1 /* $OpenBSD: auth2-chall.c,v 1.36 2012/12/03 00:14:06 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 = xmalloc(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 if (kbdintctxt->devices) { 151 xfree(kbdintctxt->devices); 152 kbdintctxt->devices = NULL; 153 } 154 xfree(kbdintctxt); 155 } 156 /* get next device */ 157 static int 158 kbdint_next_device(KbdintAuthctxt *kbdintctxt) 159 { 160 size_t len; 161 char *t; 162 int i; 163 164 if (kbdintctxt->device) 165 kbdint_reset_device(kbdintctxt); 166 do { 167 len = kbdintctxt->devices ? 168 strcspn(kbdintctxt->devices, ",") : 0; 169 170 if (len == 0) 171 break; 172 for (i = 0; devices[i]; i++) 173 if (strncmp(kbdintctxt->devices, devices[i]->name, len) == 0) 174 kbdintctxt->device = devices[i]; 175 t = kbdintctxt->devices; 176 kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL; 177 xfree(t); 178 debug2("kbdint_next_device: devices %s", kbdintctxt->devices ? 179 kbdintctxt->devices : "<empty>"); 180 } while (kbdintctxt->devices && !kbdintctxt->device); 181 182 return kbdintctxt->device ? 1 : 0; 183 } 184 185 /* 186 * try challenge-response, set authctxt->postponed if we have to 187 * wait for the response. 188 */ 189 int 190 auth2_challenge(Authctxt *authctxt, char *devs) 191 { 192 debug("auth2_challenge: user=%s devs=%s", 193 authctxt->user ? authctxt->user : "<nouser>", 194 devs ? devs : "<no devs>"); 195 196 if (authctxt->user == NULL || !devs) 197 return 0; 198 if (authctxt->kbdintctxt == NULL) 199 authctxt->kbdintctxt = kbdint_alloc(devs); 200 return auth2_challenge_start(authctxt); 201 } 202 203 /* unregister kbd-int callbacks and context */ 204 void 205 auth2_challenge_stop(Authctxt *authctxt) 206 { 207 /* unregister callback */ 208 dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL); 209 if (authctxt->kbdintctxt != NULL) { 210 kbdint_free(authctxt->kbdintctxt); 211 authctxt->kbdintctxt = NULL; 212 } 213 } 214 215 /* side effect: sets authctxt->postponed if a reply was sent*/ 216 static int 217 auth2_challenge_start(Authctxt *authctxt) 218 { 219 KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt; 220 221 debug2("auth2_challenge_start: devices %s", 222 kbdintctxt->devices ? kbdintctxt->devices : "<empty>"); 223 224 if (kbdint_next_device(kbdintctxt) == 0) { 225 auth2_challenge_stop(authctxt); 226 return 0; 227 } 228 debug("auth2_challenge_start: trying authentication method '%s'", 229 kbdintctxt->device->name); 230 231 if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) { 232 auth2_challenge_stop(authctxt); 233 return 0; 234 } 235 if (send_userauth_info_request(authctxt) == 0) { 236 auth2_challenge_stop(authctxt); 237 return 0; 238 } 239 dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, 240 &input_userauth_info_response); 241 242 authctxt->postponed = 1; 243 return 0; 244 } 245 246 static int 247 send_userauth_info_request(Authctxt *authctxt) 248 { 249 KbdintAuthctxt *kbdintctxt; 250 char *name, *instr, **prompts; 251 u_int i, *echo_on; 252 253 kbdintctxt = authctxt->kbdintctxt; 254 if (kbdintctxt->device->query(kbdintctxt->ctxt, 255 &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on)) 256 return 0; 257 258 packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST); 259 packet_put_cstring(name); 260 packet_put_cstring(instr); 261 packet_put_cstring(""); /* language not used */ 262 packet_put_int(kbdintctxt->nreq); 263 for (i = 0; i < kbdintctxt->nreq; i++) { 264 packet_put_cstring(prompts[i]); 265 packet_put_char(echo_on[i]); 266 } 267 packet_send(); 268 packet_write_wait(); 269 270 for (i = 0; i < kbdintctxt->nreq; i++) 271 xfree(prompts[i]); 272 xfree(prompts); 273 xfree(echo_on); 274 xfree(name); 275 xfree(instr); 276 return 1; 277 } 278 279 static void 280 input_userauth_info_response(int type, u_int32_t seq, void *ctxt) 281 { 282 Authctxt *authctxt = ctxt; 283 KbdintAuthctxt *kbdintctxt; 284 int authenticated = 0, res; 285 u_int i, nresp; 286 const char *devicename = NULL; 287 char **response = NULL; 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 devicename = kbdintctxt->device->name; 334 if (!authctxt->postponed) { 335 if (authenticated) { 336 auth2_challenge_stop(authctxt); 337 } else { 338 /* start next device */ 339 /* may set authctxt->postponed */ 340 auth2_challenge_start(authctxt); 341 } 342 } 343 userauth_finish(authctxt, authenticated, "keyboard-interactive", 344 devicename); 345 } 346 347 void 348 privsep_challenge_enable(void) 349 { 350 #if defined(BSD_AUTH) || defined(USE_PAM) || defined(SKEY) 351 int n = 0; 352 #endif 353 #ifdef BSD_AUTH 354 extern KbdintDevice mm_bsdauth_device; 355 #endif 356 #ifdef USE_PAM 357 extern KbdintDevice mm_sshpam_device; 358 #endif 359 #ifdef SKEY 360 extern KbdintDevice mm_skey_device; 361 #endif 362 363 #ifdef BSD_AUTH 364 devices[n++] = &mm_bsdauth_device; 365 #else 366 #ifdef USE_PAM 367 devices[n++] = &mm_sshpam_device; 368 #endif 369 #ifdef SKEY 370 devices[n++] = &mm_skey_device; 371 #endif 372 #endif 373 } 374