auth2-chall.c

   1 /*
   2  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
   3  * Copyright (c) 2001 Per Allansson.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  15  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  16  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  17  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  18  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  19  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  20  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  21  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  23  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25 #include "includes.h"
  26 RCSID("$OpenBSD: auth2-chall.c,v 1.22 2005/01/19 13:11:47 dtucker Exp $");
  27
  28 #include "ssh2.h"
  29 #include "auth.h"
  30 #include "buffer.h"
  31 #include "packet.h"
  32 #include "xmalloc.h"
  33 #include "dispatch.h"
  34 #include "log.h"
  35 #include "servconf.h"
  36
  37 /* import */
  38 extern ServerOptions options;
  39
  40 static int auth2_challenge_start(Authctxt *);
  41 static int send_userauth_info_request(Authctxt *);
  42 static void input_userauth_info_response(int, u_int32_t, void *);
  43
  44 #ifdef BSD_AUTH
  45 extern KbdintDevice bsdauth_device;
  46 #else
  47 #ifdef USE_PAM
  48 extern KbdintDevice sshpam_device;
  49 #endif
  50 #ifdef SKEY
  51 extern KbdintDevice skey_device;
  52 #endif
  53 #endif
  54
  55 KbdintDevice *devices[] = {
  56 #ifdef BSD_AUTH
  57         &bsdauth_device,
  58 #else
  59 #ifdef USE_PAM
  60         &sshpam_device,
  61 #endif
  62 #ifdef SKEY
  63         &skey_device,
  64 #endif
  65 #endif
  66         NULL
  67 };
  68
  69 typedef struct KbdintAuthctxt KbdintAuthctxt;
  70 struct KbdintAuthctxt
  71 {
  72         char *devices;
  73         void *ctxt;
  74         KbdintDevice *device;
  75         u_int nreq;
  76 };
  77
  78 #ifdef USE_PAM
  79 void
  80 remove_kbdint_device(const char *devname)
  81 {
  82         int i, j;
  83
  84         for (i = 0; devices[i] != NULL; i++)
  85                 if (strcmp(devices[i]->name, devname) == 0) {
  86                         for (j = i; devices[j] != NULL; j++)
  87                                 devices[j] = devices[j+1];
  88                         i--;
  89                 }
  90 }
  91 #endif
  92
  93 static KbdintAuthctxt *
  94 kbdint_alloc(const char *devs)
  95 {
  96         KbdintAuthctxt *kbdintctxt;
  97         Buffer b;
  98         int i;
  99
 100 #ifdef USE_PAM
 101         if (!options.use_pam)
 102                 remove_kbdint_device("pam");
 103 #endif
 104
 105         kbdintctxt = xmalloc(sizeof(KbdintAuthctxt));
 106         if (strcmp(devs, "") == 0) {
 107                 buffer_init(&b);
 108                 for (i = 0; devices[i]; i++) {
 109                         if (buffer_len(&b) > 0)
 110                                 buffer_append(&b, ",", 1);
 111                         buffer_append(&b, devices[i]->name,
 112                             strlen(devices[i]->name));
 113                 }
 114                 buffer_append(&b, "\0", 1);
 115                 kbdintctxt->devices = xstrdup(buffer_ptr(&b));
 116                 buffer_free(&b);
 117         } else {
 118                 kbdintctxt->devices = xstrdup(devs);
 119         }
 120         debug("kbdint_alloc: devices '%s'", kbdintctxt->devices);
 121         kbdintctxt->ctxt = NULL;
 122         kbdintctxt->device = NULL;
 123         kbdintctxt->nreq = 0;
 124
 125         return kbdintctxt;
 126 }
 127 static void
 128 kbdint_reset_device(KbdintAuthctxt *kbdintctxt)
 129 {
 130         if (kbdintctxt->ctxt) {
 131                 kbdintctxt->device->free_ctx(kbdintctxt->ctxt);
 132                 kbdintctxt->ctxt = NULL;
 133         }
 134         kbdintctxt->device = NULL;
 135 }
 136 static void
 137 kbdint_free(KbdintAuthctxt *kbdintctxt)
 138 {
 139         if (kbdintctxt->device)
 140                 kbdint_reset_device(kbdintctxt);
 141         if (kbdintctxt->devices) {
 142                 xfree(kbdintctxt->devices);
 143                 kbdintctxt->devices = NULL;
 144         }
 145         xfree(kbdintctxt);
 146 }
 147 /* get next device */
 148 static int
 149 kbdint_next_device(KbdintAuthctxt *kbdintctxt)
 150 {
 151         size_t len;
 152         char *t;
 153         int i;
 154
 155         if (kbdintctxt->device)
 156                 kbdint_reset_device(kbdintctxt);
 157         do {
 158                 len = kbdintctxt->devices ?
