crypto/x509: support IP SANs.

Subject Alternative Names in X.509 certificates may include IP
addresses. This change adds support for marshaling, unmarshaling and
verifying this form of SAN.

It also causes IP addresses to only be checked against IP SANs,
rather than against hostnames as was previously the case. This
reflects RFC 6125.

Fixes #4658.

R=golang-dev, mikioh.mikioh, bradfitz
CC=golang-dev
https://golang.org/cl/7336046

src/pkg/crypto/tls/generate_cert.go

@@ -16,36 +16,80 @@ import (
 	"crypto/x509/pkix"
 	"encoding/pem"
 	"flag"
+	"fmt"
 	"log"
 	"math/big"
+	"net"
 	"os"
+	"strings"
 	"time"
 )
 
-var hostName *string = flag.String("host", "127.0.0.1", "Hostname to generate a certificate for")
+var (
+	host      = flag.String("host", "", "Comma-separated hostnames and IPs to generate a certificate for")
+	validFrom = flag.String("start-date", "", "Creation date formatted as Jan 1 15:04:05 2011")
+	validFor  = flag.Duration("duration", 365*24*time.Hour, "Duration that certificate is valid for")
+	isCA      = flag.Bool("ca", false, "whether this cert should be its own Certificate Authority")
+	rsaBits   = flag.Int("rsa-bits", 1024, "Size of RSA key to generate")
+)
 
 func main() {
 	flag.Parse()
 
-	priv, err := rsa.GenerateKey(rand.Reader, 1024)
+	if len(*host) == 0 {
+		log.Fatalf("Missing required --host parameter")
+	}
+
+	priv, err := rsa.GenerateKey(rand.Reader, *rsaBits)
 	if err != nil {
 		log.Fatalf("failed to generate private key: %s", err)
 		return
 	}
 
-	now := time.Now()
+	var notBefore time.Time
+	if len(*validFrom) == 0 {
+		notBefore = time.Now()
+	} else {
+		notBefore, err = time.Parse("Jan 2 15:04:05 2006", *validFrom)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Failed to parse creation date: %s\n", err)
+			os.Exit(1)
+		}
+	}
+
+	notAfter := notBefore.Add(*validFor)
+
+	// end of ASN.1 time
+	endOfTime := time.Date(2049, 12, 31, 23, 59, 59, 0, time.UTC)
+	if notAfter.After(endOfTime) {
+		notAfter = endOfTime
+	}
 
 	template := x509.Certificate{
 		SerialNumber: new(big.Int).SetInt64(0),
 		Subject: pkix.Name{
-			CommonName:   *hostName,
 			Organization: []string{"Acme Co"},
 		},
-		NotBefore: now.Add(-5 * time.Minute).UTC(),
+		NotBefore: notBefore,
-		NotAfter:  now.AddDate(1, 0, 0).UTC(), // valid for 1 year.
+		NotAfter:  notAfter,
 
-		SubjectKeyId: []byte{1, 2, 3, 4},
+		KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
-		KeyUsage:     x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
+		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
+		BasicConstraintsValid: true,
+	}
+
+	hosts := strings.Split(*host, ",")
+	for _, h := range hosts {
+		if ip := net.ParseIP(h); ip != nil {
+			template.IPAddresses = append(template.IPAddresses, ip)
+		} else {
+			template.DNSNames = append(template.DNSNames, h)
+		}
+	}
+
+	if *isCA {
+		template.IsCA = true
+		template.KeyUsage |= x509.KeyUsageCertSign
 	}
 
 	derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, &priv.PublicKey, priv)

src/pkg/crypto/x509/verify.go

@@ -5,6 +5,7 @@
 package x509
 
 import (
+	"net"
 	"runtime"
 	"strings"
 	"time"
@@ -63,14 +64,28 @@ type HostnameError struct {
 }
 
 func (h HostnameError) Error() string {
-	var valid string
 	c := h.Certificate
-	if len(c.DNSNames) > 0 {
+
-		valid = strings.Join(c.DNSNames, ", ")
+	var valid string
+	if ip := net.ParseIP(h.Host); ip != nil {
+		// Trying to validate an IP
+		if len(c.IPAddresses) == 0 {
+			return "x509: cannot validate certificate for " + h.Host + " because it doesn't contain any IP SANs"
+		}
+		for _, san := range c.IPAddresses {
+			if len(valid) > 0 {
+				valid += ", "
+			}
+			valid += san.String()
+		}
 	} else {
-		valid = c.Subject.CommonName
+		if len(c.DNSNames) > 0 {
+			valid = strings.Join(c.DNSNames, ", ")
+		} else {
+			valid = c.Subject.CommonName
+		}
 	}
-	return "certificate is valid for " + valid + ", not " + h.Host
+	return "x509: certificate is valid for " + valid + ", not " + h.Host
 }
 
