CHANGELOG: bump to v1.13.2.

.gitignore

@@ -1 +1,2 @@
 .idea
+cmd/cert-bundler/testdata/pkg/*

.golangci.yml

@@ -390,6 +390,9 @@ linters:
         - 3
         - 4
         - 8
+        - 24
+        - 30
+        - 365
 
     nakedret:
       # Make an issue if func has more lines of code than this setting, and it has naked returns.

CHANGELOG

@@ -1,5 +1,26 @@
 CHANGELOG
 
+v1.13.2 - 2025-11-17
+
+Add:
+- certlib/bundler: refactor certificate bundling from cmd/cert-bundler
+  into a separate package.
+
+Changed:
+- cmd/cert-bundler: refactor to use bundler package, and update Dockerfile.
+
+v1.13.1 - 2025-11-17
+
+Add:
+- Dockerfile for cert-bundler.
+
+v1.13.0 - 2025-11-16
+
+Add:
+- cmd/certser: print serial numbers for certificates.
+- lib/HexEncode: add a new hex encode function handling multiple output
+  formats, including with and without colons.
+
 v1.12.4 - 2025-11-16
 
 Changed:

certlib/bundler/bundler.go

@@ -0,0 +1,668 @@
+package bundler
+
+import (
+	"archive/tar"
+	"archive/zip"
+	"compress/gzip"
+	"crypto/sha256"
+	"crypto/x509"
+	"encoding/pem"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"gopkg.in/yaml.v2"
+
+	"git.wntrmute.dev/kyle/goutils/certlib"
+)
+
+const defaultFileMode = 0644
+
+// Config represents the top-level YAML configuration.
+type Config struct {
+	Config struct {
+		Hashes string `yaml:"hashes"`
+		Expiry string `yaml:"expiry"`
+	} `yaml:"config"`
+	Chains map[string]ChainGroup `yaml:"chains"`
+}
+
+// ChainGroup represents a named group of certificate chains.
+type ChainGroup struct {
+	Certs   []CertChain `yaml:"certs"`
+	Outputs Outputs     `yaml:"outputs"`
+}
+
+// CertChain represents a root certificate and its intermediates.
+type CertChain struct {
+	Root          string   `yaml:"root"`
+	Intermediates []string `yaml:"intermediates"`
+}
+
+// Outputs defines output format options.
+type Outputs struct {
+	IncludeSingle     bool     `yaml:"include_single"`
+	IncludeIndividual bool     `yaml:"include_individual"`
+	Manifest          bool     `yaml:"manifest"`
+	Formats           []string `yaml:"formats"`
+	Encoding          string   `yaml:"encoding"`
+}
+
+var formatExtensions = map[string]string{
+	"zip": ".zip",
+	"tgz": ".tar.gz",
+}
+
+// Run performs the bundling operation given a config file path and an output directory.
+func Run(configFile string, outputDir string) error {
+	if configFile == "" {
+		return errors.New("configuration file required")
+	}
+
+	cfg, err := loadConfig(configFile)
+	if err != nil {
+		return fmt.Errorf("loading config: %w", err)
+	}
+
+	expiryDuration := 365 * 24 * time.Hour
+	if cfg.Config.Expiry != "" {
+		expiryDuration, err = parseDuration(cfg.Config.Expiry)
+		if err != nil {
+			return fmt.Errorf("parsing expiry: %w", err)
+		}
+	}
+
+	if err = os.MkdirAll(outputDir, 0750); err != nil {
+		return fmt.Errorf("creating output directory: %w", err)
+	}
+
+	totalFormats := 0
+	for _, group := range cfg.Chains {
+		totalFormats += len(group.Outputs.Formats)
+	}
+	createdFiles := make([]string, 0, totalFormats)
+	for groupName, group := range cfg.Chains {
+		files, perr := processChainGroup(groupName, group, expiryDuration, outputDir)
+		if perr != nil {
+			return fmt.Errorf("processing chain group %s: %w", groupName, perr)
+		}
+		createdFiles = append(createdFiles, files...)
+	}
+
+	if cfg.Config.Hashes != "" {
+		hashFile := filepath.Join(outputDir, cfg.Config.Hashes)
+		if gerr := generateHashFile(hashFile, createdFiles); gerr != nil {
+			return fmt.Errorf("generating hash file: %w", gerr)
+		}
+	}
+
+	return nil
+}
+
+func loadConfig(path string) (*Config, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+
+	var cfg Config
+	if uerr := yaml.Unmarshal(data, &cfg); uerr != nil {
+		return nil, uerr
+	}
+
+	return &cfg, nil
+}
+
+func parseDuration(s string) (time.Duration, error) {
+	// Support simple formats like "1y", "6m", "30d"
+	if len(s) < 2 {
+		return 0, fmt.Errorf("invalid duration format: %s", s)
+	}
+
+	unit := s[len(s)-1]
+	value := s[:len(s)-1]
+
+	var multiplier time.Duration
+	switch unit {
+	case 'y', 'Y':
+		multiplier = 365 * 24 * time.Hour
+	case 'm', 'M':
+		multiplier = 30 * 24 * time.Hour
+	case 'd', 'D':
+		multiplier = 24 * time.Hour
+	default:
+		return time.ParseDuration(s)
+	}
+
+	var num int
+	_, err := fmt.Sscanf(value, "%d", &num)
+	if err != nil {
+		return 0, fmt.Errorf("invalid duration value: %s", s)
+	}
+
+	return time.Duration(num) * multiplier, nil
+}
+
+func processChainGroup(
+	groupName string,
+	group ChainGroup,
+	expiryDuration time.Duration,
+	outputDir string,
+) ([]string, error) {
+	// Default encoding to "pem" if not specified
+	encoding := group.Outputs.Encoding
+	if encoding == "" {
+		encoding = "pem"
+	}
+
+	// Collect certificates from all chains in the group
+	singleFileCerts, individualCerts, sourcePaths, err := loadAndCollectCerts(
+		group.Certs,
+		group.Outputs,
+		expiryDuration,
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	// Prepare files for inclusion in archives
+	archiveFiles, err := prepareArchiveFiles(singleFileCerts, individualCerts, sourcePaths, group.Outputs, encoding)
+	if err != nil {
+		return nil, err
+	}
+
+	// Create archives for the entire group
+	createdFiles, err := createArchiveFiles(groupName, group.Outputs.Formats, archiveFiles, outputDir)
+	if err != nil {
+		return nil, err
+	}
+
+	return createdFiles, nil
+}
+
+// loadAndCollectCerts loads all certificates from chains and collects them for processing.
+func loadAndCollectCerts(
+	chains []CertChain,
+	outputs Outputs,
+	expiryDuration time.Duration,
+) ([]*x509.Certificate, []certWithPath, []string, error) {
+	var singleFileCerts []*x509.Certificate
+	var individualCerts []certWithPath
+	var sourcePaths []string
+
+	for _, chain := range chains {
+		s, i, cerr := collectFromChain(chain, outputs, expiryDuration)
+		if cerr != nil {
+			return nil, nil, nil, cerr
+		}
+		if len(s) > 0 {
+			singleFileCerts = append(singleFileCerts, s...)
+		}
+		if len(i) > 0 {
+			individualCerts = append(individualCerts, i...)
+		}
