Fix some lint and vet issues

README.md

@@ -36,23 +36,23 @@ logs:
 3. **Generate private keys:**
 ```bash
 mkdir -p /etc/tesseract/keys
-./tesseract-genconf -c config.yaml gen-key
+./tesseract-genconf -c config.yaml --write gen-key
 ```
 
 4. **Create directories and generate environment files:**
 ```bash
 mkdir -p /var/lib/tesseract/example2025h1/data
-./tesseract-genconf -c config.yaml gen-env
+./tesseract-genconf -c config.yaml --write gen-env
 ```
 
 5. **Generate HTML and JSON files:**
 ```bash
-./tesseract-genconf -c config.yaml gen-html
+./tesseract-genconf -c config.yaml --write gen-html
 ```
 
 6. **Generate nginx configuration files:**
 ```bash
-./tesseract-genconf -c config.yaml gen-nginx
+./tesseract-genconf -c config.yaml --write gen-nginx
 ```
 
 The port from the main `listen:` field will be used in the NGINX server blocks (in our case
@@ -66,3 +66,25 @@ The port from the main `listen:` field will be used in the NGINX server blocks (
 # For production environment, take the ccadb 'production' roots
 ./tesseract-genconf gen-roots --source https://gouda2027h2.log.ct.ipng.ch/ --output roots-production.pem
 ```
+
+### Safe File Operations with `--diff` and `--write`
+
+The `tesseract-genconf` tool includes safety features to prevent accidental file modifications:
+
+- **`--diff`**: Shows colored unified diffs of what would change without writing files
+- **`--write`**: Required flag to actually write files to disk
+- **`--no-color`**: Disables colored diff output (useful for redirecting to files)
+
+**Recommended workflow:**
+```bash
+# 1. First, preview changes with --diff
+./tesseract-genconf -c config.yaml --diff gen-html
+
+# 2. Review the colored diff output, then apply changes
+./tesseract-genconf -c config.yaml --write gen-html
+
+# 3. Or combine both to see diffs and write files
+./tesseract-genconf -c config.yaml --diff --write gen-html
+```
+
+**Note:** Flags must come before the command name (e.g., `--diff gen-html`, not `gen-html --diff`).

go.mod

@@ -3,3 +3,8 @@ module cheese
 go 1.24.4
 
 require gopkg.in/yaml.v3 v3.0.1
+
+require (
+	github.com/hexops/gotextdiff v1.0.3 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+)

go.sum

@@ -1,3 +1,7 @@
+github.com/hexops/gotextdiff v1.0.3 h1:gitA9+qJrrTCsiCl7+kh75nPqQt1cx4ZkudSTLoUqJM=
+github.com/hexops/gotextdiff v1.0.3/go.mod h1:pSWU5MAI3yDq+fZBTazCSJysOMbxWL1BSow5/V2vxeg=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

tesseract/genconf/env.go

@@ -8,7 +8,7 @@ import (
 	"strings"
 )
 
-func generateEnv(yamlFile string) {
+func generateEnv(yamlFile string, wantDiff bool, allowWrite bool, useColor bool) {
 	config := loadConfig(yamlFile)
 
 	// Check that all local directories exist
@@ -24,7 +24,7 @@ func generateEnv(yamlFile string) {
 
 		// Create combined roots.pem file
 		rootsPemPath := filepath.Join(logEntry.LocalDirectory, "roots.pem")
-		err := createCombinedRootsPemWithStatus(config.Roots, logEntry.ExtraRoots, rootsPemPath)
+		err := createCombinedRootsPemWithStatus(config.Roots, logEntry.ExtraRoots, rootsPemPath, wantDiff, allowWrite, useColor)
 		if err != nil {
 			log.Fatalf("Failed to create %s: %v", rootsPemPath, err)
 		}
@@ -32,7 +32,7 @@ func generateEnv(yamlFile string) {
 		// Build TESSERACT_ARGS string
 		args := []string{
 			fmt.Sprintf("--private_key=%s", logEntry.Secret),
-			fmt.Sprintf("--origin=%s.log.ct.ipng.ch", logEntry.ShortName),
+			fmt.Sprintf("--origin=%s", logEntry.Origin),
 			fmt.Sprintf("--storage_dir=%s", logEntry.LocalDirectory),
 			fmt.Sprintf("--roots_pem_file=%s", rootsPemPath),
 		}
@@ -53,14 +53,14 @@ func generateEnv(yamlFile string) {
 		tesseractArgs := strings.Join(args, " ")
 		envContent := fmt.Sprintf("TESSERACT_ARGS=\"%s\"\nOTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4318\n", tesseractArgs)
 
-		err = writeFileWithStatus(envPath, []byte(envContent))
+		err = writeFileWithStatus(envPath, []byte(envContent), wantDiff, allowWrite, useColor)
 		if err != nil {
 			log.Fatalf("Failed to write %s: %v", envPath, err)
 		}
 	}
 }
 
-func createCombinedRootsPemWithStatus(rootsFile, extraRootsFile, outputPath string) error {
+func createCombinedRootsPemWithStatus(rootsFile, extraRootsFile, outputPath string, wantDiff bool, allowWrite bool, useColor bool) error {
 	// Read main roots file
 	var combinedContent []byte
 	if rootsFile != "" {
@@ -80,5 +80,5 @@ func createCombinedRootsPemWithStatus(rootsFile, extraRootsFile, outputPath stri
 		combinedContent = append(combinedContent, extraRootsData...)
 	}
 
-	return writeFileWithStatus(outputPath, combinedContent)
+	return writeFileWithStatus(outputPath, combinedContent, wantDiff, allowWrite, useColor)
 }

tesseract/genconf/env_test.go

@@ -0,0 +1,219 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestGenerateEnv(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	// Create test directories
+	testLogDir := filepath.Join(tmpDir, "test-log")
+	testLog2Dir := filepath.Join(tmpDir, "test-log-2")
+	err := os.MkdirAll(testLogDir, 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = os.MkdirAll(testLog2Dir, 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Create test roots files
+	rootsFile := filepath.Join(tmpDir, "roots.pem")
+	extraRootsFile := filepath.Join(tmpDir, "extra-roots.pem")
+
+	rootsContent := `-----BEGIN CERTIFICATE-----
+MIIBkTCB+wIJAKZJ...
+-----END CERTIFICATE-----`
+
+	extraRootsContent := `-----BEGIN CERTIFICATE-----
+MIIBkTCB+wIJAKZK...
