diff options
Diffstat (limited to 'lib/libc/string')
| -rw-r--r-- | lib/libc/string/Makefile.inc | 11 | ||||
| -rw-r--r-- | lib/libc/string/bcmp.3 | 31 | ||||
| -rw-r--r-- | lib/libc/string/memcmp.3 | 5 | ||||
| -rw-r--r-- | lib/libc/string/timingsafe_bcmp.3 | 92 | ||||
| -rw-r--r-- | lib/libc/string/timingsafe_memcmp.c | 46 |
5 files changed, 152 insertions, 33 deletions
diff --git a/lib/libc/string/Makefile.inc b/lib/libc/string/Makefile.inc index 1f6d756182b..a293219058a 100644 --- a/lib/libc/string/Makefile.inc +++ b/lib/libc/string/Makefile.inc @@ -1,4 +1,4 @@ -# $OpenBSD: Makefile.inc,v 1.34 2014/03/23 23:16:48 tedu Exp $ +# $OpenBSD: Makefile.inc,v 1.35 2014/06/13 02:12:17 matthew Exp $ # string sources .PATH: ${LIBCSRCDIR}/arch/${MACHINE_CPU}/string ${LIBCSRCDIR}/string @@ -7,11 +7,11 @@ SRCS+= explicit_bzero.c memccpy.c memmem.c memrchr.c stpcpy.c stpncpy.c \ strcasecmp.c strcasestr.c strcoll.c strdup.c \ strerror.c strerror_r.c strlcat.c strmode.c strndup.c strnlen.c \ strsignal.c strtok.c strxfrm.c \ + timingsafe_bcmp.c timingsafe_memcmp.c \ wcscat.c wcschr.c wcscmp.c wcscpy.c wcscspn.c wcslcat.c wcslcpy.c \ wcslen.c wcsncat.c wcsncmp.c wcsncpy.c wcspbrk.c wcsrchr.c wcsspn.c \ wcsstr.c wcstok.c wcswcs.c wcswidth.c wmemchr.c wmemcmp.c wmemcpy.c \ - wmemmove.c wmemset.c wcsdup.c \ - timingsafe_bcmp.c wcscasecmp.c + wmemmove.c wmemset.c wcsdup.c wcscasecmp.c # machine-dependent net sources # m-d Makefile.inc must include sources for: @@ -149,7 +149,8 @@ MAN+= bcmp.3 bcopy.3 bstring.3 bzero.3 ffs.3 memccpy.3 memchr.3 \ strcat.3 strchr.3 strcmp.3 strcoll.3 strcpy.3 strcspn.3 strdup.3 \ strerror.3 string.3 strlen.3 strmode.3 strncat.3 strncpy.3 strpbrk.3 \ strrchr.3 strsep.3 strsignal.3 strspn.3 strstr.3 strtok.3 strxfrm.3 \ - swab.3 strlcpy.3 wcscasecmp.3 wcscat.3 wcschr.3 wcscmp.3 wcscpy.3 \ + swab.3 strlcpy.3 timingsafe_bcmp.3 \ + wcscasecmp.3 wcscat.3 wcschr.3 wcscmp.3 wcscpy.3 \ wcscspn.3 wcsdup.3 wcslcpy.3 wcslen.3 wcspbrk.3 wcsrchr.3 wcsspn.3 \ wcsstr.3 wcstok.3 wcswidth.3 wmemchr.3 wmemcmp.3 wmemcpy.3 wmemmove.3 \ wmemset.3 @@ -167,9 +168,9 @@ MLINKS+=strlen.3 strnlen.3 MLINKS+=strstr.3 strcasestr.3 MLINKS+=strtok.3 strtok_r.3 MLINKS+=strerror.3 strerror_r.3 +MLINKS+=timingsafe_bcmp.3 timingsafe_memcmp.3 MLINKS+=wcscasecmp.3 wcsncasecmp.3 MLINKS+=wcscat.3 wcsncat.3 MLINKS+=wcscmp.3 wcsncmp.3 MLINKS+=wcscpy.3 wcsncpy.3 MLINKS+=wcslcpy.3 wcslcat.3 -MLINKS+=bcmp.3 timingsafe_bcmp.3 diff --git a/lib/libc/string/bcmp.3 b/lib/libc/string/bcmp.3 index 52584b4b838..720a8bf3040 100644 --- a/lib/libc/string/bcmp.3 +++ b/lib/libc/string/bcmp.3 @@ -27,21 +27,18 @@ .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" -.\" $OpenBSD: bcmp.3,v 1.10 2013/06/05 03:39:23 tedu Exp $ +.\" $OpenBSD: bcmp.3,v 1.11 2014/06/13 02:12:17 matthew Exp $ .\" -.Dd $Mdocdate: June 5 2013 $ +.Dd $Mdocdate: June 13 2014 $ .Dt BCMP 3 .Os .Sh NAME -.Nm bcmp , -.Nm timingsafe_bcmp +.Nm bcmp .Nd compare byte string .Sh SYNOPSIS .In string.h .Ft int .Fn bcmp "const void *b1" "const void *b2" "size_t len" -.Ft int -.Fn timingsafe_bcmp "const void *b1" "const void *b2" "size_t len" .Sh DESCRIPTION The .Fn bcmp @@ -56,33 +53,15 @@ bytes long. Zero-length strings are always identical. .Pp The strings may overlap. -.Pp -The -.Fn timingsafe_bcmp -function has the same semantics as -.Fn bcmp , -but its running time is independent of the contents of -.Fa b1 -and -.Fa b2 , -making it safe to use for comparing secret values such as cryptographic MACs. -In contrast, -.Fn bcmp -returns after finding the first differing byte, -making it vulnerable to timing attacks. .Sh SEE ALSO .Xr memcmp 3 , .Xr strcasecmp 3 , .Xr strcmp 3 , .Xr strcoll 3 , -.Xr strxfrm 3 +.Xr strxfrm 3 , +.Xr timingsafe_bcmp 3 .Sh HISTORY The .Fn bcmp function first appeared in .Bx 4.2 . -.Pp -The -.Fn timingsafe_bcmp -function first appeared in -.Ox 4.9 . diff --git a/lib/libc/string/memcmp.3 b/lib/libc/string/memcmp.3 index ebd838825ad..25d308e6171 100644 --- a/lib/libc/string/memcmp.3 +++ b/lib/libc/string/memcmp.3 @@ -1,4 +1,4 @@ -.