minor updates

Builds certificate bundles.

certlib/hosts/hosts.go

@@ -0,0 +1,82 @@
+package hosts
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"net/url"
+	"strconv"
+	"strings"
+)
+
+type Target struct {
+	Host string
+	Port int
+}
+
+func (t *Target) String() string {
+	return fmt.Sprintf("%s:%d", t.Host, t.Port)
+}
+
+func parseURL(host string) (string, int, error) {
+	url, err := url.Parse(host)
+	if err != nil {
+		return "", 0, fmt.Errorf("certlib/hosts: invalid host: %s", host)
+	}
+
+	if strings.ToLower(url.Scheme) != "https" {
+		return "", 0, errors.New("certlib/hosts: only https scheme supported")
+	}
+
+	if url.Port() == "" {
+		return url.Hostname(), 443, nil
+	}
+
+	port, err := strconv.ParseInt(url.Port(), 10, 16)
+	if err != nil {
+		return "", 0, fmt.Errorf("certlib/hosts: invalid port: %s", url.Port())
+	}
+
+	return url.Hostname(), int(port), nil
+}
+
+func parseHostPort(host string) (string, int, error) {
+	host, sport, err := net.SplitHostPort(host)
+	if err == nil {
+		port, err := strconv.ParseInt(sport, 10, 16)
+		if err != nil {
+			return "", 0, fmt.Errorf("certlib/hosts: invalid port: %s", sport)
+		}
+
+		return host, int(port), nil
+	}
+
+	return host, 443, nil
+}
+
+func ParseHost(host string) (*Target, error) {
+	host, port, err := parseURL(host)
+	if err == nil {
+		return &Target{Host: host, Port: port}, nil
+	}
+
+	host, port, err = parseHostPort(host)
+	if err == nil {
+		return &Target{Host: host, Port: port}, nil
+	}
+
+	return nil, fmt.Errorf("certlib/hosts: invalid host: %s", host)
+}
+
+func ParseHosts(hosts ...string) ([]*Target, error) {
+	targets := make([]*Target, 0, len(hosts))
+	for _, host := range hosts {
+		target, err := ParseHost(host)
+		if err != nil {
+			return nil, err
+		}
+		targets = append(targets, target)
+	}
+
+	return targets, nil
+}