 // UnknownAuthorityError results when the certificate issuer is unknown
@@ -334,6 +349,22 @@ func toLowerCaseASCII(in string) string {
 // VerifyHostname returns nil if c is a valid certificate for the named host.
 // Otherwise it returns an error describing the mismatch.
 func (c *Certificate) VerifyHostname(h string) error {
+	// IP addresses may be written in [ ].
+	candidateIP := h
+	if len(h) >= 3 && h[0] == '[' && h[len(h)-1] == ']' {
+		candidateIP = h[1 : len(h)-1]
+	}
+	if ip := net.ParseIP(candidateIP); ip != nil {
+		// We only match IP addresses against IP SANs.
+		// https://tools.ietf.org/html/rfc6125#appendix-B.2
+		for _, candidate := range c.IPAddresses {
+			if ip.Equal(candidate) {
+				return nil
+			}
+		}
+		return HostnameError{c, candidateIP}
+	}
+
 	lowered := toLowerCaseASCII(h)
 
 	if len(c.DNSNames) > 0 {

src/pkg/crypto/x509/x509.go

@@ -19,6 +19,8 @@ import (
 	"errors"
 	"io"
 	"math/big"
+	"net"
+	"strconv"
 	"time"
 )
 
@@ -464,6 +466,7 @@ type Certificate struct {
 	// Subject Alternate Name values
 	DNSNames       []string
 	EmailAddresses []string
+	IPAddresses    []net.IP
 
 	// Name constraints
 	PermittedDNSDomainsCritical bool // if true then the name constraints are marked critical.
@@ -841,6 +844,13 @@ func parseCertificate(in *certificate) (*Certificate, error) {
 					case 2:
 						out.DNSNames = append(out.DNSNames, string(v.Bytes))
 						parsedName = true
+					case 7:
+						switch len(v.Bytes) {
+						case net.IPv4len, net.IPv6len:
+							out.IPAddresses = append(out.IPAddresses, v.Bytes)
+						default:
+							return nil, errors.New("x509: certificate contained IP address of length " + strconv.Itoa(len(v.Bytes)))
+						}
 					}
 				}
 
@@ -1085,11 +1095,22 @@ func buildExtensions(template *Certificate) (ret []pkix.Extension, err error) {
 		n++
 	}
 
-	if len(template.DNSNames) > 0 {
+	if len(template.DNSNames) > 0 || len(template.EmailAddresses) > 0 || len(template.IPAddresses) > 0 {
 		ret[n].Id = oidExtensionSubjectAltName
-		rawValues := make([]asn1.RawValue, len(template.DNSNames))
+		var rawValues []asn1.RawValue
-		for i, name := range template.DNSNames {
+		for _, name := range template.DNSNames {
-			rawValues[i] = asn1.RawValue{Tag: 2, Class: 2, Bytes: []byte(name)}
+			rawValues = append(rawValues, asn1.RawValue{Tag: 2, Class: 2, Bytes: []byte(name)})
+		}
+		for _, email := range template.EmailAddresses {
+			rawValues = append(rawValues, asn1.RawValue{Tag: 1, Class: 2, Bytes: []byte(email)})
+		}
+		for _, rawIP := range template.IPAddresses {
+			// If possible, we always want to encode IPv4 addresses in 4 bytes.
+			ip := rawIP.To4()
+			if ip == nil {
+				ip = rawIP
+			}
+			rawValues = append(rawValues, asn1.RawValue{Tag: 7, Class: 2, Bytes: ip})
 		}
 		ret[n].Value, err = asn1.Marshal(rawValues)
 		if err != nil {

src/pkg/crypto/x509/x509_test.go

@@ -19,6 +19,7 @@ import (
 	"encoding/hex"
 	"encoding/pem"
 	"math/big"
+	"net"
 	"reflect"
 	"testing"
 	"time"
@@ -174,6 +175,49 @@ func TestMatchHostnames(t *testing.T) {
 	}
 }
 
