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Iterate in 16-byte chunks

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Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
This commit is contained in:
Dave Rodgman 2024-01-12 18:29:01 +00:00
parent 67223bb501
commit c4f984f2a5
1 changed files with 19 additions and 13 deletions
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32
library/aes.c
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@ -1441,36 +1441,42 @@ int mbedtls_aes_crypt_ctr(mbedtls_aes_context *ctx,
const unsigned char *input,
unsigned char *output)
{
int c, i;
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t n;
n = *nc_off;
size_t offset = *nc_off;
if (n > 0x0F) {
if (offset > 0x0F) {
return MBEDTLS_ERR_AES_BAD_INPUT_DATA;
}
while (length--) {
if (n == 0) {
for (size_t i = 0; i < length;) {
size_t n = 16;
if (offset == 0) {
ret = mbedtls_aes_crypt_ecb(ctx, MBEDTLS_AES_ENCRYPT, nonce_counter, stream_block);
if (ret != 0) {
goto exit;
}
for (i = 16; i > 0; i--) {
if (++nonce_counter[i - 1] != 0) {
for (int j = 16; j > 0; j--) {
if (++nonce_counter[j - 1] != 0) {
break;
}
}
} else {
n -= offset;
}
c = *input++;
*output++ = (unsigned char) (c ^ stream_block[n]);
n = (n + 1) & 0x0F;
if (n > (length - i)) {
n = (length - i);
}
mbedtls_xor(&output[i], &input[i], &stream_block[offset], n);
// offset might be non-zero for the last block, but in that case, we don't use it again
offset = 0;
i += n;
}
*nc_off = n;
// capture offset for future resumption
*nc_off = (*nc_off + length) % 16;
ret = 0;
exit: