/*
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* Copyright (C) 2018 The Android Open Source Project
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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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*/
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#ifndef _DNS_DNSTLSSOCKET_H
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#define _DNS_DNSTLSSOCKET_H
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#include <openssl/ssl.h>
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#include <future>
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#include <mutex>
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#include <android-base/thread_annotations.h>
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#include <android-base/unique_fd.h>
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#include <netdutils/Slice.h>
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#include <netdutils/Status.h>
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#include "DnsTlsServer.h"
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#include "IDnsTlsSocket.h"
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#include "LockedQueue.h"
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namespace android {
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namespace net {
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class IDnsTlsSocketObserver;
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class DnsTlsSessionCache;
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// A class for managing a TLS socket that sends and receives messages in
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// [length][value] format, with a 2-byte length (i.e. DNS-over-TCP format).
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// This class is not aware of query-response pairing or anything else about DNS.
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// For the observer:
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// This class is not re-entrant: the observer is not permitted to wait for a call to query()
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// or the destructor in a callback. Doing so will result in deadlocks.
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// This class may call the observer at any time after initialize(), until the destructor
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// returns (but not after).
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class DnsTlsSocket : public IDnsTlsSocket {
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public:
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DnsTlsSocket(const DnsTlsServer& server, unsigned mark,
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IDnsTlsSocketObserver* _Nonnull observer, DnsTlsSessionCache* _Nonnull cache)
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: mMark(mark), mServer(server), mObserver(observer), mCache(cache) {}
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~DnsTlsSocket();
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// Creates the SSL context for this session and connect. Returns false on failure.
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// This method should be called after construction and before use of a DnsTlsSocket.
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// Only call this method once per DnsTlsSocket.
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bool initialize() EXCLUDES(mLock);
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// Send a query on the provided SSL socket. |query| contains
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// the body of a query, not including the ID header. This function will typically return before
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// the query is actually sent. If this function fails, DnsTlsSocketObserver will be
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// notified that the socket is closed.
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// Note that success here indicates successful sending, not receipt of a response.
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// Thread-safe.
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bool query(uint16_t id, const netdutils::Slice query) override EXCLUDES(mLock);
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private:
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// Lock to be held by the SSL event loop thread. This is not normally in contention.
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std::mutex mLock;
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// Forwards queries and receives responses. Blocks until the idle timeout.
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void loop() EXCLUDES(mLock);
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std::unique_ptr<std::thread> mLoopThread GUARDED_BY(mLock);
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// On success, sets mSslFd to a socket connected to mAddr (the
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// connection will likely be in progress if mProtocol is IPPROTO_TCP).
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// On error, returns the errno.
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netdutils::Status tcpConnect() REQUIRES(mLock);
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// Connect an SSL session on the provided socket. If connection fails, closing the
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// socket remains the caller's responsibility.
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bssl::UniquePtr<SSL> sslConnect(int fd) REQUIRES(mLock);
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// Disconnect the SSL session and close the socket.
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void sslDisconnect() REQUIRES(mLock);
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// Writes a buffer to the socket.
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bool sslWrite(const netdutils::Slice buffer) REQUIRES(mLock);
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// Reads exactly the specified number of bytes from the socket, or fails.
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// Returns SSL_ERROR_NONE on success.
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// If |wait| is true, then this function always blocks. Otherwise, it
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// will return SSL_ERROR_WANT_READ if there is no data from the server to read.
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int sslRead(const netdutils::Slice buffer, bool wait) REQUIRES(mLock);
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bool sendQuery(const std::vector<uint8_t>& buf) REQUIRES(mLock);
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bool readResponse() REQUIRES(mLock);
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// Similar to query(), this function uses incrementEventFd to send a message to the
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// loop thread. However, instead of incrementing the counter by one (indicating a
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// new query), it wraps the counter to negative, which we use to indicate a shutdown
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// request.
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void requestLoopShutdown() EXCLUDES(mLock);
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// This function sends a message to the loop thread by incrementing mEventFd.
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bool incrementEventFd(int64_t count) EXCLUDES(mLock);
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// Queue of pending queries. query() pushes items onto the queue and notifies
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// the loop thread by incrementing mEventFd. loop() reads items off the queue.
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LockedQueue<std::vector<uint8_t>> mQueue;
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// eventfd socket used for notifying the SSL thread when queries are ready to send.
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// This socket acts similarly to an atomic counter, incremented by query() and cleared
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// by loop(). We have to use a socket because the SSL thread needs to wait in poll()
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// for input from either a remote server or a query thread. Since eventfd does not have
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// EOF, we indicate a close request by setting the counter to a negative number.
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// This file descriptor is opened by initialize(), and closed implicitly after
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// destruction.
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base::unique_fd mEventFd;
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// SSL Socket fields.
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bssl::UniquePtr<SSL_CTX> mSslCtx GUARDED_BY(mLock);
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base::unique_fd mSslFd GUARDED_BY(mLock);
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bssl::UniquePtr<SSL> mSsl GUARDED_BY(mLock);
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static constexpr std::chrono::seconds kIdleTimeout = std::chrono::seconds(20);
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const unsigned mMark; // Socket mark
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const DnsTlsServer mServer;
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IDnsTlsSocketObserver* _Nonnull const mObserver;
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DnsTlsSessionCache* _Nonnull const mCache;
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};
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} // end of namespace net
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} // end of namespace android
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#endif // _DNS_DNSTLSSOCKET_H
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