/*++ /* NAME /* verify 8 /* SUMMARY /* Postfix address verification server /* SYNOPSIS /* \fBverify\fR [generic Postfix daemon options] /* DESCRIPTION /* The Postfix address verification server maintains a record /* of what recipient addresses are known to be deliverable or /* undeliverable. /* /* Addresses are verified by injecting probe messages into the /* Postfix queue. Probe messages are run through all the routing /* and rewriting machinery except for final delivery, and are /* discarded rather than being deferred or bounced. /* /* Address verification relies on the answer from the nearest /* MTA for the specified address, and will therefore not detect /* all undeliverable addresses. /* /* This server is designed to run under control by the Postfix /* master server. It maintains an optional persistent database. /* To avoid being interrupted by "postfix stop" in the middle /* of a database update, the process runs in a separate process /* group. /* /* This server implements the following requests: /* .IP "\fBupdate\fI address status text\fR" /* Update the status and text of the specified address. /* .IP "\fBquery\fI address\fR" /* Look up the \fIstatus\fR and \fItext\fR for the specified address. /* If the status is unknown, a probe is sent and an "in progress" /* status is returned. /* SECURITY /* .ad /* .fi /* The address verification server is not security-sensitive. It does /* not talk to the network, and it does not talk to local users. /* The verify server can run chrooted at fixed low privilege. /* /* The address verification server can be coerced to store /* unlimited amounts of garbage. Limiting the cache size /* trades one problem (disk space exhaustion) for another /* one (poor response time to client requests). /* DIAGNOSTICS /* Problems and transactions are logged to \fBsyslogd\fR(8). /* BUGS /* The address verification service is suitable only for sites that /* handle a low mail volume. Verification probes add additional /* traffic to the mail queue and perform poorly under high load. /* Servers may blacklist sites that probe excessively, or that /* probe excessively for non-existent recipient addresses. /* /* If the persistent database ever gets corrupted then the world /* comes to an end and human intervention is needed. This violates /* a basic Postfix principle. /* CONFIGURATION PARAMETERS /* .ad /* .fi /* Changes to \fBmain.cf\fR are not picked up automatically, as verify(8) /* processes are persistent. Use the command "\fBpostfix reload\fR" after /* a configuration change. /* /* The text below provides only a parameter summary. See /* postconf(5) for more details including examples. /* CACHE CONTROLS /* .ad /* .fi /* .IP "\fBaddress_verify_map (empty)\fR" /* Optional lookup table for persistent address verification status /* storage. /* .IP "\fBaddress_verify_sender (postmaster)\fR" /* The sender address to use in address verification probes. /* .IP "\fBaddress_verify_positive_expire_time (31d)\fR" /* The time after which a successful probe expires from the address /* verification cache. /* .IP "\fBaddress_verify_positive_refresh_time (7d)\fR" /* The time after which a successful address verification probe needs /* to be refreshed. /* .IP "\fBaddress_verify_negative_cache (yes)\fR" /* Enable caching of failed address verification probe results. /* .IP "\fBaddress_verify_negative_expire_time (3d)\fR" /* The time after which a failed probe expires from the address /* verification cache. /* .IP "\fBaddress_verify_negative_refresh_time (3h)\fR" /* The time