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Diffstat (limited to 'src/dnsblog/dnsblog.c')
| -rw-r--r-- | src/dnsblog/dnsblog.c | 319 |
1 files changed, 319 insertions, 0 deletions
diff --git a/src/dnsblog/dnsblog.c b/src/dnsblog/dnsblog.c new file mode 100644 index 0000000..bc87c4b --- /dev/null +++ b/src/dnsblog/dnsblog.c @@ -0,0 +1,319 @@ +/*++ +/* NAME +/* dnsblog 8 +/* SUMMARY +/* Postfix DNS allow/denylist logger +/* SYNOPSIS +/* \fBdnsblog\fR [generic Postfix daemon options] +/* DESCRIPTION +/* The \fBdnsblog\fR(8) server implements an ad-hoc DNS +/* allow/denylist lookup service. This may eventually be +/* replaced by an UDP client that is built directly into the +/* \fBpostscreen\fR(8) server. +/* PROTOCOL +/* .ad +/* .fi +/* With each connection, the \fBdnsblog\fR(8) server receives +/* a DNS allow/denylist domain name, an IP address, and an ID. +/* If the IP address is listed under the DNS allow/denylist, the +/* \fBdnsblog\fR(8) server logs the match and replies with the +/* query arguments plus an address list with the resulting IP +/* addresses, separated by whitespace, and the reply TTL. +/* Otherwise it replies with the query arguments plus an empty +/* address list and the reply TTL; the reply TTL is -1 if there +/* is no reply, or a negative reply that contains no SOA record. +/* Finally, the \fBdnsblog\fR(8) server closes the connection. +/* DIAGNOSTICS +/* Problems and transactions are logged to \fBsyslogd\fR(8) +/* or \fBpostlogd\fR(8). +/* CONFIGURATION PARAMETERS +/* .ad +/* .fi +/* Changes to \fBmain.cf\fR are picked up automatically, as +/* \fBdnsblog\fR(8) processes run for only a limited amount +/* of time. Use the command "\fBpostfix reload\fR" to speed +/* up a change. +/* +/* The text below provides only a parameter summary. See +/* \fBpostconf\fR(5) for more details including examples. +/* .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 "\fBpostscreen_dnsbl_sites (empty)\fR" +/* Optional list of DNS allow/denylist domains, filters and weight +/* factors. +/* .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 (see 'postconf -d' output)\fR" +/* A prefix that is prepended to the process name in syslog +/* records, so that, for example, "smtpd" becomes "prefix/smtpd". +/* .PP +/* Available in Postfix 3.3 and later: +/* .IP "\fBservice_name (read-only)\fR" +/* The master.cf service name of a Postfix daemon process. +/* SEE ALSO +/* smtpd(8), Postfix SMTP server +/* postconf(5), configuration parameters +/* postlogd(8), Postfix logging +/* syslogd(8), system logging +/* LICENSE +/* .ad +/* .fi +/* The Secure Mailer license must be distributed with this software. +/* HISTORY +/* .ad +/* .fi +/* This service was introduced with Postfix version 2.8. +/* AUTHOR(S) +/* Wietse Venema +/* IBM T.J. Watson Research +/* P.O. Box 704 +/* Yorktown Heights, NY 10598, USA +/* +/* Wietse Venema +/* Google, Inc. +/* 111 8th Avenue +/* New York, NY 10011, USA +/*--*/ + +/* System library. */ + +#include <sys_defs.h> +#include <limits.h> + +/* Utility library. */ + +#include <msg.h> +#include <vstream.h> +#include <vstring.h> +#include <argv.h> +#include <myaddrinfo.h> +#include <valid_hostname.h> +#include <sock_addr.h> + +/* Global library. */ + +#include <mail_conf.h> +#include <mail_version.h> +#include <mail_proto.h> +#include <mail_params.h> + +/* DNS library. */ + +#include <dns.h> + +/* Server skeleton. */ + +#include <mail_server.h> + +/* Application-specific. */ + + /* + * Tunable parameters. + */ +int var_dnsblog_delay; + + /* + * Static so we don't allocate and free on every request. + */ +static VSTRING *rbl_domain; +static VSTRING *addr; +static VSTRING *query; +static VSTRING *why; +static VSTRING *result; + + /* + * Silly little macros. + */ +#define STR(x) vstring_str(x) +#define LEN(x) VSTRING_LEN(x) + +/* static void dnsblog_query - query DNSBL for client address */ + +static VSTRING *dnsblog_query(VSTRING *result, int *result_ttl, + const char *dnsbl_domain, + const char *addr) +{ + const char *myname = "dnsblog_query"; + ARGV *octets; + int i; + struct addrinfo *res; + unsigned char *ipv6_addr; + int dns_status; + DNS_RR *addr_list; + DNS_RR *rr; + MAI_HOSTADDR_STR hostaddr; + + if (msg_verbose) + msg_info("%s: addr %s dnsbl_domain %s", + myname, addr, dnsbl_domain); + + VSTRING_RESET(query); + + /* + * Reverse the client IPV6 address, represented as 32 hexadecimal + * nibbles. We use the binary address to avoid tricky code. Asking for an + * AAAA record makes no sense here. Just like with IPv4 we use the lookup + * result as a bit mask, not as an IP address. + */ +#ifdef HAS_IPV6 + if (valid_ipv6_hostaddr(addr, DONT_GRIPE)) { + if (hostaddr_to_sockaddr(addr, (char *) 0, 0, &res) != 0 + || res->ai_family != PF_INET6) + msg_fatal("%s: unable to convert address %s", myname, addr); + ipv6_addr = (unsigned char *) &SOCK_ADDR_IN6_ADDR(res->ai_addr); + for (i = sizeof(SOCK_ADDR_IN6_ADDR(res->ai_addr)) - 1; i >= 0; i--) + vstring_sprintf_append(query, "%x.