Mercurial > dnsbl
diff src/new.cpp @ 71:dd21c8e13074
start coding on new config syntax
author | carl |
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date | Sat, 09 Jul 2005 19:24:41 -0700 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/new.cpp Sat Jul 09 19:24:41 2005 -0700 @@ -0,0 +1,1389 @@ +/* + +Copyright (c) 2004, 2005 Carl Byington - 510 Software Group, released +under the GPL version 2 or any later version at your choice available at +http://www.fsf.org/licenses/gpl.txt + +Based on a sample milter Copyright (c) 2000-2003 Sendmail, Inc. and its +suppliers. Inspired by the DCC by Rhyolite Software + +-r port The port used to talk to our internal dns resolver processes +-p port The port through which the MTA will connect to this milter. +-t sec The timeout value. +-c Check the config, and print a copy to stdout. Don't start the + milter or do anything with the socket. +-d Add debug syslog entries + + +TODO: +1) Add config for max_recipients for each mail domain. Recipients in +excess of that limit will be rejected, and the entire data will be +rejected if it is sent. + +2) Add config for poison addresses. If any recipient is poison, all +recipients are rejected even if they would be whitelisted, and the +data is rejected if sent. + +3) Add option to only allow one recipient if the return path is empty. + +4) Check if the envelope from domain name primary MX points 127.0.0.0/8 + +5) Add option for using smtp connections to verify addresses from backup +mx machines. This allows the backup mx to learn the valid addresses +on the primary machine. + +*/ + + +// from sendmail sample +#include <sys/types.h> +#include <sys/stat.h> +#include <errno.h> +#include <sysexits.h> +#include <unistd.h> + +// needed for socket io +#include <sys/ioctl.h> +#include <net/if.h> +#include <arpa/inet.h> +#include <netinet/in.h> +#include <netinet/tcp.h> +#include <netdb.h> +#include <sys/socket.h> +#include <sys/un.h> + +// needed for thread +#include <pthread.h> + +// needed for std c++ collections +#include <set> +#include <map> +#include <list> + +// for the dns resolver +#include <netinet/in.h> +#include <arpa/nameser.h> +#include <resolv.h> + +// misc stuff needed here +#include <ctype.h> +#include <syslog.h> +#include <pwd.h> +#include <sys/wait.h> /* header for waitpid() and various macros */ +#include <signal.h> /* header for signal functions */ + +#include "context.h" + +static char* dnsbl_version="$Id:"; + +extern "C" { + #include "libmilter/mfapi.h" + sfsistat mlfi_connect(SMFICTX *ctx, char *hostname, _SOCK_ADDR *hostaddr); + sfsistat mlfi_envfrom(SMFICTX *ctx, char **argv); + sfsistat mlfi_envrcpt(SMFICTX *ctx, char **argv); + sfsistat mlfi_body(SMFICTX *ctx, u_char *data, size_t len); + sfsistat mlfi_eom(SMFICTX *ctx); + sfsistat mlfi_abort(SMFICTX *ctx); + sfsistat mlfi_close(SMFICTX *ctx); + void sig_chld(int signo); +} + +struct ns_map { + // all the strings are owned by the keys/values in the ns_host string map + string_map ns_host; // nameserver name -> host name that uses this name server + ns_mapper ns_ip; // nameserver name -> ip address of the name server +}; + +static bool debug_syslog = false; +static bool loader_run = true; // used to stop the config loader thread +static CONFIG * config = NULL; // protected by the config_mutex +static int generation = 0; // protected by the config_mutex + +static pthread_mutex_t config_mutex; +static pthread_mutex_t syslog_mutex; +static pthread_mutex_t resolve_mutex; +static pthread_mutex_t fd_pool_mutex; + +static std::set<int> fd_pool; +static int NULL_SOCKET = -1; +static char *resolver_port = NULL; // unix domain socket to talk to the dns resolver process +static int resolver_socket = NULL_SOCKET; // socket used to listen for resolver requests +static time_t ERROR_SOCKET_TIME = 60; // number of seconds between attempts to open the spam filter socket +static time_t last_error_time; +static int resolver_sock_count = 0; // protected with fd_pool_mutex +static int resolver_pool_size = 0; // protected with fd_pool_mutex + + +// packed structure to allow a single socket write to dump the +// length and the following answer. The packing attribute is gcc specific. +struct glommer { + int length; + #ifdef NS_PACKETSZ + u_char answer[NS_PACKETSZ]; // with a resolver, we return resolver answers + #else + int answer; // without a resolver, we return a single ip4 address, 0 == no answer + #endif +} __attribute__ ((packed)); + +struct mlfiPriv; + + +//////////////////////////////////////////////// +// helper to discard the strings and objects held by an ns_map +// +static void discard(ns_map &s); +static void discard(ns_map &s) { + for (string_map::iterator i=s.ns_host.begin(); i!