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jwe_direct_encryptor_aead.go
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jwe_direct_encryptor_aead.go
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// Copyright 2024 Thales Group
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
package gose
import (
"github.com/ThalesGroup/gose/jose"
)
var (
gcmAlgToEncMap = map[jose.Alg]jose.Enc{
jose.AlgA128GCM: jose.EncA128GCM,
jose.AlgA192GCM: jose.EncA192GCM,
jose.AlgA256GCM: jose.EncA256GCM,
}
)
// JweDirectEncryptorAead implementation of JweDirectEncryptionEncryptor interface.
type JweDirectEncryptorAead struct {
key AeadEncryptionKey
externalIV bool
}
// Encrypt encrypt and authenticate the given plaintext and AAD returning a compact JWE.
func (encryptor *JweDirectEncryptorAead) Encrypt(plaintext, aad []byte) (string, error) {
var nonce []byte
var err error
if !encryptor.externalIV {
nonce, err = encryptor.key.GenerateNonce()
if err != nil {
return "", err
}
}
var blob *jose.Blob
var customHeaderFields jose.JweCustomHeaderFields
if len(aad) > 0 {
blob = &jose.Blob{B: aad}
customHeaderFields = jose.JweCustomHeaderFields{
OtherAad: blob,
}
}
jwe := &jose.Jwe{
Header: jose.JweHeader{
JwsHeader: jose.JwsHeader{
Alg: jose.AlgDir,
Kid: encryptor.key.Kid(),
},
Enc: gcmAlgToEncMap[encryptor.key.Algorithm()],
JweCustomHeaderFields: customHeaderFields,
},
EncryptedKey: []byte{},
Iv: nonce,
Plaintext: plaintext,
}
if err = jwe.MarshalHeader(); err != nil {
return "", err
}
if jwe.Ciphertext, jwe.Tag, err = encryptor.key.Seal(jose.KeyOpsEncrypt, jwe.Iv, jwe.Plaintext, jwe.MarshalledHeader); err != nil {
return "", err
}
if encryptor.externalIV {
/*
If using an externally-generated IV this will have been returned in the tag field
So we trim the tag field and update the IV field
*/
var throwawayNonceToGetLength []byte
if throwawayNonceToGetLength, err = encryptor.key.GenerateNonce(); nil != err {
return "", err
}
jwe.Iv = jwe.Tag[len(jwe.Tag)-len(throwawayNonceToGetLength):]
jwe.Tag = jwe.Tag[:len(jwe.Tag)-len(throwawayNonceToGetLength)]
}
return jwe.Marshal(), nil
}
// NewJweDirectEncryptorAead construct an instance of a JweDirectEncryptorAead.
func NewJweDirectEncryptorAead(key AeadEncryptionKey, externalIV bool) *JweDirectEncryptorAead {
return &JweDirectEncryptorAead{
key: key,
externalIV: externalIV,
}
}