52 lines
1.6 KiB
Go
52 lines
1.6 KiB
Go
|
/*-
|
||
|
|
* Copyright 2014 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 josecipher
|
||
|
|
|
||
|
|
import (
|
||
|
|
"crypto"
|
||
|
|
"crypto/ecdsa"
|
||
|
|
"encoding/binary"
|
||
|
|
)
|
||
|
|
|
||
|
|
// DeriveECDHES derives a shared encryption key using ECDH/ConcatKDF as described in JWE/JWA.
|
||
|
|
func DeriveECDHES(alg string, apuData, apvData []byte, priv *ecdsa.PrivateKey, pub *ecdsa.PublicKey, size int) []byte {
|
||
|
|
// algId, partyUInfo, partyVInfo inputs must be prefixed with the length
|
||
|
|
algID := lengthPrefixed([]byte(alg))
|
||
|
|
ptyUInfo := lengthPrefixed(apuData)
|
||
|
|
ptyVInfo := lengthPrefixed(apvData)
|
||
|
|
|
||
|
|
// suppPubInfo is the encoded length of the output size in bits
|
||
|
|
supPubInfo := make([]byte, 4)
|
||
|
|
binary.BigEndian.PutUint32(supPubInfo, uint32(size)*8)
|
||
|
|
|
||
|
|
z, _ := priv.PublicKey.Curve.ScalarMult(pub.X, pub.Y, priv.D.Bytes())
|
||
|
|
reader := NewConcatKDF(crypto.SHA256, z.Bytes(), algID, ptyUInfo, ptyVInfo, supPubInfo, []byte{})
|
||
|
|
|
||
|
|
key := make([]byte, size)
|
||
|
|
|
||
|
|
// Read on the KDF will never fail
|
||
|
|
_, _ = reader.Read(key)
|
||
|
|
return key
|
||
|
|
}
|
||
|
|
|
||
|
|
func lengthPrefixed(data []byte) []byte {
|
||
|
|
out := make([]byte, len(data)+4)
|
||
|
|
binary.BigEndian.PutUint32(out, uint32(len(data)))
|
||
|
|
copy(out[4:], data)
|
||
|
|
return out
|
||
|
|
}
|