1 /* $NetBSD: postdrop.c,v 1.1.1.4 2013/01/02 18:59:03 tron Exp $ */ 2 3 /*++ 4 /* NAME 5 /* postdrop 1 6 /* SUMMARY 7 /* Postfix mail posting utility 8 /* SYNOPSIS 9 /* \fBpostdrop\fR [\fB-rv\fR] [\fB-c \fIconfig_dir\fR] 10 /* DESCRIPTION 11 /* The \fBpostdrop\fR(1) command creates a file in the \fBmaildrop\fR 12 /* directory and copies its standard input to the file. 13 /* 14 /* Options: 15 /* .IP "\fB-c \fIconfig_dir\fR" 16 /* The \fBmain.cf\fR configuration file is in the named directory 17 /* instead of the default configuration directory. See also the 18 /* MAIL_CONFIG environment setting below. 19 /* .IP \fB-r\fR 20 /* Use a Postfix-internal protocol for reading the message from 21 /* standard input, and for reporting status information on standard 22 /* output. This is currently the only supported method. 23 /* .IP \fB-v\fR 24 /* Enable verbose logging for debugging purposes. Multiple \fB-v\fR 25 /* options make the software increasingly verbose. As of Postfix 2.3, 26 /* this option is available for the super-user only. 27 /* SECURITY 28 /* .ad 29 /* .fi 30 /* The command is designed to run with set-group ID privileges, so 31 /* that it can write to the \fBmaildrop\fR queue directory and so that 32 /* it can connect to Postfix daemon processes. 33 /* DIAGNOSTICS 34 /* Fatal errors: malformed input, I/O error, out of memory. Problems 35 /* are logged to \fBsyslogd\fR(8) and to the standard error stream. 36 /* When the input is incomplete, or when the process receives a HUP, 37 /* INT, QUIT or TERM signal, the queue file is deleted. 38 /* ENVIRONMENT 39 /* .ad 40 /* .fi 41 /* .IP MAIL_CONFIG 42 /* Directory with the \fBmain.cf\fR file. In order to avoid exploitation 43 /* of set-group ID privileges, a non-standard directory is allowed only 44 /* if: 45 /* .RS 46 /* .IP \(bu 47 /* The name is listed in the standard \fBmain.cf\fR file with the 48 /* \fBalternate_config_directories\fR configuration parameter. 49 /* .IP \(bu 50 /* The command is invoked by the super-user. 51 /* .RE 52 /* CONFIGURATION PARAMETERS 53 /* .ad 54 /* .fi 55 /* The following \fBmain.cf\fR parameters are especially relevant to 56 /* this program. 57 /* The text below provides only a parameter summary. See 58 /* \fBpostconf\fR(5) for more details including examples. 59 /* .IP "\fBalternate_config_directories (empty)\fR" 60 /* A list of non-default Postfix configuration directories that may 61 /* be specified with "-c config_directory" on the command line, or 62 /* via the MAIL_CONFIG environment parameter. 63 /* .IP "\fBconfig_directory (see 'postconf -d' output)\fR" 64 /* The default location of the Postfix main.cf and master.cf 65 /* configuration files. 66 /* .IP "\fBimport_environment (see 'postconf -d' output)\fR" 67 /* The list of environment parameters that a Postfix process will 68 /* import from a non-Postfix parent process. 69 /* .IP "\fBqueue_directory (see 'postconf -d' output)\fR" 70 /* The location of the Postfix top-level queue directory. 71 /* .IP "\fBsyslog_facility (mail)\fR" 72 /* The syslog facility of Postfix logging. 73 /* .IP "\fBsyslog_name (see 'postconf -d' output)\fR" 74 /* The mail system name that is prepended to the process name in syslog 75 /* records, so that "smtpd" becomes, for example, "postfix/smtpd". 76 /* .IP "\fBtrigger_timeout (10s)\fR" 77 /* The time limit for sending a trigger to a Postfix daemon (for 78 /* example, the \fBpickup\fR(8) or \fBqmgr\fR(8) daemon). 79 /* .PP 80 /* Available in Postfix version 2.2 and later: 81 /* .IP "\fBauthorized_submit_users (static:anyone)\fR" 82 /* List of users who are authorized to submit mail with the \fBsendmail\fR(1) 83 /* command (and with the privileged \fBpostdrop\fR(1) helper command). 