auth2-chall.c revision 255767
1/* $OpenBSD: auth2-chall.c,v 1.38 2013/05/17 00:13:13 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 */ 47extern ServerOptions options; 48 49static int auth2_challenge_start(Authctxt *); 50static int send_userauth_info_request(Authctxt *); 51static void input_userauth_info_response(int, u_int32_t, void *); 52 53#ifdef BSD_AUTH 54extern KbdintDevice bsdauth_device; 55#else 56#ifdef USE_PAM 57extern KbdintDevice sshpam_device; 58#endif 59#ifdef SKEY 60extern KbdintDevice skey_device; 61#endif 62#endif 63 64KbdintDevice *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 78typedef struct KbdintAuthctxt KbdintAuthctxt; 79struct KbdintAuthctxt 80{ 81 char *devices; 82 void *ctxt; 83 KbdintDevice *device; 84 u_int nreq; 85}; 86 87#ifdef USE_PAM 88void 89remove_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 102static KbdintAuthctxt * 103kbdint_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} 136static void 137kbdint_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} 145static void 146kbdint_free(KbdintAuthctxt *kbdintctxt) 147{ 148 if (kbdintctxt->device) 149 kbdint_reset_device(kbdintctxt); 150 free(kbdintctxt->devices); 151 bzero(kbdintctxt, sizeof(*kbdintctxt)); 152 free(kbdintctxt); 153} 154/* get next device */ 155static int 156kbdint_next_device(Authctxt *authctxt, KbdintAuthctxt *kbdintctxt) 157{ 158 size_t len; 159 char *t; 160 int i; 161 162 if (kbdintctxt->device) 163 kbdint_reset_device(kbdintctxt); 164 do { 165 len = kbdintctxt->devices ? 166 strcspn(kbdintctxt->devices, ",") : 0; 167 168 if (len == 0) 169 break; 170 for (i = 0; devices[i]; i++) { 171 if (!auth2_method_allowed(authctxt, 172 "keyboard-interactive", devices[i]->name)) 173 continue; 174 if (strncmp(kbdintctxt->devices, devices[i]->name, len) == 0) 175 kbdintctxt->device = devices[i]; 176 } 177 t = kbdintctxt->devices; 178 kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL; 179 free(t); 180 debug2("kbdint_next_device: devices %s", kbdintctxt->devices ? 181 kbdintctxt->devices : "<empty>"); 182 } while (kbdintctxt->devices && !kbdintctxt->device); 183 184 return kbdintctxt->device ? 1 : 0; 185} 186 187/* 188 * try challenge-response, set authctxt->postponed if we have to 189 * wait for the response. 190 */ 191int 192auth2_challenge(Authctxt *authctxt, char *devs) 193{ 194 debug("auth2_challenge: user=%s devs=%s", 195 authctxt->user ? authctxt->user : "<nouser>", 196 devs ? devs : "<no devs>"); 197 198 if (authctxt->user == NULL || !devs) 199 return 0; 200 if (authctxt->kbdintctxt == NULL) 201 authctxt->kbdintctxt = kbdint_alloc(devs); 202 return auth2_challenge_start(authctxt); 203} 204 205/* unregister kbd-int callbacks and context */ 206void 207auth2_challenge_stop(Authctxt *authctxt) 208{ 209 /* unregister callback */ 210 dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL); 211 if (authctxt->kbdintctxt != NULL) { 212 kbdint_free(authctxt->kbdintctxt); 213 authctxt->kbdintctxt = NULL; 214 } 215} 216 217/* side effect: sets authctxt->postponed if a reply was sent*/ 218static int 219auth2_challenge_start(Authctxt *authctxt) 220{ 221 KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt; 222 223 debug2("auth2_challenge_start: devices %s", 224 kbdintctxt->devices ? kbdintctxt->devices : "<empty>"); 225 226 if (kbdint_next_device(authctxt, kbdintctxt) == 0) { 227 auth2_challenge_stop(authctxt); 228 return 0; 229 } 230 debug("auth2_challenge_start: trying authentication method '%s'", 231 kbdintctxt->device->name); 232 233 if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) { 234 auth2_challenge_stop(authctxt); 235 return 