crypto/openssh/auth2-chall.c

   1 /* $OpenBSD: auth2-chall.c,v 1.44 2016/05/02 08:49:03 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 int 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         u_int devices_done;
  87 };
  88
  89 #ifdef USE_PAM
  90 void
  91 remove_kbdint_device(const char *devname)
  92 {
  93         int i, j;
  94
  95         for (i = 0; devices[i] != NULL; i++)
  96                 if (strcmp(devices[i]->name, devname) == 0) {
  97                         for (j = i; devices[j] != NULL; j++)
  98                                 devices[j] = devices[j+1];
  99                         i--;
 100                 }
 101 }
 102 #endif
 103
 104 static KbdintAuthctxt *
 105 kbdint_alloc(const char *devs)
 106 {
 107         KbdintAuthctxt *kbdintctxt;
 108         Buffer b;
 109         int i;
 110
 111 #ifdef USE_PAM
 112         if (!options.use_pam)
 113                 remove_kbdint_device("pam");
 114 #endif
 115
 116         kbdintctxt = xcalloc(1, sizeof(KbdintAuthctxt));
 117         if (strcmp(devs, "") == 0) {
 118                 buffer_init(&b);
 119                 for (i = 0; devices[i]; i++) {
 120                         if (buffer_len(&b) > 0)
 121                                 buffer_append(&b, ",", 1);
 122                         buffer_append(&b, devices[i]->name,
 123                             strlen(devices[i]->name));
 124                 }
 125                 if ((kbdintctxt->devices = sshbuf_dup_string(&b)) == NULL)
 126                         fatal("%s: sshbuf_dup_string failed", __func__);
 127                 buffer_free(&b);
 128         } else {
 129                 kbdintctxt->devices = xstrdup(devs);
 130         }
 131         debug("kbdint_alloc: devices '%s'", kbdintctxt->devices);
 132         kbdintctxt->ctxt = NULL;
 133         kbdintctxt->device = NULL;
 134         kbdintctxt->nreq = 0;
 135
 136         return kbdintctxt;
 137 }
 138 static void
 139 kbdint_reset_device(KbdintAuthctxt *kbdintctxt)
 140 {
 141         if (kbdintctxt->ctxt) {
 142                 kbdintctxt->device->free_ctx(kbdintctxt->ctxt);
 143                 kbdintctxt->ctxt = NULL;
 144         }
 145         kbdintctxt->device = NULL;
 146 }
 147 static void
 148 kbdint_free(KbdintAuthctxt *kbdintctxt)
 149 {
 150         if (kbdintctxt->device)
 151                 kbdint_reset_device(kbdintctxt);
 152         free(kbdintctxt->devices);
 153         explicit_bzero(kbdintctxt, sizeof(*kbdintctxt));
 154         free(kbdintctxt);
 155 }
 156 /* get next device */
 157 static int
 158 kbdint_next_device(Authctxt *authctxt, KbdintAuthctxt *kbdintctxt)
 159 {
 160         size_t len;
 161         char *t;
 162         int i;
 163
 164         if (kbdintctxt->device)
 165                 kbdint_reset_device(kbdintctxt);
 166         do {
 167                 len = kbdintctxt->devices ?
 168                     strcspn(kbdintctxt->devices, ",") : 0;
 169
 170                 if (len == 0)
 171                         break;
 172                 for (i = 0; devices[i]; i++) {
 173                         if ((kbdintctxt->devices_done & (1 << i)) != 0 ||
 174                             !auth2_method_allowed(authctxt,
 175                             "keyboard-interactive", devices[i]->name))
 176                                 continue;
 177                         if (strncmp(kbdintctxt->devices, devices[i]->name,
 178                             len) == 0) {
 179                                 kbdintctxt->device = devices[i];
 180                                 kbdintctxt->devices_done |= 1 << i;
 181                         }
 182                 }
 183                 t = kbdintctxt->devices;
 184                 kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL;
 185                 free(t);
 186                 debug2("kbdint_next_device: devices %s", kbdintctxt->devices ?
 187                     kbdintctxt->devices : "<empty>");
 188         } while (kbdintctxt->devices && !kbdintctxt->device);
 189
 190         return kbdintctxt->device ? 1 : 0;
 191 }
 192
 193 /*
 194  * try challenge-response, set authctxt->postponed if we have to
 195  * wait for the response.
