path: root/src/qmail-smtpam.c

#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#include "alloc.h"
#include "buffer.h"
#include "byte.h"
#include "case.h"
#include "constmap.h"
#include "error.h"
#include "exit.h"
#include "genalloc.h"
#include "ip.h"
#include "scan.h"
#include "sig.h"
#include "socket_if.h"
#include "str.h"
#include "stralloc.h"
#include "timeout.h"
#include "timeoutconn.h"
#include "uint_t.h"

#include "control.h"
#include "dns.h"
#include "ipalloc.h"
#include "ipme.h"
#include "now.h"
#include "quote.h"
#include "tcpto.h"
#include "tls_errors.h"
#include "tls_remote.h"
#include "tls_timeoutio.h"
#include "ucspissl.h"

#ifdef USE_CONFIG
  #include "fehsqm-config.h"
#else
  #include "auto_qmail.h"
#endif

#define MAX_SIZE     200000000
#define HUGESMTPTEXT 5000
#define PORT_SMTP    25  // silly rabbit, /etc/services is for users
#define PORT_SMTPS   465
#define VERIFYDEPTH  1
#define FDPAM        3

#define WHO "qmail-smtpam"

/**
 * @file qmail-smtpam.c -- TLS enabled SMTP PAM to check mailbox at remote MX
 */

int flagauth = 0;   /* 1 = login; 2 = plain; 3 =crammd5 */
int flagsmtps = 0;  /* RFC 8314 - 'implicit TLS' */
int flagtls = 0;    /* -2 = rejected; -1 = not; 0 = no, default;
                            > 0 see tls_remote.c
                          +10 = SMTPS; +20 = QMTPS; 100 = active TLS connection */
int flagverify = 0; /* 1 = verify Cert against CA ; -1 = Cert pinning */
int flagutf8mail = 0;

unsigned long port = PORT_SMTP;

GEN_ALLOC_typedef(saa, stralloc, sa, len, a);
GEN_ALLOC_readyplus(saa, stralloc, sa, len, a, i, n, x, 10, saa_readyplus);

stralloc helohost = {0};
stralloc host = {0};
stralloc ports = {0};
stralloc remotehost = {0};
stralloc sender = {0};
stralloc canonhost = {0};
stralloc canonbox = {0};
stralloc sendip = {0};
stralloc recipient = {0};

stralloc domainips = {0};
struct constmap mapdomainips;
char ip4[4];
char ip6[16];
uint32 ifidx = 0;

stralloc routes = {0};
struct constmap maproutes;

struct ip_mx partner;

SSL *ssl;
SSL_CTX *ctx;

void out(char *s)
{
  if (buffer_puts(buffer_1small, s) == -1) _exit(111);
}

static void zero()
{
  if (buffer_put(buffer_1small, "\0", 1) == -1) _exit(111);
}

void zerodie()
{
  zero();
  buffer_flush(buffer_1small);
  _exit(111);
}

void outsafe(stralloc *sa)
{
  int i;
  char ch;
  for (i = 0; i < sa->len; ++i) {
    ch = sa->s[i];
    if (ch < 33) ch = '?';
    if (ch > 126) ch = '?';
    if (buffer_put(buffer_1small, &ch, 1) == -1) _exit(111);
  }
}

static void temp_noip()
{
  out("Zinvalid ipaddr in control/domainips (#4.3.0)\n");
  zerodie();
}

void temp_nomem()
{
  out("ZOut of memory. (#4.3.0)\n");
  zerodie();
}

static void temp_oserr()
{
  out("ZSystem resources temporarily unavailable. (#4.3.0)\n");
  zerodie();
}

static void temp_osip()
{
  out("ZCan't bind to local ip address: ");
  outsafe(&sendip);
  out(". (#4.3.0)\n");
  zerodie();
}

static void temp_noconn()
{
  out("ZSorry, I wasn't able to establish an SMTP connection. (#4.4.1)\n");
  zerodie();
}

static void temp_dnscanon()
{
  out("ZCNAME lookup failed temporarily for: ");
  outsafe(&canonhost);
  out(". (#4.4.3)\n");
  zerodie();
}

