subversion/svnserve/cyrus_auth.c

   1 /*
   2  * sasl_auth.c :  Functions for SASL-based authentication
   3  *
   4  * ====================================================================
   5  * Copyright (c) 2006-2007 CollabNet.  All rights reserved.
   6  *
   7  * This software is licensed as described in the file COPYING, which
   8  * you should have received as part of this distribution.  The terms
   9  * are also available at http://subversion.tigris.org/license-1.html.
  10  * If newer versions of this license are posted there, you may use a
  11  * newer version instead, at your option.
  12  *
  13  * This software consists of voluntary contributions made by many
  14  * individuals.  For exact contribution history, see the revision
  15  * history and logs, available at http://subversion.tigris.org/.
  16  * ====================================================================
  17  */
  18
  19 #include "svn_private_config.h"
  20 #ifdef SVN_HAVE_SASL
  21
  22 #define APR_WANT_STRFUNC
  23 #include <apr_want.h>
  24 #include <apr_general.h>
  25 #include <apr_strings.h>
  26
  27 #include "svn_types.h"
  28 #include "svn_string.h"
  29 #include "svn_pools.h"
  30 #include "svn_error.h"
  31 #include "svn_ra_svn.h"
  32 #include "svn_base64.h"
  33
  34 #include "private/svn_atomic.h"
  35 #include "private/ra_svn_sasl.h"
  36
  37 #include "server.h"
  38
  39 /* SASL calls this function before doing anything with a username, which gives
  40    us an opportunity to do some sanity-checking.  If the username contains
  41    an '@', SASL interprets the part following the '@' as the name of the
  42    authentication realm, and worst of all, this realm overrides the one that
  43    we pass to sasl_server_new().  If we didn't check this, a user that could
  44    successfully authenticate in one realm would be able to authenticate
  45    in any other realm, simply by appending '@realm' to his username. */
  46 static int canonicalize_username(sasl_conn_t *conn,
  47                                  void *context, /* not used */
  48                                  const char *in, /* the username */
  49                                  unsigned inlen, /* its length */
  50                                  unsigned flags, /* not used */
  51                                  const char *user_realm,
  52                                  char *out, /* the output buffer */
  53                                  unsigned out_max, unsigned *out_len)
  54 {
  55   int realm_len = strlen(user_realm);
  56   char *pos;
  57
  58   *out_len = inlen;
  59
  60   /* If the username contains an '@', the part after the '@' is the realm
  61      that the user wants to authenticate in. */
  62   pos = memchr(in, '@', inlen);
  63   if (pos)
  64     {
  65       /* The only valid realm is user_realm (i.e. the repository's realm).
  66          If the user gave us another realm, complain. */
  67       if (strncmp(pos+1, user_realm, inlen-(pos-in+1)) != 0)
  68         return SASL_BADPROT;
  69     }
  70   else
  71     *out_len += realm_len + 1;
  72
  73   /* First, check that the output buffer is large enough. */
  74   if (*out_len > out_max)
  75     return SASL_BADPROT;
  76
  77   /* Copy the username part. */
  78   strncpy(out, in, inlen);
  79
  80   /* If necessary, copy the realm part. */
  81   if (!pos)
  82     {
  83       out[inlen] = '@';
  84       strncpy(&out[inlen+1], user_realm, realm_len);
  85     }
  86
  87   return SASL_OK;
  88 }
  89