 196  */
 197 int
 198 auth2_challenge(Authctxt *authctxt, char *devs)
 199 {
 200         debug("auth2_challenge: user=%s devs=%s",
 201             authctxt->user ? authctxt->user : "<nouser>",
 202             devs ? devs : "<no devs>");
 203
 204         if (authctxt->user == NULL || !devs)
 205                 return 0;
 206         if (authctxt->kbdintctxt == NULL)
 207                 authctxt->kbdintctxt = kbdint_alloc(devs);
 208         return auth2_challenge_start(authctxt);
 209 }
 210
 211 /* unregister kbd-int callbacks and context */
 212 void
 213 auth2_challenge_stop(Authctxt *authctxt)
 214 {
 215         /* unregister callback */
 216         dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL);
 217         if (authctxt->kbdintctxt != NULL) {
 218                 kbdint_free(authctxt->kbdintctxt);
 219                 authctxt->kbdintctxt = NULL;
 220         }
 221 }
 222
 223 /* side effect: sets authctxt->postponed if a reply was sent*/
 224 static int
 225 auth2_challenge_start(Authctxt *authctxt)
 226 {
 227         KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt;
 228
 229         debug2("auth2_challenge_start: devices %s",
 230             kbdintctxt->devices ?  kbdintctxt->devices : "<empty>");
 231
 232         if (kbdint_next_device(authctxt, kbdintctxt) == 0) {
 233                 auth2_challenge_stop(authctxt);
 234                 return 0;
 235         }
 236         debug("auth2_challenge_start: trying authentication method '%s'",
 237             kbdintctxt->device->name);
 238
 239         if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) {
 240                 auth2_challenge_stop(authctxt);
 241                 return 0;
 242         }
 243         if (send_userauth_info_request(authctxt) == 0) {
 244                 auth2_challenge_stop(authctxt);
 245                 return 0;
 246         }
 247         dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE,
 248             &input_userauth_info_response);
 249
 250         authctxt->postponed = 1;
 251         return 0;
 252 }
 253
 254 static int
 255 send_userauth_info_request(Authctxt *authctxt)
 256 {
 257         KbdintAuthctxt *kbdintctxt;
 258         char *name, *instr, **prompts;
 259         u_int i, *echo_on;
 260
 261         kbdintctxt = authctxt->kbdintctxt;
 262         if (kbdintctxt->device->query(kbdintctxt->ctxt,
 263             &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on))
 264                 return 0;
 265
 266         packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST);
 267         packet_put_cstring(name);
 268         packet_put_cstring(instr);
 269         packet_put_cstring("");         /* language not used */
 270         packet_put_int(kbdintctxt->nreq);
 271         for (i = 0; i < kbdintctxt->nreq; i++) {
 272                 packet_put_cstring(prompts[i]);
 273                 packet_put_char(echo_on[i]);
 274         }
 275         packet_send();
 276         packet_write_wait();
 277
 278         for (i = 0; i < kbdintctxt->nreq; i++)
 279                 free(prompts[i]);
 280         free(prompts);
 281         free(echo_on);
 282         free(name);
 283         free(instr);
 284         return 1;
 285 }
 286
 287 static int
 288 input_userauth_info_response(int type, u_int32_t seq, void *ctxt)
 289 {
 290         Authctxt *authctxt = ctxt;
 291         KbdintAuthctxt *kbdintctxt;
 292         int authenticated = 0, res;
 293         u_int i, nresp;
 294         const char *devicename = NULL;
 295         char **response = NULL;
 296
 297         if (authctxt == NULL)
 298                 fatal("input_userauth_info_response: no authctxt");
 299         kbdintctxt = authctxt->kbdintctxt;
 300         if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL)
 301                 fatal("input_userauth_info_response: no kbdintctxt");
 302         if (kbdintctxt->device == NULL)
 303                 fatal("input_userauth_info_response: no device");
 304
 305         authctxt->postponed = 0;        /* reset */
 306         nresp = packet_get_int();
 307         if (nresp != kbdintctxt->nreq)
 308                 fatal("input_userauth_info_response: wrong number of replies");
 309         if (nresp > 100)
 310                 fatal("input_userauth_info_response: too many replies");
 311         if (nresp > 0) {
 312                 response = xcalloc(nresp, sizeof(char *));
 313                 for (i = 0; i < nresp; i++)
 314                         response[i] = packet_get_string(NULL);
 315         }
 316         packet_check_eom();
 317
 318         res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response);
 319
 320         for (i = 0; i < nresp; i++) {
 321                 explicit_bzero(response[i], strlen(response[i]));
 322                 free(response[i]);
 323         }
 324         free(response);
 325
 326         switch (res) {
 327         case 0:
 328                 /* Success! */
 329                 authenticated = authctxt->valid ? 1 : 0;
 330                 break;
 331         case 1:
 332                 /* Authentication needs further interaction */
 333                 if (send_userauth_info_request(authctxt) == 1)
 334                         authctxt->postponed = 1;
 335                 break;
 336         default:
 337                 /* Failure! */
 338                 break;
 339         }
 340         devicename = kbdintctxt->device->name;
 341         if (!authctxt->postponed) {
 342                 if (authenticated) {
 343                         auth2_challenge_stop(authctxt);
 344                 } else {
 345                         /* start next device */
 346                         /* may set authctxt->postponed */
 347                         auth2_challenge_start(authctxt);
 348                 }
 349         }
 350         userauth_finish(authctxt, authenticated, "keyboard-interactive",
 351             devicename);
 352         return 0;
 353 }
 354
 355 void
 356 privsep_challenge_enable(void)
 357 {
 358 #if defined(BSD_AUTH) || defined(USE_PAM) || defined(SKEY)
 359         int n = 0;
 360 #endif
 361 #ifdef BSD_AUTH
 362         extern KbdintDevice mm_bsdauth_device;
 363 #endif
 364 #ifdef USE_PAM
 365         extern KbdintDevice mm_sshpam_device;
 366 #endif
 367 #ifdef SKEY
 368         extern KbdintDevice mm_skey_device;
 369 #endif
 370
 371 #ifdef BSD_AUTH
 372         devices[n++] = &mm_bsdauth_device;
 373 #else
 374 #ifdef USE_PAM
 375         devices[n++] = &mm_sshpam_device;
 376 #endif
 377 #ifdef SKEY
 378         devices[n++] = &mm_skey_device;
 379 #endif
 380 #endif
 381 }