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e4bd9a13d8
Bug: webrtc:9860 Change-Id: I762d175bbf2c240feb476bbf6d91a1a748d9bcbb Reviewed-on: https://webrtc-review.googlesource.com/c/125125 Reviewed-by: Karl Wiberg <kwiberg@webrtc.org> Reviewed-by: Qingsi Wang <qingsi@webrtc.org> Commit-Queue: Benjamin Wright <benwright@webrtc.org> Cr-Commit-Position: refs/heads/master@{#26930}
108 lines
3.6 KiB
C++
108 lines
3.6 KiB
C++
/*
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* Copyright 2018 The WebRTC Project Authors. All rights reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "rtc_base/openssl_key_derivation_hkdf.h"
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#include <algorithm>
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#include <utility>
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#include <openssl/ossl_typ.h>
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#ifdef OPENSSL_IS_BORINGSSL
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#include <openssl/digest.h>
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#include <openssl/hkdf.h>
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#else
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#include <openssl/evp.h>
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#include <openssl/kdf.h>
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#endif
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#include <openssl/err.h>
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#include <openssl/sha.h>
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#include "rtc_base/buffer.h"
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#include "rtc_base/openssl.h"
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namespace rtc {
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#ifndef OPENSSL_IS_BORINGSSL
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namespace {
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// HKDF is static within OpenSSL and hence not accessible to the caller.
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// This internal implementation allows for compatibility with BoringSSL.
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static int HKDF(uint8_t* out_key,
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size_t out_len,
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const EVP_MD* digest,
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const uint8_t* secret,
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size_t secret_len,
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const uint8_t* salt,
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size_t salt_len,
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const uint8_t* info,
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size_t info_len) {
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EVP_PKEY_CTX* pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
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if (EVP_PKEY_derive_init(pctx) <= 0 ||
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EVP_PKEY_CTX_set_hkdf_md(pctx, digest) <= 0 ||
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EVP_PKEY_CTX_set1_hkdf_salt(pctx, salt, salt_len) <= 0 ||
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EVP_PKEY_CTX_set1_hkdf_key(pctx, secret, secret_len) <= 0 ||
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EVP_PKEY_CTX_add1_hkdf_info(pctx, info, info_len) <= 0 ||
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EVP_PKEY_derive(pctx, out_key, &out_len) <= 0) {
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EVP_PKEY_CTX_free(pctx);
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return 0;
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}
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EVP_PKEY_CTX_free(pctx);
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return 1;
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}
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} // namespace
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#endif
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OpenSSLKeyDerivationHKDF::OpenSSLKeyDerivationHKDF() = default;
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OpenSSLKeyDerivationHKDF::~OpenSSLKeyDerivationHKDF() = default;
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const size_t OpenSSLKeyDerivationHKDF::kMinKeyByteSize = 16;
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const size_t OpenSSLKeyDerivationHKDF::kMaxKeyByteSize =
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255 * SHA256_DIGEST_LENGTH;
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const size_t OpenSSLKeyDerivationHKDF::kMinSecretByteSize = 16;
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absl::optional<ZeroOnFreeBuffer<uint8_t>> OpenSSLKeyDerivationHKDF::DeriveKey(
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rtc::ArrayView<const uint8_t> secret,
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rtc::ArrayView<const uint8_t> salt,
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rtc::ArrayView<const uint8_t> label,
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size_t derived_key_byte_size) {
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// Prevent deriving less than 128 bits of key material or more than the max.
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if (derived_key_byte_size < kMinKeyByteSize ||
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derived_key_byte_size > kMaxKeyByteSize) {
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return absl::nullopt;
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}
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// The secret must reach the minimum number of bits to be secure.
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if (secret.data() == nullptr || secret.size() < kMinSecretByteSize) {
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return absl::nullopt;
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}
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// Empty labels are always invalid in derivation.
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if (label.data() == nullptr || label.size() == 0) {
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return absl::nullopt;
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}
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// If a random salt is not provided use all zeros.
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rtc::Buffer salt_buffer;
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if (salt.data() == nullptr || salt.size() == 0) {
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salt_buffer.SetSize(SHA256_DIGEST_LENGTH);
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std::fill(salt_buffer.begin(), salt_buffer.end(), 0);
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salt = salt_buffer;
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}
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// This buffer will erase itself on release.
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ZeroOnFreeBuffer<uint8_t> derived_key_buffer(derived_key_byte_size, 0);
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if (!HKDF(derived_key_buffer.data(), derived_key_buffer.size(), EVP_sha256(),
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secret.data(), secret.size(), salt.data(), salt.size(),
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label.data(), label.size())) {
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return absl::nullopt;
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}
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return absl::optional<ZeroOnFreeBuffer<uint8_t>>(
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std::move(derived_key_buffer));
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}
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} // namespace rtc
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