1 /* $NetBSD: postdrop.c,v 1.1.1.3 2011/07/31 10:02:46 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> 113 114 /* Utility library. */ 115 116 #include <msg.h> 117 #include <mymalloc.h> 118 #include <vstream.h> 119 #include <vstring.h> 120 #include <msg_vstream.h> 121 #include <msg_syslog.h> 122 #include <argv.h> 123 #include <iostuff.h> 124 #include <stringops.h> 125 126 /* Global library. */ 127 128 #include <mail_proto.h> 129 #include <mail_queue.h> 130 #include <mail_params.h> 131 #include <mail_version.h> 132 #include <mail_conf.h> 133 #include <mail_task.h> 134 #include <clean_env.h> 135 #include <mail_stream.h> 136 #include <cleanup_user.h> 137 #include <record.h> 138 #include <rec_type.h> 139 #include <user_acl.h> 140 #include <rec_attr_map.h> 141 142 /* Application-specific. */ 143 144 /* 145 * WARNING WARNING WARNING 146 * 147 * This software is designed to run set-gid. In order to avoid exploitation of 148 * privilege, this software should not run any external commands, nor should 149 * it take any information from the user unless that information can be 150 * properly sanitized. To get an idea of how much information a process can 151 * inherit from a potentially hostile user, examine all the members of the 152 * process structure (typically, in /usr/include/sys/proc.h): the current 153 * directory, open files, timers, signals, environment, command line, umask, 154 * and so on. 155 */ 156 157 /* 158 * Local mail submission access list. 159 */ 160 char *var_submit_acl; 161 162 static const CONFIG_STR_TABLE str_table[] = { 163 VAR_SUBMIT_ACL, DEF_SUBMIT_ACL, &var_submit_acl, 0, 0, 164 0, 165 }; 166 167 /* 168 * Queue file name. Global, so that the cleanup routine can find it when 169 * called by the run-time error handler. 170 */ 171 static char *postdrop_path; 172 173 /* postdrop_sig - catch signal and clean up */ 174 175 static void postdrop_sig(int sig) 176 { 177 178 /* 179 * This is the fatal error handler. Don't try to do anything fancy. 180 * 181 * msg_vstream does not allocate memory, but msg_syslog may indirectly in 182 * syslog(), so it should not be called from a user-triggered signal 183 * handler. 184 * 185 * Assume atomic signal() updates, even when emulated with sigaction(). We 186 * use the in-kernel SIGINT handler address as an atomic variable to 187 * prevent nested postdrop_sig() calls. For this reason, main() must 188 * configure postdrop_sig() as SIGINT handler before other signal 189 * handlers are allowed to invoke postdrop_sig(). 190 */ 191 if (signal(SIGINT, SIG_IGN) != SIG_IGN) { 192 (void) signal(SIGQUIT, SIG_IGN); 193 (void) signal(SIGTERM, SIG_IGN); 194 (void) signal(SIGHUP, SIG_IGN); 195 if (postdrop_path) { 196 (void) remove(postdrop_path); 197 postdrop_path = 0; 198 } 199 /* Future proofing. If you need exit() here then you broke Postfix. */ 200 if (sig) 201 _exit(sig); 202 } 203 } 204 205 /* postdrop_cleanup - callback for the runtime error handler */ 206 207 static void postdrop_cleanup(void) 208 { 209 postdrop_sig(0); 210 } 211 212 MAIL_VERSION_STAMP_DECLARE; 213 214 /* main - the main program */ 215 216 int main(int argc, char **argv) 217 { 218 struct stat st; 219 int fd; 220 int c; 221 VSTRING *buf; 222 int status; 223 MAIL_STREAM *dst; 224 int rec_type; 225 static char *segment_info[] = { 226 REC_TYPE_POST_ENVELOPE, REC_TYPE_POST_CONTENT, REC_TYPE_POST_EXTRACT, "" 227 }; 228 char **expected; 229 uid_t uid = getuid(); 230 ARGV *import_env; 231 const char *error_text; 232 char *attr_name; 233 char *attr_value; 234 const char *errstr; 235 char *junk; 236 struct timeval start; 237 int saved_errno; 238 int from_count = 0; 239 int rcpt_count = 0; 240 int validate_input = 1; 241 242 /* 243 * Fingerprint executables and core dumps. 