Fix Proxy Protocol v2 handling

Change recv() to not use MSGPEEK and eliminated flush_input().
Add proxy_target_address/port expansions.
Convert ipv6 decoding to memmove().
Use sizeof() for variable sizing.
Correct struct member access.
Enhance debug output when passed invalid command/family.
Add to and enhance documentation.
Client script to test Proxy Protocol, interactive on STDIN/STDOUT,
  so can be chained (ie a swaks pipe), useful for any service, not
  just Exim and/or smtp.

5 files changed, 330 insertions, 39 deletions

diff --git a/src/src/expand.c b/src/src/expand.c
index d2ac8ca79..7e8c2b49d 100644
--- a/src/src/expand.c
+++ b/src/src/expand.c
@@ -565,6 +565,8 @@ static var_entry var_table[] = {
   { "proxy_host_address",  vtype_stringptr,   &proxy_host_address },
   { "proxy_host_port",     vtype_int,         &proxy_host_port },
   { "proxy_session",       vtype_bool,        &proxy_session },
+  { "proxy_target_address",vtype_stringptr,   &proxy_target_address },
+  { "proxy_target_port",   vtype_int,         &proxy_target_port },
 #endif
   { "prvscheck_address",   vtype_stringptr,   &prvscheck_address },
   { "prvscheck_keynum",    vtype_stringptr,   &prvscheck_keynum },
diff --git a/src/src/globals.c b/src/src/globals.c
index 839b91dcc..38bd37bce 100644
--- a/src/src/globals.c
+++ b/src/src/globals.c
@@ -925,6 +925,8 @@ int     proxy_host_port        = 0;
 uschar *proxy_required_hosts   = US"";
 BOOL    proxy_session          = FALSE;
 BOOL    proxy_session_failed   = FALSE;
+uschar *proxy_target_address   = US"";
+int     proxy_target_port      = 0;
 #endif
 
 uschar *prvscheck_address      = NULL;
diff --git a/src/src/globals.h b/src/src/globals.h
index 1cc39fc09..b229c1a07 100644
--- a/src/src/globals.h
+++ b/src/src/globals.h
@@ -595,11 +595,13 @@ extern uschar *process_log_path;       /* Alternate path */
 extern BOOL    prod_requires_admin;    /* TRUE if prodding requires admin */
 
 #ifdef EXPERIMENTAL_PROXY
-extern uschar *proxy_host_address;     /* IP of proxy server */
-extern int     proxy_host_port;        /* Port of proxy server */
+extern uschar *proxy_host_address;     /* IP of host being proxied */
+extern int     proxy_host_port;        /* Port of host being proxied */
 extern uschar *proxy_required_hosts;   /* Hostlist which (require) use proxy protocol */
 extern BOOL    proxy_session;          /* TRUE if receiving mail from valid proxy  */
 extern BOOL    proxy_session_failed;   /* TRUE if required proxy negotiation failed */
+extern uschar *proxy_target_address;   /* IP of proxy server inbound */
+extern int     proxy_target_port;      /* Port of proxy server inbound */
 #endif
 
 extern uschar *prvscheck_address;      /* Set during prvscheck expansion item */
diff --git a/src/src/smtp_in.c b/src/src/smtp_in.c
index 2a3873d33..7fe00be12 100644
--- a/src/src/smtp_in.c
+++ b/src/src/smtp_in.c
@@ -603,22 +603,6 @@ return proxy_session;
 
 
 /*************************************************
-*           Flush waiting input string           *
-*************************************************/
-static void
-flush_input()
-{
-int rc;
-
-rc = smtp_getc();
-while (rc != '\n')             /* End of input string */
-  {
-  rc = smtp_getc();
-  }
-}
-
-
-/*************************************************
 *         Setup host for proxy protocol          *
 *************************************************/
 /* The function configures the connection based on a header from the
@@ -664,12 +648,18 @@ union {
   } v2;
 } hdr;
 