84 /* FILES 85 /* /var/spool/postfix/maildrop, maildrop queue 86 /* SEE ALSO 87 /* sendmail(1), compatibility interface 88 /* postconf(5), configuration parameters 89 /* syslogd(8), system logging 90 /* LICENSE 91 /* .ad 92 /* .fi 93 /* The Secure Mailer license must be distributed with this software. 94 /* AUTHOR(S) 95 /* Wietse Venema 96 /* IBM T.J. Watson Research 97 /* P.O. Box 704 98 /* Yorktown Heights, NY 10598, USA 99 /*--*/ 100 101 /* System library. */ 102 103 #include <sys_defs.h> 104 #include <sys/stat.h> 105 #include <unistd.h> 106 #include <stdlib.h> 107 #include <stdio.h> /* remove() */ 108 #include <string.h> 109 #include <stdlib.h> 110 #include <signal.h> 111 #include <syslog.h> 112 #include <errno.h> 113 #include <warn_stat.h> 114 115 /* Utility library. */ 116 117 #include <msg.h> 118 #include <mymalloc.h> 119 #include <vstream.h> 120 #include <vstring.h> 121 #include <msg_vstream.h> 122 #include <msg_syslog.h> 123 #include <argv.h> 124 #include <iostuff.h> 125 #include <stringops.h> 126 127 /* Global library. */ 128 129 #include <mail_proto.h> 130 #include <mail_queue.h> 131 #include <mail_params.h> 132 #include <mail_version.h> 133 #include <mail_conf.h> 134 #include <mail_task.h> 135 #include <clean_env.h> 136 #include <mail_stream.h> 137 #include <cleanup_user.h> 138 #include <record.h> 139 #include <rec_type.h> 140 #include <user_acl.h> 141 #include <rec_attr_map.h> 142 143 /* Application-specific. */ 144 145 /* 146 * WARNING WARNING WARNING 147 * 148 * This software is designed to run set-gid. In order to avoid exploitation of 149 * privilege, this software should not run any external commands, nor should 150 * it take any information from the user unless that information can be 151 * properly sanitized. To get an idea of how much information a process can 152 * inherit from a potentially hostile user, examine all the members of the 153 * process structure (typically, in /usr/include/sys/proc.h): the current 154 * directory, open files, timers, signals, environment, command line, umask, 155 * and so on. 156 */ 157 158 /* 159 * Local mail submission access list. 160 */ 161 char *var_submit_acl; 162 163 static const CONFIG_STR_TABLE str_table[] = { 164 VAR_SUBMIT_ACL, DEF_SUBMIT_ACL, &var_submit_acl, 0, 0, 165 0, 166 }; 167 168 /* 169 * Queue file name. Global, so that the cleanup routine can find it when 170 * called by the run-time error handler. 171 */ 172 static char *postdrop_path; 173 174 /* postdrop_sig - catch signal and clean up */ 175 176 static void postdrop_sig(int sig) 177 { 178 179 /* 180 * This is the fatal error handler. Don't try to do anything fancy. 181 * 182 * msg_vstream does not allocate memory, but msg_syslog may indirectly in 183 * syslog(), so it should not be called from a user-triggered signal 184 * handler. 185 * 186 * Assume atomic signal() updates, even when emulated with sigaction(). We 187 * use the in-kernel SIGINT handler address as an atomic variable to 188 * prevent nested postdrop_sig() calls. For this reason, main() must 189 * configure postdrop_sig() as SIGINT handler before other signal 190 * handlers are allowed to invoke postdrop_sig(). 