244 */ 245 MAIL_VERSION_STAMP_ALLOCATE; 246 247 /* 248 * Be consistent with file permissions. 249 */ 250 umask(022); 251 252 /* 253 * To minimize confusion, make sure that the standard file descriptors 254 * are open before opening anything else. XXX Work around for 44BSD where 255 * fstat can return EBADF on an open file descriptor. 256 */ 257 for (fd = 0; fd < 3; fd++) 258 if (fstat(fd, &st) == -1 259 && (close(fd), open("/dev/null", O_RDWR, 0)) != fd) 260 msg_fatal("open /dev/null: %m"); 261 262 /* 263 * Set up logging. Censor the process name: it is provided by the user. 264 */ 265 argv[0] = "postdrop"; 266 msg_vstream_init(argv[0], VSTREAM_ERR); 267 msg_syslog_init(mail_task("postdrop"), LOG_PID, LOG_FACILITY); 268 set_mail_conf_str(VAR_PROCNAME, var_procname = mystrdup(argv[0])); 269 270 /* 271 * Parse JCL. This program is set-gid and must sanitize all command-line 272 * arguments. The configuration directory argument is validated by the 273 * mail configuration read routine. Don't do complex things until we have 274 * completed initializations. 275 */ 276 while ((c = GETOPT(argc, argv, "c:rv")) > 0) { 277 switch (c) { 278 case 'c': 279 if (setenv(CONF_ENV_PATH, optarg, 1) < 0) 280 msg_fatal("out of memory"); 281 break; 282 case 'r': /* forward compatibility */ 283 break; 284 case 'v': 285 if (geteuid() == 0) 286 msg_verbose++; 287 break; 288 default: 289 msg_fatal("usage: %s [-c config_dir] [-v]", argv[0]); 290 } 291 } 292 293 /* 294 * Read the global configuration file and extract configuration 295 * information. Some claim that the user should supply the working 296 * directory instead. That might be OK, given that this command needs 297 * write permission in a subdirectory called "maildrop". However we still 298 * need to reliably detect incomplete input, and so we must perform 299 * record-level I/O. With that, we should also take the opportunity to 300 * perform some sanity checks on the input. 301 */ 302 mail_conf_read(); 303 if (strcmp(var_syslog_name, DEF_SYSLOG_NAME) != 0) 304 msg_syslog_init(mail_task("postdrop"), LOG_PID, LOG_FACILITY); 305 get_mail_conf_str_table(str_table); 306 307 /* 308 * Mail submission access control. Should this be in the user-land gate, 309 * or in the daemon process? 310 */ 311 if ((errstr = check_user_acl_byuid(var_submit_acl, uid)) != 0) 312 msg_fatal("User %s(%ld) is not allowed to submit mail", 313 errstr, (long) uid); 314 315 /* 316 * Stop run-away process accidents by limiting the queue file size. This 317 * is not a defense against DOS attack. 318 */ 319 if (var_message_limit > 0 && get_file_limit() > var_message_limit) 320 set_file_limit((off_t) var_message_limit); 321 322 /* 323 * This program is installed with setgid privileges. Strip the process 324 * environment so that we don't have to trust the C library. 325 */ 326 import_env = argv_split(var_import_environ, ", \t\r\n"); 327 clean_env(import_env->argv); 328 argv_free(import_env); 329 330 if (chdir(var_queue_dir)) 331 msg_fatal("chdir %s: %m", var_queue_dir); 332 if (msg_verbose) 333 msg_info("chdir %s", var_queue_dir); 334 335 /* 336 * Set up signal handlers and a runtime error handler so that we can 337 * clean up incomplete output. 