How to calculate AES CMAC using OpenSSL CMAC_xxx functions?

Question

Is there a way to compute AES CMAC with OpenSSL / libcrypto ?

Preferably in such a way as to use AES-NI (or any other hardware acceleration).

See also OpenSSL OpenSSL CMAC Key Generation EVP_DigestSign *

Answer 1

As stated in my blog post , you can use CMAC_CTX_new , CMAC_Init , CMAC_Update and CMAC_Final from lib crypto to calculate AES-128-CBC CMAC. Here is an example:

 #include <stdio.h> #include <openssl/cmac.h> void printBytes(unsigned char *buf, size_t len) { for(int i=0; i<len; i++) { printf("%02x ", buf[i]); } printf("\n"); } int main(int argc, char *argv[]) { // https://tools.ietf.org/html/rfc4493 // K, M and T from // http://csrc.nist.gov/publications/nistpubs/800-38B/Updated_CMAC_Examples.pdf // D.1 AES-128 // K: 2b7e1516 28aed2a6 abf71588 09cf4f3c unsigned char key[] = { 0x2b,0x7e,0x15,0x16, 0x28,0xae,0xd2,0xa6, 0xab,0xf7,0x15,0x88, 0x09,0xcf,0x4f,0x3c}; // M: 6bc1bee2 2e409f96 e93d7e11 7393172a Mlen: 128 unsigned char message[] = { 0x6b,0xc1,0xbe,0xe2, 0x2e,0x40,0x9f,0x96, 0xe9,0x3d,0x7e,0x11, 0x73,0x93,0x17,0x2a }; unsigned char mact[16] = {0}; size_t mactlen; CMAC_CTX *ctx = CMAC_CTX_new(); CMAC_Init(ctx, key, 16, EVP_aes_128_cbc(), NULL); printf("message length = %lu bytes (%lu bits)\n",sizeof(message), sizeof(message)*8); CMAC_Update(ctx, message, sizeof(message)); CMAC_Final(ctx, mact, &mactlen); printBytes(mact, mactlen); /* expected result T = 070a16b4 6b4d4144 f79bdd9d d04a287c */ CMAC_CTX_free(ctx); return 0; }