=s.ns_host.end(); i++) { + char *x = (*i).first; + char *y = (*i).second; + free(x); + free(y); + } + s.ns_ip.clear(); + s.ns_host.clear(); +} + +//////////////////////////////////////////////// +// helper to register a string in an ns_map +// +static void register_string(ns_map &s, char *name, char *refer); +static void register_string(ns_map &s, char *name, char *refer) { + string_map::iterator i = s.ns_host.find(name); + if (i != s.ns_host.end()) return; + char *x = strdup(name); + char *y = strdup(refer); + s.ns_ip[x] = 0; + s.ns_host[x] = y; + +} + +//////////////////////////////////////////////// +// syslog a message +// +static void my_syslog(mlfiPriv *priv, char *text); + + +// include the content scanner +#include "scanner.cpp" + + +//////////////////////////////////////////////// +// disconnect the fd from the dns resolver process +// +void my_disconnect(int sock, bool decrement = true); +void my_disconnect(int sock, bool decrement) +{ + if (sock != NULL_SOCKET) { + if (decrement) { + pthread_mutex_lock(&fd_pool_mutex); + resolver_sock_count--; + pthread_mutex_unlock(&fd_pool_mutex); + } + shutdown(sock, SHUT_RDWR); + close(sock); + } +} + + +//////////////////////////////////////////////// +// return fd connected to the dns resolver process +// +int my_connect(); +int my_connect() +{ + // if we have had recent errors, don't even try to open the socket + time_t now = time(NULL); + if ((now - last_error_time) < ERROR_SOCKET_TIME) return NULL_SOCKET; + + // nothing recent, maybe this time it will work + int sock = NULL_SOCKET; + sockaddr_un server; + memset(&server, '\0', sizeof(server)); + server.sun_family = AF_UNIX; + strncpy(server.sun_path, resolver_port, sizeof(server.sun_path)-1); + sock = socket(AF_UNIX, SOCK_STREAM, 0); + if (sock != NULL_SOCKET) { + bool rc = (connect(sock, (sockaddr *)&server, sizeof(server)) == 0); + if (!rc) { + my_disconnect(sock, false); + sock = NULL_SOCKET; + last_error_time = now; + } + } + else last_error_time = now; + if (sock != NULL_SOCKET) { + pthread_mutex_lock(&fd_pool_mutex); + resolver_sock_count++; + pthread_mutex_unlock(&fd_pool_mutex); + } + return sock; +} + + +//////////////////////////////////////////////// +// mail filter private data, held for us by sendmail +// +struct mlfiPriv +{ + // connection specific data + CONFIG *pc; // global context with our maps + int fd; // to talk to dns resolvers process + bool err; // did we get any errors on the resolver socket? + int ip; // ip4 address of the smtp client + map<DNSBLP, status> checked; // status from those lists + // message specific data + char *mailaddr; // envelope from value + char *queueid; // sendmail queue id + bool authenticated; // client authenticated? if so, suppress all dnsbl checks + bool have_whites; // have at least one whitelisted recipient? need to accept content and remove all non-whitelisted recipients if it fails + bool only_whites; // every recipient is whitelisted? + string_set non_whites; // remember the non-whitelisted recipients so we can remove them if need be + recorder *memory; // memory for the content scanner + url_scanner *scanner; // object to handle body scanning + mlfiPriv(); + ~mlfiPriv(); + void reset(bool final = false); // for a new message + void get_fd(); + void return_fd(); + int my_read(char *buf, int len); + int my_write(char *buf, int len); +}; + +mlfiPriv::mlfiPriv() { + pthread_mutex_lock(&config_mutex); + pc = config; + pc->reference_count++; + pthread_mutex_unlock(&config_mutex); + get_fd(); + ip = 0; + mailaddr = NULL; + queueid = NULL; + authenticated = false; + have_whites = false; + only_whites = true; + memory = new recorder(this, &pc->html_tags, &pc->tlds); + scanner = new url_scanner(memory); +} + +mlfiPriv::~mlfiPriv() { + return_fd(); + pthread_mutex_lock(&config_mutex); + pc->reference_count--; + pthread_mutex_unlock(&config_mutex); + reset(true); +} + +void mlfiPriv::reset(bool final) { + if (mailaddr) free(mailaddr); + if (queueid) free(queueid); + discard(non_whites); + delete memory; + delete scanner; + if (!final) { + mailaddr = NULL; + queueid = NULL; + authenticated = false; + have_whites = false; + only_whites = true; + memory = new recorder(this, &pc->html_tags, &pc->tlds); + scanner = new url_scanner(memory); + } +} + +void mlfiPriv::get_fd() +{ + err = true; + fd = NULL_SOCKET; + int result = pthread_mutex_lock(&fd_pool_mutex); + if (!result) { + std::set<int>::iterator i; + i = fd_pool.begin(); + if (i != fd_pool.end()) { + // have at least one fd in the pool + err = false; + fd = *i; + fd_pool.erase(fd); + resolver_pool_size--; + pthread_mutex_unlock(&fd_pool_mutex); + } + else { + // pool is empty, get a new fd + pthread_mutex_unlock(&fd_pool_mutex); + fd = my_connect(); + err = (fd == NULL_SOCKET); + } + } + else { + // cannot lock the pool, just get a new fd + fd = my_connect(); + err = (fd == NULL_SOCKET); + } +} + +void mlfiPriv::return_fd() +{ + if (err) { + // this fd got a socket error, so close it, rather than returning it to the pool + my_disconnect(fd); + } + else { + int result = pthread_mutex_lock(&fd_pool_mutex); + if (!result) { + if ((resolver_sock_count > resolver_pool_size*5) || (resolver_pool_size < 5)) { + // return the fd to the pool + fd_pool.insert(fd); + resolver_pool_size++; + pthread_mutex_unlock(&fd_pool_mutex); + } + else { + // more than 20% of the open resolver sockets are in the pool, and the + // pool as at least 5 sockets. that is enough, so just close this one. + pthread_mutex_unlock(&fd_pool_mutex); + my_disconnect(fd); + } + } + else { + // could not lock the pool, so just close the fd + my_disconnect(fd); + } + } +} + +int mlfiPriv::my_write(char *buf, int len) +{ + if (err) return 0; + int rs = 0; + while (len) { + int ws = write(fd, buf, len); + if (ws > 0) { + rs += ws; + len -= ws; + buf += ws; + } + else { + // peer closed the socket! + rs = 0; + err = true; + break; + } + } + return rs; +} + +int mlfiPriv::my_read(char *buf, int len) +{ + if (err) return 0; + int rs = 0; + while (len > 1) { + int ws = read(fd, buf, len); + if (ws > 0) { + rs += ws; + len -= ws; + buf += ws; + } + else { + // peer closed the socket! + rs = 0; + err = true; + break; + } + } + return rs; +} + +#define MLFIPRIV ((struct mlfiPriv *) smfi_getpriv(ctx)) + + +//////////////////////////////////////////////// +// syslog a message +// +static void my_syslog(mlfiPriv *priv, char *text) { + char buf[1000]; + if (priv) { + snprintf(buf, sizeof(buf), "%s: %s", priv->queueid, text); + text = buf; + } + pthread_mutex_lock(&syslog_mutex); + openlog("dnsbl", LOG_PID, LOG_MAIL); + syslog(LOG_NOTICE, "%s", text); + closelog(); + pthread_mutex_unlock(&syslog_mutex); +} + +static void my_syslog(char *text); +static void my_syslog(char *text) { + my_syslog(NULL, text); +} + +//////////////////////////////////////////////// +// register a global string +// +static char* register_string(char *name); +static char* register_string(char *name) { + return register_string(all_strings, name); +} + + +static char* next_token(char *delim); +static char* next_token(char *delim) { + char *name = strtok(NULL, delim); + if (!name) return name; + return register_string(name); +} + + +//////////////////////////////////////////////// +// lookup an email address in the env_from or env_to maps +// +static char* lookup1(char *email, string_map map); +static char* lookup1(char *email, string_map map) { + string_map::iterator i = map.find(email); + if (i != map.end()) return (*i).second; + char *x = strchr(email, '@'); + if (!x) return DEFAULT; + x++; + i = map.find(x); + if (i != map.end()) return (*i).second; + return DEFAULT; +} + + +//////////////////////////////////////////////// +// lookup an email address in the env_from or env_to maps +// this email address is passed in from sendmail, and will +// always be enclosed in <>. It may have mixed case, just +// as the mail client sent it. +// +static char* lookup(char* email, string_map map); +static char* lookup(char* email, string_map map) { + int n = strlen(email)-2; + if (n < 1) return DEFAULT; // malformed + char *key = strdup(email+1); + key[n] = '\0'; + for (int i=0; i<n; i++) key[i] = tolower(key[i]); + char *rc = lookup1(key, map); + free(key); + return rc; +} + + +//////////////////////////////////////////////// +// find the dnsbl with a specific name +// +static DNSBLP find_dnsbl(CONFIG &dc, char *name); +static DNSBLP find_dnsbl(CONFIG &dc, char *name) { + dnsblp_map::iterator i = dc.dnsbls.find(name); + if (i == dc.dnsbls.end()) return NULL; + return (*i).second; +} + + +//////////////////////////////////////////////// +// find the dnsbll with a specific name +// +static DNSBLLP find_dnsbll(CONFIG &dc, char *name); +static DNSBLLP find_dnsbll(CONFIG &dc, char *name) { + dnsbllp_map::iterator i = dc.dnsblls.find(name); + if (i == dc.dnsblls.end()) return NULL; + return (*i).second; +} + + +//////////////////////////////////////////////// +// find the envfrom map with a specific name +// +static string_map* find_from_map(CONFIG &dc, char *name); +static string_map* find_from_map(CONFIG &dc, char *name) { + from_map::iterator i = dc.env_from.find(name); + if (i == dc.env_from.end()) return NULL; + return (*i).second; +} + + +static string_map& really_find_from_map(CONFIG &dc, char *name); +static string_map& really_find_from_map(CONFIG &dc, char *name) { + string_map *sm = find_from_map(dc, name); + if (!sm) { + sm = new string_map; + dc.env_from[name] = sm; + } + return *sm; +} + + + +//////////////////////////////////////////////// +// read a resolver request from the socket, process it, and +// write the result back to the socket. + +static void process_resolver_requests(int socket); +static void process_resolver_requests(int socket) { +#ifdef NS_MAXDNAME + char question[NS_MAXDNAME]; +#else + char question[1000]; +#endif + glommer glom; + + int maxq = sizeof(question); + while (true) { + // read a question + int rs = 0; + while (true) { + int ns = read(socket, question+rs, maxq-rs); + if (ns > 0) { + rs += ns; + if (question[rs-1] == '\0') { + // last