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 "misc.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 = 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 (!auth2_method_allowed(authctxt, 173 "keyboard-interactive", devices[i]->name)) 174 continue; 175 if (strncmp(kbdintctxt->devices, devices[i]->name, len) == 0) 176 kbdintctxt->device = devices[i]; 177 } 178 t = kbdintctxt->devices; 179 kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL; 180 free(t); 181 debug2("kbdint_next_device: devices %s", kbdintctxt->devices ? 182 kbdintctxt->devices : "<empty>"); 183 } while (kbdintctxt->devices && !kbdintctxt->device); 184 185 return kbdintctxt->device ? 1 : 0; 186 } 187 188 /* 189 * try challenge-response, set authctxt->postponed if we have to 190 * wait for the response. 191 */ 192 int 193 auth2_challenge(Authctxt *authctxt, char *devs) 194 { 195 debug("auth2_challenge: user=%s devs=%s", 196 authctxt->user ? authctxt->user : "<nouser>", 197 devs ? devs : "<no devs>"); 198 199 if (authctxt->user == NULL || !devs) 200 return 0; 201 if (authctxt->kbdintctxt == NULL) 202 authctxt->kbdintctxt = kbdint_alloc(devs); 203 return auth2_challenge_start(authctxt); 204 } 205 206 /* unregister kbd-int callbacks and context */ 207 void 208 auth2_challenge_stop(Authctxt *authctxt) 209 { 210 /* unregister callback */ 211 dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL); 212 if (authctxt->kbdintctxt != NULL) { 213 kbdint_free(authctxt->kbdintctxt); 214 authctxt->kbdintctxt = NULL; 215 } 216 } 217 218 /* side effect: sets authctxt->postponed if a reply was sent*/ 219 static int 220 auth2_challenge_start(Authctxt *authctxt) 221 { 222 KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt; 223 224 debug2("auth2_challenge_start: devices %s", 225 kbdintctxt->devices ? kbdintctxt->devices : "<empty>"); 226 227 if (kbdint_next_device(authctxt, kbdintctxt) == 0) { 228 auth2_challenge_stop(authctxt); 229 return 0; 230 } 231 debug("auth2_challenge_start: trying authentication method '%s'", 232 kbdintctxt->device->name); 233 234 if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) { 235 auth2_challenge_stop(authctxt); 236 return 0; 237 } 238 if (send_userauth_info_request(authctxt) == 0) { 239 auth2_challenge_stop(authctxt); 240 return 0; 241 } 242 dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, 243 &input_userauth_info_response); 244 245 authctxt->postponed = 1; 246 return 0; 247 } 248 249 static int 250 send_userauth_info_request(Authctxt *authctxt) 251 { 252 KbdintAuthctxt *kbdintctxt; 253 char *name, *instr, **prompts; 254 u_int i, *echo_on; 255 256 kbdintctxt = authctxt->kbdintctxt; 257 if (kbdintctxt->device->query(kbdintctxt->ctxt, 258 &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on)) 259 return 0; 260 261 packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST); 262 packet_put_cstring(name); 263 packet_put_cstring(instr); 264 packet_put_cstring(""); /* language not used */ 265 packet_put_int(kbdintctxt->nreq); 266 for (i = 0; i < kbdintctxt->nreq; i++) { 267 packet_put_cstring(prompts[i]); 268 packet_put_char(echo_on[i]); 269 } 270 packet_send(); 271 packet_write_wait(); 272 273 for (i = 0; i < kbdintctxt->nreq; i++) 274 free(prompts[i]); 275 free(prompts); 276 free(echo_on); 277 free(name); 278 free(instr); 279 return 1; 280 } 281 282 static void 283 input_userauth_info_response(int type, u_int32_t seq, void *ctxt) 284 { 285 Authctxt *authctxt = ctxt; 286 KbdintAuthctxt *kbdintctxt; 287 int authenticated = 0, res; 288 u_int i, nresp; 289 const char *devicename = NULL; 290 char **response = NULL; 291 292 if (authctxt == NULL) 293 fatal("input_userauth_info_response: no authctxt"); 294 kbdintctxt = authctxt->kbdintctxt; 295 if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL) 296 fatal("input_userauth_info_response: no kbdintctxt"); 297 if (kbdintctxt->device == NULL) 298 fatal("input_userauth_info_response: no device"); 299 300 authctxt->postponed = 0; /* reset */ 301 nresp = packet_get_int(); 302 if (nresp != kbdintctxt->nreq) 303 fatal("input_userauth_info_response: wrong number of replies"); 304 if (nresp > 100) 305 fatal("input_userauth_info_response: too many replies"); 306 if (nresp > 0) { 307 response = xcalloc(nresp, sizeof(char *)); 308 for (i = 0; i < nresp; i++) 309 response[i] = packet_get_string(NULL); 310 } 311 packet_check_eom(); 312 313 res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response); 314 315 for (i = 0; i < nresp; i++) { 316 explicit_bzero(response[i], strlen(response[i])); 317 free(response[i]); 318 } 319 free(response); 320 321 switch (res) { 322 case 0: 323 /* Success! */ 324 authenticated = authctxt->valid ? 1 : 0; 325 break; 326 case 1: 327 /* Authentication needs further interaction */ 328 if (send_userauth_info_request(authctxt) == 1) 329 authctxt->postponed = 1; 330 break; 331 default: 332 /* Failure! */ 333 break; 334 } 335 devicename = kbdintctxt->device->name; 336 if (!authctxt->postponed) { 337 if (authenticated) { 338 auth2_challenge_stop(authctxt); 339 } else { 340 /* start next device */ 341 /* may set authctxt->postponed */ 342 auth2_challenge_start(authctxt); 343 } 344 } 345 userauth_finish(authctxt, authenticated, "keyboard-interactive", 346 devicename); 347 } 348 349 void 350 privsep_challenge_enable(void) 351 { 352 #if defined(BSD_AUTH) || defined(USE_PAM) || defined(SKEY) 353 int n = 0; 354 #endif 355 #ifdef BSD_AUTH 356 extern KbdintDevice mm_bsdauth_device; 357 #endif 358 #ifdef USE_PAM 359 extern KbdintDevice mm_sshpam_device; 360 #endif 361 #ifdef SKEY 362 extern KbdintDevice mm_skey_device; 363 #endif 364 365 #ifdef BSD_AUTH 366 devices[n++] = &mm_bsdauth_device; 367 #else 368 #ifdef USE_PAM 369 devices[n++] = &mm_sshpam_device; 370 #endif 371 #ifdef SKEY 372 devices[n++] = &mm_skey_device; 373 #endif 374 #endif 375 } 376