| 1 | /************************************************* |
| 2 | * Exim - an Internet mail transport agent * |
| 3 | *************************************************/ |
| 4 | |
| 5 | /* Copyright (c) The Exim Maintainers 2019 */ |
| 6 | /* Copyright (c) University of Cambridge 1995 - 2018 */ |
| 7 | /* See the file NOTICE for conditions of use and distribution. */ |
| 8 | |
| 9 | /* Copyright (c) Twitter Inc 2012 |
| 10 | Author: Phil Pennock <pdp@exim.org> */ |
| 11 | /* Copyright (c) Phil Pennock 2012 */ |
| 12 | |
| 13 | /* Interface to GNU SASL library for generic authentication. */ |
| 14 | |
| 15 | /* Trade-offs: |
| 16 | |
| 17 | GNU SASL does not provide authentication data itself, so we have to expose |
| 18 | that decision to configuration. For some mechanisms, we need to act much |
| 19 | like plaintext. For others, we only need to be able to provide some |
| 20 | evaluated data on demand. There's no abstracted way (ie, without hardcoding |
| 21 | knowledge of authenticators here) to know which need what properties; we |
| 22 | can't query a session or the library for "we will need these for mechanism X". |
| 23 | |
| 24 | So: we always require server_condition, even if sometimes it will just be |
| 25 | set as "yes". We do provide a number of other hooks, which might not make |
| 26 | sense in all contexts. For some, we can do checks at init time. |
| 27 | */ |
| 28 | |
| 29 | #include "../exim.h" |
| 30 | #define CHANNELBIND_HACK |
| 31 | |
| 32 | #ifndef AUTH_GSASL |
| 33 | /* dummy function to satisfy compilers when we link in an "empty" file. */ |
| 34 | static void dummy(int x); |
| 35 | static void dummy2(int x) { dummy(x-1); } |
| 36 | static void dummy(int x) { dummy2(x-1); } |
| 37 | #else |
| 38 | |
| 39 | #include <gsasl.h> |
| 40 | #include "gsasl_exim.h" |
| 41 | |
| 42 | |
| 43 | #if GSASL_VERSION_MINOR >= 9 |
| 44 | # define EXIM_GSASL_HAVE_SCRAM_SHA_256 |
| 45 | #endif |
| 46 | |
| 47 | |
| 48 | /* Authenticator-specific options. */ |
| 49 | /* I did have server_*_condition options for various mechanisms, but since |
| 50 | we only ever handle one mechanism at a time, I didn't see the point in keeping |
| 51 | that. In case someone sees a point, I've left the condition_check() API |
| 52 | alone. */ |
| 53 | optionlist auth_gsasl_options[] = { |
| 54 | { "client_authz", opt_stringptr, |
| 55 | (void *)(offsetof(auth_gsasl_options_block, client_authz)) }, |
| 56 | { "client_channelbinding", opt_bool, |
| 57 | (void *)(offsetof(auth_gsasl_options_block, client_channelbinding)) }, |
| 58 | { "client_password", opt_stringptr, |
| 59 | (void *)(offsetof(auth_gsasl_options_block, client_password)) }, |
| 60 | { "client_username", opt_stringptr, |
| 61 | (void *)(offsetof(auth_gsasl_options_block, client_username)) }, |
| 62 | |
| 63 | { "server_channelbinding", opt_bool, |
| 64 | (void *)(offsetof(auth_gsasl_options_block, server_channelbinding)) }, |
| 65 | { "server_hostname", opt_stringptr, |
| 66 | (void *)(offsetof(auth_gsasl_options_block, server_hostname)) }, |
| 67 | { "server_mech", opt_stringptr, |
| 68 | (void *)(offsetof(auth_gsasl_options_block, server_mech)) }, |
| 69 | { "server_password", opt_stringptr, |
| 70 | (void *)(offsetof(auth_gsasl_options_block, server_password)) }, |
| 71 | { "server_realm", opt_stringptr, |
| 72 | (void *)(offsetof(auth_gsasl_options_block, server_realm)) }, |
| 73 | { "server_scram_iter", opt_stringptr, |
| 74 | (void *)(offsetof(auth_gsasl_options_block, server_scram_iter)) }, |
| 75 | { "server_scram_salt", opt_stringptr, |
| 76 | (void *)(offsetof(auth_gsasl_options_block, server_scram_salt)) }, |
| 77 | { "server_service", opt_stringptr, |
| 78 | (void *)(offsetof(auth_gsasl_options_block, server_service)) } |
| 79 | }; |
| 80 | /* GSASL_SCRAM_SALTED_PASSWORD documented only for client, so not implementing |
| 81 | hooks to avoid cleartext passwords in the Exim server. */ |
| 82 | |
| 83 | int auth_gsasl_options_count = |
| 84 | sizeof(auth_gsasl_options)/sizeof(optionlist); |
| 85 | |
| 86 | /* Defaults for the authenticator-specific options. */ |
| 87 | auth_gsasl_options_block auth_gsasl_option_defaults = { |
| 88 | .server_service = US"smtp", |
| 89 | .server_hostname = US"$primary_hostname", |
| 90 | .server_scram_iter = US"4096", |
| 91 | /* all others zero/null */ |
| 92 | }; |
| 93 | |
| 94 | |
| 95 | #ifdef MACRO_PREDEF |
| 96 | |
| 97 | /* Dummy values */ |