+-----END CERTIFICATE-----`
+
+	err = os.WriteFile(rootsFile, []byte(rootsContent), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = os.WriteFile(extraRootsFile, []byte(extraRootsContent), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Create test config
+	configContent := `listen:
+  - ":8080"
+roots: "` + rootsFile + `"
+logs:
+  - shortname: "test-log"
+    submissionprefix: "https://example.com/submit"
+    monitoringprefix: "https://example.com/monitor"
+    extraroots: "` + extraRootsFile + `"
+    secret: "test-data/test-log.key"
+    localdirectory: "` + testLogDir + `"
+    listen: ":8081"
+    notafterstart: "2024-01-01T00:00:00Z"
+    notafterlimit: "2025-01-01T00:00:00Z"
+  - shortname: "test-log-2"
+    submissionprefix: "https://log2.example.com/submit"
+    monitoringprefix: "https://log2.example.com/monitor"
+    secret: "test-data/test-log-2.key"
+    localdirectory: "` + testLog2Dir + `"`
+
+	configFile := filepath.Join(tmpDir, "test-config.yaml")
+	err = os.WriteFile(configFile, []byte(configContent), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Run generateEnv
+	generateEnv(configFile, false, true, false)
+
+	// Verify .env file was created for first log
+	envFile := filepath.Join(testLogDir, ".env")
+	envContent, err := os.ReadFile(envFile)
+	if err != nil {
+		t.Fatalf("Failed to read .env file: %v", err)
+	}
+
+	envStr := string(envContent)
+
+	// Check TESSERACT_ARGS contains expected values
+	if !strings.Contains(envStr, "TESSERACT_ARGS=") {
+		t.Error("Expected TESSERACT_ARGS in .env file")
+	}
+	if !strings.Contains(envStr, "--private_key=test-data/test-log.key") {
+		t.Error("Expected private_key argument in TESSERACT_ARGS")
+	}
+	if !strings.Contains(envStr, "--origin=example.com") {
+		t.Error("Expected origin argument in TESSERACT_ARGS")
+	}
+	if !strings.Contains(envStr, "--storage_dir="+testLogDir) {
+		t.Error("Expected storage_dir argument in TESSERACT_ARGS")
+	}
+	if !strings.Contains(envStr, "--http_endpoint=:8081") {
+		t.Error("Expected http_endpoint argument in TESSERACT_ARGS")
+	}
+	if !strings.Contains(envStr, "--not_after_start=2024-01-01T00:00:00Z") {
+		t.Error("Expected not_after_start argument in TESSERACT_ARGS")
+	}
+	if !strings.Contains(envStr, "--not_after_limit=2025-01-01T00:00:00Z") {
+		t.Error("Expected not_after_limit argument in TESSERACT_ARGS")
+	}
+	if !strings.Contains(envStr, "OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4318") {
+		t.Error("Expected OTEL_EXPORTER_OTLP_ENDPOINT in .env file")
+	}
+
+	// Verify combined roots.pem was created
+	combinedRootsFile := filepath.Join(testLogDir, "roots.pem")
+	combinedContent, err := os.ReadFile(combinedRootsFile)
+	if err != nil {
+		t.Fatalf("Failed to read combined roots.pem: %v", err)
+	}
+
+	combinedStr := string(combinedContent)
+	if !strings.Contains(combinedStr, "MIIBkTCB+wIJAKZJ") {
+		t.Error("Expected content from main roots file")
+	}
+	if !strings.Contains(combinedStr, "MIIBkTCB+wIJAKZK") {
+		t.Error("Expected content from extra roots file")
+	}
+
+	// Verify second log's .env file was created
+	env2File := filepath.Join(testLog2Dir, ".env")
+	env2Content, err := os.ReadFile(env2File)
+	if err != nil {
+		t.Fatalf("Failed to read second .env file: %v", err)
+	}
+
+	env2Str := string(env2Content)
+	if !strings.Contains(env2Str, "--origin=log2.example.com") {
+		t.Error("Expected correct origin for second log")
+	}
+	if strings.Contains(env2Str, "--http_endpoint=") {
+		t.Error("Second log should not have http_endpoint (not specified)")
+	}
+}
+
+func TestCreateCombinedRootsPemWithStatus(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	// Test case 1: Both files exist
+	rootsFile := filepath.Join(tmpDir, "roots.pem")
+	extraFile := filepath.Join(tmpDir, "extra.pem")
+	outputFile := filepath.Join(tmpDir, "combined.pem")
+
+	rootsContent := "ROOT CERT CONTENT\n"
+	extraContent := "EXTRA CERT CONTENT\n"
+
+	err := os.WriteFile(rootsFile, []byte(rootsContent), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = os.WriteFile(extraFile, []byte(extraContent), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = createCombinedRootsPemWithStatus(rootsFile, extraFile, outputFile, false, true, false)
+	if err != nil {
+		t.Errorf("createCombinedRootsPemWithStatus() error = %v", err)
+	}
+
+	combinedContent, err := os.ReadFile(outputFile)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expected := rootsContent + extraContent
+	if string(combinedContent) != expected {
+		t.Errorf("Combined content = %s, want %s", string(combinedContent), expected)
+	}
+
+	// Test case 2: Only roots file exists
+	outputFile2 := filepath.Join(tmpDir, "combined2.pem")
+	err = createCombinedRootsPemWithStatus(rootsFile, "", outputFile2, false, true, false)
+	if err != nil {
+		t.Errorf("createCombinedRootsPemWithStatus() with empty extra file error = %v", err)
+	}
+
+	combinedContent2, err := os.ReadFile(outputFile2)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if string(combinedContent2) != rootsContent {
+		t.Errorf("Combined content = %s, want %s", string(combinedContent2), rootsContent)
+	}
+
+	// Test case 3: Extra file doesn't exist (should error)
+	outputFile3 := filepath.Join(tmpDir, "combined3.pem")
+	err = createCombinedRootsPemWithStatus(rootsFile, "nonexistent.pem", outputFile3, false, true, false)
+	if err == nil {
+		t.Error("Expected error when extra file doesn't exist")
+	}
+}
+
+func TestGenerateEnvMissingDirectory(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	// Create config with non-existent directory
+	configContent := `logs:
+  - shortname: "test-log"
+    submissionprefix: "https://example.com/submit"
+    secret: "test.key"
+    localdirectory: "/nonexistent/directory"`
+
+	configFile := filepath.Join(tmpDir, "test-config.yaml")
+	err := os.WriteFile(configFile, []byte(configContent), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Should call log.Fatalf which exits the program
+	// We can't easily test this without subprocess, so we'll skip it
+	t.Skip("Cannot easily test log.Fatalf without subprocess")
+}

tesseract/genconf/html.go

@@ -74,7 +74,7 @@ const htmlTemplate = `<!DOCTYPE html>
 
     {{range .Logs}}
 
-    <h2>{{.ShortName}}.log.ct.ipng.ch</h2>
+    <h2>{{.Origin}}</h2>
 
     <p>
       Log ID: <code>{{.LogID}}</code><br>
@@ -95,6 +95,7 @@ const htmlTemplate = `<!DOCTYPE html>
 </html>
 `
 
+// LogV3JSON represents the Certificate Transparency log v3 JSON metadata format
 type LogV3JSON struct {
 	Description      string           `json:"description"`
 	SubmissionURL    string           `json:"submission_url"`
@@ -105,12 +106,13 @@ type LogV3JSON struct {
 	MMD              int              `json:"mmd"`
 }
 
+// TemporalInterval represents the time range for a Certificate Transparency log
 type TemporalInterval struct {
 	StartInclusive string `json:"start_inclusive"`
 	EndExclusive   string `json:"end_exclusive"`
 }
 
-func generateHTML(yamlFile string) {
+func generateHTML(yamlFile string, wantDiff bool, allowWrite bool, useColor bool) {
 	config := loadConfig(yamlFile)
 
 	// Check that all local directories exist
@@ -145,14 +147,14 @@ func generateHTML(yamlFile string) {
 		}
 
 		// Write file with status
-		err = writeFileWithStatus(indexPath, buf.Bytes())
+		err = writeFileWithStatus(indexPath, buf.Bytes(), wantDiff, allowWrite, useColor)
 		if err != nil {
 			log.Fatalf("Failed to write HTML to %s: %v", indexPath, err)
 		}
 
 		// Generate log.v3.json for this log
 		jsonPath := filepath.Join(logEntry.LocalDirectory, "log.v3.json")
-		err = generateLogJSONWithStatus(logEntry, jsonPath)
+		err = generateLogJSONWithStatus(logEntry, jsonPath, wantDiff, allowWrite, useColor)
 		if err != nil {
 			log.Fatalf("Failed to generate %s: %v", jsonPath, err)
 		}
@@ -209,9 +211,9 @@ func computeKeyInfo(logEntry *Log) error {
 	return nil
 }
 
-func generateLogJSONWithStatus(logEntry Log, outputPath string) error {
+func generateLogJSONWithStatus(logEntry Log, outputPath string, wantDiff bool, allowWrite bool, useColor bool) error {
 	logJSON := LogV3JSON{
-		Description:   fmt.Sprintf("%s.log.ct.ipng.ch", logEntry.ShortName),
+		Description:   logEntry.Origin,
 		SubmissionURL: fmt.Sprintf("%s/", logEntry.SubmissionPrefix),
