auth2-chall.c

   1 /* $OpenBSD: auth2-chall.c,v 1.28 2006/07/22 20:48:22 stevesk 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 #include "includes.h"
  27
  28 #include <string.h>
  29
  30 #include "ssh2.h"
  31 #include "auth.h"
  32 #include "buffer.h"
  33 #include "packet.h"
  34 #include "xmalloc.h"
  35 #include "dispatch.h"
  36 #include "log.h"
  37 #include "servconf.h"
  38
  39 /* import */
  40 extern ServerOptions options;
  41
  42 static int auth2_challenge_start(Authctxt *);
  43 static int send_userauth_info_request(Authctxt *);
  44 static void input_userauth_info_response(int, u_int32_t, void *);
  45
  46 #ifdef BSD_AUTH
  47 extern KbdintDevice bsdauth_device;
  48 #else
  49 #ifdef USE_PAM
  50 extern KbdintDevice sshpam_device;
  51 #endif
  52 #ifdef SKEY
  53 extern KbdintDevice skey_device;
  54 #endif
  55 #endif
  56
  57 KbdintDevice *devices[] = {
  58 #ifdef BSD_AUTH
  59         &bsdauth_device,
  60 #else
  61 #ifdef USE_PAM
  62         &sshpam_device,
  63 #endif
  64 #ifdef SKEY
  65         &skey_device,
  66 #endif
  67 #endif
  68         NULL
  69 };
  70
  71 typedef struct KbdintAuthctxt KbdintAuthctxt;
  72 struct KbdintAuthctxt
  73 {
  74         char *devices;
  75         void *ctxt;
  76         KbdintDevice *device;
  77         u_int nreq;
  78 };
  79
  80 #ifdef USE_PAM
  81 void
  82 remove_kbdint_device(const char *devname)
  83 {
  84         int i, j;
  85
  86         for (i = 0; devices[i] != NULL; i++)
  87                 if (strcmp(devices[i]->name, devname) == 0) {
  88                         for (j = i; devices[j] != NULL; j++)
  89                                 devices[j] = devices[j+1];
  90                         i--;
  91                 }
  92 }
  93 #endif
  94
  95 static KbdintAuthctxt *
  96 kbdint_alloc(const char *devs)
  97 {
  98         KbdintAuthctxt *kbdintctxt;
  99         Buffer b;
 100         int i;
 101
 102 #ifdef USE_PAM
 103         if (!options.use_pam)
 104                 remove_kbdint_device("pam");
 105 #endif
 106
 107         kbdintctxt = xmalloc(sizeof(KbdintAuthctxt));
 108         if (strcmp(devs, "") == 0) {
 109                 buffer_init(&b);
 110                 for (i = 0; devices[i]; i++) {
 111                         if (buffer_len(&b) > 0)
 112                                 buffer_append(&b, ",", 1);
 113                         buffer_append(&b, devices[i]->name,
 114                             strlen(devices[i]->name));
 115                 }
 116                 buffer_append(&b, "\0", 1);
 117                 kbdintctxt->devices = xstrdup(buffer_ptr(&b));
 118                 buffer_free(&b);
 119         } else {
 120                 kbdintctxt->devices = xstrdup(devs);
 121         }
 122         debug("kbdint_alloc: devices '%s'", kbdintctxt->devices);
 123         kbdintctxt->ctxt = NULL;
 124         kbdintctxt->device = NULL;
 125         kbdintctxt->nreq = 0;
 126
 127         return kbdintctxt;
 128 }
 129 static void
 130 kbdint_reset_device(KbdintAuthctxt *kbdintctxt)
 131 {
 132         if (kbdintctxt->ctxt) {
 133                 kbdintctxt->device->free_ctx(kbdintctxt->ctxt);
 134                 kbdintctxt->ctxt = NULL;
 135         }
 136         kbdintctxt->device = NULL;
 137 }
 138 static void
 139 kbdint_free(KbdintAuthctxt *kbdintctxt)
 140 {
 141         if (kbdintctxt->device)
 142                 kbdint_reset_device(kbdintctxt);
 143         if (kbdintctxt->devices) {
 144                 xfree(kbdintctxt->devices);
 145                 kbdintctxt->devices = NULL;
 146         }
 147         xfree(kbdintctxt);
 148 }
 149 /* get next device */
 150 static int
 151 kbdint_next_device(KbdintAuthctxt *kbdintctxt)
 152 {
 153         size_t len;
 154         char *t;
 155         int i;
 156
 157         if (kbdintctxt->device)
 158                 kbdint_reset_device(kbdintctxt);
 159         do {
 160                 len = kbdintctxt->devices ?