byte read was the null terminator, we are done + break; + } + } + else { + // peer closed the socket + //my_syslog("!!child worker process, peer closed socket while reading question"); + shutdown(socket, SHUT_RDWR); + close(socket); + return; + } + } + + // find the answer +#ifdef NS_PACKETSZ + //char text[1000]; + //snprintf(text, sizeof(text), "!!child worker process has a question %s", question); + //my_syslog(text); + glom.length = res_search(question, ns_c_in, ns_t_a, glom.answer, sizeof(glom.answer)); + if (glom.length < 0) glom.length = 0; // represent all errors as zero length answers +#else + glom.length = sizeof(glom.answer); + glom.answer = 0; + struct hostent *host = gethostbyname(question); + if (host && (host->h_addrtype == AF_INET)) { + memcpy(&glom.answer, host->h_addr, sizeof(glom.answer)); + } +#endif + + // write the answer + char *buf = (char *)&glom; + int len = glom.length + sizeof(glom.length); + //snprintf(text, sizeof(text), "!!child worker process writing answer length %d for total %d", glom.length, len); + //my_syslog(text); + int ws = 0; + while (len > ws) { + int ns = write(socket, buf+ws, len-ws); + if (ns > 0) { + ws += ns; + } + else { + // peer closed the socket! + //my_syslog("!!child worker process, peer closed socket while writing answer"); + shutdown(socket, SHUT_RDWR); + close(socket); + return; + } + } + } +} + + +//////////////////////////////////////////////// +// ask a dns question and get an A record answer - we don't try +// very hard, just using the default resolver retry settings. +// If we cannot get an answer, we just accept the mail. +// +// +static int dns_interface(mlfiPriv &priv, char *question, bool maybe_ip, ns_map *nameservers); +static int dns_interface(mlfiPriv &priv, char *question, bool maybe_ip, ns_map *nameservers) { + // this part can be done without locking the resolver mutex. Each + // milter thread is talking over its own socket to a separate resolver + // process, which does the actual dns resolution. + if (priv.err) return 0; // cannot ask more questions on this socket. + priv.my_write(question, strlen(question)+1); // write the question including the null terminator + glommer glom; + char *buf = (char *)&glom; + priv.my_read(buf, sizeof(glom.length)); + buf += sizeof(glom.length); + ///char text[1000]; + ///snprintf(text, sizeof(text), "!!milter thread wrote question %s and has answer length %d", question, glom.length); + ///my_syslog(text); + if ((glom.length < 0) || (glom.length > sizeof(glom.answer))) { + priv.err = true; + return 0; // cannot process overlarge answers + } + priv.my_read(buf, glom.length); + +#ifdef NS_PACKETSZ + // now we need to lock the resolver mutex to keep the milter threads from + // stepping on each other while parsing the dns answer. + int ret_address = 0; + pthread_mutex_lock(&resolve_mutex); + if (glom.length > 0) { + // parse the answer + ns_msg handle; + ns_rr rr; + if (ns_initparse(glom.answer, glom.length, &handle) == 0) { + // look for ns names + if (nameservers) { + ns_map &ns = *nameservers; + int rrnum = 0; + while (ns_parserr(&handle, ns_s_ns, rrnum++, &rr) == 0) { + if (ns_rr_type(rr) == ns_t_ns) { + char nam[NS_MAXDNAME+1]; + char *n = nam; + const u_char *p = ns_rr_rdata(rr); + while (((n-nam) < NS_MAXDNAME) && ((p-glom.answer) < glom.length) && *p) { + size_t s = *(p++); + if (s > 191) { + // compression pointer + s = (s-192)*256 + *(p++); + if (s >= glom.length) break; // pointer outside bounds of answer + p = glom.answer + s; + s = *(p++); + } + if (s > 0) { + if ((n-nam) >= (NS_MAXDNAME-s)) break; // destination would overflow name buffer + if ((p-glom.answer) >= (glom.length-s)) break; // source outside bounds of answer + memcpy(n, p, s); + n += s; + p += s; + *(n++) = '.'; + } + } + if (n-nam) n--; // remove trailing . + *n = '\0'; // null terminate it + register_string(ns, nam, question); // ns host to lookup later + } + } + rrnum = 0; + while (ns_parserr(&handle, ns_s_ar, rrnum++, &rr) == 0) { + if (ns_rr_type(rr) == ns_t_a) { + char* nam = (char*)ns_rr_name(rr); + ns_mapper::iterator i = ns.ns_ip.find(nam); + if (i != ns.ns_ip.end()) { + // we want this ip address + int address; + memcpy(&address, ns_rr_rdata(rr), sizeof(address)); + ns.ns_ip[nam] = address; + } + } + } + } + int rrnum = 0; + while (ns_parserr(&handle, ns_s_an, rrnum++, &rr) == 0) { + if (ns_rr_type(rr) == ns_t_a) { + int address; + memcpy(&address, ns_rr_rdata(rr), sizeof(address)); + ret_address = address; + } + } + } + } + if (maybe_ip && !ret_address) { + // might be a bare ip address + in_addr ip; + if (inet_aton(question, &ip)) { + ret_address = ip.s_addr; + } + } + pthread_mutex_unlock(&resolve_mutex); + return ret_address; +#else + return glom.answer; +#endif +} + + +//////////////////////////////////////////////// +// check a single dnsbl +// +static status check_single(mlfiPriv &priv, int ip, char *suffix); +static status check_single(mlfiPriv &priv, int ip, char *suffix) { + // make a dns question + const u_char *src = (const u_char *)&ip; + if (src[0] == 127) return oksofar; // don't do dns lookups on localhost +#ifdef NS_MAXDNAME + char question[NS_MAXDNAME]; +#else + char question[1000]; +#endif + snprintf(question, sizeof(question), "%u.