+		// Record source paths for timestamp preservation
+		// Only append when loading succeeded
+		sourcePaths = append(sourcePaths, chain.Root)
+		sourcePaths = append(sourcePaths, chain.Intermediates...)
+	}
+
+	return singleFileCerts, individualCerts, sourcePaths, nil
+}
+
+// collectFromChain loads a single chain, performs checks, and returns the certs to include.
+func collectFromChain(
+	chain CertChain,
+	outputs Outputs,
+	expiryDuration time.Duration,
+) (
+	[]*x509.Certificate,
+	[]certWithPath,
+	error,
+) {
+	var single []*x509.Certificate
+	var indiv []certWithPath
+
+	// Load root certificate
+	rootCert, rerr := certlib.LoadCertificate(chain.Root)
+	if rerr != nil {
+		return nil, nil, fmt.Errorf("failed to load root certificate %s: %w", chain.Root, rerr)
+	}
+
+	// Check expiry for root
+	checkExpiry(chain.Root, rootCert, expiryDuration)
+
+	// Add root to collections if needed
+	if outputs.IncludeSingle {
+		single = append(single, rootCert)
+	}
+	if outputs.IncludeIndividual {
+		indiv = append(indiv, certWithPath{cert: rootCert, path: chain.Root})
+	}
+
+	// Load and validate intermediates
+	for _, intPath := range chain.Intermediates {
+		intCert, lerr := certlib.LoadCertificate(intPath)
+		if lerr != nil {
+			return nil, nil, fmt.Errorf("failed to load intermediate certificate %s: %w", intPath, lerr)
+		}
+
+		// Validate that intermediate is signed by root
+		if sigErr := intCert.CheckSignatureFrom(rootCert); sigErr != nil {
+			return nil, nil, fmt.Errorf(
+				"intermediate %s is not properly signed by root %s: %w",
+				intPath,
+				chain.Root,
+				sigErr,
+			)
+		}
+
+		// Check expiry for intermediate
+		checkExpiry(intPath, intCert, expiryDuration)
+
+		// Add intermediate to collections if needed
+		if outputs.IncludeSingle {
+			single = append(single, intCert)
+		}
+		if outputs.IncludeIndividual {
+			indiv = append(indiv, certWithPath{cert: intCert, path: intPath})
+		}
+	}
+
+	return single, indiv, nil
+}
+
+// prepareArchiveFiles prepares all files to be included in archives.
+func prepareArchiveFiles(
+	singleFileCerts []*x509.Certificate,
+	individualCerts []certWithPath,
+	sourcePaths []string,
+	outputs Outputs,
+	encoding string,
+) ([]fileEntry, error) {
+	var archiveFiles []fileEntry
+
+	// Track used filenames to avoid collisions inside archives
+	usedNames := make(map[string]int)
+
+	// Handle a single bundle file
+	if outputs.IncludeSingle && len(singleFileCerts) > 0 {
+		bundleTime := maxModTime(sourcePaths)
+		files, err := encodeCertsToFiles(singleFileCerts, "bundle", encoding, true)
+		if err != nil {
+			return nil, fmt.Errorf("failed to encode single bundle: %w", err)
+		}
+		for i := range files {
+			files[i].name = makeUniqueName(files[i].name, usedNames)
+			files[i].modTime = bundleTime
+			// Best-effort: we do not have a portable birth/creation time.
+			// Use the same timestamp for created time to track deterministically.
+			files[i].createTime = bundleTime
+		}
+		archiveFiles = append(archiveFiles, files...)
+	}
+
+	// Handle individual files
+	if outputs.IncludeIndividual {
+		for _, cp := range individualCerts {
+			baseName := strings.TrimSuffix(filepath.Base(cp.path), filepath.Ext(cp.path))
+			files, err := encodeCertsToFiles([]*x509.Certificate{cp.cert}, baseName, encoding, false)
+			if err != nil {
+				return nil, fmt.Errorf("failed to encode individual cert %s: %w", cp.path, err)
+			}
+			mt := fileModTime(cp.path)
+			for i := range files {
+				files[i].name = makeUniqueName(files[i].name, usedNames)
+				files[i].modTime = mt
+				files[i].createTime = mt
+			}
+			archiveFiles = append(archiveFiles, files...)
+		}
+	}
+
+	// Generate manifest if requested
+	if outputs.Manifest {
+		manifestContent := generateManifest(archiveFiles)
+		manifestName := makeUniqueName("MANIFEST", usedNames)
+		mt := maxModTime(sourcePaths)
+		archiveFiles = append(archiveFiles, fileEntry{
+			name:       manifestName,
+			content:    manifestContent,
+			modTime:    mt,
+			createTime: mt,
+		})
+	}
+
+	return archiveFiles, nil
+}
+
+// createArchiveFiles creates archive files in the specified formats.
+func createArchiveFiles(
+	groupName string,
+	formats []string,
+	archiveFiles []fileEntry,
+	outputDir string,
+) ([]string, error) {
+	createdFiles := make([]string, 0, len(formats))
+
+	for _, format := range formats {
+		ext, ok := formatExtensions[format]
+		if !ok {
+			return nil, fmt.Errorf("unsupported format: %s", format)
+		}
+		archivePath := filepath.Join(outputDir, groupName+ext)
+		switch format {
+		case "zip":
+			if err := createZipArchive(archivePath, archiveFiles); err != nil {
+				return nil, fmt.Errorf("failed to create zip archive: %w", err)
+			}
+		case "tgz":
+			if err := createTarGzArchive(archivePath, archiveFiles); err != nil {
+				return nil, fmt.Errorf("failed to create tar.gz archive: %w", err)
+			}
+		default:
+			return nil, fmt.Errorf("unsupported format: %s", format)
+		}
+		createdFiles = append(createdFiles, archivePath)
+	}
+
+	return createdFiles, nil
+}
+
+func checkExpiry(path string, cert *x509.Certificate, expiryDuration time.Duration) {
+	now := time.Now()
+	expiryThreshold := now.Add(expiryDuration)
+
+	if cert.NotAfter.Before(expiryThreshold) {
+		daysUntilExpiry := int(cert.NotAfter.Sub(now).Hours() / 24)
+		if daysUntilExpiry < 0 {
+			fmt.Fprintf(
+				os.Stderr,
+				"WARNING: Certificate %s has EXPIRED (expired %d days ago)\n",
+				path,
+				-daysUntilExpiry,
+			)
+		} else {
+			fmt.Fprintf(os.Stderr, "WARNING: Certificate %s will expire in %d days (on %s)\n", path, daysUntilExpiry, cert.NotAfter.Format("2006-01-02"))
+		}
+	}
+}
+
+type fileEntry struct {
+	name       string
+	content    []byte
+	modTime    time.Time
+	createTime time.Time
+}
+
+type certWithPath struct {
+	cert *x509.Certificate
+	path string
+}
+
+// encodeCertsToFiles converts certificates to file entries based on encoding type
+// If isSingle is true, certs are concatenated into a single file; otherwise one cert per file.
+func encodeCertsToFiles(
+	certs []*x509.Certificate,
+	baseName string,