static void temp_dns()
{
  out("ZSorry, I couldn't find any host named: ");
  outsafe(&host);
  out(". (#4.1.2)\n");
  zerodie();
}

static void temp_chdir()
{
  out("ZUnable to switch to home directory. (#4.3.0)\n");
  zerodie();
}

static void temp_control()
{
  out("ZUnable to read control files. (#4.3.0)\n");
  zerodie();
}

static void perm_usage()
{
  out("Dqmail-smtpam was invoked improperly. (#5.3.5)\n");
  zerodie();
}

static void perm_dns()
{
  out("DSorry, I couldn't find any host named: ");
  outsafe(&host);
  out(". (#5.1.2)\n");
  zerodie();
}

static void outhost()
{
  char ipaddr[IPFMT];
  int len;

  switch (partner.af) {
    case AF_INET:  len = ip4_fmt(ipaddr, (char *)&partner.addr.ip4.d); break;
    case AF_INET6: len = ip6_fmt(ipaddr, (char *)&partner.addr.ip6.d); break;
  }
  if (buffer_put(buffer_1small, ipaddr, len) == -1) _exit(0);
}

int flagcritical = 0;

static void dropped()
{
  out("ZConnected to ");
  outhost();
  out(" but connection died. ");
  if (flagcritical) out("Possible duplicate! ");
  out("(#4.4.2)\n");
  zerodie();
}

long timeoutconnect = 60;
int smtpfd;
long timeout = 1200;

static ssize_t saferead(int fd, char *buf, int len)
{
  int r;
  r = timeoutread(timeout, smtpfd, buf, len);
  if (r <= 0) dropped();
  return r;
}

static ssize_t safewrite(int fd, char *buf, int len)
{
  int r;
  r = timeoutwrite(timeout, smtpfd, buf, len);
  if (r <= 0) dropped();
  return r;
}

char outbuf[1450];
buffer bo = BUFFER_INIT(safewrite, -1, outbuf, sizeof(outbuf));
char frombuf[128];
buffer bi = BUFFER_INIT(saferead, -1, frombuf, sizeof(frombuf));

stralloc smtptext = {0};

static void get(char *ch)
{
  buffer_get(&bi, ch, 1);
  if (*ch != '\r')
    if (smtptext.len < HUGESMTPTEXT)
      if (!stralloc_append(&smtptext, ch)) temp_nomem();
}

static unsigned long smtpcode()
{
  unsigned char ch;
  unsigned long code;

  if (!stralloc_copys(&smtptext, "")) temp_nomem();

  get(&ch);
  code = ch - '0';
  get(&ch);
  code = code * 10 + (ch - '0');
  get(&ch);
  code = code * 10 + (ch - '0');
  for (;;) {
    get(&ch);
    if (ch != '-') break;
    while (ch != '\n') get(&ch);
    get(&ch);
    get(&ch);
    get(&ch);
  }
  while (ch != '\n') get(&ch);

  return code;
}

static void outsmtptext()
{
  int i;
  if (smtptext.s) {
    if (smtptext.len) {
      out("Remote host said: ");
      for (i = 0; i < smtptext.len; ++i)
        if (!smtptext.s[i]) smtptext.s[i] = '?';
      if (buffer_put(buffer_1small, smtptext.s, smtptext.len) == -1) _exit(111);
      smtptext.len = 0;
    }
  }
}

static void quit(char *prepend, char *append)
{
  buffer_putsflush(&bo, "QUIT\r\n");
  /* waiting for remote side is just too ridiculous */
  out(prepend);
  outhost();
  out(append);
  out(".\n");
  outsmtptext();
  zerodie();
}

stralloc recip = {0};

/* this file is too long -------------------------------------- client TLS */

stralloc cafile = {0};
stralloc cadir = {0};
stralloc certfile = {0};
stralloc keyfile = {0};
stralloc keypwd = {0};
stralloc ciphers = {0};
stralloc tlsdest = {0};

char *tlsdestinfo = 0;
char *tlsdomaininfo = 0;

stralloc domaincerts = {0};
struct constmap mapdomaincerts;
stralloc tlsdestinations = {0};
struct constmap maptlsdestinations;
unsigned long verifydepth = VERIFYDEPTH;

static void tls_init()
{
  /* Client CTX */

  ctx = ssl_client();
  ssl_errstr();
  if (!ctx) temp_tlsctx();

