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crypto/x509: ignore CN if SAN extension present. 

The code previously tested only whether DNS-name SANs were present in a
certificate which is only approximately correct. In fact, /any/ SAN
extension, including one with no DNS names, should cause the CN to be
ignored.

Change-Id: I3d9824918975be6d4817e7cbb48ed1b0c5a2fc8b
Reviewed-on: https://go-review.googlesource.com/36696
Run-TryBot: Adam Langley <agl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Adam Langley 2017-02-09 15:57:53 -08:00
parent a524616860
commit 630e93ed2d
3 changed files with 62 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
src/crypto/x509/verify.go
View File

@ -87,7 +87,7 @@ func (h HostnameError) Error() string {
valid += san.String()
}
} else {
if len(c.DNSNames) > 0 {
if c.hasSANExtension() {
valid = strings.Join(c.DNSNames, ", ")
} else {
valid = c.Subject.CommonName
@ -482,7 +482,7 @@ func (c *Certificate) VerifyHostname(h string) error {
lowered := toLowerCaseASCII(h)
if len(c.DNSNames) > 0 {
if c.hasSANExtension() {
for _, match := range c.DNSNames {
if matchHostnames(toLowerCaseASCII(match), lowered) {
return nil

56
src/crypto/x509/verify_test.go
View File

@ -274,6 +274,17 @@ var verifyTests = []verifyTest{
errorCallback: expectNotAuthorizedError,
},
{
// If any SAN extension is present (even one without any DNS
// names), the CN should be ignored.
leaf: ignoreCNWithSANLeaf,
dnsName: "foo.example.com",
roots: []string{ignoreCNWithSANRoot},
currentTime: 1486684488,
systemSkip: true,
errorCallback: expectHostnameError,
},
}
func expectHostnameError(t *testing.T, i int, err error) (ok bool) {
@ -1334,6 +1345,51 @@ CwUAA4GBADYzYUvaToO/ucBskPdqXV16AaakIhhSENswYVSl97/sODaxsjishKq9
/jt8qszOXCv2vYdUTPNuPqufXLWMoirpuXrr1liJDmedCcAHepY/
-----END CERTIFICATE-----`
const ignoreCNWithSANRoot = `
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----`
const ignoreCNWithSANLeaf = `
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----`
var unknownAuthorityErrorTests = []struct {
cert string
expected string

4
src/crypto/x509/x509.go
View File

@ -723,6 +723,10 @@ func (c *Certificate) Equal(other *Certificate) bool {
return bytes.Equal(c.Raw, other.Raw)
}
func (c *Certificate) hasSANExtension() bool {
return oidInExtensions(oidExtensionSubjectAltName, c.Extensions)
}
// Entrust have a broken root certificate (CN=Entrust.net Certification
// Authority (2048)) which isn't marked as a CA certificate and is thus invalid
// according to PKIX.