 		MonitoringURL: fmt.Sprintf("%s/", logEntry.MonitoringPrefix),
 		TemporalInterval: TemporalInterval{
@@ -228,5 +230,5 @@ func generateLogJSONWithStatus(logEntry Log, outputPath string) error {
 		return fmt.Errorf("failed to marshal JSON: %v", err)
 	}
 
-	return writeFileWithStatus(outputPath, jsonData)
+	return writeFileWithStatus(outputPath, jsonData, wantDiff, allowWrite, useColor)
 }

tesseract/genconf/html_test.go

@@ -0,0 +1,316 @@
+package main
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/x509"
+	"encoding/json"
+	"encoding/pem"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestGenerateHTML(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	// Create test directories
+	testLogDir := filepath.Join(tmpDir, "test-log")
+	err := os.MkdirAll(testLogDir, 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Generate test private key
+	privKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	privKeyDER, err := x509.MarshalECPrivateKey(privKey)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	privKeyPEM := pem.EncodeToMemory(&pem.Block{
+		Type:  "EC PRIVATE KEY",
+		Bytes: privKeyDER,
+	})
+
+	keyFile := filepath.Join(tmpDir, "test-key.pem")
+	err = os.WriteFile(keyFile, privKeyPEM, 0600)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Create test config
+	configContent := `listen:
+  - ":8080"
+logs:
+  - shortname: "test-log"
+    submissionprefix: "https://example.com/submit"
+    monitoringprefix: "https://example.com/monitor"
+    secret: "` + keyFile + `"
+    localdirectory: "` + testLogDir + `"
+    notafterstart: "2024-01-01T00:00:00Z"
+    notafterlimit: "2025-01-01T00:00:00Z"`
+
+	configFile := filepath.Join(tmpDir, "test-config.yaml")
+	err = os.WriteFile(configFile, []byte(configContent), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Run generateHTML
+	generateHTML(configFile, false, true, false)
+
+	// Verify HTML file was created
+	htmlFile := filepath.Join(testLogDir, "index.html")
+	htmlContent, err := os.ReadFile(htmlFile)
+	if err != nil {
+		t.Fatalf("Failed to read HTML file: %v", err)
+	}
+
+	htmlStr := string(htmlContent)
+
+	// Check HTML contains expected elements
+	if !strings.Contains(htmlStr, "<!DOCTYPE html>") {
+		t.Error("Expected HTML doctype")
+	}
+	if !strings.Contains(htmlStr, "TesseraCT") {
+		t.Error("Expected TesseraCT title")
+	}
+	if !strings.Contains(htmlStr, "example.com") {
+		t.Error("Expected origin hostname in HTML")
+	}
+	if !strings.Contains(htmlStr, "https://example.com/submit/") {
+		t.Error("Expected submission prefix in HTML")
+	}
+	if !strings.Contains(htmlStr, "https://example.com/monitor/") {
+		t.Error("Expected monitoring prefix in HTML")
+	}
+	if !strings.Contains(htmlStr, "2024-01-01T00:00:00Z") {
+		t.Error("Expected start time in HTML")
+	}
+	if !strings.Contains(htmlStr, "2025-01-01T00:00:00Z") {
+		t.Error("Expected end time in HTML")
+	}
+	if !strings.Contains(htmlStr, "-----BEGIN PUBLIC KEY-----") {
+		t.Error("Expected public key in HTML")
+	}
+
+	// Verify JSON file was created
+	jsonFile := filepath.Join(testLogDir, "log.v3.json")
+	jsonContent, err := os.ReadFile(jsonFile)
+	if err != nil {
+		t.Fatalf("Failed to read JSON file: %v", err)
+	}
+
+	var logJSON LogV3JSON
+	err = json.Unmarshal(jsonContent, &logJSON)
+	if err != nil {
+		t.Fatalf("Failed to parse JSON: %v", err)
+	}
+
+	// Verify JSON content
+	if logJSON.Description != "example.com" {
+		t.Errorf("Expected description 'example.com', got %s", logJSON.Description)
+	}
+	if logJSON.SubmissionURL != "https://example.com/submit/" {
+		t.Errorf("Expected submission URL 'https://example.com/submit/', got %s", logJSON.SubmissionURL)
+	}
+	if logJSON.MonitoringURL != "https://example.com/monitor/" {
+		t.Errorf("Expected monitoring URL 'https://example.com/monitor/', got %s", logJSON.MonitoringURL)
+	}
+	if logJSON.TemporalInterval.StartInclusive != "2024-01-01T00:00:00Z" {
+		t.Errorf("Expected start time '2024-01-01T00:00:00Z', got %s", logJSON.TemporalInterval.StartInclusive)
+	}
+	if logJSON.TemporalInterval.EndExclusive != "2025-01-01T00:00:00Z" {
+		t.Errorf("Expected end time '2025-01-01T00:00:00Z', got %s", logJSON.TemporalInterval.EndExclusive)
+	}
+	if logJSON.MMD != 60 {
+		t.Errorf("Expected MMD 60, got %d", logJSON.MMD)
+	}
+	if logJSON.LogID == "" {
+		t.Error("Expected non-empty LogID")
+	}
+	if logJSON.Key == "" {
+		t.Error("Expected non-empty Key")
+	}
+}
+
+func TestComputeKeyInfo(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	// Generate test private key
+	privKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	privKeyDER, err := x509.MarshalECPrivateKey(privKey)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	privKeyPEM := pem.EncodeToMemory(&pem.Block{
+		Type:  "EC PRIVATE KEY",
+		Bytes: privKeyDER,
+	})
+
+	keyFile := filepath.Join(tmpDir, "test-key.pem")
+	err = os.WriteFile(keyFile, privKeyPEM, 0600)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Create log entry
+	logEntry := Log{
+		ShortName: "test-log",
+		Secret:    keyFile,
+	}
+
+	// Compute key info
+	err = computeKeyInfo(&logEntry)
+	if err != nil {
+		t.Fatalf("computeKeyInfo() error = %v", err)
+	}
+
+	// Verify computed fields
+	if logEntry.LogID == "" {
+		t.Error("Expected non-empty LogID")
+	}
+	if logEntry.PublicKeyPEM == "" {
+		t.Error("Expected non-empty PublicKeyPEM")
+	}
+	if !strings.Contains(logEntry.PublicKeyPEM, "-----BEGIN PUBLIC KEY-----") {
+		t.Error("Expected PEM format public key")
+	}
+	if !strings.Contains(logEntry.PublicKeyPEM, "-----END PUBLIC KEY-----") {
+		t.Error("Expected PEM format public key")
+	}
+	if logEntry.PublicKeyDERB64 == "" {
+		t.Error("Expected non-empty PublicKeyDERB64")
+	}
+	if logEntry.PublicKeyBase64 == "" {
+		t.Error("Expected non-empty PublicKeyBase64")
+	}
+	if logEntry.PublicKeyDERB64 != logEntry.PublicKeyBase64 {
+		t.Error("Expected PublicKeyDERB64 and PublicKeyBase64 to be the same")
+	}
+}
+
+func TestComputeKeyInfoInvalidKey(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	// Create invalid key file
+	invalidKeyFile := filepath.Join(tmpDir, "invalid-key.pem")
+	invalidKeyContent := `-----BEGIN EC PRIVATE KEY-----
+INVALID KEY DATA
+-----END EC PRIVATE KEY-----`
+
+	err := os.WriteFile(invalidKeyFile, []byte(invalidKeyContent), 0600)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	logEntry := Log{
+		Secret: invalidKeyFile,
+	}
+
+	err = computeKeyInfo(&logEntry)
+	if err == nil {
+		t.Error("Expected error for invalid key file")
+	}
+}
+
+func TestComputeKeyInfoMissingFile(t *testing.T) {
+	logEntry := Log{
+		Secret: "/nonexistent/key.pem",
+	}
+
+	err := computeKeyInfo(&logEntry)
+	if err == nil {
+		t.Error("Expected error for missing key file")
+	}
+}
+
+func TestGenerateLogJSONWithStatus(t *testing.T) {
+	tmpDir := t.TempDir()
+	outputFile := filepath.Join(tmpDir, "test-log.v3.json")
+
+	testTime1, _ := time.Parse("2006-01-02T15:04:05Z", "2024-01-01T00:00:00Z")
+	testTime2, _ := time.Parse("2006-01-02T15:04:05Z", "2025-01-01T00:00:00Z")
+
+	logEntry := Log{
+		Origin:           "test.example.com",
+		SubmissionPrefix: "https://test.example.com/submit",
+		MonitoringPrefix: "https://test.example.com/monitor",
+		NotAfterStart:    testTime1,
+		NotAfterLimit:    testTime2,
+		LogID:            "dGVzdC1sb2ctaWQ=",     // base64 encoded "test-log-id"
+		PublicKeyBase64:  "dGVzdC1wdWJsaWMta2V5", // base64 encoded "test-public-key"
+	}
+
+	err := generateLogJSONWithStatus(logEntry, outputFile, false, true, false)
+	if err != nil {
+		t.Fatalf("generateLogJSONWithStatus() error = %v", err)
+	}
+
+	// Verify JSON was created
+	jsonContent, err := os.ReadFile(outputFile)
+	if err != nil {
+		t.Fatalf("Failed to read JSON file: %v", err)
+	}
+
+	var logJSON LogV3JSON
+	err = json.Unmarshal(jsonContent, &logJSON)
+	if err != nil {
+		t.Fatalf("Failed to parse JSON: %v", err)
+	}
+
+	// Verify content
+	if logJSON.Description != "test.example.com" {
+		t.Errorf("Expected description 'test.example.com', got %s", logJSON.Description)
+	}
+	if logJSON.SubmissionURL != "https://test.example.com/submit/" {
+		t.Errorf("Expected submission URL to have trailing slash")
+	}
+	if logJSON.MonitoringURL != "https://test.example.com/monitor/" {
+		t.Errorf("Expected monitoring URL to have trailing slash")
