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Rename tor_mem_is_zero to fast_mem_is_zero()

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For memeq and friends, "tor_" indicates constant-time and "fast_"
indicates optimized.  I'm fine with leaving the constant-time
"safe_mem_is_zero" with its current name, but the "tor_" prefix on
the current optimized version is misleading.

Also, make the tor_digest*_is_zero() uniformly constant-time, and
add a fast_digest*_is_zero() version to use as needed.

A later commit in this branch will fix all the users of
tor_mem_is_zero().

Closes ticket 30309.
This commit is contained in:
Nick Mathewson
2019-04-30 14:43:35 -04:00
parent 847fc3280d
commit 309467c64e
3 changed files with 13 additions and 7 deletions
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src/lib/string/util_string.c
+3 -6
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@@ -71,7 +71,7 @@ tor_memstr(const void *haystack, size_t hlen, const char *needle)
/** Return true iff the 'len' bytes at 'mem' are all zero. */
int
tor_mem_is_zero(const char *mem, size_t len)
fast_mem_is_zero(const char *mem, size_t len)
{
static const char ZERO[] = {
0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0,
@@ -95,17 +95,14 @@ tor_mem_is_zero(const char *mem, size_t len)
int
tor_digest_is_zero(const char *digest)
{
static const uint8_t ZERO_DIGEST[] = {
0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0
};
return tor_memeq(digest, ZERO_DIGEST, DIGEST_LEN);
return safe_mem_is_zero(digest, DIGEST_LEN);
}
/** Return true iff the DIGEST256_LEN bytes in digest are all zero. */
int
tor_digest256_is_zero(const char *digest)
{
return tor_mem_is_zero(digest, DIGEST256_LEN);
return safe_mem_is_zero(digest, DIGEST256_LEN);
}
/** Remove from the string <b>s</b> every character which appears in