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Make AES-CBC more efficient

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Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
This commit is contained in:
Dave Rodgman 2023-05-22 19:41:58 +01:00
parent 6f40f8bf01
commit 797c4ff365
1 changed files with 22 additions and 13 deletions
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21
library/aes.c
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@ -1068,36 +1068,45 @@ int mbedtls_aes_crypt_cbc(mbedtls_aes_context *ctx,
} }
#endif #endif
const unsigned char *ivp = iv;
if (mode == MBEDTLS_AES_DECRYPT) { if (mode == MBEDTLS_AES_DECRYPT) {
if (length >= 16) {
unsigned char temp2[16];
memcpy(temp, input + length - 16, 16);
while (length > 0) { while (length > 0) {
memcpy(temp, input, 16); ret = mbedtls_aes_crypt_ecb(ctx, mode, input, temp2);
ret = mbedtls_aes_crypt_ecb(ctx, mode, input, output);
if (ret != 0) { if (ret != 0) {
goto exit; goto exit;
} }
mbedtls_xor(output, output, iv, 16); mbedtls_xor(output, temp2, ivp, 16);
memcpy(iv, temp, 16); ivp = input;
input += 16; input += 16;
output += 16; output += 16;
length -= 16; length -= 16;
} }
memcpy(iv, temp, 16);
}
} else { } else {
while (length > 0) { while (length > 0) {
mbedtls_xor(output, input, iv, 16); mbedtls_xor(output, input, ivp, 16);
ret = mbedtls_aes_crypt_ecb(ctx, mode, output, output); ret = mbedtls_aes_crypt_ecb(ctx, mode, output, output);
if (ret != 0) { if (ret != 0) {
goto exit; goto exit;
} }
memcpy(iv, output, 16); ivp = output;
input += 16; input += 16;
output += 16; output += 16;
length -= 16; length -= 16;
} }
memcpy(iv, ivp, 16);
} }
ret = 0; ret = 0;