crypto/openssh/auth2-chall.c

   1 /* $OpenBSD: auth2-chall.c,v 1.41 2014/02/02 03:44:31 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 "misc.h"
  45 #include "servconf.h"
  46
  47 /* import */
  48 extern ServerOptions options;
  49
  50 static int auth2_challenge_start(Authctxt *);
  51 static int send_userauth_info_request(Authctxt *);
  52 static void input_userauth_info_response(int, u_int32_t, void *);
  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 };
  87
  88 #ifdef USE_PAM
  89 void
  90 remove_kbdint_device(const char *devname)
  91 {
  92         int i, j;
  93
  94         for (i = 0; devices[i] != NULL; i++)
  95                 if (strcmp(devices[i]->name, devname) == 0) {
  96                         for (j = i; devices[j] != NULL; j++)
  97                                 devices[j] = devices[j+1];
  98                         i--;
  99                 }
 100 }
 101 #endif
 102
 103 static KbdintAuthctxt *
 104 kbdint_alloc(const char *devs)
 105 {
 106         KbdintAuthctxt *kbdintctxt;
 107         Buffer b;
 108         int i;
 109
 110 #ifdef USE_PAM
 111         if (!options.use_pam)
 112                 remove_kbdint_device("pam");
 113 #endif
 114
 115         kbdintctxt = xcalloc(1, sizeof(KbdintAuthctxt));
 116         if (strcmp(devs, "") == 0) {
 117                 buffer_init(&b);
 118                 for (i = 0; devices[i]; i++) {
 119                         if (buffer_len(&b) > 0)
 120                                 buffer_append(&b, ",", 1);
 121                         buffer_append(&b, devices[i]->name,
 122                             strlen(devices[i]->name));
 123                 }
 124                 buffer_append(&b, "\0", 1);
 125                 kbdintctxt->devices = xstrdup(buffer_ptr(&b));
 126                 buffer_free(&b);
 127         } else {
 128                 kbdintctxt->devices = xstrdup(devs);
 129         }
 130         debug("kbdint_alloc: devices '%s'", kbdintctxt->devices);
 131         kbdintctxt->ctxt = NULL;
 132         kbdintctxt->device = NULL;
 133         kbdintctxt->nreq = 0;
 134
 135         return kbdintctxt;
 136 }
 137 static void
 138 kbdint_reset_device(KbdintAuthctxt *kbdintctxt)
 139 {
 140         if (kbdintctxt->ctxt) {
 141                 kbdintctxt->device->free_ctx(kbdintctxt->ctxt);
 142                 kbdintctxt->ctxt = NULL;
 143         }
 144         kbdintctxt->device = NULL;
 145 }
 146 static void
 147 kbdint_free(KbdintAuthctxt *kbdintctxt)
 148 {
 149         if (kbdintctxt->device)
 150                 kbdint_reset_device(kbdintctxt);
 151         free(kbdintctxt->devices);
 152         explicit_bzero(kbdintctxt, sizeof(*kbdintctxt));
 153         free(kbdintctxt);
 154 }
 155 /* get next device */
 156 static int
 157 kbdint_next_device(Authctxt *authctxt, KbdintAuthctxt *kbdintctxt)
 158 {
 159         size_t len;
 160         char *t;
 161         int i;
 162
 163         if (kbdintctxt->device)
 164                 kbdint_reset_device(kbdintctxt);
 165         do {
 166                 len = kbdintctxt->devices ?
 167                     strcspn(kbdintctxt->devices, ",") : 0;
 168
 169                 if (len == 0)
 170                         break;
 171                 for (i = 0; devices[i]; i++) {
 172                         if (!auth2_method_allowed(authctxt,
 173                             "keyboard-interactive", devices[i]->name))
 174                                 continue;
 175                         if (strncmp(kbdintctxt->devices, devices[i]->name, len) == 0)
 176                                 kbdintctxt->device = devices[i];
 177                 }
 178                 t = kbdintctxt->devices;
 179                 kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL;
 180                 free(t);
 181                 debug2("kbdint_next_device: devices %s", kbdintctxt->devices ?
 182                     kbdintctxt->devices : "<empty>");
 183         } while (kbdintctxt->devices && !kbdintctxt->device);
 184
 185         return kbdintctxt->device ? 1 : 0;
 186 }
 187
 188 /*
 189  * try challenge-response, set authctxt->postponed if we have to
 190  * wait for the response.
