ++-
2 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/include/uapi/linux/securebits.h b/include/uapi/linux/securebits.h
index 985aac9e6bf8..35ac35cef217 100644
--- a/include/uapi/linux/securebits.h
+++ b/include/uapi/linux/securebits.h
@@ -43,9 +43,18 @@
#define SECBIT_KEEP_CAPS (issecure_mask(SECURE_KEEP_CAPS))
#define SECBIT_KEEP_CAPS_LOCKED (issecure_mask(SECURE_KEEP_CAPS_LOCKED))
+/* When set, a process cannot add new capabilities to its ambient set. */
+#define SECURE_NO_CAP_AMBIENT_RAISE 6
+#define SECURE_NO_CAP_AMBIENT_RAISE_LOCKED 7 /* make bit-6 immutable */
+
+#define SECBIT_NO_CAP_AMBIENT_RAISE
(issecure_mask(SECURE_NO_CAP_AMBIENT_RAISE))
+#define SECBIT_NO_CAP_AMBIENT_RAISE_LOCKED \
+ (issecure_mask(SECURE_NO_CAP_AMBIENT_RAISE_LOCKED))
+
#define SECURE_ALL_BITS (issecure_mask(SECURE_NOROOT) | \
issecure_mask(SECURE_NO_SETUID_FIXUP) | \
- issecure_mask(SECURE_KEEP_CAPS))
+ issecure_mask(SECURE_KEEP_CAPS) | \
+ issecure_mask(SECURE_NO_CAP_AMBIENT_RAISE))
#define SECURE_ALL_LOCKS (SECURE_ALL_BITS << 1)
#endif /* _UAPI_LINUX_SECUREBITS_H */
diff --git a/security/commoncap.c b/security/commoncap.c
index 09541a6a85a0..98aa1b129c12 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -983,7 +983,8 @@ int cap_task_prctl(int option, unsigned long arg2, unsigned
long arg3,
if (arg2 == PR_CAP_AMBIENT_RAISE &&
(!cap_raised(current_cred()->cap_permitted, arg3) ||
!cap_raised(current_cred()->cap_inheritable,
- arg3)))
+ arg3) ||
+ issecure(SECURE_NO_CAP_AMBIENT_RAISE)))
return -EPERM;
new = prepare_creds();
--
2.1.0
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