%x.", + ipv6_addr[i] & 0xf, ipv6_addr[i] >> 4); + freeaddrinfo(res); + } else +#endif + + /* + * Reverse the client IPV4 address, represented as four decimal octet + * values. We use the textual address for convenience. + */ + { + octets = argv_split(addr, "."); + for (i = octets->argc - 1; i >= 0; i--) { + vstring_strcat(query, octets->argv[i]); + vstring_strcat(query, "."); + } + argv_free(octets); + } + + /* + * Tack on the RBL domain name and query the DNS for an A record. + */ + vstring_strcat(query, dnsbl_domain); + dns_status = dns_lookup_x(STR(query), T_A, 0, &addr_list, (VSTRING *) 0, + why, (int *) 0, DNS_REQ_FLAG_NCACHE_TTL); + + /* + * We return the lowest TTL in the response from the A record(s) if + * found, or from the SOA record(s) if available. If the reply specifies + * no TTL, or if the query fails, we return a TTL of -1. + */ + VSTRING_RESET(result); + *result_ttl = -1; + if (dns_status == DNS_OK) { + for (rr = addr_list; rr != 0; rr = rr->next) { + if (dns_rr_to_pa(rr, &hostaddr) == 0) { + msg_warn("%s: skipping reply record type %s for query %s: %m", + myname, dns_strtype(rr->type), STR(query)); + } else { + msg_info("addr %s listed by domain %s as %s", + addr, dnsbl_domain, hostaddr.buf); + if (LEN(result) > 0) + vstring_strcat(result, " "); + vstring_strcat(result, hostaddr.buf); + /* Grab the positive reply TTL. */ + if (*result_ttl < 0 || *result_ttl > rr->ttl) + *result_ttl = rr->ttl; + } + } + dns_rr_free(addr_list); + } else if (dns_status == DNS_NOTFOUND) { + if (msg_verbose) + msg_info("%s: addr %s not listed by domain %s", + myname, addr, dnsbl_domain); + /* Grab the negative reply TTL. */ + for (rr = addr_list; rr != 0; rr = rr->next) { + if (rr->type == T_SOA && (*result_ttl < 0 || *result_ttl > rr->ttl)) + *result_ttl = rr->ttl; + } + dns_rr_free(addr_list); + } else { + msg_warn("%s: lookup error for DNS query %s: %s", + myname, STR(query), STR(why)); + } + VSTRING_TERMINATE(result); + return (result); +} + +/* dnsblog_service - perform service for client */ + +static void dnsblog_service(VSTREAM *client_stream, char *unused_service, + char **argv) +{ + int request_id; + int result_ttl; + + /* + * 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 dnsblog service. All connection-management stuff is handled by + * the common code in single_server.c. + */ + if (attr_scan(client_stream, + ATTR_FLAG_MORE | ATTR_FLAG_STRICT, + RECV_ATTR_STR(MAIL_ATTR_RBL_DOMAIN, rbl_domain), + RECV_ATTR_STR(MAIL_ATTR_ACT_CLIENT_ADDR, addr), + RECV_ATTR_INT(MAIL_ATTR_LABEL, &request_id), + ATTR_TYPE_END) == 3) { + (void) dnsblog_query(result, &result_ttl, STR(rbl_domain), STR(addr)); + if (var_dnsblog_delay > 0) + sleep(var_dnsblog_delay); + attr_print(client_stream, ATTR_FLAG_NONE, + SEND_ATTR_STR(MAIL_ATTR_RBL_DOMAIN, STR(rbl_domain)), + SEND_ATTR_STR(MAIL_ATTR_ACT_CLIENT_ADDR, STR(addr)), + SEND_ATTR_INT(MAIL_ATTR_LABEL, request_id), + SEND_ATTR_STR(MAIL_ATTR_RBL_ADDR, STR(result)), + SEND_ATTR_INT(MAIL_ATTR_TTL, result_ttl), + ATTR_TYPE_END); + vstream_fflush(client_stream); + } +} + +/* post_jail_init - post-jail initialization */ + +static void post_jail_init(char *unused_name, char **unused_argv) +{ + rbl_domain = vstring_alloc(100); + addr = vstring_alloc(100); + query = vstring_alloc(100); + why = vstring_alloc(100); + result = vstring_alloc(100); + var_use_limit = 0; +} + +MAIL_VERSION_STAMP_DECLARE; + +/* main - pass control to the multi-threaded skeleton */ + +int main(int argc, char **argv) +{ + static const CONFIG_TIME_TABLE time_table[] = { + VAR_DNSBLOG_DELAY, DEF_DNSBLOG_DELAY, &var_dnsblog_delay, 0, 0, + 0, + }; + + /* + * Fingerprint executables and core dumps. + */ + MAIL_VERSION_STAMP_ALLOCATE; + + single_server_main(argc, argv, dnsblog_service, + CA_MAIL_SERVER_TIME_TABLE(time_table), + CA_MAIL_SERVER_POST_INIT(post_jail_init), + CA_MAIL_SERVER_UNLIMITED, + CA_MAIL_SERVER_RETIRE_ME, + 0); +} |