| 98 | void auth_gsasl_init(auth_instance *ablock) {} |
| 99 | int auth_gsasl_server(auth_instance *ablock, uschar *data) {return 0;} |
| 100 | int auth_gsasl_client(auth_instance *ablock, void * sx, |
| 101 | int timeout, uschar *buffer, int buffsize) {return 0;} |
| 102 | void auth_gsasl_version_report(FILE *f) {} |
| 103 | |
| 104 | void |
| 105 | auth_gsasl_macros(void) |
| 106 | { |
| 107 | # ifdef EXIM_GSASL_HAVE_SCRAM_SHA_256 |
| 108 | builtin_macro_create(US"_HAVE_AUTH_GSASL_SCRAM_SHA_256"); |
| 109 | # endif |
| 110 | } |
| 111 | |
| 112 | #else /*!MACRO_PREDEF*/ |
| 113 | |
| 114 | |
| 115 | |
| 116 | /* "Globals" for managing the gsasl interface. */ |
| 117 | |
| 118 | static Gsasl *gsasl_ctx = NULL; |
| 119 | static int |
| 120 | main_callback(Gsasl *ctx, Gsasl_session *sctx, Gsasl_property prop); |
| 121 | static int |
| 122 | server_callback(Gsasl *ctx, Gsasl_session *sctx, Gsasl_property prop, auth_instance *ablock); |
| 123 | static int |
| 124 | client_callback(Gsasl *ctx, Gsasl_session *sctx, Gsasl_property prop, auth_instance *ablock); |
| 125 | |
| 126 | static BOOL sasl_error_should_defer = FALSE; |
| 127 | static Gsasl_property callback_loop = 0; |
| 128 | static BOOL checked_server_condition = FALSE; |
| 129 | |
| 130 | enum { CURRENTLY_SERVER = 1, CURRENTLY_CLIENT = 2 }; |
| 131 | |
| 132 | struct callback_exim_state { |
| 133 | auth_instance *ablock; |
| 134 | int currently; |
| 135 | }; |
| 136 | |
| 137 | |
| 138 | /************************************************* |
| 139 | * Initialization entry point * |
| 140 | *************************************************/ |
| 141 | |
| 142 | /* Called for each instance, after its options have been read, to |
| 143 | enable consistency checks to be done, or anything else that needs |
| 144 | to be set up. */ |
| 145 | |
| 146 | void |
| 147 | auth_gsasl_init(auth_instance *ablock) |
| 148 | { |
| 149 | static char * once = NULL; |
| 150 | int rc; |
| 151 | auth_gsasl_options_block *ob = |
| 152 | (auth_gsasl_options_block *)(ablock->options_block); |
| 153 | |
| 154 | /* As per existing Cyrus glue, use the authenticator's public name as |
| 155 | the default for the mechanism name; we don't handle multiple mechanisms |
| 156 | in one authenticator, but the same driver can be used multiple times. */ |
| 157 | |
| 158 | if (!ob->server_mech) |
| 159 | ob->server_mech = string_copy(ablock->public_name); |
| 160 | |
| 161 | /* Can get multiple session contexts from one library context, so just |
| 162 | initialise the once. */ |
| 163 | |
| 164 | if (!gsasl_ctx) |
| 165 | { |
| 166 | if ((rc = gsasl_init(&gsasl_ctx)) != GSASL_OK) |
| 167 | log_write(0, LOG_PANIC_DIE|LOG_CONFIG_FOR, "%s authenticator: " |
| 168 | "couldn't initialise GNU SASL library: %s (%s)", |
| 169 | ablock->name, gsasl_strerror_name(rc), gsasl_strerror(rc)); |
| 170 | |
| 171 | gsasl_callback_set(gsasl_ctx, main_callback); |
| 172 | } |
| 173 | |
| 174 | /* We don't need this except to log it for debugging. */ |
| 175 | |
| 176 | HDEBUG(D_auth) if (!once) |
| 177 | { |
| 178 | if ((rc = gsasl_server_mechlist(gsasl_ctx, &once)) != GSASL_OK) |
| 179 | log_write(0, LOG_PANIC_DIE|LOG_CONFIG_FOR, "%s authenticator: " |
| 180 | "failed to retrieve list of mechanisms: %s (%s)", |
| 181 | ablock->name, gsasl_strerror_name(rc), gsasl_strerror(rc)); |
| 182 | |
| 183 | debug_printf("GNU SASL supports: %s\n", once); |
| 184 | } |
| 185 | |
| 186 | if (!gsasl_client_support_p(gsasl_ctx, CCS ob->server_mech)) |
| 187 | log_write(0, LOG_PANIC_DIE|LOG_CONFIG_FOR, "%s authenticator: " |
| 188 | "GNU SASL does not support mechanism \"%s\"", |
| 189 | ablock->name, ob->server_mech); |
| 190 | |
| 191 | ablock->server = TRUE; |
| 192 | |
| 193 | if ( !ablock->server_condition |
| 194 | && ( streqic(ob->server_mech, US"EXTERNAL") |
| 195 | || streqic(ob->server_mech, US"ANONYMOUS") |
| 196 | || streqic(ob->server_mech, US"PLAIN") |
| 197 | || streqic(ob->server_mech, US"LOGIN") |
| 198 | ) ) |
| 199 | { |
| 200 | ablock->server = FALSE; |
| 201 | HDEBUG(D_auth) debug_printf("%s authenticator: " |
| 202 | "Need server_condition for %s mechanism\n", |
| 203 | ablock->name, ob->server_mech); |
| 204 | } |
| 205 | |
| 206 | /* This does *not* scale to new SASL mechanisms. Need a better way to ask |
| 207 | which properties will be needed. */ |
| 208 | |
| 209 | if ( !ob->server_realm |
| 210 | && streqic(ob->server_mech, US"DIGEST-MD5")) |
| 211 | { |
