1/* $NetBSD: auth2-chall.c,v 1.19 2021/03/05 17:47:15 christos Exp $ */ 2/* $OpenBSD: auth2-chall.c,v 1.54 2020/10/18 11:32:01 djm Exp $ */ 3 4/* 5 * Copyright (c) 2001 Markus Friedl. All rights reserved. 6 * Copyright (c) 2001 Per Allansson. All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29#include "includes.h" 30__RCSID("$NetBSD: auth2-chall.c,v 1.19 2021/03/05 17:47:15 christos Exp $"); 31#include <sys/types.h> 32 33#include <stdlib.h> 34#include <stdio.h> 35#include <string.h> 36#include <stdarg.h> 37 38#include "xmalloc.h" 39#include "ssh2.h" 40#include "sshkey.h" 41#include "hostfile.h" 42#include "auth.h" 43#include "sshbuf.h" 44#include "packet.h" 45#include "dispatch.h" 46#include "ssherr.h" 47#include "log.h" 48#include "misc.h" 49#include "servconf.h" 50 51/* import */ 52extern ServerOptions options; 53 54static int auth2_challenge_start(struct ssh *); 55static int send_userauth_info_request(struct ssh *); 56static int input_userauth_info_response(int, u_int32_t, struct ssh *); 57 58#ifdef BSD_AUTH 59extern KbdintDevice bsdauth_device; 60#else 61#ifdef USE_PAM 62extern KbdintDevice sshpam_device; 63#endif 64#ifdef SKEY 65extern KbdintDevice skey_device; 66#endif 67#endif 68 69KbdintDevice *devices[] = { 70#ifdef BSD_AUTH 71 &bsdauth_device, 72#else 73#ifdef USE_PAM 74 &sshpam_device, 75#endif 76#ifdef SKEY 77 &skey_device, 78#endif 79#endif 80 NULL 81}; 82 83typedef struct KbdintAuthctxt KbdintAuthctxt; 84struct KbdintAuthctxt 85{ 86 char *devices; 87 void *ctxt; 88 KbdintDevice *device; 89 u_int nreq; 90 u_int devices_done; 91}; 92 93#ifdef USE_PAM 94void remove_kbdint_device(const char *); 95void 96remove_kbdint_device(const char *xdevname) 97{ 98 int i, j; 99 100 for (i = 0; devices[i] != NULL; i++) 101 if (strcmp(devices[i]->name, xdevname) == 0) { 102 for (j = i; devices[j] != NULL; j++) 103 devices[j] = devices[j+1]; 104 i--; 105 } 106} 107#endif 108 109static KbdintAuthctxt * 110kbdint_alloc(const char *devs) 111{ 112 KbdintAuthctxt *kbdintctxt; 113 struct sshbuf *b; 114 int i, r; 115 116#ifdef USE_PAM 117 if (!options.use_pam) 118 remove_kbdint_device("pam"); 119#endif 120 121 kbdintctxt = xcalloc(1, sizeof(KbdintAuthctxt)); 122 if (strcmp(devs, "") == 0) { 123 if ((b = sshbuf_new()) == NULL) 124 fatal_f("sshbuf_new failed"); 125 for (i = 0; devices[i]; i++) { 126 if ((r = sshbuf_putf(b, "%s%s", 127 sshbuf_len(b) ? "," : "", devices[i]->name)) != 0) 128 fatal_fr(r, "buffer error"); 129 } 130 if ((kbdintctxt->devices = sshbuf_dup_string(b)) == NULL) 131 fatal_f("sshbuf_dup_string failed"); 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} 143static void 144kbdint_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} 152static void 153kbdint_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 */ 161static int 162kbdint_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 */ 201int 202auth2_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 */ 217void 218auth2_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*/ 230static int 231auth2_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 261static int 262send_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_fr(r, "start packet"); 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_fr(r, "assemble packet"); 285 } 286 if ((r = sshpkt_send(ssh)) != 0 || 287 (r = ssh_packet_write_wait(ssh)) < 0) 288 fatal_fr(r, "send packet"); 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 299static int 300input_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_f("no authctxt"); 312 kbdintctxt = authctxt->kbdintctxt; 313 if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL) 314 fatal_f("no kbdintctxt"); 315 if (kbdintctxt->device == NULL) 316 fatal_f("no device"); 317 318 authctxt->postponed = 0; /* reset */ 319 if ((r = sshpkt_get_u32(ssh, &nresp)) != 0) 320 fatal_fr(r, "parse packet"); 321 if (nresp != kbdintctxt->nreq) 322 fatal_f("wrong number of replies"); 323 if (nresp > 100) 324 fatal_f("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], NULL)) != 0) 329 fatal_fr(r, "parse response"); 330 } 331 } 332 if ((r = sshpkt_get_end(ssh)) != 0) 333 fatal_fr(r, "parse packet"); 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 372void 373privsep_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