338 * 339 * postdrop_sig() uses the in-kernel SIGINT handler address as an atomic 340 * variable to prevent nested postdrop_sig() calls. For this reason, the 341 * SIGINT handler must be configured before other signal handlers are 342 * allowed to invoke postdrop_sig(). 343 */ 344 signal(SIGPIPE, SIG_IGN); 345 signal(SIGXFSZ, SIG_IGN); 346 347 signal(SIGINT, postdrop_sig); 348 signal(SIGQUIT, postdrop_sig); 349 if (signal(SIGTERM, SIG_IGN) == SIG_DFL) 350 signal(SIGTERM, postdrop_sig); 351 if (signal(SIGHUP, SIG_IGN) == SIG_DFL) 352 signal(SIGHUP, postdrop_sig); 353 msg_cleanup(postdrop_cleanup); 354 355 /* End of initializations. */ 356 357 /* 358 * Don't trust the caller's time information. 359 */ 360 GETTIMEOFDAY(&start); 361 362 /* 363 * Create queue file. mail_stream_file() never fails. Send the queue ID 364 * to the caller. Stash away a copy of the queue file name so we can 365 * clean up in case of a fatal error or an interrupt. 366 */ 367 dst = mail_stream_file(MAIL_QUEUE_MAILDROP, MAIL_CLASS_PUBLIC, 368 var_pickup_service, 0444); 369 attr_print(VSTREAM_OUT, ATTR_FLAG_NONE, 370 ATTR_TYPE_STR, MAIL_ATTR_QUEUEID, dst->id, 371 ATTR_TYPE_END); 372 vstream_fflush(VSTREAM_OUT); 373 postdrop_path = mystrdup(VSTREAM_PATH(dst->stream)); 374 375 /* 376 * Copy stdin to file. The format is checked so that we can recognize 377 * incomplete input and cancel the operation. With the sanity checks 378 * applied here, the pickup daemon could skip format checks and pass a 379 * file descriptor to the cleanup daemon. These are by no means all 380 * sanity checks - the cleanup service and queue manager services will 381 * reject messages that lack required information. 382 * 383 * If something goes wrong, slurp up the input before responding to the 384 * client, otherwise the client will give up after detecting SIGPIPE. 385 * 386 * Allow attribute records if the attribute specifies the MIME body type 387 * (sendmail -B). 388 */ 389 vstream_control(VSTREAM_IN, VSTREAM_CTL_PATH, "stdin", VSTREAM_CTL_END); 390 buf = vstring_alloc(100); 391 expected = segment_info; 392 /* Override time information from the untrusted caller. */ 393 rec_fprintf(dst->stream, REC_TYPE_TIME, REC_TYPE_TIME_FORMAT, 394 REC_TYPE_TIME_ARG(start)); 395 for (;;) { 396 /* Don't allow PTR records. */ 397 rec_type = rec_get_raw(VSTREAM_IN, buf, var_line_limit, REC_FLAG_NONE); 398 if (rec_type == REC_TYPE_EOF) { /* request cancelled */ 399 mail_stream_cleanup(dst); 400 if (remove(postdrop_path)) 401 msg_warn("uid=%ld: remove %s: %m", (long) uid, postdrop_path); 402 else if (msg_verbose) 403 msg_info("remove %s", postdrop_path); 404 myfree(postdrop_path); 405 postdrop_path = 0; 406 exit(0); 407 } 408 if (rec_type == REC_TYPE_ERROR) 409 msg_fatal("uid=%ld: malformed input", (long) uid); 410 if (strchr(*expected, rec_type) == 0) 411 msg_fatal("uid=%ld: unexpected record type: %d", (long) uid, rec_type); 412 if (rec_type == **expected) 413 expected++; 414 /* Override time information from the untrusted caller. */ 415 if (rec_type == REC_TYPE_TIME) 416 continue; 417 /* Check these at submission time instead of pickup time. */ 418 if (rec_type == REC_TYPE_FROM) 419 from_count++; 420 if (rec_type == REC_TYPE_RCPT) 421 rcpt_count++; 422 /* Limit the