+	}
+	if logJSON.LogID != "dGVzdC1sb2ctaWQ=" {
+		t.Errorf("Expected LogID 'dGVzdC1sb2ctaWQ=', got %s", logJSON.LogID)
+	}
+	if logJSON.Key != "dGVzdC1wdWJsaWMta2V5" {
+		t.Errorf("Expected Key 'dGVzdC1wdWJsaWMta2V5', got %s", logJSON.Key)
+	}
+	if logJSON.MMD != 60 {
+		t.Errorf("Expected MMD 60, got %d", logJSON.MMD)
+	}
+}
+
+func TestGenerateHTMLMissingDirectory(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	// Create config with non-existent directory
+	configContent := `logs:
+  - shortname: "test-log"
+    submissionprefix: "https://example.com/submit"
+    monitoringprefix: "https://example.com/monitor"
+    secret: "test.key"
+    localdirectory: "/nonexistent/directory"`
+
+	configFile := filepath.Join(tmpDir, "test-config.yaml")
+	err := os.WriteFile(configFile, []byte(configContent), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Should call log.Fatalf which exits the program
+	// We can't easily test this without subprocess, so we'll skip it
+	t.Skip("Cannot easily test log.Fatalf without subprocess")
+}

tesseract/genconf/key.go

@@ -12,7 +12,12 @@ import (
 	"path/filepath"
 )
 
-func generateKeys(yamlFile string) {
+func generateKeys(yamlFile string, wantDiff bool, allowWrite bool, useColor bool) {
+	if !allowWrite {
+		fmt.Printf("Key generation requires --write flag\n")
+		return
+	}
+
 	config := loadConfig(yamlFile)
 
 	// Generate keys for each log

tesseract/genconf/key_test.go

@@ -0,0 +1,296 @@
+package main
+
+import (
+	"crypto/elliptic"
+	"crypto/x509"
+	"encoding/pem"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestGenerateKeys(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	// Create test directories
+	keyDir := filepath.Join(tmpDir, "keys")
+	err := os.MkdirAll(keyDir, 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Create test config
+	key1Path := filepath.Join(keyDir, "test-log-1.key")
+	key2Path := filepath.Join(keyDir, "test-log-2.key")
+
+	configContent := `logs:
+  - shortname: "test-log-1"
+    secret: "` + key1Path + `"
+  - shortname: "test-log-2"  
+    secret: "` + key2Path + `"`
+
+	configFile := filepath.Join(tmpDir, "test-config.yaml")
+	err = os.WriteFile(configFile, []byte(configContent), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Run generateKeys
+	generateKeys(configFile, false, true, false)
+
+	// Verify first key was created
+	if _, err := os.Stat(key1Path); os.IsNotExist(err) {
+		t.Error("Expected first key file to be created")
+	}
+
+	// Verify second key was created
+	if _, err := os.Stat(key2Path); os.IsNotExist(err) {
+		t.Error("Expected second key file to be created")
+	}
+
+	// Verify key format
+	keyContent, err := os.ReadFile(key1Path)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	keyStr := string(keyContent)
+	if !strings.Contains(keyStr, "-----BEGIN EC PRIVATE KEY-----") {
+		t.Error("Expected EC private key PEM header")
+	}
+	if !strings.Contains(keyStr, "-----END EC PRIVATE KEY-----") {
+		t.Error("Expected EC private key PEM footer")
+	}
+
+	// Verify key can be parsed
+	block, _ := pem.Decode(keyContent)
+	if block == nil {
+		t.Error("Failed to decode PEM block")
+	}
+
+	privKey, err := x509.ParseECPrivateKey(block.Bytes)
+	if err != nil {
+		t.Errorf("Failed to parse EC private key: %v", err)
+	}
+
+	// Verify it's a P-256 key
+	if privKey.Curve != elliptic.P256() {
+		t.Error("Expected P-256 curve")
+	}
+
+	// Verify file permissions
+	info, err := os.Stat(key1Path)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	perm := info.Mode().Perm()
+	expected := os.FileMode(0600)
+	if perm != expected {
+		t.Errorf("Expected file mode %o, got %o", expected, perm)
+	}
+}
+
+func TestGenerateKeysExistingKey(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	// Create existing key file
+	keyPath := filepath.Join(tmpDir, "existing.key")
+	existingContent := `-----BEGIN EC PRIVATE KEY-----
+MHcCAQEEIExistingKeyContent
+-----END EC PRIVATE KEY-----`
+
+	err := os.WriteFile(keyPath, []byte(existingContent), 0600)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Create test config
+	configContent := `logs:
+  - shortname: "test-log"
+    secret: "` + keyPath + `"`
+
+	configFile := filepath.Join(tmpDir, "test-config.yaml")
+	err = os.WriteFile(configFile, []byte(configContent), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Run generateKeys
+	generateKeys(configFile, false, true, false)
+
+	// Verify existing key was not overwritten
+	keyContent, err := os.ReadFile(keyPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if string(keyContent) != existingContent {
+		t.Error("Expected existing key to be preserved")
+	}
+}
+
+func TestGenerateKeysWithoutWriteFlag(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	keyPath := filepath.Join(tmpDir, "test.key")
+
+	configContent := `logs:
+  - shortname: "test-log"
+    secret: "` + keyPath + `"`
+
+	configFile := filepath.Join(tmpDir, "test-config.yaml")
+	err := os.WriteFile(configFile, []byte(configContent), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Run generateKeys without write flag
+	generateKeys(configFile, false, false, false)
+
+	// Verify key was not created
+	if _, err := os.Stat(keyPath); !os.IsNotExist(err) {
+		t.Error("Expected key file to not be created without --write flag")
+	}
+}
+
+func TestGenerateKeysCreateDirectory(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	// Key path with non-existent directory
+	keyDir := filepath.Join(tmpDir, "subdir", "keys")
+	keyPath := filepath.Join(keyDir, "test.key")
+
+	configContent := `logs:
+  - shortname: "test-log"
+    secret: "` + keyPath + `"`
+
+	configFile := filepath.Join(tmpDir, "test-config.yaml")
+	err := os.WriteFile(configFile, []byte(configContent), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Run generateKeys
+	generateKeys(configFile, false, true, false)
+
+	// Verify directory was created
+	if _, err := os.Stat(keyDir); os.IsNotExist(err) {
+		t.Error("Expected directory to be created")
+	}
+
+	// Verify key was created
+	if _, err := os.Stat(keyPath); os.IsNotExist(err) {
+		t.Error("Expected key file to be created")
+	}
+}
+
+func TestGenerateKeysMultipleRuns(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	key1Path := filepath.Join(tmpDir, "key1.key")
+	key2Path := filepath.Join(tmpDir, "key2.key")
+
+	configContent := `logs:
+  - shortname: "test-log-1"
+    secret: "` + key1Path + `"
+  - shortname: "test-log-2"
+    secret: "` + key2Path + `"`
+
+	configFile := filepath.Join(tmpDir, "test-config.yaml")
+	err := os.WriteFile(configFile, []byte(configContent), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// First run - should create both keys
+	generateKeys(configFile, false, true, false)
+
+	// Read first key content
+	key1Content, err := os.ReadFile(key1Path)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	key2Content, err := os.ReadFile(key2Path)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Second run - should not overwrite existing keys
+	generateKeys(configFile, false, true, false)
+
+	// Verify keys are unchanged
+	key1Content2, err := os.ReadFile(key1Path)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	key2Content2, err := os.ReadFile(key2Path)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if string(key1Content) != string(key1Content2) {
+		t.Error("First key should not have been overwritten")
+	}
+
+	if string(key2Content) != string(key2Content2) {
+		t.Error("Second key should not have been overwritten")
+	}
+}
+
+func TestECKeyGeneration(t *testing.T) {
+	tmpDir := t.TempDir()
+	keyPath := filepath.Join(tmpDir, "test.key")
+
+	configContent := `logs:
+  - shortname: "test-log"
+    secret: "` + keyPath + `"`
+
+	configFile := filepath.Join(tmpDir, "test-config.yaml")
+	err := os.WriteFile(configFile, []byte(configContent), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	generateKeys(configFile, false, true, false)
+
+	// Read and parse the generated key
+	keyContent, err := os.ReadFile(keyPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	block, _ := pem.Decode(keyContent)
+	if block == nil {
+		t.Fatal("Failed to decode PEM block")
+	}
+
+	if block.Type != "EC PRIVATE KEY" {
+		t.Errorf("Expected block type 'EC PRIVATE KEY', got %s", block.Type)
+	}
+