cmd/cert-bundler/README.txt

@@ -0,0 +1,148 @@
+cert-bundler: create certificate chain archives
+------------------------------------------------
+
+Description
+  cert-bundler creates archives of certificate chains from a YAML configuration
+  file. It validates certificates, checks expiration dates, and generates
+  archives in multiple formats (zip, tar.gz) with optional manifest files
+  containing SHA256 checksums.
+
+Usage
+  cert-bundler [options]
+
+  Options:
+    -c <file>    Path to YAML configuration file (default: bundle.yaml)
+    -o <dir>     Output directory for archives (default: pkg)
+
+YAML Configuration Format
+
+  The configuration file uses the following structure:
+
+  config:
+    hashes: <filename>
+    expiry: <duration>
+  chains:
+    <group_name>:
+      certs:
+        - root: <path>
+          intermediates:
+            - <path>
+            - <path>
+        - root: <path>
+          intermediates:
+            - <path>
+      outputs:
+        include_single: <bool>
+        include_individual: <bool>
+        manifest: <bool>
+        encoding: <encoding>
+        formats:
+          - <format>
+          - <format>
+
+Configuration Fields
+
+  config:
+    hashes: (optional) Name of the file to write SHA256 checksums of all
+            generated archives. If omitted, no hash file is created.
+    expiry: (optional) Expiration warning threshold. Certificates expiring
+            within this period will trigger a warning. Supports formats like
+            "1y" (year), "6m" (month), "30d" (day). Default: 1y
+
+  chains:
+    Each key under "chains" defines a named certificate group. All certificates
+    in a group are bundled together into archives with the group name.
+
+    certs:
+      List of certificate chains. Each chain has:
+        root: Path to root CA certificate (PEM or DER format)
+        intermediates: List of paths to intermediate certificates
+
+      All intermediates are validated against their root CA. An error is
+      reported if signature verification fails.
+
+    outputs:
+      Defines output formats and content for the group's archives:
+
+        include_single: (bool) If true, all certificates in the group are
+                        concatenated into a single file named "bundle.pem"
+                        (or "bundle.crt" for DER encoding).
+
+        include_individual: (bool) If true, each certificate is included as
+                            a separate file in the archive, named after the
+                            original file (e.g., "int/cca2.pem" becomes
+                            "cca2.pem").
+
+        manifest: (bool) If true, a MANIFEST file is included containing
+                  SHA256 checksums of all files in the archive.
+
+        encoding: Specifies certificate encoding in the archive:
+                  - "pem": PEM format with .pem extension (default)
+                  - "der": DER format with .crt extension
+                  - "both": Both PEM and DER versions are included
+
+        formats: List of archive formats to generate:
+                 - "zip": Creates a .zip archive
+                 - "tgz": Creates a .tar.gz archive
+
+Output Files
+
+  For each group and format combination, an archive is created:
+    <group_name>.zip or <group_name>.tar.gz
+
+  If config.hashes is specified, a hash file is created in the output directory
+  containing SHA256 checksums of all generated archives.
+
+Example Configuration
+
+  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
+        encoding: pem
+        formats:
+          - zip
+          - tgz
+
+  This configuration:
+    - Creates core_certs.zip and core_certs.tar.gz in the output directory
+    - Each archive contains bundle.pem (all certificates concatenated)
+    - Each archive contains individual certificates (core-ca.pem, cca1.pem, etc.)
+    - Each archive includes a MANIFEST file with SHA256 checksums
+    - Creates bundle.sha256 with checksums of the two archives
+    - Warns if any certificate expires within 1 year
+
+Examples
+
+  # Create bundles using default configuration (bundle.yaml -> pkg/)
+  cert-bundler
+
+  # Use custom configuration and output directory
+  cert-bundler -c myconfig.yaml -o output
+
+  # Create bundles from testdata configuration
+  cert-bundler -c testdata/bundle.yaml -o testdata/pkg
+
+Notes
+  - Certificate paths in the YAML are relative to the current working directory
+  - All intermediates must be properly signed by their specified root CA
+  - Certificates are checked for expiration; warnings are printed to stderr
+  - Expired certificates do not prevent archive creation but generate warnings
+  - Both PEM and DER certificate formats are supported as input
+  - Archive filenames use the group name, not individual chain names
+  - If both include_single and include_individual are true, archives contain both

