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It is pronounced S/Key

/*	$OpenBSD: skeyinit.c,v 1.27 2001/01/26 16:27:04 millert Exp $	*/

/* S/KEY v1.1b (skeyinit.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>
 *
 * Modifications:
 *          Todd C. Miller <Todd.Miller@courtesan.com>
 *
 * S/KEY initialization and seed update
 */

#include <sys/param.h>
#include <sys/file.h>
#include <sys/time.h>
#include <sys/resource.h>

#include <err.h>
#include <errno.h>
#include <ctype.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <time.h>
#include <unistd.h>
#include <utmp.h>

#include <skey.h>

#ifndef SKEY_NAMELEN
#define SKEY_NAMELEN    4
#endif

void	usage __P((char *));

int
main(argc, argv)
	int     argc;
	char   *argv[];
{
	int     rval, nn, i, l, n=0, defaultsetup=1, zerokey=0, hexmode=0;
	time_t  now;
	char	hostname[MAXHOSTNAMELEN];
	char    passwd[SKEY_MAX_PW_LEN+2], passwd2[SKEY_MAX_PW_LEN+2];
	char	seed[SKEY_MAX_SEED_LEN+2], defaultseed[SKEY_MAX_SEED_LEN+1];
	char    tbuf[27], buf[80], key[SKEY_BINKEY_SIZE];
	char    lastc, me[UT_NAMESIZE+1], *salt, *p, *pw, *ht=NULL;
	struct skey skey;
	struct passwd *pp;
	struct tm *tm;

	if (geteuid() != 0)
		errx(1, "must be setuid root.");

	if (gethostname(hostname, sizeof(hostname)) < 0)
		err(1, "gethostname");
	for (i = 0, p = defaultseed; hostname[i] && i < SKEY_NAMELEN; i++) {
		if (isalpha(hostname[i])) {
			if (isupper(hostname[i]))
				hostname[i] = tolower(hostname[i]);
			*p++ = hostname[i];
		} else if (isdigit(hostname[i]))
			*p++ = hostname[i];
	}
	*p = '\0';
	(void)time(&now);
	(void)sprintf(tbuf, "%05ld", (long) (now % 100000));
	(void)strncat(defaultseed, tbuf, sizeof(defaultseed) - 5);

	if ((pp = getpwuid(getuid())) == NULL)
		err(1, "no user with uid %d", getuid());
	(void)strcpy(me, pp->pw_name);

	if ((pp = getpwnam(me)) == NULL)
		err(1, "Who are you?");
	salt = pp->pw_passwd;

	for (i = 1; i < argc && argv[i][0] == '-' && strcmp(argv[i], "--");) {
		if (argv[i][2] == '\0') {
			/* Single character switch */
			switch (argv[i][1]) {
			case 's':
				defaultsetup = 0;
				break;
			case 'x':
				hexmode = 1;
				break;
			case 'z':
				zerokey = 1;
				break;
			case 'n':
				if (argv[++i] == NULL || argv[i][0] == '\0')
					usage(argv[0]);
				if ((n = atoi(argv[i])) < 1 || n >= SKEY_MAX_SEQ)
					errx(1, "count must be > 0 and < %d",
					     SKEY_MAX_SEQ);
				break;
			default:
				usage(argv[0]);
			}
		} else {
			/* Multi character switches are hash types */
			if ((ht = skey_set_algorithm(&argv[i][1])) == NULL) {
				warnx("Unknown hash algorithm %s", &argv[i][1]);
				usage(argv[0]);
			}
		}
		i++;
	}

	/* check for optional user string */
	if (argc - i  > 1) {
		usage(argv[0]);
	} else if (argv[i]) {
		if ((pp = getpwnam(argv[i])) == NULL) {
			if (getuid() == 0) {
				static struct passwd _pp;