| 212 | ablock->server = FALSE; |
| 213 | HDEBUG(D_auth) debug_printf("%s authenticator: " |
| 214 | "Need server_realm for %s mechanism\n", |
| 215 | ablock->name, ob->server_mech); |
| 216 | } |
| 217 | |
| 218 | /* At present, for mechanisms we don't panic on absence of server_condition; |
| 219 | need to figure out the most generically correct approach to deciding when |
| 220 | it's critical and when it isn't. Eg, for simple validation (PLAIN mechanism, |
| 221 | etc) it clearly is critical. |
| 222 | */ |
| 223 | |
| 224 | ablock->client = ob->client_username && ob->client_password; |
| 225 | } |
| 226 | |
| 227 | |
| 228 | /* GNU SASL uses one top-level callback, registered at library level. |
| 229 | We dispatch to client and server functions instead. */ |
| 230 | |
| 231 | static int |
| 232 | main_callback(Gsasl *ctx, Gsasl_session *sctx, Gsasl_property prop) |
| 233 | { |
| 234 | int rc = 0; |
| 235 | struct callback_exim_state *cb_state = |
| 236 | (struct callback_exim_state *)gsasl_session_hook_get(sctx); |
| 237 | |
| 238 | if (!cb_state) |
| 239 | { |
| 240 | HDEBUG(D_auth) debug_printf("gsasl callback (%d) not from our server/client processing\n", prop); |
| 241 | #ifdef CHANNELBIND_HACK |
| 242 | if (prop == GSASL_CB_TLS_UNIQUE) |
| 243 | { |
| 244 | uschar * s; |
| 245 | if ((s = gsasl_callback_hook_get(ctx))) |
| 246 | { |
| 247 | HDEBUG(D_auth) debug_printf("GSASL_CB_TLS_UNIQUE from ctx hook\n"); |
| 248 | gsasl_property_set(sctx, GSASL_CB_TLS_UNIQUE, CS s); |
| 249 | } |
| 250 | else |
| 251 | { |
| 252 | HDEBUG(D_auth) debug_printf("GSASL_CB_TLS_UNIQUE! dummy for now\n"); |
| 253 | gsasl_property_set(sctx, GSASL_CB_TLS_UNIQUE, ""); |
| 254 | } |
| 255 | return GSASL_OK; |
| 256 | } |
| 257 | #endif |
| 258 | return GSASL_NO_CALLBACK; |
| 259 | } |
| 260 | |
| 261 | HDEBUG(D_auth) |
| 262 | debug_printf("GNU SASL Callback entered, prop=%d (loop prop=%d)\n", |
| 263 | prop, callback_loop); |
| 264 | |
| 265 | if (callback_loop > 0) |
| 266 | { |
| 267 | /* Most likely is that we were asked for property FOO, and to |
| 268 | expand the string we asked for property BAR to put into an auth |
| 269 | variable, but property BAR is not supplied for this mechanism. */ |
| 270 | HDEBUG(D_auth) |
| 271 | debug_printf("Loop, asked for property %d while handling property %d\n", |
| 272 | prop, callback_loop); |
| 273 | return GSASL_NO_CALLBACK; |
| 274 | } |
| 275 | callback_loop = prop; |
| 276 | |
| 277 | if (cb_state->currently == CURRENTLY_CLIENT) |
| 278 | rc = client_callback(ctx, sctx, prop, cb_state->ablock); |
| 279 | else if (cb_state->currently == CURRENTLY_SERVER) |
| 280 | rc = server_callback(ctx, sctx, prop, cb_state->ablock); |
| 281 | else |
| 282 | log_write(0, LOG_PANIC_DIE|LOG_CONFIG_FOR, "%s authenticator: " |
| 283 | "unhandled callback state, bug in Exim", cb_state->ablock->name); |
| 284 | /* NOTREACHED */ |
| 285 | |
| 286 | callback_loop = 0; |
| 287 | return rc; |
| 288 | } |
| 289 | |
| 290 | |
| 291 | /************************************************* |
| 292 | * Server entry point * |
| 293 | *************************************************/ |
| 294 | |
| 295 | /* For interface, see auths/README */ |
| 296 | |
| 297 | int |
| 298 | auth_gsasl_server(auth_instance *ablock, uschar *initial_data) |
| 299 | { |
| 300 | char *tmps; |
| 301 | char *to_send, *received; |
| 302 | Gsasl_session *sctx = NULL; |
| 303 | auth_gsasl_options_block *ob = |
| 304 | (auth_gsasl_options_block *)(ablock->options_block); |
| 305 | struct callback_exim_state cb_state; |
| 306 | int rc, auth_result, exim_error, exim_error_override; |
| 307 | |
| 308 | HDEBUG(D_auth) |
| 309 | debug_printf("GNU SASL: initialising session for %s, mechanism %s\n", |
| 310 | ablock->name, ob->server_mech); |
| 311 | |
| 312 | #ifndef DISABLE_TLS |
| 313 | if (tls_in.channelbinding && ob->server_channelbinding) |
| 314 | { |
| 315 | # ifdef EXPERIMENTAL_TLS_RESUME |
| 316 | if (!tls_in.ext_master_secret && tls_in.resumption == RESUME_USED) |
| 317 | { /* per RFC 7677 section 4 */ |
| 318 | HDEBUG(D_auth) debug_printf( |
| 319 | "channel binding not usable on resumed TLS without extended-master-secret"); |
| 320 | return FAIL; |
| 321 | } |
| 322 | # endif |
| 323 | # ifdef CHANNELBIND_HACK |
| 324 | /* This is a gross hack to get around the library a) requiring that |
| 325 | c-b was already set, at the _start() call, and b) caching a b64'd |