+	privKey, err := x509.ParseECPrivateKey(block.Bytes)
+	if err != nil {
+		t.Fatalf("Failed to parse EC private key: %v", err)
+	}
+
+	// Verify public key can be derived
+	pubKey := &privKey.PublicKey
+	if pubKey.X == nil || pubKey.Y == nil {
+		t.Error("Public key coordinates should not be nil")
+	}
+
+	// Verify key is on the correct curve
+	if !pubKey.Curve.IsOnCurve(pubKey.X, pubKey.Y) {
+		t.Error("Public key is not on the curve")
+	}
+
+	// Verify we can marshal the public key (for log ID computation)
+	_, err = x509.MarshalPKIXPublicKey(pubKey)
+	if err != nil {
+		t.Errorf("Failed to marshal public key: %v", err)
+	}
+}

tesseract/genconf/main.go

@@ -5,11 +5,16 @@ import (
 	"fmt"
 	"log"
 	"os"
+	"strings"
 	"time"
 
+	"github.com/hexops/gotextdiff"
+	"github.com/hexops/gotextdiff/myers"
+	"github.com/hexops/gotextdiff/span"
 	"gopkg.in/yaml.v3"
 )
 
+// Config represents the main YAML configuration structure for tesseract
 type Config struct {
 	Listen      []string `yaml:"listen"`
 	Checkpoints string   `yaml:"checkpoints"`
@@ -17,6 +22,7 @@ type Config struct {
 	Logs        []Log    `yaml:"logs"`
 }
 
+// Log represents a single Certificate Transparency log configuration
 type Log struct {
 	ShortName        string    `yaml:"shortname"`
 	Inception        string    `yaml:"inception"`
@@ -37,10 +43,14 @@ type Log struct {
 	PublicKeyPEM    string
 	PublicKeyDERB64 string
 	PublicKeyBase64 string
+	Origin          string
 }
 
 func main() {
 	configFile := flag.String("c", "./tesseract-staging.yaml", "Path to the YAML configuration file")
+	wantDiff := flag.Bool("diff", false, "Show unified diff of changes")
+	allowWrite := flag.Bool("write", false, "Allow writing files (required for actual file modifications)")
+	noColor := flag.Bool("no-color", false, "Disable colored diff output")
 	flag.Parse()
 
 	args := flag.Args()
@@ -51,15 +61,15 @@ func main() {
 
 	switch args[0] {
 	case "gen-html":
-		generateHTML(*configFile)
+		generateHTML(*configFile, *wantDiff, *allowWrite, !*noColor)
 	case "gen-env":
-		generateEnv(*configFile)
+		generateEnv(*configFile, *wantDiff, *allowWrite, !*noColor)
 	case "gen-key":
-		generateKeys(*configFile)
+		generateKeys(*configFile, *wantDiff, *allowWrite, !*noColor)
 	case "gen-nginx":
-		generateNginx(*configFile)
+		generateNginx(*configFile, *wantDiff, *allowWrite, !*noColor)
 	case "gen-roots":
-		generateRoots(args[1:])
+		generateRoots(args[1:], *wantDiff, *allowWrite, !*noColor)
 	default:
 		fmt.Fprintf(os.Stderr, "Unknown command: %s\n", args[0])
 		showHelp()
@@ -92,22 +102,108 @@ func loadConfig(yamlFile string) Config {
 		if config.Logs[i].Period == 0 {
 			config.Logs[i].Period = 200
 		}
+
+		// Extract hostname from SubmissionPrefix to set Origin
+		if config.Logs[i].SubmissionPrefix != "" {
+			hostname, err := extractHostname(config.Logs[i].SubmissionPrefix)
+			if err != nil {
+				log.Fatalf("Failed to parse SubmissionPrefix URL for %s: %v", config.Logs[i].ShortName, err)
+			}
+			config.Logs[i].Origin = hostname
+		}
 	}
 
 	return config
 }
 
-func writeFileWithStatus(filename string, content []byte) error {
+// ANSI color codes
+const (
+	colorReset  = "\033[0m"
+	colorRed    = "\033[31m"
+	colorGreen  = "\033[32m"
+	colorYellow = "\033[33m"
+	colorCyan   = "\033[36m"
+)
+
+// colorizeUnifiedDiff adds ANSI color codes to unified diff output
+func colorizeUnifiedDiff(diff string) string {
+	lines := strings.Split(diff, "\n")
+	var colorizedLines []string
+
+	for _, line := range lines {
+		switch {
+		case strings.HasPrefix(line, "---"):
+			// File deletion header in cyan
+			colorizedLines = append(colorizedLines, colorCyan+line+colorReset)
+		case strings.HasPrefix(line, "+++"):
+			// File addition header in cyan
+			colorizedLines = append(colorizedLines, colorCyan+line+colorReset)
+		case strings.HasPrefix(line, "@@"):
+			// Hunk header in yellow
+			colorizedLines = append(colorizedLines, colorYellow+line+colorReset)
+		case strings.HasPrefix(line, "-"):
+			// Deleted lines in red
+			colorizedLines = append(colorizedLines, colorRed+line+colorReset)
+		case strings.HasPrefix(line, "+"):
+			// Added lines in green
+			colorizedLines = append(colorizedLines, colorGreen+line+colorReset)
+		default:
+			// Context lines unchanged
+			colorizedLines = append(colorizedLines, line)
+		}
+	}
+
+	return strings.Join(colorizedLines, "\n")
+}
+
+func writeFileWithStatus(filename string, content []byte, wantDiff bool, allowWrite bool, useColor bool) error {
 	existingContent, err := os.ReadFile(filename)
-	if os.IsNotExist(err) {
-		fmt.Printf("Creating %s\n", filename)
+	isNew := os.IsNotExist(err)
+	isUnchanged := false
+
+	if isNew {
+		if allowWrite {
+			fmt.Printf("Creating %s\n", filename)
+		} else {
+			fmt.Printf("Would create %s\n", filename)
+		}
 	} else if err != nil {
 		return fmt.Errorf("failed to read existing file %s: %v", filename, err)
 	} else if string(existingContent) == string(content) {
 		fmt.Printf("Unchanged %s\n", filename)
-		return nil
+		isUnchanged = true
 	} else {
-		fmt.Printf("Updating %s\n", filename)
+		if allowWrite {
+			fmt.Printf("Updating %s\n", filename)
+		} else {
+			fmt.Printf("Would update %s\n", filename)
+		}
+	}
+
+	if wantDiff && !isUnchanged {
+		if isNew {
+			// For new files, show the entire content as added
+			edits := myers.ComputeEdits(span.URIFromPath(filename), "", string(content))
+			diff := fmt.Sprint(gotextdiff.ToUnified("/dev/null", filename, "", edits))
+			if useColor {
+				fmt.Print(colorizeUnifiedDiff(diff))
+			} else {
+				fmt.Print(diff)
+			}
+		} else {
+			// For existing files, show the diff
+			edits := myers.ComputeEdits(span.URIFromPath(filename), string(existingContent), string(content))
+			diff := fmt.Sprint(gotextdiff.ToUnified(filename, filename+".new", string(existingContent), edits))
+			if useColor {
+				fmt.Print(colorizeUnifiedDiff(diff))
+			} else {
+				fmt.Print(diff)
+			}
+		}
+	}
+
+	if isUnchanged || !allowWrite {
+		return nil
 	}
 
 	err = os.WriteFile(filename, content, 0644)
@@ -119,8 +215,17 @@ func writeFileWithStatus(filename string, content []byte) error {
 
 func showHelp() {
 	fmt.Printf("Usage: %s [options] <command>\n\n", os.Args[0])
+	fmt.Printf("Note: Flags must come before the command name.\n\n")
 	fmt.Printf("Options:\n")
-	fmt.Printf("  -c <file>    Path to YAML configuration file (default: ./tesseract-staging.yaml)\n\n")
+	fmt.Printf("  -c <file>    Path to YAML configuration file (default: ./tesseract-staging.yaml)\n")
+	fmt.Printf("  --diff       Show unified diff of changes without writing files\n")
+	fmt.Printf("  --write      Allow writing files (required for actual file modifications)\n")
+	fmt.Printf("  --no-color   Disable colored diff output\n\n")
+	fmt.Printf("Examples:\n")
+	fmt.Printf("  %s --diff gen-html            # Show colored diffs without writing\n", os.Args[0])
+	fmt.Printf("  %s --diff --no-color gen-html # Show plain diffs without writing\n", os.Args[0])
+	fmt.Printf("  %s --write gen-html           # Write files\n", os.Args[0])
+	fmt.Printf("  %s --diff --write gen-html    # Show colored diffs and write files\n\n", os.Args[0])
 	fmt.Printf("Commands:\n")
 	fmt.Printf("  gen-html     Generate index.html and log.v3.json files in each log's localdirectory.\n")
 	fmt.Printf("               Creates HTML pages with log information and CT log metadata JSON.\n")

tesseract/genconf/main_test.go

@@ -0,0 +1,273 @@
+package main
+
+import (
+	"os"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestLoadConfig(t *testing.T) {
+	tests := []struct {
+		name        string
+		yamlContent string
+		wantError   bool
+		checkFields func(*testing.T, Config)
+	}{
+		{
+			name: "valid config with all fields",
+			yamlContent: `listen:
+  - ":8080"
+checkpoints: "checkpoints"
+roots: "roots.pem"
+logs:
+  - shortname: "test-log"
+    inception: "2024-01-01T00:00:00Z"
+    period: 300
+    poolsize: 1000
+    submissionprefix: "https://example.com/submit"
+    monitoringprefix: "https://example.com/monitor"
+    secret: "test.key"
+    localdirectory: "test-dir"
+    notafterstart: "2024-01-01T00:00:00Z"
+    notafterlimit: "2025-01-01T00:00:00Z"`,
+			wantError: false,
+			checkFields: func(t *testing.T, config Config) {
