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Subject: [9front] memory(2): mention tsmemcmp
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diff -r b341860aaa26 sys/man/2/memory
--- a/sys/man/2/memory	Sun Apr 25 21:49:01 2021 +0200
+++ b/sys/man/2/memory	Thu Apr 29 14:38:46 2021 +0300
@@ -24,6 +24,11 @@
 .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).
@@ -103,6 +108,11 @@
 .IR c .
 It returns
 .IR s .
+.PP
+.I Tsmemcmp
+is a variant of
+.I memcmp
+that is safe against timing attacks.
 .SH SOURCE
 All these routines have portable C implementations in
 .BR /sys/src/libc/port .
@@ -124,3 +134,8 @@
 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.