| 1 | /* |
| 2 | * Copyright (c) 2004 Andrey Panin <pazke@donpac.ru> |
| 3 | * Copyright (c) 2006-2020 The Exim Maintainers |
| 4 | * |
| 5 | * This program is free software; you can redistribute it and/or modify |
| 6 | * it under the terms of the GNU General Public License as published |
| 7 | * by the Free Software Foundation; either version 2 of the License, or |
| 8 | * (at your option) any later version. |
| 9 | */ |
| 10 | |
| 11 | /* A number of modifications have been made to the original code. Originally I |
| 12 | commented them specially, but now they are getting quite extensive, so I have |
| 13 | ceased doing that. The biggest change is to use unbuffered I/O on the socket |
| 14 | because using C buffered I/O gives problems on some operating systems. PH */ |
| 15 | |
| 16 | /* Protocol specifications: |
| 17 | * Dovecot 1, protocol version 1.1 |
| 18 | * http://wiki.dovecot.org/Authentication%20Protocol |
| 19 | * |
| 20 | * Dovecot 2, protocol version 1.1 |
| 21 | * http://wiki2.dovecot.org/Design/AuthProtocol |
| 22 | */ |
| 23 | |
| 24 | #include "../exim.h" |
| 25 | #include "dovecot.h" |
| 26 | |
| 27 | #define VERSION_MAJOR 1 |
| 28 | #define VERSION_MINOR 0 |
| 29 | |
| 30 | /* http://wiki.dovecot.org/Authentication%20Protocol |
| 31 | "The maximum line length isn't defined, |
| 32 | but it's currently expected to fit into 8192 bytes" |
| 33 | */ |
| 34 | #define DOVECOT_AUTH_MAXLINELEN 8192 |
| 35 | |
| 36 | /* This was hard-coded as 8. |
| 37 | AUTH req C->S sends {"AUTH", id, mechanism, service } + params, 5 defined for |
| 38 | Dovecot 1; Dovecot 2 (same protocol version) defines 9. |
| 39 | |
| 40 | Master->Server sends {"USER", id, userid} + params, 6 defined. |
| 41 | Server->Client only gives {"OK", id} + params, unspecified, only 1 guaranteed. |
| 42 | |
| 43 | We only define here to accept S->C; max seen is 3+<unspecified>, plus the two |
| 44 | for the command and id, where unspecified might include _at least_ user=... |
| 45 | |
| 46 | So: allow for more fields than we ever expect to see, while aware that count |
| 47 | can go up without changing protocol version. |
| 48 | The cost is the length of an array of pointers on the stack. |
| 49 | */ |
| 50 | #define DOVECOT_AUTH_MAXFIELDCOUNT 16 |
| 51 | |
| 52 | /* Options specific to the authentication mechanism. */ |
| 53 | optionlist auth_dovecot_options[] = { |
| 54 | { "server_socket", opt_stringptr, OPT_OFF(auth_dovecot_options_block, server_socket) }, |
| 55 | /*{ "server_tls", opt_bool, OPT_OFF(auth_dovecot_options_block, server_tls) },*/ |
| 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_dovecot_options_count = nelem(auth_dovecot_options); |
| 62 | |
| 63 | /* Default private options block for the authentication method. */ |
| 64 | |
| 65 | auth_dovecot_options_block auth_dovecot_option_defaults = { |
| 66 | .server_socket = NULL, |
| 67 | /* .server_tls = FALSE,*/ |
| 68 | }; |
| 69 | |
| 70 | |
| 71 | |
| 72 | |
| 73 | #ifdef MACRO_PREDEF |
| 74 | |
| 75 | /* Dummy values */ |
| 76 | void auth_dovecot_init(auth_instance *ablock) {} |
| 77 | int auth_dovecot_server(auth_instance *ablock, uschar *data) {return 0;} |