+	encoding string,
+	isSingle bool,
+) ([]fileEntry, error) {
+	var files []fileEntry
+
+	switch encoding {
+	case "pem":
+		pemContent := encodeCertsToPEM(certs)
+		files = append(files, fileEntry{
+			name:    baseName + ".pem",
+			content: pemContent,
+		})
+	case "der":
+		if isSingle {
+			// For single file in DER, concatenate all cert DER bytes
+			var derContent []byte
+			for _, cert := range certs {
+				derContent = append(derContent, cert.Raw...)
+			}
+			files = append(files, fileEntry{
+				name:    baseName + ".crt",
+				content: derContent,
+			})
+		} else if len(certs) > 0 {
+			// Individual DER file (should only have one cert)
+			files = append(files, fileEntry{
+				name:    baseName + ".crt",
+				content: certs[0].Raw,
+			})
+		}
+	case "both":
+		// Add PEM version
+		pemContent := encodeCertsToPEM(certs)
+		files = append(files, fileEntry{
+			name:    baseName + ".pem",
+			content: pemContent,
+		})
+		// Add DER version
+		if isSingle {
+			var derContent []byte
+			for _, cert := range certs {
+				derContent = append(derContent, cert.Raw...)
+			}
+			files = append(files, fileEntry{
+				name:    baseName + ".crt",
+				content: derContent,
+			})
+		} else if len(certs) > 0 {
+			files = append(files, fileEntry{
+				name:    baseName + ".crt",
+				content: certs[0].Raw,
+			})
+		}
+	default:
+		return nil, fmt.Errorf("unsupported encoding: %s (must be 'pem', 'der', or 'both')", encoding)
+	}
+
+	return files, nil
+}
+
+// encodeCertsToPEM encodes certificates to PEM format.
+func encodeCertsToPEM(certs []*x509.Certificate) []byte {
+	var pemContent []byte
+	for _, cert := range certs {
+		pemBlock := &pem.Block{
+			Type:  "CERTIFICATE",
+			Bytes: cert.Raw,
+		}
+		pemContent = append(pemContent, pem.EncodeToMemory(pemBlock)...)
+	}
+	return pemContent
+}
+
+func generateManifest(files []fileEntry) []byte {
+	var manifest strings.Builder
+	for _, file := range files {
+		if file.name == "MANIFEST" {
+			continue
+		}
+		hash := sha256.Sum256(file.content)
+		manifest.WriteString(fmt.Sprintf("%x  %s\n", hash, file.name))
+	}
+	return []byte(manifest.String())
+}
+
+// closeWithErr attempts to close all provided closers, joining any close errors with baseErr.
+func closeWithErr(baseErr error, closers ...io.Closer) error {
+	for _, c := range closers {
+		if c == nil {
+			continue
+		}
+		if cerr := c.Close(); cerr != nil {
+			baseErr = errors.Join(baseErr, cerr)
+		}
+	}
+	return baseErr
+}
+
+func createZipArchive(path string, files []fileEntry) error {
+	f, zerr := os.Create(path)
+	if zerr != nil {
+		return zerr
+	}
+
+	w := zip.NewWriter(f)
+
+	for _, file := range files {
+		hdr := &zip.FileHeader{
+			Name:   file.name,
+			Method: zip.Deflate,
+		}
+		if !file.modTime.IsZero() {
+			hdr.SetModTime(file.modTime)
+		}
+		fw, werr := w.CreateHeader(hdr)
+		if werr != nil {
+			return closeWithErr(werr, w, f)
+		}
+		if _, werr = fw.Write(file.content); werr != nil {
+			return closeWithErr(werr, w, f)
+		}
+	}
+
+	// Check errors on close operations
+	if cerr := w.Close(); cerr != nil {
+		_ = f.Close()
+		return cerr
+	}
+	return f.Close()
+}
+
+func createTarGzArchive(path string, files []fileEntry) error {
+	f, terr := os.Create(path)
+	if terr != nil {
+		return terr
+	}
+
+	gw := gzip.NewWriter(f)
+	tw := tar.NewWriter(gw)
+
+	for _, file := range files {
+		hdr := &tar.Header{
+			Name: file.name,
+			Uid:  0,
+			Gid:  0,
+			Mode: defaultFileMode,
+			Size: int64(len(file.content)),
+			ModTime: func() time.Time {
+				if file.modTime.IsZero() {
+					return time.Now()
+				}
+				return file.modTime
+			}(),
+		}
+		// Set additional times if supported
+		hdr.AccessTime = hdr.ModTime
+		if !file.createTime.IsZero() {
+			hdr.ChangeTime = file.createTime
+		} else {
+			hdr.ChangeTime = hdr.ModTime
+		}
+		if herr := tw.WriteHeader(hdr); herr != nil {
+			return closeWithErr(herr, tw, gw, f)
+		}
+		if _, werr := tw.Write(file.content); werr != nil {
+			return closeWithErr(werr, tw, gw, f)
+		}
+	}
+
+	// Check errors on close operations in the correct order
+	if cerr := tw.Close(); cerr != nil {
+		_ = gw.Close()
+		_ = f.Close()
+		return cerr
+	}
+	if cerr := gw.Close(); cerr != nil {
+		_ = f.Close()
+		return cerr
+	}
+	return f.Close()
+}
+
+func generateHashFile(path string, files []string) error {
+	f, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	for _, file := range files {
+		data, rerr := os.ReadFile(file)
+		if rerr != nil {
+			return rerr
+		}
+
+		hash := sha256.Sum256(data)
+		fmt.Fprintf(f, "%x  %s\n", hash, filepath.Base(file))
+	}
+
+	return nil
+}
+
+// makeUniqueName ensures that each file name within the archive is unique by appending
+// an incremental numeric suffix before the extension when collisions occur.
+// Example: "root.pem" -> "root-2.pem", "root-3.pem", etc.
+func makeUniqueName(name string, used map[string]int) string {
+	// If unused, mark and return as-is
+	if _, ok := used[name]; !ok {
+		used[name] = 1
+		return name
+	}
+
+	ext := filepath.Ext(name)
+	base := strings.TrimSuffix(name, ext)
+	// Track a counter per base+ext key
+	key := base + ext
+	counter := max(used[key], 1)
+	for {
+		counter++
+		candidate := fmt.Sprintf("%s-%d%s", base, counter, ext)
+		if _, exists := used[candidate]; !exists {
+			used[key] = counter
+			used[candidate] = 1
+			return candidate
+		}
+	}
+}
+
+// fileModTime returns the file's modification time, or time.Now() if stat fails.
+func fileModTime(path string) time.Time {
+	fi, err := os.Stat(path)
+	if err != nil {
+		return time.Now()
+	}
+	return fi.ModTime()
+}
+
+// maxModTime returns the latest modification time across provided paths.
+// If the list is empty or stats fail, returns time.Now().
+func maxModTime(paths []string) time.Time {
+	var zero time.Time
+	maxTime := zero
+	for _, p := range paths {
+		fi, err := os.Stat(p)
+		if err != nil {
+			continue
+		}
+		mt := fi.ModTime()
+		if maxTime.IsZero() || mt.After(maxTime) {
+			maxTime = mt
+		}
+	}
+	if maxTime.IsZero() {
+		return time.Now()
+	}
+	return maxTime
+}

