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104 lines
4.2 KiB
C++
104 lines
4.2 KiB
C++
// Copyright 2020 Google LLC
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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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// https://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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#ifndef THIRD_PARTY_NEARBY_INTERNAL_CRYPTO_OPENSSL_UTIL_H_
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#define THIRD_PARTY_NEARBY_INTERNAL_CRYPTO_OPENSSL_UTIL_H_
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#include <stddef.h>
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#include <string.h>
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#include "internal/crypto/crypto_export.h"
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namespace crypto {
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// Provides a buffer of at least MIN_SIZE bytes, for use when calling OpenSSL's
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// SHA256, HMAC, etc functions, adapting the buffer sizing rules to meet those
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// of our base wrapper APIs.
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// This allows the library to write directly to the caller's buffer if it is of
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// sufficient size, but if not it will write to temporary |min_sized_buffer_|
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// of required size and then its content is automatically copied out on
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// destruction, with truncation as appropriate.
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template <int MIN_SIZE>
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class ScopedOpenSSLSafeSizeBuffer {
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public:
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ScopedOpenSSLSafeSizeBuffer(unsigned char* output, size_t output_len)
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: output_(output), output_len_(output_len) {}
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ScopedOpenSSLSafeSizeBuffer(const ScopedOpenSSLSafeSizeBuffer&) = delete;
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ScopedOpenSSLSafeSizeBuffer& operator=(const ScopedOpenSSLSafeSizeBuffer&) =
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delete;
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~ScopedOpenSSLSafeSizeBuffer() {
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if (output_len_ < MIN_SIZE) {
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// Copy the temporary buffer out, truncating as needed.
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memcpy(output_, min_sized_buffer_, output_len_);
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}
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// else... any writing already happened directly into |output_|.
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}
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unsigned char* safe_buffer() {
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return output_len_ < MIN_SIZE ? min_sized_buffer_ : output_;
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}
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private:
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// Pointer to the caller's data area and its associated size, where data
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// written via safe_buffer() will [eventually] end up.
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unsigned char* output_;
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size_t output_len_;
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// Temporary buffer written into in the case where the caller's
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// buffer is not of sufficient size.
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unsigned char min_sized_buffer_[MIN_SIZE];
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};
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// Initialize OpenSSL if it isn't already initialized. This must be called
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// before any other OpenSSL functions though it is safe and cheap to call this
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// multiple times.
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// This function is thread-safe, and OpenSSL will only ever be initialized once.
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// OpenSSL will be properly shut down on program exit.
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CRYPTO_EXPORT void EnsureOpenSSLInit();
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// Drains the OpenSSL ERR_get_error stack. On a debug build the error codes
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// are send to VLOG(1), on a release build they are disregarded. In most
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// cases you should pass absl::SourceLocation::current() as the |location|.
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// TODO(b/239260254): Currently source_location.h is not available in OSS.
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// We can not use std::SourceLocation as it is C++20. Once we move to C++20 or
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// absl::SourceLocation is in OSS, add back "location".
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// See google3/third_party/castlite/agent/crypto/openssl_util.h for reference.
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CRYPTO_EXPORT void ClearOpenSSLERRStack();
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// Place an instance of this class on the call stack to automatically clear
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// the OpenSSL error stack on function exit.
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class OpenSSLErrStackTracer {
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public:
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// Pass absl::SourceLocation::current() as |location|, to help track the
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// source of OpenSSL error messages. Note any diagnostic emitted will be
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// tagged with the location of the constructor call as it's not possible to
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// trace a destructor's callsite.
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// TODO(b/239260254): Currently source_location.h is not available in OSS.
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// We can not use std::SourceLocation as it is C++20. Once we move to C++20 or
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// absl::SourceLocation is in OSS, add back "location".
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// See google3/third_party/castlite/agent/crypto/openssl_util.h for reference.
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OpenSSLErrStackTracer() { EnsureOpenSSLInit(); }
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OpenSSLErrStackTracer(const OpenSSLErrStackTracer&) = delete;
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OpenSSLErrStackTracer& operator=(const OpenSSLErrStackTracer&) = delete;
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~OpenSSLErrStackTracer() { ClearOpenSSLERRStack(); }
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};
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} // namespace crypto
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#endif // THIRD_PARTY_NEARBY_INTERNAL_CRYPTO_OPENSSL_UTIL_H_
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