191 */ 192 if (signal(SIGINT, SIG_IGN) != SIG_IGN) { 193 (void) signal(SIGQUIT, SIG_IGN); 194 (void) signal(SIGTERM, SIG_IGN); 195 (void) signal(SIGHUP, SIG_IGN); 196 if (postdrop_path) { 197 (void) remove(postdrop_path); 198 postdrop_path = 0; 199 } 200 /* Future proofing. If you need exit() here then you broke Postfix. */ 201 if (sig) 202 _exit(sig); 203 } 204 } 205 206 /* postdrop_cleanup - callback for the runtime error handler */ 207 208 static void postdrop_cleanup(void) 209 { 210 postdrop_sig(0); 211 } 212 213 MAIL_VERSION_STAMP_DECLARE; 214 215 /* main - the main program */ 216 217 int main(int argc, char **argv) 218 { 219 struct stat st; 220 int fd; 221 int c; 222 VSTRING *buf; 223 int status; 224 MAIL_STREAM *dst; 225 int rec_type; 226 static char *segment_info[] = { 227 REC_TYPE_POST_ENVELOPE, REC_TYPE_POST_CONTENT, REC_TYPE_POST_EXTRACT, "" 228 }; 229 char **expected; 230 uid_t uid = getuid(); 231 ARGV *import_env; 232 const char *error_text; 233 char *attr_name; 234 char *attr_value; 235 const char *errstr; 236 char *junk; 237 struct timeval start; 238 int saved_errno; 239 int from_count = 0; 240 int rcpt_count = 0; 241 int validate_input = 1; 242 243 /* 244 * Fingerprint executables and core dumps. 245 */ 246 MAIL_VERSION_STAMP_ALLOCATE; 247 248 /* 249 * Be consistent with file permissions. 250 */ 251 umask(022); 252 253 /* 254 * To minimize confusion, make sure that the standard file descriptors 255 * are open before opening anything else. XXX Work around for 44BSD where 256 * fstat can return EBADF on an open file descriptor. 257 */ 258 for (fd = 0; fd < 3; fd++) 259 if (fstat(fd, &st) == -1 260 && (close(fd), open("/dev/null", O_RDWR, 0)) != fd) 261 msg_fatal("open /dev/null: %m"); 262 263 /* 264 * Set up logging. Censor the process name: it is provided by the user. 265 */ 266 argv[0] = "postdrop"; 267 msg_vstream_init(argv[0], VSTREAM_ERR); 268 msg_syslog_init(mail_task("postdrop"), LOG_PID, LOG_FACILITY); 269 set_mail_conf_str(VAR_PROCNAME, var_procname = mystrdup(argv[0])); 270 271 /* 272 * Check the Postfix library version as soon as we enable logging. 273 */ 274 MAIL_VERSION_CHECK; 275 276 /* 277 * Parse JCL. This program is set-gid and must sanitize all command-line 278 * arguments. The configuration directory argument is validated by the 279 * mail configuration read routine. Don't do complex things until we have 280 * completed initializations. 281 */ 282 while ((c = GETOPT(argc, argv, "c:rv")) > 0) { 283 switch (c) { 284 case 'c': 285 if (setenv(CONF_ENV_PATH, optarg, 1) < 0) 286 msg_fatal("out of memory"); 287 break; 288 case 'r': /* forward compatibility */ 289 break; 290 case 'v': 291 if (geteuid() == 0) 292 msg_verbose++; 293 break; 294 default: 295 msg_fatal("usage: %s [-c config_dir] [-v]", argv[0]); 296 } 297 } 298 299 /* 300 * Read the global configuration file and extract configuration 301 * information. Some claim that the user should supply the working 302 * directory instead. That might be OK, given that this command needs 303 * write permission in a subdirectory called "maildrop". However we still 304 * need to reliably detect incomplete input, and so we must perform 305 * record-level I/O. With that, we should also take the opportunity to 306 * perform some sanity checks on the input. 307 */ 308 mail_conf_read(); 309 if (strcmp(var_syslog_name, DEF_SYSLOG_NAME) != 0) 310 msg_syslog_init(mail_task("postdrop"), LOG_PID, LOG_FACILITY); 311 get_mail_conf_str_table(str_table); 312 313 /* 314 * Mail submission access control. Should this be in the user-land gate, 315 * or in the daemon process? 316 */ 317 if ((errstr = check_user_acl_byuid(var_submit_acl, uid)) != 0) 318 msg_fatal("User %s(%ld) is not allowed to submit mail", 319 errstr, (long) uid); 320 321 /* 322 * Stop run-away process accidents by limiting the queue file size. This 323 * is not a defense against DOS attack. 