plugin-rbl.c

#include <string.h>

#include <bglibs/msg.h>
#include <bglibs/wrap.h>
#include <bglibs/dns.h>
#include <bglibs/ipv4.h>
#include <bglibs/str.h>

#include "mailfront.h"

static enum msgstatus { na, good, bad } msgstatus;

static response rbl_blocked;
static RESPONSE(dnserror, 451, "4.3.0 DNS error doing RBL lookup");
static int debug = 0;
static int queuedir = 0;

static const response* make_response(int code, const char* status, const char* msg)
{
  static str resp_str;
  unsigned int i;
  if (!str_copyf(&resp_str, "s{: }s", status, msg))
    return &resp_oom;
  for (i = 0; i < resp_str.len; ++i)
    if (resp_str.s[i] < 32 || resp_str.s[i] > 126)
      resp_str.s[i] = '?';
  rbl_blocked.number = code;
  rbl_blocked.message = resp_str.s;
  return 0;
}

static const char* make_name(const ipv4addr* ip, const char* rbl)
{
  char iprbuf[16];
  static str name;
  wrap_str(str_copyb(&name, iprbuf, fmt_ipv4addr_reverse(iprbuf, ip)));
  wrap_str(str_catc(&name, '.'));
  wrap_str(str_cats(&name, rbl));
  return name.s;
}

static const response* test_rbl(const char* rbl, enum msgstatus status, const ipv4addr* ip)
{
  static struct dns_result txt;
  int i;
  const char* query = make_name(ip, rbl);
  const response* resp = NULL;

  if (dns_txt(&txt, query) < 0)
    return &resp_dnserror;
  if (txt.count > 0) {
    if (debug) {
      str lines = {0};
      for (i = 0; i < txt.count; ++i) {
        if (lines.len > 0)
          wrap_str(str_cats(&lines, " // "));
        wrap_str(str_cats(&lines, txt.rr.name[i]));
      }
      msgf("{rbl: }s{ by }s{: }S", (status == good) ? "whitelisted" : "blacklisted", rbl, &lines);
      str_free(&lines);
    }
    msgstatus = status;
    resp = make_response(451, "Blocked", txt.rr.name[0]); /* 451 temporary, 553 permanent */
  }
  dns_result_free(&txt);
  return resp;
}

static const response* test_rbls(const char* rbls, enum msgstatus status, const ipv4addr* ip)
{
  const char* comma;
  const response* r;
  static str rbl;
  while ((comma = strchr(rbls, ',')) != 0) {
    wrap_str(str_copyb(&rbl, rbls, comma-rbls));
    if ((r = test_rbl(rbl.s, status, ip)) != 0)
      return r;
    rbls = comma + 1;
  }
  return test_rbl(rbls, status, ip);
}

static const response* init(void)
{
  const char* blacklist;
  const char* whitelist;
  const response* r;
  const char* e;
  ipv4addr ip;

  debug = session_getenv("RBL_DEBUG") != 0;

  if ((blacklist = session_getenv("RBL_BLACKLISTS")) == 0 || *blacklist == 0) {
    if (debug)
      msg1("{rbl: No blacklists, skipping}");
    return 0;
  }

  queuedir = session_getenv("RBL_QUEUEDIR") != 0;
  if (queuedir)
    queuedir_init("RBL_QUEUEDIR");

  /* Can only handle IPv4 sessions */
  if ((e = session_getenv("TCPREMOTEIP")) == 0) {
    if (debug)
      msg1("{rbl: $TCPREMOTEIP is unset, skipping RBL tests}");
    return 0;
  }
  if (!ipv4_scan(e, &ip)) {
    msgf("{rbl: Cannot parse IP '}s{'}", e);
    return 0;
  }

  whitelist = session_getenv("RBL_WHITELISTS");
  if (whitelist != NULL && *whitelist != 0)
    if ((r = test_rbls(whitelist, good, &ip)) != NULL)
      return r;

  if (msgstatus == na
      && (r = test_rbls(blacklist, bad, &ip)) != 0)
    return r;
  return 0;
}

static const response* sender(str* address, str* params)
{
  const response* r;
  if (msgstatus == bad) {
    if (queuedir) {
      if ((r = queuedir_sender(address, params)) != 0)
	return r;
    }
    else
      return &rbl_blocked;
  }
  return 0;
}

static const response* recipient(str* address, str* params)
{
  return queuedir && msgstatus == bad ? queuedir_recipient(address, params): 0;
}

static const response* data_start(int fd)
{
  return queuedir && msgstatus == bad ? queuedir_data_start(fd) : 0;
}

static const response* data_block(const char* bytes, unsigned long len)
{
  return queuedir && msgstatus == bad ? queuedir_data_block(bytes, len) : 0;
}

static const response* message_end(int fd)
{
  const response* r;
  if (msgstatus == bad) {
    if (queuedir) {
      if ((r = queuedir_message_end(fd)) != 0)
	return r;
    }
    return &rbl_blocked;
  }
  return 0;
}

struct plugin plugin = {
  .version = PLUGIN_VERSION,
  .flags = 0,
  .init = init,
  .reset = queuedir_reset,
  .sender = sender,
  .recipient = recipient,
  .data_start = data_start,
  .data_block = data_block,
  .message_end = message_end,
};