  /* Fetch CA infos for dest */

  if (flagverify > 0)
    if (cafile.len || cadir.len)
      if (!ssl_ca(ctx, cafile.s, cadir.s, (int)verifydepth)) temp_tlsca();

  if (ciphers.len)
    if (!ssl_ciphers(ctx, ciphers.s)) temp_tlscipher();

  /* Set SSL Context */

  ssl = ssl_new(ctx, smtpfd);
  if (!ssl) temp_tlsctx();

  /* Setup SSL FDs */

  if (!tls_conn(ssl, smtpfd)) temp_tlscon();

  /* Go on in none-blocking mode */

  if (tls_timeoutconn(timeout, smtpfd, smtpfd, ssl) <= 0) temp_tlserr();
}

static int starttls_peer()
{
  int i = 0;

  while ((i += str_chr(smtptext.s + i, '\n') + 1) && (i < smtptext.len - 8)) {
    if (!str_diffn(smtptext.s + i + 4, "STARTTLS", 8)) return 1;
  }

  return 0;
}

static void tls_peercheck()
{
  X509 *cert;

  cert = SSL_get_peer_certificate(ssl);
  if (!cert) {
    flagtls = 100;
    return;
  }

  if (flagverify < 0) {
    if (cafile.len) case_lowerb(cafile.s, cafile.len);
    switch (tls_fingerprint(cert, cafile.s + 1, cafile.len - 1)) {
      case -1: temp_tlspeercert();
      case -2: temp_tlsdigest();
      case -3: temp_invaliddigest();
      case 1:  temp_tlscertfp();
    }
  } else {
    switch (tls_checkpeer(ssl, cert, remotehost, flagtls, flagverify)) {
      case -1: temp_tlspeercert();
      case -2: temp_tlspeerverify();
      case -3: temp_tlspeervalid();
      case 1:  flagtls = 101; break;
      case 2:  flagtls = 102; break;
      case 3:  flagtls = 103; break;
    }
  }

  if (flagtls < 100) flagtls = 100;

  X509_free(cert);

  return;
}

static int utf8flag(unsigned char *ch, int len)
{
  int i = 0;
  while (i < len)
    if (ch[i++] > 127) return 1;
  return 0;
}

/* this file is too long -------------------------------------- SMTP connection */

unsigned long code;

static void smtp_greeting()
{
  buffer_puts(&bo, "EHLO ");
  buffer_put(&bo, helohost.s, helohost.len);
  buffer_puts(&bo, "\r\n");
  buffer_flush(&bo);

  if (smtpcode() != 250) {
    buffer_puts(&bo, "HELO ");
    buffer_put(&bo, helohost.s, helohost.len);
    buffer_puts(&bo, "\r\n");
    buffer_flush(&bo);
    code = smtpcode();
    if (code >= 500) quit("DConnected to", " but my name was rejected");
    if (code != 250) quit("ZConnected to", " but my name was rejected");
  }
}

static void smtp_starttls()
{
  buffer_puts(&bo, "STARTTLS\r\n");
  buffer_flush(&bo);
  if (smtpcode() == 220) {
    tls_init();
    tls_peercheck();
    smtp_greeting();
  } else {
    flagtls = -2;
    quit("ZConnected to", " but STARTTLS was rejected");
  }
}

static void smtp()
{

  if (flagtls > 10 && flagtls < 20) { /* SMTPS */
    tls_init();
    tls_peercheck();
  }

  code = smtpcode();
  if (code >= 500) quit("DConnected to ", " but sender was rejected");
  if (code >= 400) quit("ZConnected to ", " but sender was probably greylisted");

  smtp_greeting();

  if (flagutf8mail) buffer_puts(&bo, " SMTPUTF8");

