auth2-chall.c revision 1.13
1 /* $NetBSD: auth2-chall.c,v 1.13 2017/10/07 19:39:19 christos Exp $ */ 2 /* $OpenBSD: auth2-chall.c,v 1.48 2017/05/30 14:29:59 markus Exp $ */ 3 /* 4 * Copyright (c) 2001 Markus Friedl. All rights reserved. 5 * Copyright (c) 2001 Per Allansson. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 */ 27 28 #include "includes.h" 29 __RCSID("$NetBSD: auth2-chall.c,v 1.13 2017/10/07 19:39:19 christos Exp $"); 30 #include <sys/types.h> 31 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 remove_kbdint_device(const char *); 91 void 92 remove_kbdint_device(const char *xdevname) 93 { 94 int i, j; 95 96 for (i = 0; devices[i] != NULL; i++) 97 if (strcmp(devices[i]->name, xdevname) == 0) { 98 for (j = i; devices[j] != NULL; j++) 99 devices[j] = devices[j+1]; 100 i--; 101 } 102 } 103 #endif 104 105 static KbdintAuthctxt * 106 kbdint_alloc(const char *devs) 107 { 108 KbdintAuthctxt *kbdintctxt; 109 Buffer b; 110 int i; 111 112 #ifdef USE_PAM 113 if (!options.use_pam) 114 remove_kbdint_device("pam"); 115 #endif 116 117 kbdintctxt = xcalloc(1, sizeof(KbdintAuthctxt)); 118 if (strcmp(devs, "") == 0) { 119 buffer_init(&b); 120 for (i = 0; devices[i]; i++) { 121 if (buffer_len(&b) > 0) 122 buffer_append(&b, ",", 1); 123 buffer_append(&b, devices[i]->name, 124 strlen(devices[i]->name)); 125 } 126 if ((kbdintctxt->devices = sshbuf_dup_string(&b)) == NULL) 127 fatal("%s: sshbuf_dup_string failed", __func__); 128 buffer_free(&b); 129 } else { 130 kbdintctxt->devices = xstrdup(devs); 131 } 132 debug("kbdint_alloc: devices '%s'", kbdintctxt->devices); 133 kbdintctxt->ctxt = NULL; 134 kbdintctxt->device = NULL; 135 kbdintctxt->nreq = 0; 136 137 return kbdintctxt; 138 } 139 static void 140 kbdint_reset_device(KbdintAuthctxt *kbdintctxt) 141 { 142 if (kbdintctxt->ctxt) { 143 kbdintctxt->device->free_ctx(kbdintctxt->ctxt); 144 kbdintctxt->ctxt = NULL; 145 } 146 kbdintctxt->device = NULL; 147 } 148 static void 149 kbdint_free(KbdintAuthctxt *kbdintctxt) 150 { 151 if (kbdintctxt->device) 152 kbdint_reset_device(kbdintctxt); 153 free(kbdintctxt->devices); 154 explicit_bzero(kbdintctxt, sizeof(*kbdintctxt)); 155 free(kbdintctxt); 156 } 157 /* get next device */ 158 static int 159 kbdint_next_device(Authctxt *authctxt, KbdintAuthctxt *kbdintctxt) 160 { 161 size_t len; 162 char *t; 163 int i; 164 165 if (kbdintctxt->device) 166 kbdint_reset_device(kbdintctxt); 167 do { 168 len = kbdintctxt->devices ? 169 strcspn(kbdintctxt->devices, ",") : 0; 170 171 if (len == 0) 172 break; 173 for (i = 0; devices[i]; i++) { 174 if ((kbdintctxt->devices_done & (1 << i)) != 0 || 175 !auth2_method_allowed(authctxt, 176 "keyboard-interactive", devices[i]->name)) 177 continue; 178 if (strncmp(kbdintctxt->devices, devices[i]->name, 179 len) == 0) { 180 kbdintctxt->device = devices[i]; 181 kbdintctxt->devices_done |= 1 << i; 182 } 183 } 184 t = kbdintctxt->devices; 185 kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL; 186 free(t); 187 debug2("kbdint_next_device: devices %s", kbdintctxt->devices ? 188 kbdintctxt->devices : "<empty>"); 189 } while (kbdintctxt->devices && !kbdintctxt->device); 190 191 return kbdintctxt->device ? 1 : 0; 192 } 193 194 /* 195 * try challenge-response, set authctxt->postponed if we have to 196 * wait for the response. 197 */ 198 int 199 auth2_challenge(struct ssh *ssh, char *devs) 200 { 201 Authctxt *authctxt = ssh->authctxt; 202 debug("auth2_challenge: user=%s devs=%s", 203 authctxt->user ? authctxt->user : "<nouser>", 204 devs ? devs : "<no devs>"); 205 206 if (authctxt->user == NULL || !devs) 207 return 0; 208 if (authctxt->kbdintctxt == NULL) 209 authctxt->kbdintctxt = kbdint_alloc(devs); 210 return auth2_challenge_start(ssh); 211 } 212 213 /* unregister kbd-int callbacks and context */ 214 void 215 auth2_challenge_stop(struct ssh *ssh) 216 { 217 Authctxt *authctxt = ssh->authctxt; 218 /* unregister callback */ 219 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL); 220 if (authctxt->kbdintctxt != NULL) { 221 kbdint_free(authctxt->kbdintctxt); 222 authctxt->kbdintctxt = NULL; 223 } 224 } 225 226 /* side effect: sets authctxt->postponed if a reply was sent*/ 227 static int 228 auth2_challenge_start(struct ssh *ssh) 229 { 230 Authctxt *authctxt = ssh->authctxt; 231 KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt; 232 233 debug2("auth2_challenge_start: devices %s", 234 kbdintctxt->devices ? kbdintctxt->devices : "<empty>"); 235 236 if (kbdint_next_device(authctxt, kbdintctxt) == 0) { 237 auth2_challenge_stop(ssh); 238 return 0; 239 } 240 debug("auth2_challenge_start: trying authentication method '%s'", 241 kbdintctxt->device->name); 242 243 if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) { 244 auth2_challenge_stop(ssh); 245 return 0; 246 } 247 if (send_userauth_info_request(authctxt) == 0) { 248 auth2_challenge_stop(ssh); 249 return 0; 250 } 251 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_INFO_RESPONSE, 252 &input_userauth_info_response); 253 254 authctxt->postponed = 1; 255 return 0; 256 } 257 258 static int 259 send_userauth_info_request(Authctxt *authctxt) 260 { 261 KbdintAuthctxt *kbdintctxt; 262 char *name, *instr, **prompts; 263 u_int i, *echo_on; 264 265 kbdintctxt = authctxt->kbdintctxt; 266 if (kbdintctxt->device->query(kbdintctxt->ctxt, 267 &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on)) 268 return 0; 269 270 packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST); 271 packet_put_cstring(name); 272 packet_put_cstring(instr); 273 packet_put_cstring(""); /* language not used */ 274 packet_put_int(kbdintctxt->nreq); 275 for (i = 0; i < kbdintctxt->nreq; i++) { 276 packet_put_cstring(prompts[i]); 277 packet_put_char(echo_on[i]); 278 } 279 packet_send(); 280 packet_write_wait(); 281 282 for (i = 0; i < kbdintctxt->nreq; i++) 283 free(prompts[i]); 284 free(prompts); 285 free(echo_on); 286 free(name); 287 free(instr); 288 return 1; 289 } 290 291 static int 292 input_userauth_info_response(int type, u_int32_t seq, struct ssh *ssh) 293 { 294 Authctxt *authctxt = ssh->authctxt; 295 KbdintAuthctxt *kbdintctxt; 296 int authenticated = 0, res; 297 u_int i, nresp; 298 const char *devicename = NULL; 299 char **response = NULL; 300 301 if (authctxt == NULL) 302 fatal("input_userauth_info_response: no authctxt"); 303 kbdintctxt = authctxt->kbdintctxt; 304 if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL) 305 fatal("input_userauth_info_response: no kbdintctxt"); 306 if (kbdintctxt->device == NULL) 307 fatal("input_userauth_info_response: no device"); 308 309 authctxt->postponed = 0; /* reset */ 310 nresp = packet_get_int(); 311 if (nresp != kbdintctxt->nreq) 312 fatal("input_userauth_info_response: wrong number of replies"); 313 if (nresp > 100) 314 fatal("input_userauth_info_response: too many replies"); 315 if (nresp > 0) { 316 response = xcalloc(nresp, sizeof(char *)); 317 for (i = 0; i < nresp; i++) 318 response[i] = packet_get_string(NULL); 319 } 320 packet_check_eom(); 321 322 res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response); 323 324 for (i = 0; i < nresp; i++) { 325 explicit_bzero(response[i], strlen(response[i])); 326 free(response[i]); 327 } 328 free(response); 329 330 switch (res) { 331 case 0: 332 /* Success! */ 333 authenticated = authctxt->valid ? 1 : 0; 334 break; 335 case 1: 336 /* Authentication needs further interaction */ 337 if (send_userauth_info_request(authctxt) == 1) 338 authctxt->postponed = 1; 339 break; 340 default: 341 /* Failure! */ 342 break; 343 } 344 devicename = kbdintctxt->device->name; 345 if (!authctxt->postponed) { 346 if (authenticated) { 347 auth2_challenge_stop(ssh); 348 } else { 349 /* start next device */ 350 /* may set authctxt->postponed */ 351 auth2_challenge_start(ssh); 352 } 353 } 354 userauth_finish(ssh, authenticated, "keyboard-interactive", 355 devicename); 356 return 0; 357 } 358 359 void 360 privsep_challenge_enable(void) 361 { 362 #if defined(BSD_AUTH) || defined(USE_PAM) || defined(SKEY) 363 int n = 0; 364 #endif 365 #ifdef BSD_AUTH 366 extern KbdintDevice mm_bsdauth_device; 367 #endif 368 #ifdef USE_PAM 369 extern KbdintDevice mm_sshpam_device; 370 #endif 371 #ifdef SKEY 372 extern KbdintDevice mm_skey_device; 373 #endif 374 /* As long as SSHv1 has devices[0] hard coded this is fine */ 375 #ifdef BSD_AUTH 376 devices[n++] = &mm_bsdauth_device; 377 #endif 378 #ifdef USE_PAM 379 devices[n++] = &mm_sshpam_device; 380 #endif 381 #ifdef SKEY 382 devices[n++] = &mm_skey_device; 383 #endif 384 } 385
Indexes created Sun Apr 26 00:22:38 UTC 2026