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crypto/x509: provide better error messages for X.509 verify failures.

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Failures caused by errors like invalid signatures or missing hash
functions cause rather generic, unhelpful error messages because no
trust chain can be constructed: "x509: certificate signed by unknown
authority."

With this change, authority errors may contain the reason why an
arbitary candidate step in the chain was rejected. For example, in the
event of a missing hash function the error looks like:

x509: certificate signed by unknown authority (possibly because of
"crypto/x509: cannot verify signature: algorithm unimplemented" while
trying to verify candidate authority certificate 'Thawte SGC CA')

Fixes 5058.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/9104051
This commit is contained in:
Adam Langley 2013-05-20 14:20:26 -04:00
parent 910bd157c9
commit b419e2b57c
4 changed files with 130 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
src/pkg/crypto/x509/cert_pool.go
View File

@ -25,9 +25,10 @@ func NewCertPool() *CertPool {
}
// findVerifiedParents attempts to find certificates in s which have signed the
// given certificate. If no such certificate can be found or the signature
// doesn't match, it returns nil.
func (s *CertPool) findVerifiedParents(cert *Certificate) (parents []int) {
// given certificate. If any candidates were rejected then errCert will be set
// to one of them, arbitrarily, and err will contain the reason that it was
// rejected.
func (s *CertPool) findVerifiedParents(cert *Certificate) (parents []int, errCert *Certificate, err error) {
if s == nil {
return
}
@ -41,8 +42,10 @@ func (s *CertPool) findVerifiedParents(cert *Certificate) (parents []int) {
}
for _, c := range candidates {
if cert.CheckSignatureFrom(s.certs[c]) == nil {
if err = cert.CheckSignatureFrom(s.certs[c]); err == nil {
parents = append(parents, c)
} else {
errCert = s.certs[c]
}
}

6
src/pkg/crypto/x509/root_windows.go
View File

@ -89,7 +89,7 @@ func checkChainTrustStatus(c *Certificate, chainCtx *syscall.CertChainContext) e
case syscall.CERT_TRUST_IS_NOT_TIME_VALID:
return CertificateInvalidError{c, Expired}
default:
return UnknownAuthorityError{c}
return UnknownAuthorityError{c, nil, nil}
}
}
return nil
@ -129,9 +129,9 @@ func checkChainSSLServerPolicy(c *Certificate, chainCtx *syscall.CertChainContex
case syscall.CERT_E_CN_NO_MATCH:
return HostnameError{c, opts.DNSName}
case syscall.CERT_E_UNTRUSTEDROOT:
return UnknownAuthorityError{c}
return UnknownAuthorityError{c, nil, nil}
default:
return UnknownAuthorityError{c}
return UnknownAuthorityError{c, nil, nil}
}
}

34
src/pkg/crypto/x509/verify.go
View File

@ -5,6 +5,7 @@
package x509
import (
"fmt"
"net"
"runtime"
"strings"
@ -91,10 +92,27 @@ func (h HostnameError) Error() string {
// UnknownAuthorityError results when the certificate issuer is unknown
type UnknownAuthorityError struct {
cert *Certificate
// hintErr contains an error that may be helpful in determining why an
// authority wasn't found.
hintErr error
// hintCert contains a possible authority certificate that was rejected
// because of the error in hintErr.
hintCert *Certificate
}
func (e UnknownAuthorityError) Error() string {
return "x509: certificate signed by unknown authority"
s := "x509: certificate signed by unknown authority"
if e.hintErr != nil {
certName := e.hintCert.Subject.CommonName
if len(certName) == 0 {
if len(e.hintCert.Subject.Organization) > 0 {
certName = e.hintCert.Subject.Organization[0]
}
certName = "serial:" + e.hintCert.SerialNumber.String()
}
s += fmt.Sprintf(" (possibly because of %q while trying to verify candidate authority certificate %q)", e.hintErr, certName)
}
return s
}
// SystemRootsError results when we fail to load the system root certificates.
@ -249,7 +267,8 @@ func appendToFreshChain(chain []*Certificate, cert *Certificate) []*Certificate
}
func (c *Certificate) buildChains(cache map[int][][]*Certificate, currentChain []*Certificate, opts *VerifyOptions) (chains [][]*Certificate, err error) {
for _, rootNum := range opts.Roots.findVerifiedParents(c) {
possibleRoots, failedRoot, rootErr := opts.Roots.findVerifiedParents(c)
for _, rootNum := range possibleRoots {
root := opts.Roots.certs[rootNum]
err = root.isValid(rootCertificate, currentChain, opts)
if err != nil {
@ -258,8 +277,9 @@ func (c *Certificate) buildChains(cache map[int][][]*Certificate, currentChain [
chains = append(chains, appendToFreshChain(currentChain, root))
}
possibleIntermediates, failedIntermediate, intermediateErr := opts.Intermediates.findVerifiedParents(c)
nextIntermediate:
for _, intermediateNum := range opts.Intermediates.findVerifiedParents(c) {
for _, intermediateNum := range possibleIntermediates {
intermediate := opts.Intermediates.certs[intermediateNum]
for _, cert := range currentChain {
if cert == intermediate {
@ -284,7 +304,13 @@ nextIntermediate:
}
if len(chains) == 0 && err == nil {
err = UnknownAuthorityError{c}
hintErr := rootErr
hintCert := failedRoot
if hintErr == nil {
hintErr = intermediateErr
hintCert = failedIntermediate
}
err = UnknownAuthorityError{c, hintErr, hintCert}
}
return

