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 }; 86 87 #ifdef USE_PAM 88 void 89 remove_kbdint_device(const char *devname) 90 { 91 int i, j; 92 93 for (i = 0; devices[i] != NULL; i++) 94 if (strcmp(devices[i]->name, devname) == 0) { 95 for (j = i; devices[j] != NULL; j++) 96 devices[j] = devices[j+1]; 97 i--; 98 } 99 } 100 #endif 101 102 static KbdintAuthctxt * 103 kbdint_alloc(const char *devs) 104 { 105 KbdintAuthctxt *kbdintctxt; 106 Buffer b; 107 int i; 108 109 #ifdef USE_PAM 110 if (!options.use_pam) 111 remove_kbdint_device("pam"); 112 #endif 113 114 kbdintctxt = xcalloc(1, sizeof(KbdintAuthctxt)); 115 if (strcmp(devs, "") == 0) { 116 buffer_init(&b); 117 for (i = 0; devices[i]; i++) { 118 if (buffer_len(&b) > 0) 119 buffer_append(&b, ",", 1); 120 buffer_append(&b, devices[i]->name, 121 strlen(devices[i]->name)); 122 } 123 buffer_append(&b, "\0", 1); 124 kbdintctxt->devices = xstrdup(buffer_ptr(&b)); 125 buffer_free(&b); 126 } else { 127 kbdintctxt->devices = xstrdup(devs); 128 } 129 debug("kbdint_alloc: devices '%s'", kbdintctxt->devices); 130 kbdintctxt->ctxt = NULL; 131 kbdintctxt->device = NULL; 132 kbdintctxt->nreq = 0; 133 134 return kbdintctxt; 135 } 136 static void 137 kbdint_reset_device(KbdintAuthctxt *kbdintctxt) 138 { 139 if (kbdintctxt->ctxt) { 140 kbdintctxt->device->free_ctx(kbdintctxt->ctxt); 141 kbdintctxt->ctxt = NULL; 142 } 143 kbdintctxt->device = NULL; 144 } 145 static void 146 kbdint_free(KbdintAuthctxt *kbdintctxt) 147 { 148 if (kbdintctxt->device) 149 kbdint_reset_device(kbdintctxt); 150 free(kbdintctxt->devices); 151 explicit_bzero(kbdintctxt, sizeof(*kbdintctxt)); 152 free(kbdintctxt); 153 } 154 /* get next device */ 155 static int 156 kbdint_next_device(Authctxt *authctxt, KbdintAuthctxt *kbdintctxt) 157 { 158 size_t len; 159 char *t; 160 int i; 161 162 if (kbdintctxt->device) 163 kbdint_reset_device(kbdintctxt); 164 do { 165 len = kbdintctxt->devices ? 166 strcspn(kbdintctxt->devices, ",") : 0; 167 168 if (len == 0) 169 break; 170 for (i = 0; devices[i]; i++) { 171 if (!auth2_method_allowed(authctxt, 172 "keyboard-interactive", devices[i]->name)) 173 continue; 174 if (strncmp(kbdintctxt->devices, devices[i]->name, len) == 0) 175 kbdintctxt->device = devices[i]; 176 } 177 t = kbdintctxt->devices; 178 kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL; 179 free(t); 180 debug2("kbdint_next_device: devices %s", kbdintctxt->devices ? 181 kbdintctxt->devices : "<empty>"); 182 } while (kbdintctxt->devices && !kbdintctxt->device); 183 184 return kbdintctxt->device ? 1 : 0; 185 } 186 187 /* 188 * try challenge-response, set authctxt->postponed if we have to 189 * wait for the response. 190 */ 191 int 192 auth2_challenge(Authctxt *authctxt, char *devs) 193 { 194 debug("auth2_challenge: user=%s devs=%s", 195 authctxt->user ? authctxt->user : "<nouser>", 196 devs ? devs : "<no devs>"); 197 198 if (authctxt->user == NULL || !devs) 199 return 0; 200 if (authctxt->kbdintctxt == NULL) 201 authctxt->kbdintctxt = kbdint_alloc(devs); 202 return auth2_challenge_start(authctxt); 203 } 204 205 /* unregister kbd-int callbacks and context */ 206 void 207 auth2_challenge_stop(Authctxt *authctxt) 208 { 209 /* unregister callback */ 210 dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL); 211 if (authctxt->kbdintctxt != NULL) { 212 kbdint_free(authctxt->kbdintctxt); 213 authctxt->kbdintctxt = NULL; 214 } 215 } 216 217 /* side effect: sets authctxt->postponed if a reply was sent*/ 218 static int 219 auth2_challenge_start(Authctxt *authctxt) 220 { 221 KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt; 222 223 debug2("auth2_challenge_start: devices %s", 224 kbdintctxt->devices ? kbdintctxt->devices : "<empty>"); 225 226 if (kbdint_next_device(authctxt, kbdintctxt) == 0) { 227 auth2_challenge_stop(authctxt); 228 return 0; 229 } 230 debug("auth2_challenge_start: trying authentication method '%s'", 231 kbdintctxt->device->name); 232 233 if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) { 234 auth2_challenge_stop(authctxt); 235 return 0; 236 } 237 if (send_userauth_info_request(authctxt) == 0) { 238 auth2_challenge_stop(authctxt); 239 return 0; 240 } 241 dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, 242 &input_userauth_info_response); 243 244 authctxt->postponed = 1; 245 return 0; 246 } 247 248 static int 249 send_userauth_info_request(Authctxt *authctxt) 250 { 251 KbdintAuthctxt *kbdintctxt; 252 char *name, *instr, **prompts; 253 u_int i, *echo_on; 254 255 kbdintctxt = authctxt->kbdintctxt; 256 if (kbdintctxt->device->query(kbdintctxt->ctxt, 257 &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on)) 258 return 0; 259 260 packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST); 261 packet_put_cstring(name); 262 packet_put_cstring(instr); 263 packet_put_cstring(""); /* language not used */ 264 packet_put_int(kbdintctxt->nreq); 265 for (i = 0; i < kbdintctxt->nreq; i++) { 266 packet_put_cstring(prompts[i]); 267 packet_put_char(echo_on[i]); 268 } 269 packet_send(); 270 packet_write_wait(); 271 272 for (i = 0; i < kbdintctxt->nreq; i++) 273 free(prompts[i]); 274 free(prompts); 275 free(echo_on); 276 free(name); 277 free(instr); 278 return 1; 279 } 280 281 static void 282 input_userauth_info_response(int type, u_int32_t seq, void *ctxt) 283 { 284 Authctxt *authctxt = ctxt; 285 KbdintAuthctxt *kbdintctxt; 286 int authenticated = 0, res; 287 u_int i, nresp; 288 const char *devicename = NULL; 289 char **response = NULL; 290 291 if (authctxt == NULL) 292 fatal("input_userauth_info_response: no authctxt"); 293 kbdintctxt = authctxt->kbdintctxt; 294 if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL) 295 fatal("input_userauth_info_response: no kbdintctxt"); 296 if (kbdintctxt->device == NULL) 297 fatal("input_userauth_info_response: no device"); 298 299 authctxt->postponed = 0; /* reset */ 300 nresp = packet_get_int(); 301 if (nresp != kbdintctxt->nreq) 302 fatal("input_userauth_info_response: wrong number of replies"); 303 if (nresp > 100) 304 fatal("input_userauth_info_response: too many replies"); 305 if (nresp > 0) { 306 response = xcalloc(nresp, sizeof(char *)); 307 for (i = 0; i < nresp; i++) 308 response[i] = packet_get_string(NULL); 309 } 310 packet_check_eom(); 311 312 res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response); 313 314 for (i = 0; i < nresp; i++) { 315 explicit_bzero(response[i], strlen(response[i])); 316 free(response[i]); 317 } 318 free(response); 319 320 switch (res) { 321 case 0: 322 /* Success! */ 323 authenticated = authctxt->valid ? 1 : 0; 324 break; 325 case 1: 326 /* Authentication needs further interaction */ 327 if (send_userauth_info_request(authctxt) == 1) 328 authctxt->postponed = 1; 329 break; 330 default: 331 /* Failure! */ 332 break; 333 } 334 devicename = kbdintctxt->device->name; 335 if (!authctxt->postponed) { 336 if (authenticated) { 337 auth2_challenge_stop(authctxt); 338 } else { 339 /* start next device */ 340 /* may set authctxt->postponed */ 341 auth2_challenge_start(authctxt); 342 } 343 } 344 userauth_finish(authctxt, authenticated, "keyboard-interactive", 345 devicename); 346 } 347 348 void 349 privsep_challenge_enable(void) 350 { 351 #if defined(BSD_AUTH) || defined(USE_PAM) || defined(SKEY) 352 int n = 0; 353 #endif 354 #ifdef BSD_AUTH 355 extern KbdintDevice mm_bsdauth_device; 356 #endif 357 #ifdef USE_PAM 358 extern KbdintDevice mm_sshpam_device; 359 #endif 360 #ifdef SKEY 361 extern KbdintDevice mm_skey_device; 362 #endif 363 364 #ifdef BSD_AUTH 365 devices[n++] = &mm_bsdauth_device; 366 #else 367 #ifdef USE_PAM 368 devices[n++] = &mm_sshpam_device; 369 #endif 370 #ifdef SKEY 371 devices[n++] = &mm_skey_device; 372 #endif 373 #endif 374 } 375