Add specs for the new method

lib/msf/base/sessions/meterpreter.rb

@@ -323,9 +323,9 @@ class Meterpreter < Rex::Post::Meterpreter::Client
         nhost = find_internet_connected_address
 
         original_session_host = self.session_host
-        # If we found a better IP address for this session, change it up
-        # only handle cases where the DB is not connected here
-        if !(framework.db && framework.db.active)
+        # If we found a better IP address for this session, change it
+        # up.  Only handle cases where the DB is not connected here
+        if nhost && !(framework.db && framework.db.active)
           self.session_host = nhost
         end
 
@@ -461,6 +461,8 @@ protected
   # @see Rex::Post::Meterpreter::Extensions::Stdapi::Net::Config#get_routes
   # @return [String] The address from which this host reaches the
   #   internet, as ASCII. e.g.: "192.168.100.156"
+  # @return [nil] If there is an interface with an address that matches
+  #   {#session_host}
   def find_internet_connected_address
 
     ifaces = self.net.config.get_interfaces().flatten rescue []
@@ -497,7 +499,9 @@ protected
       end
 
       if !nhost
-        # Find the first non-loopback address
+        # No internal address matches what we see externally and no
+        # interface has a default route. Fall back to the first
+        # non-loopback address
         non_loopback = ifaces.find { |i| i.ip != "127.0.0.1" && i.ip != "::1" }
         if non_loopback
           nhost = non_loopback.ip

spec/lib/msf/base/sessions/meterpreter_spec.rb

@@ -0,0 +1,154 @@
+require 'spec_helper'
+require 'msf/base/sessions/meterpreter'
+require 'rex/post/meterpreter/extensions/stdapi/net/interface'
+require 'rex/post/meterpreter/extensions/stdapi/net/route'
+
+describe Msf::Sessions::Meterpreter do
+  subject(:meterpreter) { described_class.new(StringIO.new(""), skip_ssl: true) }
+
+  let(:v6_gateway) { "2607:f8b0:4004:0802::1014" }
+  let(:v4_gateway) { "192.168.3.1" }
+
+  let(:v6_linklocal) { "fe80::d6c9:efff:fe53:53ff" }
+
+  let(:routes) do
+    [
+      Rex::Post::Meterpreter::Extensions::Stdapi::Net::Route.new(
+        IPAddr.new("0.0.0.0").hton, # Subnet
+        IPAddr.new("0.0.0.0").hton, # Netmask
+        IPAddr.new("192.168.3.1").hton  # Gateway
+      ),
+      Rex::Post::Meterpreter::Extensions::Stdapi::Net::Route.new(
+        IPAddr.new("::").hton, # Subnet
+        IPAddr.new("::").hton, # Netmask
+        IPAddr.new(v6_gateway).hton  # Gateway
+      )
+    ]
+  end
+
+  it { should respond_to(:find_internet_connected_address) }
+
+  describe "#find_internet_connected_address" do
+
+    subject(:connected_address) do
+      m = described_class.new(StringIO.new(""), skip_ssl: true)
+      m.stub_chain(:net, :config, :get_interfaces).and_return(interfaces)
+      m.stub_chain(:net, :config, :get_routes).and_return(routes)
+      m.session_host = session_host
+
+      m.send(:find_internet_connected_address)
+    end
+
+    let(:interfaces) do
+      ifaces = []
+      interface_config.each_with_index { |iface_hash, idx|
+        ifaces << Rex::Post::Meterpreter::Extensions::Stdapi::Net::Interface.new(
+          index: idx,
+          mac_addr: "00:11:22:33:44:%02x"%idx,
+          mac_name: "eth0",
+          mtu: 1500,
+          flags: 0,
+          addrs: iface_hash[:ips],
+          netmasks: iface_hash[:masks],
+          scopes: [ "" ]
+        )
+      }
+
+      ifaces
+    end
+
+    let(:session_host) { "99.99.99.99" }
+
+    context "with an address that matches #session_host" do
+      let(:interface_config) do
+        [
+          { ips: [ "192.168.10.1" ], masks: [ "255.255.255.0" ], },
+          { ips: [ "192.168.11.1" ], masks: [ "255.255.255.0" ], },
+          { ips: [ "192.168.12.1" ], masks: [ "255.255.255.0" ], },
+          { ips: [ session_host   ], masks: [ "255.255.255.0" ], },
+          { ips: [ "192.168.14.1" ], masks: [ "255.255.255.0" ], },
+          { ips: [ "192.168.16.1" ], masks: [ "255.255.255.0" ], },
+        ]
+      end
+      it "returns nil" do
+        expect(connected_address).to be_nil
+      end
+    end
+
+    # All the rest of these assume session_host does not match any
+    # interface's addresses
+
+    context "one interface with one IPv4 address" do
+      let(:interface_config) do
+        [ { ips: [ "10.2.3.4" ], masks: [ "255.255.255.0" ], } ]
+      end
+      it "returns that address" do
+        expect(connected_address).to eq("10.2.3.4")
+      end
+    end
+
+    context "one interface with one IPv6 address" do
+      let(:interface_config) do
+        [
+          { ips: [ v6_linklocal ], masks: [ "ffff:ffff:ffff:ffff::" ], },
+        ]
+      end
+      it "returns that address" do
+        expect(connected_address).to eq(v6_linklocal)
+      end
+    end
+
+    context "one interface with mixed IP versions" do
+      context "first is correct" do
+        let(:interface_config) do
+          [
+            { ips: [ "192.168.3.4" ], masks: [ "255.255.255.0" ], },
+            { ips: [ v6_linklocal ], masks: [ "ffff:ffff:ffff:ffff::" ], },
+          ]
+        end
+        it "returns first address" do
+          expect(connected_address).to eq("192.168.3.4")
+        end
+      end
+      context "second address is correct" do
+        let(:interface_config) do
+          [
+            { ips: [ v6_linklocal ], masks: [ "ffff:ffff:ffff:ffff::" ], },
+            { ips: [ "192.168.3.4" ], masks: [ "255.255.255.0" ], },
+          ]
+        end
+        it "returns second address" do
+          expect(connected_address).to eq("192.168.3.4")
+        end
+      end
+    end
+
+    context "one interface with multiple IPv4 addresses" do
+      context "first address is correct" do
+        let(:interface_config) do
+          [ {
+            ips: ["192.168.3.4", "10.2.3.4"],
+            masks: [ "255.255.255.0", "255.0.0.0"],
+          } ]
+        end
+        it "returns first address" do
+          expect(connected_address).to eq("192.168.3.4")
+        end
+      end
+      context "second address is correct" do
+        let(:interface_config) do
+          [ {
+            ips: [ "10.2.3.4", "192.168.3.4" ],
+            masks: [ "255.0.0.0", "255.255.255.0" ],
+          } ]
+        end
+        it "returns second address" do
+          expect(connected_address).to eq("192.168.3.4")
+        end
+      end
+    end
+
+  end
+
+end
+