auth2-chall.c

   1 /* $OpenBSD: auth2-chall.c,v 1.33 2007/09/21 08:15:29 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 */
  47 extern ServerOptions options;
  48
  49 static int auth2_challenge_start(Authctxt *);
  50 static int send_userauth_info_request(Authctxt *);
  51 static void input_userauth_info_response(int, u_int32_t, void *);
  52
  53 #ifdef BSD_AUTH
  54 extern KbdintDevice bsdauth_device;
  55 #else
  56 #ifdef USE_PAM
  57 extern KbdintDevice sshpam_device;
  58 #endif
  59 #ifdef SKEY
  60 extern KbdintDevice skey_device;
  61 #endif
  62 #endif
  63
  64 KbdintDevice *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
  78 typedef struct KbdintAuthctxt KbdintAuthctxt;
  79 struct KbdintAuthctxt
  80 {
  81         char *devices;
  82         void *ctxt;
  83         KbdintDevice *device;
  84         u_int nreq;
  85 };
  86
  87 #ifdef USE_PAM
  88 void
  89 remove_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
 102 static KbdintAuthctxt *
 103 kbdint_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 }
 136 static void
 137 kbdint_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 }
 145 static void
 146 kbdint_free(KbdintAuthctxt *kbdintctxt)
 147 {
 148         if (kbdintctxt->device)
 149                 kbdint_reset_device(kbdintctxt);
 150         if (kbdintctxt->devices) {
 151                 xfree(kbdintctxt->devices);
 152                 kbdintctxt->devices = NULL;
 153         }
 154         xfree(kbdintctxt);
 155 }
 156 /* get next device */
 157 static int
 158 kbdint_next_device(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 (strncmp(kbdintctxt->devices, devices[i]->name, len) == 0)
 174                                 kbdintctxt->device = devices[i];
 175                 t = kbdintctxt->devices;
 176                 kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL;
 177                 xfree(t);
 178                 debug2("kbdint_next_device: devices %s", kbdintctxt->devices ?
 179                     kbdintctxt->devices : "<empty>");
 180         } while (kbdintctxt->devices && !kbdintctxt->device);
 181
 182         return kbdintctxt->device ? 1 : 0;
 183 }
 184
 185 /*
 186  * try challenge-response, set authctxt->postponed if we have to
 187  * wait for the response.
 188  */
 189 int
 190 auth2_challenge(Authctxt *authctxt, char *devs)
 191 {
 192         debug("auth2_challenge: user=%s devs=%s",
 193             authctxt->user ? authctxt->user : "<nouser>",
 194             devs ? devs : "<no devs>");
 195
 196         if (authctxt->user == NULL || !devs)
 197                 return 0;
 198         if (authctxt->kbdintctxt == NULL)
 199                 authctxt->kbdintctxt = kbdint_alloc(devs);
 200         return auth2_challenge_start(authctxt);
 201 }
 202
 203 /* unregister kbd-int callbacks and context */
 204 void
 205 auth2_challenge_stop(Authctxt *authctxt)
 206 {
 207         /* unregister callback */
 208         dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL);
 209         if (authctxt->kbdintctxt != NULL) {
 210                 kbdint_free(authctxt->kbdintctxt);
 211                 authctxt->kbdintctxt = NULL;
 212         }
 213 }
 214
 215 /* side effect: sets authctxt->postponed if a reply was sent*/
 216 static int
 217 auth2_challenge_start(Authctxt *authctxt)
 218 {
 219         KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt;
 220
 221         debug2("auth2_challenge_start: devices %s",
 222             kbdintctxt->devices ?  kbdintctxt->devices : "<empty>");
 223
 224         if (kbdint_next_device(kbdintctxt) == 0) {
 225                 auth2_challenge_stop(authctxt);
 226                 return 0;
 227         }
 228         debug("auth2_challenge_start: trying authentication method '%s'",
 229             kbdintctxt->device->name);
 230
 231         if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) {
 232                 auth2_challenge_stop(authctxt);
 233                 return 0;
 234         }
 235         if (send_userauth_info_request(authctxt) == 0) {
 236                 auth2_challenge_stop(authctxt);
 237                 return 0;
 238         }
 239         dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE,
 240             &input_userauth_info_response);
 241
 242         authctxt->postponed = 1;
 243         return 0;
 244 }
 245
 246 static int
 247 send_userauth_info_request(Authctxt *authctxt)
 248 {
 249         KbdintAuthctxt *kbdintctxt;
 250         char *name, *instr, **prompts;
 251         u_int i, *echo_on;