after which a failed address verification probe needs to /* be refreshed. /* PROBE MESSAGE ROUTING CONTROLS /* .ad /* .fi /* By default, probe messages are delivered via the same route /* as regular messages. The following parameters can be used to /* override specific message routing mechanisms. /* .IP "\fBaddress_verify_relayhost ($relayhost)\fR" /* Overrides the relayhost parameter setting for address verification /* probes. /* .IP "\fBaddress_verify_transport_maps ($transport_maps)\fR" /* Overrides the transport_maps parameter setting for address verification /* probes. /* .IP "\fBaddress_verify_local_transport ($local_transport)\fR" /* Overrides the local_transport parameter setting for address /* verification probes. /* .IP "\fBaddress_verify_virtual_transport ($virtual_transport)\fR" /* Overrides the virtual_transport parameter setting for address /* verification probes. /* .IP "\fBaddress_verify_relay_transport ($relay_transport)\fR" /* Overrides the relay_transport parameter setting for address /* verification probes. /* .IP "\fBaddress_verify_default_transport ($default_transport)\fR" /* Overrides the default_transport parameter setting for address /* verification probes. /* MISCELLANEOUS CONTROLS /* .ad /* .fi /* .IP "\fBconfig_directory (see 'postconf -d' output)\fR" /* The default location of the Postfix main.cf and master.cf /* configuration files. /* .IP "\fBdaemon_timeout (18000s)\fR" /* How much time a Postfix daemon process may take to handle a /* request before it is terminated by a built-in watchdog timer. /* .IP "\fBipc_timeout (3600s)\fR" /* The time limit for sending or receiving information over an internal /* communication channel. /* .IP "\fBprocess_id (read-only)\fR" /* The process ID of a Postfix command or daemon process. /* .IP "\fBprocess_name (read-only)\fR" /* The process name of a Postfix command or daemon process. /* .IP "\fBqueue_directory (see 'postconf -d' output)\fR" /* The location of the Postfix top-level queue directory. /* .IP "\fBsyslog_facility (mail)\fR" /* The syslog facility of Postfix logging. /* .IP "\fBsyslog_name (postfix)\fR" /* The mail system name that is prepended to the process name in syslog /* records, so that "smtpd" becomes, for example, "postfix/smtpd". /* SEE ALSO /* smtpd(8), Postfix SMTP server /* cleanup(8), enqueue Postfix message /* postconf(5), configuration parameters /* syslogd(5), system logging /* README FILES /* .ad /* .fi /* Use "\fBpostconf readme_directory\fR" or /* "\fBpostconf html_directory\fR" to locate this information. /* .na /* .nf /* ADDRESS_VERIFICATION_README, address verification howto /* LICENSE /* .ad /* .fi /* The Secure Mailer license must be distributed with this software. /* HISTORY /* .ad /* .fi /* This service was introduced with Postfix version 2.1. /* AUTHOR(S) /* Wietse Venema /* IBM T.J. Watson Research /* P.O. Box 704 /* Yorktown Heights, NY 10598, USA /*--*/ /* System library. */ #include <sys_defs.h> #include <sys/stat.h> #include <time.h> #include <string.h> #include <stdlib.h> #include <unistd.h> /* Utility library. */ #include <msg.h> #include <mymalloc.h> #include <htable.h> #include <dict_ht.h> #include <dict.h> #include <split_at.h> /* Global library. */ #include <mail_conf.h> #include <mail_params.h> #include <mail_proto.h> #include <post_mail.h> #include <verify_clnt.h> /* Server skeleton. */ #include <mail_server.h> /* Application-specific. */ /* * Tunable parameters. */ char *var_verify_map; int var_verify_pos_exp; int var_verify_pos_try; int var_verify_neg_exp; int