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crypto/x509: bypass signature verification in CreateCertificate when using MD5WithRSA

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Bypasses the signature verification check we previously added if the
signature algorithm is MD5WithRSA, as we only support this algorithm
for signing and not verification.

Change-Id: Idba6dbba8b365d6199d467526746b88a5f734af1
Reviewed-on: https://go-review.googlesource.com/c/go/+/264019
Run-TryBot: Roland Shoemaker <roland@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
Trust: Roland Shoemaker <roland@golang.org>
This commit is contained in:
Roland Shoemaker 2020-10-20 13:50:52 -07:00 committed by Roland Shoemaker
parent 6f45b39e4d
commit b04eb73a68
2 changed files with 22 additions and 2 deletions
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6
src/crypto/x509/x509.go
View File

@ -2156,9 +2156,13 @@ func CreateCertificate(rand io.Reader, template, parent *Certificate, pub, priv
} }
// Check the signature to ensure the crypto.Signer behaved correctly. // Check the signature to ensure the crypto.Signer behaved correctly.
if err := checkSignature(getSignatureAlgorithmFromAI(signatureAlgorithm), c.Raw, signature, key.Public()); err != nil { // We skip this check if the signature algorithm is MD5WithRSA as we
// only support this algorithm for signing, and not verification.
if sigAlg := getSignatureAlgorithmFromAI(signatureAlgorithm); sigAlg != MD5WithRSA {
if err := checkSignature(sigAlg, c.Raw, signature, key.Public()); err != nil {
return nil, fmt.Errorf("x509: signature over certificate returned by signer is invalid: %w", err) return nil, fmt.Errorf("x509: signature over certificate returned by signer is invalid: %w", err)
} }
}
return signedCert, nil return signedCert, nil
} }

16
src/crypto/x509/x509_test.go
View File

@ -2896,3 +2896,19 @@ func TestCreateCertificateBrokenSigner(t *testing.T) {
t.Fatalf("CreateCertificate returned an unexpected error: got %q, want %q", err, expectedErr) t.Fatalf("CreateCertificate returned an unexpected error: got %q, want %q", err, expectedErr)
} }
} }
func TestCreateCertificateMD5(t *testing.T) {
template := &Certificate{
SerialNumber: big.NewInt(10),
DNSNames: []string{"example.com"},
SignatureAlgorithm: MD5WithRSA,
}
k, err := rsa.GenerateKey(rand.Reader, 1024)
if err != nil {
t.Fatalf("failed to generate test key: %s", err)
}
_, err = CreateCertificate(rand.Reader, template, template, k.Public(), &brokenSigner{k.Public()})
if err != nil {
t.Fatalf("CreateCertificate failed when SignatureAlgorithm = MD5WithRSA: %s", err)
}
}