 161                     strcspn(kbdintctxt->devices, ",") : 0;
 162
 163                 if (len == 0)
 164                         break;
 165                 for (i = 0; devices[i]; i++)
 166                         if (strncmp(kbdintctxt->devices, devices[i]->name, len) == 0)
 167                                 kbdintctxt->device = devices[i];
 168                 t = kbdintctxt->devices;
 169                 kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL;
 170                 xfree(t);
 171                 debug2("kbdint_next_device: devices %s", kbdintctxt->devices ?
 172                     kbdintctxt->devices : "<empty>");
 173         } while (kbdintctxt->devices && !kbdintctxt->device);
 174
 175         return kbdintctxt->device ? 1 : 0;
 176 }
 177
 178 /*
 179  * try challenge-response, set authctxt->postponed if we have to
 180  * wait for the response.
 181  */
 182 int
 183 auth2_challenge(Authctxt *authctxt, char *devs)
 184 {
 185         debug("auth2_challenge: user=%s devs=%s",
 186             authctxt->user ? authctxt->user : "<nouser>",
 187             devs ? devs : "<no devs>");
 188
 189         if (authctxt->user == NULL || !devs)
 190                 return 0;
 191         if (authctxt->kbdintctxt == NULL)
 192                 authctxt->kbdintctxt = kbdint_alloc(devs);
 193         return auth2_challenge_start(authctxt);
 194 }
 195
 196 /* unregister kbd-int callbacks and context */
 197 void
 198 auth2_challenge_stop(Authctxt *authctxt)
 199 {
 200         /* unregister callback */
 201         dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL);
 202         if (authctxt->kbdintctxt != NULL)  {
 203                 kbdint_free(authctxt->kbdintctxt);
 204                 authctxt->kbdintctxt = NULL;
 205         }
 206 }
 207
 208 /* side effect: sets authctxt->postponed if a reply was sent*/
 209 static int
 210 auth2_challenge_start(Authctxt *authctxt)
 211 {
 212         KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt;
 213
 214         debug2("auth2_challenge_start: devices %s",
 215             kbdintctxt->devices ?  kbdintctxt->devices : "<empty>");
 216
 217         if (kbdint_next_device(kbdintctxt) == 0) {
 218                 auth2_challenge_stop(authctxt);
 219                 return 0;
 220         }
 221         debug("auth2_challenge_start: trying authentication method '%s'",
 222             kbdintctxt->device->name);
 223
 224         if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) {
 225                 auth2_challenge_stop(authctxt);
 226                 return 0;
 227         }
 228         if (send_userauth_info_request(authctxt) == 0) {
 229                 auth2_challenge_stop(authctxt);
 230                 return 0;
 231         }
 232         dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE,
 233             &input_userauth_info_response);
 234
 235         authctxt->postponed = 1;
 236         return 0;
 237 }
 238
 239 static int
 240 send_userauth_info_request(Authctxt *authctxt)
 241 {
 242         KbdintAuthctxt *kbdintctxt;
 243         char *name, *instr, **prompts;
 244         u_int i, *echo_on;
 245
 246         kbdintctxt = authctxt->kbdintctxt;
 247         if (kbdintctxt->device->query(kbdintctxt->ctxt,
 248             &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on))
 249                 return 0;
 250
 251         packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST);
 252         packet_put_cstring(name);
 253         packet_put_cstring(instr);
 254         packet_put_cstring("");         /* language not used */
 255         packet_put_int(kbdintctxt->nreq);
 256         for (i = 0; i < kbdintctxt->nreq; i++) {
 257                 packet_put_cstring(prompts[i]);
 258                 packet_put_char(echo_on[i]);
 259         }
 260         packet_send();
