From: Kees Cook <kees.cook@canonical.com>
To: Roland McGrath <roland@redhat.com>, linux-kernel@vger.kernel.org
Cc: Jakub Jelinek <jakub@redhat.com>,
Ulrich Drepper <drepper@redhat.com>,
libc-alpha@sourceware.org
Subject: [PATCH] ELF: implement AT_RANDOM for future glibc use
Date: Thu, 2 Oct 2008 17:16:16 -0700 [thread overview]
Message-ID: <20081003001616.GN10632@outflux.net> (raw)
In-Reply-To: <20081001222706.68E7E1544B4@magilla.localdomain>
While discussing[1] the need for glibc to have access to random bytes
during program load, it seems that an earlier attempt to implement
AT_RANDOM got stalled. This implements a configurable number of random
bytes available to every ELF program via a new auxv AT_RANDOM vector.
[1] http://sourceware.org/ml/libc-alpha/2008-10/msg00006.html
Signed-off-by: Kees Cook <kees.cook@canonical.com>
---
fs/binfmt_elf.c | 20 ++++++++++++++++++++
include/linux/auxvec.h | 4 +++-
security/Kconfig | 9 +++++++++
3 files changed, 32 insertions(+), 1 deletions(-)
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 655ed8d..9b2ea62 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -152,6 +152,8 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec,
elf_addr_t __user *sp;
elf_addr_t __user *u_platform;
elf_addr_t __user *u_base_platform;
+ elf_addr_t __user *u_rand_bytes;
+ unsigned int rand_size;
const char *k_platform = ELF_PLATFORM;
const char *k_base_platform = ELF_BASE_PLATFORM;
int items;
@@ -196,6 +198,18 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec,
return -EFAULT;
}
+ rand_size = CONFIG_SECURITY_AUXV_RANDOM_SIZE * sizeof(unsigned long);
+ u_rand_bytes = NULL;
+ if (rand_size) {
+ unsigned char k_rand_bytes[CONFIG_SECURITY_AUXV_RANDOM_SIZE *
+ sizeof(unsigned long)];
+ get_random_bytes(k_rand_bytes, rand_size);
+
+ u_rand_bytes = (elf_addr_t __user *)STACK_ALLOC(p, rand_size);
+ if (__copy_to_user(u_rand_bytes, k_rand_bytes, rand_size))
+ return -EFAULT;
+ }
+
/* Create the ELF interpreter info */
elf_info = (elf_addr_t *)current->mm->saved_auxv;
/* update AT_VECTOR_SIZE_BASE if the number of NEW_AUX_ENT() changes */
@@ -228,6 +242,12 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec,
NEW_AUX_ENT(AT_GID, tsk->gid);
NEW_AUX_ENT(AT_EGID, tsk->egid);
NEW_AUX_ENT(AT_SECURE, security_bprm_secureexec(bprm));
+ if (rand_size) {
+ NEW_AUX_ENT(AT_RANDOM_SIZE,
+ (elf_addr_t)(unsigned long)rand_size);
+ NEW_AUX_ENT(AT_RANDOM,
+ (elf_addr_t)(unsigned long)u_rand_bytes);
+ }
NEW_AUX_ENT(AT_EXECFN, bprm->exec);
if (k_platform) {
NEW_AUX_ENT(AT_PLATFORM,
diff --git a/include/linux/auxvec.h b/include/linux/auxvec.h
index d7afa9d..df4ff65 100644
--- a/include/linux/auxvec.h
+++ b/include/linux/auxvec.h
@@ -23,6 +23,8 @@
#define AT_PLATFORM 15 /* string identifying CPU for optimizations */
#define AT_HWCAP 16 /* arch dependent hints at CPU capabilities */
#define AT_CLKTCK 17 /* frequency at which times() increments */
+#define AT_RANDOM 18 /* address of random bytes */
+#define AT_RANDOM_SIZE 19 /* number of random bytes at AT_RANDOM */
#define AT_SECURE 23 /* secure mode boolean */
@@ -32,7 +34,7 @@
#define AT_EXECFN 31 /* filename of program */
#ifdef __KERNEL__
-#define AT_VECTOR_SIZE_BASE 18 /* NEW_AUX_ENT entries in auxiliary table */
+#define AT_VECTOR_SIZE_BASE 20 /* NEW_AUX_ENT entries in auxiliary table */
/* number of "#define AT_.*" above, minus {AT_NULL, AT_IGNORE, AT_NOTELF} */
#endif
diff --git a/security/Kconfig b/security/Kconfig
index f6c0429..8d9d49d 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -114,6 +114,15 @@ config SECURITY_DEFAULT_MMAP_MIN_ADDR
This value can be changed after boot using the
/proc/sys/vm/mmap_min_addr tunable.