| 326 | version of the binding then which it never updates. */ |
| 327 | |
| 328 | gsasl_callback_hook_set(gsasl_ctx, tls_in.channelbinding); |
| 329 | # endif |
| 330 | } |
| 331 | #endif |
| 332 | |
| 333 | if ((rc = gsasl_server_start(gsasl_ctx, CCS ob->server_mech, &sctx)) != GSASL_OK) |
| 334 | { |
| 335 | auth_defer_msg = string_sprintf("GNU SASL: session start failure: %s (%s)", |
| 336 | gsasl_strerror_name(rc), gsasl_strerror(rc)); |
| 337 | HDEBUG(D_auth) debug_printf("%s\n", auth_defer_msg); |
| 338 | return DEFER; |
| 339 | } |
| 340 | /* Hereafter: gsasl_finish(sctx) please */ |
| 341 | |
| 342 | cb_state.ablock = ablock; |
| 343 | cb_state.currently = CURRENTLY_SERVER; |
| 344 | gsasl_session_hook_set(sctx, &cb_state); |
| 345 | |
| 346 | tmps = CS expand_string(ob->server_service); |
| 347 | gsasl_property_set(sctx, GSASL_SERVICE, tmps); |
| 348 | tmps = CS expand_string(ob->server_hostname); |
| 349 | gsasl_property_set(sctx, GSASL_HOSTNAME, tmps); |
| 350 | if (ob->server_realm) |
| 351 | { |
| 352 | tmps = CS expand_string(ob->server_realm); |
| 353 | if (tmps && *tmps) |
| 354 | gsasl_property_set(sctx, GSASL_REALM, tmps); |
| 355 | } |
| 356 | /* We don't support protection layers. */ |
| 357 | gsasl_property_set(sctx, GSASL_QOPS, "qop-auth"); |
| 358 | |
| 359 | #ifndef DISABLE_TLS |
| 360 | if (tls_in.channelbinding) |
| 361 | { |
| 362 | /* Some auth mechanisms can ensure that both sides are talking withing the |
| 363 | same security context; for TLS, this means that even if a bad certificate |
| 364 | has been accepted, they remain MitM-proof because both sides must be within |
| 365 | the same negotiated session; if someone is terminating one session and |
| 366 | proxying data on within a second, authentication will fail. |
| 367 | |
| 368 | We might not have this available, depending upon TLS implementation, |
| 369 | ciphersuite, phase of moon ... |
| 370 | |
| 371 | If we do, it results in extra SASL mechanisms being available; here, |
| 372 | Exim's one-mechanism-per-authenticator potentially causes problems. |
| 373 | It depends upon how GNU SASL will implement the PLUS variants of GS2 |
| 374 | and whether it automatically mandates a switch to the bound PLUS |
| 375 | if the data is available. Since default-on, despite being more secure, |
| 376 | would then result in mechanism name changes on a library update, we |
| 377 | have little choice but to default it off and let the admin choose to |
| 378 | enable it. *sigh* |
| 379 | */ |
| 380 | if (ob->server_channelbinding) |
| 381 | { |
| 382 | HDEBUG(D_auth) debug_printf("Auth %s: Enabling channel-binding\n", |
| 383 | ablock->name); |
| 384 | # ifndef CHANNELBIND_HACK |
| 385 | gsasl_property_set(sctx, GSASL_CB_TLS_UNIQUE, CCS tls_in.channelbinding); |
| 386 | # endif |
| 387 | } |
| 388 | else |
| 389 | HDEBUG(D_auth) |
| 390 | debug_printf("Auth %s: Not enabling channel-binding (data available)\n", |
| 391 | ablock->name); |
| 392 | } |
| 393 | else |
| 394 | HDEBUG(D_auth) |
| 395 | debug_printf("Auth %s: no channel-binding data available\n", |
| 396 | ablock->name); |
| 397 | #endif |
| 398 | |
| 399 | checked_server_condition = FALSE; |
| 400 | |
| 401 | received = CS initial_data; |
| 402 | to_send = NULL; |
| 403 | exim_error = exim_error_override = OK; |
| 404 | |
| 405 | do { |
| 406 | switch (rc = gsasl_step64(sctx, received, &to_send)) |
| 407 | { |
| 408 | case GSASL_OK: |
| 409 | if (!to_send) |
| 410 | goto STOP_INTERACTION; |
| 411 | break; |
| 412 | |
| 413 | case GSASL_NEEDS_MORE: |
| 414 | break; |
| 415 | |
| 416 | case GSASL_AUTHENTICATION_ERROR: |
| 417 | case GSASL_INTEGRITY_ERROR: |
| 418 | case GSASL_NO_AUTHID: |
| 419 | case GSASL_NO_ANONYMOUS_TOKEN: |
| 420 | case GSASL_NO_AUTHZID: |
| 421 | case GSASL_NO_PASSWORD: |
| 422 | case GSASL_NO_PASSCODE: |
| 423 | case GSASL_NO_PIN: |
| 424 | case GSASL_BASE64_ERROR: |
| 425 | HDEBUG(D_auth) debug_printf("GNU SASL permanent error: %s (%s)\n", |
| 426 | gsasl_strerror_name(rc), gsasl_strerror(rc)); |
| 427 | log_write(0, LOG_REJECT, "%s authenticator (%s):\n " |
| 428 | "GNU SASL permanent failure: %s (%s)", |
| 429 | ablock->name, ob->server_mech, |
| 430 | gsasl_strerror_name(rc), gsasl_strerror(rc)); |
| 431 | if (rc == GSASL_BASE64_ERROR) |
| 432 | exim_error_override = BAD64; |
| 433 | goto STOP_INTERACTION; |
| 434 | |
| 435 | default: |
| 436 | auth_defer_msg = string_sprintf("GNU SASL temporary error: %s (%s)", |