 159                     strcspn(kbdintctxt->devices, ",") : 0;
 160
 161                 if (len == 0)
 162                         break;
 163                 for (i = 0; devices[i]; i++)
 164                         if (strncmp(kbdintctxt->devices, devices[i]->name, len) == 0)
 165                                 kbdintctxt->device = devices[i];
 166                 t = kbdintctxt->devices;
 167                 kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL;
 168                 xfree(t);
 169                 debug2("kbdint_next_device: devices %s", kbdintctxt->devices ?
 170                    kbdintctxt->devices : "<empty>");
 171         } while (kbdintctxt->devices && !kbdintctxt->device);
 172
 173         return kbdintctxt->device ? 1 : 0;
 174 }
 175
 176 /*
 177  * try challenge-response, set authctxt->postponed if we have to
 178  * wait for the response.
 179  */
 180 int
 181 auth2_challenge(Authctxt *authctxt, char *devs)
 182 {
 183         debug("auth2_challenge: user=%s devs=%s",
 184             authctxt->user ? authctxt->user : "<nouser>",
 185             devs ? devs : "<no devs>");
 186
 187         if (authctxt->user == NULL || !devs)
 188                 return 0;
 189         if (authctxt->kbdintctxt == NULL)
 190                 authctxt->kbdintctxt = kbdint_alloc(devs);
 191         return auth2_challenge_start(authctxt);
 192 }
 193
 194 /* unregister kbd-int callbacks and context */
 195 void
 196 auth2_challenge_stop(Authctxt *authctxt)
 197 {
 198         /* unregister callback */
 199         dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL);
 200         if (authctxt->kbdintctxt != NULL)  {
 201                 kbdint_free(authctxt->kbdintctxt);
 202                 authctxt->kbdintctxt = NULL;
 203         }
 204 }
 205
 206 /* side effect: sets authctxt->postponed if a reply was sent*/
 207 static int
 208 auth2_challenge_start(Authctxt *authctxt)
 209 {
 210         KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt;
 211
 212         debug2("auth2_challenge_start: devices %s",
 213             kbdintctxt->devices ?  kbdintctxt->devices : "<empty>");
 214
 215         if (kbdint_next_device(kbdintctxt) == 0) {
 216                 auth2_challenge_stop(authctxt);
 217                 return 0;
 218         }
 219         debug("auth2_challenge_start: trying authentication method '%s'",
 220             kbdintctxt->device->name);
 221
 222         if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) {
 223                 auth2_challenge_stop(authctxt);
 224                 return 0;
 225         }
 226         if (send_userauth_info_request(authctxt) == 0) {
 227                 auth2_challenge_stop(authctxt);
 228                 return 0;
 229         }
 230         dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE,
 231             &input_userauth_info_response);
 232
 233         authctxt->postponed = 1;
 234         return 0;
 235 }
 236
 237 static int
 238 send_userauth_info_request(Authctxt *authctxt)
 239 {
 240         KbdintAuthctxt *kbdintctxt;
 241         char *name, *instr, **prompts;
 242         int i;
 243         u_int *echo_on;
 244
 245         kbdintctxt = authctxt->kbdintctxt;
 246         if (kbdintctxt->device->query(kbdintctxt->ctxt,
 247             &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on))
 248                 return 0;
 249
 250         packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST);
 251         packet_put_cstring(name);
 252         packet_put_cstring(instr);
 253         packet_put_cstring("");         /* language not used */
 254         packet_put_int(kbdintctxt->nreq);
 255         for (i = 0; i < kbdintctxt->nreq; i++) {
 256                 packet_put_cstring(prompts[i]);
 257                 packet_put_char(echo_on[i]);
 258         }
 259         packet_send();