%u.%u.%u.%s.", src[3], src[2], src[1], src[0], suffix); + // ask the question, if we get an A record it implies a blacklisted ip address + return (dns_interface(priv, question, false, NULL)) ? reject : oksofar; +} + + +//////////////////////////////////////////////// +// check a single dnsbl +// +static status check_single(mlfiPriv &priv, int ip, DNSBL &bl); +static status check_single(mlfiPriv &priv, int ip, DNSBL &bl) { + return check_single(priv, ip, bl.suffix); +} + + +//////////////////////////////////////////////// +// check the dnsbls specified for this recipient +// +static status check_dnsbl(mlfiPriv &priv, DNSBLLP dnsbllp, DNSBLP &rejectlist); +static status check_dnsbl(mlfiPriv &priv, DNSBLLP dnsbllp, DNSBLP &rejectlist) { + if (priv.authenticated) return oksofar; + if (!dnsbllp) return oksofar; + DNSBLL &dnsbll = *dnsbllp; + for (DNSBLL::iterator i=dnsbll.begin(); i!=dnsbll.end(); i++) { + DNSBLP dp = *i; // non null by construction + status st; + map<DNSBLP, status>::iterator f = priv.checked.find(dp); + if (f == priv.checked.end()) { + // have not checked this list yet + st = check_single(priv, priv.ip, *dp); + rejectlist = dp; + priv.checked[dp] = st; + } + else { + st = (*f).second; + rejectlist = (*f).first; + } + if (st == reject) return st; + } + return oksofar; +} + + +//////////////////////////////////////////////// +// check the hosts from the body against the content dnsbl +// +static status check_hosts(mlfiPriv &priv, char *&host, int &ip); +static status check_hosts(mlfiPriv &priv, char *&host, int &ip) { + CONFIG &dc = *priv.pc; + int count = 0; + ns_map nameservers; + bool ran = priv.pc->host_random; + int lim = priv.pc->host_limit; // we should not look at more than this many hosts + int cnt = priv.memory->hosts.size(); // number of hosts we could look at + int_set ips; // remove duplicate ip addresses + for (string_set::iterator i=priv.memory->hosts.begin(); i!=priv.memory->hosts.end(); i++) { + host = *i; // a reference into priv.memory->hosts, which will live until this smtp transaction is closed + + // don't bother looking up hosts on the ignore list + string_set::iterator j = priv.pc->content_host_ignore.find(host); + if (j != priv.pc->content_host_ignore.end()) continue; + + // try to only look at lim/cnt fraction of the available cnt host names in random mode + if ((cnt > lim) && (lim > 0) && ran) { + int r = rand() % cnt; + if (r >= lim) { + char buf[1000]; + snprintf(buf, sizeof(buf), "host %s skipped", host); + my_syslog(&priv, buf); + continue; + } + } + count++; + if ((count > lim) && (lim > 0) && (!ran)) { + discard(nameservers); + return reject_host; + } + ip = dns_interface(priv, host, true, &nameservers); + if (debug_syslog) { + char buf[1000]; + if (ip) { + char adr[sizeof "255.255.255.255"]; + adr[0] = '\0'; + inet_ntop(AF_INET, (const u_char *)&ip, adr, sizeof(adr)); + snprintf(buf, sizeof(buf), "host %s found at %s", host, adr); + } + else { + snprintf(buf, sizeof(buf), "host %s not found", host); + } + my_syslog(&priv, buf); + } + if (ip) { + int_set::iterator i = ips.find(ip); + if (i == ips.end()) { + ips.insert(ip); + status st = check_single(priv, ip, dc.content_suffix); + if (st == reject) { + discard(nameservers); + return st; + } + } + } + } + lim *= 4; // allow average of 3 ns per host name + for (ns_mapper::iterator i=nameservers.ns_ip.begin(); i!=nameservers.ns_ip.end(); i++) { + count++; + if ((count > lim) && (lim > 0)) { + if (ran) continue; // don't complain + discard(nameservers); + return reject_host; + } + host = (*i).first; // a transient reference that needs to be replaced before we return it + ip = (*i).second; + if (!ip) ip = dns_interface(priv, host, false, NULL); + if (debug_syslog) { + char buf[200]; + if (ip) { + char adr[sizeof "255.255.255.255"]; + adr[0] = '\0'; + inet_ntop(AF_INET, (const u_char *)&ip, adr, sizeof(adr)); + snprintf(buf, sizeof(buf), "ns %s found at %s", host, adr); + } + else { + snprintf(buf, sizeof(buf), "ns %s not found", host); + } + my_syslog(&priv, buf); + } + if (ip) { + int_set::iterator i = ips.find(ip); + if (i == ips.end()) { + ips.insert(ip); + status st = check_single(priv, ip, dc.content_suffix); + if (st == reject) { + string_map::iterator j = nameservers.ns_host.find(host); + if (j != nameservers.ns_host.end()) { + char *refer = (*j).second; + char buf[1000]; + snprintf(buf, sizeof(buf), "%s with nameserver %s", refer, host); + host = register_string(priv.memory->hosts, buf); // put a copy into priv.memory->hosts, and return that reference + } + else { + host = register_string(priv.memory->hosts, host); // put