\" $OpenBSD: memcmp.3,v 1.8 2013/06/05 03:39:23 tedu Exp $ +.\" $OpenBSD: memcmp.3,v 1.9 2014/06/13 02:12:17 matthew Exp $ .\" .\" Copyright (c) 1990, 1991 The Regents of the University of California. .\" All rights reserved. @@ -31,7 +31,7 @@ .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" -.Dd $Mdocdate: June 5 2013 $ +.Dd $Mdocdate: June 13 2014 $ .Dt MEMCMP 3 .Os .Sh NAME @@ -70,6 +70,7 @@ Zero-length strings are always identical. .Xr strcmp 3 , .Xr strcoll 3 , .Xr strxfrm 3 , +.Xr timingsafe_memcmp 3 , .Xr wmemcmp 3 .Sh STANDARDS The diff --git a/lib/libc/string/timingsafe_bcmp.3 b/lib/libc/string/timingsafe_bcmp.3 new file mode 100644 index 00000000000..0886731ce7b --- /dev/null +++ b/lib/libc/string/timingsafe_bcmp.3 @@ -0,0 +1,92 @@ +.\" $OpenBSD: timingsafe_bcmp.3,v 1.1 2014/06/13 02:12:17 matthew Exp $ +.\" +.\" Copyright (c) 2014 Google Inc. +.\" +.\" 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. +.Dd $Mdocdate: June 13 2014 $ +.Dt TIMINGSAFE_BCMP 3 +.Os +.Sh NAME +.Nm timingsafe_bcmp , +.Nm timingsafe_memcmp +.Nd timing-safe byte sequence comparisons +.Sh SYNOPSIS +.In string.h +.Ft int +.Fn timingsafe_bcmp "const void *b1" "const void *b2" "size_t len" +.Ft int +.Fn timingsafe_memcmp "const void *b1" "const void *b2" "size_t len" +.Sh DESCRIPTION +The +.Fn timingsafe_bcmp +and +.Fn timingsafe_memcmp +functions lexicographically compare the first +.Fa len +bytes (each interpreted as an +.Vt unsigned char ) +pointed to by +.Fa b1 +and +.Fa b2 . +.Pp +Additionally, their running times are independent of the byte sequences compared, +making them safe to use for comparing secret values such as cryptographic MACs. +In contrast, +.Xr bcmp 3 +and +.Xr memcmp 3 +may short-circuit after finding the first differing byte. +.Sh RETURN VALUES +The +.Fn timingsafe_bcmp +function returns 0 or 1 if the byte sequence pointed to by +.Fa b1 +compares equal to or not equal to (respectively) +the byte sequence pointed to by +.Fa b2 . +.Pp +The +.Fn timingsafe_memcmp +function returns \-1, 0, or 1 if the byte sequence pointed to by +.Fa b1 +compares less than, equal to, or greater than (respectively) +the byte sequence pointed to by +.Fa b2 . +.Pp +Note that these return values are compatible with, but stricter than, +the ones specified for +.Xr bcmp 3 +and +.Xr memcmp 3 . +.Sh SEE ALSO +.Xr bcmp 3 , +.Xr memcmp 3 +.Sh STANDARDS +The +.Fn timingsafe_bcmp +and +.Fn timingsafe_memcmp +functions are +.Ox +extensions. +.Sh HISTORY +The +.Fn timingsafe_bcmp +function first appeared in +.Ox 4.9 . +.Pp +The +.Fn timingsafe_memcmp +function first appeared in +.Ox 5.6 . diff --git a/lib/libc/string/timingsafe_memcmp.c b/lib/libc/string/timingsafe_memcmp.c new file mode 100644 index 00000000000..04e2ac5e206 --- /dev/null +++ b/lib/libc/string/timingsafe_memcmp.c @@ -0,0 +1,46 @@ +/* $OpenBSD: timingsafe_memcmp.c,v 1.1 2014/06/13 02:12:17 matthew Exp $ */ +/* + * Copyright (c) 2014 Google Inc. + * + * 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 <limits.h> +#include <string.h> + +int +timingsafe_memcmp(const void *b1, const void *b2, size_t len) +{ + const unsigned char *p1 = b1, *p2 = b2; + size_t i; + int res = 0, done = 0; + + for (i = 0; i < len; i++) { + /* lt is -1 if p1[i] < p2[i]; else 0. */ + int lt = (p1[i] - p2[i]) >> CHAR_BIT; + + /* gt is -1 if p1[i] > p2[i]; else 0. */ + int gt = (p2[i] - p1[i]) >> CHAR_BIT; + + /* cmp is 1 if p1[i] > p2[i]; -1 if p1[i] < p2[i]; else 0. */ + int cmp = lt - gt; + + /* set res = cmp if !done. */ + res |= cmp & ~done; + + /* set done if p1[i] != p2[i]. */ + done |= lt | gt; + } + + return (res); +} |