+/* Temp variables used in PPv2 address:port parsing */
+uint16_t tmpport;
+char tmpip[INET_ADDRSTRLEN];
+struct sockaddr_in tmpaddr;
+char tmpip6[INET6_ADDRSTRLEN];
+struct sockaddr_in6 tmpaddr6;
+
+int get_ok = 0;
 int size, ret, fd;
-uschar *tmpip;
 const char v2sig[13] = "\x0D\x0A\x0D\x0A\x00\x0D\x0A\x51\x55\x49\x54\x0A\x02";
 uschar *iptype;  /* To display debug info */
 struct timeval tv;
-int get_ok = 0;
 socklen_t vslen = 0;
 struct timeval tvtmp;
 
@@ -690,7 +680,9 @@ setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, (char *)&tv,
 
 do
   {
-  ret = recv(fd, &hdr, sizeof(hdr), MSG_PEEK);
+  /* The inbound host was declared to be a Proxy Protocol host, so
+     don't do a PEEK into the data, actually slurp it up. */
+  ret = recv(fd, &hdr, sizeof(hdr), 0);
   }
   while (ret == -1 && errno == EINTR);
 
@@ -715,20 +707,63 @@ if (ret >= 16 &&
     case 0x01: /* PROXY command */
       switch (hdr.v2.fam)
         {
-        case 0x11:  /* TCPv4 */
-          tmpip = string_sprintf("%s", hdr.v2.addr.ip4.src_addr);
-          if (!string_is_ip_address(tmpip,NULL))
+        case 0x11:  /* TCPv4 address type */
+          iptype = US"IPv4";
+          tmpaddr.sin_addr.s_addr = hdr.v2.addr.ip4.src_addr;
+          inet_ntop(AF_INET, &(tmpaddr.sin_addr), (char *)&tmpip, sizeof(tmpip));
+          if (!string_is_ip_address(US tmpip,NULL))
+            {
+            DEBUG(D_receive) debug_printf("Invalid %s source IP\n", iptype);
             return ERRNO_PROXYFAIL;
-          sender_host_address = tmpip;
-          sender_host_port    = hdr.v2.addr.ip4.src_port;
+            }
+          proxy_host_address  = sender_host_address;
+          sender_host_address = string_copy(US tmpip);
+          tmpport             = ntohs(hdr.v2.addr.ip4.src_port);
+          proxy_host_port     = sender_host_port;
+          sender_host_port    = tmpport;
+          /* Save dest ip/port */
+          tmpaddr.sin_addr.s_addr = hdr.v2.addr.ip4.dst_addr;
+          inet_ntop(AF_INET, &(tmpaddr.sin_addr), (char *)&tmpip, sizeof(tmpip));
+          if (!string_is_ip_address(US tmpip,NULL))
+            {
+            DEBUG(D_receive) debug_printf("Invalid %s dest port\n", iptype);
+            return ERRNO_PROXYFAIL;
+            }
+          proxy_target_address = string_copy(US tmpip);
+          tmpport              = ntohs(hdr.v2.addr.ip4.dst_port);
+          proxy_target_port    = tmpport;
           goto done;
-        case 0x21:  /* TCPv6 */
-          tmpip = string_sprintf("%s", hdr.v2.addr.ip6.src_addr);
-          if (!string_is_ip_address(tmpip,NULL))
+        case 0x21:  /* TCPv6 address type */
+          iptype = US"IPv6";
