102 lines
3.3 KiB
Go
102 lines
3.3 KiB
Go
// Copyright 2015 Google Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package ct
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import (
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"crypto"
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"crypto/ecdsa"
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"crypto/elliptic"
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"crypto/rsa"
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"crypto/sha256"
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"encoding/pem"
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"flag"
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"fmt"
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"log"
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"github.com/google/certificate-transparency-go/tls"
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"github.com/google/certificate-transparency-go/x509"
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)
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var allowVerificationWithNonCompliantKeys = flag.Bool("allow_verification_with_non_compliant_keys", false,
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"Allow a SignatureVerifier to use keys which are technically non-compliant with RFC6962.")
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// PublicKeyFromPEM parses a PEM formatted block and returns the public key contained within and any remaining unread bytes, or an error.
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func PublicKeyFromPEM(b []byte) (crypto.PublicKey, SHA256Hash, []byte, error) {
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p, rest := pem.Decode(b)
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if p == nil {
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return nil, [sha256.Size]byte{}, rest, fmt.Errorf("no PEM block found in %s", string(b))
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}
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k, err := x509.ParsePKIXPublicKey(p.Bytes)
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return k, sha256.Sum256(p.Bytes), rest, err
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}
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// SignatureVerifier can verify signatures on SCTs and STHs
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type SignatureVerifier struct {
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pubKey crypto.PublicKey
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}
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// NewSignatureVerifier creates a new SignatureVerifier using the passed in PublicKey.
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func NewSignatureVerifier(pk crypto.PublicKey) (*SignatureVerifier, error) {
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switch pkType := pk.(type) {
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case *rsa.PublicKey:
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if pkType.N.BitLen() < 2048 {
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e := fmt.Errorf("public key is RSA with < 2048 bits (size:%d)", pkType.N.BitLen())
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if !(*allowVerificationWithNonCompliantKeys) {
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return nil, e
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}
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log.Printf("WARNING: %v", e)
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}
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case *ecdsa.PublicKey:
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params := *(pkType.Params())
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if params != *elliptic.P256().Params() {
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e := fmt.Errorf("public is ECDSA, but not on the P256 curve")
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if !(*allowVerificationWithNonCompliantKeys) {
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return nil, e
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}
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log.Printf("WARNING: %v", e)
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}
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default:
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return nil, fmt.Errorf("Unsupported public key type %v", pkType)
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}
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return &SignatureVerifier{
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pubKey: pk,
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}, nil
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}
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// VerifySignature verifies the given signature sig matches the data.
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func (s SignatureVerifier) VerifySignature(data []byte, sig tls.DigitallySigned) error {
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return tls.VerifySignature(s.pubKey, data, sig)
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}
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// VerifySCTSignature verifies that the SCT's signature is valid for the given LogEntry.
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func (s SignatureVerifier) VerifySCTSignature(sct SignedCertificateTimestamp, entry LogEntry) error {
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sctData, err := SerializeSCTSignatureInput(sct, entry)
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if err != nil {
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return err
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}
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return s.VerifySignature(sctData, tls.DigitallySigned(sct.Signature))
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}
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// VerifySTHSignature verifies that the STH's signature is valid.
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func (s SignatureVerifier) VerifySTHSignature(sth SignedTreeHead) error {
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sthData, err := SerializeSTHSignatureInput(sth)
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if err != nil {
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return err
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}
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return s.VerifySignature(sthData, tls.DigitallySigned(sth.TreeHeadSignature))
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}
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