90
src/pkg/crypto/x509/verify_test.go
View File

@ -126,6 +126,18 @@ var verifyTests = []verifyTest{
{"dnssec-exp", "StartCom Class 1", "StartCom Certification Authority", "StartCom Certification Authority"},
},
},
{
leaf: googleLeafWithInvalidHash,
intermediates: []string{thawteIntermediate},
roots: []string{verisignRoot},
currentTime: 1302726541,
dnsName: "www.google.com",
// The specific error message may not occur when using system
// verification.
systemSkip: true,
errorCallback: expectHashError,
},
{
// The default configuration should reject an S/MIME chain.
leaf: smimeLeaf,
@ -213,6 +225,18 @@ func expectSystemRootsError(t *testing.T, i int, err error) bool {
return true
}
func expectHashError(t *testing.T, i int, err error) bool {
if err == nil {
t.Errorf("#%d: no error resulted from invalid hash", i)
return false
}
if expected := "algorithm unimplemented"; !strings.Contains(err.Error(), expected) {
t.Errorf("#%d: error resulting from invalid hash didn't contain '%s', rather it was: %s", i, expected, err)
return false
}
return true
}
func certificateFromPEM(pemBytes string) (*Certificate, error) {
block, _ := pem.Decode([]byte(pemBytes))
if block == nil {
@ -400,6 +424,28 @@ u2ONgJd8IyAPkU0Wueru9G2Jysa9zCRo1kNbzipYvzwY4OA8Ys+WAi0oR1A04Se6
z5nRUP8pJcA2NhUzUnC+MY+f6H/nEQyNv4SgQhqAibAxWEEHXw==
-----END CERTIFICATE-----`
// googleLeafWithInvalidHash is the same as googleLeaf, but the signature
// algorithm in the certificate contains a nonsense OID.
const googleLeafWithInvalidHash = `-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----`
const dnssecExpLeaf = `-----BEGIN CERTIFICATE-----
MIIGzTCCBbWgAwIBAgIDAdD6MA0GCSqGSIb3DQEBBQUAMIGMMQswCQYDVQQGEwJJ
TDEWMBQGA1UEChMNU3RhcnRDb20gTHRkLjErMCkGA1UECxMiU2VjdXJlIERpZ2l0
@ -522,6 +568,50 @@ um0ABj6y6koQOdjQK/W/7HW/lwLFCRsI3FU34oH7N4RDYiDK51ZLZer+bMEkkySh
NOsF/5oirpt9P/FlUQqmMGqz9IgcgA38corog14=
-----END CERTIFICATE-----`
const startComRootSHA256 = `-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----`
const smimeLeaf = `-----BEGIN CERTIFICATE-----
MIIFBjCCA+6gAwIBAgISESFvrjT8XcJTEe6rBlPptILlMA0GCSqGSIb3DQEBBQUA
MFQxCzAJBgNVBAYTAkJFMRkwFwYDVQQKExBHbG9iYWxTaWduIG52LXNhMSowKAYD