xref: /src/lib/libskey/skeylogin.c

/*	$NetBSD: skeylogin.c,v 1.13 2000/04/13 13:25:56 is Exp $	*/

/* S/KEY v1.1b (skeylogin.c)
 *
 * Authors:
 *          Neil M. Haller <nmh (at) thumper.bellcore.com>
 *          Philip R. Karn <karn (at) chicago.qualcomm.com>
 *          John S. Walden <jsw (at) thumper.bellcore.com>
 *          Scott Chasin <chasin (at) crimelab.com>
 *
 * S/KEY verification check, lookups, and authentication.
 */

#include <sys/param.h>
#ifdef	QUOTA
#include <sys/quota.h>
#endif
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/timeb.h>
#include <sys/resource.h>


#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <time.h>
#include <errno.h>

#include "skey.h"

#define	_PATH_KEYFILE	"/etc/skeykeys"

/* Issue a skey challenge for user 'name'. If successful,
 * fill in the caller's skey structure and return 0. If unsuccessful
 * (e.g., if name is unknown) return -1.
 *
 * The file read/write pointer is left at the start of the
 * record.
 *
 * XXX this function should be changed to have a length param for the
 * prompt!
 */
int
getskeyprompt(mp,name,prompt)
	struct skey *mp;
	char *name;
	char *prompt;
{
	int rval;

	sevenbit(name);
	rval = skeylookup(mp,name);
#if 0
	strcpy(prompt, "s/key 55 latour1\n");
#endif
	switch (rval) {
	case -1:	/* File error */
		return -1;
	case 0:		/* Lookup succeeded, return challenge */
		sprintf(prompt,"s/key %d %s\n",mp->n - 1,mp->seed);
		return 0;
	case 1:		/* User not found */
		fclose(mp->keyfile);
		return -1;
	}
	return -1;	/* Can't happen */
}

/* Return  a skey challenge string for user 'name'. If successful,
 * fill in the caller's skey structure and return 0. If unsuccessful
 * (e.g., if name is unknown) return -1.
 *
 * The file read/write pointer is left at the start of the
 * record.
 */
int
skeychallenge(mp,name, ss, sslen)
	struct skey *mp;
	const char *name;
	char *ss;
	int sslen;
{
	int rval;

	rval = skeylookup(mp,name);
	switch(rval){
	case -1:	/* File error */
		return -1;
	case 0:		/* Lookup succeeded, issue challenge */
                (void)snprintf(ss, (size_t)sslen, "s/key %d %s", mp->n - 1,
		    mp->seed);
		return 0;
	case 1:		/* User not found */
		fclose(mp->keyfile);
		return -1;
	}
	return -1;	/* Can't happen */
}

/* Find an entry in the One-time Password database.
 * Return codes:
 * -1: error in opening database
 *  0: entry found, file R/W pointer positioned at beginning of record
 *  1: entry not found, file R/W pointer positioned at EOF
 */
int
skeylookup(mp,name)
	struct skey *mp;
	const char *name;
{
	int found;
	size_t len;
	long recstart = 0;
	char *cp;
	struct stat statbuf;

	/* See if the _PATH_KEYFILE exists, and create it if not */

	if (stat(_PATH_KEYFILE,&statbuf) == -1 && errno == ENOENT) {
		mp->keyfile = fopen(_PATH_KEYFILE,"w+");
		if (mp->keyfile)
			chmod(_PATH_KEYFILE, 0644);
	} else {
		/* Otherwise open normally for update */
		mp->keyfile = fopen(_PATH_KEYFILE,"r+");
	}
	if (mp->keyfile == NULL)
		return -1;

	/* Look up user name in database */
	len = strlen(name);
	if (len > 8)
		len = 8;		/*  Added 8/2/91  -  nmh */
	found = 0;
	while (!feof(mp->keyfile)) {
		recstart = ftell(mp->keyfile);
		mp->recstart = recstart;
		if (fgets(mp->buf,sizeof(mp->buf),mp->keyfile) != mp->buf) {
			break;
		}
		rip(mp->buf);
		if (mp->buf[0] == '#')
			continue;	/* Comment */
		if ((mp->logname = strtok(mp->buf," \t")) == NULL)
			continue;
		if ((cp = strtok(NULL," \t")) == NULL)
			continue;
		mp->n = atoi(cp);
		if ((mp->seed = strtok(NULL," \t")) == NULL)
			continue;
		if ((mp->val = strtok(NULL," \t")) == NULL)
			continue;
		if (strlen(mp->logname) == len
		 && strncmp(mp->logname,name,len) == 0){
			found = 1;
			break;
		}
	}
	if (found) {
		fseek(mp->keyfile,recstart,0);
		return 0;
	} else
		return 1;
}
/* Verify response to a s/key challenge.
 *
 * Return codes:
 * -1: Error of some sort; database unchanged
 *  0:  Verify successful, database updated
 *  1:  Verify failed, database unchanged
 *
 * The database file is always closed by this call.
 */
int
skeyverify(mp,response)
	struct skey *mp;
	char *response;
{
	char key[8];
	char fkey[8];
	char filekey[8];
	time_t now;
	int  prevprio;
	struct tm *tm;
	char tbuf[27];

	time(&now);
	tm = localtime(&now);
	strftime(tbuf, sizeof(tbuf), " %b %d,%Y %T", tm);

	if (response == NULL) {
		fclose(mp->keyfile);
		return -1;
	}
	rip(response);