 261         packet_write_wait();
 262
 263         for (i = 0; i < kbdintctxt->nreq; i++)
 264                 xfree(prompts[i]);
 265         xfree(prompts);
 266         xfree(echo_on);
 267         xfree(name);
 268         xfree(instr);
 269         return 1;
 270 }
 271
 272 static void
 273 input_userauth_info_response(int type, u_int32_t seq, void *ctxt)
 274 {
 275         Authctxt *authctxt = ctxt;
 276         KbdintAuthctxt *kbdintctxt;
 277         int authenticated = 0, res, len;
 278         u_int i, nresp;
 279         char **response = NULL, *method;
 280
 281         if (authctxt == NULL)
 282                 fatal("input_userauth_info_response: no authctxt");
 283         kbdintctxt = authctxt->kbdintctxt;
 284         if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL)
 285                 fatal("input_userauth_info_response: no kbdintctxt");
 286         if (kbdintctxt->device == NULL)
 287                 fatal("input_userauth_info_response: no device");
 288
 289         authctxt->postponed = 0;        /* reset */
 290         nresp = packet_get_int();
 291         if (nresp != kbdintctxt->nreq)
 292                 fatal("input_userauth_info_response: wrong number of replies");
 293         if (nresp > 100)
 294                 fatal("input_userauth_info_response: too many replies");
 295         if (nresp > 0) {
 296                 response = xcalloc(nresp, sizeof(char *));
 297                 for (i = 0; i < nresp; i++)
 298                         response[i] = packet_get_string(NULL);
 299         }
 300         packet_check_eom();
 301
 302         res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response);
 303
 304         for (i = 0; i < nresp; i++) {
 305                 memset(response[i], 'r', strlen(response[i]));
 306                 xfree(response[i]);
 307         }
 308         if (response)
 309                 xfree(response);
 310
 311         switch (res) {
 312         case 0:
 313                 /* Success! */
 314                 authenticated = authctxt->valid ? 1 : 0;
 315                 break;
 316         case 1:
 317                 /* Authentication needs further interaction */
 318                 if (send_userauth_info_request(authctxt) == 1)
 319                         authctxt->postponed = 1;
 320                 break;
 321         default:
 322                 /* Failure! */
 323                 break;
 324         }
 325
 326         len = strlen("keyboard-interactive") + 2 +
 327                 strlen(kbdintctxt->device->name);
 328         method = xmalloc(len);
 329         snprintf(method, len, "keyboard-interactive/%s",
 330             kbdintctxt->device->name);
 331
 332         if (!authctxt->postponed) {
 333                 if (authenticated) {
 334                         auth2_challenge_stop(authctxt);
 335                 } else {
 336                         /* start next device */
 337                         /* may set authctxt->postponed */
 338                         auth2_challenge_start(authctxt);
 339                 }
 340         }
 341         userauth_finish(authctxt, authenticated, method);
 342         xfree(method);
 343 }
 344
 345 void
 346 privsep_challenge_enable(void)
 347 {
 348 #if defined(BSD_AUTH) || defined(USE_PAM) || defined(SKEY)
 349         int n = 0;
 350 #endif
 351 #ifdef BSD_AUTH
 352         extern KbdintDevice mm_bsdauth_device;
 353 #endif
 354 #ifdef USE_PAM
 355         extern KbdintDevice mm_sshpam_device;
 356 #endif
 357 #ifdef SKEY
 358         extern KbdintDevice mm_skey_device;
 359 #endif
 360
 361 #ifdef BSD_AUTH
 362         devices[n++] = &mm_bsdauth_device;
 363 #else
 364 #ifdef USE_PAM
 365         devices[n++] = &mm_sshpam_device;
 366 #endif
 367 #ifdef SKEY
 368         devices[n++] = &mm_skey_device;
 369 #endif
 370 #endif
 371 }