				_pp.pw_name = argv[i];
				pp = &_pp;
				warnx("Warning, user unknown: %s", argv[i]);
			} else {
				errx(1, "User unknown: %s", argv[i]);
			}
		} else if (strcmp(pp->pw_name, me) != 0) {
			if (getuid() != 0) {
				/* Only root can change other's passwds */
				errx(1, "Permission denied.");
			}
		}
	}

	if (getuid() != 0) {
		pw = getpass("Password (or `s/key'):");
		if (strcasecmp(pw, "s/key") == 0) {
			if (skey_haskey(me))
				exit(1);
			if (skey_authenticate(me))
				errx(1, "Password incorrect.");
		} else {
			p = crypt(pw, salt);
			if (strcmp(p, pp->pw_passwd))
				errx(1, "Password incorrect.");
		}
	}

	rval = skeylookup(&skey, pp->pw_name);
	switch (rval) {
		case -1:
			if (errno == ENOENT)
				errx(1, "S/Key disabled");
			else
				err(1, "cannot open database");
			break;
		case 0:
			/* comment out user if asked to */
			if (zerokey)
				exit(skeyzero(&skey, pp->pw_name));

			(void)printf("[Updating %s]\n", pp->pw_name);
			(void)printf("Old key: [%s] %s\n", skey_get_algorithm(),
				     skey.seed);

			/*
			 * Sanity check old seed.
			 */
			l = strlen(skey.seed);
			for (p = skey.seed; *p; p++) {
				if (isalpha(*p)) {
					if (isupper(*p))
						*p = tolower(*p);
				} else if (!isdigit(*p)) {
					memmove(p, p + 1, l - (p - skey.seed));
					l--;
				}
			}

			/*
			 * Let's be nice if they have an skey.seed that
			 * ends in 0-8 just add one
			 */
			if (l > 0) {
				lastc = skey.seed[l - 1];
				if (isdigit(lastc) && lastc != '9') {
					(void)strcpy(defaultseed, skey.seed);
					defaultseed[l - 1] = lastc + 1;
				}
				if (isdigit(lastc) && lastc == '9' && l < 16) {
					(void)strcpy(defaultseed, skey.seed);
					defaultseed[l - 1] = '0';
					defaultseed[l] = '0';
					defaultseed[l + 1] = '\0';
				}
			}
			break;
		case 1:
			if (zerokey)
				errx(1, "You have no entry to zero.");
			(void)printf("[Adding %s]\n", pp->pw_name);
			break;
	}
	if (n == 0)
		n = 99;

	/* Set hash type if asked to */
	if (ht) {
		/* Need to zero out old key when changing algorithm */
		if (strcmp(ht, skey_get_algorithm()) && skey_set_algorithm(ht))
			zerokey = 1;
	}

	if (!defaultsetup) {
		(void)printf("You need the 6 english words generated from the \"skey\" command.\n");
		for (i = 0; ; i++) {
			if (i >= 2)
				exit(1);

			(void)printf("Enter sequence count from 1 to %d: ",
				     SKEY_MAX_SEQ);
			(void)fgets(buf, sizeof(buf), stdin);
			n = atoi(buf);
			if (n > 0 && n < SKEY_MAX_SEQ)
				break;	/* Valid range */
			(void)printf("Error: Count must be > 0 and < %d\n",
				     SKEY_MAX_SEQ);
		}

		for (i = 0;; i++) {
			if (i >= 2)
				exit(1);

			(void)printf("Enter new key [default %s]: ",
				     defaultseed);
			(void)fgets(seed, sizeof(seed), stdin);
			rip(seed);
			if (seed[0] == '\0')
				(void)strcpy(seed, defaultseed);
			for (p = seed; *p; p++) {
				if (isalpha(*p)) {
					if (isupper(*p))
						*p = tolower(*p);
				} else if (!isdigit(*p)) {
					(void)puts("Error: seed may only contain alpha numeric characters");
					break;
				}
			}
			if (*p == '\0')
				break;  /* Valid seed */
		}
		if (strlen(seed) > SKEY_MAX_SEED_LEN) {
			(void)printf("Notice: Seed truncated to %d characters.\n",
				     SKEY_MAX_SEED_LEN);
			seed[SKEY_MAX_SEED_LEN] = '\0';
		}

		for (i = 0;; i++) {
			if (i >= 2)
				exit(1);

