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SHA256 fixes #1

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merged 2 commits into from
Oct 8, 2024
Merged

SHA256 fixes #1

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8c17b07
sha256: remove burnStack function
neocturne Sep 21, 2024
554e258
sha256: fix misaligned buffer read in ecdsa_sha256_update()
neocturne Sep 21, 2024
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30 changes: 12 additions & 18 deletions src/lib/sha256.c
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Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,8 @@
#define ROTL(x, n) (((x) << (n)) | ((x) >> (32 - (n))))
#define ROTR(x, n) (((x) >> (n)) | ((x) << (32 - (n))))

#define IS_ALIGNED(p, a) (!((uintptr_t)(p) & (uintptr_t)((a) - 1)))

#define Ch(x, y, z) ((z) ^ ((x) & ((y) ^ (z))))
#define Maj(x, y, z) (((x) & ((y) | (z))) | ((y) & (z)))
#define SIGMA0(x) (ROTR((x), 2) ^ ROTR((x), 13) ^ ROTR((x), 22))
Expand Down Expand Up @@ -176,16 +178,6 @@ void ecdsa_sha256_init(ecdsa_sha256_context_t *sc)
sc->bufferLength = 0L;
}

static void burnStack(int size)
{
char buf[128];

memset(buf, 0, sizeof(buf));
size -= sizeof(buf);
if (size > 0)
burnStack(size);
}

static void SHA256Guts(ecdsa_sha256_context_t *sc, const uint32_t *cbuf)
{
uint32_t buf[64];
Expand Down Expand Up @@ -388,11 +380,12 @@ static void SHA256Guts(ecdsa_sha256_context_t *sc, const uint32_t *cbuf)
sc->hash[7] += h;
}



void ecdsa_sha256_update(ecdsa_sha256_context_t *sc, const void *data, size_t len)
{
uint32_t bufferBytesLeft;
uint32_t bytesToCopy;
int needBurn = 0;

if (sc->bufferLength) {
bufferBytesLeft = 64L - sc->bufferLength;
Expand All @@ -411,16 +404,21 @@ void ecdsa_sha256_update(ecdsa_sha256_context_t *sc, const void *data, size_t le

if (sc->bufferLength == 64L) {
SHA256Guts(sc, sc->buffer.words);
needBurn = 1;
sc->bufferLength = 0L;
}
}

while (len > 63L) {
uint32_t words[64 / sizeof(uint32_t)];

sc->totalLength += 512L;

SHA256Guts(sc, data);
needBurn = 1;
if (IS_ALIGNED(data, sizeof(uint32_t))) {
SHA256Guts(sc, data);
} else {
memcpy(words, data, sizeof(words));
SHA256Guts(sc, words);
}
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data = ((uint8_t *) data) + 64L;
len -= 64L;
Expand All @@ -433,10 +431,6 @@ void ecdsa_sha256_update(ecdsa_sha256_context_t *sc, const void *data, size_t le

sc->bufferLength += len;
}

if (needBurn)
burnStack(sizeof(uint32_t[74]) + sizeof(uint32_t *[6]) +
sizeof(int));
}

void ecdsa_sha256_final(ecdsa_sha256_context_t *sc, uint8_t hash[ECDSA_SHA256_HASH_SIZE])
Expand Down