| 437 | gsasl_strerror_name(rc), gsasl_strerror(rc)); |
| 438 | HDEBUG(D_auth) debug_printf("%s\n", auth_defer_msg); |
| 439 | exim_error_override = DEFER; |
| 440 | goto STOP_INTERACTION; |
| 441 | } |
| 442 | |
| 443 | if ((rc == GSASL_NEEDS_MORE) || (to_send && *to_send)) |
| 444 | exim_error = auth_get_no64_data(USS &received, US to_send); |
| 445 | |
| 446 | if (to_send) |
| 447 | { |
| 448 | free(to_send); |
| 449 | to_send = NULL; |
| 450 | } |
| 451 | |
| 452 | if (exim_error) |
| 453 | break; /* handles * cancelled check */ |
| 454 | |
| 455 | } while (rc == GSASL_NEEDS_MORE); |
| 456 | |
| 457 | STOP_INTERACTION: |
| 458 | auth_result = rc; |
| 459 | |
| 460 | gsasl_finish(sctx); |
| 461 | |
| 462 | /* Can return: OK DEFER FAIL CANCELLED BAD64 UNEXPECTED */ |
| 463 | |
| 464 | if (exim_error != OK) |
| 465 | return exim_error; |
| 466 | |
| 467 | if (auth_result != GSASL_OK) |
| 468 | { |
| 469 | HDEBUG(D_auth) debug_printf("authentication returned %s (%s)\n", |
| 470 | gsasl_strerror_name(auth_result), gsasl_strerror(auth_result)); |
| 471 | if (exim_error_override != OK) |
| 472 | return exim_error_override; /* might be DEFER */ |
| 473 | if (sasl_error_should_defer) /* overriding auth failure SASL error */ |
| 474 | return DEFER; |
| 475 | return FAIL; |
| 476 | } |
| 477 | |
| 478 | /* Auth succeeded, check server_condition unless already done in callback */ |
| 479 | return checked_server_condition ? OK : auth_check_serv_cond(ablock); |
| 480 | } |
| 481 | |
| 482 | |
| 483 | /* returns the GSASL status of expanding the Exim string given */ |
| 484 | static int |
| 485 | condition_check(auth_instance *ablock, uschar *label, uschar *condition_string) |
| 486 | { |
| 487 | int exim_rc = auth_check_some_cond(ablock, label, condition_string, FAIL); |
| 488 | switch (exim_rc) |
| 489 | { |
| 490 | case OK: return GSASL_OK; |
| 491 | case DEFER: sasl_error_should_defer = TRUE; |
| 492 | return GSASL_AUTHENTICATION_ERROR; |
| 493 | case FAIL: return GSASL_AUTHENTICATION_ERROR; |
| 494 | default: log_write(0, LOG_PANIC_DIE|LOG_CONFIG_FOR, "%s authenticator: " |
| 495 | "Unhandled return from checking %s: %d", |
| 496 | ablock->name, label, exim_rc); |
| 497 | } |
| 498 | |
| 499 | /* NOTREACHED */ |
| 500 | return GSASL_AUTHENTICATION_ERROR; |
| 501 | } |
| 502 | |
| 503 | static int |
| 504 | server_callback(Gsasl *ctx, Gsasl_session *sctx, Gsasl_property prop, |
| 505 | auth_instance *ablock) |
| 506 | { |
| 507 | char *tmps; |
| 508 | uschar *propval; |
| 509 | int cbrc = GSASL_NO_CALLBACK; |
| 510 | auth_gsasl_options_block *ob = |
| 511 | (auth_gsasl_options_block *)(ablock->options_block); |
| 512 | |
| 513 | HDEBUG(D_auth) |
| 514 | debug_printf("GNU SASL callback %d for %s/%s as server\n", |
| 515 | prop, ablock->name, ablock->public_name); |
| 516 | |
| 517 | for (int i = 0; i < AUTH_VARS; i++) auth_vars[i] = NULL; |
| 518 | expand_nmax = 0; |
| 519 | |
| 520 | switch (prop) |
| 521 | { |
| 522 | case GSASL_VALIDATE_SIMPLE: |
| 523 | HDEBUG(D_auth) debug_printf(" VALIDATE_SIMPLE\n"); |
| 524 | /* GSASL_AUTHID, GSASL_AUTHZID, and GSASL_PASSWORD */ |
| 525 | propval = US gsasl_property_fast(sctx, GSASL_AUTHID); |
| 526 | auth_vars[0] = expand_nstring[1] = propval ? string_copy(propval) : US""; |
| 527 | propval = US gsasl_property_fast(sctx, GSASL_AUTHZID); |
| 528 | auth_vars[1] = expand_nstring[2] = propval ? string_copy(propval) : US""; |
| 529 | propval = US gsasl_property_fast(sctx, GSASL_PASSWORD); |
| 530 | auth_vars[2] = expand_nstring[3] = propval ? string_copy(propval) : US""; |
| 531 | expand_nmax = 3; |
| 532 | for (int i = 1; i <= 3; ++i) |
| 533 | expand_nlength[i] = Ustrlen(expand_nstring[i]); |
| 534 | |
| 535 | cbrc = condition_check(ablock, US"server_condition", ablock->server_condition); |
| 536 | checked_server_condition = TRUE; |
| 537 | break; |
| 538 | |
| 539 | case GSASL_VALIDATE_EXTERNAL: |
| 540 | HDEBUG(D_auth) debug_printf(" VALIDATE_EXTERNAL\n"); |
| 541 | if (!ablock->server_condition) |
| 542 | { |
| 543 | HDEBUG(D_auth) debug_printf("No server_condition supplied, to validate EXTERNAL\n"); |
| 544 | cbrc = GSASL_AUTHENTICATION_ERROR; |
| 545 | break; |
| 546 | } |
| 547 | propval = US gsasl_property_fast(sctx, GSASL_AUTHZID); |
| 548 | |
| 549 | /* We always set $auth1, even if only to empty string. */ |
| 550 | auth_vars[0] = expand_nstring[1] = propval ? string_copy(propval) : US""; |