 260         packet_write_wait();
 261
 262         for (i = 0; i < kbdintctxt->nreq; i++)
 263                 xfree(prompts[i]);
 264         xfree(prompts);
 265         xfree(echo_on);
 266         xfree(name);
 267         xfree(instr);
 268         return 1;
 269 }
 270
 271 static void
 272 input_userauth_info_response(int type, u_int32_t seq, void *ctxt)
 273 {
 274         Authctxt *authctxt = ctxt;
 275         KbdintAuthctxt *kbdintctxt;
 276         int i, authenticated = 0, res, len;
 277         u_int nresp;
 278         char **response = NULL, *method;
 279
 280         if (authctxt == NULL)
 281                 fatal("input_userauth_info_response: no authctxt");
 282         kbdintctxt = authctxt->kbdintctxt;
 283         if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL)
 284                 fatal("input_userauth_info_response: no kbdintctxt");
 285         if (kbdintctxt->device == NULL)
 286                 fatal("input_userauth_info_response: no device");
 287
 288         authctxt->postponed = 0;        /* reset */
 289         nresp = packet_get_int();
 290         if (nresp != kbdintctxt->nreq)
 291                 fatal("input_userauth_info_response: wrong number of replies");
 292         if (nresp > 100)
 293                 fatal("input_userauth_info_response: too many replies");
 294         if (nresp > 0) {
 295                 response = xmalloc(nresp * sizeof(char *));
 296                 for (i = 0; i < nresp; i++)
 297                         response[i] = packet_get_string(NULL);
 298         }
 299         packet_check_eom();
 300
 301         res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response);
 302
 303         for (i = 0; i < nresp; i++) {
 304                 memset(response[i], 'r', strlen(response[i]));
 305                 xfree(response[i]);
 306         }
 307         if (response)
 308                 xfree(response);
 309
 310         switch (res) {
 311         case 0:
 312                 /* Success! */
 313                 authenticated = authctxt->valid ? 1 : 0;
 314                 break;
 315         case 1:
 316                 /* Authentication needs further interaction */
 317                 if (send_userauth_info_request(authctxt) == 1)
 318                         authctxt->postponed = 1;
 319                 break;
 320         default:
 321                 /* Failure! */
 322                 break;
 323         }
 324
 325         len = strlen("keyboard-interactive") + 2 +
 326                 strlen(kbdintctxt->device->name);
 327         method = xmalloc(len);
 328         snprintf(method, len, "keyboard-interactive/%s",
 329             kbdintctxt->device->name);
 330
 331         if (!authctxt->postponed) {
 332                 if (authenticated) {
 333                         auth2_challenge_stop(authctxt);
 334                 } else {
 335                         /* start next device */
 336                         /* may set authctxt->postponed */
 337                         auth2_challenge_start(authctxt);
 338                 }
 339         }
 340         userauth_finish(authctxt, authenticated, method);
 341         xfree(method);
 342 }
 343
 344 void
 345 privsep_challenge_enable(void)
 346 {
 347 #if defined(BSD_AUTH) || defined(USE_PAM) || defined(SKEY)
 348         int n = 0;
 349 #endif
 350 #ifdef BSD_AUTH
 351         extern KbdintDevice mm_bsdauth_device;
 352 #endif
 353 #ifdef USE_PAM
 354         extern KbdintDevice mm_sshpam_device;
 355 #endif
 356 #ifdef SKEY
 357         extern KbdintDevice mm_skey_device;
 358 #endif
 359
 360 #ifdef BSD_AUTH
 361         devices[n++] = &mm_bsdauth_device;
 362 #else
 363 #ifdef USE_PAM
 364         devices[n++] = &mm_sshpam_device;
 365 #endif
 366 #ifdef SKEY
 367         devices[n++] = &mm_skey_device;
 368 #endif
 369 #endif
 370 }