324 */ 325 if (var_message_limit > 0 && get_file_limit() > var_message_limit) 326 set_file_limit((off_t) var_message_limit); 327 328 /* 329 * This program is installed with setgid privileges. Strip the process 330 * environment so that we don't have to trust the C library. 331 */ 332 import_env = argv_split(var_import_environ, ", \t\r\n"); 333 clean_env(import_env->argv); 334 argv_free(import_env); 335 336 if (chdir(var_queue_dir)) 337 msg_fatal("chdir %s: %m", var_queue_dir); 338 if (msg_verbose) 339 msg_info("chdir %s", var_queue_dir); 340 341 /* 342 * Set up signal handlers and a runtime error handler so that we can 343 * clean up incomplete output. 344 * 345 * postdrop_sig() uses the in-kernel SIGINT handler address as an atomic 346 * variable to prevent nested postdrop_sig() calls. For this reason, the 347 * SIGINT handler must be configured before other signal handlers are 348 * allowed to invoke postdrop_sig(). 349 */ 350 signal(SIGPIPE, SIG_IGN); 351 signal(SIGXFSZ, SIG_IGN); 352 353 signal(SIGINT, postdrop_sig); 354 signal(SIGQUIT, postdrop_sig); 355 if (signal(SIGTERM, SIG_IGN) == SIG_DFL) 356 signal(SIGTERM, postdrop_sig); 357 if (signal(SIGHUP, SIG_IGN) == SIG_DFL) 358 signal(SIGHUP, postdrop_sig); 359 msg_cleanup(postdrop_cleanup); 360 361 /* End of initializations. */ 362 363 /* 364 * Don't trust the caller's time information. 365 */ 366 GETTIMEOFDAY(&start); 367 368 /* 369 * Create queue file. mail_stream_file() never fails. Send the queue ID 370 * to the caller. Stash away a copy of the queue file name so we can 371 * clean up in case of a fatal error or an interrupt. 372 */ 373 dst = mail_stream_file(MAIL_QUEUE_MAILDROP, MAIL_CLASS_PUBLIC, 374 var_pickup_service, 0444); 375 attr_print(VSTREAM_OUT, ATTR_FLAG_NONE, 376 ATTR_TYPE_STR, MAIL_ATTR_QUEUEID, dst->id, 377 ATTR_TYPE_END); 378 vstream_fflush(VSTREAM_OUT); 379 postdrop_path = mystrdup(VSTREAM_PATH(dst->stream)); 380 381 /* 382 * Copy stdin to file. The format is checked so that we can recognize 383 * incomplete input and cancel the operation. With the sanity checks 384 * applied here, the pickup daemon could skip format checks and pass a 385 * file descriptor to the cleanup daemon. These are by no means all 386 * sanity checks - the cleanup service and queue manager services will 387 * reject messages that lack required information. 388 * 389 * If something goes wrong, slurp up the input before responding to the 390 * client, otherwise the client will give up after detecting SIGPIPE. 391 * 392 * Allow attribute records if the attribute specifies the MIME body type 393 * (sendmail -B). 394 */ 395 vstream_control(VSTREAM_IN, VSTREAM_CTL_PATH, "stdin", VSTREAM_CTL_END); 396 buf = vstring_alloc(100); 397 expected = segment_info; 398 /* Override time information from the untrusted caller. */ 399 rec_fprintf(dst->stream, REC_TYPE_TIME, REC_TYPE_TIME_FORMAT, 400 REC_TYPE_TIME_ARG(start)); 401 for (;;) { 402 /* Don't allow PTR records. */ 403 rec_type = rec_get_raw(VSTREAM_IN, buf, var_line_limit, REC_FLAG_NONE); 404 if (rec_type == REC_TYPE_EOF) { /* request cancelled */ 405 mail_stream_cleanup(dst); 406 if (remove(postdrop_path)) 407 msg_warn("uid=%ld: remove %s: %m", (long) uid, postdrop_path); 408 else if (msg_verbose) 409 msg_info("remove %s", postdrop_path); 410 myfree(postdrop_path); 411 postdrop_path = 0; 412 exit(0); 413 } 414 if (rec_type == REC_TYPE_ERROR) 415 msg_fatal("uid=%ld: malformed input", (long) uid); 416 if (strchr(*expected, rec_type) == 0) 417 msg_fatal("uid=%ld: unexpected record type: %d", (long) uid, rec_type); 418 if (rec_type == **expected) 419 expected++; 420 /* Override time information from the untrusted caller. */ 421 if (rec_type == REC_TYPE_TIME) 422 continue; 423 /* Check these at submission time instead of pickup time. */ 424 if (rec_type == REC_TYPE_FROM) 425 from_count++; 426 if (rec_type == REC_TYPE_RCPT) 427 rcpt_count++; 428 /* Limit the attribute types that users may specify. */ 429 if (rec_type == REC_TYPE_ATTR) { 430 if ((error_text = split_nameval(vstring_str(buf), &attr_name, 431 &attr_value)) != 0) { 432 msg_warn("uid=%ld: ignoring malformed record: %s: %.200s", 433 (long) uid, error_text, vstring_str(buf)); 434 continue; 435 } 436 #define STREQ(x,y) (strcmp(x,y) == 0) 437 438 if ((STREQ(attr_name, MAIL_ATTR_ENCODING) 439 && (STREQ(attr_value, MAIL_ATTR_ENC_7BIT) 440 || STREQ(attr_value, MAIL_ATTR_ENC_8BIT) 441 || STREQ(attr_value, MAIL_ATTR_ENC_NONE))) 442 || STREQ(attr_name, MAIL_ATTR_DSN_ENVID) 443 || STREQ(attr_name, MAIL_ATTR_DSN_NOTIFY) 444 || rec_attr_map(attr_name) 445 || (STREQ(attr_name, MAIL_ATTR_RWR_CONTEXT) 446 && (STREQ(attr_value, MAIL_ATTR_RWR_LOCAL) 447 || STREQ(attr_value, MAIL_ATTR_RWR_REMOTE))) 448 || STREQ(attr_name, MAIL_ATTR_TRACE_FLAGS)) { /* XXX */ 449 rec_fprintf(dst->stream, REC_TYPE_ATTR, "%s=%s", 450 attr_name, attr_value); 451 } else { 452 msg_warn("uid=%ld: ignoring attribute record: %.200s=%.200s", 453 (long) uid, attr_name, attr_value); 454 } 455 continue; 456 } 457 if (REC_PUT_BUF(dst->stream, rec_type, buf) < 0) { 458 /* rec_get() errors must not clobber errno. */ 459 saved_errno = errno; 460 while ((rec_type = rec_get_raw(VSTREAM_IN, buf, var_line_limit, 461 REC_FLAG_NONE)) != REC_TYPE_END 462 && rec_type != REC_TYPE_EOF) 463 if (rec_type == REC_TYPE_ERROR) 464 msg_fatal("uid=%ld: malformed input", (long) uid); 465 validate_input = 0; 466 errno = saved_errno; 467 break; 468 } 469 if (rec_type == REC_TYPE_END) 470 break; 471 } 472 vstring_free(buf); 473 474 /* 475 * As of Postfix 2.7 the pickup daemon discards mail without recipients. 476 * Such mail may enter the maildrop queue when "postsuper -r" is invoked 477 * before the queue manager deletes an already delivered message. Looking 478 * at file ownership is not a good way to make decisions on what mail to 479 * discard. Instead, the pickup server now requires that new submissions 480 * always have at least one recipient record. 481 * 482 * The Postfix sendmail command already rejects mail without recipients. 483 * However, in the future postdrop may receive mail via other programs, 484 * so we add a redundant recipient check here for future proofing. 485 * 486 * The test for the sender address is just for consistency of error 487 * reporting (report at submission time instead of pickup time). Besides 488 * the segment terminator records, there aren't any other mandatory 489 * records in a Postfix submission queue file. 490 */ 491 if (validate_input && (from_count == 0 || rcpt_count == 0)) { 492 status = CLEANUP_STAT_BAD; 493 mail_stream_cleanup(dst); 494 } 495 496 /* 497 * Finish the file. 498 */ 499 else if ((status = mail_stream_finish(dst, (VSTRING *) 0)) != 0) { 500 msg_warn("uid=%ld: %m", (long) uid); 501 postdrop_cleanup(); 502 } 503 504 /* 505 * Disable deletion on fatal error before reporting success, so the file 506 * will not be deleted after we have taken responsibility for delivery. 507 */ 508 if (postdrop_path) { 509 junk = postdrop_path; 510 postdrop_path = 0; 511 myfree(junk); 512 } 513 514 /* 515 * Send the completion status to the caller and terminate. 516 */ 517 attr_print(VSTREAM_OUT, ATTR_FLAG_NONE, 518 ATTR_TYPE_INT, MAIL_ATTR_STATUS, status, 519 ATTR_TYPE_STR, MAIL_ATTR_WHY, "", 520 ATTR_TYPE_END); 521 vstream_fflush(VSTREAM_OUT); 522 exit(status); 523 } 524