Add ski utility.

cmd/ski/README

@@ -0,0 +1,30 @@
+ski: print subject public key info
+
+Usage:
+	ski [-hm] files...
+
+Flags:
+	-h	Print a help message and exit.
+	-m	All SKIs should match.
+
+Examples:
+
+	Printing the SKI of a private key and certificate:
+
+	$ ski *
+	server.key  3A:AB:D1:B2:E5:7A:F2:5A:D5:8E:8B:7B:25:D9:41:90:F8:6B:A3:5E (RSA private key)
+	[ski] trailing data in PEM file
+	server.pem  3A:AB:D1:B2:E5:7A:F2:5A:D5:8E:8B:7B:25:D9:41:90:F8:6B:A3:5E (RSA certificate)
+
+	Making sure the SKIs match:
+
+	$ ski -m *
+	tyrfingr.key  3A:AB:D1:B2:E5:7A:F2:5A:D5:8E:8B:7B:25:D9:41:90:F8:6B:A3:5E (RSA private key)
+	[ski] trailing data in PEM file
+	tyrfingr.pem  3A:AB:D1:B2:E5:7A:F2:5A:D5:8E:8B:7B:25:D9:41:90:F8:6B:A3:5E (RSA certificate)
+
+	Making sure the SKIs match with a bad certificate:
+	$ ski -m server.key bad.pem
+	server.key  3A:AB:D1:B2:E5:7A:F2:5A:D5:8E:8B:7B:25:D9:41:90:F8:6B:A3:5E (RSA private key)
+	[ski] bad.pem: SKI mismatch (3A:AB:D1:B2:E5:7A:F2:5A:D5:8E:8B:7B:25:D9:41:90:F8:6B:A3:5E != 90:AF:6A:3A:94:5A:0B:D8:90:EA:12:56:73:DF:43:B4:3A:28:DA:E7)
+	bad.pem  90:AF:6A:3A:94:5A:0B:D8:90:EA:12:56:73:DF:43:B4:3A:28:DA:E7 (RSA certificate)

cmd/ski/main.go

@@ -0,0 +1,187 @@
+package main
+
+import (
+	"bytes"
+	"crypto"
+	"crypto/ecdsa"
+	"crypto/rsa"
+	"crypto/sha1"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/asn1"
+	"encoding/pem"
+	"flag"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"strings"
+
+	"github.com/kisom/goutils/die"
+	"github.com/kisom/goutils/lib"
+)
+
+func usage(w io.Writer) {
+	fmt.Fprintf(w, `ski: print subject key info for PEM-encoded files
+
+Usage:
+	ski [-hm] files...
+
+Flags:
+	-h	Print this help message.
+	-m	All SKIs should match; as soon as an SKI mismatch is found,
+		it is reported.
+
+`)
+}
+
+func init() {
+	flag.Usage = func() { usage(os.Stderr) }
+}
+
+func parse(path string) (public []byte, kt, ft string) {
+	data, err := ioutil.ReadFile(path)
+	die.If(err)
+
+	data = bytes.TrimSpace(data)
+	p, rest := pem.Decode(data)
+	if len(rest) > 0 {
+		lib.Warnx("trailing data in PEM file")
+	}
+
+	data = p.Bytes
+
+	switch p.Type {
+	case "PRIVATE KEY", "RSA PRIVATE KEY", "EC PRIVATE KEY":
+		public, kt = parseKey(data)
+		ft = "private key"
+	case "CERTIFICATE":
+		public, kt = parseCertificate(data)
+		ft = "certificate"
+	case "CERTIFICATE REQUEST":
+		public, kt = parseCSR(data)
+		ft = "certificate request"
+	default:
+		die.With("unknown PEM type %s", p.Type)
+	}
+
+	return
+}
+
+func parseKey(data []byte) (public []byte, kt string) {
+	privInterface, err := x509.ParsePKCS8PrivateKey(data)
+	if err != nil {
+		privInterface, err = x509.ParsePKCS1PrivateKey(data)
+		if err != nil {
+			privInterface, err = x509.ParseECPrivateKey(data)
+			if err != nil {
+				die.With("couldn't parse private key.")
+			}
+		}
+	}
+
+	var priv crypto.Signer
+	switch privInterface.(type) {
+	case *rsa.PrivateKey:
+		priv = privInterface.(*rsa.PrivateKey)
+		kt = "RSA"
+	case *ecdsa.PrivateKey:
+		priv = privInterface.(*ecdsa.PrivateKey)
+		kt = "ECDSA"
+	default:
+		die.With("unknown private key type %T", privInterface)
+	}
+
+	public, err = x509.MarshalPKIXPublicKey(priv.Public())
+	die.If(err)
+
+	return
+}
+
+func parseCertificate(data []byte) (public []byte, kt string) {
+	cert, err := x509.ParseCertificate(data)
+	die.If(err)
+
+	pub := cert.PublicKey
+	switch pub.(type) {
+	case *rsa.PublicKey:
+		kt = "RSA"
+	case *ecdsa.PublicKey:
+		kt = "ECDSA"
+	default:
+		die.With("unknown public key type %T", pub)
+	}
+
+	public, err = x509.MarshalPKIXPublicKey(pub)
+	die.If(err)
+	return
+}
+
+func parseCSR(data []byte) (public []byte, kt string) {
+	csr, err := x509.ParseCertificateRequest(data)
+	die.If(err)
+
+	pub := csr.PublicKey
+	switch pub.(type) {
+	case *rsa.PublicKey:
+		kt = "RSA"
+	case *ecdsa.PublicKey:
+		kt = "ECDSA"
+	default:
+		die.With("unknown public key type %T", pub)
+	}
+
+	public, err = x509.MarshalPKIXPublicKey(pub)
+	die.If(err)
+	return
+}
+
+func dumpHex(in []byte) string {
+	var s string
+	for i := range in {
+		s += fmt.Sprintf("%02X:", in[i])
+	}
+
+	return strings.Trim(s, ":")
+}
+
+type subjectPublicKeyInfo struct {
+	Algorithm        pkix.AlgorithmIdentifier
+	SubjectPublicKey asn1.BitString
+}
+
+func main() {
+	var help, shouldMatch bool
+	flag.BoolVar(&help, "h", false, "print a help message and exit")
+	flag.BoolVar(&shouldMatch, "m", false, "all SKIs should match")
+	flag.Parse()
+
+	if help {
+		usage(os.Stdout)
+		os.Exit(0)
+	}
+
+	var ski string
+	for _, path := range flag.Args() {
+		public, kt, ft := parse(path)
+
+		var subPKI subjectPublicKeyInfo
+		_, err := asn1.Unmarshal(public, &subPKI)
+		if err != nil {
+			lib.Warn(err, "failed to get subject PKI")
+			continue
+		}
+
+		pubHash := sha1.Sum(subPKI.SubjectPublicKey.Bytes)
+		pubHashString := dumpHex(pubHash[:])
+		if ski == "" {
+			ski = pubHashString
+		}
+
+		if shouldMatch && ski != pubHashString {
+			lib.Warnx("%s: SKI mismatch (%s != %s)",
+				path, ski, pubHashString)
+		}
+		fmt.Printf("%s  %s (%s %s)\n", path, pubHashString, kt, ft)
+	}
+}