+          memmove(tmpaddr6.sin6_addr.s6_addr, hdr.v2.addr.ip6.src_addr, 16);
+          inet_ntop(AF_INET6, &(tmpaddr6.sin6_addr), (char *)&tmpip6, sizeof(tmpip6));
+          if (!string_is_ip_address(US tmpip6,NULL))
+            {
+            DEBUG(D_receive) debug_printf("Invalid %s source IP\n", iptype);
+            return ERRNO_PROXYFAIL;
+            }
+          proxy_host_address  = sender_host_address;
+          sender_host_address = string_copy(US tmpip6);
+          tmpport             = ntohs(hdr.v2.addr.ip6.src_port);
+          proxy_host_port     = sender_host_port;
+          sender_host_port    = tmpport;
+          /* Save dest ip/port */
+          memmove(tmpaddr6.sin6_addr.s6_addr, hdr.v2.addr.ip6.dst_addr, 16);
+          inet_ntop(AF_INET6, &(tmpaddr6.sin6_addr), (char *)&tmpip6, sizeof(tmpip6));
+          if (!string_is_ip_address(US tmpip6,NULL))
+            {
+            DEBUG(D_receive) debug_printf("Invalid %s dest port\n", iptype);
             return ERRNO_PROXYFAIL;
-          sender_host_address = tmpip;
-          sender_host_port    = hdr.v2.addr.ip6.src_port;
+            }
+          proxy_target_address = string_copy(US tmpip6);
+          tmpport              = ntohs(hdr.v2.addr.ip6.dst_port);
+          proxy_target_port    = tmpport;
           goto done;
+        default:
+          DEBUG(D_receive)
+            debug_printf("Unsupported PROXYv2 connection type: 0x%02x\n",
+                         hdr.v2.fam);
+          goto proxyfail;
         }
       /* Unsupported protocol, keep local connection address */
       break;
@@ -736,7 +771,9 @@ if (ret >= 16 &&
       /* Keep local connection address for LOCAL */
       break;
     default:
-      DEBUG(D_receive) debug_printf("Unsupported PROXYv2 command\n");
+      DEBUG(D_receive)
+        debug_printf("Unsupported PROXYv2 command: 0x%02x\n",
+                     hdr.v2.cmd);
       goto proxyfail;
     }
   }
@@ -816,7 +853,7 @@ else if (ret >= 8 &&
       debug_printf("Proxy dest arg is not an %s address\n", iptype);
     goto proxyfail;
     }
-  /* Should save dest ip somewhere? */
+  proxy_target_address = p;
   p = sp + 1;
   if ((sp = Ustrchr(p, ' ')) == NULL)
     {
@@ -846,29 +883,27 @@ else if (ret >= 8 &&
       debug_printf("Proxy dest port '%s' not an integer\n", p);
     goto proxyfail;
     }
-  /* Should save dest port somewhere? */
+  proxy_target_port = tmp_port;
   /* Already checked for /r /n above. Good V1 header received. */
   goto done;
   }
 else
   {
   /* Wrong protocol */
-  DEBUG(D_receive) debug_printf("Wrong proxy protocol specified\n");
+  DEBUG(D_receive) debug_printf("Invalid proxy protocol version negotiation\n");
   goto proxyfail;
   }
 