cmd/cert-bundler/Dockerfile

@@ -0,0 +1,28 @@
+# Build and runtime image for cert-bundler
+# Usage (from repo root or cmd/cert-bundler directory):
+#   docker build -t cert-bundler:latest -f cmd/cert-bundler/Dockerfile .
+#   docker run --rm -v "$PWD":/work cert-bundler:latest
+# This expects a /work/bundle.yaml file in the mounted directory and
+# will write generated bundles to /work/bundle.
+
+# Build stage
+FROM golang:1.24.3-alpine AS build
+WORKDIR /src
+
+# Copy go module files and download dependencies first for better caching
+RUN go install git.wntrmute.dev/kyle/goutils/cmd/cert-bundler@v1.13.2 && \
+    mv /go/bin/cert-bundler /usr/local/bin/cert-bundler
+
+# Runtime stage (kept as golang:alpine per requirement)
+FROM golang:1.24.3-alpine
+
+# Create a work directory that users will typically mount into
+WORKDIR /work
+VOLUME ["/work"]
+
+# Copy the built binary from the builder stage
+COPY --from=build /usr/local/bin/cert-bundler /usr/local/bin/cert-bundler
+
+# Default command: read bundle.yaml from current directory and output to ./bundle
+ENTRYPOINT ["/usr/local/bin/cert-bundler"]
+CMD ["-c", "/work/bundle.yaml", "-o", "/work/bundle"]

cmd/cert-bundler/main.go

@@ -1,66 +1,19 @@
 package main
 
 import (
-	"archive/tar"
-	"archive/zip"
-	"compress/gzip"
-	"crypto/sha256"
-	"crypto/x509"
 	_ "embed"
-	"encoding/pem"
-	"errors"
 	"flag"
 	"fmt"
-	"io"
 	"os"
-	"path/filepath"
-	"strings"
-	"time"
 
-	"git.wntrmute.dev/kyle/goutils/certlib"
-	"gopkg.in/yaml.v2"
+	"git.wntrmute.dev/kyle/goutils/certlib/bundler"
 )
 
-// Config represents the top-level YAML configuration.
-type Config struct {
-	Config struct {
-		Hashes string `yaml:"hashes"`
-		Expiry string `yaml:"expiry"`
-	} `yaml:"config"`
-	Chains map[string]ChainGroup `yaml:"chains"`
-}
-
-// ChainGroup represents a named group of certificate chains.
-type ChainGroup struct {
-	Certs   []CertChain `yaml:"certs"`
-	Outputs Outputs     `yaml:"outputs"`
-}
-
-// CertChain represents a root certificate and its intermediates.
-type CertChain struct {
-	Root          string   `yaml:"root"`
-	Intermediates []string `yaml:"intermediates"`
-}
-
-// Outputs defines output format options.
-type Outputs struct {
-	IncludeSingle     bool     `yaml:"include_single"`
-	IncludeIndividual bool     `yaml:"include_individual"`
-	Manifest          bool     `yaml:"manifest"`
-	Formats           []string `yaml:"formats"`
-	Encoding          string   `yaml:"encoding"`
-}
-
 var (
 	configFile string
 	outputDir  string
 )
 
-var formatExtensions = map[string]string{
-	"zip": ".zip",
-	"tgz": ".tar.gz",
-}
-
 //go:embed README.txt
 var readmeContent string
 
@@ -79,497 +32,10 @@ func main() {
 		os.Exit(1)
 	}
 
-	// Load and parse configuration
-	cfg, err := loadConfig(configFile)
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "Error loading config: %v\n", err)
+	if err := bundler.Run(configFile, outputDir); err != nil {
+		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
 		os.Exit(1)
 	}
 