| 78 | int auth_dovecot_client(auth_instance *ablock, void * sx, |
| 79 | int timeout, uschar *buffer, int buffsize) {return 0;} |
| 80 | |
| 81 | #else /*!MACRO_PREDEF*/ |
| 82 | |
| 83 | |
| 84 | /* Static variables for reading from the socket */ |
| 85 | |
| 86 | static uschar sbuffer[256]; |
| 87 | static int socket_buffer_left; |
| 88 | |
| 89 | |
| 90 | |
| 91 | /************************************************* |
| 92 | * Initialization entry point * |
| 93 | *************************************************/ |
| 94 | |
| 95 | /* Called for each instance, after its options have been read, to |
| 96 | enable consistency checks to be done, or anything else that needs |
| 97 | to be set up. */ |
| 98 | |
| 99 | void auth_dovecot_init(auth_instance *ablock) |
| 100 | { |
| 101 | auth_dovecot_options_block *ob = |
| 102 | (auth_dovecot_options_block *)(ablock->options_block); |
| 103 | |
| 104 | if (!ablock->public_name) ablock->public_name = ablock->name; |
| 105 | if (ob->server_socket) ablock->server = TRUE; |
| 106 | ablock->client = FALSE; |
| 107 | } |
| 108 | |
| 109 | /************************************************* |
| 110 | * "strcut" to split apart server lines * |
| 111 | *************************************************/ |
| 112 | |
| 113 | /* Dovecot auth protocol uses TAB \t as delimiter; a line consists |
| 114 | of a command-name, TAB, and then any parameters, each separated by a TAB. |
| 115 | A parameter can be param=value or a bool, just param. |
| 116 | |
| 117 | This function modifies the original str in-place, inserting NUL characters. |
| 118 | It initialises ptrs entries, setting all to NULL and only setting |
| 119 | non-NULL N entries, where N is the return value, the number of fields seen |
| 120 | (one more than the number of tabs). |
| 121 | |
| 122 | Note that the return value will always be at least 1, is the count of |
| 123 | actual fields (so last valid offset into ptrs is one less). |
| 124 | */ |
| 125 | |
| 126 | static int |
| 127 | strcut(uschar *str, uschar **ptrs, int nptrs) |
| 128 | { |
| 129 | uschar *last_sub_start = str; |
| 130 | int n; |
| 131 | |
| 132 | for (n = 0; n < nptrs; n++) |
| 133 | ptrs[n] = NULL; |
| 134 | n = 1; |
| 135 | |
| 136 | while (*str) |
| 137 | if (*str++ == '\t') |
| 138 | if (n++ <= nptrs) |
| 139 | { |
| 140 | *ptrs++ = last_sub_start; |
| 141 | last_sub_start = str; |
| 142 | str[-1] = '\0'; |
| 143 | } |
| 144 | |
| 145 | /* It's acceptable for the string to end with a tab character. We see |
| 146 | this in AUTH PLAIN without an initial response from the client, which |
| 147 | causing us to send "334 " and get the data from the client. */ |
| 148 | if (n <= nptrs) |
| 149 | *ptrs = last_sub_start; |
| 150 | else |
| 151 | { |
| 152 | HDEBUG(D_auth) |
| 153 | debug_printf("dovecot: warning: too many results from tab-splitting;" |
| 154 | " saw %d fields, room for %d\n", n, nptrs); |
| 155 | n = nptrs; |
| 156 | } |
| 157 | |
| 158 | return n <= nptrs ? n : nptrs; |
| 159 | } |
| 160 | |
| 161 | static void debug_strcut(uschar **ptrs, int nlen, int alen) ARG_UNUSED; |
| 162 | static void |
| 163 | debug_strcut(uschar **ptrs, int nlen, int alen) |
