appl/kx/krb5.c

   1 /*
   2  * Copyright (c) 1995 - 2004 Kungliga Tekniska Högskolan
   3  * (Royal Institute of Technology, Stockholm, Sweden).
   4  * 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  *
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  *
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * 3. Neither the name of the Institute nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 #include "kx.h"
  35
  36 RCSID("$Id$");
  37
  38 #ifdef KRB5
  39
  40 struct krb5_kx_context {
  41     krb5_context context;
  42     krb5_keyblock *keyblock;
  43     krb5_crypto crypto;
  44     krb5_principal client;
  45     krb5_log_facility *log;
  46
  47 };
  48
  49 typedef struct krb5_kx_context krb5_kx_context;
  50
  51 #define K5DATA(kc) ((krb5_kx_context*)kc->data)
  52 #define CONTEXT(kc) (K5DATA(kc)->context)
  53
  54 /*
  55  * Destroy the krb5 context in `c'.
  56  */
  57
  58 static void
  59 krb5_destroy (kx_context *kc)
  60 {
  61     if (K5DATA(kc)->keyblock)
  62         krb5_free_keyblock (CONTEXT(kc), K5DATA(kc)->keyblock);
  63     if (K5DATA(kc)->crypto)
  64         krb5_crypto_destroy (CONTEXT(kc), K5DATA(kc)->crypto);
  65     if (K5DATA(kc)->client)
  66         krb5_free_principal (CONTEXT(kc), K5DATA(kc)->client);
  67     if (CONTEXT(kc))
  68         krb5_free_context (CONTEXT(kc));
  69     memset (kc->data, 0, sizeof(krb5_kx_context));
  70     free (kc->data);
  71 }
  72
  73 /*
  74  * Read the authentication information from `s' and return 0 if
  75  * succesful, else -1.
  76  */
  77
  78 static int
  79 krb5_authenticate (kx_context *kc, int s)
  80 {
  81     krb5_auth_context auth_context = NULL;
  82     krb5_error_code ret;
  83     krb5_principal server;
  84     const char *host = kc->host;
  85
  86     ret = krb5_sname_to_principal (CONTEXT(kc),
  87                                    host, "host", KRB5_NT_SRV_HST, &server);
  88     if (ret) {
  89         krb5_warn (CONTEXT(kc), ret, "krb5_sname_to_principal: %s", host);
  90         return 1;
  91     }
  92
  93     ret = krb5_sendauth (CONTEXT(kc),
  94                          &auth_context,
  95                          &s,
  96                          KX_VERSION,
  97                          NULL,
  98                          server,
  99                          AP_OPTS_MUTUAL_REQUIRED | AP_OPTS_USE_SUBKEY,
 100                          NULL,
 101                          NULL,
 102                          NULL,
 103                          NULL,
 104                          NULL,
 105                          NULL);
 106     if (ret) {
 107         if(ret != KRB5_SENDAUTH_BADRESPONSE)
 108             krb5_warn (CONTEXT(kc), ret, "krb5_sendauth: %s", host);
 109         return 1;
 110     }
 111
 112     ret = krb5_auth_con_getkey (CONTEXT(kc), auth_context,
 113                                 &K5DATA(kc)->keyblock);
 114     if (ret) {
 115         krb5_warn (CONTEXT(kc), ret, "krb5_auth_con_getkey: %s", host);
 116         krb5_auth_con_free (CONTEXT(kc), auth_context);
 117         return 1;
 118     }
 119
 120     ret = krb5_crypto_init (CONTEXT(kc), K5DATA(kc)->keyblock,
 121                             0, &K5DATA(kc)->crypto);
 122     if (ret) {
 123         krb5_warn (CONTEXT(kc), ret, "krb5_crypto_init");
 124         krb5_auth_con_free (CONTEXT(kc), auth_context);
 125         return 1;
 126     }
 127     return 0;
 128 }
 129
 130 /*
 131  * Read an encapsulated krb5 packet from `fd' into `buf' (of size
 132  * `len').  Return the number of bytes read or 0 on EOF or -1 on
 133  * error.
 134  */
 135
 136 static ssize_t
 137 krb5_read (kx_context *kc,
 138            int fd, void *buf, size_t len)
 139 {
 140     size_t data_len, outer_len;
 141     krb5_error_code ret;
 142     unsigned char tmp[4];
 143     krb5_data data;
 144     int l;
 145
 146     l = krb5_net_read (CONTEXT(kc), &fd, tmp, 4);
 147     if (l == 0)
 148         return l;
 149     if (l != 4)
 150         return -1;
 151     data_len  = (tmp[0] << 24) | (tmp[1] << 16) | (tmp[2] << 8) | tmp[3];
 152     outer_len = krb5_get_wrapped_length (CONTEXT(kc),
 153                                          K5DATA(kc)->crypto, data_len);
 154     if (outer_len > len)
 155         return -1;
 156     if (krb5_net_read (CONTEXT(kc), &fd, buf, outer_len) != outer_len)
 157         return -1;
 158
 159     ret = krb5_decrypt (CONTEXT(kc), K5DATA(kc)->crypto,
 160                         KRB5_KU_OTHER_ENCRYPTED,
 161                         buf, outer_len, &data);
 162     if (ret) {
 163         krb5_warn (CONTEXT(kc), ret, "krb5_decrypt");
 164         return -1;
 165     }
 166     if (data_len > data.length) {
 167         krb5_data_free (&data);
 168         return -1;
 169     }
 170     memmove (buf, data.data, data_len);
 171     krb5_data_free (&data);
 172     return data_len;
 173 }
 174
 175 /*
 176  * Write an encapsulated krb5 packet on `fd' with the data in `buf,
 177  * len'.  Return len or -1 on error.