-	// Parse expiry duration (default 1 year)
-	expiryDuration := 365 * 24 * time.Hour
-	if cfg.Config.Expiry != "" {
-		expiryDuration, err = parseDuration(cfg.Config.Expiry)
-		if err != nil {
-			fmt.Fprintf(os.Stderr, "Error parsing expiry: %v\n", err)
-			os.Exit(1)
-		}
-	}
-
-	// Create output directory if it doesn't exist
-	err = os.MkdirAll(outputDir, 0750)
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "Error creating output directory: %v\n", err)
-		os.Exit(1)
-	}
-
-	// Process each chain group
-	// Pre-allocate createdFiles based on total number of formats across all groups
-	totalFormats := 0
-	for _, group := range cfg.Chains {
-		totalFormats += len(group.Outputs.Formats)
-	}
-	createdFiles := make([]string, 0, totalFormats)
-	for groupName, group := range cfg.Chains {
-		files, perr := processChainGroup(groupName, group, expiryDuration)
-		if perr != nil {
-			fmt.Fprintf(os.Stderr, "Error processing chain group %s: %v\n", groupName, perr)
-			os.Exit(1)
-		}
-		createdFiles = append(createdFiles, files...)
-	}
-
-	// Generate hash file for all created archives
-	if cfg.Config.Hashes != "" {
-		hashFile := filepath.Join(outputDir, cfg.Config.Hashes)
-		if gerr := generateHashFile(hashFile, createdFiles); gerr != nil {
-			fmt.Fprintf(os.Stderr, "Error generating hash file: %v\n", gerr)
-			os.Exit(1)
-		}
-	}
-
 	fmt.Println("Certificate bundling completed successfully")
 }
-
-func loadConfig(path string) (*Config, error) {
-	data, err := os.ReadFile(path)
-	if err != nil {
-		return nil, err
-	}
-
-	var cfg Config
-	if uerr := yaml.Unmarshal(data, &cfg); uerr != nil {
-		return nil, uerr
-	}
-
-	return &cfg, nil
-}
-
-func parseDuration(s string) (time.Duration, error) {
-	// Support simple formats like "1y", "6m", "30d"
-	if len(s) < 2 {
-		return 0, fmt.Errorf("invalid duration format: %s", s)
-	}
-
-	unit := s[len(s)-1]
-	value := s[:len(s)-1]
-
-	var multiplier time.Duration
-	switch unit {
-	case 'y', 'Y':
-		multiplier = 365 * 24 * time.Hour
-	case 'm', 'M':
-		multiplier = 30 * 24 * time.Hour
-	case 'd', 'D':
-		multiplier = 24 * time.Hour
-	default:
-		return time.ParseDuration(s)
-	}
-
-	var num int
-	_, err := fmt.Sscanf(value, "%d", &num)
-	if err != nil {
-		return 0, fmt.Errorf("invalid duration value: %s", s)
-	}
-
-	return time.Duration(num) * multiplier, nil
-}
-
-func processChainGroup(groupName string, group ChainGroup, expiryDuration time.Duration) ([]string, error) {
-	// Default encoding to "pem" if not specified
-	encoding := group.Outputs.Encoding
-	if encoding == "" {
-		encoding = "pem"
-	}
-
-	// Collect certificates from all chains in the group
-	singleFileCerts, individualCerts, err := loadAndCollectCerts(group.Certs, group.Outputs, expiryDuration)
-	if err != nil {
-		return nil, err
-	}
-
-	// Prepare files for inclusion in archives
-	archiveFiles, err := prepareArchiveFiles(singleFileCerts, individualCerts, group.Outputs, encoding)
-	if err != nil {
-		return nil, err
-	}
-
-	// Create archives for the entire group
-	createdFiles, err := createArchiveFiles(groupName, group.Outputs.Formats, archiveFiles)
-	if err != nil {
-		return nil, err
-	}
-
-	return createdFiles, nil
-}
-
-// loadAndCollectCerts loads all certificates from chains and collects them for processing.
-func loadAndCollectCerts(
-	chains []CertChain,
-	outputs Outputs,
-	expiryDuration time.Duration,
-) ([]*x509.Certificate, []certWithPath, error) {
-	var singleFileCerts []*x509.Certificate
-	var individualCerts []certWithPath
-
-	for _, chain := range chains {
-		s, i, cerr := collectFromChain(chain, outputs, expiryDuration)
-		if cerr != nil {
-			return nil, nil, cerr
-		}
-		if len(s) > 0 {
-			singleFileCerts = append(singleFileCerts, s...)
-		}
-		if len(i) > 0 {
-			individualCerts = append(individualCerts, i...)
-		}
-	}
-
-	return singleFileCerts, individualCerts, nil
-}
-
-// collectFromChain loads a single chain, performs checks, and returns the certs to include.
-func collectFromChain(
-	chain CertChain,
-	outputs Outputs,
-	expiryDuration time.Duration,
-) (
-	[]*x509.Certificate,
-	[]certWithPath,
-	error,
-) {
-	var single []*x509.Certificate
-	var indiv []certWithPath
-
-	// Load root certificate
-	rootCert, rerr := certlib.LoadCertificate(chain.Root)
-	if rerr != nil {
-		return nil, nil, fmt.Errorf("failed to load root certificate %s: %w", chain.Root, rerr)
-	}
-
-	// Check expiry for root
-	checkExpiry(chain.Root, rootCert, expiryDuration)
-
-	// Add root to collections if needed
-	if outputs.IncludeSingle {
-		single = append(single, rootCert)
-	}
-	if outputs.IncludeIndividual {
-		indiv = append(indiv, certWithPath{cert: rootCert, path: chain.Root})
-	}
-
-	// Load and validate intermediates
-	for _, intPath := range chain.Intermediates {
-		intCert, lerr := certlib.LoadCertificate(intPath)
-		if lerr != nil {
-			return nil, nil, fmt.Errorf("failed to load intermediate certificate %s: %w", intPath, lerr)
-		}
-
-		// Validate that intermediate is signed by root
-		if sigErr := intCert.CheckSignatureFrom(rootCert); sigErr != nil {
-			return nil, nil, fmt.Errorf(
-				"intermediate %s is not properly signed by root %s: %w",
-				intPath,
-				chain.Root,
-				sigErr,
-			)
-		}
-
-		// Check expiry for intermediate
-		checkExpiry(intPath, intCert, expiryDuration)
-
-		// Add intermediate to collections if needed
-		if outputs.IncludeSingle {
-			single = append(single, intCert)
-		}
-		if outputs.IncludeIndividual {
-			indiv = append(indiv, certWithPath{cert: intCert, path: intPath})
-		}
-	}
-
-	return single, indiv, nil
-}
-
-// prepareArchiveFiles prepares all files to be included in archives.
-func prepareArchiveFiles(
-	singleFileCerts []*x509.Certificate,
-	individualCerts []certWithPath,
-	outputs Outputs,
-	encoding string,
-) ([]fileEntry, error) {
-	var archiveFiles []fileEntry
-
-	// Handle a single bundle file
-	if outputs.IncludeSingle && len(singleFileCerts) > 0 {
-		files, err := encodeCertsToFiles(singleFileCerts, "bundle", encoding, true)
-		if err != nil {
-			return nil, fmt.Errorf("failed to encode single bundle: %w", err)
-		}
-		archiveFiles = append(archiveFiles, files...)
-	}
-
-	// Handle individual files
-	if outputs.IncludeIndividual {
-		for _, cp := range individualCerts {
-			baseName := strings.TrimSuffix(filepath.Base(cp.path), filepath.Ext(cp.path))
-			files, err := encodeCertsToFiles([]*x509.Certificate{cp.cert}, baseName, encoding, false)
-			if err != nil {