cmd/cert-bundler/main.go

@@ -0,0 +1,489 @@
+package main
+
+import (
+	"archive/tar"
+	"archive/zip"
+	"compress/gzip"
+	"crypto/sha256"
+	"crypto/x509"
+	_ "embed"
+	"encoding/pem"
+	"flag"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"git.wntrmute.dev/kyle/goutils/certlib"
+	"gopkg.in/yaml.v2"
+)
+
+// 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
+
+func usage() {
+	fmt.Fprint(os.Stderr, readmeContent)
+}
+
+func main() {
+	flag.Usage = usage
+	flag.StringVar(&configFile, "c", "bundle.yaml", "path to YAML configuration file")
+	flag.StringVar(&outputDir, "o", "pkg", "output directory for archives")
+	flag.Parse()
+
+	if configFile == "" {
+		fmt.Fprintf(os.Stderr, "Error: configuration file required (-c flag)\n")
+		os.Exit(1)
+	}
+
+	// Load and parse configuration
+	cfg, err := loadConfig(configFile)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Error loading config: %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
+	if err := os.MkdirAll(outputDir, 0755); err != nil {
+		fmt.Fprintf(os.Stderr, "Error creating output directory: %v\n", err)
+		os.Exit(1)
+	}
+
+	// Process each chain group
+	createdFiles := []string{}
+	for groupName, group := range cfg.Chains {
+		files, err := processChainGroup(groupName, group, expiryDuration)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Error processing chain group %s: %v\n", groupName, err)
+			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 err := generateHashFile(hashFile, createdFiles); err != nil {
+			fmt.Fprintf(os.Stderr, "Error generating hash file: %v\n", err)
+			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 err := yaml.Unmarshal(data, &cfg); err != nil {
+		return nil, err
+	}
+
+	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) {
+	var createdFiles []string
+
+	// Default encoding to "pem" if not specified
+	encoding := group.Outputs.Encoding
+	if encoding == "" {
+		encoding = "pem"
+	}
+
+	// Collect data from all chains in the group
+	var singleFileCerts []*x509.Certificate
+	var individualCerts []certWithPath
+
+	for _, chain := range group.Certs {
+		// Step 1: Load all certificates for this chain
+		allCerts := make(map[string]*x509.Certificate)
+
+		// Load root certificate
+		rootCert, err := certlib.LoadCertificate(chain.Root)
+		if err != nil {
+			return nil, fmt.Errorf("failed to load root certificate %s: %v", chain.Root, err)
+		}
+		allCerts[chain.Root] = rootCert
+
+		// Check expiry for root
+		checkExpiry(chain.Root, rootCert, expiryDuration)
+
+		// Add root to single file if needed
+		if group.Outputs.IncludeSingle {
+			singleFileCerts = append(singleFileCerts, rootCert)
+		}
+
+		// Add root to individual files if needed
+		if group.Outputs.IncludeIndividual {
+			individualCerts = append(individualCerts, certWithPath{
+				cert: rootCert,
+				path: chain.Root,
+			})
+		}
+
+		// Step 2: Load and validate intermediates
+		for _, intPath := range chain.Intermediates {
+			intCert, err := certlib.LoadCertificate(intPath)
+			if err != nil {
+				return nil, fmt.Errorf("failed to load intermediate certificate %s: %v", intPath, err)
+			}
+			allCerts[intPath] = intCert
+
+			// Validate that intermediate is signed by root
+			if err := intCert.CheckSignatureFrom(rootCert); err != nil {
+				return nil, fmt.Errorf("intermediate %s is not properly signed by root %s: %v", intPath, chain.Root, err)
+			}
+
+			// Check expiry for intermediate
+			checkExpiry(intPath, intCert, expiryDuration)
+
+			// Add intermediate to a single file if needed
+			if group.Outputs.IncludeSingle {
+				singleFileCerts = append(singleFileCerts, intCert)
+			}
+
+			// Add intermediate to individual files if needed
+			if group.Outputs.IncludeIndividual {
+				individualCerts = append(individualCerts, certWithPath{
+					cert: intCert,
+					path: intPath,
+				})
+			}
+		}
+	}
+
+	// Prepare files for inclusion in archives for the entire group.
+	var archiveFiles []fileEntry
+
+	// Handle a single bundle file.
+	if group.Outputs.IncludeSingle && len(singleFileCerts) > 0 {
+		files, err := encodeCertsToFiles(singleFileCerts, "bundle", encoding, true)
+		if err != nil {
+			return nil, fmt.Errorf("failed to encode single bundle: %v", err)
+		}
+		archiveFiles = append(archiveFiles, files...)
+	}
+
+	// Handle individual files
+	if group.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: %v", cp.path, err)
+			}
+			archiveFiles = append(archiveFiles, files...)
+		}
+	}
+
+	// Generate manifest if requested
+	if group.Outputs.Manifest {
+		manifestContent := generateManifest(archiveFiles)
+		archiveFiles = append(archiveFiles, fileEntry{
+			name:    "MANIFEST",
+			content: manifestContent,
+		})
+	}
+
+	// Create archives for the entire group
+	for _, format := range group.Outputs.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: %v", err)
+			}
+		case "tgz":
+			if err := createTarGzArchive(archivePath, archiveFiles); err != nil {
+				return nil, fmt.Errorf("failed to create tar.gz archive: %v", 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, err := encodeCertsToPEM(certs, isSingle)
+		if err != nil {
+			return nil, err
+		}
+		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 {
+			// Individual DER file (should only have one cert)
+			if len(certs) > 0 {
+				files = append(files, fileEntry{
+					name:    baseName + ".crt",
+					content: certs[0].Raw,
+				})
+			}
+		}
+	case "both":
+		// Add PEM version
+		pemContent, err := encodeCertsToPEM(certs, isSingle)
+		if err != nil {
+			return nil, err
+		}
+		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, concatenate bool) ([]byte, error) {
+	var pemContent []byte
+	for _, cert := range certs {
+		pemBlock := &pem.Block{
+			Type:  "CERTIFICATE",
+			Bytes: cert.Raw,
+		}
+		pemContent = append(pemContent, pem.EncodeToMemory(pemBlock)...)
+	}
+	return pemContent, nil
+}
+
+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())
+}
+
+func createZipArchive(path string, files []fileEntry) error {
+	f, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	w := zip.NewWriter(f)
+	defer w.Close()
+
+	for _, file := range files {
+		fw, err := w.Create(file.name)
+		if err != nil {
+			return err
+		}
+		if _, err := fw.Write(file.content); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func createTarGzArchive(path string, files []fileEntry) error {
+	f, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	gw := gzip.NewWriter(f)
+	defer gw.Close()
+
+	tw := tar.NewWriter(gw)
+	defer tw.Close()
+
+	for _, file := range files {
+		hdr := &tar.Header{
+			Name: file.name,
+			Mode: 0644,
+			Size: int64(len(file.content)),
+		}
+		if err := tw.WriteHeader(hdr); err != nil {
+			return err
+		}
+		if _, err := tw.Write(file.content); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+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, err := os.ReadFile(file)
+		if err != nil {
+			return err
+		}
+
+		hash := sha256.Sum256(data)
+		fmt.Fprintf(f, "%x  %s\n", hash, filepath.Base(file))
+	}
+
+	return nil
+}