| 551 | expand_nlength[1] = Ustrlen(expand_nstring[1]); |
| 552 | expand_nmax = 1; |
| 553 | |
| 554 | cbrc = condition_check(ablock, |
| 555 | US"server_condition (EXTERNAL)", ablock->server_condition); |
| 556 | checked_server_condition = TRUE; |
| 557 | break; |
| 558 | |
| 559 | case GSASL_VALIDATE_ANONYMOUS: |
| 560 | HDEBUG(D_auth) debug_printf(" VALIDATE_ANONYMOUS\n"); |
| 561 | if (!ablock->server_condition) |
| 562 | { |
| 563 | HDEBUG(D_auth) debug_printf("No server_condition supplied, to validate ANONYMOUS\n"); |
| 564 | cbrc = GSASL_AUTHENTICATION_ERROR; |
| 565 | break; |
| 566 | } |
| 567 | propval = US gsasl_property_fast(sctx, GSASL_ANONYMOUS_TOKEN); |
| 568 | |
| 569 | /* We always set $auth1, even if only to empty string. */ |
| 570 | |
| 571 | auth_vars[0] = expand_nstring[1] = propval ? string_copy(propval) : US""; |
| 572 | expand_nlength[1] = Ustrlen(expand_nstring[1]); |
| 573 | expand_nmax = 1; |
| 574 | |
| 575 | cbrc = condition_check(ablock, |
| 576 | US"server_condition (ANONYMOUS)", ablock->server_condition); |
| 577 | checked_server_condition = TRUE; |
| 578 | break; |
| 579 | |
| 580 | case GSASL_VALIDATE_GSSAPI: |
| 581 | HDEBUG(D_auth) debug_printf(" VALIDATE_GSSAPI\n"); |
| 582 | /* GSASL_AUTHZID and GSASL_GSSAPI_DISPLAY_NAME |
| 583 | The display-name is authenticated as part of GSS, the authzid is claimed |
| 584 | by the SASL integration after authentication; protected against tampering |
| 585 | (if the SASL mechanism supports that, which Kerberos does) but is |
| 586 | unverified, same as normal for other mechanisms. |
| 587 | First coding, we had these values swapped, but for consistency and prior |
| 588 | to the first release of Exim with this authenticator, they've been |
| 589 | switched to match the ordering of GSASL_VALIDATE_SIMPLE. */ |
| 590 | |
| 591 | propval = US gsasl_property_fast(sctx, GSASL_GSSAPI_DISPLAY_NAME); |
| 592 | auth_vars[0] = expand_nstring[1] = propval ? string_copy(propval) : US""; |
| 593 | propval = US gsasl_property_fast(sctx, GSASL_AUTHZID); |
| 594 | auth_vars[1] = expand_nstring[2] = propval ? string_copy(propval) : US""; |
| 595 | expand_nmax = 2; |
| 596 | for (int i = 1; i <= 2; ++i) |
| 597 | expand_nlength[i] = Ustrlen(expand_nstring[i]); |
| 598 | |
| 599 | /* In this one case, it perhaps makes sense to default back open? |
| 600 | But for consistency, let's just mandate server_condition here too. */ |
| 601 | |
| 602 | cbrc = condition_check(ablock, |
| 603 | US"server_condition (GSSAPI family)", ablock->server_condition); |
| 604 | checked_server_condition = TRUE; |
| 605 | break; |
| 606 | |
| 607 | case GSASL_SCRAM_ITER: |
| 608 | HDEBUG(D_auth) debug_printf(" SCRAM_ITER\n"); |
| 609 | if (ob->server_scram_iter) |
| 610 | { |
| 611 | tmps = CS expand_string(ob->server_scram_iter); |
| 612 | gsasl_property_set(sctx, GSASL_SCRAM_ITER, tmps); |
| 613 | cbrc = GSASL_OK; |
| 614 | } |
| 615 | break; |
| 616 | |
| 617 | case GSASL_SCRAM_SALT: |
| 618 | HDEBUG(D_auth) debug_printf(" SCRAM_SALT\n"); |
| 619 | if (ob->server_scram_iter) |
| 620 | { |
| 621 | tmps = CS expand_string(ob->server_scram_salt); |
| 622 | gsasl_property_set(sctx, GSASL_SCRAM_SALT, tmps); |
| 623 | cbrc = GSASL_OK; |
| 624 | } |
| 625 | break; |
| 626 | |
| 627 | case GSASL_PASSWORD: |
| 628 | HDEBUG(D_auth) debug_printf(" PASSWORD\n"); |
| 629 | /* DIGEST-MD5: GSASL_AUTHID, GSASL_AUTHZID and GSASL_REALM |
| 630 | CRAM-MD5: GSASL_AUTHID |
| 631 | PLAIN: GSASL_AUTHID and GSASL_AUTHZID |
| 632 | LOGIN: GSASL_AUTHID |
| 633 | */ |
| 634 | if (ob->server_scram_iter) |
| 635 | { |
| 636 | tmps = CS expand_string(ob->server_scram_iter); |
| 637 | gsasl_property_set(sctx, GSASL_SCRAM_ITER, tmps); |
| 638 | } |
| 639 | if (ob->server_scram_salt) |
| 640 | { |
| 641 | tmps = CS expand_string(ob->server_scram_salt); |
| 642 | gsasl_property_set(sctx, GSASL_SCRAM_SALT, tmps); |
| 643 | } |
| 644 | |
| 645 | /* Asking for GSASL_AUTHZID calls back into us if we use |
| 646 | gsasl_property_get(), thus the use of gsasl_property_fast(). |
| 647 | Do we really want to hardcode limits per mechanism? What happens when |
| 648 | a new mechanism is added to the library. It *shouldn't* result in us |
| 649 | needing to add more glue, since avoiding that is a large part of the |
| 650 | point of SASL. */ |
| 651 | |
| 652 | propval = US gsasl_property_fast(sctx, GSASL_AUTHID); |
| 653 | auth_vars[0] = expand_nstring[1] = propval ? string_copy(propval) : US""; |