-				return nil, fmt.Errorf("failed to encode individual cert %s: %w", cp.path, err)
-			}
-			archiveFiles = append(archiveFiles, files...)
-		}
-	}
-
-	// Generate manifest if requested
-	if outputs.Manifest {
-		manifestContent := generateManifest(archiveFiles)
-		archiveFiles = append(archiveFiles, fileEntry{
-			name:    "MANIFEST",
-			content: manifestContent,
-		})
-	}
-
-	return archiveFiles, nil
-}
-
-// createArchiveFiles creates archive files in the specified formats.
-func createArchiveFiles(groupName string, formats []string, archiveFiles []fileEntry) ([]string, error) {
-	createdFiles := make([]string, 0, len(formats))
-
-	for _, format := range formats {
-		ext, ok := formatExtensions[format]
-		if !ok {
-			return nil, fmt.Errorf("unsupported format: %s", format)
-		}
-		archivePath := filepath.Join(outputDir, groupName+ext)
-		switch format {
-		case "zip":
-			if err := createZipArchive(archivePath, archiveFiles); err != nil {
-				return nil, fmt.Errorf("failed to create zip archive: %w", err)
-			}
-		case "tgz":
-			if err := createTarGzArchive(archivePath, archiveFiles); err != nil {
-				return nil, fmt.Errorf("failed to create tar.gz archive: %w", err)
-			}
-		default:
-			return nil, fmt.Errorf("unsupported format: %s", format)
-		}
-		createdFiles = append(createdFiles, archivePath)
-	}
-
-	return createdFiles, nil
-}
-
-func checkExpiry(path string, cert *x509.Certificate, expiryDuration time.Duration) {
-	now := time.Now()
-	expiryThreshold := now.Add(expiryDuration)
-
-	if cert.NotAfter.Before(expiryThreshold) {
-		daysUntilExpiry := int(cert.NotAfter.Sub(now).Hours() / 24)
-		if daysUntilExpiry < 0 {
-			fmt.Fprintf(
-				os.Stderr,
-				"WARNING: Certificate %s has EXPIRED (expired %d days ago)\n",
-				path,
-				-daysUntilExpiry,
-			)
-		} else {
-			fmt.Fprintf(os.Stderr, "WARNING: Certificate %s will expire in %d days (on %s)\n", path, daysUntilExpiry, cert.NotAfter.Format("2006-01-02"))
-		}
-	}
-}
-
-type fileEntry struct {
-	name    string
-	content []byte
-}
-
-type certWithPath struct {
-	cert *x509.Certificate
-	path string
-}
-
-// encodeCertsToFiles converts certificates to file entries based on encoding type
-// If isSingle is true, certs are concatenated into a single file; otherwise one cert per file.
-func encodeCertsToFiles(
-	certs []*x509.Certificate,
-	baseName string,
-	encoding string,
-	isSingle bool,
-) ([]fileEntry, error) {
-	var files []fileEntry
-
-	switch encoding {
-	case "pem":
-		pemContent := encodeCertsToPEM(certs)
-		files = append(files, fileEntry{
-			name:    baseName + ".pem",
-			content: pemContent,
-		})
-	case "der":
-		if isSingle {
-			// For single file in DER, concatenate all cert DER bytes
-			var derContent []byte
-			for _, cert := range certs {
-				derContent = append(derContent, cert.Raw...)
-			}
-			files = append(files, fileEntry{
-				name:    baseName + ".crt",
-				content: derContent,
-			})
-		} else if len(certs) > 0 {
-			// Individual DER file (should only have one cert)
-			files = append(files, fileEntry{
-				name:    baseName + ".crt",
-				content: certs[0].Raw,
-			})
-		}
-	case "both":
-		// Add PEM version
-		pemContent := encodeCertsToPEM(certs)
-		files = append(files, fileEntry{
-			name:    baseName + ".pem",
-			content: pemContent,
-		})
-		// Add DER version
-		if isSingle {
-			var derContent []byte
-			for _, cert := range certs {
-				derContent = append(derContent, cert.Raw...)
-			}
-			files = append(files, fileEntry{
-				name:    baseName + ".crt",
-				content: derContent,
-			})
-		} else if len(certs) > 0 {
-			files = append(files, fileEntry{
-				name:    baseName + ".crt",
-				content: certs[0].Raw,
-			})
-		}
-	default:
-		return nil, fmt.Errorf("unsupported encoding: %s (must be 'pem', 'der', or 'both')", encoding)
-	}
-
-	return files, nil
-}
-
-// encodeCertsToPEM encodes certificates to PEM format.
-func encodeCertsToPEM(certs []*x509.Certificate) []byte {
-	var pemContent []byte
-	for _, cert := range certs {
-		pemBlock := &pem.Block{
-			Type:  "CERTIFICATE",
-			Bytes: cert.Raw,
-		}
-		pemContent = append(pemContent, pem.EncodeToMemory(pemBlock)...)
-	}
-	return pemContent
-}
-
-func generateManifest(files []fileEntry) []byte {
-	var manifest strings.Builder
-	for _, file := range files {
-		if file.name == "MANIFEST" {
-			continue
-		}
-		hash := sha256.Sum256(file.content)
-		manifest.WriteString(fmt.Sprintf("%x  %s\n", hash, file.name))
-	}
-	return []byte(manifest.String())
-}
-
-// closeWithErr attempts to close all provided closers, joining any close errors with baseErr.
-func closeWithErr(baseErr error, closers ...io.Closer) error {
-	for _, c := range closers {
-		if c == nil {
-			continue
-		}
-		if cerr := c.Close(); cerr != nil {
-			baseErr = errors.Join(baseErr, cerr)
-		}
-	}
-	return baseErr
-}
-
-func createZipArchive(path string, files []fileEntry) error {
-	f, zerr := os.Create(path)
-	if zerr != nil {
-		return zerr
-	}
-
-	w := zip.NewWriter(f)
-
-	for _, file := range files {
-		fw, werr := w.Create(file.name)
-		if werr != nil {
-			return closeWithErr(werr, w, f)
-		}
-		if _, werr = fw.Write(file.content); werr != nil {
-			return closeWithErr(werr, w, f)
-		}
-	}
-
-	// Check errors on close operations
-	if cerr := w.Close(); cerr != nil {
-		_ = f.Close()
-		return cerr
-	}
-	return f.Close()
-}
-
-func createTarGzArchive(path string, files []fileEntry) error {
-	f, terr := os.Create(path)
-	if terr != nil {
-		return terr
-	}
-
-	gw := gzip.NewWriter(f)
-	tw := tar.NewWriter(gw)
-
-	for _, file := range files {
-		hdr := &tar.Header{
-			Name: file.name,
-			Mode: 0644,
-			Size: int64(len(file.content)),
-		}
-		if herr := tw.WriteHeader(hdr); herr != nil {
-			return closeWithErr(herr, tw, gw, f)
-		}
-		if _, werr := tw.Write(file.content); werr != nil {
-			return closeWithErr(werr, tw, gw, f)
-		}
-	}
-
-	// Check errors on close operations in the correct order
-	if cerr := tw.Close(); cerr != nil {
-		_ = gw.Close()
-		_ = f.Close()
-		return cerr
-	}
-	if cerr := gw.Close(); cerr != nil {
-		_ = f.Close()
-		return cerr
-	}
-	return f.Close()
-}
-
-func generateHashFile(path string, files []string) error {
-	f, err := os.Create(path)
-	if err != nil {
-		return err
-	}
-	defer f.Close()
-
-	for _, file := range files {
-		data, rerr := os.ReadFile(file)
-		if rerr != nil {
-			return rerr
-		}
-
-		hash := sha256.Sum256(data)
-		fmt.Fprintf(f, "%x  %s\n", hash, filepath.Base(file))
-	}
-
-	return nil
-}

