auth2-chall.c

   1 /* $OpenBSD: auth2-chall.c,v 1.29 2006/08/01 23:22:47 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 <stdio.h>
  29 #include <string.h>
  30
  31 #include "ssh2.h"
  32 #include "auth.h"
  33 #include "buffer.h"
  34 #include "packet.h"
  35 #include "xmalloc.h"
  36 #include "dispatch.h"
  37 #include "log.h"
  38 #include "servconf.h"
  39
  40 /* import */
  41 extern ServerOptions options;
  42
  43 static int auth2_challenge_start(Authctxt *);
  44 static int send_userauth_info_request(Authctxt *);
  45 static void input_userauth_info_response(int, u_int32_t, void *);
  46
  47 #ifdef BSD_AUTH
  48 extern KbdintDevice bsdauth_device;
  49 #else
  50 #ifdef USE_PAM
  51 extern KbdintDevice sshpam_device;
  52 #endif
  53 #ifdef SKEY
  54 extern KbdintDevice skey_device;
  55 #endif
  56 #endif
  57
  58 KbdintDevice *devices[] = {
  59 #ifdef BSD_AUTH
  60         &bsdauth_device,
  61 #else
  62 #ifdef USE_PAM
  63         &sshpam_device,
  64 #endif
  65 #ifdef SKEY
  66         &skey_device,
  67 #endif
  68 #endif
  69         NULL
  70 };
  71
  72 typedef struct KbdintAuthctxt KbdintAuthctxt;
  73 struct KbdintAuthctxt
  74 {
  75         char *devices;
  76         void *ctxt;
  77         KbdintDevice *device;
  78         u_int nreq;
  79 };
  80
  81 #ifdef USE_PAM
  82 void
  83 remove_kbdint_device(const char *devname)
  84 {
  85         int i, j;
  86
  87         for (i = 0; devices[i] != NULL; i++)
  88                 if (strcmp(devices[i]->name, devname) == 0) {
  89                         for (j = i; devices[j] != NULL; j++)
  90                                 devices[j] = devices[j+1];
  91                         i--;
  92                 }
  93 }
  94 #endif
  95
  96 static KbdintAuthctxt *
  97 kbdint_alloc(const char *devs)
  98 {
  99         KbdintAuthctxt *kbdintctxt;
 100         Buffer b;
 101         int i;
 102
 103 #ifdef USE_PAM
 104         if (!options.use_pam)
 105                 remove_kbdint_device("pam");
 106 #endif
 107
 108         kbdintctxt = xmalloc(sizeof(KbdintAuthctxt));
 109         if (strcmp(devs, "") == 0) {
 110                 buffer_init(&b);
 111                 for (i = 0; devices[i]; i++) {
 112                         if (buffer_len(&b) > 0)
 113                                 buffer_append(&b, ",", 1);
 114                         buffer_append(&b, devices[i]->name,
 115                             strlen(devices[i]->name));
 116                 }
 117                 buffer_append(&b, "\0", 1);
 118                 kbdintctxt->devices = xstrdup(buffer_ptr(&b));
 119                 buffer_free(&b);
 120         } else {
 121                 kbdintctxt->devices = xstrdup(devs);
 122         }
 123         debug("kbdint_alloc: devices '%s'", kbdintctxt->devices);
 124         kbdintctxt->ctxt = NULL;
 125         kbdintctxt->device = NULL;
 126         kbdintctxt->nreq = 0;
 127
 128         return kbdintctxt;
 129 }
 130 static void
 131 kbdint_reset_device(KbdintAuthctxt *kbdintctxt)
 132 {
 133         if (kbdintctxt->ctxt) {
 134                 kbdintctxt->device->free_ctx(kbdintctxt->ctxt);
 135                 kbdintctxt->ctxt = NULL;
 136         }
 137         kbdintctxt->device = NULL;
 138 }
 139 static void
 140 kbdint_free(KbdintAuthctxt *kbdintctxt)
 141 {
 142         if (kbdintctxt->device)
 143                 kbdint_reset_device(kbdintctxt);
 144         if (kbdintctxt->devices) {
 145                 xfree(kbdintctxt->devices);
 146                 kbdintctxt->devices = NULL;
 147         }
 148         xfree(kbdintctxt);
 149 }
 150 /* get next device */
 151 static int
 152 kbdint_next_device(KbdintAuthctxt *kbdintctxt)
 153 {
 154         size_t len;
 155         char *t;
 156         int i;
 157
 158         if (kbdintctxt->device)
 159                 kbdint_reset_device(kbdintctxt);
 160         do {
 161                 len = kbdintctxt->devices ?
