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/*-
* Copyright 2018 Square Inc.
*
* 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 cryptosigner implements an OpaqueSigner that wraps a "crypto".Signer
//
// https://godoc.org/crypto#Signer
package cryptosigner
import (
"crypto"
"crypto/ecdsa"
"crypto/ed25519"
"crypto/elliptic"
"crypto/rand"
"crypto/rsa"
"encoding/asn1"
"io"
"math/big"
"github.com/go-jose/go-jose/v4"
)
// Opaque creates an OpaqueSigner from a "crypto".Signer
func Opaque(s crypto.Signer) jose.OpaqueSigner {
pk := &jose.JSONWebKey{
Key: s.Public(),
}
return &cryptoSigner{signer: s, rand: rand.Reader, pk: pk}
}
type cryptoSigner struct {
pk *jose.JSONWebKey
signer crypto.Signer
rand io.Reader
}
func (s *cryptoSigner) Public() *jose.JSONWebKey {
return s.pk
}
func (s *cryptoSigner) Algs() []jose.SignatureAlgorithm {
switch key := s.signer.Public().(type) {
case ed25519.PublicKey:
return []jose.SignatureAlgorithm{jose.EdDSA}
case *ecdsa.PublicKey:
switch key.Curve {
case elliptic.P256():
return []jose.SignatureAlgorithm{jose.ES256}
case elliptic.P384():
return []jose.SignatureAlgorithm{jose.ES384}
case elliptic.P521():
return []jose.SignatureAlgorithm{jose.ES512}
default:
return nil
}
case *rsa.PublicKey:
return []jose.SignatureAlgorithm{jose.RS256, jose.RS384, jose.RS512, jose.PS256, jose.PS384, jose.PS512}
default:
return nil
}
}
func (s *cryptoSigner) SignPayload(payload []byte, alg jose.SignatureAlgorithm) ([]byte, error) {
var hash crypto.Hash
switch alg {
case jose.EdDSA:
case jose.RS256, jose.PS256, jose.ES256:
hash = crypto.SHA256
case jose.RS384, jose.PS384, jose.ES384:
hash = crypto.SHA384
case jose.RS512, jose.PS512, jose.ES512:
hash = crypto.SHA512
default:
return nil, jose.ErrUnsupportedAlgorithm
}
var hashed []byte
if hash != crypto.Hash(0) {
hasher := hash.New()
if _, err := hasher.Write(payload); err != nil {
return nil, err
}
hashed = hasher.Sum(nil)
}
var (
out []byte
err error
)
switch alg {
case jose.EdDSA:
out, err = s.signer.Sign(s.rand, payload, crypto.Hash(0))
case jose.ES256, jose.ES384, jose.ES512:
var byteLen int
switch alg {
case jose.ES256:
byteLen = 32
case jose.ES384:
byteLen = 48
case jose.ES512:
byteLen = 66
}
var b []byte
b, err = s.signer.Sign(s.rand, hashed, hash)
if err != nil {
return nil, err
}
sig := struct {
R, S *big.Int
}{}
if _, err = asn1.Unmarshal(b, &sig); err != nil {
return nil, err
}
rBytes := sig.R.Bytes()
out = make([]byte, byteLen)
copy(out[byteLen-len(rBytes):], rBytes)
sBytes := sig.S.Bytes()
sBytesPadded := make([]byte, byteLen)
copy(sBytesPadded[byteLen-len(sBytes):], sBytes)
out = append(out, sBytesPadded...)
case jose.RS256, jose.RS384, jose.RS512:
out, err = s.signer.Sign(s.rand, hashed, hash)
case jose.PS256, jose.PS384, jose.PS512:
out, err = s.signer.Sign(s.rand, hashed, &rsa.PSSOptions{
SaltLength: rsa.PSSSaltLengthAuto,
Hash: hash,
})
}
return out, err
}
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