+func TestMatchIP(t *testing.T) {
+	// Check that pattern matching is working.
+	c := &Certificate{
+		DNSNames: []string{"*.foo.bar.baz"},
+		Subject: pkix.Name{
+			CommonName: "*.foo.bar.baz",
+		},
+	}
+	err := c.VerifyHostname("quux.foo.bar.baz")
+	if err != nil {
+		t.Fatalf("VerifyHostname(quux.foo.bar.baz): %v", err)
+	}
+
+	// But check that if we change it to be matching against an IP address,
+	// it is rejected.
+	c = &Certificate{
+		DNSNames: []string{"*.2.3.4"},
+		Subject: pkix.Name{
+			CommonName: "*.2.3.4",
+		},
+	}
+	err = c.VerifyHostname("1.2.3.4")
+	if err == nil {
+		t.Fatalf("VerifyHostname(1.2.3.4) should have failed, did not")
+	}
+
+	c = &Certificate{
+		IPAddresses: []net.IP{net.ParseIP("127.0.0.1"), net.ParseIP("::1")},
+	}
+	err = c.VerifyHostname("127.0.0.1")
+	if err != nil {
+		t.Fatalf("VerifyHostname(127.0.0.1): %v", err)
+	}
+	err = c.VerifyHostname("::1")
+	if err != nil {
+		t.Fatalf("VerifyHostname(::1): %v", err)
+	}
+	err = c.VerifyHostname("[::1]")
+	if err != nil {
+		t.Fatalf("VerifyHostname([::1]): %v", err)
+	}
+}
+
 func TestCertificateParse(t *testing.T) {
 	s, _ := hex.DecodeString(certBytes)
 	certs, err := ParseCertificates(s)
@@ -284,8 +328,11 @@ func TestCreateSelfSignedCertificate(t *testing.T) {
 			UnknownExtKeyUsage: testUnknownExtKeyUsage,
 
 			BasicConstraintsValid: true,
-			IsCA:     true,
+			IsCA: true,
-			DNSNames: []string{"test.example.com"},
+
+			DNSNames:       []string{"test.example.com"},
+			EmailAddresses: []string{"gopher@golang.org"},
+			IPAddresses:    []net.IP{net.IPv4(127, 0, 0, 1).To4(), net.ParseIP("2001:4860:0:2001::68")},
 
 			PolicyIdentifiers:   []asn1.ObjectIdentifier{[]int{1, 2, 3}},
 			PermittedDNSDomains: []string{".example.com", "example.com"},
@@ -327,6 +374,18 @@ func TestCreateSelfSignedCertificate(t *testing.T) {
 			t.Errorf("%s: unknown extkeyusage wasn't correctly copied from the template. Got %v, want %v", test.name, cert.UnknownExtKeyUsage, testUnknownExtKeyUsage)
 		}
 
+		if !reflect.DeepEqual(cert.DNSNames, template.DNSNames) {
+			t.Errorf("%s: SAN DNS names differ from template. Got %v, want %v", test.name, cert.DNSNames, template.DNSNames)
+		}
+
+		if !reflect.DeepEqual(cert.EmailAddresses, template.EmailAddresses) {
+			t.Errorf("%s: SAN emails differ from template. Got %v, want %v", test.name, cert.EmailAddresses, template.EmailAddresses)
+		}
+
+		if !reflect.DeepEqual(cert.IPAddresses, template.IPAddresses) {
+			t.Errorf("%s: SAN IPs differ from template. Got %v, want %v", test.name, cert.IPAddresses, template.IPAddresses)
+		}
+
 		if test.checkSig {
 			err = cert.CheckSignatureFrom(cert)
 			if err != nil {

src/pkg/go/build/deps_test.go

@@ -306,7 +306,7 @@ var pkgDeps = map[string][]string{
 	},
 	"crypto/x509": {
 		"L4", "CRYPTO-MATH", "OS", "CGO",
-		"crypto/x509/pkix", "encoding/pem", "encoding/hex", "syscall",
+		"crypto/x509/pkix", "encoding/pem", "encoding/hex", "net", "syscall",
 	},
 	"crypto/x509/pkix": {"L4", "CRYPTO-MATH"},
 

src/pkg/net/http/httptest/server.go

@@ -200,28 +200,29 @@ func (h *waitGroupHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	h.h.ServeHTTP(w, r)
 }
 