var_verify_neg_try; char *var_verify_sender; /* * State. */ static DICT *verify_map; /* * Silly little macros. */ #define STR(x) vstring_str(x) #define STREQ(x,y) (strcmp(x,y) == 0) /* * The address verification database consists of (address, data) tuples. The * format of the data field is "status:probed:updated:text". The meaning of * each field is: * * status: one of the four recipient status codes (OK, DEFER, BOUNCE or TODO). * In the case of TODO, we have no information about the address, and the * address is being probed. * * probed: if non-zero, the time of the last outstanding address probe. If * zero, there is no outstanding address probe. * * updated: if non-zero, the time of the last processed address probe. If zero, * we have no information about the address, and the address is being * probed. * * text: descriptive text from delivery agents etc. */ /* * Quick test to see status without parsing the whole entry. */ #define STATUS_FROM_RAW_ENTRY(e) atoi(e) /* verify_make_entry - construct table entry */ static void verify_make_entry(VSTRING *buf, int status, long probed, long updated, const char *text) { vstring_sprintf(buf, "%d:%ld:%ld:%s", status, probed, updated, text); } /* verify_parse_entry - parse table entry */ static int verify_parse_entry(char *buf, int *status, long *probed, long *updated, char **text) { char *probed_text; char *updated_text; if ((probed_text = split_at(buf, ':')) != 0 && (updated_text = split_at(probed_text, ':')) != 0 && (*text = split_at(updated_text, ':')) != 0) { *probed = atol(probed_text); *updated = atol(updated_text); *status = atoi(buf); if ((*status == DEL_RCPT_STAT_OK || *status == DEL_RCPT_STAT_DEFER || *status == DEL_RCPT_STAT_BOUNCE || *status == DEL_RCPT_STAT_TODO) && (probed || updated)) return (0); } msg_warn("bad address verify table entry: %.100s", buf); return (-1); } /* verify_stat2name - status to name */ static const char *verify_stat2name(int addr_status) { if (addr_status == DEL_RCPT_STAT_OK) return ("deliverable"); if (addr_status == DEL_RCPT_STAT_DEFER) return ("undeliverable"); if (addr_status == DEL_RCPT_STAT_BOUNCE) return ("undeliverable"); return (0); } /* verify_update_service - update address service */ static void verify_update_service(VSTREAM *client_stream) { VSTRING *buf = vstring_alloc(10); VSTRING *addr = vstring_alloc(10); int addr_status; VSTRING *text = vstring_alloc(10); const char *status_name; const char *raw_data; long probed; long updated; if (attr_scan(client_stream, ATTR_FLAG_STRICT, ATTR_TYPE_STR, MAIL_ATTR_ADDR, addr, ATTR_TYPE_NUM, MAIL_ATTR_ADDR_STATUS, &addr_status, ATTR_TYPE_STR, MAIL_ATTR_WHY, text, ATTR_TYPE_END) == 3) { if ((status_name = verify_stat2name(addr_status)) == 0) { msg_warn("bad recipient status %d for recipient %s", addr_status, STR(addr)); attr_print(client_stream, ATTR_FLAG_NONE, ATTR_TYPE_NUM, MAIL_ATTR_STATUS, VRFY_STAT_BAD, ATTR_TYPE_END); } else { /* * Robustness: don't allow a failed probe to clobber an OK * address before it expires. The failed probe is ignored so that * the address will be re-probed upon the next query. As long as * some probes succeed the address will remain cached as OK. */ if (addr_status == DEL_RCPT_STAT_OK || (raw_data = dict_get(verify_map, STR(addr))) == 0 || STATUS_FROM_RAW_ENTRY(raw_data) != DEL_RCPT_STAT_OK) { probed = 0; updated = (long) time((time_t *) 0); verify_make_entry(buf, addr_status, probed, updated, STR(text)); if (msg_verbose) msg_info("PUT %s status=%d probed=%ld updated=%ld