/*      $OpenBSD: skey.c,v 1.36 2024/08/03 22:00:31 millert Exp $       */
/*
 * OpenBSD S/Key (skey.c)
 *
 * Authors:
 *          Neil M. Haller <nmh@thumper.bellcore.com>
 *          Philip R. Karn <karn@chicago.qualcomm.com>
 *          John S. Walden <jsw@thumper.bellcore.com>
 *          Scott Chasin <chasin@crimelab.com>
 *          Todd C. Miller <millert@openbsd.org>
 *
 *
 * Stand-alone program for computing responses to S/Key challenges.
 * Takes the iteration count and seed as command line args, prompts
 * for the user's key, and produces both word and hex format responses.
 *
 * Usage example:
 *      >skey 88 ka9q2
 *      Enter password:
 *      OMEN US HORN OMIT BACK AHOY
 *      >
 *
 */

#include <err.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <readpassphrase.h>
#include <skey.h>

void usage();

extern char *__progname;

int
main(int argc, char *argv[])
{
        int     n, i, cnt = 1, pass = 0, hexmode = 0;
        char    passwd[SKEY_MAX_PW_LEN+1], key[SKEY_BINKEY_SIZE];
        char    buf[33], *seed, *slash, *algo;
        const char *errstr;

        if (pledge("stdio tty", NULL) == -1)
                err(1, "pledge");

        /* If we were called as otp-METHOD, set algorithm based on that */
        if (strncmp(__progname, "otp-", 4) == 0) {
                algo = __progname + 4;
                if (skey_set_algorithm(algo) == NULL)
                        errx(1, "Unknown hash algorithm %s", algo);
        }

        for (i = 1; i < argc && argv[i][0] == '-' && strcmp(argv[i], "--");) {
                if (argv[i][2] == '\0') {
                        /* Single character switch */
                        switch (argv[i][1]) {
                        case 'n':
                                if (++i == argc)
                                        usage();
                                cnt = strtonum(argv[i], 1, SKEY_MAX_SEQ + 1,
                                    &errstr);
                                if (errstr)
                                        usage();
                                break;
                        case 'p':
                                if (++i == argc)
                                        usage();
                                if (strlcpy(passwd, argv[i], sizeof(passwd)) >=
                                    sizeof(passwd))
                                        errx(1, "Password too long");
                                pass = 1;
                                break;
                        case 'x':
                                hexmode = 1;
                                break;
                        default:
                                usage();
                        }
                } else {
                        /* Multi character switches are hash types */
                        if (skey_set_algorithm(&argv[i][1]) == NULL) {
                                warnx("Unknown hash algorithm %s", &argv[i][1]);
                                usage();
                        }
                }
                i++;
        }

        if (argc > i + 2)
                usage();

        /* Could be in the form <number>/<seed> */
        if (argc <= i + 1) {
                /* look for / in it */
                if (argc <= i)
                        usage();
                slash = strchr(argv[i], '/');
                if (slash == NULL)
                        usage();
                *slash++ = '\0';
                seed = slash;

                n = strtonum(argv[i], 0, SKEY_MAX_SEQ, &errstr);
                if (errstr) {
                        warnx("%s: %s", argv[i], errstr);
                        usage();
                }
        } else {
                n = strtonum(argv[i], 0, SKEY_MAX_SEQ, &errstr);
                if (errstr) {
                        warnx("%s: %s", argv[i], errstr);
                        usage();
                }
                seed = argv[++i];
        }

        /* Get user's secret passphrase */
        if (!pass && (readpassphrase("Enter secret passphrase: ", passwd,
            sizeof(passwd), 0) == NULL || passwd[0] == '\0'))
                exit(1);

        /* Crunch seed and passphrase into starting key */
        if (keycrunch(key, seed, passwd) != 0) {
                explicit_bzero(passwd, sizeof(passwd));
                errx(1, "key crunch failed");
        }

        explicit_bzero(passwd, sizeof(passwd));

        if (cnt == 1) {
                while (n-- != 0)
                        f(key);
                (void)puts(hexmode ? put8(buf, key) : btoe(buf, key));
        } else {
                for (i = 0; i <= n - cnt; i++)
                        f(key);
                for (; i <= n; i++) {
                        if (hexmode)
                                (void)printf("%d: %s\n", i, put8(buf, key));
                        else
                                (void)printf("%d: %-29s\n", i, btoe(buf, key));
                        f(key);
                }
        }
        exit(0);
}

void
usage(void)
{
        fprintf(stderr,
            "usage: %s [-x] [-md5 | -rmd160 | -sha1] [-n count]\n\t"
            "[-p passphrase] <sequence#>[/] key\n", __progname);
        exit(1);
}