src/auths/spa.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) University of Cambridge 1995 - 2018 */
   6 /* See the file NOTICE for conditions of use and distribution. */
   7
   8 /* This file, which provides support for Microsoft's Secure Password
   9 Authentication, was contributed by Marc Prud'hommeaux. Tom Kistner added SPA
  10 server support. I (PH) have only modified it in very trivial ways.
  11
  12 References:
  13   http://www.innovation.ch/java/ntlm.html
  14   http://www.kuro5hin.org/story/2002/4/28/1436/66154
  15   http://download.microsoft.com/download/9/5/e/95ef66af-9026-4bb0-a41d-a4f81802d92c/%5bMS-SMTP%5d.pdf
  16
  17  * It seems that some systems have existing but different definitions of some
  18  * of the following types. I received a complaint about "int16" causing
  19  * compilation problems. So I (PH) have renamed them all, to be on the safe
  20  * side, by adding 'x' on the end. See auths/auth-spa.h.
  21
  22  * typedef signed short int16;
  23  * typedef unsigned short uint16;
  24  * typedef unsigned uint32;
  25  * typedef unsigned char  uint8;
  26
  27 07-August-2003:  PH: Patched up the code to avoid assert bombouts for stupid
  28                      input data. Find appropriate comment by grepping for "PH".
  29 16-October-2006: PH: Added a call to auth_check_serv_cond() at the end
  30 05-June-2010:    PP: handle SASL initial response
  31 */
  32
  33
  34 #include "../exim.h"
  35 #include "spa.h"
  36
  37 /* #define DEBUG_SPA */
  38
  39 #ifdef DEBUG_SPA
  40 #define DSPA(x,y,z)   debug_printf(x,y,z)
  41 #else
  42 #define DSPA(x,y,z)
  43 #endif
  44
  45 /* Options specific to the spa authentication mechanism. */
  46
  47 optionlist auth_spa_options[] = {
  48   { "client_domain",             opt_stringptr,
  49       (void *)(offsetof(auth_spa_options_block, spa_domain)) },
  50   { "client_password",           opt_stringptr,
  51       (void *)(offsetof(auth_spa_options_block, spa_password)) },
  52   { "client_username",           opt_stringptr,
  53       (void *)(offsetof(auth_spa_options_block, spa_username)) },
  54   { "server_password",           opt_stringptr,
  55       (void *)(offsetof(auth_spa_options_block, spa_serverpassword)) }
  56 };
  57
  58 /* Size of the options list. An extern variable has to be used so that its
  59 address can appear in the tables drtables.c. */
  60
  61 int auth_spa_options_count =
  62   sizeof(auth_spa_options)/sizeof(optionlist);
  63
  64 /* Default private options block for the condition authentication method. */
  65
  66 auth_spa_options_block auth_spa_option_defaults = {
  67   NULL,              /* spa_password */
  68   NULL,              /* spa_username */
  69   NULL,              /* spa_domain */
  70   NULL               /* spa_serverpassword (for server side use) */
  71 };
  72
  73
  74 #ifdef MACRO_PREDEF
  75
  76 /* Dummy values */
  77 void auth_spa_init(auth_instance *ablock) {}
  78 int auth_spa_server(auth_instance *ablock, uschar *data) {return 0;}
  79 int auth_spa_client(auth_instance *ablock, void * sx, int timeout,
  80     uschar *buffer, int buffsize) {return 0;}
  81
  82 #else   /*!MACRO_PREDEF*/
  83
  84
  85
  86
  87 /*************************************************
  88 *          Initialization entry point            *
  89 *************************************************/
  90
  91 /* Called for each instance, after its options have been read, to
  92 enable consistency checks to be done, or anything else that needs
  93 to be set up. */
  94
  95 void
  96 auth_spa_init(auth_instance *ablock)
  97 {
  98 auth_spa_options_block *ob =
  99   (auth_spa_options_block *)(ablock->options_block);
 100
 101 /* The public name defaults to the authenticator name */
 102
 103 if (ablock->public_name == NULL) ablock->public_name = ablock->name;
 104
 105 /* Both username and password must be set for a client */
 106
 107 if ((ob->spa_username == NULL) != (ob->spa_password == NULL))
 108   log_write(0, LOG_PANIC_DIE|LOG_CONFIG_FOR, "%s authenticator:\n  "
 109       "one of client_username and client_password cannot be set without "
 110       "the other", ablock->name);
 111 ablock->client = ob->spa_username != NULL;
 112
 113 /* For a server we have just one option */
 114
 115 ablock->server = ob->spa_serverpassword != NULL;
 116 }
 117
 118
 119
 120 /*************************************************
 121 *             Server entry point                 *