text=%s", STR(addr), addr_status, probed, updated, STR(text)); dict_put(verify_map, STR(addr), STR(buf)); } attr_print(client_stream, ATTR_FLAG_NONE, ATTR_TYPE_NUM, MAIL_ATTR_STATUS, VRFY_STAT_OK, ATTR_TYPE_END); } } vstring_free(buf); vstring_free(addr); vstring_free(text); } /* verify_post_mail_action - callback */ static void verify_post_mail_action(VSTREAM *stream, void *unused_context) { /* * Probe messages need no body content, because they are never delivered, * deferred, or bounced. */ if (stream != 0) post_mail_fclose(stream); } /* verify_query_service - query address status */ static void verify_query_service(VSTREAM *client_stream) { VSTRING *addr = vstring_alloc(10); VSTRING *get_buf = 0; VSTRING *put_buf = 0; const char *raw_data; int addr_status; long probed; long updated; char *text; VSTREAM *post; if (attr_scan(client_stream, ATTR_FLAG_STRICT, ATTR_TYPE_STR, MAIL_ATTR_ADDR, addr, ATTR_TYPE_END) == 1) { long now = (long) time((time_t *) 0); /* * Produce a default record when no usable record exists. * * If negative caching is disabled, purge an expired record from the * database. * * XXX Assume that a probe is lost if no response is received in 1000 * seconds. If this number is too small the queue will slowly fill up * with delayed probes. * * XXX Maintain a moving average for the probe turnaround time, and * allow probe "retransmission" when a probe is outstanding for, say * some minimal amount of time (1000 sec) plus several times the * observed probe turnaround time. This causes probing to back off * when the mail system becomes congested. */ #define POSITIVE_ENTRY_EXPIRED(addr_status, updated) \ (addr_status == DEL_RCPT_STAT_OK && updated + var_verify_pos_exp < now) #define NEGATIVE_ENTRY_EXPIRED(addr_status, updated) \ (addr_status != DEL_RCPT_STAT_OK && updated + var_verify_neg_exp < now) #define PROBE_TTL 1000 if ((raw_data = dict_get(verify_map, STR(addr))) == 0 /* not found */ || ((get_buf = vstring_alloc(10)), vstring_strcpy(get_buf, raw_data), /* malformed */ verify_parse_entry(STR(get_buf), &addr_status, &probed, &updated, &text) < 0) || (now - probed > PROBE_TTL /* safe to probe */ && (POSITIVE_ENTRY_EXPIRED(addr_status, updated) || NEGATIVE_ENTRY_EXPIRED(addr_status, updated)))) { addr_status = DEL_RCPT_STAT_TODO; probed = 0; updated = 0; text = "Address verification in progress"; if (raw_data != 0 && var_verify_neg_cache == 0) dict_del(verify_map, STR(addr)); } if (msg_verbose) msg_info("GOT %s status=%d probed=%ld updated=%ld text=%s", STR(addr), addr_status, probed, updated, text); /* * Respond to the client. */ attr_print(client_stream, ATTR_FLAG_NONE, ATTR_TYPE_NUM, MAIL_ATTR_STATUS, VRFY_STAT_OK, ATTR_TYPE_NUM, MAIL_ATTR_ADDR_STATUS, addr_status, ATTR_TYPE_STR, MAIL_ATTR_WHY, text, ATTR_TYPE_END); /* * Send a new probe when the information needs to be refreshed. * * XXX For an initial proof of concept implementation, use synchronous * mail submission. This needs to be made async for high-volume * sites, which makes it even more interesting to eliminate duplicate * queries while a probe is being built. * * If negative caching is turned off, update the database only when * refreshing an existing entry. */ #define POSITIVE_REFRESH_NEEDED(addr_status, updated) \ (addr_status == DEL_RCPT_STAT_OK && updated + var_verify_pos_try < now) #define NEGATIVE_REFRESH_NEEDED(addr_status, updated) \ (addr_status != DEL_RCPT_STAT_OK && updated + var_verify_neg_try < now) if (now - probed > PROBE_TTL && (POSITIVE_REFRESH_NEEDED(addr_status, updated) || NEGATIVE_REFRESH_NEEDED(addr_status, updated))) { if (msg_verbose) msg_info("PROBE %s status=%d probed=%ld updated=%ld", STR(addr), addr_status, now, updated); post_mail_fopen_async(strcmp(var_verify_sender, "<>") == 0 ? "" : var_verify_sender, STR(addr), CLEANUP_FLAG_MASK_INTERNAL, DEL_REQ_FLAG_VERIFY, verify_post_mail_action, (void *) 0); if (updated != 0 || var_verify_neg_cache != 0) { put_buf = vstring_alloc(10); verify_make_entry(put_buf, addr_status, now, updated, text); if (msg_verbose) msg_info("PUT %s status=%d probed=%ld updated=%ld text=%s", STR(addr), addr_status, now, updated, text); dict_put(verify_map, STR(addr), STR(put_buf)); } } } vstring_free(addr); if (get_buf) vstring_free(get_buf); if (put_buf) vstring_free(put_buf); } /* verify_service - perform service for client */ static void verify_service(VSTREAM *client_stream, char *unused_service, char **argv) { VSTRING *request = vstring_alloc(10); /* * Sanity check. This service takes no command-line arguments. */ if (argv[0]) msg_fatal("unexpected command-line argument: %s", argv[0]); /* * This routine runs whenever a client connects to the socket dedicated * to the address verification service. All connection-management stuff * is handled by the common code in multi_server.c. */ if (attr_scan(client_stream, ATTR_FLAG_MORE | ATTR_FLAG_STRICT, ATTR_TYPE_STR, MAIL_ATTR_REQ, request, ATTR_TYPE_END) == 1) { if (STREQ(STR(request), VRFY_REQ_UPDATE)) { verify_update_service(client_stream); } else if (STREQ(STR(request), VRFY_REQ_QUERY)) { verify_query_service(client_stream); } else { msg_warn("unrecognized request: \"%s\", ignored", STR(request)); attr_print(client_stream, ATTR_FLAG_NONE, ATTR_TYPE_NUM, MAIL_ATTR_STATUS, VRFY_STAT_BAD, ATTR_TYPE_END); } } vstream_fflush(client_stream); vstring_free(request); } /* post_jail_init - post-jail initialization */ static void post_jail_init(char *unused_name, char **unused_argv) { /* * If the database is in volatile memory only, prevent automatic process * suicide after a limited number of client requests or after a limited * amount of idle time. */ if (*var_verify_map == 0) { var_use_limit = 0; var_idle_limit = 0; } } /* pre_jail_init - pre-jail initialization */ static void pre_jail_init(char *unused_name, char **unused_argv) { mode_t saved_mask; /* * Keep state in persistent (external) or volatile (internal) map. */ #define VERIFY_DICT_OPEN_FLAGS (DICT_FLAG_DUP_REPLACE | DICT_FLAG_SYNC_UPDATE) if (*var_verify_map) { saved_mask = umask(022); verify_map = dict_open(var_verify_map, O_CREAT | O_RDWR, VERIFY_DICT_OPEN_FLAGS); (void) umask(saved_mask); } else { verify_map = dict_ht_open("verify", htable_create(0), myfree); } /* * Never, ever, get killed by a master signal, as that would corrupt the * database when we're in the middle of an update. */ setsid(); } /* main - pass control to the multi-threaded skeleton */ int main(int argc, char **argv) { static CONFIG_STR_TABLE str_table[] = { VAR_VERIFY_MAP, DEF_VERIFY_MAP, &var_verify_map, 0, 0, VAR_VERIFY_SENDER, DEF_VERIFY_SENDER, &var_verify_sender, 0, 0, 0, }; static CONFIG_TIME_TABLE time_table[] = { VAR_VERIFY_POS_EXP, DEF_VERIFY_POS_EXP, &var_verify_pos_exp, 1, 0, VAR_VERIFY_POS_TRY, DEF_VERIFY_POS_TRY, &var_verify_pos_try, 1, 0, VAR_VERIFY_NEG_EXP, DEF_VERIFY_NEG_EXP, &var_verify_neg_exp, 1, 0, VAR_VERIFY_NEG_TRY, DEF_VERIFY_NEG_TRY, &var_verify_neg_try, 1, 0, 0, }; multi_server_main(argc, argv, verify_service, MAIL_SERVER_STR_TABLE, str_table, MAIL_SERVER_TIME_TABLE, time_table, MAIL_SERVER_PRE_INIT, pre_jail_init, MAIL_SERVER_POST_INIT, post_jail_init, MAIL_SERVER_SOLITARY, 0); }