| 654 | propval = US gsasl_property_fast(sctx, GSASL_AUTHZID); |
| 655 | auth_vars[1] = expand_nstring[2] = propval ? string_copy(propval) : US""; |
| 656 | propval = US gsasl_property_fast(sctx, GSASL_REALM); |
| 657 | auth_vars[2] = expand_nstring[3] = propval ? string_copy(propval) : US""; |
| 658 | expand_nmax = 3; |
| 659 | for (int i = 1; i <= 3; ++i) |
| 660 | expand_nlength[i] = Ustrlen(expand_nstring[i]); |
| 661 | |
| 662 | if (!ob->server_password) |
| 663 | break; |
| 664 | if (!(tmps = CS expand_string(ob->server_password))) |
| 665 | { |
| 666 | sasl_error_should_defer = f.expand_string_forcedfail ? FALSE : TRUE; |
| 667 | HDEBUG(D_auth) debug_printf("server_password expansion failed, so " |
| 668 | "can't tell GNU SASL library the password for %s\n", auth_vars[0]); |
| 669 | return GSASL_AUTHENTICATION_ERROR; |
| 670 | } |
| 671 | gsasl_property_set(sctx, GSASL_PASSWORD, tmps); |
| 672 | |
| 673 | /* This is inadequate; don't think Exim's store stacks are geared |
| 674 | for memory wiping, so expanding strings will leave stuff laying around. |
| 675 | But no need to compound the problem, so get rid of the one we can. */ |
| 676 | |
| 677 | memset(tmps, '\0', strlen(tmps)); |
| 678 | cbrc = GSASL_OK; |
| 679 | break; |
| 680 | |
| 681 | default: |
| 682 | HDEBUG(D_auth) debug_printf(" Unrecognised callback: %d\n", prop); |
| 683 | cbrc = GSASL_NO_CALLBACK; |
| 684 | } |
| 685 | |
| 686 | HDEBUG(D_auth) debug_printf("Returning %s (%s)\n", |
| 687 | gsasl_strerror_name(cbrc), gsasl_strerror(cbrc)); |
| 688 | |
| 689 | return cbrc; |
| 690 | } |
| 691 | |
| 692 | |
| 693 | /******************************************************************************/ |
| 694 | |
| 695 | #define PROP_OPTIONAL BIT(0) |
| 696 | |
| 697 | static BOOL |
| 698 | client_prop(Gsasl_session * sctx, Gsasl_property propnum, uschar * val, |
| 699 | const uschar * why, unsigned flags, uschar * buffer, int buffsize) |
| 700 | { |
| 701 | uschar * s; |
| 702 | int rc; |
| 703 | |
| 704 | if (flags & PROP_OPTIONAL && !val) return TRUE; |
| 705 | if (!(s = expand_string(val)) || !(flags & PROP_OPTIONAL) && !*s) |
| 706 | { |
| 707 | string_format(buffer, buffsize, "%s", expand_string_message); |
| 708 | return FALSE; |
| 709 | } |
| 710 | if (*s) gsasl_property_set(sctx, propnum, CS s); |
| 711 | return TRUE; |
| 712 | } |
| 713 | |
| 714 | /************************************************* |
| 715 | * Client entry point * |
| 716 | *************************************************/ |
| 717 | |
| 718 | /* For interface, see auths/README */ |
| 719 | |
| 720 | int |
| 721 | auth_gsasl_client( |
| 722 | auth_instance *ablock, /* authenticator block */ |
| 723 | void * sx, /* connection */ |
| 724 | int timeout, /* command timeout */ |
| 725 | uschar *buffer, /* buffer for reading response */ |
| 726 | int buffsize) /* size of buffer */ |
| 727 | { |
| 728 | auth_gsasl_options_block *ob = |
| 729 | (auth_gsasl_options_block *)(ablock->options_block); |
| 730 | Gsasl_session * sctx = NULL; |
| 731 | struct callback_exim_state cb_state; |
| 732 | uschar * s; |
| 733 | BOOL initial = TRUE; |
| 734 | int rc, yield = FAIL; |
| 735 | |
| 736 | HDEBUG(D_auth) |
| 737 | debug_printf("GNU SASL: initialising session for %s, mechanism %s\n", |
| 738 | ablock->name, ob->server_mech); |
| 739 | |
| 740 | *buffer = 0; |
| 741 | |
| 742 | #ifndef DISABLE_TLS |
| 743 | if (tls_out.channelbinding && ob->client_channelbinding) |
| 744 | { |
| 745 | # ifdef EXPERIMENTAL_TLS_RESUME |
| 746 | if (!tls_out.ext_master_secret && tls_out.resumption == RESUME_USED) |
| 747 | { /* per RFC 7677 section 4 */ |
| 748 | string_format(buffer, buffsize, "%s", |
| 749 | "channel binding not usable on resumed TLS without extended-master-secret"); |
| 750 | return FAIL; |
| 751 | } |
| 752 | # endif |
| 753 | # ifdef CHANNELBIND_HACK |
| 754 | /* This is a gross hack to get around the library a) requiring that |
| 755 | c-b was already set, at the _start() call, and b) caching a b64'd |
| 756 | version of the binding then which it never updates. */ |
| 757 | |
| 758 | gsasl_callback_hook_set(gsasl_ctx, tls_out.channelbinding); |
| 759 | # endif |
| 760 | } |
| 761 | #endif |
| 762 | |
| 763 | if ((rc = gsasl_client_start(gsasl_ctx, CCS ob->server_mech, &sctx)) != GSASL_OK) |
| 764 | { |
| 765 | string_format(buffer, buffsize, "GNU SASL: session start failure: %s (%s)", |
