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/*
* Copyright 2019 Offensive Security
* Copyright 2019 Raphaël Hertzog <raphael@offensive-security.com>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This package is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/random.h>
#include <crypt.h>
void
usage(const char* name, int exitcode)
{
fprintf(stderr, "Usage: %s <command>\n", name);
fprintf(stderr, "Valid commands:\n");
fprintf(stderr, " --help: display this output\n");
fprintf(stderr, " --generate <salt>: read password from stdin and print hashed version\n");
fprintf(stderr, " --check <hash>: read password from stdin and check it against supplied hash\n");
fprintf(stderr, " Exits with error 0 when password matched, 1 otherwise.\n");
exit(exitcode);
}
void
read_password(char *buffer, int bufsize)
{
int size = -1, total = 0, i = 0;
while ((size != 0) && (total < bufsize - 1)) {
size = read(0, buffer+total, bufsize - total);
if (size != -1) {
total += size;
}
}
buffer[total+1] = '\0';
for(i = 0; i < total; i++) {
if ((buffer[i] == '\n') || (buffer[i] == '\r')) {
buffer[i] = '\0';
break;
}
}
if (strlen(buffer) == 0) {
fprintf(stderr, "ERROR: no password supplied");
exit(1);
}
}
char*
gen_salt()
{
static const char alphanum[] = "123456789abcdefghijklmnopqrstuvwxyz"
"ABCDEFGHIJKLMNOPQRSTUVWXYZ";
static char salt[16];
int i, index;
unsigned int seed;
ssize_t ret;
ret = getrandom(&seed, sizeof(seed), 0);
if (ret != sizeof(seed)) {
fprintf(stderr, "ERROR: failed to get random data\n");
exit(2);
}
srandom(seed);
salt[0] = '$';
salt[1] = '6';
salt[2] = '$';
for (i = 3; i < 11; i++) {
index = random() % (sizeof(alphanum) - 1);
salt[i] = alphanum[index];
}
salt[11] = '$';
salt[12] = '\0';
return salt;
}
char*
extract_salt(char* hash)
{
static char salt[24];
if (hash[0] != '$') {
/* Traditional crypt hash with 2 characters */
salt[0] = hash[0];
salt[1] = hash[1];
salt[2] = '\0';
} else {
/* Hash delimited by $ characters */
char *p, *end;
int i;
p = hash;
end = strrchr(hash, '$');
for(i = 0; p <= end && i < sizeof(salt) - 1; i++) {
salt[i] = *p;
p++;
}
salt[i] = '\0';
}
return salt;
}
int
main (int argc, char* argv[])
{
static char buffer[256];
char *crypted, *salt;
if (argc == 1) {
usage(argv[0], 1);
}
if (strcmp(argv[1], "--help") == 0) {
usage(argv[0], 0);
} else if (strcmp(argv[1], "--generate") == 0) {
read_password(buffer, sizeof(buffer));
salt = (argc > 2 && strlen(argv[2])) ? argv[2] : gen_salt();
crypted = crypt(buffer, salt);
if (crypted == NULL || (
strlen(crypted) < 13 &&
strncmp(crypted, "*", 1) == 0 &&
strcmp(crypted, salt) != 0
)) {
fprintf(stderr, "ERROR: crypt() failed to return anything with salt '%s'", salt);
exit(1);
}
printf("%s\n", crypted);
} else if (strcmp(argv[1], "--check") == 0) {
read_password(buffer, sizeof(buffer));
if (argc < 3) {
fprintf(stderr, "ERROR: missing <hash> argument after --check");
exit(1);
}
salt = extract_salt(argv[2]);
crypted = crypt(buffer, salt);
if (crypted == NULL)
exit(1);
if (strcmp(crypted, argv[2]) == 0)
exit(0);
else
exit(1);
} else {
usage(argv[0], 1);
}
return 0;
}
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