  if (flagtls > 0 && flagtls < 10) { /* STARTTLS */
    if (starttls_peer()) {
      smtp_starttls();
    } else if (flagtls > 2) {
      temp_tlshost();
    }
  }

  buffer_puts(&bo, "MAIL FROM:<>");
  if (flagutf8mail) buffer_puts(&bo, " SMTPUTF8");
  buffer_puts(&bo, "\r\n");
  buffer_flush(&bo);
  code = smtpcode();
  if (code >= 500) quit("DConnected to ", " but sender was rejected");
  if (code >= 400) quit("ZConnected to ", " but sender was rejected");

  buffer_puts(&bo, "RCPT TO:<");
  buffer_put(&bo, recipient.s, recipient.len);
  buffer_puts(&bo, ">\r\n");
  buffer_flush(&bo);
  code = smtpcode();
  close(smtpfd);
  if (code == 250) _exit(0);
  _exit(1);
}

static void getcontrols()
{
  if (control_init() == -1) temp_control();
  if (control_readint(&timeout, "control/timeoutremote") == -1) temp_control();
  if (control_readint(&timeoutconnect, "control/timeoutconnect") == -1) temp_control();
  if (control_rldef(&helohost, "control/helohost", 1, (char *)0) != 1) temp_control();
  switch (control_readfile(&domainips, "control/domainips", 0)) {
    case -1: temp_control();
    case 0:
      if (!constmap_init(&mapdomainips, "", 0, 1)) temp_nomem();
      break;
    case 1:
      if (!constmap_init(&mapdomainips, domainips.s, domainips.len, 1)) temp_nomem();
      break;
  }
  switch (control_readfile(&tlsdestinations, "control/tlsdestinations", 0)) {
    case -1: temp_control();
    case 0:
      if (!constmap_init(&maptlsdestinations, "", 0, 1)) temp_nomem();
      break;
    case 1:
      if (!constmap_init(&maptlsdestinations, tlsdestinations.s, tlsdestinations.len, 1)) temp_nomem();
      break;
  }
}

char up[513];
int uplen;

int main(int argc, char **argv)
{
  static ipalloc ip = {0};
  stralloc netif = {0};
  int i, j, k;
  int r; /* reserved for return code */
  int p; /* reserved for port */
  char *localip = 0;
  char *tlsdestinfo = 0;

  sig_pipeignore();
  if (argc < 2) perm_usage();
  if (chdir(auto_qmail) == -1) temp_chdir();
  getcontrols();

  if (!stralloc_copys(&host, argv[1])) temp_nomem();

  if (argv[2]) {
    if (!stralloc_copys(&ports, argv[2])) temp_nomem();
    if (*ports.s == 's') {
      ports.s++;
      flagsmtps = 1;
    }
    scan_ulong(ports.s, &port);
  }

  if (ipme_init() != 1) temp_oserr();

  /* this file is too long -------------------------------------- set domain ip + helohost  */

  if (!localip) localip = constmap(&mapdomainips, "*", 1); /* one for all */

  if (localip) {
    j = str_chr(localip, '%');
    if (localip[j] != '%') j = 0;
    k = str_chr(localip, '|');
    if (localip[k] != '|') k = 0;
    if (k) { /* helohost */
      if (!stralloc_copys(&helohost, localip + k + 1)) temp_nomem();
      localip[k] = 0;
    }
    if (j) { /* if index */
      localip[j] = 0;
      if (!stralloc_copys(&netif, localip + j + 1)) temp_nomem();
      if (!stralloc_0(&netif)) temp_nomem();
    }
  }