 proxyfail:
 restore_socket_timeout(fd, get_ok, tvtmp, vslen);
 /* Don't flush any potential buffer contents. Any input should cause a
-synchronization failure or we just don't want to speak SMTP to them */
+   synchronization failure */
 return FALSE;
 
 done:
 restore_socket_timeout(fd, get_ok, tvtmp, vslen);
-flush_input();
 DEBUG(D_receive)
-  debug_printf("Valid %s sender from Proxy Protocol header\n",
-               iptype);
+  debug_printf("Valid %s sender from Proxy Protocol header\n", iptype);
 return proxy_session;
 }
 #endif
diff --git a/src/util/proxy_protocol_client.pl b/src/util/proxy_protocol_client.pl
new file mode 100644
index 000000000..7cfc13ddc
--- /dev/null
+++ b/src/util/proxy_protocol_client.pl
@@ -0,0 +1,250 @@
+#!/usr/bin/perl
+#
+# Copyright (C) 2014 Todd Lyons
+# License GPLv2: GNU GPL version 2
+# <http://www.gnu.org/licenses/old-licenses/gpl-2.0.html>
+#
+# This script emulates a proxy which uses Proxy Protocol to communicate
+# to a backend server.  It should be run from an IP which is configured
+# to be a Proxy Protocol connection (or not, if you are testing error
+# scenarios) because Proxy Protocol specs require not to fall back to a
+# non-proxied mode.
+#
+# The script is interactive, so when you run it, you are expected to
+# perform whatever conversation is required for the protocol being
+# tested.  It uses STDIN/STDOUT, so you can also pipe output to/from the
+# script.  It was originally written to test Exim's Proxy Protocol
+# code, and it could be tested like this:
+#
+# swaks --pipe 'perl proxy_protocol_client.pl --server-ip
+#   host.internal.lan' --from user@example.com --to user@example.net
+#
+use strict;
+use warnings;
+use IO::Select;
+use IO::Socket;
+use Getopt::Long;
+use Data::Dumper;
+
+my %opts;
+GetOptions( \%opts,
+  'help',
+  '6|ipv6',
+  'dest-ip:s',
+  'dest-port:i',
+  'source-ip:s',
+  'source-port:i',
+  'server-ip:s',
+  'server-port:i',
+  'version:i'
+);
+&usage() if ($opts{help} || !$opts{'server-ip'});
+
+my ($dest_ip,$source_ip,$dest_port,$source_port);
+my %socket_map;
+my $status_line = "Testing Proxy Protocol Version " .
+                  ($opts{version} ? $opts{version} : '2') .
+                  ":\n";
+
+# All ip's and ports are in network byte order in version 2 mode, but are
+# simple strings when in version 1 mode.  The binary_pack_*() functions
+# return the required data for the Proxy Protocol version being used.
+
+# Use provided source or fall back to www.mrball.net
+$source_ip   = $opts{'source-ip'} ?  binary_pack_ip($opts{'source-ip'}) :
+                 $opts{6} ?
+                 binary_pack_ip("2001:470:d:367::50") :
+                 binary_pack_ip("208.89.139.252");
+$source_port = $opts{'source-port'} ?
+                 binary_pack_port($opts{'source-port'}) :
+                 binary_pack_port(43118);
+
+$status_line .= "-> " if (!$opts{version} || $opts{version} == 2);
+
+# Use provided dest or fall back to mail.exim.org
+$dest_ip   = $opts{'dest-ip'} ?  binary_pack_ip($opts{'dest-ip'}) :
+               $opts{6} ?
+               binary_pack_ip("2001:630:212:8:204:23ff:fed6:b664") :
+               binary_pack_ip("131.111.8.192");
+$dest_port = $opts{'dest-port'} ?
+               binary_pack_port($opts{'dest-port'}) :
+               binary_pack_port(25);
+
+# The IP and port of the Proxy Protocol backend real server being tested,
+# don't binary pack it.
+my $server_ip   = $opts{'server-ip'};
+my $server_port = $opts{'server-port'} ? $opts{'server-port'} : 25;
+
+my $s = IO::Select->new(); # for socket polling
+
+sub generate_preamble {
+  my @preamble;
+  if (!$opts{version} || $opts{version} == 2) {
+    @preamble = (
+      "\x0D\x0A\x0D\x0A\x00\x0D\x0A\x51\x55\x49\x54\x0A", # 12 byte v2 header
+      "\x02",                                             # declares v2
+      "\x01",                                             # connection is proxied
+      $opts{6} ? "\x21" : "\x11",                         # inet6/4 and TCP (stream)
+      $opts{6} ? "\x24" : "\x0b",                         # 36 bytes / 12 bytes
+      $source_ip,
+      $dest_ip,
+      $source_port,
+      $dest_port
+    );
