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// Copyright (C) 2017. See 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 openssl
// #include <openssl/evp.h>
import "C"
import (
"errors"
"fmt"
"runtime"
)
type AuthenticatedEncryptionCipherCtx interface {
EncryptionCipherCtx
// data passed in to ExtraData() is part of the final output; it is
// not encrypted itself, but is part of the authenticated data. when
// decrypting or authenticating, pass back with the decryption
// context's ExtraData()
ExtraData([]byte) error
// use after finalizing encryption to get the authenticating tag
GetTag() ([]byte, error)
}
type AuthenticatedDecryptionCipherCtx interface {
DecryptionCipherCtx
// pass in any extra data that was added during encryption with the
// encryption context's ExtraData()
ExtraData([]byte) error
// use before finalizing decryption to tell the library what the
// tag is expected to be
SetTag([]byte) error
}
type authEncryptionCipherCtx struct {
*encryptionCipherCtx
}
type authDecryptionCipherCtx struct {
*decryptionCipherCtx
}
func getGCMCipher(blocksize int) (*Cipher, error) {
var cipherptr *C.EVP_CIPHER
switch blocksize {
case 256:
cipherptr = C.EVP_aes_256_gcm()
case 192:
cipherptr = C.EVP_aes_192_gcm()
case 128:
cipherptr = C.EVP_aes_128_gcm()
default:
return nil, fmt.Errorf("unknown block size %d", blocksize)
}
return &Cipher{ptr: cipherptr}, nil
}
func NewGCMEncryptionCipherCtx(blocksize int, e *Engine, key, iv []byte) (
AuthenticatedEncryptionCipherCtx, error) {
cipher, err := getGCMCipher(blocksize)
if err != nil {
return nil, err
}
ctx, err := newEncryptionCipherCtx(cipher, e, key, nil)
if err != nil {
return nil, err
}
if len(iv) > 0 {
err := ctx.setCtrl(C.EVP_CTRL_GCM_SET_IVLEN, len(iv))
if err != nil {
return nil, fmt.Errorf("could not set IV len to %d: %s",
len(iv), err)
}
if 1 != C.EVP_EncryptInit_ex(ctx.ctx, nil, nil, nil,
(*C.uchar)(&iv[0])) {
return nil, errors.New("failed to apply IV")
}
runtime.KeepAlive(ctx)
runtime.KeepAlive(iv)
}
return &authEncryptionCipherCtx{encryptionCipherCtx: ctx}, nil
}
func NewGCMDecryptionCipherCtx(blocksize int, e *Engine, key, iv []byte) (
AuthenticatedDecryptionCipherCtx, error) {
cipher, err := getGCMCipher(blocksize)
if err != nil {
return nil, err
}
ctx, err := newDecryptionCipherCtx(cipher, e, key, nil)
if err != nil {
return nil, err
}
if len(iv) > 0 {
err := ctx.setCtrl(C.EVP_CTRL_GCM_SET_IVLEN, len(iv))
if err != nil {
return nil, fmt.Errorf("could not set IV len to %d: %s",
len(iv), err)
}
if 1 != C.EVP_DecryptInit_ex(ctx.ctx, nil, nil, nil,
(*C.uchar)(&iv[0])) {
return nil, errors.New("failed to apply IV")
}
runtime.KeepAlive(ctx)
runtime.KeepAlive(iv)
}
return &authDecryptionCipherCtx{decryptionCipherCtx: ctx}, nil
}
func (ctx *authEncryptionCipherCtx) ExtraData(aad []byte) error {
if aad == nil {
return nil
}
var outlen C.int
if 1 != C.EVP_EncryptUpdate(ctx.ctx, nil, &outlen, (*C.uchar)(&aad[0]),
C.int(len(aad))) {
return errors.New("failed to add additional authenticated data")
}
runtime.KeepAlive(ctx)
runtime.KeepAlive(aad)
return nil
}
func (ctx *authDecryptionCipherCtx) ExtraData(aad []byte) error {
if aad == nil {
return nil
}
var outlen C.int
if 1 != C.EVP_DecryptUpdate(ctx.ctx, nil, &outlen, (*C.uchar)(&aad[0]),
C.int(len(aad))) {
return errors.New("failed to add additional authenticated data")
}
runtime.KeepAlive(ctx)
runtime.KeepAlive(aad)
return nil
}
func (ctx *authEncryptionCipherCtx) GetTag() ([]byte, error) {
return ctx.getCtrlBytes(C.EVP_CTRL_GCM_GET_TAG, GCM_TAG_MAXLEN,
GCM_TAG_MAXLEN)
}
func (ctx *authDecryptionCipherCtx) SetTag(tag []byte) error {
return ctx.setCtrlBytes(C.EVP_CTRL_GCM_SET_TAG, len(tag), tag)
}
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