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Add a is_zero() helper

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This commit is contained in:
Frank Denis 2015-11-13 01:48:34 +01:00
parent cc29da17c3
commit 7561a25d5a
3 changed files with 36 additions and 13 deletions
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3
src/libsodium/include/sodium/utils.h
View File

@ -40,6 +40,9 @@ int sodium_compare(const unsigned char *b1_, const unsigned char *b2_,
size_t len)
__attribute__ ((warn_unused_result));
SODIUM_EXPORT
int sodium_is_zero(const unsigned char *n, const size_t nlen);
SODIUM_EXPORT
void sodium_increment(unsigned char *n, const size_t nlen);

38
src/libsodium/sodium/utils.c
View File

@ -154,6 +154,31 @@ sodium_compare(const unsigned char *b1_, const unsigned char *b2_, size_t len)
return (int) (gt + gt + eq) - 1;
}
int
sodium_is_zero(const unsigned char *n, const size_t nlen)
{
size_t i;
unsigned char c = 0U;
for (i = (size_t) 0U; i < nlen; i++) {
c |= n[i];
}
return ((c - 1U) >> 8) & 1U;
}
void
sodium_increment(unsigned char *n, const size_t nlen)
{
size_t i;
unsigned int c = 1U << 8;
for (i = (size_t) 0U; i < nlen; i++) {
c >>= 8;
c += n[i];
n[i] = (unsigned char) c;
}
}
/* Derived from original code by CodesInChaos */
char *
sodium_bin2hex(char * const hex, const size_t hex_maxlen,
@ -568,16 +593,3 @@ sodium_mprotect_readwrite(void *ptr)
{
return _sodium_mprotect(ptr, _mprotect_readwrite);
}
void
sodium_increment(unsigned char *n, const size_t nlen)
{
size_t i;
unsigned int c = 1U << 8;
for (i = (size_t) 0U; i < nlen; i++) {
c >>= 8;
c += n[i];
n[i] = (unsigned char) c;
}
}

8
test/default/sodium_utils.c
View File

@ -105,5 +105,13 @@ int main(void)
(unsigned int) bin_len);
}
}
memset(buf1, 0, sizeof buf1);
if (sodium_is_zero(buf1, sizeof buf1) != 1) {
printf("sodium_is_zero() failed\n");
}
buf1[randombytes_uniform(sizeof buf1)]++;
if (sodium_is_zero(buf1, sizeof buf1) != 0) {
printf("sodium_is_zero() failed\n");
}
return 0;
}