+				if len(config.Listen) != 1 || config.Listen[0] != ":8080" {
+					t.Errorf("Expected Listen [\":8080\"], got %v", config.Listen)
+				}
+				if config.Checkpoints != "checkpoints" {
+					t.Errorf("Expected Checkpoints \"checkpoints\", got %s", config.Checkpoints)
+				}
+				if len(config.Logs) != 1 {
+					t.Errorf("Expected 1 log, got %d", len(config.Logs))
+				}
+				log := config.Logs[0]
+				if log.ShortName != "test-log" {
+					t.Errorf("Expected ShortName \"test-log\", got %s", log.ShortName)
+				}
+				if log.Period != 300 {
+					t.Errorf("Expected Period 300, got %d", log.Period)
+				}
+				if log.PoolSize != 1000 {
+					t.Errorf("Expected PoolSize 1000, got %d", log.PoolSize)
+				}
+				if log.Origin != "example.com" {
+					t.Errorf("Expected Origin \"example.com\", got %s", log.Origin)
+				}
+			},
+		},
+		{
+			name: "config with defaults",
+			yamlContent: `logs:
+  - shortname: "minimal-log"
+    submissionprefix: "https://test.example.com/submit"
+    secret: "test.key"
+    localdirectory: "test-dir"`,
+			wantError: false,
+			checkFields: func(t *testing.T, config Config) {
+				if len(config.Listen) != 1 || config.Listen[0] != ":8080" {
+					t.Errorf("Expected default Listen [\":8080\"], got %v", config.Listen)
+				}
+				if len(config.Logs) != 1 {
+					t.Errorf("Expected 1 log, got %d", len(config.Logs))
+				}
+				log := config.Logs[0]
+				if log.Period != 200 {
+					t.Errorf("Expected default Period 200, got %d", log.Period)
+				}
+				if log.PoolSize != 750 {
+					t.Errorf("Expected default PoolSize 750, got %d", log.PoolSize)
+				}
+				if log.Origin != "test.example.com" {
+					t.Errorf("Expected Origin \"test.example.com\", got %s", log.Origin)
+				}
+			},
+		},
+		{
+			name: "invalid yaml",
+			yamlContent: `invalid: yaml: content:
+  - malformed`,
+			wantError: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			tmpfile, err := os.CreateTemp("", "test-config-*.yaml")
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer os.Remove(tmpfile.Name())
+
+			_, err = tmpfile.WriteString(tt.yamlContent)
+			if err != nil {
+				t.Fatal(err)
+			}
+			tmpfile.Close()
+
+			if tt.wantError {
+				// Can't easily test log.Fatalf without subprocess
+				t.Skip("Cannot easily test log.Fatalf without subprocess")
+			} else {
+				config := loadConfig(tmpfile.Name())
+				if tt.checkFields != nil {
+					tt.checkFields(t, config)
+				}
+			}
+		})
+	}
+}
+
+func TestExtractHostname(t *testing.T) {
+	tests := []struct {
+		name    string
+		urlStr  string
+		want    string
+		wantErr bool
+	}{
+		{
+			name:    "https URL",
+			urlStr:  "https://example.com/path",
+			want:    "example.com",
+			wantErr: false,
+		},
+		{
+			name:    "http URL",
+			urlStr:  "http://test.example.com:8080/path",
+			want:    "test.example.com:8080",
+			wantErr: false,
+		},
+		{
+			name:    "URL with port",
+			urlStr:  "https://log.example.com:9090/monitor",
+			want:    "log.example.com:9090",
+			wantErr: false,
+		},
+		{
+			name:    "invalid URL",
+			urlStr:  "://invalid-url",
+			want:    "",
+			wantErr: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := extractHostname(tt.urlStr)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("extractHostname() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if got != tt.want {
+				t.Errorf("extractHostname() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestExtractPort(t *testing.T) {
+	tests := []struct {
+		name       string
+		listenAddr string
+		want       string
+	}{
+		{
+			name:       "port only",
+			listenAddr: ":8080",
+			want:       "8080",
+		},
+		{
+			name:       "localhost with port",
+			listenAddr: "localhost:9090",
+			want:       "9090",
+		},
+		{
+			name:       "IPv6 with port",
+			listenAddr: "[::]:8080",
+			want:       "8080",
+		},
+		{
+			name:       "no port",
+			listenAddr: "localhost",
+			want:       "",
+		},
+		{
+			name:       "empty string",
+			listenAddr: "",
+			want:       "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := extractPort(tt.listenAddr)
+			if got != tt.want {
+				t.Errorf("extractPort() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestColorizeUnifiedDiff(t *testing.T) {
+	diff := `--- file1.txt
++++ file2.txt
+@@ -1,3 +1,3 @@
+ line1
+-old line
++new line
+ line3`
+
+	result := colorizeUnifiedDiff(diff)
+
+	if !strings.Contains(result, colorCyan) {
+		t.Error("Expected diff to contain cyan color codes")
+	}
+	if !strings.Contains(result, colorYellow) {
+		t.Error("Expected diff to contain yellow color codes")
+	}
+	if !strings.Contains(result, colorRed) {
+		t.Error("Expected diff to contain red color codes")
+	}
+	if !strings.Contains(result, colorGreen) {
+		t.Error("Expected diff to contain green color codes")
+	}
+	if !strings.Contains(result, colorReset) {
+		t.Error("Expected diff to contain reset color codes")
+	}
+}
+
+func TestWriteFileWithStatus(t *testing.T) {
+	tmpDir := t.TempDir()
+	testFile := tmpDir + "/test.txt"
+	content := []byte("test content")
+
+	err := writeFileWithStatus(testFile, content, false, true, false)
+	if err != nil {
+		t.Errorf("writeFileWithStatus() error = %v", err)
+	}
+
+	writtenContent, err := os.ReadFile(testFile)
+	if err != nil {
+		t.Fatalf("Failed to read written file: %v", err)
+	}
+
+	if string(writtenContent) != string(content) {
+		t.Errorf("Written content = %s, want %s", string(writtenContent), string(content))
+	}
+
+	err = writeFileWithStatus(testFile, content, false, false, false)
+	if err != nil {
+		t.Errorf("writeFileWithStatus() with allowWrite=false should not error: %v", err)
+	}
+}
+
+func TestTimeFormats(t *testing.T) {
+	testTime := time.Date(2024, 1, 1, 12, 0, 0, 0, time.UTC)
+	expected := "2024-01-01T12:00:00Z"
+
+	formatted := testTime.Format("2006-01-02T15:04:05Z")
+	if formatted != expected {
+		t.Errorf("Time format = %s, want %s", formatted, expected)
+	}
+}

tesseract/genconf/nginx.go

@@ -70,13 +70,14 @@ const nginxTemplate = `server {
 }
 `
 
+// NginxTemplateData contains the data needed to generate nginx configuration files
 type NginxTemplateData struct {
 	MonitoringHost string
 	LocalDirectory string
 	ListenPort     string
 }
 
-func generateNginx(yamlFile string) {
+func generateNginx(yamlFile string, wantDiff bool, allowWrite bool, useColor bool) {
 	config := loadConfig(yamlFile)
 
 	// Extract port from first listen address
@@ -123,7 +124,7 @@ func generateNginx(yamlFile string) {
 		}
 
 		// Write file with status
-		err = writeFileWithStatus(outputPath, buf.Bytes())
+		err = writeFileWithStatus(outputPath, buf.Bytes(), wantDiff, allowWrite, useColor)
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "Failed to write nginx config file %s: %v\n", outputPath, err)
 			continue
@@ -151,14 +152,10 @@ func extractPort(listenAddr string) string {
 }
 
 func extractHostname(urlStr string) (string, error) {
-	if !strings.HasPrefix(urlStr, "http://") && !strings.HasPrefix(urlStr, "https://") {
-		urlStr = "https://" + urlStr
-	}
-
 	parsedURL, err := url.Parse(urlStr)
 	if err != nil {
 		return "", err
 	}
 
-	return parsedURL.Hostname(), nil
+	return parsedURL.Host, nil
 }

tesseract/genconf/nginx_test.go

@@ -0,0 +1,307 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestGenerateNginx(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	// Create test directories
+	log1Dir := filepath.Join(tmpDir, "log1")
+	log2Dir := filepath.Join(tmpDir, "log2")
+	err := os.MkdirAll(log1Dir, 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = os.MkdirAll(log2Dir, 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Create test config
+	configContent := `listen:
+  - ":8080"
+logs:
+  - shortname: "log1"
+    monitoringprefix: "https://log1.example.com/monitor"
+    localdirectory: "` + log1Dir + `"
+  - shortname: "log2"  
+    monitoringprefix: "https://log2.example.com:9090/monitor"
+    localdirectory: "` + log2Dir + `"`
+
+	configFile := filepath.Join(tmpDir, "test-config.yaml")
+	err = os.WriteFile(configFile, []byte(configContent), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Run generateNginx
+	generateNginx(configFile, false, true, false)
+
+	// Verify nginx config for first log
+	nginxFile1 := filepath.Join(log1Dir, "log1.example.com.conf")
