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verify.go
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verify.go
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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 ssh
import (
"io"
"github.com/sigstore/sigstore/pkg/signature"
"golang.org/x/crypto/ssh"
)
// Verify verifies the supplied signature against the specified key.
func Verify(message io.Reader, armoredSignature []byte, pubKey ssh.PublicKey) error {
decodedSignature, err := Decode(armoredSignature)
if err != nil {
return err
}
// Hash the message so we can verify it against the signature.
h := supportedHashAlgorithms[decodedSignature.hashAlg]()
if _, err := io.Copy(h, message); err != nil {
return err
}
hm := h.Sum(nil)
toVerify := messageWrapper{
Namespace: "file",
HashAlgorithm: decodedSignature.hashAlg,
Hash: string(hm),
}
signedMessage := ssh.Marshal(toVerify)
signedMessage = append([]byte(magicHeader), signedMessage...)
return pubKey.Verify(signedMessage, decodedSignature.signature)
}
var _ signature.Verifier = (*Signer)(nil)
// VerifySignature verifies a suppled signature.
func (s *Signer) VerifySignature(signature, message io.Reader, opts ...signature.VerifyOption) error {
b, err := io.ReadAll(signature)
if err != nil {
return err
}
return Verify(message, b, s.signer.PublicKey())
}