a copy into priv.memory->hosts, and return that reference + } + discard(nameservers); + return st; + } + } + } + } + discard(nameservers); + host = NULL; + int bin = priv.memory->binary_tags; + int bad = priv.memory->bad_html_tags; + lim = priv.pc->tag_limit; + if (3*bin > bad) return oksofar; // probably .zip or .tar.gz with random content + if ((bad > lim) && (lim > 0)) return reject_tag; + return oksofar; +} + + +//////////////////////////////////////////////// +// start of sendmail milter interfaces +// +sfsistat mlfi_connect(SMFICTX *ctx, char *hostname, _SOCK_ADDR *hostaddr) +{ + // allocate some private memory + mlfiPriv *priv = new mlfiPriv; + if (hostaddr->sa_family == AF_INET) { + priv->ip = ((struct sockaddr_in *)hostaddr)->sin_addr.s_addr; + } + + // save the private data + smfi_setpriv(ctx, (void*)priv); + + // continue processing + return SMFIS_CONTINUE; +} + +sfsistat mlfi_envfrom(SMFICTX *ctx, char **from) +{ + mlfiPriv &priv = *MLFIPRIV; + priv.mailaddr = strdup(from[0]); + priv.authenticated = (smfi_getsymval(ctx, "{auth_authen}") != NULL); + return SMFIS_CONTINUE; +} + +sfsistat mlfi_envrcpt(SMFICTX *ctx, char **rcpt) +{ + DNSBLP rejectlist = NULL; // list that caused the reject + status st = oksofar; + mlfiPriv &priv = *MLFIPRIV; + CONFIG &dc = *priv.pc; + if (!priv.queueid) priv.queueid = strdup(smfi_getsymval(ctx, "i")); + char *rcptaddr = rcpt[0]; + char *dnsname = lookup(rcptaddr, dc.env_to_dnsbll); + char *fromname = lookup(rcptaddr, dc.env_to_chkfrom); + if ((strcmp(dnsname, BLACK) == 0) || + (strcmp(fromname, BLACK) == 0)) { + st = black; // two options to blacklist this recipient + } + else if (strcmp(fromname, WHITE) == 0) { + st = white; + } + else { + // check an env_from map + string_map *sm = find_from_map(dc, fromname); + if (sm != NULL) { + fromname = lookup(priv.mailaddr, *sm); // returns default if name not in map + if (strcmp(fromname, BLACK) == 0) { + st = black; // blacklist this envelope from value + } + if (strcmp(fromname, WHITE) == 0) { + st = white; // blacklist this envelope from value + } + } + } + if ((st == oksofar) && (strcmp(dnsname, WHITE) != 0)) { + // check dns lists + st = check_dnsbl(priv, find_dnsbll(dc, dnsname), rejectlist); + } + + if (st == reject) { + // reject the recipient based on some dnsbl + char adr[sizeof "255.255.255.255"]; + adr[0] = '\0'; + inet_ntop(AF_INET, (const u_char *)&priv.ip, adr, sizeof(adr)); + char buf[2000]; + snprintf(buf, sizeof(buf), rejectlist->message, adr, adr); + smfi_setreply(ctx, "550", "5.7.1", buf); + return SMFIS_REJECT; + } + else if (st == black) { + // reject the recipient based on blacklisting either from or to + smfi_setreply(ctx, "550", "5.7.1", "no such user"); + return SMFIS_REJECT; + } + else { + // accept the recipient + if (st == oksofar) { + // but remember the non-whites + register_string(priv.non_whites, rcptaddr); + priv.only_whites = false; + } + if (st == white) { + priv.have_whites = true; + } + return SMFIS_CONTINUE; + } +} + +sfsistat mlfi_body(SMFICTX *ctx, u_char *data, size_t len) +{ + mlfiPriv &priv = *MLFIPRIV; + if (priv.authenticated) return SMFIS_CONTINUE; + if (priv.only_whites) return SMFIS_CONTINUE; + if (!priv.pc->content_suffix) return SMFIS_CONTINUE; + priv.scanner->scan(data, len); + return SMFIS_CONTINUE; +} + +sfsistat mlfi_eom(SMFICTX *ctx) +{ + sfsistat rc; + mlfiPriv &priv = *MLFIPRIV; + char *host = NULL; + int ip; + status st; + // process end of message + if (priv.authenticated || + priv.only_whites || + (!priv.pc->content_suffix) || + ((st=check_hosts(priv, host, ip)) == oksofar)) rc = SMFIS_CONTINUE; + else { + if (!priv.have_whites) { + // can reject the entire message + char buf[2000]; + if (st == reject_tag) { + // rejected due to excessive bad html tags + snprintf(buf, sizeof(buf), priv.pc->tag_limit_message); + } + else if (st == reject_host) { + // rejected due to excessive unique host/urls + snprintf(buf, sizeof(buf), priv.pc->host_limit_message); + } + else { + char adr[sizeof "255.255.255.255"]; + adr[0] = '\0'; + inet_ntop(AF_INET, (const u_char *)&ip, adr, sizeof(adr)); + snprintf(buf, sizeof(buf), priv.pc->content_message, host, adr); + } + smfi_setreply(ctx, "550", "5.7.1", buf); + rc = SMFIS_REJECT; + } + else { + // need to accept it but remove the recipients that don't want it + for (string_set::iterator i=priv.non_whites.begin(); i!