1 /* $OpenBSD: login_skey.c,v 1.14 2004/08/08 19:32:45 deraadt Exp $ */ 2 3 /* 4 * Copyright (c) 2000, 2001, 2004 Todd C. Miller <Todd.Miller@courtesan.com> 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/param.h> 20 #include <sys/socket.h> 21 #include <sys/stat.h> 22 #include <sys/time.h> 23 #include <sys/resource.h> 24 25 #include <ctype.h> 26 #include <errno.h> 27 #include <fcntl.h> 28 #include <paths.h> 29 #include <pwd.h> 30 #include <readpassphrase.h> 31 #include <signal.h> 32 #include <stdio.h> 33 #include <stdlib.h> 34 #include <string.h> 35 #include <syslog.h> 36 #include <unistd.h> 37 38 #include <login_cap.h> 39 #include <bsd_auth.h> 40 #include <skey.h> 41 42 #define MODE_LOGIN 0 43 #define MODE_CHALLENGE 1 44 #define MODE_RESPONSE 2 45 46 void quit(int); 47 void send_fd(int); 48 void suspend(int); 49 50 volatile sig_atomic_t resumed; 51 struct skey skey; 52 53 int 54 main(int argc, char *argv[]) 55 { 56 FILE *back = NULL; 57 char *user = NULL, *cp, *ep; 58 char challenge[SKEY_MAX_CHALLENGE+17], response[SKEY_MAX_PW_LEN+1]; 59 const char *errstr; 60 int ch, fd = -1, haskey = 0, mode = MODE_LOGIN; 61 62 (void)signal(SIGINT, quit); 63 (void)signal(SIGQUIT, quit); 64 (void)signal(SIGALRM, quit); 65 (void)signal(SIGTSTP, suspend); 66 (void)setpriority(PRIO_PROCESS, 0, 0); 67 68 openlog(NULL, LOG_ODELAY, LOG_AUTH); 69 70 while ((ch = getopt(argc, argv, "ds:v:")) != -1) { 71 switch (ch) { 72 case 'd': 73 back = stdout; 74 break; 75 case 's': /* service */ 76 if (strcmp(optarg, "login") == 0) 77 mode = MODE_LOGIN; 78 else if (strcmp(optarg, "challenge") == 0) 79 mode = MODE_CHALLENGE; 80 else if (strcmp(optarg, "response") == 0) 81 mode = MODE_RESPONSE; 82 else { 83 syslog(LOG_ERR, "%s: invalid service", optarg); 84 exit(1); 85 } 86 break; 87 case 'v': 88 if (strncmp(optarg, "fd=", 3) == 0) { 89 fd = strtonum(optarg + 3, 0, INT_MAX, &errstr); 90 if (errstr != NULL) { 91 syslog(LOG_ERR, "fd is %s: %s", 92 errstr, optarg + 3); 93 fd = -1; 94 } 95 } 96 /* silently ignore unsupported variables */ 97 break; 98 default: 99 syslog(LOG_ERR, "usage error"); 100 exit(1); 101 } 102 } 103 argc -= optind; 104 argv += optind; 105 106 switch (argc) { 107 case 2: /* silently ignore class */ 108 case 1: 109 user = *argv; 110 break; 111 default: 112 syslog(LOG_ERR, "usage error"); 113 exit(1); 114 } 115 116 if (back == NULL && (back = fdopen(3, "r+")) == NULL) { 117 syslog(LOG_ERR, "reopening back channel: %m"); 118 exit(1); 119 } 120 121 /* 122 * Note: our skeychallenge2() will always fill in the challenge, 123 * even if it has to create a fake one. 124 */ 125 switch (mode) { 126 case MODE_LOGIN: 127 haskey = (skeychallenge2(fd, &skey, user, challenge) == 0); 128 strlcat(challenge, "\nS/Key Password: ", sizeof(challenge)); 129 130 /* time out getting passphrase after 2 minutes to avoid a DoS */ 131 if (haskey) 132 alarm(120); 133 resumed = 0; 134 if (!readpassphrase(challenge, response, sizeof(response), 0)) 135 exit(1); 136 if (response[0] == '\0') 137 readpassphrase("S/Key Password [echo on]: ", 138 response, sizeof(response), RPP_ECHO_ON); 139 alarm(0); 140 if (resumed) { 141 /* 142 * We were suspended by the user. Our lock is 143 * no longer valid so we must regain it so 144 * an attacker cannot do a partial guess of 145 * an S/Key response already in progress. 