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sha1: fix zeroing storage

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Compilers remove dead assignments in optimization phase. But SHA1 code
uses them for wiping of sensitive data.  Fix this with the trick used
by openssl.
This commit is contained in:
Dmitry Podgorny
2020-06-18 22:14:04 +03:00
parent 7f5ce7d2ae
commit bef411f319
1 changed files with 16 additions and 5 deletions
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21
src/sha1.c
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@@ -126,6 +126,13 @@ static uint32_t host_to_be(uint32_t i)
#undef le_to_be
}
static void *(*volatile SHA1_explicit_memset)(void *, int, size_t) = &memset;
static void SHA1_cleanse(void *p, size_t len)
{
SHA1_explicit_memset(p, 0, len);
}
/* Hash a single 512-bit block. This is the core of the algorithm. */
static void SHA1_Transform(uint32_t state[5], const uint8_t buffer[64])
{
@@ -179,7 +186,11 @@ static void SHA1_Transform(uint32_t state[5], const uint8_t buffer[64])
state[4] += e;
/* Wipe variables */
a = b = c = d = e = 0;
SHA1_cleanse(&a, sizeof(a));
SHA1_cleanse(&b, sizeof(b));
SHA1_cleanse(&c, sizeof(c));
SHA1_cleanse(&d, sizeof(d));
SHA1_cleanse(&e, sizeof(e));
}
/* SHA1Init - Initialize new context */
@@ -240,10 +251,10 @@ void crypto_SHA1_Final(SHA1_CTX *context, uint8_t *digest)
}
/* Wipe variables */
memset(context->buffer, 0, 64);
memset(context->state, 0, 20);
memset(context->count, 0, 8);
memset(finalcount, 0, 8); /* SWR */
SHA1_cleanse(context->buffer, 64);
SHA1_cleanse(context->state, 20);
SHA1_cleanse(context->count, 8);
SHA1_cleanse(finalcount, 8); /* SWR */
SHA1_Transform(context->state, context->buffer);
}