	/* Convert response to binary */
	if (etob(key, response) != 1 && atob8(key, response) != 0) {
		/* Neither english words or ascii hex */
		fclose(mp->keyfile);
		return -1;
	}

	/* Compute fkey = f(key) */
	memcpy(fkey,key,sizeof(key));
        fflush (stdout);

	f(fkey);
	/*
	 * in order to make the window of update as short as possible
	 * we must do the comparison here and if OK write it back
	 * other wise the same password can be used twice to get in
	 * to the system
	 */

	/* Save the priority for later use. */
	errno = 0;
	prevprio = getpriority(PRIO_PROCESS, 0);
	if (errno) {
		/* Don't report the error; just don't use it later. */
		prevprio = PRIO_MAX + 1;
	} else {
		setpriority(PRIO_PROCESS, 0, -4);
	}

	/* reread the file record NOW*/

	fseek(mp->keyfile,mp->recstart,0);
	if (fgets(mp->buf,sizeof(mp->buf),mp->keyfile) != mp->buf){
		if (prevprio != PRIO_MAX + 1) {
			setpriority(PRIO_PROCESS, 0, prevprio);
		}
		fclose(mp->keyfile);
		return -1;
	}
	rip(mp->buf);
	mp->logname = strtok(mp->buf," \t");
	(void) strtok(NULL," \t");	/* ignore counter */
	mp->seed = strtok(NULL," \t");
	mp->val = strtok(NULL," \t");
	/* And convert file value to hex for comparison */
	atob8(filekey,mp->val);

	/* Do actual comparison */
        fflush (stdout);

	if (memcmp(filekey,fkey,8) != 0){
		/* Wrong response */
		if (prevprio != PRIO_MAX + 1) {
			setpriority(PRIO_PROCESS, 0, prevprio);
		}
		fclose(mp->keyfile);
		return 1;
	}

	/*
	 * Update key in database by overwriting entire record. Note
	 * that we must write exactly the same number of bytes as in
	 * the original record (note fixed width field for N)
	 */
	btoa8(mp->val,key);
	mp->n--;
	fseek(mp->keyfile,mp->recstart,0);
	fprintf(mp->keyfile, "%s %04d %-16s %s %-21s\n",
		mp->logname,mp->n,mp->seed, mp->val, tbuf);

	fclose(mp->keyfile);

	if (prevprio != PRIO_MAX + 1) {
		setpriority(PRIO_PROCESS, 0, prevprio);
	}
	return 0;
}


/*
 * skey_haskey ()
 *
 * Returns: 1 user doesnt exist, -1 fle error, 0 user exists.
 *
 */

int
skey_haskey (username)
	const char *username;
{
	struct skey skey;

	return (skeylookup (&skey, username));
}

/*
 * skey_keyinfo ()
 *
 * Returns the current sequence number and
 * seed for the passed user.
 *
 */
char *
skey_keyinfo (username)
	const char *username;
{
	int i;
	static char str [50];
	struct skey skey;

	i = skeychallenge (&skey, username, str, sizeof str);
	if (i == -1)
		return 0;

	return str;
}

/*
 * skey_passcheck ()
 *
 * Check to see if answer is the correct one to the current
 * challenge.
 *
 * Returns: 0 success, -1 failure
 *
 */

int
skey_passcheck (username, passwd)
	const char *username;
	char *passwd;
{
	int i;
	struct skey skey;

	i = skeylookup (&skey, username);
	if (i == -1 || i == 1)
		return -1;

	if (skeyverify (&skey, passwd) == 0)
		return skey.n;

	return -1;
}

/*
 * skey_authenticate ()
 *
 * Used when calling program will allow input of the user's
 * response to the challenge.
 *
 * Returns: 0 success, -1 failure
 *
 */

int
skey_authenticate (username)
	const char *username;
{
	int i;
	char pbuf[256], skeyprompt[50];
	struct skey skey;

	/* Attempt a S/Key challenge */
	i = skeychallenge (&skey, username, skeyprompt, sizeof skeyprompt);

	if (i == -2)
		return 0;

	printf("[%s]\n", skeyprompt);
	fflush(stdout);

	printf("Response: ");
	readskey(pbuf, sizeof (pbuf));
	rip(pbuf);

	/* Is it a valid response? */
	if (i == 0 && skeyverify (&skey, pbuf) == 0) {
		if (skey.n < 5) {
			printf ("\nWarning! Key initialization needed soon.  ");
			printf ("(%d logins left)\n", skey.n);
		}
		return 0;
	}
	return -1;
}