[release-branch.go1.8] crypto/x509: reject intermediates with unknown critical extensions.

In https://golang.org/cl/9390 I messed up and put the critical extension
test in the wrong function. Thus it only triggered for leaf certificates
and not for intermediates or roots.

In practice, this is not expected to have a security impact in the web
PKI.

[Merge conflicts resolved in verify_test.go]

Change-Id: I4f2464ef2fb71b5865389901f293062ba1327702
Reviewed-on: https://go-review.googlesource.com/69294
Run-TryBot: Adam Langley <agl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-on: https://go-review.googlesource.com/70842
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Adam Langley <agl@golang.org>

3 files changed, 100 insertions, 72 deletions

diff --git a/src/crypto/x509/verify.go b/src/crypto/x509/verify.go
index 29345a1755..67f9ff530e 100644
--- a/src/crypto/x509/verify.go
+++ b/src/crypto/x509/verify.go
@@ -191,6 +191,10 @@ func matchNameConstraint(domain, constraint string) bool {
 
 // isValid performs validity checks on the c.
 func (c *Certificate) isValid(certType int, currentChain []*Certificate, opts *VerifyOptions) error {
+	if len(c.UnhandledCriticalExtensions) > 0 {
+		return UnhandledCriticalExtension{}
+	}
+
 	if len(currentChain) > 0 {
 		child := currentChain[len(currentChain)-1]
 		if !bytes.Equal(child.RawIssuer, c.RawSubject) {
@@ -279,10 +283,6 @@ func (c *Certificate) Verify(opts VerifyOptions) (chains [][]*Certificate, err e
 		return c.systemVerify(&opts)
 	}
 
-	if len(c.UnhandledCriticalExtensions) > 0 {
-		return nil, UnhandledCriticalExtension{}
-	}
-
 	if opts.Roots == nil {
 		opts.Roots = systemRootsPool()
 		if opts.Roots == nil {
diff --git a/src/crypto/x509/verify_test.go b/src/crypto/x509/verify_test.go
index 15c4091444..63661348ee 100644
--- a/src/crypto/x509/verify_test.go
+++ b/src/crypto/x509/verify_test.go
@@ -263,6 +263,30 @@ var verifyTests = []verifyTest{
 
 		errorCallback: expectSubjectIssuerMismatcthError,
 	},
+	{
+		// Test that unknown critical extensions in a leaf cause a
+		// verify error.
+		leaf:          criticalExtLeafWithExt,
+		dnsName:       "example.com",
+		intermediates: []string{criticalExtIntermediate},
+		roots:         []string{criticalExtRoot},
+		currentTime:   1486684488,
+		systemSkip:    true,
+
+		errorCallback: expectUnhandledCriticalExtension,
+	},
+	{
+		// Test that unknown critical extensions in an intermediate
+		// cause a verify error.
+		leaf:          criticalExtLeaf,
+		dnsName:       "example.com",
+		intermediates: []string{criticalExtIntermediateWithExt},
+		roots:         []string{criticalExtRoot},
+		currentTime:   1486684488,
+		systemSkip:    true,
+
+		errorCallback: expectUnhandledCriticalExtension,
+	},
 }
 
 func expectHostnameError(t *testing.T, i int, err error) (ok bool) {
@@ -330,6 +354,14 @@ func expectSubjectIssuerMismatcthError(t *testing.T, i int, err error) (ok bool)
 	return true
 }
 
