auth2-chall.c revision 1.18
1 /* $NetBSD: auth2-chall.c,v 1.18 2020/05/28 17:05:49 christos Exp $ */ 2 /* $OpenBSD: auth2-chall.c,v 1.53 2020/02/26 13:40:09 jsg 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 1.18 2020/05/28 17:05:49 christos Exp $"); 30 #include <sys/types.h> 31 32 #include <stdlib.h> 33 #include <stdio.h> 34 #include <string.h> 35 #include <stdarg.h> 36 37 #include "xmalloc.h" 38 #include "ssh2.h" 39 #include "sshkey.h" 40 #include "hostfile.h" 41 #include "auth.h" 42 #include "sshbuf.h" 43 #include "packet.h" 44 #include "dispatch.h" 45 #include "ssherr.h" 46 #include "log.h" 47 #include "misc.h" 48 #include "servconf.h" 49 50 /* import */ 51 extern ServerOptions options; 52 53 static int auth2_challenge_start(struct ssh *); 54 static int send_userauth_info_request(struct ssh *); 55 static int input_userauth_info_response(int, u_int32_t, struct ssh *); 56 57 #ifdef BSD_AUTH 58 extern KbdintDevice bsdauth_device; 59 #else 60 #ifdef USE_PAM 61 extern KbdintDevice sshpam_device; 62 #endif 63 #ifdef SKEY 64 extern KbdintDevice skey_device; 65 #endif 66 #endif 67 68 KbdintDevice *devices[] = { 69 #ifdef BSD_AUTH 70 &bsdauth_device, 71 #else 72 #ifdef USE_PAM 73 &sshpam_device, 74 #endif 75 #ifdef SKEY 76 &skey_device, 77 #endif 78 #endif 79 NULL 80 }; 81 82 typedef struct KbdintAuthctxt KbdintAuthctxt; 83 struct KbdintAuthctxt 84 { 85 char *devices; 86 void *ctxt; 87 KbdintDevice *device; 88 u_int nreq; 89 u_int devices_done; 90 }; 91 92 #ifdef USE_PAM 93 void remove_kbdint_device(const char *); 94 void 95 remove_kbdint_device(const char *xdevname) 96 { 97 int i, j; 98 99 for (i = 0; devices[i] != NULL; i++) 100 if (strcmp(devices[i]->name, xdevname) == 0) { 101 for (j = i; devices[j] != NULL; j++) 102 devices[j] = devices[j+1]; 103 i--; 104 } 105 } 106 #endif 107 108 static KbdintAuthctxt * 109 kbdint_alloc(const char *devs) 110 { 111 KbdintAuthctxt *kbdintctxt; 112 struct sshbuf *b; 113 int i, r; 114 115 #ifdef USE_PAM 116 if (!options.use_pam) 117 remove_kbdint_device("pam"); 118 #endif 119 120 kbdintctxt = xcalloc(1, sizeof(KbdintAuthctxt)); 121 if (strcmp(devs, "") == 0) { 122 if ((b = sshbuf_new()) == NULL) 123 fatal("%s: sshbuf_new failed", __func__); 124 for (i = 0; devices[i]; i++) { 125 if ((r = sshbuf_putf(b, "%s%s", 126 sshbuf_len(b) ? "," : "", devices[i]->name)) != 0) 127 fatal("%s: buffer error: %s", 128 __func__, ssh_err(r)); 129 } 130 if ((kbdintctxt->devices = sshbuf_dup_string(b)) == NULL) 131 fatal("%s: sshbuf_dup_string failed", __func__); 132 sshbuf_free(b); 133 } else { 134 kbdintctxt->devices = xstrdup(devs); 135 } 136 debug("kbdint_alloc: devices '%s'", kbdintctxt->devices); 137 kbdintctxt->ctxt = NULL; 138 kbdintctxt->device = NULL; 139 kbdintctxt->nreq = 0; 140 141 return kbdintctxt; 142 } 143 static void 144 kbdint_reset_device(KbdintAuthctxt *kbdintctxt) 145 { 146 if (kbdintctxt->ctxt) { 147 kbdintctxt->device->free_ctx(kbdintctxt->ctxt); 148 kbdintctxt->ctxt = NULL; 149 } 150 kbdintctxt->device = NULL; 151 } 152 static void 153 kbdint_free(KbdintAuthctxt *kbdintctxt) 154 { 155 if (kbdintctxt->device) 156 kbdint_reset_device(kbdintctxt); 157 free(kbdintctxt->devices); 158 freezero(kbdintctxt, sizeof(*kbdintctxt)); 159 } 160 /* get next device */ 161 static int 162 kbdint_next_device(Authctxt *authctxt, KbdintAuthctxt *kbdintctxt) 163 { 164 size_t len; 165 char *t; 166 int i; 167 168 if (kbdintctxt->device) 169 kbdint_reset_device(kbdintctxt); 170 do { 171 len = kbdintctxt->devices ? 