+config SECURITY_AUXV_RANDOM_SIZE
+ int "Number of random longs to store in AT_RANDOM on every exec"
+ default 4
+ help
+ This value determines the size of the random longs provided
+ to programs via the auxv AT_RANDOM vector. It can be used
+ to initialize random values needed during program load.
+
+ If you are unsure how many longs to use, answer 4.
source security/selinux/Kconfig
source security/smack/Kconfig
--
1.5.6.3
--
Kees Cook
Ubuntu Security Team
next parent reply other threads:[~2008-10-03 0:17 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20081001201116.GD12527@outflux.net>
[not found] ` <48E3EFD6.2010704@redhat.com>
[not found] ` <20081001215657.GH12527@outflux.net>
[not found] ` <20081001220948.GC32107@sunsite.ms.mff.cuni.cz>
[not found] ` <20081001222706.68E7E1544B4@magilla.localdomain>
2008-10-03 0:16 ` Kees Cook [this message]
2008-10-03 0:43 ` [PATCH] ELF: implement AT_RANDOM for future glibc use Jakub Jelinek
2008-10-03 5:25 ` Kees Cook
2008-10-03 5:29 ` Kees Cook
2008-10-03 5:57 ` Arjan van de Ven
2008-10-03 6:25 ` Ulrich Drepper
2008-10-03 14:50 ` [PATCH] ELF: implement AT_RANDOM for glibc PRNG seeding Kees Cook
2008-10-03 14:56 ` Ulrich Drepper
2008-10-03 14:57 ` Jakub Jelinek
2008-10-03 17:33 ` Kees Cook
2008-10-03 17:41 ` Ulrich Drepper
2008-10-03 17:59 ` [PATCH v5] " Kees Cook
2008-10-18 5:42 ` Ulrich Drepper
2008-10-21 20:01 ` Andrew Morton
2008-10-21 20:22 ` Ulrich Drepper
2008-10-27 5:46 ` Andrew Morton
2008-10-03 0:52 ` [PATCH] ELF: implement AT_RANDOM for future glibc use Roland McGrath
2008-10-03 5:15 ` Kees Cook
2008-10-03 20:22 ` Roland McGrath
2008-10-06 6:00 ` Andi Kleen
2008-10-06 17:50 ` Kees Cook
2008-10-06 18:25 ` David Wagner
2008-10-06 20:23 ` Andi Kleen
2008-10-06 22:16 ` David Wagner
2008-10-06 19:26 ` Andi Kleen
2008-10-06 22:01 ` Kees Cook
2008-10-06 23:19 ` Andi Kleen
2008-10-06 23:29 ` Kees Cook
2008-10-06 23:44 ` Andi Kleen
2008-10-06 22:07 ` Kees Cook
2008-10-06 23:28 ` Andi Kleen
2008-10-06 23:58 ` Roland McGrath
2008-10-07 0:08 ` Ulrich Drepper
2008-10-07 0:31 ` Kees Cook
2008-10-07 0:57 ` Ulrich Drepper
2008-10-07 1:44 ` Kees Cook
2008-10-07 1:51 ` Ulrich Drepper
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