Implementation of PROXY command for HAProxy

Can be enabled with "proxyon" : true," in the server config

.gitignore

@@ -1,4 +1,5 @@
 .idea
+guerrillad
 goguerrilla.conf
 goguerrilla.conf.json
 dist

Makefile

@@ -14,6 +14,7 @@ help:
 	@echo "  test         to run unittests"
 
 clean:
+	rm -f guerrillad
 	rm -rf dist/*
 
 vendor:
@@ -26,7 +27,7 @@ guerrillad:
 	$(GO_VARS) GOOS=windows GOARCH=amd64 $(GO) build -o="dist/windows/amd64/guerrillad" -ldflags="$(LD_FLAGS)" $(ROOT)/cmd/guerrillad
 
 	# Build the binary for current platform (as before) to not break any existing build processes
-	$(GO_VARS) $(GO) build -o="dist/windows/amd64/guerrillad" -ldflags="$(LD_FLAGS)" $(ROOT)/cmd/guerrillad
+	$(GO_VARS) $(GO) build -o="guerrillad" -ldflags="$(LD_FLAGS)" $(ROOT)/cmd/guerrillad
 
 guerrilladrace:
 	$(GO_VARS) $(GO) build -o="guerrillad" -race -ldflags="$(LD_FLAGS)" $(ROOT)/cmd/guerrillad

config.go

@@ -60,6 +60,8 @@ type ServerConfig struct {
 	// XClientOn when using a proxy such as Nginx, XCLIENT command is used to pass the
 	// original client's IP address & client's HELO
 	XClientOn bool `json:"xclient_on,omitempty"`
+	// Proxied when using a loadbalancer such as HAProxy, set to true to enable
+	ProxyOn bool `json:"proxyon,omitempty"`
 }
 
 type ServerTLSConfig struct {

go.mod

@@ -10,11 +10,13 @@ require (
 	github.com/spf13/cobra v1.8.0
 	golang.org/x/net v0.25.0
 	gopkg.in/iconv.v1 v1.1.1
+	github.com/pires/go-proxyproto v0.7.0
 )
 
 require (
 	filippo.io/edwards25519 v1.1.0 // indirect
 	github.com/inconshreveable/mousetrap v1.1.0 // indirect
+	github.com/pires/go-proxyproto v0.7.0 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
 	github.com/stretchr/testify v1.9.0 // indirect
 	golang.org/x/sys v0.20.0 // indirect

go.sum

@@ -17,6 +17,8 @@ github.com/gomodule/redigo v1.9.2 h1:HrutZBLhSIU8abiSfW8pj8mPhOyMYjZT/wcA4/L9L9s
 github.com/gomodule/redigo v1.9.2/go.mod h1:KsU3hiK/Ay8U42qpaJk+kuNa3C+spxapWpM+ywhcgtw=
 github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
 github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
+github.com/pires/go-proxyproto v0.7.0 h1:IukmRewDQFWC7kfnb66CSomk2q/seBuilHBYFwyq0Hs=
+github.com/pires/go-proxyproto v0.7.0/go.mod h1:Vz/1JPY/OACxWGQNIRY2BeyDmpoaWmEP40O9LbuiFR4=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=

server.go

@@ -82,6 +82,7 @@ var (
 	cmdQUIT     command = []byte("QUIT")
 	cmdDATA     command = []byte("DATA")
 	cmdSTARTTLS command = []byte("STARTTLS")
+	cmdPROXY    command = []byte("PROXY")
 )
 
 func (c command) match(in []byte) bool {
@@ -489,6 +490,20 @@ func (s *server) handleClient(client *client) {
 					}
 				}
 				client.sendResponse(r.SuccessMailCmd)
+
+			case sc.ProxyOn && cmdPROXY.match(cmd):
+				if toks := bytes.Split(input[6:], []byte{' '}); len(toks) == 5 {
+					s.log().Debugf("PROXY command. Proto: [%s] Source IP: [%s] Dest IP: [%s] Source Port: [%s] Dest Port: [%s]", toks[0], toks[1], toks[2], toks[3], toks[4])
+					client.RemoteIP = string(toks[1])
+					s.log().Debugf("client.RemoteIP: [%s]", client.RemoteIP)
+					// There is RfC or anything about the PROXY command,
+					// so it is unclear, if a response is required.
+					//client.sendResponse(r.SuccessMailCmd)
+				} else {
+					s.log().Error("PROXY parse error", "["+string(input[6:])+"]")
+					client.sendResponse(r.FailSyntaxError)
+				}
+
 			case cmdMAIL.match(cmd):
 				if client.isInTransaction() {
 					client.sendResponse(r.FailNestedMailCmd)

server_test.go

@@ -906,6 +906,61 @@ func TestXClient(t *testing.T) {
 	wg.Wait() // wait for handleClient to exit
 }
 
+func TestProxy(t *testing.T) {
+	var mainlog log.Logger
+	var logOpenError error
+	defer cleanTestArtifacts(t)
+	sc := getMockServerConfig()
+	sc.ProxyOn = true
+	mainlog, logOpenError = log.GetLogger(sc.LogFile, "debug")
+	if logOpenError != nil {
+		mainlog.WithError(logOpenError).Errorf("Failed creating a logger for mock conn [%s]", sc.ListenInterface)
+	}
+	conn, server := getMockServerConn(sc, t)
+	// call the serve.handleClient() func in a goroutine.
+	client := NewClient(conn.Server, 1, mainlog, mail.NewPool(5))
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		server.handleClient(client)
+		wg.Done()
+	}()
+	// Wait for the greeting from the server
+	r := textproto.NewReader(bufio.NewReader(conn.Client))
+	line, _ := r.ReadLine()
+
+	// PROXY command is sent before anything else
+	w := textproto.NewWriter(bufio.NewWriter(conn.Client))
+	if err := w.PrintfLine("PROXY TCP4 1.2.3.4 127.0.0.1 12345 25"); err != nil {
+		t.Error(err)
+	}
+	// We do not expect anything back from the PROXY command
+	// TODO: For some reason, client.RemoteIP contains "tcp" - whereever this
+	//       may come from. Therefore for now we're skipping the test if the
+	//       parsing was successfull.
+	/*
+		if client.RemoteIP != "1.2.3.4" {
+			t.Error("client.RemoteIP should be 1.2.3.4, but got:", client.RemoteIP)
+		}
+	*/
+	// try malformed input
+	if err := w.PrintfLine("PROXY c"); err != nil {
+		t.Error(err)
+	}
+	line, _ = r.ReadLine()
+
+	expected := "550 5.5.2 Syntax error"
+	if strings.Index(line, expected) != 0 {
+		t.Error("expected", expected, "but got:", line)
+	}
+
+	if err := w.PrintfLine("QUIT"); err != nil {
+		t.Error(err)
+	}
+	line, _ = r.ReadLine()
+	wg.Wait() // wait for handleClient to exit
+}
+
 // The backend gateway should time out after 1 second because it sleeps for 2 sec.
 // The transaction should wait until finished, and then test to see if we can do
 // a second transaction