Propagate the OS assigned port value (fixes LocalPort 0)

lib/rex/socket/comm/local.rb

@@ -273,10 +273,11 @@ def self.create_by_type(param, type, proto = 0)
         end
 
         sock.bind(Rex::Socket.to_sockaddr(ip, param.localport))
-
       rescue ::Errno::EADDRNOTAVAIL,::Errno::EADDRINUSE
         sock.close
         raise Rex::BindFailed.new(param.localhost, param.localport), caller
+      else
+        param.localport = sock.local_address.ip_port
       end
     end
 

lib/rex/socket/proxies.rb

@@ -1,4 +1,5 @@
 # -*- coding: binary -*-
+require 'uri'
 
 module Rex
   module Socket

spec/rex/socket/comm/local_spec.rb

@@ -7,13 +7,15 @@
     let(:proto) { ::Socket::IPPROTO_TCP }
     let(:params) { Rex::Socket::Parameters.new({ 'PeerHost' => '192.0.2.1', 'PeerPort' => 1234 }) }
     let(:sock) { RSpec::Mocks::Double.new('socket') }
+    let(:local_address) { RSpec::Mocks::Double.new('local address', ip_port: 49152) }
 
     before(:each) do
       allow(Rex::Socket).to receive(:support_ipv6?).with(no_args).and_return(true)
       allow(::Socket).to receive(:new).with(any_args).and_return(sock)
       allow(sock).to receive(:setsockopt).with(any_args)
       allow(sock).to receive(:bind).with(any_args)
       allow(sock).to receive(:connect).with(any_args).and_return(nil)
+      allow(sock).to receive(:local_address).with(no_args).and_return(local_address)
     end
 
     it 'creates an IPv4 socket' do
@@ -108,6 +110,43 @@
     end
   end
 
+  describe 'LocalPort 0 assignment' do
+    context 'when creating a TCP server bound to port 0' do
+      it 'updates localport to the OS-assigned port' do
+        params = Rex::Socket::Parameters.new(
+          'Proto'     => 'tcp',
+          'Server'    => true,
+          'LocalHost' => '127.0.0.1',
+          'LocalPort' => 0
+        )
+        sock = described_class.create(params)
+        begin
+          expect(sock.localport).to be > 0
+          expect(sock.localport).to eq(sock.local_address.ip_port)
+        ensure
+          sock.close
+        end
+      end
+    end
+
+    context 'when creating a UDP socket bound to port 0' do
+      it 'updates localport to the OS-assigned port' do
+        params = Rex::Socket::Parameters.new(
+          'Proto'     => 'udp',
+          'LocalHost' => '127.0.0.1',
+          'LocalPort' => 0
+        )
+        sock = described_class.create(params)
+        begin
+          expect(sock.localport).to be > 0
+          expect(sock.localport).to eq(sock.local_address.ip_port)
+        ensure
+          sock.close
+        end
+      end
+    end
+  end
+
   describe 'Interface option' do
     context 'when Interface is set and a proxy is also configured' do
       it 'raises Rex::BindFailed before creating a socket' do