Add subjhash tool. Minor cleanups.

cmd/ski/main.go

@@ -49,6 +49,10 @@ func parse(path string) (public []byte, kt, ft string) {
 		lib.Warnx("trailing data in PEM file")
 	}
 
+	if p == nil {
+		die.With("no PEM data found")
+	}
+
 	data = p.Bytes
 
 	switch p.Type {

cmd/subjhash/main.go

@@ -0,0 +1,108 @@
+package main
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"crypto/x509"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/kisom/goutils/die"
+	"github.com/kisom/goutils/lib"
+)
+
+func usage(w io.Writer) {
+	fmt.Fprintf(w, `Print hash of subject or issuer fields in certificates.
+
+Usage: subjhash [-im] certs...
+
+Flags:
+	-i	Print hash of issuer field.
+	-m	Matching mode. This expects arguments to be in the form of
+		pairs of certificates (e.g. previous, new) whose subjects
+		will be compared. For example,
+
+			subjhash -m ca1.pem ca1-renewed.pem	\
+				ca2.pem ca2-renewed.pem
+
+		will exit with a non-zero status if the subject in the
+		ca1-renewed.pem certificate doesn't match the subject in the
+		ca.pem certificate; similarly for ca2.
+`)
+}
+
+// NB: the Issuer field is *also* a subject field. Also, the returned
+// hash is *not* hex encoded.
+func getSubjectInfoHash(cert *x509.Certificate, issuer bool) []byte {
+	if cert == nil {
+		return nil
+	}
+
+	var subject []byte
+	if issuer {
+		subject = cert.RawIssuer
+	} else {
+		subject = cert.RawSubject
+	}
+
+	digest := sha256.Sum256(subject)
+	return digest[:]
+}
+
+func printDigests(paths []string, issuer bool) {
+	for _, path := range paths {
+		cert, err := lib.LoadCertificate(path)
+		if err != nil {
+			lib.Warn(err, "failed to load certificate from %s", path)
+			continue
+		}
+
+		digest := getSubjectInfoHash(cert, issuer)
+		fmt.Printf("%x  %s\n", digest, path)
+	}
+}
+
+func matchDigests(paths []string, issuer bool) {
+	if (len(paths) % 2) != 0 {
+		lib.Errx(lib.ExitFailure, "not all certificates are paired")
+	}
+
+	var invalid int
+	for {
+		if len(paths) == 0 {
+			break
+		}
+		fst := paths[0]
+		snd := paths[1]
+		paths = paths[2:]
+
+		fstCert, err := lib.LoadCertificate(fst)
+		die.If(err)
+		sndCert, err := lib.LoadCertificate(snd)
+		die.If(err)
+		if !bytes.Equal(getSubjectInfoHash(fstCert, issuer), getSubjectInfoHash(sndCert, issuer)) {
+			lib.Warnx("certificates don't match: %s and %s", fst, snd)
+			invalid++
+		}
+	}
+
+	if invalid > 0 {
+		os.Exit(1)
+	}
+}
+
+func main() {
+	var issuer, match bool
+	flag.BoolVar(&issuer, "i", false, "print the issuer")
+	flag.BoolVar(&match, "m", false, "match mode")
+	flag.Parse()
+
+	paths := flag.Args()
+	if match {
+		matchDigests(paths, issuer)
+	} else {
+		printDigests(paths, issuer)
+	}
+}

lib/lib.go

@@ -2,7 +2,11 @@
 package lib
 
 import (
+	"crypto/x509"
+	"encoding/pem"
+	"errors"
 	"fmt"
+	"io/ioutil"
 	"os"
 	"path/filepath"
 	"time"
@@ -79,6 +83,7 @@ var (
 	yearDuration = (365 * dayDuration) + (6 * time.Hour)
 )
 
