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//
// Copyright 2021 The Sigstore Authors.
//
// 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 signature
import (
"crypto"
"crypto/ecdsa"
"crypto/ed25519"
"crypto/rsa"
"errors"
"io"
"os"
"path/filepath"
"github.com/sigstore/sigstore/pkg/cryptoutils"
"github.com/sigstore/sigstore/pkg/signature/options"
)
// Verifier verifies the digital signature using a specified public key
type Verifier interface {
PublicKeyProvider
VerifySignature(signature, message io.Reader, opts ...VerifyOption) error
}
// LoadVerifier returns a signature.Verifier based on the algorithm of the public key
// provided that will use the hash function specified when computing digests.
//
// If publicKey is an RSA key, a RSAPKCS1v15Verifier will be returned. If a
// RSAPSSVerifier is desired instead, use the LoadRSAPSSVerifier() method directly.
func LoadVerifier(publicKey crypto.PublicKey, hashFunc crypto.Hash) (Verifier, error) {
return LoadVerifierWithOpts(publicKey, options.WithHash(hashFunc))
}
// LoadVerifierWithOpts returns a signature.Verifier based on the algorithm of the public key
// provided that will use the hash function specified when computing digests.
func LoadVerifierWithOpts(publicKey crypto.PublicKey, opts ...LoadOption) (Verifier, error) {
var rsaPSSOptions *rsa.PSSOptions
var useED25519ph bool
hashFunc := crypto.SHA256
for _, o := range opts {
o.ApplyED25519ph(&useED25519ph)
o.ApplyHash(&hashFunc)
o.ApplyRSAPSS(&rsaPSSOptions)
}
switch pk := publicKey.(type) {
case *rsa.PublicKey:
if rsaPSSOptions != nil {
return LoadRSAPSSVerifier(pk, hashFunc, rsaPSSOptions)
}
return LoadRSAPKCS1v15Verifier(pk, hashFunc)
case *ecdsa.PublicKey:
return LoadECDSAVerifier(pk, hashFunc)
case ed25519.PublicKey:
if useED25519ph {
return LoadED25519phVerifier(pk)
}
return LoadED25519Verifier(pk)
}
return nil, errors.New("unsupported public key type")
}
// LoadUnsafeVerifier returns a signature.Verifier based on the algorithm of the public key
// provided that will use SHA1 when computing digests for RSA and ECDSA signatures.
//
// If publicKey is an RSA key, a RSAPKCS1v15Verifier will be returned. If a
// RSAPSSVerifier is desired instead, use the LoadRSAPSSVerifier() method directly.
func LoadUnsafeVerifier(publicKey crypto.PublicKey) (Verifier, error) {
switch pk := publicKey.(type) {
case *rsa.PublicKey:
if pk == nil {
return nil, errors.New("invalid RSA public key specified")
}
return &RSAPKCS1v15Verifier{
publicKey: pk,
hashFunc: crypto.SHA1,
}, nil
case *ecdsa.PublicKey:
if pk == nil {
return nil, errors.New("invalid ECDSA public key specified")
}
return &ECDSAVerifier{
publicKey: pk,
hashFunc: crypto.SHA1,
}, nil
case ed25519.PublicKey:
return LoadED25519Verifier(pk)
}
return nil, errors.New("unsupported public key type")
}
// LoadVerifierFromPEMFile returns a signature.Verifier based on the contents of a
// file located at path. The Verifier wil use the hash function specified when computing digests.
//
// If the publickey is an RSA key, a RSAPKCS1v15Verifier will be returned. If a
// RSAPSSVerifier is desired instead, use the LoadRSAPSSVerifier() and cryptoutils.UnmarshalPEMToPublicKey() methods directly.
func LoadVerifierFromPEMFile(path string, hashFunc crypto.Hash) (Verifier, error) {
fileBytes, err := os.ReadFile(filepath.Clean(path))
if err != nil {
return nil, err
}
pubKey, err := cryptoutils.UnmarshalPEMToPublicKey(fileBytes)
if err != nil {
return nil, err
}
return LoadVerifier(pubKey, hashFunc)
}
// LoadVerifierFromPEMFileWithOpts returns a signature.Verifier based on the contents of a
// file located at path. The Verifier wil use the hash function specified in the options when computing digests.
func LoadVerifierFromPEMFileWithOpts(path string, opts ...LoadOption) (Verifier, error) {
fileBytes, err := os.ReadFile(filepath.Clean(path))
if err != nil {
return nil, err
}
pubKey, err := cryptoutils.UnmarshalPEMToPublicKey(fileBytes)
if err != nil {
return nil, err
}
return LoadVerifierWithOpts(pubKey, opts...)
}
// LoadDefaultVerifier returns a signature.Verifier based on the public key.
// Each public key has a corresponding PublicKeyDetails associated in the
// Sigstore ecosystem, see Algorithm Registry for more details.
func LoadDefaultVerifier(publicKey crypto.PublicKey, opts ...LoadOption) (Verifier, error) {
algorithmDetails, err := GetDefaultAlgorithmDetails(publicKey, opts...)
if err != nil {
return nil, err
}
return LoadVerifierFromAlgorithmDetails(publicKey, algorithmDetails, opts...)
}
// LoadVerifierFromAlgorithmDetails returns a signature.Verifier based on
// the algorithm details and the user's choice of options.
func LoadVerifierFromAlgorithmDetails(publicKey crypto.PublicKey, algorithmDetails AlgorithmDetails, opts ...LoadOption) (Verifier, error) {
filteredOpts := GetOptsFromAlgorithmDetails(algorithmDetails, opts...)
return LoadVerifierWithOpts(publicKey, filteredOpts...)
}
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