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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"
// these ensure we have the implementations loaded
_ "crypto/sha256"
_ "crypto/sha512"
"github.com/sigstore/sigstore/pkg/cryptoutils"
"github.com/sigstore/sigstore/pkg/signature/options"
// these ensure we have the implementations loaded
_ "golang.org/x/crypto/sha3"
)
// Signer creates digital signatures over a message using a specified key pair
type Signer interface {
PublicKeyProvider
SignMessage(message io.Reader, opts ...SignOption) ([]byte, error)
}
// SignerOpts implements crypto.SignerOpts but also allows callers to specify
// additional options that may be utilized in signing the digest provided.
type SignerOpts struct {
Hash crypto.Hash
Opts []SignOption
}
// HashFunc returns the hash function for this object
func (s SignerOpts) HashFunc() crypto.Hash {
return s.Hash
}
// LoadSigner returns a signature.Signer based on the algorithm of the private key
// provided.
//
// If privateKey is an RSA key, a RSAPKCS1v15Signer will be returned. If a
// RSAPSSSigner is desired instead, use the LoadRSAPSSSigner() method directly.
func LoadSigner(privateKey crypto.PrivateKey, hashFunc crypto.Hash) (Signer, error) {
return LoadSignerWithOpts(privateKey, options.WithHash(hashFunc))
}
// LoadSignerWithOpts returns a signature.Signer based on the algorithm of the private key
// provided.
func LoadSignerWithOpts(privateKey crypto.PrivateKey, opts ...LoadOption) (Signer, 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 := privateKey.(type) {
case *rsa.PrivateKey:
if rsaPSSOptions != nil {
return LoadRSAPSSSigner(pk, hashFunc, rsaPSSOptions)
}
return LoadRSAPKCS1v15Signer(pk, hashFunc)
case *ecdsa.PrivateKey:
return LoadECDSASigner(pk, hashFunc)
case ed25519.PrivateKey:
if useED25519ph {
return LoadED25519phSigner(pk)
}
return LoadED25519Signer(pk)
}
return nil, errors.New("unsupported public key type")
}
// LoadSignerFromPEMFile returns a signature.Signer based on the algorithm of the private key
// in the file. The Signer will use the hash function specified when computing digests.
//
// If key is an RSA key, a RSAPKCS1v15Signer will be returned. If a
// RSAPSSSigner is desired instead, use the LoadRSAPSSSigner() and
// cryptoutils.UnmarshalPEMToPrivateKey() methods directly.
func LoadSignerFromPEMFile(path string, hashFunc crypto.Hash, pf cryptoutils.PassFunc) (Signer, error) {
fileBytes, err := os.ReadFile(filepath.Clean(path))
if err != nil {
return nil, err
}
priv, err := cryptoutils.UnmarshalPEMToPrivateKey(fileBytes, pf)
if err != nil {
return nil, err
}
return LoadSigner(priv, hashFunc)
}
// LoadSignerFromPEMFileWithOpts returns a signature.Signer based on the algorithm of the private key
// in the file. The Signer will use the hash function specified in the options when computing digests.
func LoadSignerFromPEMFileWithOpts(path string, pf cryptoutils.PassFunc, opts ...LoadOption) (Signer, error) {
fileBytes, err := os.ReadFile(filepath.Clean(path))
if err != nil {
return nil, err
}
priv, err := cryptoutils.UnmarshalPEMToPrivateKey(fileBytes, pf)
if err != nil {
return nil, err
}
return LoadSignerWithOpts(priv, opts...)
}
// LoadDefaultSigner returns a signature.Signer based on the private key.
// Each private key has a corresponding PublicKeyDetails associated in the
// Sigstore ecosystem, see Algorithm Registry for more details.
func LoadDefaultSigner(privateKey crypto.PrivateKey, opts ...LoadOption) (Signer, error) {
signer, ok := privateKey.(crypto.Signer)
if !ok {
return nil, errors.New("private key does not implement signature.Signer")
}
algorithmDetails, err := GetDefaultAlgorithmDetails(signer.Public(), opts...)
if err != nil {
return nil, err
}
return LoadSignerFromAlgorithmDetails(privateKey, algorithmDetails, opts...)
}
// LoadSignerFromAlgorithmDetails returns a signature.Signer based on
// the algorithm details and the user's choice of options.
func LoadSignerFromAlgorithmDetails(privateKey crypto.PrivateKey, algorithmDetails AlgorithmDetails, opts ...LoadOption) (Signer, error) {
filteredOpts := GetOptsFromAlgorithmDetails(algorithmDetails, opts...)
return LoadSignerWithOpts(privateKey, filteredOpts...)
}
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