attribute types that users may specify. */ 423 if (rec_type == REC_TYPE_ATTR) { 424 if ((error_text = split_nameval(vstring_str(buf), &attr_name, 425 &attr_value)) != 0) { 426 msg_warn("uid=%ld: ignoring malformed record: %s: %.200s", 427 (long) uid, error_text, vstring_str(buf)); 428 continue; 429 } 430 #define STREQ(x,y) (strcmp(x,y) == 0) 431 432 if ((STREQ(attr_name, MAIL_ATTR_ENCODING) 433 && (STREQ(attr_value, MAIL_ATTR_ENC_7BIT) 434 || STREQ(attr_value, MAIL_ATTR_ENC_8BIT) 435 || STREQ(attr_value, MAIL_ATTR_ENC_NONE))) 436 || STREQ(attr_name, MAIL_ATTR_DSN_ENVID) 437 || STREQ(attr_name, MAIL_ATTR_DSN_NOTIFY) 438 || rec_attr_map(attr_name) 439 || (STREQ(attr_name, MAIL_ATTR_RWR_CONTEXT) 440 && (STREQ(attr_value, MAIL_ATTR_RWR_LOCAL) 441 || STREQ(attr_value, MAIL_ATTR_RWR_REMOTE))) 442 || STREQ(attr_name, MAIL_ATTR_TRACE_FLAGS)) { /* XXX */ 443 rec_fprintf(dst->stream, REC_TYPE_ATTR, "%s=%s", 444 attr_name, attr_value); 445 } else { 446 msg_warn("uid=%ld: ignoring attribute record: %.200s=%.200s", 447 (long) uid, attr_name, attr_value); 448 } 449 continue; 450 } 451 if (REC_PUT_BUF(dst->stream, rec_type, buf) < 0) { 452 /* rec_get() errors must not clobber errno. */ 453 saved_errno = errno; 454 while ((rec_type = rec_get_raw(VSTREAM_IN, buf, var_line_limit, 455 REC_FLAG_NONE)) != REC_TYPE_END 456 && rec_type != REC_TYPE_EOF) 457 if (rec_type == REC_TYPE_ERROR) 458 msg_fatal("uid=%ld: malformed input", (long) uid); 459 validate_input = 0; 460 errno = saved_errno; 461 break; 462 } 463 if (rec_type == REC_TYPE_END) 464 break; 465 } 466 vstring_free(buf); 467 468 /* 469 * As of Postfix 2.7 the pickup daemon discards mail without recipients. 470 * Such mail may enter the maildrop queue when "postsuper -r" is invoked 471 * before the queue manager deletes an already delivered message. Looking 472 * at file ownership is not a good way to make decisions on what mail to 473 * discard. Instead, the pickup server now requires that new submissions 474 * always have at least one recipient record. 475 * 476 * The Postfix sendmail command already rejects mail without recipients. 477 * However, in the future postdrop may receive mail via other programs, 478 * so we add a redundant recipient check here for future proofing. 479 * 480 * The test for the sender address is just for consistency of error 481 * reporting (report at submission time instead of pickup time). Besides 482 * the segment terminator records, there aren't any other mandatory 483 * records in a Postfix submission queue file. 484 */ 485 if (validate_input && (from_count == 0 || rcpt_count == 0)) { 486 status = CLEANUP_STAT_BAD; 487 mail_stream_cleanup(dst); 488 } 489 490 /* 491 * Finish the file. 492 */ 493 else if ((status = mail_stream_finish(dst, (VSTRING *) 0)) != 0) { 494 msg_warn("uid=%ld: %m", (long) uid); 495 postdrop_cleanup(); 496 } 497 498 /* 499 * Disable deletion on fatal error before reporting success, so the file 500 * will not be deleted after we have taken responsibility for delivery. 501 */ 502 if (postdrop_path) { 503 junk = postdrop_path; 504 postdrop_path = 0; 505 myfree(junk); 506 } 507 508 /* 509 * Send the completion status to the caller and terminate. 510 */ 511 attr_print(VSTREAM_OUT, ATTR_FLAG_NONE, 512 ATTR_TYPE_INT, MAIL_ATTR_STATUS, status, 513 ATTR_TYPE_STR, MAIL_ATTR_WHY, "", 514 ATTR_TYPE_END); 515 vstream_fflush(VSTREAM_OUT); 516 exit(status); 517 } 518