OpenBSD-4.6/libexec/login_skey/login_skey.c
/* $OpenBSD: login_skey.c,v 1.23 2009/06/02 20:42:48 jmeltzer Exp $ */
/*
* Copyright (c) 2000, 2001, 2004 Todd C. Miller <Todd.Miller@courtesan.com>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/param.h>
#include <sys/socket.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 <skey.h>
#define MODE_LOGIN 0
#define MODE_CHALLENGE 1
#define MODE_RESPONSE 2
void quit(int);
void send_fd(int);
void suspend(int);
volatile sig_atomic_t resumed;
struct skey skey;
int
main(int argc, char *argv[])
{
FILE *back = NULL;
char *user = NULL, *cp, *ep;
char challenge[SKEY_MAX_CHALLENGE+17], response[SKEY_MAX_PW_LEN+1];
const char *errstr;
int ch, fd = -1, haskey = 0, mode = MODE_LOGIN;
(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 ((ch = getopt(argc, argv, "ds:v:")) != -1) {
switch (ch) {
case 'd':
back = stdout;
break;
case 's': /* service */
if (strcmp(optarg, "login") == 0)
mode = MODE_LOGIN;
else if (strcmp(optarg, "challenge") == 0)
mode = MODE_CHALLENGE;
else if (strcmp(optarg, "response") == 0)
mode = MODE_RESPONSE;
else {
syslog(LOG_ERR, "%s: invalid service", optarg);
exit(1);
}
break;
case 'v':
if (strncmp(optarg, "fd=", 3) == 0) {
fd = strtonum(optarg + 3, 0, INT_MAX, &errstr);
if (errstr != NULL) {
syslog(LOG_ERR, "fd is %s: %s",
errstr, optarg + 3);
fd = -1;
}
}
/* silently ignore unsupported variables */
break;
default:
syslog(LOG_ERR, "usage error");
exit(1);
}
}
argc -= optind;
argv += optind;
switch (argc) {
case 2: /* silently ignore class */
case 1:
user = *argv;
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);
}
/*
* Note: our skeychallenge2() will always fill in the challenge,
* even if it has to create a fake one.
*/
switch (mode) {
case MODE_LOGIN:
haskey = (skeychallenge2(fd, &skey, user, challenge) == 0);
strlcat(challenge, "\nS/Key Password:", sizeof(challenge));
/* time out getting passphrase after 2 minutes to avoid a DoS */
if (haskey)
alarm(120);
resumed = 0;
if (!readpassphrase(challenge, response, sizeof(response), 0))
exit(1);
if (response[0] == '\0')
readpassphrase("S/Key Password [echo on]: ",
response, sizeof(response), 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, user) == 0);
}
break;
case MODE_CHALLENGE:
haskey = (skeychallenge2(fd, &skey, user, challenge) == 0);
strlcat(challenge, "\nS/Key Password:", sizeof(challenge));
fprintf(back, BI_VALUE " challenge %s\n",
auth_mkvalue(challenge));
fprintf(back, BI_CHALLENGE "\n");
fprintf(back, BI_FDPASS "\n");
fflush(back);
send_fd(fileno(back));
exit(0);
case MODE_RESPONSE:
/* read challenge */
mode = -1;
cp = challenge;
ep = challenge + sizeof(challenge);
while (cp < ep && read(fileno(back), cp, 1) == 1) {
if (*cp++ == '\0') {
mode = MODE_CHALLENGE;
break;
}
}
if (mode != MODE_CHALLENGE) {
syslog(LOG_ERR,
"protocol error: bad/missing challenge");
exit(1);
}
/* read response */
cp = response;
ep = response + sizeof(response);
while (cp < ep && read(fileno(back), cp, 1) == 1) {
if (*cp++ == '\0') {
mode = MODE_RESPONSE;
break;
}
}
if (mode != MODE_RESPONSE) {
syslog(LOG_ERR,
"protocol error: bad/missing response");
exit(1);
}
/*
* Since the entry is locked we do not need to compare
* the passed in challenge to the S/Key database but
* maybe we should anyway?
*/
haskey = (skeychallenge2(fd, &skey, user, challenge) == 0);
break;
}
/*
* Ignore keyboard interrupt/suspend during database update.
*/
signal(SIGINT, SIG_IGN);
signal(SIGQUIT, SIG_IGN);
signal(SIGTSTP, SIG_IGN);
if (haskey && skeyverify(&skey, response) == 0) {
if (mode == MODE_LOGIN) {
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);
}
/* ARGSUSED */
void
quit(int signo)
{
_exit(1);
}
/* ARGSUSED */
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;
}
void
send_fd(int sock)
{
struct msghdr msg;
struct cmsghdr *cmp;
union {
struct cmsghdr hdr;
char buf[CMSG_SPACE(sizeof(int))];
} cmsgbuf;
memset(&msg, 0, sizeof(msg));
msg.msg_control = &cmsgbuf.buf;
msg.msg_controllen = sizeof(cmsgbuf.buf);
cmp = CMSG_FIRSTHDR(&msg);
cmp->cmsg_len = CMSG_LEN(sizeof(int));
cmp->cmsg_level = SOL_SOCKET;
cmp->cmsg_type = SCM_RIGHTS;
*(int *)CMSG_DATA(cmp) = fileno(skey.keyfile);
if (sendmsg(sock, &msg, 0) < 0)
syslog(LOG_ERR, "sendmsg: %m");
}