| 164 | { |
| 165 | int i; |
| 166 | debug_printf("%d read but unreturned bytes; strcut() gave %d results: ", |
| 167 | socket_buffer_left, nlen); |
| 168 | for (i = 0; i < nlen; i++) |
| 169 | debug_printf(" {%s}", ptrs[i]); |
| 170 | if (nlen < alen) |
| 171 | debug_printf(" last is %s\n", ptrs[i] ? ptrs[i] : US"<null>"); |
| 172 | else |
| 173 | debug_printf(" (max for capacity)\n"); |
| 174 | } |
| 175 | |
| 176 | #define CHECK_COMMAND(str, arg_min, arg_max) do { \ |
| 177 | if (strcmpic(US(str), args[0]) != 0) \ |
| 178 | goto out; \ |
| 179 | if (nargs - 1 < (arg_min)) \ |
| 180 | goto out; \ |
| 181 | if ( (arg_max != -1) && (nargs - 1 > (arg_max)) ) \ |
| 182 | goto out; \ |
| 183 | } while (0) |
| 184 | |
| 185 | #define OUT(msg) do { \ |
| 186 | auth_defer_msg = (US msg); \ |
| 187 | goto out; \ |
| 188 | } while(0) |
| 189 | |
| 190 | |
| 191 | |
| 192 | /************************************************* |
| 193 | * "fgets" to read directly from socket * |
| 194 | *************************************************/ |
| 195 | |
| 196 | /* Added by PH after a suggestion by Steve Usher because the previous use of |
| 197 | C-style buffered I/O gave trouble. */ |
| 198 | |
| 199 | static uschar * |
| 200 | dc_gets(uschar *s, int n, client_conn_ctx * cctx) |
| 201 | { |
| 202 | int p = 0; |
| 203 | int count = 0; |
| 204 | |
| 205 | for (;;) |
| 206 | { |
| 207 | if (socket_buffer_left == 0) |
| 208 | { |
| 209 | if ((socket_buffer_left = |
| 210 | #ifndef DISABLE_TLS |
| 211 | cctx->tls_ctx ? tls_read(cctx->tls_ctx, sbuffer, sizeof(sbuffer)) : |
| 212 | #endif |
| 213 | read(cctx->sock, sbuffer, sizeof(sbuffer))) <= 0) |
| 214 | if (count == 0) |
| 215 | return NULL; |
| 216 | else |
| 217 | break; |
| 218 | p = 0; |
| 219 | } |
| 220 | |
| 221 | while (p < socket_buffer_left) |
| 222 | { |
| 223 | if (count >= n - 1) break; |
| 224 | s[count++] = sbuffer[p]; |
| 225 | if (sbuffer[p++] == '\n') break; |
| 226 | } |
| 227 | |
| 228 | memmove(sbuffer, sbuffer + p, socket_buffer_left - p); |
| 229 | socket_buffer_left -= p; |
| 230 | |
| 231 | if (s[count-1] == '\n' || count >= n - 1) break; |
| 232 | } |
| 233 | |
| 234 | s[count] = '\0'; |
| 235 | return s; |
| 236 | } |
| 237 | |
| 238 | |
| 239 | |
| 240 | |
| 241 | /************************************************* |
| 242 | * Server entry point * |
| 243 | *************************************************/ |
| 244 | |
| 245 | int |
| 246 | auth_dovecot_server(auth_instance * ablock, uschar * data) |
| 247 | { |
| 248 | auth_dovecot_options_block *ob = |
| 249 | (auth_dovecot_options_block *) ablock->options_block; |
| 250 | uschar buffer[DOVECOT_AUTH_MAXLINELEN]; |
| 251 | uschar *args[DOVECOT_AUTH_MAXFIELDCOUNT]; |
| 252 | uschar *auth_command; |
| 253 | uschar *auth_extra_data = US""; |
| 254 | uschar *p; |
| 255 | int nargs, tmp; |
| 256 | int crequid = 1, ret = DEFER; |
| 257 | host_item host; |
| 258 | client_conn_ctx cctx = {.sock = -1, .tls_ctx = NULL}; |
| 259 | BOOL found = FALSE, have_mech_line = FALSE; |
| 260 | |
| 261 | HDEBUG(D_auth) debug_printf("dovecot authentication\n"); |
| 262 | |
| 263 | if (!data) |
| 264 | { |
