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/* $OpenBSD: login_skey.c,v 1.11 2002/09/06 18:45:07 deraadt Exp $ */
/*-
* Copyright (c) 1995 Berkeley Software Design, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by Berkeley Software Design,
* Inc.
* 4. The name of Berkeley Software Design, Inc. may not be used to endorse
* or promote products derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN, INC. ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN, INC. BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* BSDI $From: login_skey.c,v 1.3 1996/09/04 05:24:56 prb Exp $
*/
#include <sys/types.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <paths.h>
#include <pwd.h>
#include <readpassphrase.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#include <login_cap.h>
#include <bsd_auth.h>
#include <sha1.h>
#include <skey.h>
void quit(int);
void suspend(int);
volatile sig_atomic_t resumed;
struct skey skey;
int
main(int argc, char *argv[])
{
FILE *back = NULL;
char *class = 0;
char *username = 0;
char skeyprompt[SKEY_MAX_CHALLENGE+17];
char passbuf[SKEY_MAX_PW_LEN+1];
int c, haskey;
int mode = 0;
skeyprompt[0] = '\0';
(void)signal(SIGINT, quit);
(void)signal(SIGQUIT, quit);
(void)signal(SIGALRM, quit);
(void)signal(SIGTSTP, suspend);
(void)setpriority(PRIO_PROCESS, 0, 0);
openlog(NULL, LOG_ODELAY, LOG_AUTH);
while ((c = getopt(argc, argv, "ds:v:")) != -1)
switch (c) {
case 'd': /* to remain undocumented */
back = stdout;
break;
case 'v':
break;
case 's': /* service */
if (strcmp(optarg, "login") == 0)
mode = 0;
else if (strcmp(optarg, "challenge") == 0)
mode = 1;
else if (strcmp(optarg, "response") == 0)
mode = 2;
else {
syslog(LOG_ERR, "%s: invalid service", optarg);
exit(1);
}
break;
default:
syslog(LOG_ERR, "usage error");
exit(1);
}
switch (argc - optind) {
case 2:
class = argv[optind + 1];
case 1:
username = argv[optind];
break;
default:
syslog(LOG_ERR, "usage error");
exit(1);
}
if (back == NULL && (back = fdopen(3, "r+")) == NULL) {
syslog(LOG_ERR, "reopening back channel: %m");
exit(1);
}
if (mode == 2) {
mode = 0;
c = -1;
/* XXX - redo these loops! */
while (++c < sizeof(skeyprompt) &&
read(3, &skeyprompt[c], 1) == 1) {
if (skeyprompt[c] == '\0') {
mode++;
break;
}
}
if (mode == 1) {
c = -1;
while (++c < sizeof(passbuf) &&
read(3, &passbuf[c], 1) == 1) {
if (passbuf[c] == '\0') {
mode++;
break;
}
}
}
if (mode < 2) {
syslog(LOG_ERR, "protocol error on back channel");
exit(1);
}
/*
* Sigh. S/Key really is a stateful protocol.
* We must assume that a user will only try to
* authenticate one at a time and that this call to
* skeychallenge will produce the same results as
* the call to skeychallenge when mode was 1.
*
* Furthermore, RFC2289 requires that an entry be
* locked against a partial guess race which is
* simply not possible if the calling program queries
* the user for the passphrase itself. Oh well.
*/
haskey = (skeychallenge(&skey, username, skeyprompt) == 0);
} else {
/*
* Attempt an S/Key challenge.
* The OpenBSD skeychallenge() will always fill in a
* challenge, even if it has to cons one up.
*/
haskey = (skeychallenge(&skey, username, skeyprompt) == 0);
strlcat(skeyprompt, "\nS/Key Password: ", sizeof skeyprompt);
if (mode == 1) {
fprintf(back, BI_VALUE " challenge %s\n",
auth_mkvalue(skeyprompt));
fprintf(back, BI_CHALLENGE "\n");
exit(0);
}
/* Time out getting passphrase after 2 minutes to avoid a DoS */
if (haskey)
alarm(120);
resumed = 0;
readpassphrase(skeyprompt, passbuf, sizeof(passbuf), 0);
if (passbuf[0] == '\0')
readpassphrase("S/Key Password [echo on]: ",
passbuf, sizeof(passbuf), RPP_ECHO_ON);
alarm(0);
if (resumed) {
/*
* We were suspended by the user. Our lock is
* no longer valid so we must regain it so
* an attacker cannot do a partial guess of
* an S/Key response already in progress.
*/
haskey = (skeylookup(&skey, username) == 0);
}
}
/*
* Ignore keyboard interupt/suspend during database update.
*/
signal(SIGINT, SIG_IGN);
signal(SIGQUIT, SIG_IGN);
signal(SIGTSTP, SIG_IGN);
if (haskey && skeyverify(&skey, passbuf) == 0) {
if (mode == 0) {
if (skey.n <= 1)
printf("Warning! You MUST change your "
"S/Key password now!\n");
else if (skey.n < 5)
printf("Warning! Change S/Key password soon\n");
}
fprintf(back, BI_AUTH "\n");
fprintf(back, BI_SECURE "\n");
exit(0);
}
fprintf(back, BI_REJECT "\n");
exit(1);
}
void
quit(int signo)
{
_exit(1);
}
void
suspend(int signo)
{
sigset_t nset;
int save_errno = errno;
/*
* Unlock the skey record so we don't sleep holding the lock.
* Unblock SIGTSTP, set it to the default action and then
* resend it so we are suspended properly.
* When we resume, reblock SIGTSTP, reset the signal handler,
* set a flag and restore errno.
*/
alarm(0);
skey_unlock(&skey);
(void)signal(signo, SIG_DFL);
(void)sigemptyset(&nset);
(void)sigaddset(&nset, signo);
(void)sigprocmask(SIG_UNBLOCK, &nset, NULL);
(void)kill(getpid(), signo);
(void)sigprocmask(SIG_BLOCK, &nset, NULL);
(void)signal(signo, suspend);
resumed = 1;
errno = save_errno;
}
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