  90 static sasl_callback_t callbacks[] =
  91 {
  92   { SASL_CB_CANON_USER, canonicalize_username, NULL },
  93   { SASL_CB_LIST_END, NULL, NULL }
  94 };
  95
  96 static svn_error_t *initialize(apr_pool_t *pool)
  97 {
  98   int result;
  99   apr_status_t status;
 100
 101   status = svn_ra_svn__sasl_common_init(pool);
 102   if (status)
 103     return svn_error_wrap_apr(status,
 104                               _("Could not initialize the SASL library"));
 105
 106   /* The second parameter tells SASL to look for a configuration file
 107      named subversion.conf. */
 108   result = sasl_server_init(callbacks, SVN_RA_SVN_SASL_NAME);
 109   if (result != SASL_OK)
 110     {
 111       svn_error_t *err = svn_error_create(SVN_ERR_RA_NOT_AUTHORIZED, NULL,
 112                                           sasl_errstring(result, NULL, NULL));
 113       return svn_error_quick_wrap(err,
 114                                   _("Could not initialize the SASL library"));
 115     }
 116   return SVN_NO_ERROR;
 117 }
 118
 119 svn_error_t *cyrus_init(apr_pool_t *pool)
 120 {
 121   SVN_ERR(svn_atomic__init_once(&svn_ra_svn__sasl_status, initialize, pool));
 122   return SVN_NO_ERROR;
 123 }
 124
 125 /* Tell the client the authentication failed. This is only used during
 126    the authentication exchange (i.e. inside try_auth()). */
 127 static svn_error_t *
 128 fail_auth(svn_ra_svn_conn_t *conn, apr_pool_t *pool, sasl_conn_t *sasl_ctx)
 129 {
 130   const char *msg = sasl_errdetail(sasl_ctx);
 131   SVN_ERR(svn_ra_svn_write_tuple(conn, pool, "w(c)", "failure", msg));
 132   return svn_ra_svn_flush(conn, pool);
 133 }
 134
 135 /* Like svn_ra_svn_write_cmd_failure, but also clears the given error
 136    and sets it to SVN_NO_ERROR. */
 137 static svn_error_t *
 138 write_failure(svn_ra_svn_conn_t *conn, apr_pool_t *pool, svn_error_t **err_p)
 139 {
 140   svn_error_t *write_err = svn_ra_svn_write_cmd_failure(conn, pool, *err_p);
 141   svn_error_clear(*err_p);
 142   *err_p = SVN_NO_ERROR;
 143   return write_err;
 144 }
 145
 146 /* Used if we run into a SASL error outside try_auth(). */
 147 static svn_error_t *
 148 fail_cmd(svn_ra_svn_conn_t *conn, apr_pool_t *pool, sasl_conn_t *sasl_ctx)
 149 {
 150   svn_error_t *err = svn_error_create(SVN_ERR_RA_NOT_AUTHORIZED, NULL,
 151                                       sasl_errdetail(sasl_ctx));
 152   SVN_ERR(write_failure(conn, pool, &err));
 153   return svn_ra_svn_flush(conn, pool);
 154 }
 155
 156 static svn_error_t *try_auth(svn_ra_svn_conn_t *conn,
 157                              sasl_conn_t *sasl_ctx,
 158                              apr_pool_t *pool,
 159                              server_baton_t *b,
 160                              svn_boolean_t *success)
 161 {
 162   const char *out, *mech;
 163   const svn_string_t *arg = NULL, *in;
 164   unsigned int outlen;
 165   int result;
 166   svn_boolean_t use_base64;
 167
 168   *success = FALSE;
 169
 170   /* Read the client's chosen mech and the initial token. */
 171   SVN_ERR(svn_ra_svn_read_tuple(conn, pool, "w(?s)", &mech, &in));
 172
 173   if (strcmp(mech, "EXTERNAL") == 0 && !in)
 174     in = svn_string_create(b->tunnel_user, pool);
 175   else if (in)
 176     in = svn_base64_decode_string(in, pool);
 177
 178   /* For CRAM-MD5, we don't base64-encode stuff. */
 179   use_base64 = (strcmp(mech, "CRAM-MD5") != 0);
 180
 181   result = sasl_server_start(sasl_ctx, mech,
 182                              in ? in->data : NULL,
 183                              in ? in->len : 0, &out, &outlen);