+	nginxContent1, err := os.ReadFile(nginxFile1)
+	if err != nil {
+		t.Fatalf("Failed to read nginx config: %v", err)
+	}
+
+	nginx1Str := string(nginxContent1)
+
+	// Check server block basics
+	if !strings.Contains(nginx1Str, "server {") {
+		t.Error("Expected server block")
+	}
+	if !strings.Contains(nginx1Str, "listen 8080;") {
+		t.Error("Expected listen directive with port 8080")
+	}
+	if !strings.Contains(nginx1Str, "listen [::]:8080;") {
+		t.Error("Expected IPv6 listen directive")
+	}
+	if !strings.Contains(nginx1Str, "server_name log1.example.com;") {
+		t.Error("Expected correct server name")
+	}
+	if !strings.Contains(nginx1Str, "root "+log1Dir+";") {
+		t.Error("Expected correct document root")
+	}
+
+	// Check location blocks
+	if !strings.Contains(nginx1Str, "location = / {") {
+		t.Error("Expected root location block")
+	}
+	if !strings.Contains(nginx1Str, "location = /checkpoint {") {
+		t.Error("Expected checkpoint location block")
+	}
+	if !strings.Contains(nginx1Str, "location = /log.v3.json {") {
+		t.Error("Expected log.v3.json location block")
+	}
+	if !strings.Contains(nginx1Str, "location ~ ^/issuer/(.+)$ {") {
+		t.Error("Expected issuer location block")
+	}
+	if !strings.Contains(nginx1Str, "location ~ ^/tile/(.+)$ {") {
+		t.Error("Expected tile location block")
+	}
+
+	// Check CORS headers
+	if !strings.Contains(nginx1Str, `add_header Access-Control-Allow-Origin "*" always;`) {
+		t.Error("Expected CORS headers")
+	}
+
+	// Check cache control headers
+	if !strings.Contains(nginx1Str, `add_header Cache-Control "no-store" always;`) {
+		t.Error("Expected no-store cache control for checkpoint")
+	}
+	if !strings.Contains(nginx1Str, `add_header Cache-Control "public, max-age=3600, immutable" always;`) {
+		t.Error("Expected long cache control for log.v3.json")
+	}
+	if !strings.Contains(nginx1Str, `add_header Cache-Control "public, max-age=604800, immutable" always;`) {
+		t.Error("Expected very long cache control for static files")
+	}
+
+	// Check content types
+	if !strings.Contains(nginx1Str, `add_header Content-Type "text/html; charset=utf-8" always;`) {
+		t.Error("Expected HTML content type")
+	}
+	if !strings.Contains(nginx1Str, `add_header Content-Type "text/plain; charset=utf-8" always;`) {
+		t.Error("Expected plain text content type for checkpoint")
+	}
+	if !strings.Contains(nginx1Str, `add_header Content-Type "application/json" always;`) {
+		t.Error("Expected JSON content type")
+	}
+	if !strings.Contains(nginx1Str, `add_header Content-Type "application/pkix-cert" always;`) {
+		t.Error("Expected certificate content type")
+	}
+	if !strings.Contains(nginx1Str, `add_header Content-Type "application/octet-stream" always;`) {
+		t.Error("Expected octet-stream content type")
+	}
+
+	// Check gzip handling
+	if !strings.Contains(nginx1Str, `add_header Content-Encoding "gzip" always;`) {
+		t.Error("Expected gzip content encoding for .gz files")
+	}
+
+	// Verify nginx config for second log (with port)
+	nginxFile2 := filepath.Join(log2Dir, "log2.example.com:9090.conf")
+	nginxContent2, err := os.ReadFile(nginxFile2)
+	if err != nil {
+		t.Fatalf("Failed to read second nginx config: %v", err)
+	}
+
+	nginx2Str := string(nginxContent2)
+	if !strings.Contains(nginx2Str, "server_name log2.example.com:9090;") {
+		t.Error("Expected correct server name with port")
+	}
+	if !strings.Contains(nginx2Str, "root "+log2Dir+";") {
+		t.Error("Expected correct document root for second log")
+	}
+}
+
+func TestGenerateNginxCustomPort(t *testing.T) {
+	tmpDir := t.TempDir()
+	logDir := filepath.Join(tmpDir, "test-log")
+	err := os.MkdirAll(logDir, 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Create config with custom port
+	configContent := `listen:
+  - ":9999"
+logs:
+  - shortname: "test-log"
+    monitoringprefix: "https://test.example.com/monitor"
+    localdirectory: "` + logDir + `"`
+
+	configFile := filepath.Join(tmpDir, "test-config.yaml")
+	err = os.WriteFile(configFile, []byte(configContent), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	generateNginx(configFile, false, true, false)
+
+	nginxFile := filepath.Join(logDir, "test.example.com.conf")
+	nginxContent, err := os.ReadFile(nginxFile)
+	if err != nil {
+		t.Fatalf("Failed to read nginx config: %v", err)
+	}
+
+	nginxStr := string(nginxContent)
+	if !strings.Contains(nginxStr, "listen 9999;") {
+		t.Error("Expected listen directive with custom port 9999")
+	}
+	if !strings.Contains(nginxStr, "listen [::]:9999;") {
+		t.Error("Expected IPv6 listen directive with custom port")
+	}
+}
+
+func TestGenerateNginxMultiplePorts(t *testing.T) {
+	tmpDir := t.TempDir()
+	logDir := filepath.Join(tmpDir, "test-log")
+	err := os.MkdirAll(logDir, 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Create config with multiple listen addresses (should use first one)
+	configContent := `listen:
+  - ":8080"
+  - ":8081"  
+logs:
+  - shortname: "test-log"
+    monitoringprefix: "https://test.example.com/monitor"
+    localdirectory: "` + logDir + `"`
+
+	configFile := filepath.Join(tmpDir, "test-config.yaml")
+	err = os.WriteFile(configFile, []byte(configContent), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	generateNginx(configFile, false, true, false)
+
+	nginxFile := filepath.Join(logDir, "test.example.com.conf")
+	nginxContent, err := os.ReadFile(nginxFile)
+	if err != nil {
+		t.Fatalf("Failed to read nginx config: %v", err)
+	}
+
+	nginxStr := string(nginxContent)
+	if !strings.Contains(nginxStr, "listen 8080;") {
+		t.Error("Expected first port to be used")
+	}
+	if strings.Contains(nginxStr, "listen 8081;") {
+		t.Error("Should not contain second port")
+	}
+}
+
+func TestGenerateNginxInvalidURL(t *testing.T) {
+	tmpDir := t.TempDir()
+	logDir := filepath.Join(tmpDir, "test-log")
+	err := os.MkdirAll(logDir, 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Create config with invalid monitoring URL
+	configContent := `logs:
+  - shortname: "test-log"
+    monitoringprefix: "not-a-valid-url"
+    localdirectory: "` + logDir + `"`
+
+	configFile := filepath.Join(tmpDir, "test-config.yaml")
+	err = os.WriteFile(configFile, []byte(configContent), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Should not create nginx config file due to invalid URL
+	generateNginx(configFile, false, true, false)
+
+	// Check that a .conf file was still created (even with invalid hostname extraction)
+	// The function continues execution and creates a file with empty hostname
+	files, err := filepath.Glob(filepath.Join(logDir, "*.conf"))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// The function still creates a file, but with an empty hostname, resulting in ".conf"
+	if len(files) == 0 {
+		t.Error("Expected at least one config file to be created despite invalid URL")
+	}
+}
+
+func TestNginxTemplateData(t *testing.T) {
+	data := NginxTemplateData{
+		MonitoringHost: "example.com",
+		LocalDirectory: "/path/to/files",
+		ListenPort:     "8080",
+	}
+
+	if data.MonitoringHost != "example.com" {
+		t.Errorf("Expected MonitoringHost 'example.com', got %s", data.MonitoringHost)
+	}
+	if data.LocalDirectory != "/path/to/files" {
+		t.Errorf("Expected LocalDirectory '/path/to/files', got %s", data.LocalDirectory)
+	}
+	if data.ListenPort != "8080" {
+		t.Errorf("Expected ListenPort '8080', got %s", data.ListenPort)
+	}
+}
+
+func TestGenerateNginxNoListenConfig(t *testing.T) {
+	tmpDir := t.TempDir()
+	logDir := filepath.Join(tmpDir, "test-log")
+	err := os.MkdirAll(logDir, 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Create config without listen directive (should use default 8080)
+	configContent := `logs:
+  - shortname: "test-log"
+    monitoringprefix: "https://test.example.com/monitor"
+    localdirectory: "` + logDir + `"`
+
+	configFile := filepath.Join(tmpDir, "test-config.yaml")
+	err = os.WriteFile(configFile, []byte(configContent), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	generateNginx(configFile, false, true, false)
+
+	nginxFile := filepath.Join(logDir, "test.example.com.conf")
+	nginxContent, err := os.ReadFile(nginxFile)
+	if err != nil {
+		t.Fatalf("Failed to read nginx config: %v", err)
+	}
+
+	nginxStr := string(nginxContent)