cmd/cert-bundler/prompt.txt

@@ -1,197 +0,0 @@
-This project is an exploration into the utility of Jetbrains' Junie
-to write smaller but tedious programs.
-
-Task: build a certificate bundling tool in cmd/cert-bundler. It
-creates archives of certificates chains.
-
-A YAML file for this looks something like:
-
-``` yaml
-config:
-  hashes: bundle.sha256
-  expiry: 1y
-chains:
-  core_certs:
-    certs:
-      - root: roots/core-ca.pem
-        intermediates:
-          - int/cca1.pem
-  	- int/cca2.pem
-  	- int/cca3.pem
-      - root: roots/ssh-ca.pem
-        intermediates:
-          - ssh/ssh_dmz1.pem
-  	- ssh/ssh_internal.pem
-  outputs:
-    include_single: true
-    include_individual: true
-    manifest: true
-    formats:
-      - zip
-      - tgz
-```
-
-Some requirements:
-
-1. First, all the certificates should be loaded.
-2. For each root, each of the indivudal intermediates should be
-   checked to make sure they are properly signed by the root CA.
-3. The program should optionally take an expiration period (defaulting
-   to one year), specified in config.expiration, and if any certificate
-   is within that expiration period, a warning should be printed.
-4. If outputs.include_single is true, all certificates under chains
-   should be concatenated into a single file.
-5. If outputs.include_individual is true, all certificates under
-   chains should be included at the root level (e.g. int/cca2.pem
-   would be cca2.pem in the archive).
-6. If bundle.manifest is true, a "MANIFEST" file is created with
-   SHA256 sums of each file included in the archive.
-7. For each of the formats, create an archive file in the output
-   directory (specified with `-o`) with that format.
-   - If zip is included, create a .zip file.
-   - If tgz is included, create a .tar.gz file with default compression
-     levels.
-   - All archive files should include any generated files (single
-     and/or individual) in the top-level directory.
-8. In the output directory, create a file with the same name as
-   config.hashes that contains the SHA256 sum of all files created.
-
------
-
-The outputs.include_single and outputs.include_individual describe
-what should go in the final archive. If both are specified, the output
-archive should include both a single bundle.pem and each individual
-certificate, for example.
-
------
-
-As it stands, given the following `bundle.yaml`:
-
-``` yaml
-config:
-  hashes: bundle.sha256
-  expiry: 1y
-chains:
-  core_certs:
-    certs:
-      - root: pems/gts-r1.pem
-        intermediates:
-          - pems/goog-wr2.pem
-        outputs:
-          include_single: true
-          include_individual: true
-          manifest: true
-          formats:
-            - zip
-            - tgz
-      - root: pems/isrg-root-x1.pem
-        intermediates:
-          - pems/le-e7.pem
-        outputs:
-          include_single: true
-          include_individual: false
-          manifest: true
-          formats:
-            - zip
-            - tgz
-  google_certs:
-    certs:
-      - root: pems/gts-r1.pem
-        intermediates:
-          - pems/goog-wr2.pem
-        outputs:
-          include_single: true
-          include_individual: false
-          manifest: true
-          formats:
-            - tgz
-  lets_encrypt:
-    certs:
-      - root: pems/isrg-root-x1.pem
-        intermediates:
-          - pems/le-e7.pem
-        outputs:
-          include_single: false
-          include_individual: true
-          manifest: false
-          formats:
-            - zip
-```
-
-The program outputs the following files:
-
-- bundle.sha256
-- core_certs_0.tgz (contains individual certs)
-- core_certs_0.zip (contains individual certs)
-- core_certs_1.tgz (contains core_certs.pem)
-- core_certs_1.zip (contains core_certs.pem)
-- google_certs_0.tgz
-- lets_encrypt_0.zip
-
-It should output
-
-- bundle.sha256
-- core_certs.tgz
-- core_certs.zip
-- google_certs.tgz
-- lets_encrypt.zip
-
-core_certs.* should contain `bundle.pem` and all the individual
-certs. There should be no _$n$ variants of archives.
-
------
-
-Add an additional field to outputs: encoding. It should accept one of
-`der`, `pem`, or `both`. If `der`, certificates should be output as a
-`.crt` file containing a DER-encoded certificate. If `pem`, certificates
-should be output as a `.pem` file containing a PEM-encoded certificate.
-If both, both the `.crt` and `.pem` certificate should be included.
-
-For example, given the previous config, if `encoding` is der, the
-google_certs.tgz archive should contain
-
-- bundle.crt
-- MANIFEST
-
-Or with lets_encrypt.zip:
-
-- isrg-root-x1.crt
-- le-e7.crt
-
-However, if `encoding` is pem, the lets_encrypt.zip archive should contain:
-
-- isrg-root-x1.pem
-- le-e7.pem
-
-And if it `encoding` is both, the lets_encrypt.zip archive should contain:
-
-- isrg-root-x1.crt
-- isrg-root-x1.pem
-- le-e7.crt
-- le-e7.pem
-
------
-
-The tgz format should output a `.tar.gz` file instead of a `.tgz` file.
-
------
-
-Move the format extensions to a global variable.
-
------
-
-Write a README.txt with a description of the bundle.yaml format.
-
-Additionally, update the help text for the program (e.g. with `-h`)
-to provide the same detailed information.
-
------
-
-It may be easier to embed the README.txt in the program on build.
-
------
-
-For the archive (tar.gz and zip) writers, make sure errors are
-checked at the end, and don't just defer the close operations.
-
-

cmd/cert-bundler/testdata/bundle.yaml

@@ -2,6 +2,19 @@ config:
   hashes: bundle.sha256
   expiry: 1y
 chains:
+  weird:
+    certs:
+      - root: pems/gts-r1.pem
+        intermediates:
+          - pems/goog-wr2.pem
+      - root: pems/isrg-root-x1.pem
+    outputs:
+      include_single: true
+      include_individual: true
+      manifest: true
+      formats:
+        - zip
+        - tgz
   core_certs:
     certs:
       - root: pems/gts-r1.pem

cmd/cert-bundler/testdata/pkg/bundle.sha256

@@ -1,4 +0,0 @@
-5ed8bf9ed693045faa8a5cb0edc4a870052e56aef6291ce8b1604565affbc2a4  core_certs.zip
-e59eddc590d2f7b790a87c5b56e81697088ab54be382c0e2c51b82034006d308  core_certs.tgz
-51b9b63b1335118079e90700a3a5b847c363808e9116e576ca84f301bc433289  google_certs.tgz
-3d1910ca8835c3ded1755a8c7d6c48083c2f3ff68b2bfbf932aaf27e29d0a232  lets_encrypt.zip

cmd/certser/main.go

@@ -0,0 +1,51 @@
+package main
+
+import (
+	"crypto/x509"
+	"flag"
+	"fmt"
+	"strings"
+
+	"git.wntrmute.dev/kyle/goutils/certlib"
+	"git.wntrmute.dev/kyle/goutils/die"
+	"git.wntrmute.dev/kyle/goutils/lib"
+)
+
+const displayInt lib.HexEncodeMode = iota
+
+func parseDisplayMode(mode string) lib.HexEncodeMode {
+	mode = strings.ToLower(mode)
+
+	if mode == "int" {
+		return displayInt
+	}
+
+	return lib.ParseHexEncodeMode(mode)
+}
+
+func serialString(cert *x509.Certificate, mode lib.HexEncodeMode) string {
+	if mode == displayInt {
+		return cert.SerialNumber.String()
+	}
+
+	return lib.HexEncode(cert.SerialNumber.Bytes(), mode)
+}
+
+func main() {
+	displayAs := flag.String("d", "int", "display mode (int, hex, uhex)")
+	showExpiry := flag.Bool("e", false, "show expiry date")
+	flag.Parse()
+
+	displayMode := parseDisplayMode(*displayAs)
+
+	for _, arg := range flag.Args() {
+		cert, err := certlib.LoadCertificate(arg)
+		die.If(err)
+
+		fmt.Printf("%s: %s", arg, serialString(cert, displayMode))
+		if *showExpiry {
+			fmt.Printf(" (%s)", cert.NotAfter.Format("2006-01-02"))
+		}
+		fmt.Println()
+	}
+}

lib/lib.go

@@ -2,9 +2,11 @@
 package lib
 
 import (
+	"encoding/hex"
 	"fmt"
 	"os"
 	"path/filepath"
+	"strings"
 	"time"
 )
 