| 265 | ret = FAIL; |
| 266 | goto out; |
| 267 | } |
| 268 | |
| 269 | /*XXX timeout? */ |
| 270 | cctx.sock = ip_streamsocket(ob->server_socket, &auth_defer_msg, 5, &host); |
| 271 | if (cctx.sock < 0) |
| 272 | goto out; |
| 273 | |
| 274 | #ifdef notdef |
| 275 | # ifndef DISABLE_TLS |
| 276 | if (ob->server_tls) |
| 277 | { |
| 278 | uschar * s; |
| 279 | smtp_connect_args conn_args = { .host = &host }; |
| 280 | tls_support tls_dummy = {.sni=NULL}; |
| 281 | uschar * errstr; |
| 282 | |
| 283 | if (!tls_client_start(&cctx, &conn_args, NULL, &tls_dummy, &errstr)) |
| 284 | { |
| 285 | auth_defer_msg = string_sprintf("TLS connect failed: %s", errstr); |
| 286 | goto out; |
| 287 | } |
| 288 | } |
| 289 | # endif |
| 290 | #endif |
| 291 | |
| 292 | auth_defer_msg = US"authentication socket protocol error"; |
| 293 | |
| 294 | socket_buffer_left = 0; /* Global, used to read more than a line but return by line */ |
| 295 | for (;;) |
| 296 | { |
| 297 | debug_printf("%s %d\n", __FUNCTION__, __LINE__); |
| 298 | if (!dc_gets(buffer, sizeof(buffer), &cctx)) |
| 299 | OUT("authentication socket read error or premature eof"); |
| 300 | debug_printf("%s %d\n", __FUNCTION__, __LINE__); |
| 301 | p = buffer + Ustrlen(buffer) - 1; |
| 302 | if (*p != '\n') |
| 303 | OUT("authentication socket protocol line too long"); |
| 304 | |
| 305 | *p = '\0'; |
| 306 | HDEBUG(D_auth) debug_printf("received: '%s'\n", buffer); |
| 307 | |
| 308 | nargs = strcut(buffer, args, nelem(args)); |
| 309 | |
| 310 | HDEBUG(D_auth) debug_strcut(args, nargs, nelem(args)); |
| 311 | |
| 312 | /* Code below rewritten by Kirill Miazine (km@krot.org). Only check commands that |
| 313 | Exim will need. Original code also failed if Dovecot server sent unknown |
| 314 | command. E.g. COOKIE in version 1.1 of the protocol would cause troubles. */ |
| 315 | /* pdp: note that CUID is a per-connection identifier sent by the server, |
| 316 | which increments at server discretion. |
| 317 | By contrast, the "id" field of the protocol is a connection-specific request |
| 318 | identifier, which needs to be unique per request from the client and is not |
| 319 | connected to the CUID value, so we ignore CUID from server. It's purely for |
| 320 | diagnostics. */ |
| 321 | |
| 322 | if (Ustrcmp(args[0], US"VERSION") == 0) |
| 323 | { |
| 324 | CHECK_COMMAND("VERSION", 2, 2); |
| 325 | if (Uatoi(args[1]) != VERSION_MAJOR) |
| 326 | OUT("authentication socket protocol version mismatch"); |
| 327 | } |
| 328 | else if (Ustrcmp(args[0], US"MECH") == 0) |
| 329 | { |
| 330 | CHECK_COMMAND("MECH", 1, INT_MAX); |
| 331 | have_mech_line = TRUE; |
| 332 | if (strcmpic(US args[1], ablock->public_name) == 0) |
| 333 | found = TRUE; |
| 334 | } |
| 335 | else if (Ustrcmp(args[0], US"SPID") == 0) |
| 336 | { |
| 337 | /* Unfortunately the auth protocol handshake wasn't designed well |
| 338 | to differentiate between auth-client/userdb/master. auth-userdb |
| 339 | and auth-master send VERSION + SPID lines only and nothing |
| 340 | afterwards, while auth-client sends VERSION + MECH + SPID + |
| 341 | CUID + more. The simplest way that we can determine if we've |
