toxcore/other/fun/sign.c

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/* Binary signer/checker using ed25519
*
* Compile with:
* gcc -o sign sign.c -lsodium
*
* Generate a keypair:
* ./sign g
*
* Sign a file:
* ./sign s PRIVATEKEY file.bin signedfile.bin
*
* Check a file:
*
* ./sign c PUBKEY signedfile.bin
*
* NOTE: The signature is appended to the end of the file.
*/
#include <sodium.h>
#include <string.h>
unsigned char *hex_string_to_bin(char hex_string[])
{
size_t len = strlen(hex_string);
unsigned char *val = malloc(len);
char *pos = hex_string;
int i;
for (i = 0; i < len; ++i, pos += 2)
sscanf(pos, "%2hhx", &val[i]);
return val;
}
int load_file(char *filename, char **result)
{
int size = 0;
FILE *f = fopen(filename, "rb");
if (f == NULL) {
*result = NULL;
return -1; // -1 means file opening fail
}
fseek(f, 0, SEEK_END);
size = ftell(f);
fseek(f, 0, SEEK_SET);
*result = (char *)malloc(size + 1);
if (size != fread(*result, sizeof(char), size, f)) {
free(*result);
return -2; // -2 means file reading fail
}
fclose(f);
(*result)[size] = 0;
return size;
}
int main(int argc, char *argv[])
{
unsigned char pk[crypto_sign_ed25519_PUBLICKEYBYTES];
unsigned char sk[crypto_sign_ed25519_SECRETKEYBYTES];
if (argc == 2 && argv[1][0] == 'g') {
crypto_sign_ed25519_keypair(pk, sk);
printf("Public key:\n");
int i;
for (i = 0; i < crypto_sign_ed25519_PUBLICKEYBYTES; i++) {
printf("%02hhX", pk[i]);
}
printf("\nSecret key:\n");
for (i = 0; i < crypto_sign_ed25519_SECRETKEYBYTES; i++) {
printf("%02hhX", sk[i]);
}
printf("\n");
}
if (argc == 5 && argv[1][0] == 's') {
unsigned char *secret_key = hex_string_to_bin(argv[2]);
char *data;
int size = load_file(argv[3], &data);
if (size < 0)
goto fail;
unsigned long long smlen;
char *sm = malloc(size + crypto_sign_ed25519_BYTES * 2);
crypto_sign_ed25519(sm, &smlen, data, size, secret_key);
if (smlen - size != crypto_sign_ed25519_BYTES)
goto fail;
FILE *f = fopen(argv[4], "wb");
if (f == NULL)
goto fail;
memcpy(sm + smlen, sm, crypto_sign_ed25519_BYTES); // Move signature from beginning to end of file.
if (fwrite(sm + (smlen - size), 1, smlen, f) != smlen)
goto fail;
fclose(f);
printf("Signed successfully.\n");
}
if (argc == 4 && argv[1][0] == 'c') {
unsigned char *public_key = hex_string_to_bin(argv[2]);
char *data;
int size = load_file(argv[3], &data);
if (size < 0)
goto fail;
char *signe = malloc(size + crypto_sign_ed25519_BYTES);
memcpy(signe, data + size - crypto_sign_ed25519_BYTES,
crypto_sign_ed25519_BYTES); // Move signature from end to beginning of file.
memcpy(signe + crypto_sign_ed25519_BYTES, data, size - crypto_sign_ed25519_BYTES);
unsigned long long smlen;
char *m = malloc(size);
unsigned long long mlen;
if (crypto_sign_ed25519_open(m, &mlen, signe, size, public_key) == -1) {
printf("Failed checking sig.\n");
goto fail;
}
printf("Checked successfully.\n");
}
return 0;
fail:
printf("FAIL\n");
return 1;
}