@@ -109,3 +111,111 @@ func Duration(d time.Duration) string {
 	s += fmt.Sprintf("%dh%s", hours, d)
 	return s
 }
+
+type HexEncodeMode uint8
+
+const (
+	// HexEncodeLower prints the bytes as lowercase hexadecimal.
+	HexEncodeLower HexEncodeMode = iota + 1
+	// HexEncodeUpper prints the bytes as uppercase hexadecimal.
+	HexEncodeUpper
+	// HexEncodeLowerColon prints the bytes as lowercase hexadecimal
+	// with colons between each pair of bytes.
+	HexEncodeLowerColon
+	// HexEncodeUpperColon prints the bytes as uppercase hexadecimal
+	// with colons between each pair of bytes.
+	HexEncodeUpperColon
+)
+
+func (m HexEncodeMode) String() string {
+	switch m {
+	case HexEncodeLower:
+		return "lower"
+	case HexEncodeUpper:
+		return "upper"
+	case HexEncodeLowerColon:
+		return "lcolon"
+	case HexEncodeUpperColon:
+		return "ucolon"
+	default:
+		panic("invalid hex encode mode")
+	}
+}
+
+func ParseHexEncodeMode(s string) HexEncodeMode {
+	switch strings.ToLower(s) {
+	case "lower":
+		return HexEncodeLower
+	case "upper":
+		return HexEncodeUpper
+	case "lcolon":
+		return HexEncodeLowerColon
+	case "ucolon":
+		return HexEncodeUpperColon
+	}
+
+	panic("invalid hex encode mode")
+}
+
+func hexColons(s string) string {
+	if len(s)%2 != 0 {
+		fmt.Fprintf(os.Stderr, "hex string: %s\n", s)
+		fmt.Fprintf(os.Stderr, "hex length: %d\n", len(s))
+		panic("invalid hex string length")
+	}
+
+	n := len(s)
+	if n <= 2 {
+		return s
+	}
+
+	pairCount := n / 2
+	if n%2 != 0 {
+		pairCount++
+	}
+
+	var b strings.Builder
+	b.Grow(n + pairCount - 1)
+
+	for i := 0; i < n; i += 2 {
+		b.WriteByte(s[i])
+
+		if i+1 < n {
+			b.WriteByte(s[i+1])
+		}
+
+		if i+2 < n {
+			b.WriteByte(':')
+		}
+	}
+
+	return b.String()
+}
+
+func hexEncode(b []byte) string {
+	s := hex.EncodeToString(b)
+
+	if len(s)%2 != 0 {
+		s = "0" + s
+	}
+
+	return s
+}
+
+// HexEncode encodes the given bytes as a hexadecimal string.
+func HexEncode(b []byte, mode HexEncodeMode) string {
+	str := hexEncode(b)
+
+	switch mode {
+	case HexEncodeLower:
+		return str
+	case HexEncodeUpper:
+		return strings.ToUpper(str)
+	case HexEncodeLowerColon:
+		return hexColons(str)
+	case HexEncodeUpperColon:
+		return strings.ToUpper(hexColons(str))
+	default:
+		panic("invalid hex encode mode")
+	}
+}

lib/lib_test.go

@@ -0,0 +1,79 @@
+package lib_test
+
+import (
+	"testing"
+
+	"git.wntrmute.dev/kyle/goutils/lib"
+)
+
+func TestHexEncode_LowerUpper(t *testing.T) {
+	b := []byte{0x0f, 0xa1, 0x00, 0xff}
+
+	gotLower := lib.HexEncode(b, lib.HexEncodeLower)
+	if gotLower != "0fa100ff" {
+		t.Fatalf("lib.HexEncode lower: expected %q, got %q", "0fa100ff", gotLower)
+	}
+
+	gotUpper := lib.HexEncode(b, lib.HexEncodeUpper)
+	if gotUpper != "0FA100FF" {
+		t.Fatalf("lib.HexEncode upper: expected %q, got %q", "0FA100FF", gotUpper)
+	}
+}
+
+func TestHexEncode_ColonModes(t *testing.T) {
+	// Includes leading zero nibble and a zero byte to verify padding and separators
+	b := []byte{0x0f, 0xa1, 0x00, 0xff}
+
+	gotLColon := lib.HexEncode(b, lib.HexEncodeLowerColon)
+	if gotLColon != "0f:a1:00:ff" {
+		t.Fatalf("lib.HexEncode colon lower: expected %q, got %q", "0f:a1:00:ff", gotLColon)
+	}
+
+	gotUColon := lib.HexEncode(b, lib.HexEncodeUpperColon)
+	if gotUColon != "0F:A1:00:FF" {
+		t.Fatalf("lib.HexEncode colon upper: expected %q, got %q", "0F:A1:00:FF", gotUColon)
+	}
+}
+
+func TestHexEncode_EmptyInput(t *testing.T) {
+	var b []byte
+	if got := lib.HexEncode(b, lib.HexEncodeLower); got != "" {
+		t.Fatalf("empty lower: expected empty string, got %q", got)
+	}
+	if got := lib.HexEncode(b, lib.HexEncodeUpper); got != "" {
+		t.Fatalf("empty upper: expected empty string, got %q", got)
+	}
+	if got := lib.HexEncode(b, lib.HexEncodeLowerColon); got != "" {
+		t.Fatalf("empty colon lower: expected empty string, got %q", got)
+	}
+	if got := lib.HexEncode(b, lib.HexEncodeUpperColon); got != "" {
+		t.Fatalf("empty colon upper: expected empty string, got %q", got)
+	}
+}
+
+func TestHexEncode_SingleByte(t *testing.T) {
+	b := []byte{0x0f}
+	if got := lib.HexEncode(b, lib.HexEncodeLower); got != "0f" {
+		t.Fatalf("single byte lower: expected %q, got %q", "0f", got)
+	}
+	if got := lib.HexEncode(b, lib.HexEncodeUpper); got != "0F" {
+		t.Fatalf("single byte upper: expected %q, got %q", "0F", got)
+	}
+	// For a single byte, colon modes should not introduce separators
+	if got := lib.HexEncode(b, lib.HexEncodeLowerColon); got != "0f" {
+		t.Fatalf("single byte colon lower: expected %q, got %q", "0f", got)
+	}
+	if got := lib.HexEncode(b, lib.HexEncodeUpperColon); got != "0F" {
+		t.Fatalf("single byte colon upper: expected %q, got %q", "0F", got)
+	}
+}
+
+func TestHexEncode_InvalidModePanics(t *testing.T) {
+	defer func() {
+		if r := recover(); r == nil {
+			t.Fatalf("expected panic for invalid mode, but function returned normally")
+		}
+	}()
+	// 0 is not a valid lib.HexEncodeMode (valid modes start at 1)
+	_ = lib.HexEncode([]byte{0x01}, lib.HexEncodeMode(0))
+}