vendor

vendor/github.com/google/certificate-transparency-go/tls/signature.go

@@ -0,0 +1,152 @@
+// Copyright 2016 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tls
+
+import (
+	"crypto"
+	"crypto/dsa"
+	"crypto/ecdsa"
+	_ "crypto/md5" // For registration side-effect
+	"crypto/rand"
+	"crypto/rsa"
+	_ "crypto/sha1"   // For registration side-effect
+	_ "crypto/sha256" // For registration side-effect
+	_ "crypto/sha512" // For registration side-effect
+	"errors"
+	"fmt"
+	"log"
+	"math/big"
+
+	"github.com/google/certificate-transparency-go/asn1"
+)
+
+type dsaSig struct {
+	R, S *big.Int
+}
+
+func generateHash(algo HashAlgorithm, data []byte) ([]byte, crypto.Hash, error) {
+	var hashType crypto.Hash
+	switch algo {
+	case MD5:
+		hashType = crypto.MD5
+	case SHA1:
+		hashType = crypto.SHA1
+	case SHA224:
+		hashType = crypto.SHA224
+	case SHA256:
+		hashType = crypto.SHA256
+	case SHA384:
+		hashType = crypto.SHA384
+	case SHA512:
+		hashType = crypto.SHA512
+	default:
+		return nil, hashType, fmt.Errorf("unsupported Algorithm.Hash in signature: %v", algo)
+	}
+
+	hasher := hashType.New()
+	if _, err := hasher.Write(data); err != nil {
+		return nil, hashType, fmt.Errorf("failed to write to hasher: %v", err)
+	}
+	return hasher.Sum([]byte{}), hashType, nil
+}
+
+// VerifySignature verifies that the passed in signature over data was created by the given PublicKey.
+func VerifySignature(pubKey crypto.PublicKey, data []byte, sig DigitallySigned) error {
+	hash, hashType, err := generateHash(sig.Algorithm.Hash, data)
+	if err != nil {
+		return err
+	}
+
+	switch sig.Algorithm.Signature {
+	case RSA:
+		rsaKey, ok := pubKey.(*rsa.PublicKey)
+		if !ok {
+			return fmt.Errorf("cannot verify RSA signature with %T key", pubKey)
+		}
+		if err := rsa.VerifyPKCS1v15(rsaKey, hashType, hash, sig.Signature); err != nil {
+			return fmt.Errorf("failed to verify rsa signature: %v", err)
+		}
+	case DSA:
+		dsaKey, ok := pubKey.(*dsa.PublicKey)
+		if !ok {
+			return fmt.Errorf("cannot verify DSA signature with %T key", pubKey)
+		}
+		var dsaSig dsaSig
+		rest, err := asn1.Unmarshal(sig.Signature, &dsaSig)
+		if err != nil {
+			return fmt.Errorf("failed to unmarshal DSA signature: %v", err)
+		}
+		if len(rest) != 0 {
+			log.Printf("Garbage following signature %v", rest)
+		}
+		if dsaSig.R.Sign() <= 0 || dsaSig.S.Sign() <= 0 {
+			return errors.New("DSA signature contained zero or negative values")
+		}
+		if !dsa.Verify(dsaKey, hash, dsaSig.R, dsaSig.S) {
+			return errors.New("failed to verify DSA signature")
+		}
+	case ECDSA:
+		ecdsaKey, ok := pubKey.(*ecdsa.PublicKey)
+		if !ok {
+			return fmt.Errorf("cannot verify ECDSA signature with %T key", pubKey)
+		}
+		var ecdsaSig dsaSig
+		rest, err := asn1.Unmarshal(sig.Signature, &ecdsaSig)
+		if err != nil {
+			return fmt.Errorf("failed to unmarshal ECDSA signature: %v", err)
+		}
+		if len(rest) != 0 {
+			log.Printf("Garbage following signature %v", rest)
+		}
+		if ecdsaSig.R.Sign() <= 0 || ecdsaSig.S.Sign() <= 0 {
+			return errors.New("ECDSA signature contained zero or negative values")
+		}
+
+		if !ecdsa.Verify(ecdsaKey, hash, ecdsaSig.R, ecdsaSig.S) {
+			return errors.New("failed to verify ECDSA signature")
+		}
+	default:
+		return fmt.Errorf("unsupported Algorithm.Signature in signature: %v", sig.Algorithm.Hash)
+	}
+	return nil
+}
+
+// CreateSignature builds a signature over the given data using the specified hash algorithm and private key.
+func CreateSignature(privKey crypto.PrivateKey, hashAlgo HashAlgorithm, data []byte) (DigitallySigned, error) {
+	var sig DigitallySigned
+	sig.Algorithm.Hash = hashAlgo
+	hash, hashType, err := generateHash(sig.Algorithm.Hash, data)
+	if err != nil {
+		return sig, err
+	}
+
+	switch privKey := privKey.(type) {
+	case rsa.PrivateKey:
+		sig.Algorithm.Signature = RSA
+		sig.Signature, err = rsa.SignPKCS1v15(rand.Reader, &privKey, hashType, hash)
+		return sig, err
+	case ecdsa.PrivateKey:
+		sig.Algorithm.Signature = ECDSA
+		var ecdsaSig dsaSig
+		ecdsaSig.R, ecdsaSig.S, err = ecdsa.Sign(rand.Reader, &privKey, hash)
+		if err != nil {
+			return sig, err
+		}
+		sig.Signature, err = asn1.Marshal(ecdsaSig)
+		return sig, err
+	default:
+		return sig, fmt.Errorf("unsupported private key type %T", privKey)
+	}
+}