 178  */
 179
 180 static ssize_t
 181 krb5_write(kx_context *kc,
 182            int fd, const void *buf, size_t len)
 183 {
 184     krb5_data data;
 185     krb5_error_code ret;
 186     unsigned char tmp[4];
 187     size_t outlen;
 188
 189     ret = krb5_encrypt (CONTEXT(kc), K5DATA(kc)->crypto,
 190                         KRB5_KU_OTHER_ENCRYPTED,
 191                         (void *)buf, len, &data);
 192     if (ret){
 193         krb5_warn (CONTEXT(kc), ret, "krb5_write");
 194         return -1;
 195     }
 196
 197     outlen = data.length;
 198     tmp[0] = (len >> 24) & 0xFF;
 199     tmp[1] = (len >> 16) & 0xFF;
 200     tmp[2] = (len >>  8) & 0xFF;
 201     tmp[3] = (len >>  0) & 0xFF;
 202
 203     if (krb5_net_write (CONTEXT(kc), &fd, tmp, 4) != 4 ||
 204         krb5_net_write (CONTEXT(kc), &fd, data.data, outlen) != outlen) {
 205         krb5_data_free (&data);
 206         return -1;
 207     }
 208     krb5_data_free (&data);
 209     return len;
 210 }
 211
 212 /*
 213  * Copy from the unix socket `from_fd' encrypting to `to_fd'.
 214  * Return 0, -1 or len.
 215  */
 216
 217 static int
 218 copy_out (kx_context *kc, int from_fd, int to_fd)
 219 {
 220     char buf[32768];
 221     ssize_t len;
 222
 223     len = read (from_fd, buf, sizeof(buf));
 224     if (len == 0)
 225         return 0;
 226     if (len < 0) {
 227         krb5_warn (CONTEXT(kc), errno, "read");
 228         return len;
 229     }
 230     return krb5_write (kc, to_fd, buf, len);
 231 }
 232
 233 /*
 234  * Copy from the socket `from_fd' decrypting to `to_fd'.
 235  * Return 0, -1 or len.
 236  */
 237
 238 static int
 239 copy_in (kx_context *kc, int from_fd, int to_fd)
 240 {
 241     char buf[33000];            /* XXX */
 242
 243     ssize_t len;
 244
 245     len = krb5_read (kc, from_fd, buf, sizeof(buf));
 246     if (len == 0)
 247         return 0;
 248     if (len < 0) {
 249         krb5_warn (CONTEXT(kc), errno, "krb5_read");
 250         return len;
 251     }
 252
 253     return krb5_net_write (CONTEXT(kc), &to_fd, buf, len);
 254 }
 255
 256 /*
 257  * Copy data between `fd1' and `fd2', encrypting in one direction and
 258  * decrypting in the other.
 259  */
 260
 261 static int
 262 krb5_copy_encrypted (kx_context *kc, int fd1, int fd2)
 263 {
 264     for (;;) {
 265         fd_set fdset;
 266         int ret;
 267
 268         if (fd1 >= FD_SETSIZE || fd2 >= FD_SETSIZE) {
 269             krb5_warnx (CONTEXT(kc), "fd too large");
 270             return 1;
 271         }
 272
 273         FD_ZERO(&fdset);
 274         FD_SET(fd1, &fdset);
 275         FD_SET(fd2, &fdset);
 276
 277         ret = select (max(fd1, fd2)+1, &fdset, NULL, NULL, NULL);
 278         if (ret < 0 && errno != EINTR) {
 279             krb5_warn (CONTEXT(kc), errno, "select");
 280             return 1;
 281         }
 282         if (FD_ISSET(fd1, &fdset)) {
 283             ret = copy_out (kc, fd1, fd2);
 284             if (ret <= 0)
 285                 return ret;
 286         }
 287         if (FD_ISSET(fd2, &fdset)) {
 288             ret = copy_in (kc, fd2, fd1);
 289             if (ret <= 0)
 290                 return ret;
 291         }
 292     }
 293 }
 294
 295 /*
 296  * Return 0 if the user authenticated on `kc' is allowed to login as
 297  * `user'.
