Re: [PATCH v2 2/2] capabilities: Add a securebit to disable PR_CAP_AMBIENT_RAISE
From: Serge E. Hallyn <hidden>
Date: 2015-05-23 19:45:42
Also in:
lkml
On Thu, May 14, 2015 at 11:39:49PM -0700, Andy Lutomirski wrote:
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 [off-list ref] Cc: Kees Cook <redacted> Cc: Christoph Lameter <redacted> Cc: Serge Hallyn <redacted> Cc: Andy Lutomirski <redacted> Cc: Jonathan Corbet <redacted> Cc: Aaron Jones <redacted> CC: Ted Ts'o <redacted> Cc: linux-security-module-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Cc: linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Cc: akpm-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org Cc: Andrew G. Morgan <redacted> Cc: Mimi Zohar <redacted> Cc: Austin S Hemmelgarn <redacted> Cc: Markku Savela <msa-kXoF896ld44xHbG02/KK1g@public.gmane.org> Cc: Jarkko Sakkinen <jarkko.sakkinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org> Cc: Michael Kerrisk <redacted> Signed-off-by: Andy Lutomirski <redacted>
Interesting - at first I thought this wouldn't please Andrew as he'd want the inverse, but I guess this way keeps the pure-capabilities mode (with SECURE_ALL_BITS set) ambient-free which I suppose is really the important thing. Acked-by: Serge Hallyn <redacted>
quoted hunk ↗ jump to hunk
--- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/