172 strcspn(kbdintctxt->devices, ",") : 0; 173 174 if (len == 0) 175 break; 176 for (i = 0; devices[i]; i++) { 177 if ((kbdintctxt->devices_done & (1 << i)) != 0 || 178 !auth2_method_allowed(authctxt, 179 "keyboard-interactive", devices[i]->name)) 180 continue; 181 if (strncmp(kbdintctxt->devices, devices[i]->name, 182 len) == 0) { 183 kbdintctxt->device = devices[i]; 184 kbdintctxt->devices_done |= 1 << i; 185 } 186 } 187 t = kbdintctxt->devices; 188 kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL; 189 free(t); 190 debug2("kbdint_next_device: devices %s", kbdintctxt->devices ? 191 kbdintctxt->devices : "<empty>"); 192 } while (kbdintctxt->devices && !kbdintctxt->device); 193 194 return kbdintctxt->device ? 1 : 0; 195 } 196 197 /* 198 * try challenge-response, set authctxt->postponed if we have to 199 * wait for the response. 200 */ 201 int 202 auth2_challenge(struct ssh *ssh, char *devs) 203 { 204 Authctxt *authctxt = ssh->authctxt; 205 debug("auth2_challenge: user=%s devs=%s", 206 authctxt->user ? authctxt->user : "<nouser>", 207 devs ? devs : "<no devs>"); 208 209 if (authctxt->user == NULL || !devs) 210 return 0; 211 if (authctxt->kbdintctxt == NULL) 212 authctxt->kbdintctxt = kbdint_alloc(devs); 213 return auth2_challenge_start(ssh); 214 } 215 216 /* unregister kbd-int callbacks and context */ 217 void 218 auth2_challenge_stop(struct ssh *ssh) 219 { 220 Authctxt *authctxt = ssh->authctxt; 221 /* unregister callback */ 222 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL); 223 if (authctxt->kbdintctxt != NULL) { 224 kbdint_free(authctxt->kbdintctxt); 225 authctxt->kbdintctxt = NULL; 226 } 227 } 228 229 /* side effect: sets authctxt->postponed if a reply was sent*/ 230 static int 231 auth2_challenge_start(struct ssh *ssh) 232 { 233 Authctxt *authctxt = ssh->authctxt; 234 KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt; 235 236 debug2("auth2_challenge_start: devices %s", 237 kbdintctxt->devices ? kbdintctxt->devices : "<empty>"); 238 239 if (kbdint_next_device(authctxt, kbdintctxt) == 0) { 240 auth2_challenge_stop(ssh); 241 return 0; 242 } 243 debug("auth2_challenge_start: trying authentication method '%s'", 244 kbdintctxt->device->name); 245 246 if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) { 247 auth2_challenge_stop(ssh); 248 return 0; 249 } 250 if (send_userauth_info_request(ssh) == 0) { 251 auth2_challenge_stop(ssh); 252 return 0; 253 } 254 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_INFO_RESPONSE, 255 &input_userauth_info_response); 256 257 authctxt->postponed = 1; 258 return 0; 259 } 260 261 static int 262 send_userauth_info_request(struct ssh *ssh) 263 { 264 Authctxt *authctxt = ssh->authctxt; 265 KbdintAuthctxt *kbdintctxt; 266 char *name, *instr, **prompts; 267 int r; 268 u_int i, *echo_on; 269 270 kbdintctxt = authctxt->kbdintctxt; 271 if (kbdintctxt->device->query(kbdintctxt->ctxt, 272 &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on)) 273 return 0; 274 275 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_INFO_REQUEST)) != 0 || 276 (r = sshpkt_put_cstring(ssh, name)) != 0 || 277 (r = sshpkt_put_cstring(ssh, instr)) != 0 || 278 (r = sshpkt_put_cstring(ssh, "")) != 0 || /* language not used */ 279 (r = sshpkt_put_u32(ssh, kbdintctxt->nreq)) != 0) 280 fatal("%s: %s", __func__, ssh_err(r)); 281 for (i = 0; i < kbdintctxt->nreq; i++) { 282 if ((r = sshpkt_put_cstring(ssh, prompts[i])) != 0 || 283 (r = sshpkt_put_u8(ssh, echo_on[i])) != 0) 284 fatal("%s: %s", __func__, ssh_err(r)); 285 } 286 if ((r = sshpkt_send(ssh)) != 0 || 287 (r = ssh_packet_write_wait(ssh)) < 0) 288 fatal("%s: %s", __func__, ssh_err(r)); 289 290 for (i = 0; i < kbdintctxt->nreq; i++) 291 free(prompts[i]); 292 free(prompts); 293 free(echo_on); 294 free(name); 295 free(instr); 296 return 1; 297 } 298 299 static int 300 input_userauth_info_response(int type, u_int32_t seq, struct ssh *ssh) 301 { 302 Authctxt *authctxt = ssh->authctxt; 303 KbdintAuthctxt *kbdintctxt; 304 int authenticated = 0, res; 305 int r; 306 u_int i, nresp; 307 const char *devicename = NULL; 308 char **response = NULL; 309 310 if (authctxt == NULL) 311 fatal("input_userauth_info_response: no authctxt"); 312 kbdintctxt = authctxt->kbdintctxt; 313 if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL) 314 fatal("input_userauth_info_response: no kbdintctxt"); 315 if (kbdintctxt->device == NULL) 316 fatal("input_userauth_info_response: no device"); 317 318 authctxt->postponed = 0; /* reset */ 319 if ((r = sshpkt_get_u32(ssh, &nresp)) != 0) 320 fatal("%s: %s", __func__, ssh_err(r)); 321 if (nresp != kbdintctxt->nreq) 322 fatal("input_userauth_info_response: wrong number of replies"); 323 if (nresp > 100) 324 fatal("input_userauth_info_response: too many replies"); 325 if (nresp > 0) { 326 response = xcalloc(nresp, sizeof(char *)); 327 for (i = 0; i < nresp; i++) 328 if ((r = sshpkt_get_cstring(ssh, &response[i], 329 NULL)) != 0) 330 fatal("%s: %s", __func__, ssh_err(r)); 331 } 332 if ((r = sshpkt_get_end(ssh)) != 0) 333 fatal("%s: %s", __func__, ssh_err(r)); 334 335 res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response); 336 337 for (i = 0; i < nresp; i++) { 338 explicit_bzero(response[i], strlen(response[i])); 339 free(response[i]); 340 } 341 free(response); 342 343 switch (res) { 344 case 0: 345 /* Success! */ 346 authenticated = authctxt->valid ? 1 : 0; 347 break; 348 case 1: 349 /* Authentication needs further interaction */ 350 if (send_userauth_info_request(ssh) == 1) 351 authctxt->postponed = 1; 352 break; 353 default: 354 /* Failure! */ 355 break; 356 } 357 devicename = kbdintctxt->device->name; 358 if (!authctxt->postponed) { 359 if (authenticated) { 360 auth2_challenge_stop(ssh); 361 } else { 362 /* start next device */ 363 /* may set authctxt->postponed */ 364 auth2_challenge_start(ssh); 365 } 366 } 367 userauth_finish(ssh, authenticated, "keyboard-interactive", 368 devicename); 369 return 0; 370 } 371 372 void 373 privsep_challenge_enable(void) 374 { 375 #if defined(BSD_AUTH) || defined(USE_PAM) || defined(SKEY) 376 int n = 0; 377 #endif 378 #ifdef BSD_AUTH 379 extern KbdintDevice mm_bsdauth_device; 380 #endif 381 #ifdef USE_PAM 382 extern KbdintDevice mm_sshpam_device; 383 #endif 384 #ifdef SKEY 385 extern KbdintDevice mm_skey_device; 386 #endif 387 /* As long as SSHv1 has devices[0] hard coded this is fine */ 388 #ifdef BSD_AUTH 389 devices[n++] = &mm_bsdauth_device; 390 #endif 391 #ifdef USE_PAM 392 devices[n++] = &mm_sshpam_device; 393 #endif 394 #ifdef SKEY 395 devices[n++] = &mm_skey_device; 396 #endif 397 } 398
Indexes created Mon Apr 27 00:23:16 UTC 2026