			(void)printf("otp-%s %d %s\nS/Key access password: ",
				     skey_get_algorithm(), n, seed);
			(void)fgets(buf, sizeof(buf), stdin);
			rip(buf);
			backspace(buf);

			if (buf[0] == '?') {
				(void)puts("Enter 6 English words from secure S/Key calculation.");
				continue;
			} else if (buf[0] == '\0')
				exit(1);
			if (etob(key, buf) == 1 || atob8(key, buf) == 0)
				break;	/* Valid format */
			(void)puts("Invalid format - try again with 6 English words.");
		}
	} else {
		/* Get user's secret password */
		fputs("Reminder - Only use this method if you are directly connected\n           or have an encrypted channel.  If you are using telnet\n           or rlogin, exit with no password and use skeyinit -s.\n", stderr);

		for (i = 0;; i++) {
			if (i > 2)
				exit(1);

			(void)fputs("Enter secret password: ", stderr);
			readpass(passwd, sizeof(passwd));
			if (passwd[0] == '\0')
				exit(1);

			if (strlen(passwd) < SKEY_MIN_PW_LEN) {
				(void)fprintf(stderr,
				    "Your password must be at least %d characters long.\n", SKEY_MIN_PW_LEN);
				continue;
			} else if (strcmp(passwd, pp->pw_name) == 0) {
				(void)fputs("Your password may not be the same as your user name.\n", stderr);
				continue;
			} else if (strspn(passwd, "abcdefghijklmnopqrstuvwxyz") == strlen(passwd)) {
				(void)fputs("Your password must contain more than just lower case letters.\nWhitespace, numbers, and puctuation are suggested.\n", stderr);
				continue;
			}

			(void)fputs("Again secret password: ", stderr);
			readpass(passwd2, sizeof(passwd));

			if (strcmp(passwd, passwd2) == 0)
				break;

			(void)fputs("Passwords do not match.\n", stderr);
		}

		/* Crunch seed and password into starting key */
		(void)strcpy(seed, defaultseed);
		if (keycrunch(key, seed, passwd) != 0)
			err(2, "key crunch failed");

		nn = n;
		while (nn-- != 0)
			f(key);
	}
	(void)time(&now);
	tm = localtime(&now);
	(void)strftime(tbuf, sizeof(tbuf), " %b %d,%Y %T", tm);

	if ((skey.val = (char *)malloc(16 + 1)) == NULL)
		err(1, "Can't allocate memory");

	/* Zero out old key if necesary (entry would change size) */
	if (zerokey) {
		(void)skeyzero(&skey, pp->pw_name);
		/* Re-open keys file and seek to the end */
		if (skeylookup(&skey, pp->pw_name) == -1)
			err(1, "cannot open database");
	}

	btoa8(skey.val, key);

	/*
	 * Obtain an exclusive lock on the key file so we don't
	 * clobber someone authenticating themselves at the same time.
	 */
	for (i = 0; i < 300; i++) {
		if ((rval = flock(fileno(skey.keyfile), LOCK_EX|LOCK_NB)) == 0
		    || errno != EWOULDBLOCK)
			break;
		usleep(100000);			/* Sleep for 0.1 seconds */
	}
	if (rval == -1)	{			/* Can't get exclusive lock */
		errno = EAGAIN;
		err(1, "cannot open database");
	}

	/* Don't save algorithm type for md4 (keep record length same) */
	if (strcmp(skey_get_algorithm(), "md4") == 0)
		(void)fprintf(skey.keyfile, "%s %04d %-16s %s %-21s\n",
		    pp->pw_name, n, seed, skey.val, tbuf);
	else
		(void)fprintf(skey.keyfile, "%s %s %04d %-16s %s %-21s\n",
		    pp->pw_name, skey_get_algorithm(), n, seed, skey.val, tbuf);

	(void)fclose(skey.keyfile);

	(void)printf("\nID %s skey is otp-%s %d %s\n", pp->pw_name,
		     skey_get_algorithm(), n, seed);
	(void)printf("Next login password: %s\n\n",
		     hexmode ? put8(buf, key) : btoe(buf, key));
	exit(0);
}

void
usage(s)
	char *s;
{
	(void)fprintf(stderr,
		"Usage: %s [-s] [-x] [-z] [-n count] [-md4|-md5|-sha1|-rmd160] [user]\n", s);
	exit(1);
}