1 /* $OpenBSD: auth2-chall.c,v 1.48 2017/05/30 14:29:59 markus 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(struct ssh *); 51 static int send_userauth_info_request(Authctxt *); 52 static int input_userauth_info_response(int, u_int32_t, struct ssh *); 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 u_int devices_done; 87 }; 88 89 #ifdef USE_PAM 90 void 91 remove_kbdint_device(const char *devname) 92 { 93 int i, j; 94 95 for (i = 0; devices[i] != NULL; i++) 96 if (strcmp(devices[i]->name, devname) == 0) { 97 for (j = i; devices[j] != NULL; j++) 98 devices[j] = devices[j+1]; 99 i--; 100 } 101 } 102 #endif 103 104 static KbdintAuthctxt * 105 kbdint_alloc(const char *devs) 106 { 107 KbdintAuthctxt *kbdintctxt; 108 Buffer b; 109 int i; 110 111 #ifdef USE_PAM 112 if (!options.use_pam) 113 remove_kbdint_device("pam"); 114 #endif 115 116 kbdintctxt = xcalloc(1, sizeof(KbdintAuthctxt)); 117 if (strcmp(devs, "") == 0) { 118 buffer_init(&b); 119 for (i = 0; devices[i]; i++) { 120 if (buffer_len(&b) > 0) 121 buffer_append(&b, ",", 1); 122 buffer_append(&b, devices[i]->name, 123 strlen(devices[i]->name)); 124 } 125 if ((kbdintctxt->devices = sshbuf_dup_string(&b)) == NULL) 126 fatal("%s: sshbuf_dup_string failed", __func__); 127 buffer_free(&b); 128 } else { 129 kbdintctxt->devices = xstrdup(devs); 130 } 131 debug("kbdint_alloc: devices '%s'", kbdintctxt->devices); 132 kbdintctxt->ctxt = NULL; 133 kbdintctxt->device = NULL; 134 kbdintctxt->nreq = 0; 135 136 return kbdintctxt; 137 } 138 static void 139 kbdint_reset_device(KbdintAuthctxt *kbdintctxt) 140 { 141 if (kbdintctxt->ctxt) { 142 kbdintctxt->device->free_ctx(kbdintctxt->ctxt); 143 kbdintctxt->ctxt = NULL; 144 } 145 kbdintctxt->device = NULL; 146 } 147 static void 148 kbdint_free(KbdintAuthctxt *kbdintctxt) 149 { 150 if (kbdintctxt->device) 151 kbdint_reset_device(kbdintctxt); 152 free(kbdintctxt->devices); 153 explicit_bzero(kbdintctxt, sizeof(*kbdintctxt)); 154 free(kbdintctxt); 155 } 156 /* get next device */ 157 static int 158 kbdint_next_device(Authctxt *authctxt, 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 ((kbdintctxt->devices_done & (1 << i)) != 0 || 174 !auth2_method_allowed(authctxt, 175 "keyboard-interactive", devices[i]->name)) 176 continue; 177 if (strncmp(kbdintctxt->devices, devices[i]->name, 178 len) == 0) { 179 kbdintctxt->device = devices[i]; 180 kbdintctxt->devices_done |= 1 << i; 181 } 182 } 183 t = kbdintctxt->devices; 184 kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL; 185 free(t); 186 debug2("kbdint_next_device: devices %s", kbdintctxt->devices ? 187 kbdintctxt->devices : "<empty>"); 188 } while (kbdintctxt->devices && !kbdintctxt->device); 189 190 return kbdintctxt->device ? 1 : 0; 191 } 192 193 /* 194 * try challenge-response, set authctxt->postponed if we have to 195 * wait for the response. 196 */ 197 int 198 auth2_challenge(struct ssh *ssh, char *devs) 199 { 200 Authctxt *authctxt = ssh->authctxt; 201 debug("auth2_challenge: user=%s devs=%s", 202 authctxt->user ? authctxt->user : "<nouser>", 203 devs ? devs : "<no devs>"); 204 205 if (authctxt->user == NULL || !devs) 206 return 0; 207 if (authctxt->kbdintctxt == NULL) 208 authctxt->kbdintctxt = kbdint_alloc(devs); 209 return auth2_challenge_start(ssh); 210 } 211 212 /* unregister kbd-int callbacks and context */ 213 void 214 auth2_challenge_stop(struct ssh *ssh) 215 { 216 Authctxt *authctxt = ssh->authctxt; 217 /* unregister callback */ 218 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL); 219 if (authctxt->kbdintctxt != NULL) { 220 kbdint_free(authctxt->kbdintctxt); 221 authctxt->kbdintctxt = NULL; 222 } 223 } 224 225 /* side effect: sets authctxt->postponed if a reply was sent*/ 226 static int 227 auth2_challenge_start(struct ssh *ssh) 228 { 229 Authctxt *authctxt = ssh->authctxt; 230 KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt; 231 232 debug2("auth2_challenge_start: devices %s", 233 kbdintctxt->devices ? kbdintctxt->devices : "<empty>"); 234 235 