 162                     strcspn(kbdintctxt->devices, ",") : 0;
 163
 164                 if (len == 0)
 165                         break;
 166                 for (i = 0; devices[i]; i++)
 167                         if (strncmp(kbdintctxt->devices, devices[i]->name, len) == 0)
 168                                 kbdintctxt->device = devices[i];
 169                 t = kbdintctxt->devices;
 170                 kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL;
 171                 xfree(t);
 172                 debug2("kbdint_next_device: devices %s", kbdintctxt->devices ?
 173                     kbdintctxt->devices : "<empty>");
 174         } while (kbdintctxt->devices && !kbdintctxt->device);
 175
 176         return kbdintctxt->device ? 1 : 0;
 177 }
 178
 179 /*
 180  * try challenge-response, set authctxt->postponed if we have to
 181  * wait for the response.
 182  */
 183 int
 184 auth2_challenge(Authctxt *authctxt, char *devs)
 185 {
 186         debug("auth2_challenge: user=%s devs=%s",
 187             authctxt->user ? authctxt->user : "<nouser>",
 188             devs ? devs : "<no devs>");
 189
 190         if (authctxt->user == NULL || !devs)
 191                 return 0;
 192         if (authctxt->kbdintctxt == NULL)
 193                 authctxt->kbdintctxt = kbdint_alloc(devs);
 194         return auth2_challenge_start(authctxt);
 195 }
 196
 197 /* unregister kbd-int callbacks and context */
 198 void
 199 auth2_challenge_stop(Authctxt *authctxt)
 200 {
 201         /* unregister callback */
 202         dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL);
 203         if (authctxt->kbdintctxt != NULL)  {
 204                 kbdint_free(authctxt->kbdintctxt);
 205                 authctxt->kbdintctxt = NULL;
 206         }
 207 }
 208
 209 /* side effect: sets authctxt->postponed if a reply was sent*/
 210 static int
 211 auth2_challenge_start(Authctxt *authctxt)
 212 {
 213         KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt;
 214
 215         debug2("auth2_challenge_start: devices %s",
 216             kbdintctxt->devices ?  kbdintctxt->devices : "<empty>");
 217
 218         if (kbdint_next_device(kbdintctxt) == 0) {
 219                 auth2_challenge_stop(authctxt);
 220                 return 0;
 221         }
 222         debug("auth2_challenge_start: trying authentication method '%s'",
 223             kbdintctxt->device->name);
 224
 225         if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) {
 226                 auth2_challenge_stop(authctxt);
 227                 return 0;
 228         }
 229         if (send_userauth_info_request(authctxt) == 0) {
 230                 auth2_challenge_stop(authctxt);
 231                 return 0;
 232         }
 233         dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE,
 234             &input_userauth_info_response);
 235
 236         authctxt->postponed = 1;
 237         return 0;
 238 }
 239
 240 static int
 241 send_userauth_info_request(Authctxt *authctxt)
 242 {
 243         KbdintAuthctxt *kbdintctxt;
 244         char *name, *instr, **prompts;
 245         u_int i, *echo_on;
 246
 247         kbdintctxt = authctxt->kbdintctxt;
 248         if (kbdintctxt->device->query(kbdintctxt->ctxt,
 249             &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on))
 250                 return 0;
 251
 252         packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST);
 253         packet_put_cstring(name);
 254         packet_put_cstring(instr);
 255         packet_put_cstring("");         /* language not used */
 256         packet_put_int(kbdintctxt->nreq);
 257         for (i = 0; i < kbdintctxt->nreq; i++) {
 258                 packet_put_cstring(prompts[i]);
 259                 packet_put_char(echo_on[i]);
 260         }
 261         packet_send();