  /* this file is too long -------------------------------------- TLS destinations */

  flagtls = tls_destination((const stralloc)host);  // un-terminated

  if (flagtls > 0) {
    if (tlsdestinfo) {
      i = str_chr(tlsdestinfo, '|'); /* ca file or cert fingerprint */
      if (tlsdestinfo[i] == '|') {
        tlsdestinfo[i] = 0;
        j = str_chr(tlsdestinfo + i + 1, '|'); /* cipher */
        if (tlsdestinfo[i + j + 1] == '|') {
          tlsdestinfo[i + j + 1] = 0;
          k = str_chr(tlsdestinfo + i + j + 2, '|'); /* cone domain */
          if (tlsdestinfo[i + j + k + 2] == '|') {
            tlsdestinfo[i + j + k + 2] = 0;
            if (str_diffn(tlsdestinfo + j + k + 3, canonhost.s, canonhost.len)) flagtls = 0;
          }
          p = str_chr(tlsdestinfo + i + j + 2, ';'); /* verifydepth;port */
          if (tlsdestinfo[i + j + p + 2] == ';') {
            if (tlsdestinfo[i + j + p + 3] == 's') {
              flagsmtps = 1;
              p++;
            }
            tlsdestinfo[i + j + p + 2] = 0;
            if (p > 0) scan_ulong(tlsdestinfo + i + j + 2, &verifydepth);
            scan_ulong(tlsdestinfo + i + j + p + 3, &port);
          }
        }
        if (!stralloc_copys(&ciphers, tlsdestinfo + i + 1)) temp_nomem();
      }
      if (!stralloc_copys(&cafile, tlsdestinfo)) temp_nomem();
    }

    /* cafile starts with '=' => it is a fingerprint
   cafile ends with '/'  => consider it as cadir */

    if (cafile.len) {
      flagverify = 1;
      if (cafile.s[cafile.len] == '/') {
        cafile.len = 0;
        flagverify = 2;
        if (!stralloc_copys(&cadir, tlsdestinfo)) temp_nomem();
        if (!stralloc_0(&cadir)) temp_nomem();
      } else {
        if (cafile.s[0] == '%') flagverify = -1;
        if (!stralloc_0(&cafile)) temp_nomem();
      }
    } else {
      cafile.len = cadir.len = ciphers.len = p = 0;
    }

    if (port == PORT_SMTPS || flagsmtps) flagtls = flagtls + 10;
  }

  /* this file is too long -------------------------------------- Setup connection */

  uplen = 0;
  for (;;) {
    do r = read(FDPAM, up + uplen, sizeof(up) - uplen);
    while ((r == -1) && (errno == EINTR));
    if (r == -1) _exit(111);
    if (r == 0) break;
    uplen += r;
    if (uplen >= sizeof(up)) _exit(111);
  }
  close(FDPAM);

  if (!stralloc_copyb(&recipient, up, uplen)) temp_nomem();
  if (!stralloc_0(&recipient)) temp_nomem();
  if (!stralloc_0(&host)) temp_nomem();
  if (!stralloc_copys(&remotehost, host.s)) temp_nomem();

  flagutf8mail = utf8flag(recipient.s, recipient.len);

  switch (dns_ip(&ip, &remotehost)) {
    case DNS_MEM: temp_nomem();
    case DNS_ERR: temp_dns();
    case DNS_COM: temp_dnscanon();
    default:
      if (ip.len <= 0) perm_dns();
  }

  smtpfd = socket(ip.ix[i].af, SOCK_STREAM, 0);
  if (smtpfd == -1) temp_oserr();

  if (localip) { /* set domain ip */
    if (!stralloc_copyb(&sendip, localip, str_len(localip))) temp_nomem();
    j = str_chr(localip, ':');
    if (j && localip[j] == ':') { /* IPv6 */
      if (!ip6_scan(localip, ip6)) temp_noip();
      ifidx = socket_getifidx(netif.s);
      if (socket_bind6(smtpfd, ip6, 0, ifidx) < 0) temp_osip();
    } else { /* IPv4 */
      if (!ip4_scan(localip, ip4)) temp_noip();
      if (socket_bind4(smtpfd, ip4, 0) < 0) temp_osip();
    }
  }

  r = timeoutconn(smtpfd, ip.ix[i].addr.ip4.d, (unsigned int)port, timeoutconnect, ifidx);
  if (r == 0) {
    tcpto_err(&ip.ix[i], 0);
    partner = ip.ix[i];
    smtp(); /* does not return */
  }
  tcpto_err(&ip.ix[i], errno == ETIMEDOUT);
  close(smtpfd);

  temp_noconn();
}