+  }
+  else {
+    @preamble = (
+      "PROXY", " ",                                       # Request proxy mode
+      $opts{6} ? "TCP6" : "TCP4", " ",                    # inet6/4 and TCP (stream)
+      $source_ip, " ",                                    
+      $dest_ip, " ",
+      $source_port, " ",
+      $dest_port,
+      "\x0d\x0a"
+    );
+    $status_line .= join "", @preamble;
+  }
+  print "\n", $status_line, "\n";
+  print "\n" if (!$opts{version} || $opts{version} == 2);
+  return @preamble;
+}
+
+sub binary_pack_port {
+  my $port = shift();
+  if ($opts{version} && $opts{version} == 1) {
+    return $port
+      if ($port && $port =~ /^\d+$/ && $port > 0 && $port < 65536);
+    die "Not a valid port: $port";
+  }
+  $status_line .= $port." ";
+  $port = pack "S", $port;
+  return $port;
+}
+
+sub binary_pack_ip {
+  my $ip = shift();
+  if ( $ip =~ m/\./ && !$opts{6}) {
+    if (IP4_valid($ip)) {
+      return $ip if ($opts{version} && $opts{version} == 1);
+      $status_line .= $ip.":";
+      $ip = pack "C*", split /\./, $ip;
+    }
+    else { die "Invalid IPv4: $ip"; }
+  }
+  elsif ($ip =~ m/:/ && $opts{6}) {
+    $ip = pad_ipv6($ip);
+    if (IP6_valid($ip)) {
+      return $ip if ($opts{version} && $opts{version} == 1);
+      $status_line .= $ip.":";
+      $ip = pack "S>*", map hex, split /:/, $ip;
+    }
+    else { die "Invalid IPv6: $ip"; }
+  }
+  else { die "Mismatching IP families passed: $ip"; }
+  return $ip;
+}
+
+sub pad_ipv6 {
+  my $ip = shift();
+  my @ip = split /:/, $ip;
+  my $segments = scalar @ip;
+  return $ip if ($segments == 8);
+  $ip = "";
+  for (my $count=1; $count <= $segments; $count++) {
+    my $block = $ip[$count-1];
+    if ($block) {
+      $ip .= $block;
+      $ip .= ":" unless $count == $segments;
+    }
+    elsif ($count == 1) {
+      # Somebody passed us ::1, fix it, but it's not really valid
+      $ip = "0:";
+    }
+    else {
+      $ip .= join ":", map "0", 0..(8-$segments);
+      $ip .= ":";
+    }
+  }
+  return $ip;
+}
+
+sub IP6_valid {
+  my $ip = shift;
+  $ip = lc($ip);
+  return 0 unless ($ip =~ /^[0-9a-f:]+$/);
+  my @ip = split /:/, $ip;
+  return 0 if (scalar @ip != 8);
+  return 1;
+}
+
+sub IP4_valid {
+  my $ip = shift;
+  $ip =~ /^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$/;
+  foreach ($1,$2,$3,$4){
+    if ($_  <256 && $_ >0) {next;}
+    return 0;
+  }
+  return 1;
+}
+
+sub go_interactive {
+  my $continue = 1;
+  while($continue) {
+    # Check for input on both ends, recheck every 5 sec
+    for my $socket ($s->can_read(5)) {
+      my $remote = $socket_map{$socket};
+      my $buffer;
+      my $read = $socket->sysread($buffer, 4096);
+      if ($read) {
+        $remote->syswrite($buffer);
+      }
+      else {
+        $continue = 0;
+      }
+    }
+  }
+}
+
+sub connect_stdin_to_proxy {
+  my $sock = new IO::Socket::INET(
+               PeerAddr => $server_ip,
+               PeerPort => $server_port,
+               Proto    => 'tcp'
+             );
+
+  die "Could not create socket: $!\n" unless $sock;
+  # Add sockets to the Select group
+  $s->add(\*STDIN);
+  $s->add($sock);
+  # Tie the sockets together using this hash
+  $socket_map{\*STDIN} = $sock;
+  $socket_map{$sock} = \*STDOUT;
+  return $sock;
+}
+
+sub usage {
+  chomp(my $prog = `basename $0`);
+  print <<EOF;
+Usage: $prog [required] [optional]
+  Required:
+    --server-ip   IP of server to test proxy configuration,
+                  a hostname is ok, but for only this setting
+  Optional:
+    --server-port Port server is listening on (default 25)
+    --6           IPv6 source/dest (default IPv4), if none specified,
+                  some default, reverse resolvable IP's are used for
+                  the source and dest ip/port
+    --dest-ip     Public IP of the proxy server
+    --dest-port   Port of public IP of proxy server
+    --source-ip   IP connecting to the proxy server
+    --source-port Port of IP connecting to the proxy server
+    --help        This output
+EOF
+  exit;
+}
+
+
+my $sock = connect_stdin_to_proxy();
+my @preamble = generate_preamble();
+print $sock @preamble;
+go_interactive();