cmd/cert-bundler/prompt.txt

@@ -0,0 +1,189 @@
+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.
+
+

cmd/cert-bundler/testdata/bundle.yaml

@@ -0,0 +1,43 @@
+config:
+  hashes: bundle.sha256
+  expiry: 1y
+chains:
+  core_certs:
+    certs:
+      - root: pems/gts-r1.pem
+        intermediates:
+          - pems/goog-wr2.pem
+      - root: pems/isrg-root-x1.pem
+        intermediates:
+          - pems/le-e7.pem
+    outputs:
+      include_single: true
+      include_individual: true
+      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
+      encoding: der
+      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
+      encoding: both
+      formats:
+        - zip

cmd/cert-bundler/testdata/pems/goog-wr2.pem

@@ -0,0 +1,29 @@
+-----BEGIN CERTIFICATE-----
+MIIFCzCCAvOgAwIBAgIQf/AFoHxM3tEArZ1mpRB7mDANBgkqhkiG9w0BAQsFADBH
+MQswCQYDVQQGEwJVUzEiMCAGA1UEChMZR29vZ2xlIFRydXN0IFNlcnZpY2VzIExM
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+/oTxUFqOl2stKnn7QGTq8z29W+GgBLCXSBxC9epaHM0myFH/FJlniXJfHeytWt0=
+-----END CERTIFICATE-----

cmd/cert-bundler/testdata/pems/gts-r1.pem

@@ -0,0 +1,31 @@
+-----BEGIN CERTIFICATE-----
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+bP6MvPJwNQzcmRk13NfIRmPVNnGuV/u3gm3c
+-----END CERTIFICATE-----

cmd/cert-bundler/testdata/pems/isrg-root-x1.pem

@@ -0,0 +1,31 @@
+-----BEGIN CERTIFICATE-----
+MIIFazCCA1OgAwIBAgIRAIIQz7DSQONZRGPgu2OCiwAwDQYJKoZIhvcNAQELBQAw
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+-----END CERTIFICATE-----

cmd/cert-bundler/testdata/pems/le-e7.pem

@@ -0,0 +1,26 @@
+-----BEGIN CERTIFICATE-----
+MIIEVzCCAj+gAwIBAgIRAKp18eYrjwoiCWbTi7/UuqEwDQYJKoZIhvcNAQELBQAw
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++VUwFj9tmWxyR/M=
+-----END CERTIFICATE-----

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

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