 184
 185   if (result != SASL_OK && result != SASL_CONTINUE)
 186     return fail_auth(conn, pool, sasl_ctx);
 187
 188   while (result == SASL_CONTINUE)
 189     {
 190       svn_ra_svn_item_t *item;
 191
 192       arg = svn_string_ncreate(out, outlen, pool);
 193       /* Encode what we send to the client. */
 194       if (use_base64)
 195         arg = svn_base64_encode_string(arg, pool);
 196
 197       SVN_ERR(svn_ra_svn_write_tuple(conn, pool, "w(s)", "step", arg));
 198
 199       /* Read and decode the client response. */
 200       SVN_ERR(svn_ra_svn_read_item(conn, pool, &item));
 201       if (item->kind != SVN_RA_SVN_STRING)
 202         return SVN_NO_ERROR;
 203
 204       in = item->u.string;
 205       if (use_base64)
 206         in = svn_base64_decode_string(in, pool);
 207       result = sasl_server_step(sasl_ctx, in->data, in->len, &out, &outlen);
 208     }
 209
 210   if (result != SASL_OK)
 211     return fail_auth(conn, pool, sasl_ctx);
 212
 213   /* Send our last response, if necessary. */
 214   if (outlen)
 215     arg = svn_base64_encode_string(svn_string_ncreate(out, outlen, pool),
 216                                    pool);
 217   else
 218     arg = NULL;
 219
 220   *success = TRUE;
 221   SVN_ERR(svn_ra_svn_write_tuple(conn, pool, "w(?s)", "success", arg));
 222
 223   return SVN_NO_ERROR;
 224 }
 225
 226 static apr_status_t sasl_dispose_cb(void *data)
 227 {
 228   sasl_conn_t *sasl_ctx = (sasl_conn_t*) data;
 229   sasl_dispose(&sasl_ctx);
 230   return APR_SUCCESS;
 231 }
 232
 233 svn_error_t *cyrus_auth_request(svn_ra_svn_conn_t *conn,
 234                                 apr_pool_t *pool,
 235                                 server_baton_t *b,
 236                                 enum access_type required,
 237                                 svn_boolean_t needs_username)
 238 {
 239   sasl_conn_t *sasl_ctx;
 240   apr_pool_t *subpool;
 241   apr_status_t apr_err;
 242   const char *localaddrport = NULL, *remoteaddrport = NULL;
 243   const char *mechlist, *val;
 244   char hostname[APRMAXHOSTLEN + 1];
 245   sasl_security_properties_t secprops;
 246   svn_boolean_t success, no_anonymous;
 247   int mech_count, result = SASL_OK;
 248
 249   SVN_ERR(svn_ra_svn__get_addresses(&localaddrport, &remoteaddrport,
 250                                         conn, pool));
 251   apr_err = apr_gethostname(hostname, sizeof(hostname), pool);
 252   if (apr_err)
 253     {
 254       svn_error_t *err = svn_error_wrap_apr(apr_err, _("Can't get hostname"));
 255       SVN_ERR(write_failure(conn, pool, &err));
 256       return svn_ra_svn_flush(conn, pool);
 257     }
 258
 259   /* Create a SASL context. SASL_SUCCESS_DATA tells SASL that the protocol
 260      supports sending data along with the final "success" message. */
 261   result = sasl_server_new(SVN_RA_SVN_SASL_NAME,
 262                            hostname, b->realm,
 263                            localaddrport, remoteaddrport,
 264                            NULL, SASL_SUCCESS_DATA,
 265                            &sasl_ctx);
 266   if (result != SASL_OK)
 267     {
 268       svn_error_t *err = svn_error_create(SVN_ERR_RA_NOT_AUTHORIZED, NULL,
 269                                           sasl_errstring(result, NULL, NULL));
 270       SVN_ERR(write_failure(conn, pool, &err));
 271       return svn_ra_svn_flush(conn, pool);
 272     }
 273
 274   /* Make sure the context is always destroyed. */
 275   apr_pool_cleanup_register(b->pool, sasl_ctx, sasl_dispose_cb,
