diff options
| -rw-r--r-- | sys/man/2/memory | 23 |
1 files changed, 22 insertions, 1 deletions
diff --git a/sys/man/2/memory b/sys/man/2/memory index 42bcc0555..30c5cfb1e 100644 --- a/sys/man/2/memory +++ b/sys/man/2/memory @@ -1,6 +1,6 @@ .TH MEMORY 2 .SH NAME -memccpy, memchr, memcmp, memcpy, memmove, memset \- memory operations +memccpy, memchr, memcmp, memcpy, memmove, memset, tsmemcmp \- memory operations .SH SYNOPSIS .B #include <u.h> .br @@ -24,6 +24,11 @@ void* memmove(void *s1, void *s2, ulong n) .PP .B void* memset(void *s, int c, ulong n) +.PP +.B #include <libsec.h> +.PP +.B +int tsmemcmp(void *s1, void *s2, ulong n) .SH DESCRIPTION These functions operate efficiently on memory areas (arrays of bytes bounded by a count, not terminated by a zero byte). @@ -103,11 +108,22 @@ to the value of byte .IR c . It returns .IR s . +.PP +.I Tsmemcmp +is a variant of +.I memcmp +that is safe against timing attacks. +It does not stop when it sees a difference, this way it's runtime is function of +.I n +and not something that can lead clues to attackers. .SH SOURCE All these routines have portable C implementations in .BR /sys/src/libc/port . Most also have machine-dependent assembly language implementations in .BR /sys/src/libc/$objtype . +.I Tsmemcmp +is found on +.BR /sys/src/libsec/port/tsmemcmp.c . .SH SEE ALSO .IR strcat (2) .SH BUGS @@ -124,3 +140,8 @@ If and .I memmove are handed a negative count, they abort. +.PP +.I Memcmp +should not be used to compare sensitive data as it's vulnerable to timing attacks. Instead, +.I tsmemcmp +should be used. |