-// localhostCert is a PEM-encoded TLS cert with SAN DNS names
+// localhostCert is a PEM-encoded TLS cert with SAN IPs
 // "127.0.0.1" and "[::1]", expiring at the last second of 2049 (the end
 // of ASN.1 time).
+// generated from src/pkg/crypto/tls:
+// go run generate_cert.go  --rsa-bits 512 --host 127.0.0.1,::1,example.com --ca --start-date "Jan 1 00:00:00 1970" --duration=1000000h
 var localhostCert = []byte(`-----BEGIN CERTIFICATE-----
-MIIBTTCB+qADAgECAgEAMAsGCSqGSIb3DQEBBTAAMB4XDTcwMDEwMTAwMDAwMFoX
+MIIBdzCCASOgAwIBAgIBADALBgkqhkiG9w0BAQUwEjEQMA4GA1UEChMHQWNtZSBD
-DTQ5MTIzMTIzNTk1OVowADBaMAsGCSqGSIb3DQEBAQNLADBIAkEAsuA5mAFMj6Q7
+bzAeFw03MDAxMDEwMDAwMDBaFw00OTEyMzEyMzU5NTlaMBIxEDAOBgNVBAoTB0Fj
-qoBzcvKzIq4kzuT5epSp2AkcQfyBHm7K13Ws7u+0b5Vb9gqTf5cAiIKcrtrXVqkL
+bWUgQ28wWjALBgkqhkiG9w0BAQEDSwAwSAJBAN55NcYKZeInyTuhcCwFMhDHCmwa
-8i1UQF6AzwIDAQABo2MwYTAOBgNVHQ8BAf8EBAMCACQwEgYDVR0TAQH/BAgwBgEB
+IUSdtXdcbItRB/yfXGBhiex00IaLXQnSU+QZPRZWYqeTEbFSgihqi1PUDy8CAwEA
-/wIBATANBgNVHQ4EBgQEAQIDBDAPBgNVHSMECDAGgAQBAgMEMBsGA1UdEQQUMBKC
+AaNoMGYwDgYDVR0PAQH/BAQDAgCkMBMGA1UdJQQMMAoGCCsGAQUFBwMBMA8GA1Ud
-CTEyNy4wLjAuMYIFWzo6MV0wCwYJKoZIhvcNAQEFA0EAj1Jsn/h2KHy7dgqutZNB
+EwEB/wQFMAMBAf8wLgYDVR0RBCcwJYILZXhhbXBsZS5jb22HBH8AAAGHEAAAAAAA
-nCGlNN+8vw263Bax9MklR85Ti6a0VWSvp/fDQZUADvmFTDkcXeA24pqmdUxeQDWw
+AAAAAAAAAAAAAAEwCwYJKoZIhvcNAQEFA0EAAoQn/ytgqpiLcZu9XKbCJsJcvkgk
-Pg==
+Se6AbGXgSlq+ZCEVo0qIwSgeBqmsJxUu7NCSOwVJLYNEBO2DtIxoYVk+MA==
 -----END CERTIFICATE-----`)
 
 // localhostKey is the private key for localhostCert.
 var localhostKey = []byte(`-----BEGIN RSA PRIVATE KEY-----
-MIIBPQIBAAJBALLgOZgBTI+kO6qAc3LysyKuJM7k+XqUqdgJHEH8gR5uytd1rO7v
+MIIBPAIBAAJBAN55NcYKZeInyTuhcCwFMhDHCmwaIUSdtXdcbItRB/yfXGBhiex0
-tG+VW/YKk3+XAIiCnK7a11apC/ItVEBegM8CAwEAAQJBAI5sxq7naeR9ahyqRkJi
+0IaLXQnSU+QZPRZWYqeTEbFSgihqi1PUDy8CAwEAAQJBAQdUx66rfh8sYsgfdcvV
-SIv2iMxLuPEHaezf5CYOPWjSjBPyVhyRevkhtqEjF/WkgL7C2nWpYHsUcBDBQVF0
+NoafYpnEcB5s4m/vSVe6SU7dCK6eYec9f9wpT353ljhDUHq3EbmE4foNzJngh35d
-3KECIQDtEGB2ulnkZAahl3WuJziXGLB+p8Wgx7wzSM6bHu1c6QIhAMEp++CaS+SJ
+AekCIQDhRQG5Li0Wj8TM4obOnnXUXf1jRv0UkzE9AHWLG5q3AwIhAPzSjpYUDjVW
-/TrU0zwY/fW4SvQeb49BPZUF3oqR8Xz3AiEA1rAJHBzBgdOQKdE3ksMUPcnvNJSN
+MCUXgckTpKCuGwbJk7424Nb8bLzf3kllAiA5mUBgjfr/WtFSJdWcPQ4Zt9KTMNKD
-poCcELmz2clVXtkCIQCLytuLV38XHToTipR4yMl6O+6arzAjZ56uq7m7ZRV0TwIh
+EUO0ukpTwEIl6wIhAMbGqZK3zAAFdq8DD2jPx+UJXnh0rnOkZBzDtJ6/iN69AiEA
-AM65XAOw8Dsg9Kq78aYXiOEDc5DL0sbFUu/SlmRcCg93
+1Aq8MJgTaYsDQWyU/hDq5YkDJc9e9DSCvUIzqxQWMQE=
------END RSA PRIVATE KEY-----
+-----END RSA PRIVATE KEY-----`)
-`)