 252
 253         kbdintctxt = authctxt->kbdintctxt;
 254         if (kbdintctxt->device->query(kbdintctxt->ctxt,
 255             &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on))
 256                 return 0;
 257
 258         packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST);
 259         packet_put_cstring(name);
 260         packet_put_cstring(instr);
 261         packet_put_cstring("");         /* language not used */
 262         packet_put_int(kbdintctxt->nreq);
 263         for (i = 0; i < kbdintctxt->nreq; i++) {
 264                 packet_put_cstring(prompts[i]);
 265                 packet_put_char(echo_on[i]);
 266         }
 267         packet_send();
 268         packet_write_wait();
 269
 270         for (i = 0; i < kbdintctxt->nreq; i++)
 271                 xfree(prompts[i]);
 272         xfree(prompts);
 273         xfree(echo_on);
 274         xfree(name);
 275         xfree(instr);
 276         return 1;
 277 }
 278
 279 static void
 280 input_userauth_info_response(int type, u_int32_t seq, void *ctxt)
 281 {
 282         Authctxt *authctxt = ctxt;
 283         KbdintAuthctxt *kbdintctxt;
 284         int authenticated = 0, res, len;
 285         u_int i, nresp;
 286         char **response = NULL, *method;
 287
 288         if (authctxt == NULL)
 289                 fatal("input_userauth_info_response: no authctxt");
 290         kbdintctxt = authctxt->kbdintctxt;
 291         if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL)
 292                 fatal("input_userauth_info_response: no kbdintctxt");
 293         if (kbdintctxt->device == NULL)
 294                 fatal("input_userauth_info_response: no device");
 295
 296         authctxt->postponed = 0;        /* reset */
 297         nresp = packet_get_int();
 298         if (nresp != kbdintctxt->nreq)
 299                 fatal("input_userauth_info_response: wrong number of replies");
 300         if (nresp > 100)
 301                 fatal("input_userauth_info_response: too many replies");
 302         if (nresp > 0) {
 303                 response = xcalloc(nresp, sizeof(char *));
 304                 for (i = 0; i < nresp; i++)
 305                         response[i] = packet_get_string(NULL);
 306         }
 307         packet_check_eom();
 308
 309         res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response);
 310
 311         for (i = 0; i < nresp; i++) {
 312                 memset(response[i], 'r', strlen(response[i]));
 313                 xfree(response[i]);
 314         }
 315         if (response)
 316                 xfree(response);
 317
 318         switch (res) {
 319         case 0:
 320                 /* Success! */
 321                 authenticated = authctxt->valid ? 1 : 0;
 322                 break;
 323         case 1:
 324                 /* Authentication needs further interaction */
 325                 if (send_userauth_info_request(authctxt) == 1)
 326                         authctxt->postponed = 1;
 327                 break;
 328         default:
 329                 /* Failure! */
 330                 break;
 331         }
 332
 333         len = strlen("keyboard-interactive") + 2 +
 334                 strlen(kbdintctxt->device->name);
 335         method = xmalloc(len);
 336         snprintf(method, len, "keyboard-interactive/%s",
 337             kbdintctxt->device->name);
 338
 339         if (!authctxt->postponed) {
 340                 if (authenticated) {
 341                         auth2_challenge_stop(authctxt);
 342                 } else {
 343                         /* start next device */
 344                         /* may set authctxt->postponed */
 345                         auth2_challenge_start(authctxt);
 346                 }
 347         }
 348         userauth_finish(authctxt, authenticated, method);
 349         xfree(method);
 350 }
 351
 352 void
 353 privsep_challenge_enable(void)
 354 {
 355 #if defined(BSD_AUTH) || defined(USE_PAM) || defined(SKEY)
 356         int n = 0;
 357 #endif
 358 #ifdef BSD_AUTH
 359         extern KbdintDevice mm_bsdauth_device;
 360 #endif
 361 #ifdef USE_PAM
 362         extern KbdintDevice mm_sshpam_device;
 363 #endif
 364 #ifdef SKEY
 365         extern KbdintDevice mm_skey_device;
 366 #endif
 367
 368 #ifdef BSD_AUTH
 369         devices[n++] = &mm_bsdauth_device;
 370 #else
 371 #ifdef USE_PAM
 372         devices[n++] = &mm_sshpam_device;
 373 #endif
 374 #ifdef SKEY
 375         devices[n++] = &mm_skey_device;
 376 #endif
 377 #endif
 378 }