poly1305-aes authentication

poly1305-aes.c

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <stdarg.h>
#include <unistd.h>

#include <openssl/evp.h>
#include <openssl/err.h>
#include <openssl/params.h>

int main()
{
    EVP_MAC *mac = EVP_MAC_fetch(NULL, "poly1305", NULL);
    const unsigned char key[] = {0x85, 0xd6, 0xbe, 0x78, 0x57, 0x55, 0x6d, 0x33,
                                 0x7f, 0x44, 0x52, 0xfe, 0x42, 0xd5, 0x06, 0xa8,
                                 0x01, 0x03, 0x80, 0x8a, 0xfb, 0x0d, 0xb2, 0xfd,
                                 0x4a, 0xbf, 0xf6, 0xaf, 0x41, 0x49, 0xf5, 0x1b};
    EVP_MAC_CTX *ctx = NULL;

    unsigned char *buf = "Cryptographic Forum Research Group";
    size_t final_l;

    size_t i;

    OSSL_PARAM params[1];
    size_t params_n = 0;

    params[params_n] = OSSL_PARAM_construct_end();

    ctx = EVP_MAC_CTX_new(mac);
    if (!ctx) {
        return -1;
    }

    if (!EVP_MAC_init(ctx, key, sizeof(key), params)) {
        goto err;
    }

    if (!EVP_MAC_update(ctx, buf, strlen(buf)))
        goto err;

    unsigned char out[32];
    if (!EVP_MAC_final(ctx, out, &final_l, sizeof(out)))
        goto err;

    printf("Result: ");
    for (i = 0; i < final_l; i++)
        printf("%02X:", out[i]);
    printf("\n");

    EVP_MAC_CTX_free(ctx);
    EVP_MAC_free(mac);
    return 0;

err:
    EVP_MAC_CTX_free(ctx);
    EVP_MAC_free(mac);
    fprintf(stderr, "Something went wrong\n");
    ERR_print_errors_fp(stderr);

    return -1;
}