Refactor and expand client dial-and-send tests

Renamed TestClient_DialAndSend to TestClient_DialAndSendWithContext and reorganized message setup. Added multiple test cases to cover different failure points in the DialAndSendWithContext method.

.github/workflows/codeql-analysis.yml

@@ -54,7 +54,7 @@ jobs:
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL
-      uses: github/codeql-action/init@f779452ac5af1c261dce0346a8f964149f49322b # v3.26.13
+      uses: github/codeql-action/init@662472033e021d55d94146f66f6058822b0b39fd # v3.27.0
       with:
         languages: ${{ matrix.language }}
         # If you wish to specify custom queries, you can do so here or in a config file.
@@ -65,7 +65,7 @@ jobs:
     # Autobuild attempts to build any compiled languages  (C/C++, C#, or Java).
     # If this step fails, then you should remove it and run the build manually (see below)
     - name: Autobuild
-      uses: github/codeql-action/autobuild@f779452ac5af1c261dce0346a8f964149f49322b # v3.26.13
+      uses: github/codeql-action/autobuild@662472033e021d55d94146f66f6058822b0b39fd # v3.27.0
 
     # ℹ️ Command-line programs to run using the OS shell.
     # 📚 https://git.io/JvXDl
@@ -79,4 +79,4 @@ jobs:
     #   make release
 
     - name: Perform CodeQL Analysis
-      uses: github/codeql-action/analyze@f779452ac5af1c261dce0346a8f964149f49322b # v3.26.13
+      uses: github/codeql-action/analyze@662472033e021d55d94146f66f6058822b0b39fd # v3.27.0

.github/workflows/scorecards.yml

@@ -75,6 +75,6 @@ jobs:
 
       # Upload the results to GitHub's code scanning dashboard.
       - name: "Upload to code-scanning"
-        uses: github/codeql-action/upload-sarif@f779452ac5af1c261dce0346a8f964149f49322b # v3.26.13
+        uses: github/codeql-action/upload-sarif@662472033e021d55d94146f66f6058822b0b39fd # v3.27.0
         with:
           sarif_file: results.sarif

b64linebreaker_test.go

@@ -21,7 +21,7 @@ var (
 
 func TestBase64LineBreaker(t *testing.T) {
 	t.Run("write, copy and close", func(t *testing.T) {
-		logoWriter := &bytes.Buffer{}
+		logoWriter := bytes.NewBuffer(nil)
 		lineBreaker := &Base64LineBreaker{out: logoWriter}
 		t.Cleanup(func() {
 			if err := lineBreaker.Close(); err != nil {
@@ -43,7 +43,7 @@ func TestBase64LineBreaker(t *testing.T) {
 			}
 		})
 
-		logoWriter := &bytes.Buffer{}
+		logoWriter := bytes.NewBuffer(nil)
 		lineBreaker := &Base64LineBreaker{out: logoWriter}
 		t.Cleanup(func() {
 			if err := lineBreaker.Close(); err != nil {
@@ -237,9 +237,9 @@ func FuzzBase64LineBreaker(f *testing.F) {
 	}
 
 	f.Fuzz(func(t *testing.T, data []byte) {
-		var buffer bytes.Buffer
+		buffer := bytes.NewBuffer(nil)
 		lineBreaker := &Base64LineBreaker{
-			out: &buffer,
+			out: buffer,
 		}
 		base64Encoder := base64.NewEncoder(base64.StdEncoding, lineBreaker)
 

smtp/smtp.go

@@ -554,8 +554,19 @@ func (c *Client) Noop() error {
 
 // Quit sends the QUIT command and closes the connection to the server.
 func (c *Client) Quit() error {
-	if err := c.hello(); err != nil {
-		return err
+	// If we already tried to send a EHLO/HELO but it failed, we still need to be able to send
+	// a QUIT to close the connection.
+	// c.hello() will return the global helloErr of the Client, which will always be set if the HELO
+	// failed before. Therefore if we already sent a HELO and the error is not nil, we skip another
+	// EHLO/HELO try
+	c.mutex.RLock()
+	didHello := c.didHello
+	helloErr := c.helloError
+	c.mutex.RUnlock()
+	if !didHello || helloErr == nil {
+		if err := c.hello(); err != nil {
+			return err
+		}
 	}
 	_, _, err := c.cmd(221, "QUIT")
 	if err != nil {