+func expectUnhandledCriticalExtension(t *testing.T, i int, err error) (ok bool) {
+	if _, ok := err.(UnhandledCriticalExtension); !ok {
+		t.Errorf("#%d: error was not an UnhandledCriticalExtension: %s", i, err)
+		return false
+	}
+	return true
+}
+
 func certificateFromPEM(pemBytes string) (*Certificate, error) {
 	block, _ := pem.Decode([]byte(pemBytes))
 	if block == nil {
@@ -1379,3 +1411,67 @@ w67CoNRb81dy+4Q1lGpA8ORoLWh5fIq2t2eNGc4qB8vlTIKiESzAwu7u3sRfuWQi
 4R+gnfLd37FWflMHwztFbVTuNtPOljCX0LN7KcuoXYlr05RhQrmoN7fQHsrZMNLs
 8FVjHdKKu+uPstwd04Uy4BR/H2y1yerN9j/L6ZkMl98iiA==
 -----END CERTIFICATE-----`
+
+const criticalExtRoot = `-----BEGIN CERTIFICATE-----
+MIIBqzCCAVGgAwIBAgIJAJ+mI/85cXApMAoGCCqGSM49BAMCMB0xDDAKBgNVBAoT
+A09yZzENMAsGA1UEAxMEUm9vdDAeFw0xNTAxMDEwMDAwMDBaFw0yNTAxMDEwMDAw
+MDBaMB0xDDAKBgNVBAoTA09yZzENMAsGA1UEAxMEUm9vdDBZMBMGByqGSM49AgEG
+CCqGSM49AwEHA0IABJGp9joiG2QSQA+1FczEDAsWo84rFiP3GTL+n+ugcS6TyNib
+gzMsdbJgVi+a33y0SzLZxB+YvU3/4KTk8yKLC+2jejB4MA4GA1UdDwEB/wQEAwIC
+BDAdBgNVHSUEFjAUBggrBgEFBQcDAQYIKwYBBQUHAwIwDwYDVR0TAQH/BAUwAwEB
+/zAZBgNVHQ4EEgQQQDfXAftAL7gcflQEJ4xZATAbBgNVHSMEFDASgBBAN9cB+0Av
+uBx+VAQnjFkBMAoGCCqGSM49BAMCA0gAMEUCIFeSV00fABFceWR52K+CfIgOHotY
+FizzGiLB47hGwjMuAiEA8e0um2Kr8FPQ4wmFKaTRKHMaZizCGl3m+RG5QsE1KWo=
+-----END CERTIFICATE-----`
+
+const criticalExtIntermediate = `-----BEGIN CERTIFICATE-----
+MIIBszCCAVmgAwIBAgIJAL2kcGZKpzVqMAoGCCqGSM49BAMCMB0xDDAKBgNVBAoT
+A09yZzENMAsGA1UEAxMEUm9vdDAeFw0xNTAxMDEwMDAwMDBaFw0yNTAxMDEwMDAw
+MDBaMCUxDDAKBgNVBAoTA09yZzEVMBMGA1UEAxMMSW50ZXJtZWRpYXRlMFkwEwYH
+KoZIzj0CAQYIKoZIzj0DAQcDQgAESqVq92iPEq01cL4o99WiXDc5GZjpjNlzMS1n
+rk8oHcVDp4tQRRQG3F4A6dF1rn/L923ha3b0fhDLlAvXZB+7EKN6MHgwDgYDVR0P
+AQH/BAQDAgIEMB0GA1UdJQQWMBQGCCsGAQUFBwMBBggrBgEFBQcDAjAPBgNVHRMB
+Af8EBTADAQH/MBkGA1UdDgQSBBCMGmiotXbbXVd7H40UsgajMBsGA1UdIwQUMBKA
+EEA31wH7QC+4HH5UBCeMWQEwCgYIKoZIzj0EAwIDSAAwRQIhAOhhNRb6KV7h3wbE
+cdap8bojzvUcPD78fbsQPCNw1jPxAiBOeAJhlTwpKn9KHpeJphYSzydj9NqcS26Y
+xXbdbm27KQ==
+-----END CERTIFICATE-----`
+
+const criticalExtLeafWithExt = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+const criticalExtIntermediateWithExt = `-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----`
+
+const criticalExtLeaf = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
diff --git a/src/crypto/x509/x509_test.go b/src/crypto/x509/x509_test.go
index b085dad90f..5e81e9ff5a 100644
--- a/src/crypto/x509/x509_test.go
+++ b/src/crypto/x509/x509_test.go
@@ -518,74 +518,6 @@ func TestCreateSelfSignedCertificate(t *testing.T) {
 	}
 }
 
-func TestUnknownCriticalExtension(t *testing.T) {
-	priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
-	if err != nil {
-		t.Fatalf("Failed to generate ECDSA key: %s", err)
-	}
-
-	oids := []asn1.ObjectIdentifier{
-		// This OID is in the PKIX arc, but unknown.
-		{2, 5, 29, 999999},
-		// This is a nonsense, unassigned OID.
-		{1, 2, 3, 4},
-	}
-
-	for _, oid := range oids {
-		template := Certificate{
-			SerialNumber: big.NewInt(1),
-			Subject: pkix.Name{
-				CommonName: "foo",
-			},
-			NotBefore: time.Unix(1000, 0),
-			NotAfter:  time.Now().AddDate(1, 0, 0),
-
-			BasicConstraintsValid: true,
-			IsCA: true,
-
-			KeyUsage:    KeyUsageCertSign,
-			ExtKeyUsage: []ExtKeyUsage{ExtKeyUsageServerAuth},
-
-			ExtraExtensions: []pkix.Extension{
-				{
-					Id:       oid,
-					Critical: true,
-					Value:    nil,
-				},
-			},
-		}
-
-		derBytes, err := CreateCertificate(rand.Reader, &template, &template, &priv.PublicKey, priv)
-		if err != nil {
-			t.Fatalf("failed to create certificate: %s", err)
-		}
-
-		cert, err := ParseCertificate(derBytes)
-		if err != nil {
-			t.Fatalf("Certificate with unknown critical extension was not parsed: %s", err)
-		}
-
-		roots := NewCertPool()
-		roots.AddCert(cert)
-
-		// Setting Roots ensures that Verify won't delegate to the OS
-		// library and thus the correct error should always be
-		// returned.
-		_, err = cert.Verify(VerifyOptions{Roots: roots})
-		if err == nil {
-			t.Fatal("Certificate with unknown critical extension was verified without error")
-		}
-		if _, ok := err.(UnhandledCriticalExtension); !ok {
-			t.Fatalf("Error was %#v, but wanted one of type UnhandledCriticalExtension", err)
-		}
-
-		cert.UnhandledCriticalExtensions = nil
-		if _, err = cert.Verify(VerifyOptions{Roots: roots}); err != nil {
-			t.Errorf("Certificate failed to verify after unhandled critical extensions were cleared: %s", err)
-		}
-	}
-}
-
 // Self-signed certificate using ECDSA with SHA1 & secp256r1
 var ecdsaSHA1CertPem = `
 -----BEGIN CERTIFICATE-----