1 /* $OpenBSD: auth2-chall.c,v 1.41 2014/02/02 03:44:31 djm 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 29 #include <sys/types.h> 30 31 #include <stdarg.h> 32 #include <stdio.h> 33 #include <string.h> 34 35 #include "xmalloc.h" 36 #include "ssh2.h" 37 #include "key.h" 38 #include "hostfile.h" 39 #include "auth.h" 40 #include "buffer.h" 41 #include "packet.h" 42 #include "dispatch.h" 43 #include "log.h" 44 #include "servconf.h" 45 46 /* import */ 47 extern ServerOptions options; 48 49 static int auth2_challenge_start(Authctxt *); 50 static int send_userauth_info_request(Authctxt *); 51 static void input_userauth_info_response(int, u_int32_t, void *); 52 53 #ifdef BSD_AUTH 54 extern KbdintDevice bsdauth_device; 55 #else 56 #ifdef USE_PAM 57 extern KbdintDevice sshpam_device; 58 #endif 59 #ifdef SKEY 60 extern KbdintDevice skey_device; 61 #endif 62 #endif 63 64 KbdintDevice *devices[] = { 65 #ifdef BSD_AUTH 66 &bsdauth_device, 67 #else 68 #ifdef USE_PAM 69 &sshpam_device, 70 #endif 71 #ifdef SKEY 72 &skey_device, 73 #endif 74 #endif 75 NULL 76 }; 77 78 typedef struct KbdintAuthctxt KbdintAuthctxt; 79 struct KbdintAuthctxt 80 { 81 char *devices; 82 void *ctxt; 83 KbdintDevice *device; 84 u_int nreq; 85 u_int devices_done; 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 = xcalloc(1, 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 free(kbdintctxt->devices); 152 explicit_bzero(kbdintctxt, sizeof(*kbdintctxt)); 153 free(kbdintctxt); 154 } 155 /* get next device */ 156 static int 157 kbdint_next_device(Authctxt *authctxt, KbdintAuthctxt *kbdintctxt) 158 { 159 size_t len; 160 char *t; 161 int i; 162 163 if (kbdintctxt->device) 164 kbdint_reset_device(kbdintctxt); 165 do { 166 len = kbdintctxt->devices ? 167 strcspn(kbdintctxt->devices, ",") : 0; 168 169 if (len == 0) 170 break; 171 for (i = 0; devices[i]; i++) { 172 if ((kbdintctxt->devices_done & (1 << i)) != 0 || 173 !auth2_method_allowed(authctxt, 174 "keyboard-interactive", devices[i]->name)) 175 continue; 176 if (strncmp(kbdintctxt->devices, devices[i]->name, 177 len) == 0) { 178 kbdintctxt->device = devices[i]; 179 kbdintctxt->devices_done |= 1 << i; 180 } 181 } 182 t = kbdintctxt->devices; 183 kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL; 184 free(t); 185 debug2("kbdint_next_device: devices %s", kbdintctxt->devices ? 186 kbdintctxt->devices : "<empty>"); 187 } while (kbdintctxt->devices && !kbdintctxt->device); 188 189 return kbdintctxt->device ? 1 : 0; 190 } 191 192 /* 193 * try challenge-response, set authctxt->postponed if we have to 194 * wait for the response. 195 */ 196 int 197 auth2_challenge(Authctxt *authctxt, char *devs) 198 { 199 debug("auth2_challenge: user=%s devs=%s", 200 authctxt->user ? authctxt->user : "<nouser>", 201 devs ? devs : "<no devs>"); 202 203 if (authctxt->user == NULL || !devs) 204 return 0; 205 if (authctxt->kbdintctxt == NULL) 206 authctxt->kbdintctxt = kbdint_alloc(devs); 207 return auth2_challenge_start(authctxt); 208 } 209 210 /* unregister kbd-int callbacks and context */ 211 void 212 auth2_challenge_stop(Authctxt *authctxt) 213 { 214 /* unregister callback */ 215 dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL); 216 if (authctxt->kbdintctxt != NULL) { 217 kbdint_free(authctxt->kbdintctxt); 218 authctxt->kbdintctxt = NULL; 219 } 220 } 221 222 /* side effect: sets authctxt->postponed if a reply was sent*/ 223 static int 224 auth2_challenge_start(Authctxt *authctxt) 225 { 226 KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt; 227 228 debug2("auth2_challenge_start: devices %s", 229 kbdintctxt->devices ? kbdintctxt->devices : "<empty>"); 230 231 if (kbdint_next_device(authctxt, kbdintctxt) == 0) { 232 auth2_challenge_stop(authctxt); 233 return 0; 234 } 235 debug("auth2_challenge_start: trying authentication method '%s'", 236 kbdintctxt->device->name); 237 238 if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) { 239 auth2_challenge_stop(authctxt); 240 return 0; 241 } 242 if (send_userauth_info_request(authctxt) == 0) { 243 auth2_challenge_stop(authctxt); 244 return 0; 245 } 246 dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, 247 &input_userauth_info_response); 248 249 authctxt->postponed = 1; 250 return 0; 251 } 252 253 static int 254 send_userauth_info_request(Authctxt *authctxt) 255 { 256 KbdintAuthctxt *kbdintctxt; 257 char *name, *instr, **prompts; 258 u_int i, *echo_on; 259 260 kbdintctxt = authctxt->kbdintctxt; 261 if (kbdintctxt->device->query(kbdintctxt->ctxt, 262 &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on)) 263 return 0; 264 265 packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST); 266 packet_put_cstring(name); 267 packet_put_cstring(instr); 268 packet_put_cstring(""); /* language not used */ 269 packet_put_int(kbdintctxt->nreq); 270 for (i = 0; i < kbdintctxt->nreq; i++) { 271 packet_put_cstring(prompts[i]); 272 packet_put_char(echo_on[i]); 273 } 274 packet_send(); 275 packet_write_wait(); 276 277 for (i = 0; i < kbdintctxt->nreq; i++) 278 free(prompts[i]); 279 free(prompts); 280 free(echo_on); 281 free(name); 282 free(instr); 283 return 1; 284 } 285 286 static void 287 input_userauth_info_response(int type, u_int32_t seq, void *ctxt) 288 { 289 Authctxt *authctxt = ctxt; 290 KbdintAuthctxt *kbdintctxt; 291 int authenticated = 0, res; 292 u_int i, nresp; 293 const char *devicename = NULL; 294 char **response = NULL; 295 296 if (authctxt == NULL) 297 fatal("input_userauth_info_response: no authctxt"); 298 kbdintctxt = authctxt->kbdintctxt; 299 if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL) 300 fatal("input_userauth_info_response: no kbdintctxt"); 301 if (kbdintctxt->device == NULL) 302 fatal("input_userauth_info_response: no device"); 303 304 authctxt->postponed = 0; /* reset */ 305 nresp = packet_get_int(); 306 if (nresp != kbdintctxt->nreq) 307 fatal("input_userauth_info_response: wrong number of replies"); 308 if (nresp > 100) 309 fatal("input_userauth_info_response: too many replies"); 310 if (nresp > 0) { 311 response = xcalloc(nresp, sizeof(char *)); 312 for (i = 0; i < nresp; i++) 313 response[i] = packet_get_string(NULL); 314 } 315 packet_check_eom(); 316 317 res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response); 318 319 for (i = 0; i < nresp; i++) { 320 explicit_bzero(response[i], strlen(response[i])); 321 free(response[i]); 322 } 323 free(response); 324 325 switch (res) { 326 case 0: 327 /* Success! */ 328 authenticated = authctxt->valid ? 1 : 0; 329 break; 330 case 1: 331 /* Authentication needs further interaction */ 332 if (send_userauth_info_request(authctxt) == 1) 333 authctxt->postponed = 1; 334 break; 335 default: 336 /* Failure! */ 337 break; 338 } 339 devicename = kbdintctxt->device->name; 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, "keyboard-interactive", 350 devicename); 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