| 766 | gsasl_strerror_name(rc), gsasl_strerror(rc)); |
| 767 | HDEBUG(D_auth) debug_printf("%s\n", buffer); |
| 768 | return ERROR; |
| 769 | } |
| 770 | |
| 771 | cb_state.ablock = ablock; |
| 772 | cb_state.currently = CURRENTLY_CLIENT; |
| 773 | gsasl_session_hook_set(sctx, &cb_state); |
| 774 | |
| 775 | /* Set properties */ |
| 776 | |
| 777 | if ( !client_prop(sctx, GSASL_PASSWORD, ob->client_password, US"password", |
| 778 | 0, buffer, buffsize) |
| 779 | || !client_prop(sctx, GSASL_AUTHID, ob->client_username, US"username", |
| 780 | 0, buffer, buffsize) |
| 781 | || !client_prop(sctx, GSASL_AUTHZID, ob->client_authz, US"authz", |
| 782 | PROP_OPTIONAL, buffer, buffsize) |
| 783 | ) |
| 784 | return ERROR; |
| 785 | |
| 786 | #ifndef DISABLE_TLS |
| 787 | if (tls_out.channelbinding) |
| 788 | if (ob->client_channelbinding) |
| 789 | { |
| 790 | HDEBUG(D_auth) debug_printf("Auth %s: Enabling channel-binding\n", |
| 791 | ablock->name); |
| 792 | # ifndef CHANNELBIND_HACK |
| 793 | gsasl_property_set(sctx, GSASL_CB_TLS_UNIQUE, CCS tls_out.channelbinding); |
| 794 | # endif |
| 795 | } |
| 796 | else |
| 797 | HDEBUG(D_auth) |
| 798 | debug_printf("Auth %s: Not enabling channel-binding (data available)\n", |
| 799 | ablock->name); |
| 800 | #endif |
| 801 | |
| 802 | /* Run the SASL conversation with the server */ |
| 803 | |
| 804 | for(s = NULL; ;) |
| 805 | { |
| 806 | uschar * outstr; |
| 807 | BOOL fail; |
| 808 | |
| 809 | rc = gsasl_step64(sctx, CS s, CSS &outstr); |
| 810 | |
| 811 | fail = initial |
| 812 | ? smtp_write_command(sx, SCMD_FLUSH, |
| 813 | outstr ? "AUTH %s %s\r\n" : "AUTH %s\r\n", |
| 814 | ablock->public_name, outstr) <= 0 |
| 815 | : outstr |
| 816 | ? smtp_write_command(sx, SCMD_FLUSH, "%s\r\n", outstr) <= 0 |
| 817 | : FALSE; |
| 818 | if (outstr && *outstr) free(outstr); |
| 819 | if (fail) |
| 820 | { |
| 821 | yield = FAIL_SEND; |
| 822 | goto done; |
| 823 | } |
| 824 | initial = FALSE; |
| 825 | |
| 826 | if (rc != GSASL_NEEDS_MORE) |
| 827 | { |
| 828 | if (rc != GSASL_OK) |
| 829 | { |
| 830 | string_format(buffer, buffsize, "gsasl: %s", gsasl_strerror(rc)); |
| 831 | break; |
| 832 | } |
| 833 | |
| 834 | /* expecting a final 2xx from the server, accepting the AUTH */ |
| 835 | |
| 836 | if (smtp_read_response(sx, buffer, buffsize, '2', timeout)) |
| 837 | yield = OK; |
| 838 | break; /* from SASL sequence loop */ |
| 839 | } |
| 840 | |
| 841 | /* 2xx or 3xx response is acceptable. If 2xx, no further input */ |
| 842 | |
| 843 | if (!smtp_read_response(sx, buffer, buffsize, '3', timeout)) |
| 844 | if (errno == 0 && buffer[0] == '2') |
| 845 | buffer[4] = '\0'; |
| 846 | else |
| 847 | { |
| 848 | yield = FAIL; |
| 849 | goto done; |
| 850 | } |
| 851 | s = buffer + 4; |
| 852 | } |
| 853 | |
| 854 | done: |
| 855 | gsasl_finish(sctx); |
| 856 | return yield; |
| 857 | } |
| 858 | |
| 859 | static int |
| 860 | client_callback(Gsasl *ctx, Gsasl_session *sctx, Gsasl_property prop, auth_instance *ablock) |
| 861 | { |
| 862 | HDEBUG(D_auth) debug_printf("GNU SASL callback %d for %s/%s as client\n", |
| 863 | prop, ablock->name, ablock->public_name); |
| 864 | switch (prop) |
| 865 | { |
| 866 | case GSASL_AUTHZID: |
| 867 | HDEBUG(D_auth) debug_printf(" inquired for AUTHZID; not providing one\n"); |
| 868 | break; |
| 869 | case GSASL_SCRAM_SALTED_PASSWORD: |
| 870 | HDEBUG(D_auth) |
| 871 | debug_printf(" inquired for SCRAM_SALTED_PASSWORD; not providing one\n"); |
| 872 | break; |
| 873 | case GSASL_CB_TLS_UNIQUE: |
| 874 | HDEBUG(D_auth) |
| 875 | debug_printf(" inquired for CB_TLS_UNIQUE, filling in\n"); |
| 876 | gsasl_property_set(sctx, GSASL_CB_TLS_UNIQUE, CCS tls_out.channelbinding); |
| 877 | break; |
| 878 | } |
| 879 | return GSASL_NO_CALLBACK; |
| 880 | } |
| 881 | |
| 882 | /************************************************* |
| 883 | * Diagnostic API * |
| 884 | *************************************************/ |
| 885 | |
| 886 | void |
| 887 | auth_gsasl_version_report(FILE *f) |
| 888 | { |
| 889 | const char *runtime; |
| 890 | runtime = gsasl_check_version(NULL); |
| 891 | fprintf(f, "Library version: GNU SASL: Compile: %s\n" |
| 892 | " Runtime: %s\n", |
| 893 | GSASL_VERSION, runtime); |
| 894 | } |
| 895 | |
| 896 | |
| 897 | |
| 898 | /* Dummy */ |
| 899 | void auth_gsasl_macros(void) {} |
| 900 | |
| 901 | #endif /*!MACRO_PREDEF*/ |
| 902 | #endif /* AUTH_GSASL */ |
| 903 | |
| 904 | /* End of gsasl_exim.c */ |