 276                             apr_pool_cleanup_null);
 277
 278   /* Initialize security properties. */
 279   svn_ra_svn__default_secprops(&secprops);
 280
 281   /* Don't allow PLAIN or LOGIN, since we don't support TLS yet. */
 282   secprops.security_flags = SASL_SEC_NOPLAINTEXT;
 283
 284   /* Don't allow ANONYMOUS if a username is required. */
 285   no_anonymous = needs_username || get_access(b, UNAUTHENTICATED) < required;
 286   if (no_anonymous)
 287     secprops.security_flags |= SASL_SEC_NOANONYMOUS;
 288
 289   svn_config_get(b->cfg, &val,
 290                  SVN_CONFIG_SECTION_SASL,
 291                  SVN_CONFIG_OPTION_MIN_SSF,
 292                  "0");
 293   secprops.min_ssf = atoi(val);
 294
 295   svn_config_get(b->cfg, &val,
 296                  SVN_CONFIG_SECTION_SASL,
 297                  SVN_CONFIG_OPTION_MAX_SSF,
 298                  "256");
 299   secprops.max_ssf = atoi(val);
 300
 301   /* Set security properties. */
 302   result = sasl_setprop(sasl_ctx, SASL_SEC_PROPS, &secprops);
 303   if (result != SASL_OK)
 304     return fail_cmd(conn, pool, sasl_ctx);
 305
 306   /* SASL needs to know if we are externally authenticated. */
 307   if (b->tunnel_user)
 308     result = sasl_setprop(sasl_ctx, SASL_AUTH_EXTERNAL, b->tunnel_user);
 309   if (result != SASL_OK)
 310     return fail_cmd(conn, pool, sasl_ctx);
 311
 312   /* Get the list of mechanisms. */
 313   result = sasl_listmech(sasl_ctx, NULL, NULL, " ", NULL,
 314                          &mechlist, NULL, &mech_count);
 315
 316   if (result != SASL_OK)
 317     return fail_cmd(conn, pool, sasl_ctx);
 318
 319   if (mech_count == 0)
 320     {
 321       svn_error_t *err = svn_error_create(SVN_ERR_RA_NOT_AUTHORIZED, NULL,
 322                                           _("Could not obtain the list"
 323                                           " of SASL mechanisms"));
 324       SVN_ERR(write_failure(conn, pool, &err));
 325       return svn_ra_svn_flush(conn, pool);
 326     }
 327
 328   /* Send the list of mechanisms and the realm to the client. */
 329   SVN_ERR(svn_ra_svn_write_cmd_response(conn, pool, "(w)c",
 330                                         mechlist, b->realm));
 331
 332   /* The main authentication loop. */
 333   subpool = svn_pool_create(pool);
 334   do
 335     {
 336       svn_pool_clear(subpool);
 337       SVN_ERR(try_auth(conn, sasl_ctx, subpool, b, &success));
 338     }
 339   while (!success);
 340   svn_pool_destroy(subpool);
 341
 342   SVN_ERR(svn_ra_svn__enable_sasl_encryption(conn, sasl_ctx, pool));
 343
 344   if (no_anonymous)
 345     {
 346       char *p;
 347       const void *user;
 348
 349       /* Get the authenticated username. */
 350       result = sasl_getprop(sasl_ctx, SASL_USERNAME, &user);
 351
 352       if (result != SASL_OK)
 353         return fail_cmd(conn, pool, sasl_ctx);
 354
 355       if ((p = strchr(user, '@')) != NULL)
 356         /* Drop the realm part. */
 357         b->user = apr_pstrndup(b->pool, user, p - (char *)user);
 358       else
 359         {
 360           svn_error_t *err;
 361           err = svn_error_create(SVN_ERR_RA_NOT_AUTHORIZED, NULL,
 362                                  _("Couldn't obtain the authenticated"
 363                                  " username"));
 364           SVN_ERR(write_failure(conn, pool, &err));
 365           return svn_ra_svn_flush(conn, pool);
 366         }
 367     }
 368
 369   return SVN_NO_ERROR;
 370 }
 371
 372 #endif /* SVN_HAVE_SASL */