 191  */
 192 int
 193 auth2_challenge(Authctxt *authctxt, char *devs)
 194 {
 195         debug("auth2_challenge: user=%s devs=%s",
 196             authctxt->user ? authctxt->user : "<nouser>",
 197             devs ? devs : "<no devs>");
 198
 199         if (authctxt->user == NULL || !devs)
 200                 return 0;
 201         if (authctxt->kbdintctxt == NULL)
 202                 authctxt->kbdintctxt = kbdint_alloc(devs);
 203         return auth2_challenge_start(authctxt);
 204 }
 205
 206 /* unregister kbd-int callbacks and context */
 207 void
 208 auth2_challenge_stop(Authctxt *authctxt)
 209 {
 210         /* unregister callback */
 211         dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL);
 212         if (authctxt->kbdintctxt != NULL) {
 213                 kbdint_free(authctxt->kbdintctxt);
 214                 authctxt->kbdintctxt = NULL;
 215         }
 216 }
 217
 218 /* side effect: sets authctxt->postponed if a reply was sent*/
 219 static int
 220 auth2_challenge_start(Authctxt *authctxt)
 221 {
 222         KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt;
 223
 224         debug2("auth2_challenge_start: devices %s",
 225             kbdintctxt->devices ?  kbdintctxt->devices : "<empty>");
 226
 227         if (kbdint_next_device(authctxt, kbdintctxt) == 0) {
 228                 auth2_challenge_stop(authctxt);
 229                 return 0;
 230         }
 231         debug("auth2_challenge_start: trying authentication method '%s'",
 232             kbdintctxt->device->name);
 233
 234         if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) {
 235                 auth2_challenge_stop(authctxt);
 236                 return 0;
 237         }
 238         if (send_userauth_info_request(authctxt) == 0) {
 239                 auth2_challenge_stop(authctxt);
 240                 return 0;
 241         }
 242         dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE,
 243             &input_userauth_info_response);
 244
 245         authctxt->postponed = 1;
 246         return 0;
 247 }
 248
 249 static int
 250 send_userauth_info_request(Authctxt *authctxt)
 251 {
 252         KbdintAuthctxt *kbdintctxt;
 253         char *name, *instr, **prompts;
 254         u_int i, *echo_on;
 255
 256         kbdintctxt = authctxt->kbdintctxt;
 257         if (kbdintctxt->device->query(kbdintctxt->ctxt,
 258             &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on))
 259                 return 0;
 260
 261         packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST);
 262         packet_put_cstring(name);
 263         packet_put_cstring(instr);
 264         packet_put_cstring("");         /* language not used */
 265         packet_put_int(kbdintctxt->nreq);
 266         for (i = 0; i < kbdintctxt->nreq; i++) {
 267                 packet_put_cstring(prompts[i]);
 268                 packet_put_char(echo_on[i]);
 269         }
 270         packet_send();
 271         packet_write_wait();
 272
 273         for (i = 0; i < kbdintctxt->nreq; i++)
 274                 free(prompts[i]);
 275         free(prompts);
 276         free(echo_on);
 277         free(name);
 278         free(instr);
 279         return 1;
 280 }
 281
 282 static void
 283 input_userauth_info_response(int type, u_int32_t seq, void *ctxt)
 284 {
 285         Authctxt *authctxt = ctxt;
 286         KbdintAuthctxt *kbdintctxt;
 287         int authenticated = 0, res;
 288         u_int i, nresp;
 289         const char *devicename = NULL;
 290         char **response = NULL;
 291
 292         if (authctxt == NULL)
 293                 fatal("input_userauth_info_response: no authctxt");
 294         kbdintctxt = authctxt->kbdintctxt;
 295         if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL)
 296                 fatal("input_userauth_info_response: no kbdintctxt");
 297         if (kbdintctxt->device == NULL)
 298                 fatal("input_userauth_info_response: no device");
 299
 300         authctxt->postponed = 0;        /* reset */
 301         nresp = packet_get_int();
 302         if (nresp != kbdintctxt->nreq)
 303                 fatal("input_userauth_info_response: wrong number of replies");
 304         if (nresp > 100)
 305                 fatal("input_userauth_info_response: too many replies");
 306         if (nresp > 0) {
 307                 response = xcalloc(nresp, sizeof(char *));
 308                 for (i = 0; i < nresp; i++)
 309                         response[i] = packet_get_string(NULL);
 310         }
 311         packet_check_eom();
 312
 313         res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response);
 314
 315         for (i = 0; i < nresp; i++) {
 316                 explicit_bzero(response[i], strlen(response[i]));
 317                 free(response[i]);
 318         }
 319         free(response);
 320
 321         switch (res) {
 322         case 0:
 323                 /* Success! */
 324                 authenticated = authctxt->valid ? 1 : 0;
 325                 break;
 326         case 1:
 327                 /* Authentication needs further interaction */
 328                 if (send_userauth_info_request(authctxt) == 1)
 329                         authctxt->postponed = 1;
 330                 break;
 331         default:
 332                 /* Failure! */
 333                 break;
 334         }
 335         devicename = kbdintctxt->device->name;
 336         if (!authctxt->postponed) {
 337                 if (authenticated) {
 338                         auth2_challenge_stop(authctxt);
 339                 } else {
 340                         /* start next device */
 341                         /* may set authctxt->postponed */
 342                         auth2_challenge_start(authctxt);
 343                 }
 344         }
 345         userauth_finish(authctxt, authenticated, "keyboard-interactive",
 346             devicename);
 347 }
 348
 349 void
 350 privsep_challenge_enable(void)
 351 {
 352 #if defined(BSD_AUTH) || defined(USE_PAM) || defined(SKEY)
 353         int n = 0;
 354 #endif
 355 #ifdef BSD_AUTH
 356         extern KbdintDevice mm_bsdauth_device;
 357 #endif
 358 #ifdef USE_PAM
 359         extern KbdintDevice mm_sshpam_device;
 360 #endif
 361 #ifdef SKEY
 362         extern KbdintDevice mm_skey_device;
 363 #endif
 364
 365 #ifdef BSD_AUTH
 366         devices[n++] = &mm_bsdauth_device;
 367 #else
 368 #ifdef USE_PAM
 369         devices[n++] = &mm_sshpam_device;
 370 #endif
 371 #ifdef SKEY
 372         devices[n++] = &mm_skey_device;
 373 #endif
 374 #endif
 375 }