=priv.non_whites.end(); i++) { + char *rcpt = *i; + smfi_delrcpt(ctx, rcpt); + } + rc = SMFIS_CONTINUE; + } + } + // reset for a new message on the same connection + mlfi_abort(ctx); + return rc; +} + +sfsistat mlfi_abort(SMFICTX *ctx) +{ + mlfiPriv &priv = *MLFIPRIV; + priv.reset(); + return SMFIS_CONTINUE; +} + +sfsistat mlfi_close(SMFICTX *ctx) +{ + mlfiPriv *priv = MLFIPRIV; + if (!priv) return SMFIS_CONTINUE; + delete priv; + smfi_setpriv(ctx, NULL); + return SMFIS_CONTINUE; +} + +struct smfiDesc smfilter = +{ + "DNSBL", // filter name + SMFI_VERSION, // version code -- do not change + SMFIF_DELRCPT, // flags + mlfi_connect, // connection info filter + NULL, // SMTP HELO command filter + mlfi_envfrom, // envelope sender filter + mlfi_envrcpt, // envelope recipient filter + NULL, // header filter + NULL, // end of header + mlfi_body, // body block filter + mlfi_eom, // end of message + mlfi_abort, // message aborted + mlfi_close, // connection cleanup +}; + + +//////////////////////////////////////////////// +// reload the config +// +static CONFIG* new_conf(); +static CONFIG* new_conf() { + CONFIG *newc = new CONFIG; + pthread_mutex_lock(&config_mutex); + newc->generation = generation++; + pthread_mutex_unlock(&config_mutex); + char buf[200]; + snprintf(buf, sizeof(buf), "loading configuration generation %d", newc->generation); + my_syslog(buf); + if (load_conf(*newc, "dnsbl.conf") { + newc->load_time = time(NULL); + return newc; + } + delete newc; + return NULL; +} + + +//////////////////////////////////////////////// +// thread to watch the old config files for changes +// and reload when needed. we also cleanup old +// configs whose reference count has gone to zero. +// +static void* config_loader(void *arg); +static void* config_loader(void *arg) { + typedef set<CONFIG *> configp_set; + configp_set old_configs; + while (loader_run) { + sleep(180); // look for modifications every 3 minutes + if (!loader_run) break; + CONFIG &dc = *config; + time_t then = dc.load_time; + struct stat st; + bool reload = false; + for (string_list::iterator i=dc.config_files.begin(); i!=dc.config_files.end(); i++) { + char *fn = *i; + if (stat(fn, &st)) reload = true; // file disappeared + else if (st.st_mtime > then) reload = true; // file modified + if (reload) break; + } + if (reload) { + CONFIG *newc = new_conf(); + // replace the global config pointer + pthread_mutex_lock(&config_mutex); + CONFIG *old = config; + config = newc; + pthread_mutex_unlock(&config_mutex); + if (old) old_configs.insert(old); + } + // now look for old configs with zero ref counts + for (configp_set::iterator i=old_configs.begin(); i!=old_configs.end(); ) { + CONFIG *old = *i; + if (!old->reference_count) { + char buf[200]; + snprintf(buf, sizeof(buf), "freeing memory for old configuration generation %d", old->generation); + my_syslog(buf); + delete old; // destructor does all the work + old_configs.erase(i++); + } + else i++; + } + } + return NULL; +} + + +static void usage(char *prog); +static void usage(char *prog) +{ + fprintf(stderr, "Usage: %s [-d] [-c] -r port -p sm-sock-addr [-t timeout]\n", prog); + fprintf(stderr, "where port is for the connection to our own dns resolver processes\n"); + fprintf(stderr, " and should be local-domain-socket-file-name\n"); + fprintf(stderr, "where sm-sock-addr is for the connection to sendmail\n"); + fprintf(stderr, " and should be one of\n"); + fprintf(stderr, " inet:port@ip-address\n"); + fprintf(stderr, " local:local-domain-socket-file-name\n"); + fprintf(stderr, "-c will load and dump the config to stdout\n"); + fprintf(stderr, "-d will add some syslog debug messages\n"); +} + + + +static void setup_socket(char *sock); +static void setup_socket(char *sock) { + unlink(sock); + // sockaddr_un addr; + // memset(&addr, '\0', sizeof addr); + // addr.sun_family = AF_UNIX; + // strncpy(addr.sun_path, sock, sizeof(addr.sun_path)-1); + // int s = socket(AF_UNIX, SOCK_STREAM, 0); + // bind(s, (sockaddr*)&addr, sizeof(addr)); + // close(s); +} + + +/* + * The signal handler function -- only gets called when a SIGCHLD + * is received, ie when a child terminates + */ +void sig_chld(int signo) +{ + int status; + /* Wait for any child without blocking */ + while (waitpid(-1, &status, WNOHANG) > 0) { + // ignore child exit status, we only do this to cleanup zombies + } +} + + +int main(int argc, char**argv) +{ + token_init(); + bool check = false; + bool setconn = false; + bool setreso = false; + int c; + const char *args = "r:p:t:hcd"; + extern char *optarg; + + // Process command line options + while ((c = getopt(argc, argv, args)) != -1) { + switch (c) { + case 'r': + if (optarg == NULL || *optarg == '\0') { + fprintf(stderr, "Illegal resolver socket: %s\n", optarg); + exit(EX_USAGE); + } + resolver_port = strdup(optarg); + setup_socket(resolver_port); + setreso = true; + break; + + case 'p': + if (optarg == NULL || *optarg == '\0') { + fprintf(stderr, "Illegal sendmail socket: %s\n", optarg); + exit(EX_USAGE); + } + if (smfi_setconn(optarg) == MI_FAILURE) { + fprintf(stderr, "smfi_setconn failed\n"); + exit(EX_SOFTWARE); + } + if (strncasecmp(optarg, "unix:", 5) == 0) setup_socket(optarg + 5); + else if (strncasecmp(optarg, "local:", 6) == 0) setup_socket(optarg + 6); + setconn = true; + break; + + case 't': + if (optarg == NULL || *optarg == '\0') { + fprintf(stderr, "Illegal timeout: %s\n", optarg); + exit(EX_USAGE); + } + if (smfi_settimeout(atoi(optarg)) == MI_FAILURE) { + fprintf(stderr, "smfi_settimeout