projects / apple / libc.git / blame
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| fc5ea90f A |
1 | .\" $OpenBSD: timingsafe_bcmp.3,v 1.2 2014/06/21 20:22:15 tedu Exp $ |
| 2 | .\" | |
| 3 | .\" Copyright (c) 2014 Google Inc. | |
| 4 | .\" | |
| 5 | .\" Permission to use, copy, modify, and distribute this software for any | |
| 6 | .\" purpose with or without fee is hereby granted, provided that the above | |
| 7 | .\" copyright notice and this permission notice appear in all copies. | |
| 8 | .\" | |
| 9 | .\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES | |
| 10 | .\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF | |
| 11 | .\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR | |
| 12 | .\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES | |
| 13 | .\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN | |
| 14 | .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF | |
| 15 | .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. | |
| 16 | .\" | |
| 17 | .\" $FreeBSD$ | |
| 18 | .Dd August 15, 2016 | |
| 19 | .Dt TIMINGSAFE_BCMP 3 | |
| 20 | .Os | |
| 21 | .Sh NAME | |
| 22 | .Nm timingsafe_bcmp | |
| 23 | .Nd timing-safe byte sequence comparisons | |
| 24 | .Sh SYNOPSIS | |
| 25 | .In string.h | |
| 26 | .Ft int | |
| 27 | .Fn timingsafe_bcmp "const void *b1" "const void *b2" "size_t len" | |
| 28 | .Sh DESCRIPTION | |
| 29 | The | |
| 30 | .Fn timingsafe_bcmp | |
| 31 | function compares the first | |
| 32 | .Fa len | |
| 33 | bytes pointed to by | |
| 34 | .Fa b1 | |
| 35 | and | |
| 36 | .Fa b2 . | |
| 37 | .Pp | |
| 38 | Additionally, the running time is independent of the byte sequences compared, | |
| 39 | making it safe to use for comparing secret values such as cryptographic MACs. | |
| 40 | In contrast, | |
| 41 | .Xr bcmp 3 | |
| 42 | and | |
| 43 | .Xr memcmp 3 | |
| 44 | may short-circuit after finding the first differing byte. | |
| 45 | .Sh RETURN VALUES | |
| 46 | The | |
| 47 | .Fn timingsafe_bcmp | |
| 48 | function returns 0 or not zero if the byte sequence pointed to by | |
| 49 | .Fa b1 | |
| 50 | compares equal to or not equal to (respectively) | |
| 51 | the byte sequence pointed to by | |
| 52 | .Fa b2 . | |
| 53 | .Sh SEE ALSO | |
| 54 | .Xr bcmp 3 | |
| 55 | .Sh STANDARDS | |
| 56 | The | |
| 57 | .Fn timingsafe_bcmp | |
| 58 | function is a non-standard extension. | |
| 59 | .Sh HISTORY | |
| 60 | The | |
| 61 | .Fn timingsafe_bcmp | |
| 62 | function first appeared in | |
| 63 | .Ox 4.9 , | |
| 64 | .Fx 12.0 , | |
| 65 | and macOS 10.12.1. |