| 342 | connected to the correct socket is to see if MECH line exists or |
| 343 | not (alternatively we'd have to have a small timeout after SPID |
| 344 | to see if CUID is sent or not). */ |
| 345 | |
| 346 | if (!have_mech_line) |
| 347 | OUT("authentication socket type mismatch" |
| 348 | " (connected to auth-master instead of auth-client)"); |
| 349 | } |
| 350 | else if (Ustrcmp(args[0], US"DONE") == 0) |
| 351 | { |
| 352 | CHECK_COMMAND("DONE", 0, 0); |
| 353 | break; |
| 354 | } |
| 355 | } |
| 356 | |
| 357 | if (!found) |
| 358 | { |
| 359 | auth_defer_msg = string_sprintf( |
| 360 | "Dovecot did not advertise mechanism \"%s\" to us", ablock->public_name); |
| 361 | goto out; |
| 362 | } |
| 363 | |
| 364 | /* Added by PH: data must not contain tab (as it is |
| 365 | b64 it shouldn't, but check for safety). */ |
| 366 | |
| 367 | if (Ustrchr(data, '\t') != NULL) |
| 368 | { |
| 369 | ret = FAIL; |
| 370 | goto out; |
| 371 | } |
| 372 | |
| 373 | /* Added by PH: extra fields when TLS is in use or if the TCP/IP |
| 374 | connection is local. */ |
| 375 | |
| 376 | if (tls_in.cipher) |
| 377 | auth_extra_data = string_sprintf("secured\t%s%s", |
| 378 | tls_in.certificate_verified ? "valid-client-cert" : "", |
| 379 | tls_in.certificate_verified ? "\t" : ""); |
| 380 | |
| 381 | else if ( interface_address |
| 382 | && Ustrcmp(sender_host_address, interface_address) == 0) |
| 383 | auth_extra_data = US"secured\t"; |
| 384 | |
| 385 | |
| 386 | /**************************************************************************** |
| 387 | The code below was the original code here. It didn't work. A reading of the |
| 388 | file auth-protocol.txt.gz that came with Dovecot 1.0_beta8 indicated that |
| 389 | this was not right. Maybe something changed. I changed it to move the |
| 390 | service indication into the AUTH command, and it seems to be better. PH |
| 391 | |
| 392 | fprintf(f, "VERSION\t%d\t%d\r\nSERVICE\tSMTP\r\nCPID\t%d\r\n" |
| 393 | "AUTH\t%d\t%s\trip=%s\tlip=%s\tresp=%s\r\n", |
| 394 | VERSION_MAJOR, VERSION_MINOR, getpid(), cuid, |
| 395 | ablock->public_name, sender_host_address, interface_address, |
| 396 | data ? CS data : ""); |
| 397 | |
| 398 | Subsequently, the command was modified to add "secured" and "valid-client- |
| 399 | cert" when relevant. |
| 400 | ****************************************************************************/ |
| 401 | |
| 402 | auth_command = string_sprintf("VERSION\t%d\t%d\nCPID\t%d\n" |
| 403 | "AUTH\t%d\t%s\tservice=smtp\t%srip=%s\tlip=%s\tnologin\tresp=%s\n", |
| 404 | VERSION_MAJOR, VERSION_MINOR, getpid(), crequid, |
| 405 | ablock->public_name, auth_extra_data, sender_host_address, |
| 406 | interface_address, data); |
| 407 | |
| 408 | if (( |
| 409 | #ifndef DISABLE_TLS |
| 410 | cctx.tls_ctx ? tls_write(cctx.tls_ctx, auth_command, Ustrlen(auth_command), FALSE) : |
| 411 | #endif |
| 412 | write(cctx.sock, auth_command, Ustrlen(auth_command))) < 0) |
| 413 | HDEBUG(D_auth) debug_printf("error sending auth_command: %s\n", |
| 414 | strerror(errno)); |
| 415 | |
| 416 | HDEBUG(D_auth) debug_printf("sent: '%s'\n", auth_command); |
| 417 | |
| 418 | while (1) |