146 */ 147 haskey = (skeylookup(&skey, user) == 0); 148 } 149 break; 150 151 case MODE_CHALLENGE: 152 haskey = (skeychallenge2(fd, &skey, user, challenge) == 0); 153 strlcat(challenge, "\nS/Key Password: ", sizeof(challenge)); 154 fprintf(back, BI_VALUE " challenge %s\n", 155 auth_mkvalue(challenge)); 156 fprintf(back, BI_CHALLENGE "\n"); 157 fprintf(back, BI_FDPASS "\n"); 158 fflush(back); 159 send_fd(fileno(back)); 160 exit(0); 161 162 case MODE_RESPONSE: 163 /* read challenge */ 164 mode = -1; 165 cp = challenge; 166 ep = challenge + sizeof(challenge); 167 while (cp < ep && read(fileno(back), cp, 1) == 1) { 168 if (*cp++ == '\0') { 169 mode = MODE_CHALLENGE; 170 break; 171 } 172 } 173 if (mode != MODE_CHALLENGE) { 174 syslog(LOG_ERR, 175 "protocol error: bad/missing challenge"); 176 exit(1); 177 } 178 179 /* read response */ 180 cp = response; 181 ep = response + sizeof(response); 182 while (cp < ep && read(fileno(back), cp, 1) == 1) { 183 if (*cp++ == '\0') { 184 mode = MODE_RESPONSE; 185 break; 186 } 187 } 188 if (mode != MODE_RESPONSE) { 189 syslog(LOG_ERR, 190 "protocol error: bad/missing response"); 191 exit(1); 192 } 193 194 /* 195 * Since the entry is locked we do not need to compare 196 * the passed in challenge to the S/Key database but 197 * maybe we should anyway? 198 */ 199 haskey = (skeychallenge2(fd, &skey, user, challenge) == 0); 200 break; 201 } 202 203 /* 204 * Ignore keyboard interupt/suspend during database update. 205 */ 206 signal(SIGINT, SIG_IGN); 207 signal(SIGQUIT, SIG_IGN); 208 signal(SIGTSTP, SIG_IGN); 209 210 if (haskey && skeyverify(&skey, response) == 0) { 211 if (mode == MODE_LOGIN) { 212 if (skey.n <= 1) 213 printf("Warning! You MUST change your " 214 "S/Key password now!\n"); 215 else if (skey.n < 5) 216 printf("Warning! Change S/Key password soon\n"); 217 } 218 fprintf(back, BI_AUTH "\n"); 219 fprintf(back, BI_SECURE "\n"); 220 exit(0); 221 } 222 fprintf(back, BI_REJECT "\n"); 223 exit(1); 224 } 225 226 void 227 quit(int signo) 228 { 229 230 _exit(1); 231 } 232 233 void 234 suspend(int signo) 235 { 236 sigset_t nset; 237 int save_errno = errno; 238 239 /* 240 * Unlock the skey record so we don't sleep holding the lock. 241 * Unblock SIGTSTP, set it to the default action and then 242 * resend it so we are suspended properly. 243 * When we resume, reblock SIGTSTP, reset the signal handler, 244 * set a flag and restore errno. 245 */ 246 alarm(0); 247 skey_unlock(&skey); 248 (void)signal(signo, SIG_DFL); 249 (void)sigemptyset(&nset); 250 (void)sigaddset(&nset, signo); 251 (void)sigprocmask(SIG_UNBLOCK, &nset, NULL); 252 (void)kill(getpid(), signo); 253 (void)sigprocmask(SIG_BLOCK, &nset, NULL); 254 (void)signal(signo, suspend); 255 resumed = 1; 256 errno = save_errno; 257 } 258 259 void 260 send_fd(int fd) 261 { 262 struct msghdr msg; 263 struct cmsghdr *cmp; 264 char cmsgbuf[CMSG_LEN(sizeof(int))]; 265 266 memset(&msg, 0, sizeof(msg)); 267 msg.msg_control = cmsgbuf; 268 msg.msg_controllen = sizeof(cmsgbuf); 269 270 cmp = (struct cmsghdr *)cmsgbuf; 271 cmp->cmsg_len = sizeof(cmsgbuf); 272 cmp->cmsg_level = SOL_SOCKET; 273 cmp->cmsg_type = SCM_RIGHTS; 274 275 *(int *)CMSG_DATA(cmsgbuf) = fileno(skey.keyfile); 276 277 if (sendmsg(fd, &msg, 0) < 0) 278 syslog(LOG_ERR, "sendmsg: %m"); 279 } 280