 262         packet_write_wait();
 263
 264         for (i = 0; i < kbdintctxt->nreq; i++)
 265                 xfree(prompts[i]);
 266         xfree(prompts);
 267         xfree(echo_on);
 268         xfree(name);
 269         xfree(instr);
 270         return 1;
 271 }
 272
 273 static void
 274 input_userauth_info_response(int type, u_int32_t seq, void *ctxt)
 275 {
 276         Authctxt *authctxt = ctxt;
 277         KbdintAuthctxt *kbdintctxt;
 278         int authenticated = 0, res, len;
 279         u_int i, nresp;
 280         char **response = NULL, *method;
 281
 282         if (authctxt == NULL)
 283                 fatal("input_userauth_info_response: no authctxt");
 284         kbdintctxt = authctxt->kbdintctxt;
 285         if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL)
 286                 fatal("input_userauth_info_response: no kbdintctxt");
 287         if (kbdintctxt->device == NULL)
 288                 fatal("input_userauth_info_response: no device");
 289
 290         authctxt->postponed = 0;        /* reset */
 291         nresp = packet_get_int();
 292         if (nresp != kbdintctxt->nreq)
 293                 fatal("input_userauth_info_response: wrong number of replies");
 294         if (nresp > 100)
 295                 fatal("input_userauth_info_response: too many replies");
 296         if (nresp > 0) {
 297                 response = xcalloc(nresp, sizeof(char *));
 298                 for (i = 0; i < nresp; i++)
 299                         response[i] = packet_get_string(NULL);
 300         }
 301         packet_check_eom();
 302
 303         res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response);
 304
 305         for (i = 0; i < nresp; i++) {
 306                 memset(response[i], 'r', strlen(response[i]));
 307                 xfree(response[i]);
 308         }
 309         if (response)
 310                 xfree(response);
 311
 312         switch (res) {
 313         case 0:
 314                 /* Success! */
 315                 authenticated = authctxt->valid ? 1 : 0;
 316                 break;
 317         case 1:
 318                 /* Authentication needs further interaction */
 319                 if (send_userauth_info_request(authctxt) == 1)
 320                         authctxt->postponed = 1;
 321                 break;
 322         default:
 323                 /* Failure! */
 324                 break;
 325         }
 326
 327         len = strlen("keyboard-interactive") + 2 +
 328                 strlen(kbdintctxt->device->name);
 329         method = xmalloc(len);
 330         snprintf(method, len, "keyboard-interactive/%s",
 331             kbdintctxt->device->name);
 332
 333         if (!authctxt->postponed) {
 334                 if (authenticated) {
 335                         auth2_challenge_stop(authctxt);
 336                 } else {
 337                         /* start next device */
 338                         /* may set authctxt->postponed */
 339                         auth2_challenge_start(authctxt);
 340                 }
 341         }
 342         userauth_finish(authctxt, authenticated, method);
 343         xfree(method);
 344 }
 345
 346 void
 347 privsep_challenge_enable(void)
 348 {
 349 #if defined(BSD_AUTH) || defined(USE_PAM) || defined(SKEY)
 350         int n = 0;
 351 #endif
 352 #ifdef BSD_AUTH
 353         extern KbdintDevice mm_bsdauth_device;
 354 #endif
 355 #ifdef USE_PAM
 356         extern KbdintDevice mm_sshpam_device;
 357 #endif
 358 #ifdef SKEY
 359         extern KbdintDevice mm_skey_device;
 360 #endif
 361
 362 #ifdef BSD_AUTH
 363         devices[n++] = &mm_bsdauth_device;
 364 #else
 365 #ifdef USE_PAM
 366         devices[n++] = &mm_sshpam_device;
 367 #endif
 368 #ifdef SKEY
 369         devices[n++] = &mm_skey_device;
 370 #endif
 371 #endif
 372 }