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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 "shim.h"
import "C"
import (
"errors"
"runtime"
"unsafe"
)
type HMAC struct {
ctx *C.HMAC_CTX
engine *Engine
md *C.EVP_MD
}
func NewHMAC(key []byte, digestAlgorithm EVP_MD) (*HMAC, error) {
return NewHMACWithEngine(key, digestAlgorithm, nil)
}
func NewHMACWithEngine(key []byte, digestAlgorithm EVP_MD, e *Engine) (*HMAC, error) {
var md *C.EVP_MD = getDigestFunction(digestAlgorithm)
h := &HMAC{engine: e, md: md}
h.ctx = C.X_HMAC_CTX_new()
if h.ctx == nil {
return nil, errors.New("unable to allocate HMAC_CTX")
}
var c_e *C.ENGINE
if e != nil {
c_e = e.e
}
if rc := C.X_HMAC_Init_ex(h.ctx,
unsafe.Pointer(&key[0]),
C.int(len(key)),
md,
c_e); rc != 1 {
C.X_HMAC_CTX_free(h.ctx)
return nil, errors.New("failed to initialize HMAC_CTX")
}
runtime.SetFinalizer(h, func(h *HMAC) { h.Close() })
return h, nil
}
func (h *HMAC) Close() {
C.X_HMAC_CTX_free(h.ctx)
}
func (h *HMAC) Write(data []byte) (n int, err error) {
if len(data) == 0 {
return 0, nil
}
if rc := C.X_HMAC_Update(h.ctx, (*C.uchar)(unsafe.Pointer(&data[0])),
C.size_t(len(data))); rc != 1 {
return 0, errors.New("failed to update HMAC")
}
runtime.KeepAlive(h)
return len(data), nil
}
func (h *HMAC) Reset() error {
if 1 != C.X_HMAC_Init_ex(h.ctx, nil, 0, nil, nil) {
return errors.New("failed to reset HMAC_CTX")
}
runtime.KeepAlive(h)
return nil
}
func (h *HMAC) Final() (result []byte, err error) {
mdLength := C.X_EVP_MD_size(h.md)
result = make([]byte, mdLength)
if rc := C.X_HMAC_Final(h.ctx, (*C.uchar)(unsafe.Pointer(&result[0])),
(*C.uint)(unsafe.Pointer(&mdLength))); rc != 1 {
return nil, errors.New("failed to finalized HMAC")
}
runtime.KeepAlive(result)
return result, h.Reset()
}
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