0; 236 } 237 if (send_userauth_info_request(authctxt) == 0) { 238 auth2_challenge_stop(authctxt); 239 return 0; 240 } 241 dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, 242 &input_userauth_info_response); 243 244 authctxt->postponed = 1; 245 return 0; 246} 247 248static int 249send_userauth_info_request(Authctxt *authctxt) 250{ 251 KbdintAuthctxt *kbdintctxt; 252 char *name, *instr, **prompts; 253 u_int i, *echo_on; 254 255 kbdintctxt = authctxt->kbdintctxt; 256 if (kbdintctxt->device->query(kbdintctxt->ctxt, 257 &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on)) 258 return 0; 259 260 packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST); 261 packet_put_cstring(name); 262 packet_put_cstring(instr); 263 packet_put_cstring(""); /* language not used */ 264 packet_put_int(kbdintctxt->nreq); 265 for (i = 0; i < kbdintctxt->nreq; i++) { 266 packet_put_cstring(prompts[i]); 267 packet_put_char(echo_on[i]); 268 } 269 packet_send(); 270 packet_write_wait(); 271 272 for (i = 0; i < kbdintctxt->nreq; i++) 273 free(prompts[i]); 274 free(prompts); 275 free(echo_on); 276 free(name); 277 free(instr); 278 return 1; 279} 280 281static void 282input_userauth_info_response(int type, u_int32_t seq, void *ctxt) 283{ 284 Authctxt *authctxt = ctxt; 285 KbdintAuthctxt *kbdintctxt; 286 int authenticated = 0, res; 287 u_int i, nresp; 288 const char *devicename = NULL; 289 char **response = NULL; 290 291 if (authctxt == NULL) 292 fatal("input_userauth_info_response: no authctxt"); 293 kbdintctxt = authctxt->kbdintctxt; 294 if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL) 295 fatal("input_userauth_info_response: no kbdintctxt"); 296 if (kbdintctxt->device == NULL) 297 fatal("input_userauth_info_response: no device"); 298 299 authctxt->postponed = 0; /* reset */ 300 nresp = packet_get_int(); 301 if (nresp != kbdintctxt->nreq) 302 fatal("input_userauth_info_response: wrong number of replies"); 303 if (nresp > 100) 304 fatal("input_userauth_info_response: too many replies"); 305 if (nresp > 0) { 306 response = xcalloc(nresp, sizeof(char *)); 307 for (i = 0; i < nresp; i++) 308 response[i] = packet_get_string(NULL); 309 } 310 packet_check_eom(); 311 312 res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response); 313 314 for (i = 0; i < nresp; i++) { 315 memset(response[i], 'r', strlen(response[i])); 316 free(response[i]); 317 } 318 free(response); 319 320 switch (res) { 321 case 0: 322 /* Success! */ 323 authenticated = authctxt->valid ? 1 : 0; 324 break; 325 case 1: 326 /* Authentication needs further interaction */ 327 if (send_userauth_info_request(authctxt) == 1) 328 authctxt->postponed = 1; 329 break; 330 default: 331 /* Failure! */ 332 break; 333 } 334 devicename = kbdintctxt->device->name; 335 if (!authctxt->postponed) { 336 if (authenticated) { 337 auth2_challenge_stop(authctxt); 338 } else { 339 /* start next device */ 340 /* may set authctxt->postponed */ 341 auth2_challenge_start(authctxt); 342 } 343 } 344 userauth_finish(authctxt, authenticated, "keyboard-interactive", 345 devicename); 346} 347 348void 349privsep_challenge_enable(void) 350{ 351#if defined(BSD_AUTH) || defined(USE_PAM) || defined(SKEY) 352 int n = 0; 353#endif 354#ifdef BSD_AUTH 355 extern KbdintDevice mm_bsdauth_device; 356#endif 357#ifdef USE_PAM 358 extern KbdintDevice mm_sshpam_device; 359#endif 360#ifdef SKEY 361 extern KbdintDevice mm_skey_device; 362#endif 363 364#ifdef BSD_AUTH 365 devices[n++] = &mm_bsdauth_device; 366#else 367#ifdef USE_PAM 368 devices[n++] = &mm_sshpam_device; 369#endif 370#ifdef SKEY 371 devices[n++] = &mm_skey_device; 372#endif 373#endif 374} 375