1 /* $OpenBSD: login_skey.c,v 1.30 2023/03/08 04:43:05 guenther Exp $ */
2
3 /*
4 * Copyright (c) 2000, 2001, 2004 Todd C. Miller <millert@openbsd.org>
5 *
6 * Permission to use, copy, modify, and distribute this software for any
7 * purpose with or without fee is hereby granted, provided that the above
8 * copyright notice and this permission notice appear in all copies.
9 *
10 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
11 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
12 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
13 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
14 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
15 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
16 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17 */
18
19 #include <sys/socket.h>
20 #include <sys/stat.h>
21 #include <sys/time.h>
22 #include <sys/resource.h>
23
24 #include <ctype.h>
25 #include <errno.h>
26 #include <fcntl.h>
27 #include <paths.h>
28 #include <pwd.h>
29 #include <readpassphrase.h>
30 #include <signal.h>
31 #include <stdio.h>
32 #include <stdlib.h>
33 #include <string.h>
34 #include <syslog.h>
35 #include <unistd.h>
36 #include <limits.h>
37 #include <err.h>
38
39 #include <login_cap.h>
40 #include <bsd_auth.h>
41 #include <skey.h>
42
43 #define MODE_LOGIN 0
44 #define MODE_CHALLENGE 1
45 #define MODE_RESPONSE 2
46
47 void quit(int);
48 void send_fd(int);
49 void suspend(int);
50
51 volatile sig_atomic_t resumed;
52 struct skey skey;
53
54 int
main(int argc,char * argv[])55 main(int argc, char *argv[])
56 {
57 FILE *back = NULL;
58 char *user = NULL, *cp, *ep;
59 char challenge[SKEY_MAX_CHALLENGE+17], response[SKEY_MAX_PW_LEN+1];
60 const char *errstr;
61 int ch, fd = -1, haskey = 0, mode = MODE_LOGIN;
62
63 (void)signal(SIGINT, quit);
64 (void)signal(SIGQUIT, quit);
65 (void)signal(SIGALRM, quit);
66 (void)signal(SIGTSTP, suspend);
67 (void)setpriority(PRIO_PROCESS, 0, 0);
68
69 if (pledge("stdio rpath wpath flock sendfd proc tty", NULL) == -1) {
70 syslog(LOG_AUTH|LOG_ERR, "pledge: %m");
71 exit(1);
72 }
73
74 openlog(NULL, LOG_ODELAY, LOG_AUTH);
75
76 while ((ch = getopt(argc, argv, "ds:v:")) != -1) {
77 switch (ch) {
78 case 'd':
79 back = stdout;
80 break;
81 case 's': /* service */
82 if (strcmp(optarg, "login") == 0)
83 mode = MODE_LOGIN;
84 else if (strcmp(optarg, "challenge") == 0)
85 mode = MODE_CHALLENGE;
86 else if (strcmp(optarg, "response") == 0)
87 mode = MODE_RESPONSE;
88 else {
89 syslog(LOG_ERR, "%s: invalid service", optarg);
90 exit(1);
91 }
92 break;
93 case 'v':
94 if (strncmp(optarg, "fd=", 3) == 0) {
95 fd = strtonum(optarg + 3, 0, INT_MAX, &errstr);
96 if (errstr != NULL) {
97 syslog(LOG_ERR, "fd is %s: %s",
98 errstr, optarg + 3);
99 fd = -1;
100 }
101 }
102 /* silently ignore unsupported variables */
103 break;
104 default:
105 syslog(LOG_ERR, "usage error");
106 exit(1);
107 }
108 }
109 argc -= optind;
110 argv += optind;
111
112 switch (argc) {
113 case 2: /* silently ignore class */
114 case 1:
115 user = *argv;
116 break;
117 default:
118 syslog(LOG_ERR, "usage error");
119 exit(1);
120 }
121
122 if (back == NULL && (back = fdopen(3, "r+")) == NULL) {
123 syslog(LOG_ERR, "reopening back channel: %m");
124 exit(1);
125 }
126
127 /*
128 * Note: our skeychallenge2() will always fill in the challenge,
129 * even if it has to create a fake one.
130 */
131 switch (mode) {
132 case MODE_LOGIN:
133 haskey = (skeychallenge2(fd, &skey, user, challenge) == 0);
134 strlcat(challenge, "\nS/Key Password:", sizeof(challenge));
135
136 /* time out getting passphrase after 2 minutes to avoid a DoS */
137 if (haskey)
138 alarm(120);
139 resumed = 0;
140 if (!readpassphrase(challenge, response, sizeof(response), 0))
141 exit(1);
142 if (response[0] == '\0')
143 readpassphrase("S/Key Password [echo on]: ",
144 response, sizeof(response), RPP_ECHO_ON);
145 alarm(0);
146 if (resumed) {
147 /*
148 * We were suspended by the user. Our lock is
149 * no longer valid so we must regain it so
150 * an attacker cannot do a partial guess of
151 * an S/Key response already in progress.
