1 /* $OpenBSD: auth2-chall.c,v 1.31 2006/08/05 08:28:24 dtucker Exp $ */ 2 /* 3 * Copyright (c) 2001 Markus Friedl. All rights reserved. 4 * Copyright (c) 2001 Per Allansson. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 #include "includes.h" 28 __RCSID("$FreeBSD$"); 29 30 #include <sys/types.h> 31 32 #include <stdarg.h> 33 #include <stdio.h> 34 #include <string.h> 35 36 #include "xmalloc.h" 37 #include "ssh2.h" 38 #include "key.h" 39 #include "hostfile.h" 40 #include "auth.h" 41 #include "buffer.h" 42 #include "packet.h" 43 #include "dispatch.h" 44 #include "log.h" 45 #include "servconf.h" 46 47 /* import */ 48 extern ServerOptions options; 49 50 static int auth2_challenge_start(Authctxt *); 51 static int send_userauth_info_request(Authctxt *); 52 static void input_userauth_info_response(int, u_int32_t, void *); 53 54 #ifdef BSD_AUTH 55 extern KbdintDevice bsdauth_device; 56 #else 57 #ifdef USE_PAM 58 extern KbdintDevice sshpam_device; 59 #endif 60 #ifdef SKEY 61 extern KbdintDevice skey_device; 62 #endif 63 #endif 64 65 KbdintDevice *devices[] = { 66 #ifdef BSD_AUTH 67 &bsdauth_device, 68 #else 69 #ifdef USE_PAM 70 &sshpam_device, 71 #endif 72 #ifdef SKEY 73 &skey_device, 74 #endif 75 #endif 76 NULL 77 }; 78 79 typedef struct KbdintAuthctxt KbdintAuthctxt; 80 struct KbdintAuthctxt 81 { 82 char *devices; 83 void *ctxt; 84 KbdintDevice *device; 85 u_int nreq; 86 }; 87 88 #ifdef USE_PAM 89 void 90 remove_kbdint_device(const char *devname) 91 { 92 int i, j; 93 94 for (i = 0; devices[i] != NULL; i++) 95 if (strcmp(devices[i]->name, devname) == 0) { 96 for (j = i; devices[j] != NULL; j++) 97 devices[j] = devices[j+1]; 98 i--; 99 } 100 } 101 #endif 102 103 static KbdintAuthctxt * 104 kbdint_alloc(const char *devs) 105 { 106 KbdintAuthctxt *kbdintctxt; 107 Buffer b; 108 int i; 109 110 #ifdef USE_PAM 111 if (!options.use_pam) 112 remove_kbdint_device("pam"); 113 #endif 114 115 kbdintctxt = xmalloc(sizeof(KbdintAuthctxt)); 116 if (strcmp(devs, "") == 0) { 117 buffer_init(&b); 118 for (i = 0; devices[i]; i++) { 119 if (buffer_len(&b) > 0) 120 buffer_append(&b, ",", 1); 121 buffer_append(&b, devices[i]->name, 122 strlen(devices[i]->name)); 123 } 124 buffer_append(&b, "\0", 1); 125 kbdintctxt->devices = xstrdup(buffer_ptr(&b)); 126 buffer_free(&b); 127 } else { 128 kbdintctxt->devices = xstrdup(devs); 129 } 130 debug("kbdint_alloc: devices '%s'", kbdintctxt->devices); 131 kbdintctxt->ctxt = NULL; 132 kbdintctxt->device = NULL; 133 kbdintctxt->nreq = 0; 134 135 return kbdintctxt; 136 } 137 static void 138 kbdint_reset_device(KbdintAuthctxt *kbdintctxt) 139 { 140 if (kbdintctxt->ctxt) { 141 kbdintctxt->device->free_ctx(kbdintctxt->ctxt); 142 kbdintctxt->ctxt = NULL; 143 } 144 kbdintctxt->device = NULL; 145 } 146 static void 147 kbdint_free(KbdintAuthctxt *kbdintctxt) 148 { 149 if (kbdintctxt->device) 150 kbdint_reset_device(kbdintctxt); 151 if (kbdintctxt->devices) { 152 xfree(kbdintctxt->devices); 153 kbdintctxt->devices = NULL; 154 } 155 xfree(kbdintctxt); 156 } 157 /* get next device */ 158 static int 159 kbdint_next_device(KbdintAuthctxt *kbdintctxt) 160 { 161 size_t len; 162 char *t; 163 int i; 164 165 if (kbdintctxt->device) 166 kbdint_reset_device(kbdintctxt); 167 do { 168 len = kbdintctxt->devices ? 169 strcspn(kbdintctxt->devices, ",") : 0; 170 171 if (len == 0) 172 break; 173 for (i = 0; devices[i]; i++) 174 if (strncmp(kbdintctxt->devices, devices[i]->name, len) == 0) 175 kbdintctxt->device = devices[i]; 176 t = kbdintctxt->devices; 177 kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL; 178 xfree(t); 179 debug2("kbdint_next_device: devices %s", kbdintctxt->devices ? 180 kbdintctxt->devices : "<empty>"); 181 } while (kbdintctxt->devices && !kbdintctxt->device); 182 183 return kbdintctxt->device ? 1 : 0; 184 } 185 186 /* 187 * try challenge-response, set authctxt->postponed if we have to 188 * wait for the response. 