67 lines
2.2 KiB
Go
67 lines
2.2 KiB
Go
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// Copyright (C) 2017. See AUTHORS.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package openssl
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// #include "shim.h"
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import "C"
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import (
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"errors"
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"unsafe"
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)
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// DeriveSharedSecret derives a shared secret using a private key and a peer's
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// public key.
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// The specific algorithm that is used depends on the types of the
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// keys, but it is most commonly a variant of Diffie-Hellman.
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func DeriveSharedSecret(private PrivateKey, public PublicKey) ([]byte, error) {
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// Create context for the shared secret derivation
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dhCtx := C.EVP_PKEY_CTX_new(private.evpPKey(), nil)
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if dhCtx == nil {
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return nil, errors.New("failed creating shared secret derivation context")
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}
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defer C.EVP_PKEY_CTX_free(dhCtx)
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// Initialize the context
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if int(C.EVP_PKEY_derive_init(dhCtx)) != 1 {
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return nil, errors.New("failed initializing shared secret derivation context")
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}
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// Provide the peer's public key
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if int(C.EVP_PKEY_derive_set_peer(dhCtx, public.evpPKey())) != 1 {
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return nil, errors.New("failed adding peer public key to context")
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}
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// Determine how large of a buffer we need for the shared secret
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var buffLen C.size_t
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if int(C.EVP_PKEY_derive(dhCtx, nil, &buffLen)) != 1 {
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return nil, errors.New("failed determining shared secret length")
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}
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// Allocate a buffer
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buffer := C.X_OPENSSL_malloc(buffLen)
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if buffer == nil {
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return nil, errors.New("failed allocating buffer for shared secret")
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}
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defer C.X_OPENSSL_free(buffer)
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// Derive the shared secret
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if int(C.EVP_PKEY_derive(dhCtx, (*C.uchar)(buffer), &buffLen)) != 1 {
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return nil, errors.New("failed deriving the shared secret")
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}
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secret := C.GoBytes(unsafe.Pointer(buffer), C.int(buffLen))
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return secret, nil
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}
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