crypto/openssh/auth2-chall.c

   1 /* $OpenBSD: auth2-chall.c,v 1.48 2017/05/30 14:29:59 markus 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(struct ssh *);
  51 static int send_userauth_info_request(Authctxt *);
  52 static int input_userauth_info_response(int, u_int32_t, struct ssh *);
  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(struct ssh *ssh, char *devs)
 199 {
 200         Authctxt *authctxt = ssh->authctxt;
 201         debug("auth2_challenge: user=%s devs=%s",
 202             authctxt->user ? authctxt->user : "<nouser>",
 203             devs ? devs : "<no devs>");
 204
 205         if (authctxt->user == NULL || !devs)
 206                 return 0;
 207         if (authctxt->kbdintctxt == NULL)
 208                 authctxt->kbdintctxt = kbdint_alloc(devs);
 209         return auth2_challenge_start(ssh);
 210 }
 211
 212 /* unregister kbd-int callbacks and context */
 213 void
 214 auth2_challenge_stop(struct ssh *ssh)
 215 {
 216         Authctxt *authctxt = ssh->authctxt;
 217         /* unregister callback */
 218         ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL);
 219         if (authctxt->kbdintctxt != NULL) {
 220                 kbdint_free(authctxt->kbdintctxt);
 221                 authctxt->kbdintctxt = NULL;
 222         }
 223 }
 224
 225 /* side effect: sets authctxt->postponed if a reply was sent*/
 226 static int
 227 auth2_challenge_start(struct ssh *ssh)
 228 {
 229         Authctxt *authctxt = ssh->authctxt;
 230         KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt;
 231
 232         debug2("auth2_challenge_start: devices %s",
 233             kbdintctxt->devices ?  kbdintctxt->devices : "<empty>");
 234
 235         if (kbdint_next_device(authctxt, kbdintctxt) == 0) {
 236                 auth2_challenge_stop(ssh);
 237                 return 0;
 238         }
 239         debug("auth2_challenge_start: trying authentication method '%s'",
 240             kbdintctxt->device->name);
 241
 242         if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) {
 243                 auth2_challenge_stop(ssh);
 244                 return 0;
 245         }
 246         if (send_userauth_info_request(authctxt) == 0) {
 247                 auth2_challenge_stop(ssh);
 248                 return 0;
 249         }
 250         ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_INFO_RESPONSE,
 251             &input_userauth_info_response);
 252
 253         authctxt->postponed = 1;
 254         return 0;
 255 }
 256
 257 static int
 258 send_userauth_info_request(Authctxt *authctxt)
 259 {
 260         KbdintAuthctxt *kbdintctxt;
 261         char *name, *instr, **prompts;
 262         u_int i, *echo_on;
 263
 264         kbdintctxt = authctxt->kbdintctxt;
 265         if (kbdintctxt->device->query(kbdintctxt->ctxt,
 266             &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on))
 267                 return 0;
 268
 269         packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST);
 270         packet_put_cstring(name);
 271         packet_put_cstring(instr);
 272         packet_put_cstring("");         /* language not used */
 273         packet_put_int(kbdintctxt->nreq);
 274         for (i = 0; i < kbdintctxt->nreq; i++) {
 275                 packet_put_cstring(prompts[i]);
 276                 packet_put_char(echo_on[i]);
 277         }
 278         packet_send();
 279         packet_write_wait();
 280
 281         for (i = 0; i < kbdintctxt->nreq; i++)
 282                 free(prompts[i]);
 283         free(prompts);
 284         free(echo_on);
 285         free(name);
 286         free(instr);
 287         return 1;
 288 }
 289
 290 static int
 291 input_userauth_info_response(int type, u_int32_t seq, struct ssh *ssh)
 292 {
 293         Authctxt *authctxt = ssh->authctxt;
 294         KbdintAuthctxt *kbdintctxt;
 295         int authenticated = 0, res;
 296         u_int i, nresp;
 297         const char *devicename = NULL;
 298         char **response = NULL;
 299
 300         if (authctxt == NULL)
 301                 fatal("input_userauth_info_response: no authctxt");
 302         kbdintctxt = authctxt->kbdintctxt;
 303         if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL)
 304                 fatal("input_userauth_info_response: no kbdintctxt");
 305         if (kbdintctxt->device == NULL)
 306                 fatal("input_userauth_info_response: no device");
 307
 308         authctxt->postponed = 0;        /* reset */
 309         nresp = packet_get_int();
 310         if (nresp != kbdintctxt->nreq)
 311                 fatal("input_userauth_info_response: wrong number of replies");
 312         if (nresp > 100)
 313                 fatal("input_userauth_info_response: too many replies");
 314         if (nresp > 0) {
 315                 response = xcalloc(nresp, sizeof(char *));
 316                 for (i = 0; i < nresp; i++)
 317                         response[i] = packet_get_string(NULL);
 318         }
 319         packet_check_eom();
 320
 321         res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response);
 322
 323         for (i = 0; i < nresp; i++) {
 324                 explicit_bzero(response[i], strlen(response[i]));
 325                 free(response[i]);
 326         }
 327         free(response);
 328
 329         switch (res) {
 330         case 0:
 331                 /* Success! */
 332                 authenticated = authctxt->valid ? 1 : 0;
 333                 break;
 334         case 1:
 335                 /* Authentication needs further interaction */
 336                 if (send_userauth_info_request(authctxt) == 1)
 337                         authctxt->postponed = 1;
 338                 break;
 339         default:
 340                 /* Failure! */
 341                 break;
 342         }
 343         devicename = kbdintctxt->device->name;
 344         if (!authctxt->postponed) {
 345                 if (authenticated) {
 346                         auth2_challenge_stop(ssh);
 347                 } else {
 348                         /* start next device */
 349                         /* may set authctxt->postponed */
 350                         auth2_challenge_start(ssh);
 351                 }
 352         }
 353         userauth_finish(ssh, authenticated, "keyboard-interactive",
 354             devicename);
 355         return 0;
 356 }
 357
 358 void
 359 privsep_challenge_enable(void)
 360 {
 361 #if defined(BSD_AUTH) || defined(USE_PAM) || defined(SKEY)
 362         int n = 0;
 363 #endif
 364 #ifdef BSD_AUTH
 365         extern KbdintDevice mm_bsdauth_device;
 366 #endif
 367 #ifdef USE_PAM
 368         extern KbdintDevice mm_sshpam_device;
 369 #endif
 370 #ifdef SKEY
 371         extern KbdintDevice mm_skey_device;
 372 #endif
 373
 374 #ifdef BSD_AUTH
 375         devices[n++] = &mm_bsdauth_device;
 376 #else
 377 #ifdef USE_PAM
 378         devices[n++] = &mm_sshpam_device;
 379 #endif
 380 #ifdef SKEY
 381         devices[n++] = &mm_skey_device;
 382 #endif
 383 #endif
 384 }