I have written a simple example which uses openssl SHA-3 implementation to calculate the digest of all the data read from stdin.
With a command line parameter to specify SHA-3 digest length.
Tested on Linux Parrot (distro based on Debian), libssl-dev 1.1.1c-1.
Link to the repository.
Or here is the source code:
#include <openssl/evp.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
/*
* building on Debian requires libssl-dev package (sudo apt install libssl-dev)
*/
#define BUF_SIZE 1024
#define HANDLE_ERROR(msg) { fprintf(stderr, "%s\n", msg); exit(EXIT_FAILURE); }
#define HANDLE_ERROR2(msg, mdctx) { fprintf(stderr, "%s\n", msg); EVP_MD_CTX_destroy(mdctx); exit(EXIT_FAILURE); }
int main(int argc, char * const argv[]) {
int opt;
char * endptr;
char buffer[BUF_SIZE];
int bytes_read;
EVP_MD_CTX * mdctx;
int val;
unsigned char * digest;
unsigned int digest_len;
EVP_MD * algo = NULL;
while ((opt = getopt(argc, argv, "t:")) != -1) {
switch (opt) {
case 't':
errno = 0;
val = strtol(optarg, &endptr, 10);
if ((errno == ERANGE && (val == LONG_MAX || val == LONG_MIN))
|| (errno != 0 && val == 0)) {
perror("Wrong value for t parameter");
exit(EXIT_FAILURE);
}
if (endptr == optarg) {
fprintf(stderr, "No value was found for t parameter\n");
exit(EXIT_FAILURE);
}
switch (val) {
case 224:
algo = EVP_sha3_224();
break;
case 256:
algo = EVP_sha3_256();
break;
case 384:
algo = EVP_sha3_384();
break;
case 512:
algo = EVP_sha3_512();
break;
default:
fprintf(stderr,"Wrong value for t parameter (valid values: 224, 256, 384, 512)");
exit(EXIT_FAILURE);
}
break;
default: /* '?' */
fprintf(stderr, "Usage: %s [-t sha3_size]\n"
"Example program which calculates SHA-3 hash of data read from stdin.\n"
"Uses openssl implementation of SHA-3 algorithm.\n"
"sha3_size can be: 224, 256, 384, 512. Default is 256.\n",
argv[0]);
exit(EXIT_FAILURE);
}
}
if (algo == NULL) {
algo = EVP_sha3_256();
}
if ((mdctx = EVP_MD_CTX_create()) == NULL) {
HANDLE_ERROR("EVP_MD_CTX_create() error")
}
// initialize digest engine
if (EVP_DigestInit_ex(mdctx, algo, NULL) != 1) { // returns 1 if successful
HANDLE_ERROR2("EVP_DigestInit_ex() error", mdctx)
}
while ((bytes_read = read(STDIN_FILENO, buffer, BUF_SIZE)) > 0) { // read returns 0 on EOF, -1 on error
// provide data to digest engine
if (EVP_DigestUpdate(mdctx, buffer, bytes_read) != 1) { // returns 1 if successful
HANDLE_ERROR2("EVP_DigestUpdate() error", mdctx)
}
}
if (bytes_read == -1) {
perror("read error");
exit(1);
}
digest_len = EVP_MD_size(algo);
if ((digest = (unsigned char *)OPENSSL_malloc(digest_len)) == NULL) {
HANDLE_ERROR2("OPENSSL_malloc() error", mdctx)
}
// produce digest
if (EVP_DigestFinal_ex(mdctx, digest, &digest_len) != 1) { // returns 1 if successful
OPENSSL_free(digest);
HANDLE_ERROR2("EVP_DigestFinal_ex() error", mdctx)
}
for (int i = 0; i < digest_len; i++) {
printf("%02x", digest[i]);
}
OPENSSL_free(digest);
EVP_MD_CTX_destroy(mdctx);
return 0;
}
