raise RuntimeError on incomplete or extra data

lib/msf/core/exploit/remote/smtp_deliver.rb

@@ -249,7 +249,8 @@ module Exploit::Remote::SMTPDeliver
       while !(res =~ /(^|\r\n)\d{3}( .*|)\r\n$/) && chunk = nsock.get_once
         res += chunk
       end
-    rescue
+      raise RuntimeError.new("SMTP response is incomplete or contains extra data") unless res =~ /(^|\r\n)\d{3}( .*|)\r\n$/
+    rescue EOFError
       return nil
     end
     # Don't truncate the server output because it might be helpful for

spec/lib/msf/core/exploit/remote/smtp_delivery_spec.rb

@@ -38,6 +38,22 @@ RSpec.describe Msf::Exploit::Remote::SMTPDeliver do
       expect(response).to end_with(ehlo_resp3 + ehlo_resp4)
     end
 
+    context "when a single response occurs" do
+      let(:ehlo_resp1) {
+        "250 DSN\r\n"
+      }
+
+      before {
+        allow(socket).to receive(:get_once).and_return(ehlo_resp1)
+      }
+
+
+      it "passes" do
+        response = instance.smtp_send_recv(cmd, socket)
+        expect(response).to end_with(ehlo_resp1)
+      end
+    end
+
     context "when the server response is terse" do
       let(:ehlo_resp3) {
         "250"
@@ -49,15 +65,28 @@ RSpec.describe Msf::Exploit::Remote::SMTPDeliver do
       end
     end
 
-    context "when invalid response are received" do
+    context "when incomplete response is received" do
       # a nil from `get_once` simulates a Timeout expired
       let(:ehlo_resp4){
         nil
       }
 
-      it "should return the incomplete response when no data is left to read" do
-        response = instance.smtp_send_recv(cmd, socket)
-        expect(response).to end_with(ehlo_resp3)
+      it "should raise error when the response is incomplete" do
+        expect {instance.smtp_send_recv(cmd, socket)}.to raise_error RuntimeError
+      end
+    end
+
+    context "when excess data response is received" do
+      # a nil from `get_once` simulates a Timeout expired
+      let(:ehlo_resp3){
+        "250 DSN\r\n253 additional unexpected data"
+      }
+      let(:ehlo_resp4){
+        nil
+      }
+
+      it "should raise error when the response is incomplete" do
+        expect {instance.smtp_send_recv(cmd, socket)}.to raise_error RuntimeError
       end
     end
   end