+	if !strings.Contains(nginxStr, "listen 8080;") {
+		t.Error("Expected default port 8080 when no listen config provided")
+	}
+}

tesseract/genconf/roots.go

@@ -12,11 +12,12 @@ import (
 	"strings"
 )
 
+// CTLogRootsResponse represents the JSON response from a CT log's get-roots endpoint
 type CTLogRootsResponse struct {
 	Certificates []string `json:"certificates"`
 }
 
-func generateRoots(args []string) {
+func generateRoots(args []string, wantDiff bool, allowWrite bool, useColor bool) {
 	sourceURL := "https://rennet2027h2.log.ct.ipng.ch/"
 	outputFile := "roots.pem"
 
@@ -107,7 +108,7 @@ func generateRoots(args []string) {
 	}
 
 	// Write all certificates to file with status
-	err = writeFileWithStatus(outputFile, pemBuffer.Bytes())
+	err = writeFileWithStatus(outputFile, pemBuffer.Bytes(), wantDiff, allowWrite, useColor)
 	if err != nil {
 		log.Fatalf("Failed to write output file %s: %v", outputFile, err)
 	}

tesseract/genconf/roots_test.go

@@ -0,0 +1,217 @@
+package main
+
+import (
+	"encoding/json"
+	"encoding/pem"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestGenerateRoots(t *testing.T) {
+	tmpDir := t.TempDir()
+	outputFile := filepath.Join(tmpDir, "test-roots.pem")
+
+	// Create a test HTTP server that returns mock root certificates
+	mockResponse := CTLogRootsResponse{
+		Certificates: []string{
+			// Real certificate (base64 encoded DER from OpenSSL)
+			"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",
+			// Second certificate (same but different serial for testing)
+			"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",
+		},
+	}
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if !strings.HasSuffix(r.URL.Path, "/ct/v1/get-roots") {
+			t.Errorf("Expected path to end with /ct/v1/get-roots, got %s", r.URL.Path)
+		}
+
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(mockResponse)
+	}))
+	defer server.Close()
+
+	// Test with default arguments
+	args := []string{"--source", server.URL, "--output", outputFile}
+	generateRoots(args, false, true, false)
+
+	// Verify output file was created
+	if _, err := os.Stat(outputFile); os.IsNotExist(err) {
+		t.Fatal("Output file was not created")
+	}
+
+	// Verify file contents
+	content, err := os.ReadFile(outputFile)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	contentStr := string(content)
+
+	// Should contain PEM headers
+	if !strings.Contains(contentStr, "-----BEGIN CERTIFICATE-----") {
+		t.Error("Expected PEM certificate headers")
+	}
+	if !strings.Contains(contentStr, "-----END CERTIFICATE-----") {
+		t.Error("Expected PEM certificate footers")
+	}
+
+	// Count certificates (should have 2)
+	certCount := strings.Count(contentStr, "-----BEGIN CERTIFICATE-----")
+	if certCount != 2 {
+		t.Errorf("Expected 2 certificates, found %d", certCount)
+	}
+}
+
+func TestGenerateRootsWithNegativeSerial(t *testing.T) {
+	// Should call log.Fatalf due to invalid base64
+	// Can't easily test this without subprocess, so we'll skip it
+	t.Skip("Cannot easily test log.Fatalf without subprocess")
+}
+
+func TestGenerateRootsHTTPError(t *testing.T) {
+	// Should call log.Fatalf due to HTTP error
+	// Can't easily test this without subprocess, so we'll skip it
+	t.Skip("Cannot easily test log.Fatalf without subprocess")
+}
+
+func TestGenerateRootsInvalidJSON(t *testing.T) {
+	// Should call log.Fatalf due to JSON parse error
+	// Can't easily test this without subprocess, so we'll skip it
+	t.Skip("Cannot easily test log.Fatalf without subprocess")
+}
+
+func TestGenerateRootsArgumentParsing(t *testing.T) {
+	tmpDir := t.TempDir()
+	customOutputFile := filepath.Join(tmpDir, "custom-roots.pem")
+
+	mockResponse := CTLogRootsResponse{
+		Certificates: []string{
+			"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",
+		},
+	}
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(mockResponse)
+	}))
+	defer server.Close()
+
+	// Test custom source and output
+	args := []string{"--source", server.URL, "--output", customOutputFile}
+	generateRoots(args, false, true, false)
+
+	// Verify custom output file was created
+	if _, err := os.Stat(customOutputFile); os.IsNotExist(err) {
+		t.Error("Custom output file was not created")
+	}
+}
+
+func TestGenerateRootsMissingSourceArgument(t *testing.T) {
+	// Should call log.Fatal due to missing source URL argument
+	// Can't easily test this without subprocess, so we'll skip it
+	t.Skip("Cannot easily test log.Fatal without subprocess")
+}
+
+func TestGenerateRootsMissingOutputArgument(t *testing.T) {
+	// Should call log.Fatal due to missing output filename argument
+	// Can't easily test this without subprocess, so we'll skip it
+	t.Skip("Cannot easily test log.Fatal without subprocess")
+}
+
+func TestGenerateRootsUnknownArgument(t *testing.T) {
+	// Should call log.Fatalf due to unknown argument
+	// Can't easily test this without subprocess, so we'll skip it
+	t.Skip("Cannot easily test log.Fatalf without subprocess")
+}
+
+func TestGenerateRootsDefaultArguments(t *testing.T) {
+	// Test that default arguments are used correctly
+	// This test would normally make a real HTTP request, so we'll skip it
+	// unless we're doing integration tests
+	t.Skip("Skipping test that would make real HTTP request")
+}
+
+func TestGenerateRootsSourceURLFormatting(t *testing.T) {
+	tmpDir := t.TempDir()
+	outputFile := filepath.Join(tmpDir, "test-roots.pem")
+
+	mockResponse := CTLogRootsResponse{
+		Certificates: []string{
+			"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",
+		},
+	}
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		// Verify the path formatting
+		expectedPath := "/ct/v1/get-roots"
+		if r.URL.Path != expectedPath {
+			t.Errorf("Expected path %s, got %s", expectedPath, r.URL.Path)
+		}
+
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(mockResponse)
+	}))
+	defer server.Close()
+
+	// Test with URL that doesn't end with /
+	sourceURL := strings.TrimSuffix(server.URL, "/")
+	args := []string{"--source", sourceURL, "--output", outputFile}
+	generateRoots(args, false, true, false)
+
+	// Should still work (the function adds trailing slash)
+	if _, err := os.Stat(outputFile); os.IsNotExist(err) {
+		t.Error("Output file was not created when source URL lacks trailing slash")
+	}
+}
+
+func TestPEMEncoding(t *testing.T) {
+	tmpDir := t.TempDir()
+	outputFile := filepath.Join(tmpDir, "test-roots.pem")
+
+	mockResponse := CTLogRootsResponse{
+		Certificates: []string{
+			"MIIDFzCCAf+gAwIBAgIUbOZ5dIVBuGei8T0VdIKjCpACVgMwDQYJKoZIhvcNAQELBQAwGzEZMBcGA1UEAwwQVGVzdCBDZXJ0aWZpY2F0ZTAeFw0yNTA4MjgxOTA4MjlaFw0yNjA4MjgxOTA4MjlaMBsxGTAXBgNVBAMMEFRlc3QgQ2VydGlmaWNhdGUwggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQDEmF+JcVMD9u0efdi8AkIH4xiKb/8lJveOYu5UKJ/hE7j+QN0HcK+3d0Fh83Hgny7ZgF3A8JlTDnlZrkI1+n8uxLAbvZ/PVNS286FwlnWppnarSBwFMuHp+SoGFuNIQtB5LaxVt943Oxaw4vVaFBqi0iYPFKXj2JxLIwiwKxLiZ2hS15g/JIhRXSycHjMCvukPj1wtRo/cHF83Miydw+ngFqrfXcEzvG/Yx5qvAgowvG/FEKha5zB36ywy35SHq8gX7DHs77eQ52lxd4yvYfPhIwaAzTvnpyACcvfgP/XiETMxsaPoZ3WFzK4y3Smg6zUMLAB1YE4RxUd+4NA+NBmbAgMBAAGjUzBRMB0GA1UdDgQWBBQxgJBg/4o2f1e58aBMOlyEO0svIDAfBgNVHSMEGDAWgBQxgJBg/4o2f1e58aBMOlyEO0svIDAPBgNVHRMBAf8EBTADAQH/MA0GCSqGSIb3DQEBCwUAA4IBAQA1Z1r8pJeYizgo30kA+Q4SICq70jvAO6XPrin2hp8MlvE7nUG2afInzNh6FXjqMI0TWctqV+wF9nnCkPBPu4ybCbm7reiJ1SojPmp/qxv+qoyXXFZxX/ugOhhJv4BbSoHxepdSPBtqQb5uZPL/1q9vYmLfsEdEdh1dI4vEbrvvZR/fV/5+ZjL2uOuWf6zw0BpMqXyC0wcoZIWKHl62yLOhdJwbUVLfKiHuwrhsdIIc0QDI74U6x5pu/eIa1hCPX9e/X8vEK8/0EBV2xGhAeeteu4bY04AjrSs0tESQO5EfACmhQM/1ytlqMx3qsPGb7pIptUttHREvr+RL6qKCRZCK",
+		},
+	}
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(mockResponse)
+	}))
+	defer server.Close()
+
+	args := []string{"--source", server.URL, "--output", outputFile}
+	generateRoots(args, false, true, false)
+
+	// Read and verify PEM structure
+	content, err := os.ReadFile(outputFile)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Parse PEM blocks
+	var certCount int
+	remaining := content
+	for len(remaining) > 0 {
+		block, rest := pem.Decode(remaining)
+		if block == nil {
+			break
+		}
+
+		if block.Type != "CERTIFICATE" {
+			t.Errorf("Expected block type 'CERTIFICATE', got %s", block.Type)
+		}
+
+		certCount++
+		remaining = rest
+	}
+
+	if certCount != 1 {
+		t.Errorf("Expected 1 certificate, found %d", certCount)
+	}
+}