 122 *************************************************/
 123
 124 /* For interface, see auths/README */
 125
 126 #define CVAL(buf,pos) ((US (buf))[pos])
 127 #define PVAL(buf,pos) ((unsigned)CVAL(buf,pos))
 128 #define SVAL(buf,pos) (PVAL(buf,pos)|PVAL(buf,(pos)+1)<<8)
 129 #define IVAL(buf,pos) (SVAL(buf,pos)|SVAL(buf,(pos)+2)<<16)
 130
 131 int
 132 auth_spa_server(auth_instance *ablock, uschar *data)
 133 {
 134 auth_spa_options_block *ob = (auth_spa_options_block *)(ablock->options_block);
 135 uint8x lmRespData[24];
 136 uint8x ntRespData[24];
 137 SPAAuthRequest request;
 138 SPAAuthChallenge challenge;
 139 SPAAuthResponse  response;
 140 SPAAuthResponse  *responseptr = &response;
 141 uschar msgbuf[2048];
 142 uschar *clearpass;
 143
 144 /* send a 334, MS Exchange style, and grab the client's request,
 145 unless we already have it via an initial response. */
 146
 147 if ((*data == '\0') &&
 148     (auth_get_no64_data(&data, US"NTLM supported") != OK))
 149   {
 150   /* something borked */
 151   return FAIL;
 152   }
 153
 154 if (spa_base64_to_bits(CS (&request), sizeof(request), CCS (data)) < 0)
 155   {
 156   DEBUG(D_auth) debug_printf("auth_spa_server(): bad base64 data in "
 157   "request: %s\n", data);
 158   return FAIL;
 159   }
 160
 161 /* create a challenge and send it back */
 162
 163 spa_build_auth_challenge(&request,&challenge);
 164 spa_bits_to_base64 (msgbuf, (unsigned char*)&challenge,
 165     spa_request_length(&challenge));
 166
 167 if (auth_get_no64_data(&data, msgbuf) != OK)
 168   {
 169   /* something borked */
 170   return FAIL;
 171   }
 172
 173 /* dump client response */
 174 if (spa_base64_to_bits(CS (&response), sizeof(response), CCS (data)) < 0)
 175   {
 176   DEBUG(D_auth) debug_printf("auth_spa_server(): bad base64 data in "
 177   "response: %s\n", data);
 178   return FAIL;
 179   }
 180
 181 /***************************************************************
 182 PH 07-Aug-2003: The original code here was this:
 183
 184 Ustrcpy(msgbuf, unicodeToString(((char*)responseptr) +
 185   IVAL(&responseptr->uUser.offset,0),
 186   SVAL(&responseptr->uUser.len,0)/2) );
 187
 188 However, if the response data is too long, unicodeToString bombs out on
 189 an assertion failure. It uses a 1024 fixed buffer. Bombing out is not a good
 190 idea. It's too messy to try to rework that function to return an error because
 191 it is called from a number of other places in the auth-spa.c module. Instead,
 192 since it is a very small function, I reproduce its code here, with a size check
 193 that causes failure if the size of msgbuf is exceeded. ****/
 194
 195   {
 196   int i;
 197   char *p = ((char*)responseptr) + IVAL(&responseptr->uUser.offset,0);
 198   int len = SVAL(&responseptr->uUser.len,0)/2;
 199
 200   if (len + 1 >= sizeof(msgbuf)) return FAIL;
 201   for (i = 0; i < len; ++i)
 202     {
 203     msgbuf[i] = *p & 0x7f;
 204     p += 2;
 205     }
 206   msgbuf[i] = 0;
 207   }
 208
 209 /***************************************************************/
 210
 211 /* Put the username in $auth1 and $1. The former is now the preferred variable;
 212 the latter is the original variable. These have to be out of stack memory, and
 213 need to be available once known even if not authenticated, for error messages
 214 (server_set_id, which only makes it to authenticated_id if we return OK) */
 215
 216 auth_vars[0] = expand_nstring[1] = string_copy(msgbuf);
 217 expand_nlength[1] = Ustrlen(msgbuf);
 218 expand_nmax = 1;
 219
 220 debug_print_string(ablock->server_debug_string);    /* customized debug */
 221
 222 /* look up password */
 223
 224 clearpass = expand_string(ob->spa_serverpassword);
 225 if (clearpass == NULL)
 226   {
 227   if (f.expand_string_forcedfail)
 228     {
 229     DEBUG(D_auth) debug_printf("auth_spa_server(): forced failure while "
 230       "expanding spa_serverpassword\n");
 231     return FAIL;
 232     }
 233   else
 234     {
 235     DEBUG(D_auth) debug_printf("auth_spa_server(): error while expanding "
 236       "spa_serverpassword: %s\n", expand_string_message);
 237     return DEFER;
 238     }
 239   }
 240
 241 /* create local hash copy */
 242
 243 spa_smb_encrypt (clearpass, challenge.challengeData, lmRespData);
 244 spa_smb_nt_encrypt (clearpass, challenge.challengeData, ntRespData);
 245
 246 /* compare NT hash (LM may not be available) */
 247
 248 if (memcmp(ntRespData,
 249       ((unsigned char*)responseptr)+IVAL(&responseptr->ntResponse.offset,0),