 298  */
 299
 300 static int
 301 krb5_userok (kx_context *kc, char *user)
 302 {
 303     krb5_error_code ret;
 304     char *tmp;
 305
 306     ret = krb5_unparse_name (CONTEXT(kc), K5DATA(kc)->client, &tmp);
 307     if (ret)
 308         krb5_err (CONTEXT(kc), 1, ret, "krb5_unparse_name");
 309     kc->user = tmp;
 310
 311     return !krb5_kuserok (CONTEXT(kc), K5DATA(kc)->client, user);
 312 }
 313
 314 /*
 315  * Create an instance of an krb5 context.
 316  */
 317
 318 void
 319 krb5_make_context (kx_context *kc)
 320 {
 321     krb5_kx_context *c;
 322     krb5_error_code ret;
 323
 324     kc->authenticate    = krb5_authenticate;
 325     kc->userok          = krb5_userok;
 326     kc->read            = krb5_read;
 327     kc->write           = krb5_write;
 328     kc->copy_encrypted  = krb5_copy_encrypted;
 329     kc->destroy         = krb5_destroy;
 330     kc->user            = NULL;
 331     kc->data            = malloc(sizeof(krb5_kx_context));
 332
 333     if (kc->data == NULL) {
 334         syslog (LOG_ERR, "failed to malloc %u bytes", sizeof(krb5_kx_context));
 335         exit(1);
 336     }
 337     memset (kc->data, 0, sizeof(krb5_kx_context));
 338     c = (krb5_kx_context *)kc->data;
 339     ret = krb5_init_context (&c->context);
 340     if (ret) {
 341         syslog (LOG_ERR, "failed initialise krb5 context");
 342         exit(1);
 343     }
 344 }
 345
 346 /*
 347  * Receive authentication information on `sock' (first four bytes
 348  * in `buf').
 349  */
 350
 351 int
 352 recv_v5_auth (kx_context *kc, int sock, u_char *buf)
 353 {
 354     u_int32_t len;
 355     krb5_error_code ret;
 356     krb5_principal server;
 357     krb5_auth_context auth_context = NULL;
 358     krb5_ticket *ticket;
 359
 360     if (memcmp (buf, "\x00\x00\x00\x13", 4) != 0)
 361         return 1;
 362     len = (buf[0] << 24) | (buf[1] << 16) | (buf[2] << 8) | (buf[3]);
 363     if (net_read(sock, buf, len) != len) {
 364         syslog (LOG_ERR, "read: %m");
 365         exit (1);
 366     }
 367     if (len != sizeof(KRB5_SENDAUTH_VERSION)
 368         || memcmp (buf, KRB5_SENDAUTH_VERSION, len) != 0) {
 369         syslog (LOG_ERR, "bad sendauth version: %.8s", buf);
 370         exit (1);
 371     }
 372
 373     krb5_make_context (kc);
 374     krb5_openlog(CONTEXT(kc), "kxd", &K5DATA(kc)->log);
 375     krb5_set_warn_dest(CONTEXT(kc), K5DATA(kc)->log);
 376
 377     ret = krb5_sock_to_principal (CONTEXT(kc), sock, "host",
 378                                   KRB5_NT_SRV_HST, &server);
 379     if (ret) {
 380         syslog (LOG_ERR, "krb5_sock_to_principal: %s",
 381                 krb5_get_err_text (CONTEXT(kc), ret));
 382         exit (1);
 383     }
 384
 385     ret = krb5_recvauth (CONTEXT(kc),
 386                          &auth_context,
 387                          &sock,
 388                          KX_VERSION,
 389                          server,
 390                          KRB5_RECVAUTH_IGNORE_VERSION,
 391                          NULL,
 392                          &ticket);
 393     krb5_free_principal (CONTEXT(kc), server);
 394     if (ret) {
 395         syslog (LOG_ERR, "krb5_sock_to_principal: %s",
 396                 krb5_get_err_text (CONTEXT(kc), ret));
 397         exit (1);
 398     }
 399
 400     ret = krb5_auth_con_getkey (CONTEXT(kc), auth_context, &K5DATA(kc)->keyblock);
 401     if (ret) {
 402         syslog (LOG_ERR, "krb5_auth_con_getkey: %s",
 403                 krb5_get_err_text (CONTEXT(kc), ret));
 404         exit (1);
 405     }
 406
 407     ret = krb5_crypto_init (CONTEXT(kc), K5DATA(kc)->keyblock, 0, &K5DATA(kc)->crypto);
 408     if (ret) {
 409         syslog (LOG_ERR, "krb5_crypto_init: %s",
 410                 krb5_get_err_text (CONTEXT(kc), ret));
 411         exit (1);
 412     }
 413
 414     K5DATA(kc)->client = ticket->client;
 415     ticket->client = NULL;
 416     krb5_free_ticket (CONTEXT(kc), ticket);
 417
 418     return 0;
 419 }
 420
 421 #endif /* KRB5 */