added pop3 STARTTLS queryResponse (#84)

* added pop3 STARTTLS queryResponse

* implemented pop3 test, added pop3 starttls parameter to README

Co-authored-by: Timo Boldt <tb@teuto.net>

README.md

@@ -311,7 +311,7 @@ target: <string>
 ### <tcp_probe>
 
 ```
-# Use the STARTTLS command before starting TLS for those protocols that support it (smtp, ftp, imap, postgres)
+# Use the STARTTLS command before starting TLS for those protocols that support it (smtp, ftp, imap, pop3, postgres)
 [ starttls: <string> ]
 ```
 

prober/tcp.go

@@ -119,6 +119,17 @@ var (
 				expectBytes: []byte{0x53},
 			},
 		},
+		"pop3": []queryResponse{
+			queryResponse{
+				expect: "OK",
+			},
+			queryResponse{
+				send: "STLS",
+			},
+			queryResponse{
+				expect: "OK",
+			},
+		},
 	}
 )
 

prober/tcp_test.go

@@ -324,6 +324,45 @@ func TestProbeTCPStartTLSIMAP(t *testing.T) {
 	checkTLSVersionMetrics("TLS 1.3", registry, t)
 }
 
+// TestProbeTCPStartTLSPOP3 tests STARTTLS against a mock POP3 server
+func TestProbeTCPStartTLSPOP3(t *testing.T) {
+	server, certPEM, _, caFile, teardown, err := test.SetupTCPServer()
+	if err != nil {
+		t.Fatalf(err.Error())
+	}
+	defer teardown()
+
+	server.StartPOP3()
+	defer server.Close()
+
+	module := config.Module{
+		TCP: config.TCPProbe{
+			StartTLS: "pop3",
+		},
+		TLSConfig: config.TLSConfig{
+			CAFile:             caFile,
+			InsecureSkipVerify: false,
+		},
+	}
+
+	registry := prometheus.NewRegistry()
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	if err := ProbeTCP(ctx, newTestLogger(), server.Listener.Addr().String(), module, registry); err != nil {
+		t.Fatalf("error: %s", err)
+	}
+
+	cert, err := newCertificate(certPEM)
+	if err != nil {
+		t.Fatal(err)
+	}
+	checkCertificateMetrics(cert, registry, t)
+	checkOCSPMetrics([]byte{}, registry, t)
+	checkTLSVersionMetrics("TLS 1.3", registry, t)
+}
+
 // TestProbeTCPStartTLSPostgreSQL tests STARTTLS against a mock PostgreSQL server
 func TestProbeTCPStartTLSPostgreSQL(t *testing.T) {
 	server, certPEM, _, caFile, teardown, err := test.SetupTCPServer()

test/tcp.go

@@ -164,6 +164,33 @@ func (t *TCPServer) StartIMAP() {
 	}()
 }
 
+// StartPOP3 starts a listener that negotiates a TLS connection with an pop3
+// client using STARTTLS
+func (t *TCPServer) StartPOP3() {
+	go func() {
+		conn, err := t.Listener.Accept()
+		if err != nil {
+			panic(fmt.Sprintf("Error accepting on socket: %s", err))
+		}
+		defer conn.Close()
+
+		fmt.Fprintf(conn, "+OK XPOP3 ready.\n")
+		if _, e := fmt.Fscanf(conn, "STLS\n"); e != nil {
+			panic("Error in dialog. No STLS received.")
+		}
+		fmt.Fprintf(conn, "+OK Begin TLS negotiation now.\n")
+
+		// Upgrade to TLS.
+		tlsConn := tls.Server(conn, t.TLS)
+		if err := tlsConn.Handshake(); err != nil {
+			level.Error(t.logger).Log("msg", err)
+		}
+		defer tlsConn.Close()
+
+		t.stopCh <- struct{}{}
+	}()
+}
+
 // StartPostgreSQL starts a listener that negotiates a TLS connection with an postgresql
 // client using STARTTLS
 func (t *TCPServer) StartPostgreSQL() {