152 */
153 haskey = (skeylookup(&skey, user) == 0);
154 }
155 break;
156
157 case MODE_CHALLENGE:
158 haskey = (skeychallenge2(fd, &skey, user, challenge) == 0);
159 strlcat(challenge, "\nS/Key Password:", sizeof(challenge));
160 cp = auth_mkvalue(challenge);
161 if (cp == NULL) {
162 (void)fprintf(back, BI_VALUE " errormsg %s\n",
163 "unable to allocate memory");
164 (void)fprintf(back, BI_REJECT "\n");
165 exit(1);
166 }
167 fprintf(back, BI_VALUE " challenge %s\n", cp);
168 fprintf(back, BI_CHALLENGE "\n");
169 if (haskey) {
170 fprintf(back, BI_FDPASS "\n");
171 fflush(back);
172 send_fd(fileno(back));
173 }
174 exit(0);
175
176 case MODE_RESPONSE:
177 /* read challenge */
178 mode = -1;
179 cp = challenge;
180 ep = challenge + sizeof(challenge);
181 while (cp < ep && read(fileno(back), cp, 1) == 1) {
182 if (*cp++ == '\0') {
183 mode = MODE_CHALLENGE;
184 break;
185 }
186 }
187 if (mode != MODE_CHALLENGE) {
188 syslog(LOG_ERR,
189 "protocol error: bad/missing challenge");
190 exit(1);
191 }
192
193 /* read response */
194 cp = response;
195 ep = response + sizeof(response);
196 while (cp < ep && read(fileno(back), cp, 1) == 1) {
197 if (*cp++ == '\0') {
198 mode = MODE_RESPONSE;
199 break;
200 }
201 }
202 if (mode != MODE_RESPONSE) {
203 syslog(LOG_ERR,
204 "protocol error: bad/missing response");
205 exit(1);
206 }
207
208 /*
209 * Since the entry is locked we do not need to compare
210 * the passed in challenge to the S/Key database but
211 * maybe we should anyway?
212 */
213 haskey = (skeychallenge2(fd, &skey, user, challenge) == 0);
214 break;
215 }
216
217 /*
218 * Ignore keyboard interrupt/suspend during database update.
219 */
220 signal(SIGINT, SIG_IGN);
221 signal(SIGQUIT, SIG_IGN);
222 signal(SIGTSTP, SIG_IGN);
223
224 if (haskey && skeyverify(&skey, response) == 0) {
225 if (mode == MODE_LOGIN) {
226 if (skey.n <= 1)
227 printf("Warning! You MUST change your "
228 "S/Key password now!\n");
229 else if (skey.n < 5)
230 printf("Warning! Change S/Key password soon\n");
231 }
232 fprintf(back, BI_AUTH "\n");
233 fprintf(back, BI_SECURE "\n");
234 exit(0);
235 }
236 fprintf(back, BI_REJECT "\n");
237 exit(1);
238 }
239
240 void
quit(int signo)241 quit(int signo)
242 {
243
244 _exit(1);
245 }
246
247 void
suspend(int signo)248 suspend(int signo)
249 {
250 sigset_t nset;
251 int save_errno = errno;
252
253 /*
254 * Unlock the skey record so we don't sleep holding the lock.
255 * Unblock SIGTSTP, set it to the default action and then
256 * resend it so we are suspended properly.
257 * When we resume, reblock SIGTSTP, reset the signal handler,
258 * set a flag and restore errno.
259 */
260 alarm(0);
261 skey_unlock(&skey);
262 (void)signal(signo, SIG_DFL);
263 (void)sigemptyset(&nset);
264 (void)sigaddset(&nset, signo);
265 (void)sigprocmask(SIG_UNBLOCK, &nset, NULL);
266 (void)kill(getpid(), signo);
267 (void)sigprocmask(SIG_BLOCK, &nset, NULL);
268 (void)signal(signo, suspend);
269 resumed = 1;
270 errno = save_errno;
271 }
272
273 void
send_fd(int sock)274 send_fd(int sock)
275 {
276 struct msghdr msg;
277 struct cmsghdr *cmp;
278 union {
279 struct cmsghdr hdr;
280 char buf[CMSG_SPACE(sizeof(int))];
281 } cmsgbuf;
282
283 memset(&msg, 0, sizeof(msg));
284 msg.msg_control = &cmsgbuf.buf;
285 msg.msg_controllen = sizeof(cmsgbuf.buf);
286
287 cmp = CMSG_FIRSTHDR(&msg);
288 cmp->cmsg_len = CMSG_LEN(sizeof(int));
289 cmp->cmsg_level = SOL_SOCKET;
290 cmp->cmsg_type = SCM_RIGHTS;
291
292 *(int *)CMSG_DATA(cmp) = fileno(skey.keyfile);
293
294 if (sendmsg(sock, &msg, 0) == -1)
295 syslog(LOG_ERR, "sendmsg: %m");
296 }
297