189 */ 190 int 191 auth2_challenge(Authctxt *authctxt, char *devs) 192 { 193 debug("auth2_challenge: user=%s devs=%s", 194 authctxt->user ? authctxt->user : "<nouser>", 195 devs ? devs : "<no devs>"); 196 197 if (authctxt->user == NULL || !devs) 198 return 0; 199 if (authctxt->kbdintctxt == NULL) 200 authctxt->kbdintctxt = kbdint_alloc(devs); 201 return auth2_challenge_start(authctxt); 202 } 203 204 /* unregister kbd-int callbacks and context */ 205 void 206 auth2_challenge_stop(Authctxt *authctxt) 207 { 208 /* unregister callback */ 209 dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL); 210 if (authctxt->kbdintctxt != NULL) { 211 kbdint_free(authctxt->kbdintctxt); 212 authctxt->kbdintctxt = NULL; 213 } 214 } 215 216 /* side effect: sets authctxt->postponed if a reply was sent*/ 217 static int 218 auth2_challenge_start(Authctxt *authctxt) 219 { 220 KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt; 221 222 debug2("auth2_challenge_start: devices %s", 223 kbdintctxt->devices ? kbdintctxt->devices : "<empty>"); 224 225 if (kbdint_next_device(kbdintctxt) == 0) { 226 auth2_challenge_stop(authctxt); 227 return 0; 228 } 229 debug("auth2_challenge_start: trying authentication method '%s'", 230 kbdintctxt->device->name); 231 232 if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) { 233 auth2_challenge_stop(authctxt); 234 return 0; 235 } 236 if (send_userauth_info_request(authctxt) == 0) { 237 auth2_challenge_stop(authctxt); 238 return 0; 239 } 240 dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, 241 &input_userauth_info_response); 242 243 authctxt->postponed = 1; 244 return 0; 245 } 246 247 static int 248 send_userauth_info_request(Authctxt *authctxt) 249 { 250 KbdintAuthctxt *kbdintctxt; 251 char *name, *instr, **prompts; 252 u_int i, *echo_on; 253 254 kbdintctxt = authctxt->kbdintctxt; 255 if (kbdintctxt->device->query(kbdintctxt->ctxt, 256 &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on)) 257 return 0; 258 259 packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST); 260 packet_put_cstring(name); 261 packet_put_cstring(instr); 262 packet_put_cstring(""); /* language not used */ 263 packet_put_int(kbdintctxt->nreq); 264 for (i = 0; i < kbdintctxt->nreq; i++) { 265 packet_put_cstring(prompts[i]); 266 packet_put_char(echo_on[i]); 267 } 268 packet_send(); 269 packet_write_wait(); 270 271 for (i = 0; i < kbdintctxt->nreq; i++) 272 xfree(prompts[i]); 273 xfree(prompts); 274 xfree(echo_on); 275 xfree(name); 276 xfree(instr); 277 return 1; 278 } 279 280 static void 281 input_userauth_info_response(int type, u_int32_t seq, void *ctxt) 282 { 283 Authctxt *authctxt = ctxt; 284 KbdintAuthctxt *kbdintctxt; 285 int authenticated = 0, res, len; 286 u_int i, nresp; 287 char **response = NULL, *method; 288 289 if (authctxt == NULL) 290 fatal("input_userauth_info_response: no authctxt"); 291 kbdintctxt = authctxt->kbdintctxt; 292 if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL) 293 fatal("input_userauth_info_response: no kbdintctxt"); 294 if (kbdintctxt->device == NULL) 295 fatal("input_userauth_info_response: no device"); 296 297 authctxt->postponed = 0; /* reset */ 298 nresp = packet_get_int(); 299 if (nresp != kbdintctxt->nreq) 300 fatal("input_userauth_info_response: wrong number of replies"); 301 if (nresp > 100) 302 fatal("input_userauth_info_response: too many replies"); 303 if (nresp > 0) { 304 response = xcalloc(nresp, sizeof(char *)); 305 for (i = 0; i < nresp; i++) 306 response[i] = packet_get_string(NULL); 307 } 308 packet_check_eom(); 309 310 res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response); 311 312 for (i = 0; i < nresp; i++) { 313 memset(response[i], 'r', strlen(response[i])); 314 xfree(response[i]); 315 } 316 if (response) 317 xfree(response); 318 319 switch (res) { 320 case 0: 321 /* Success! */ 322 authenticated = authctxt->valid ? 1 : 0; 323 break; 324 case 1: 325 /* Authentication needs further interaction */ 326 if (send_userauth_info_request(authctxt) == 1) 327 authctxt->postponed = 1; 328 break; 329 default: 330 /* Failure! */ 331 break; 332 } 333 334 len = strlen("keyboard-interactive") + 2 + 335 strlen(kbdintctxt->device->name); 336 method = xmalloc(len); 337 snprintf(method, len, "keyboard-interactive/%s", 338 kbdintctxt->device->name); 339 340 if (!authctxt->postponed) { 341 if (authenticated) { 342 auth2_challenge_stop(authctxt); 343 } else { 344 /* start next device */ 345 /* may set authctxt->postponed */ 346 auth2_challenge_start(authctxt); 347 } 348 } 349 userauth_finish(authctxt, authenticated, method); 350 xfree(method); 351 } 352 353 void 354 privsep_challenge_enable(void) 355 { 356 #if defined(BSD_AUTH) || defined(USE_PAM) || defined(SKEY) 357 int n = 0; 358 #endif 359 #ifdef BSD_AUTH 360 extern KbdintDevice mm_bsdauth_device; 361 #endif 362 #ifdef USE_PAM 363 extern KbdintDevice mm_sshpam_device; 364 #endif 365 #ifdef SKEY 366 extern KbdintDevice mm_skey_device; 367 #endif 368 369 #ifdef BSD_AUTH 370 devices[n++] = &mm_bsdauth_device; 371 #else 372 #ifdef USE_PAM 373 devices[n++] = &mm_sshpam_device; 374 #endif 375 #ifdef SKEY 376 devices[n++] = &mm_skey_device; 377 #endif 378 #endif 379 } 380