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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 dsse
import (
"bytes"
"context"
"crypto"
"encoding/base64"
"encoding/json"
"io"
"github.com/secure-systems-lab/go-securesystemslib/dsse"
"github.com/sigstore/sigstore/pkg/signature"
)
// WrapSigner returns a signature.Signer that uses the DSSE encoding format
func WrapSigner(s signature.Signer, payloadType string) signature.Signer {
return &wrappedSigner{
s: s,
payloadType: payloadType,
}
}
type wrappedSigner struct {
s signature.Signer
payloadType string
}
// PublicKey returns the public key associated with the signer
func (w *wrappedSigner) PublicKey(opts ...signature.PublicKeyOption) (crypto.PublicKey, error) {
return w.s.PublicKey(opts...)
}
// SignMessage signs the provided stream in the reader using the DSSE encoding format
func (w *wrappedSigner) SignMessage(r io.Reader, opts ...signature.SignOption) ([]byte, error) {
p, err := io.ReadAll(r)
if err != nil {
return nil, err
}
pae := dsse.PAE(w.payloadType, p)
sig, err := w.s.SignMessage(bytes.NewReader(pae), opts...)
if err != nil {
return nil, err
}
env := dsse.Envelope{
PayloadType: w.payloadType,
Payload: base64.StdEncoding.EncodeToString(p),
Signatures: []dsse.Signature{
{
Sig: base64.StdEncoding.EncodeToString(sig),
},
},
}
return json.Marshal(env)
}
// WrapVerifier returns a signature.Verifier that uses the DSSE encoding format
func WrapVerifier(v signature.Verifier) signature.Verifier {
return &wrappedVerifier{
v: v,
}
}
type wrappedVerifier struct {
v signature.Verifier
}
// PublicKey returns the public key associated with the verifier
func (w *wrappedVerifier) PublicKey(opts ...signature.PublicKeyOption) (crypto.PublicKey, error) {
return w.v.PublicKey(opts...)
}
// VerifySignature verifies the signature specified in an DSSE envelope
func (w *wrappedVerifier) VerifySignature(s, _ io.Reader, _ ...signature.VerifyOption) error {
sig, err := io.ReadAll(s)
if err != nil {
return err
}
env := dsse.Envelope{}
if err := json.Unmarshal(sig, &env); err != nil {
return err
}
pub, err := w.PublicKey()
if err != nil {
return err
}
verifier, err := dsse.NewEnvelopeVerifier(&VerifierAdapter{
SignatureVerifier: w.v,
Pub: pub,
PubKeyID: "", // We do not want to limit verification to a specific key.
})
if err != nil {
return err
}
_, err = verifier.Verify(context.Background(), &env)
return err
}
// WrapSignerVerifier returns a signature.SignerVerifier that uses the DSSE encoding format
func WrapSignerVerifier(sv signature.SignerVerifier, payloadType string) signature.SignerVerifier {
signer := &wrappedSigner{
payloadType: payloadType,
s: sv,
}
verifier := &wrappedVerifier{
v: sv,
}
return &wrappedSignerVerifier{
signer: signer,
verifier: verifier,
}
}
type wrappedSignerVerifier struct {
signer *wrappedSigner
verifier *wrappedVerifier
}
// PublicKey returns the public key associated with the verifier
func (w *wrappedSignerVerifier) PublicKey(opts ...signature.PublicKeyOption) (crypto.PublicKey, error) {
return w.signer.PublicKey(opts...)
}
// VerifySignature verifies the signature specified in an DSSE envelope
func (w *wrappedSignerVerifier) VerifySignature(s, r io.Reader, opts ...signature.VerifyOption) error {
return w.verifier.VerifySignature(s, r, opts...)
}
// SignMessage signs the provided stream in the reader using the DSSE encoding format
func (w *wrappedSignerVerifier) SignMessage(r io.Reader, opts ...signature.SignOption) ([]byte, error) {
return w.signer.SignMessage(r, opts...)
}
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