commit 309467c64e007ea6841c07fdee35eaff0146d541 Author: Nick Mathewson <nickm@torproject.org> Date: Tue Apr 30 14:43:35 2019 -0400 Rename tor_mem_is_zero to fast_mem_is_zero() 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. --- changes/bug30309 | 3 +++ src/lib/string/util_string.c | 9 +++------ src/lib/string/util_string.h | 8 +++++++- 3 files changed, 13 insertions(+), 7 deletions(-) diff --git a/changes/bug30309 b/changes/bug30309 new file mode 100644 index 000000000..6cbbe8d15 --- /dev/null +++ b/changes/bug30309 @@ -0,0 +1,3 @@ + o Code simplification and refactoring: + - Rename tor_mem_is_zero() to fast_mem_is_zero(), to emphasize that + it is not a constant-time function. Closes ticket 30309. diff --git a/src/lib/string/util_string.c b/src/lib/string/util_string.c index 0c4e39900..f5061a11d 100644 --- a/src/lib/string/util_string.c +++ b/src/lib/string/util_string.c @@ -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 diff --git a/src/lib/string/util_string.h b/src/lib/string/util_string.h index da4fab159..7e8af0578 100644 --- a/src/lib/string/util_string.h +++ b/src/lib/string/util_string.h @@ -20,7 +20,13 @@ const void *tor_memmem(const void *haystack, size_t hlen, const void *needle, size_t nlen); const void *tor_memstr(const void *haystack, size_t hlen, const char *needle); -int tor_mem_is_zero(const char *mem, size_t len); +int fast_mem_is_zero(const char *mem, size_t len); +#define fast_digest_is_zero(d) fast_mem_is_zero((d), DIGEST_LEN) +#define fast_digetst256_is_zero(d) fast_mem_is_zero((d), DIGEST256_LEN) + +// XXXX remove this after we replace all users. +#define tor_mem_is_zero fast_mem_is_zero + int tor_digest_is_zero(const char *digest); int tor_digest256_is_zero(const char *digest);