| 419 | { |
| 420 | uschar *temp; |
| 421 | uschar *auth_id_pre = NULL; |
| 422 | |
| 423 | if (!dc_gets(buffer, sizeof(buffer), &cctx)) |
| 424 | { |
| 425 | auth_defer_msg = US"authentication socket read error or premature eof"; |
| 426 | goto out; |
| 427 | } |
| 428 | |
| 429 | buffer[Ustrlen(buffer) - 1] = 0; |
| 430 | HDEBUG(D_auth) debug_printf("received: '%s'\n", buffer); |
| 431 | nargs = strcut(buffer, args, nelem(args)); |
| 432 | HDEBUG(D_auth) debug_strcut(args, nargs, nelem(args)); |
| 433 | |
| 434 | if (Uatoi(args[1]) != crequid) |
| 435 | OUT("authentication socket connection id mismatch"); |
| 436 | |
| 437 | switch (toupper(*args[0])) |
| 438 | { |
| 439 | case 'C': |
| 440 | CHECK_COMMAND("CONT", 1, 2); |
| 441 | |
| 442 | if ((tmp = auth_get_no64_data(&data, US args[2])) != OK) |
| 443 | { |
| 444 | ret = tmp; |
| 445 | goto out; |
| 446 | } |
| 447 | |
| 448 | /* Added by PH: data must not contain tab (as it is |
| 449 | b64 it shouldn't, but check for safety). */ |
| 450 | |
| 451 | if (Ustrchr(data, '\t') != NULL) |
| 452 | { |
| 453 | ret = FAIL; |
| 454 | goto out; |
| 455 | } |
| 456 | |
| 457 | temp = string_sprintf("CONT\t%d\t%s\n", crequid, data); |
| 458 | if (( |
| 459 | #ifndef DISABLE_TLS |
| 460 | cctx.tls_ctx ? tls_write(cctx.tls_ctx, temp, Ustrlen(temp), FALSE) : |
| 461 | #endif |
| 462 | write(cctx.sock, temp, Ustrlen(temp))) < 0) |
| 463 | OUT("authentication socket write error"); |
| 464 | break; |
| 465 | |
| 466 | case 'F': |
| 467 | CHECK_COMMAND("FAIL", 1, -1); |
| 468 | |
| 469 | for (int i = 2; i < nargs && !auth_id_pre; i++) |
| 470 | if (Ustrncmp(args[i], US"user=", 5) == 0) |
| 471 | { |
| 472 | auth_id_pre = args[i] + 5; |
| 473 | expand_nstring[1] = auth_vars[0] = string_copy(auth_id_pre); /* PH */ |
| 474 | expand_nlength[1] = Ustrlen(auth_id_pre); |
| 475 | expand_nmax = 1; |
| 476 | } |
| 477 | ret = FAIL; |
| 478 | goto out; |
| 479 | |
| 480 | case 'O': |
| 481 | CHECK_COMMAND("OK", 2, -1); |
| 482 | |
| 483 | /* Search for the "user=$USER" string in the args array |
| 484 | and return the proper value. */ |
| 485 | |
| 486 | for (int i = 2; i < nargs && !auth_id_pre; i++) |
| 487 | if (Ustrncmp(args[i], US"user=", 5) == 0) |
| 488 | { |
| 489 | auth_id_pre = args[i] + 5; |
| 490 | expand_nstring[1] = auth_vars[0] = string_copy(auth_id_pre); /* PH */ |
| 491 | expand_nlength[1] = Ustrlen(auth_id_pre); |
| 492 | expand_nmax = 1; |
| 493 | } |
| 494 | |
| 495 | if (!auth_id_pre) |
| 496 | OUT("authentication socket protocol error, username missing"); |
| 497 | |
| 498 | auth_defer_msg = NULL; |
| 499 | ret = OK; |
| 500 | /* fallthrough */ |
| 501 | |
| 502 | default: |
| 503 | goto out; |
| 504 | } |
| 505 | } |
| 506 | |
| 507 | out: |
| 508 | /* close the socket used by dovecot */ |
| 509 | #ifndef DISABLE_TLS |
| 510 | if (cctx.tls_ctx) |
| 511 | tls_close(cctx.tls_ctx, TRUE); |
| 512 | #endif |
| 513 | if (cctx.sock >= 0) |
| 514 | close(cctx.sock); |
| 515 | |
| 516 | /* Expand server_condition as an authorization check */ |
| 517 | return ret == OK ? auth_check_serv_cond(ablock) : ret; |
| 518 | } |
| 519 | |
| 520 | |
| 521 | #endif /*!MACRO_PREDEF*/ |