diff options
| author | Antonio Nino Diaz <antonio.ninodiaz@arm.com> | 2017-01-16 13:25:38 +0000 |
|---|---|---|
| committer | Antonio Nino Diaz <antonio.ninodiaz@arm.com> | 2017-01-24 14:42:12 +0000 |
| commit | aa050a7bdb943ca94ab914f2a9dc508e09a57431 (patch) | |
| tree | 5a97cdc90d14dcfca121ba20ae5c97f92324231e /lib | |
| parent | 34438669d41a648e4dcf6fd93e1a1f1f7eee0482 (diff) | |
stdlib: Import timingsafe_bcmp() from FreeBSD
Some side-channel attacks involve an attacker inferring something from
the time taken for a memory compare operation to complete, for example
when comparing hashes during image authentication. To mitigate this,
timingsafe_bcmp() must be used for such operations instead of the
standard memcmp().
This function executes in constant time and so doesn't leak any timing
information to the caller.
Change-Id: I470a723dc3626a0ee6d5e3f7fd48d0a57b8aa5fd
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/stdlib/stdlib.mk | 3 | ||||
| -rw-r--r-- | lib/stdlib/timingsafe_bcmp.c | 36 |
2 files changed, 38 insertions, 1 deletions
diff --git a/lib/stdlib/stdlib.mk b/lib/stdlib/stdlib.mk index 4ff405fb..53327174 100644 --- a/lib/stdlib/stdlib.mk +++ b/lib/stdlib/stdlib.mk @@ -42,7 +42,8 @@ STDLIB_SRCS := $(addprefix lib/stdlib/, \ strlen.c \ strncmp.c \ strnlen.c \ - subr_prf.c) + subr_prf.c \ + timingsafe_bcmp.c) INCLUDES += -Iinclude/lib/stdlib \ -Iinclude/lib/stdlib/sys diff --git a/lib/stdlib/timingsafe_bcmp.c b/lib/stdlib/timingsafe_bcmp.c new file mode 100644 index 00000000..d0981580 --- /dev/null +++ b/lib/stdlib/timingsafe_bcmp.c @@ -0,0 +1,36 @@ +/* $OpenBSD: timingsafe_bcmp.c,v 1.3 2015/08/31 02:53:57 guenther Exp $ */ +/* + * Copyright (c) 2010 Damien Miller. All rights reserved. + * + * Permission to use, copy, modify, and distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + */ + +#include <sys/cdefs.h> +__FBSDID("$FreeBSD$"); + +#include <string.h> + +int __timingsafe_bcmp(const void *, const void *, size_t); + +int +__timingsafe_bcmp(const void *b1, const void *b2, size_t n) +{ + const unsigned char *p1 = b1, *p2 = b2; + int ret = 0; + + for (; n > 0; n--) + ret |= *p1++ ^ *p2++; + return (ret != 0); +} + +__weak_reference(__timingsafe_bcmp, timingsafe_bcmp); |