if (kbdint_next_device(authctxt, kbdintctxt) == 0) { 236 auth2_challenge_stop(ssh); 237 return 0; 238 } 239 debug("auth2_challenge_start: trying authentication method '%s'", 240 kbdintctxt->device->name); 241 242 if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) { 243 auth2_challenge_stop(ssh); 244 return 0; 245 } 246 if (send_userauth_info_request(authctxt) == 0) { 247 auth2_challenge_stop(ssh); 248 return 0; 249 } 250 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_INFO_RESPONSE, 251 &input_userauth_info_response); 252 253 authctxt->postponed = 1; 254 return 0; 255 } 256 257 static int 258 send_userauth_info_request(Authctxt *authctxt) 259 { 260 KbdintAuthctxt *kbdintctxt; 261 char *name, *instr, **prompts; 262 u_int i, *echo_on; 263 264 kbdintctxt = authctxt->kbdintctxt; 265 if (kbdintctxt->device->query(kbdintctxt->ctxt, 266 &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on)) 267 return 0; 268 269 packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST); 270 packet_put_cstring(name); 271 packet_put_cstring(instr); 272 packet_put_cstring(""); /* language not used */ 273 packet_put_int(kbdintctxt->nreq); 274 for (i = 0; i < kbdintctxt->nreq; i++) { 275 packet_put_cstring(prompts[i]); 276 packet_put_char(echo_on[i]); 277 } 278 packet_send(); 279 packet_write_wait(); 280 281 for (i = 0; i < kbdintctxt->nreq; i++) 282 free(prompts[i]); 283 free(prompts); 284 free(echo_on); 285 free(name); 286 free(instr); 287 return 1; 288 } 289 290 static int 291 input_userauth_info_response(int type, u_int32_t seq, struct ssh *ssh) 292 { 293 Authctxt *authctxt = ssh->authctxt; 294 KbdintAuthctxt *kbdintctxt; 295 int authenticated = 0, res; 296 u_int i, nresp; 297 const char *devicename = NULL; 298 char **response = NULL; 299 300 if (authctxt == NULL) 301 fatal("input_userauth_info_response: no authctxt"); 302 kbdintctxt = authctxt->kbdintctxt; 303 if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL) 304 fatal("input_userauth_info_response: no kbdintctxt"); 305 if (kbdintctxt->device == NULL) 306 fatal("input_userauth_info_response: no device"); 307 308 authctxt->postponed = 0; /* reset */ 309 nresp = packet_get_int(); 310 if (nresp != kbdintctxt->nreq) 311 fatal("input_userauth_info_response: wrong number of replies"); 312 if (nresp > 100) 313 fatal("input_userauth_info_response: too many replies"); 314 if (nresp > 0) { 315 response = xcalloc(nresp, sizeof(char *)); 316 for (i = 0; i < nresp; i++) 317 response[i] = packet_get_string(NULL); 318 } 319 packet_check_eom(); 320 321 res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response); 322 323 for (i = 0; i < nresp; i++) { 324 explicit_bzero(response[i], strlen(response[i])); 325 free(response[i]); 326 } 327 free(response); 328 329 switch (res) { 330 case 0: 331 /* Success! */ 332 authenticated = authctxt->valid ? 1 : 0; 333 break; 334 case 1: 335 /* Authentication needs further interaction */ 336 if (send_userauth_info_request(authctxt) == 1) 337 authctxt->postponed = 1; 338 break; 339 default: 340 /* Failure! */ 341 break; 342 } 343 devicename = kbdintctxt->device->name; 344 if (!authctxt->postponed) { 345 if (authenticated) { 346 auth2_challenge_stop(ssh); 347 } else { 348 /* start next device */ 349 /* may set authctxt->postponed */ 350 auth2_challenge_start(ssh); 351 } 352 } 353 userauth_finish(ssh, authenticated, "keyboard-interactive", 354 devicename); 355 return 0; 356 } 357 358 void 359 privsep_challenge_enable(void) 360 { 361 #if defined(BSD_AUTH) || defined(USE_PAM) || defined(SKEY) 362 int n = 0; 363 #endif 364 #ifdef BSD_AUTH 365 extern KbdintDevice mm_bsdauth_device; 366 #endif 367 #ifdef USE_PAM 368 extern KbdintDevice mm_sshpam_device; 369 #endif 370 #ifdef SKEY 371 extern KbdintDevice mm_skey_device; 372 #endif 373 374 #ifdef BSD_AUTH 375 devices[n++] = &mm_bsdauth_device; 376 #else 377 #ifdef USE_PAM 378 devices[n++] = &mm_sshpam_device; 379 #endif 380 #ifdef SKEY 381 devices[n++] = &mm_skey_device; 382 #endif 383 #endif 384 } 385