+// Duration returns a prettier string for time.Durations.
 func Duration(d time.Duration) string {
 	var s string
 	if d >= yearDuration {
@@ -102,3 +107,78 @@ func Duration(d time.Duration) string {
 	s += fmt.Sprintf("%dh%s", hours, d)
 	return s
 }
+
+// ReadCertificate reads a DER or PEM-encoded certificate from the
+// byte slice.
+func ReadCertificate(in []byte) (cert *x509.Certificate, rest []byte, err error) {
+	if len(in) == 0 {
+		err = errors.New("lib: empty certificate")
+		return
+	}
+
+	if in[0] == '-' {
+		p, remaining := pem.Decode(in)
+		if p == nil {
+			err = errors.New("lib: invalid PEM file")
+			return
+		}
+
+		rest = remaining
+		if p.Type != "CERTIFICATE" {
+			err = fmt.Errorf("lib: expected a CERTIFICATE PEM file, but have %s", p.Type)
+			return
+		}
+
+		in = p.Bytes
+	}
+
+	cert, err = x509.ParseCertificate(in)
+	return
+}
+
+// ReadCertificates tries to read all the certificates in a
+// PEM-encoded collection.
+func ReadCertificates(in []byte) (certs []*x509.Certificate, err error) {
+	var cert *x509.Certificate
+	for {
+		cert, in, err = ReadCertificate(in)
+		if err != nil {
+			break
+		}
+
+		if cert == nil {
+			break
+		}
+
+		certs = append(certs, cert)
+		if len(in) == 0 {
+			break
+		}
+	}
+
+	return certs, err
+}
+
+// LoadCertificate tries to read a single certificate from disk. If
+// the file contains multiple certificates (e.g. a chain), only the
+// first certificate is returned.
+func LoadCertificate(path string) (*x509.Certificate, error) {
+	in, err := ioutil.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+
+	cert, _, err := ReadCertificate(in)
+	return cert, err
+}
+
+// LoadCertificates tries to read all the certificates in a file,
+// returning them in the order that it found them in the file.
+func LoadCertificates(path string) ([]*x509.Certificate, error) {
+	in, err := ioutil.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+
+	return ReadCertificates(in)
+}

lib/lib_test.go

@@ -0,0 +1,139 @@
+package lib
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/kisom/goutils/assert"
+)
+
+// some CA certs I found on my computerbox.
+var testCerts = `-----BEGIN CERTIFICATE-----
+MIIH0zCCBbugAwIBAgIIXsO3pkN/pOAwDQYJKoZIhvcNAQEFBQAwQjESMBAGA1UE
+AwwJQUNDVlJBSVoxMRAwDgYDVQQLDAdQS0lBQ0NWMQ0wCwYDVQQKDARBQ0NWMQsw
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+pPVWQxaZLPSkVrQ0uGE3ycJYgBugl6H8WY3pEfbRD0tVNEYqi4Y7
+-----END CERTIFICATE-----
+-----BEGIN CERTIFICATE-----
+MIIFtTCCA52gAwIBAgIIYY3HhjsBggUwDQYJKoZIhvcNAQEFBQAwRDEWMBQGA1UE
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+Z05phkOTOPu220+DkdRgfks+KzgHVZhepA==
+-----END CERTIFICATE-----
+-----BEGIN CERTIFICATE-----
+MIIFuzCCA6OgAwIBAgIIVwoRl0LE48wwDQYJKoZIhvcNAQELBQAwazELMAkGA1UE
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+LnPqZih4zR0Uv6CPLy64Lo7yFIrM6bV8+2ydDKXhlg==
+-----END CERTIFICATE-----
+`
+
+func TestReadCertificate(t *testing.T) {
+	cert, remaining, err := ReadCertificate([]byte(testCerts))
+	assert.NoErrorT(t, err)
+
+	assert.BoolT(t, len(remaining) > 0, "lib: expected extra data from ReadCertificate")
+	assert.BoolT(t, cert != nil, "lib: expected an actual certificate to have been returned")
+}
+
+func TestReadCertificates(t *testing.T) {
+	certs, err := ReadCertificates([]byte(testCerts))
+	assert.NoErrorT(t, err)
+
+	assert.BoolT(t, len(certs) == 3, fmt.Sprintf("lib: expected three certificates, have %d", len(certs)))
+	for _, cert := range certs {
+		assert.BoolT(t, cert != nil, "lib: expected an actual certificate to have been returned")
+	}
+}