 250       24) == 0)
 251   /* success. we have a winner. */
 252   {
 253   return auth_check_serv_cond(ablock);
 254   }
 255
 256   /* Expand server_condition as an authorization check (PH) */
 257
 258 return FAIL;
 259 }
 260
 261
 262 /*************************************************
 263 *              Client entry point                *
 264 *************************************************/
 265
 266 /* For interface, see auths/README */
 267
 268 int
 269 auth_spa_client(
 270   auth_instance *ablock,                 /* authenticator block */
 271   void * sx,                             /* connection */
 272   int timeout,                           /* command timeout */
 273   uschar *buffer,                        /* buffer for reading response */
 274   int buffsize)                          /* size of buffer */
 275 {
 276 auth_spa_options_block *ob =
 277        (auth_spa_options_block *)(ablock->options_block);
 278 SPAAuthRequest   request;
 279 SPAAuthChallenge challenge;
 280 SPAAuthResponse  response;
 281 char msgbuf[2048];
 282 char *domain = NULL;
 283 char *username, *password;
 284
 285 /* Code added by PH to expand the options */
 286
 287 *buffer = 0;    /* Default no message when cancelled */
 288
 289 if (!(username = CS expand_string(ob->spa_username)))
 290   {
 291   if (f.expand_string_forcedfail) return CANCELLED;
 292   string_format(buffer, buffsize, "expansion of \"%s\" failed in %s "
 293    "authenticator: %s", ob->spa_username, ablock->name,
 294    expand_string_message);
 295   return ERROR;
 296   }
 297
 298 if (!(password = CS expand_string(ob->spa_password)))
 299   {
 300   if (f.expand_string_forcedfail) return CANCELLED;
 301   string_format(buffer, buffsize, "expansion of \"%s\" failed in %s "
 302    "authenticator: %s", ob->spa_password, ablock->name,
 303    expand_string_message);
 304   return ERROR;
 305   }
 306
 307 if (ob->spa_domain)
 308   if (!(domain = CS expand_string(ob->spa_domain)))
 309     {
 310     if (f.expand_string_forcedfail) return CANCELLED;
 311     string_format(buffer, buffsize, "expansion of \"%s\" failed in %s "
 312                   "authenticator: %s", ob->spa_domain, ablock->name,
 313                   expand_string_message);
 314     return ERROR;
 315     }
 316
 317 /* Original code */
 318
 319 if (smtp_write_command(sx, SCMD_FLUSH, "AUTH %s\r\n", ablock->public_name) < 0)
 320   return FAIL_SEND;
 321
 322 /* wait for the 3XX OK message */
 323 if (!smtp_read_response(sx, US buffer, buffsize, '3', timeout))
 324   return FAIL;
 325
 326 DSPA("\n\n%s authenticator: using domain %s\n\n", ablock->name, domain);
 327
 328 spa_build_auth_request (&request, CS username, domain);
 329 spa_bits_to_base64 (US msgbuf, (unsigned char*)&request,
 330        spa_request_length(&request));
 331
 332 DSPA("\n\n%s authenticator: sending request (%s)\n\n", ablock->name, msgbuf);
 333
 334 /* send the encrypted password */
 335 if (smtp_write_command(sx, SCMD_FLUSH, "%s\r\n", msgbuf) < 0)
 336   return FAIL_SEND;
 337
 338 /* wait for the auth challenge */
 339 if (!smtp_read_response(sx, US buffer, buffsize, '3', timeout))
 340   return FAIL;
 341
 342 /* convert the challenge into the challenge struct */
 343 DSPA("\n\n%s authenticator: challenge (%s)\n\n", ablock->name, buffer + 4);
 344 spa_base64_to_bits (CS (&challenge), sizeof(challenge), CCS (buffer + 4));
 345
 346 spa_build_auth_response (&challenge, &response, CS username, CS password);
 347 spa_bits_to_base64 (US msgbuf, (unsigned char*)&response,
 348        spa_request_length(&response));
 349 DSPA("\n\n%s authenticator: challenge response (%s)\n\n", ablock->name, msgbuf);
 350
 351 /* send the challenge response */
 352 if (smtp_write_command(sx, SCMD_FLUSH, "%s\r\n", msgbuf) < 0)
 353        return FAIL_SEND;
 354
 355 /* If we receive a success response from the server, authentication
 356 has succeeded. There may be more data to send, but is there any point
 357 in provoking an error here? */
 358
 359 if (smtp_read_response(sx, US buffer, buffsize, '2', timeout))
 360   return OK;
 361
 362 /* Not a success response. If errno != 0 there is some kind of transmission
 363 error. Otherwise, check the response code in the buffer. If it starts with
 364 '3', more data is expected. */
 365
 366 if (errno != 0 || buffer[0] != '3')
 367   return FAIL;
 368
 369 return FAIL;
 370 }
 371
 372 #endif   /*!MACRO_PREDEF*/
 373 /* End of spa.c */