failed\n"); + exit(EX_SOFTWARE); + } + break; + + case 'c': + check = true; + break; + + case 'd': + debug_syslog = true; + break; + + case 'h': + default: + usage(argv[0]); + exit(EX_USAGE); + } + } + + if (check) { + CONFIG *conf = new_conf(); + if (conf) { + conf->dump(); + delete conf; + return 0; + } + else { + return 1; // config failed to load + } + } + + if (!setconn) { + fprintf(stderr, "%s: Missing required -p argument\n", argv[0]); + usage(argv[0]); + exit(EX_USAGE); + } + + if (!setreso) { + fprintf(stderr, "%s: Missing required -r argument\n", argv[0]); + usage(argv[0]); + exit(EX_USAGE); + } + + if (smfi_register(smfilter) == MI_FAILURE) { + fprintf(stderr, "smfi_register failed\n"); + exit(EX_UNAVAILABLE); + } + + // switch to background mode + if (daemon(1,0) < 0) { + fprintf(stderr, "daemon() call failed\n"); + exit(EX_UNAVAILABLE); + } + + // write the pid + const char *pidpath = "/var/run/dnsbl.pid"; + unlink(pidpath); + FILE *f = fopen(pidpath, "w"); + if (f) { +#ifdef linux + // from a comment in the DCC source code: + // Linux threads are broken. Signals given the + // original process are delivered to only the + // thread that happens to have that PID. The + // sendmail libmilter thread that needs to hear + // SIGINT and other signals does not, and that breaks + // scripts that need to stop milters. + // However, signaling the process group works. + fprintf(f, "-%d\n", (u_int)getpgrp()); +#else + fprintf(f, "%d\n", (u_int)getpid()); +#endif + fclose(f); + } + + // initialize the thread sync objects + pthread_mutex_init(&config_mutex, 0); + pthread_mutex_init(&syslog_mutex, 0); + pthread_mutex_init(&resolve_mutex, 0); + pthread_mutex_init(&fd_pool_mutex, 0); + + // drop root privs + struct passwd *pw = getpwnam("dnsbl"); + if (pw) { + if (setgid(pw->pw_gid) == -1) { + my_syslog("failed to switch to group dnsbl"); + } + if (setuid(pw->pw_uid) == -1) { + my_syslog("failed to switch to user dnsbl"); + } + } + + // fork off the resolver listener process + pid_t child = fork(); + if (child < 0) { + my_syslog("failed to create resolver listener process"); + exit(0); + } + if (child == 0) { + // we are the child - dns resolver listener process + resolver_socket = socket(AF_UNIX, SOCK_STREAM, 0); + if (resolver_socket < 0) { + my_syslog("child failed to create resolver socket"); + exit(0); // failed + } + sockaddr_un server; + memset(&server, '\0', sizeof(server)); + server.sun_family = AF_UNIX; + strncpy(server.sun_path, resolver_port, sizeof(server.sun_path)-1); + //try to bind the address to the socket. + if (bind(resolver_socket, (sockaddr *)&server, sizeof(server)) < 0) { + // bind failed + shutdown(resolver_socket, SHUT_RDWR); + close(resolver_socket); + my_syslog("child failed to bind resolver socket"); + exit(0); // failed + } + //listen on the socket. + if (listen(resolver_socket, 10) < 0) { + // listen failed + shutdown(resolver_socket, SHUT_RDWR); + close(resolver_socket); + my_syslog("child failed to listen to resolver socket"); + exit(0); // failed + } + // setup sigchld handler to prevent zombies + struct sigaction act; + act.sa_handler = sig_chld; // Assign sig_chld as our SIGCHLD handler + sigemptyset(&act.sa_mask); // We don't want to block any other signals in this example + act.sa_flags = SA_NOCLDSTOP; // only want children that have terminated + if (sigaction(SIGCHLD, &act, NULL) < 0) { + my_syslog("child failed to setup SIGCHLD handler"); + exit(0); // failed + } + while (true) { + sockaddr_un client; + socklen_t clientlen = sizeof(client); + int s = accept(resolver_socket, (sockaddr *)&client, &clientlen); + if (s > 0) { + // accept worked, it did not get cancelled before we could accept it + // fork off a process to handle this connection + int newchild = fork(); + if (newchild == 0) { + // this is the worker process + // child does not need the listening socket + close(resolver_socket); + //my_syslog("child forked a worker process"); + process_resolver_requests(s); + //my_syslog("child terminated a worker process"); + exit(0); + } + else { + // this is the parent + // parent does not need the accepted socket + close(s); + } + } + } + exit(0); // make sure we don't fall thru. + } + else { + sleep(2); // allow child to get started + } + + // load the initial config + config = new_conf(); + + // only create threads after the fork() in daemon + pthread_t tid; + if (pthread_create(&tid, 0, config_loader, 0)) + my_syslog("failed to create config loader thread"); + if (pthread_detach(tid)) + my_syslog("failed to detach config loader thread"); + + time_t starting = time(NULL); + int rc = smfi_main(); + if ((rc != MI_SUCCESS) && (time(NULL) > starting+5*60)) { + my_syslog("trying to restart after smfi_main()"); + loader_run = false; // eventually the config loader thread will terminate + execvp(argv[0], argv); + } + exit((rc == MI_SUCCESS) ? 0 : EX_UNAVAILABLE); +} +