server/dns/DnsTlsTransport.h

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * 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.
 */

#ifndef _DNS_DNSTLSTRANSPORT_H
#define _DNS_DNSTLSTRANSPORT_H

#include <netinet/in.h>
#include <set>
#include <sys/socket.h>
#include <sys/types.h>
#include <vector>

#include "android-base/unique_fd.h"

// Forward declaration.
typedef struct ssl_st SSL;

namespace android {
namespace net {

class DnsTlsTransport {
public:
    DnsTlsTransport(unsigned mark, int protocol, const sockaddr_storage &ss,
            const std::set<std::vector<uint8_t>>& fingerprints)
            : mMark(mark), mProtocol(protocol), mAddr(ss), mFingerprints(fingerprints)
            {}
    ~DnsTlsTransport() {}

    enum class Response : uint8_t { success, network_error, limit_error, internal_error };

    // Given a |query| of length |qlen|, sends it to the server and writes the
    // response into |ans|, which can accept up to |anssiz| bytes.  Indicates
    // the number of bytes written in |resplen|.  If |resplen| is zero, an
    // error has occurred.
    Response doQuery(const uint8_t *query, size_t qlen, uint8_t *ans, size_t anssiz, int *resplen);

private:
    // On success, returns a non-blocking socket connected to mAddr (the
    // connection will likely be in progress if mProtocol is IPPROTO_TCP).
    // On error, returns -1 with errno set appropriately.
    android::base::unique_fd makeConnectedSocket() const;

    SSL* sslConnect(int fd);

    // Writes a buffer to the socket.
    bool sslWrite(int fd, SSL *ssl, const uint8_t *buffer, int len);

    // Reads exactly the specified number of bytes from the socket.  Blocking.
    // Returns false if the socket closes before enough bytes can be read.
    bool sslRead(int fd, SSL *ssl, uint8_t *buffer, int len);

    const unsigned mMark;  // Socket mark
    const int mProtocol;
    const sockaddr_storage mAddr;
    const std::set<std::vector<uint8_t>> mFingerprints;
};

// Check that a given TLS server (ss) is fully working on the specified netid, and has a
// provided SHA-256 fingerprint (if nonempty).  This function is used in ResolverController
// to ensure that we don't enable DNS over TLS on networks where it doesn't actually work.
bool validateDnsTlsServer(unsigned netid, const sockaddr_storage& ss,
        const std::set<std::vector<uint8_t>>& fingerprints);

}  // namespace net
}  // namespace android

#endif  // _DNS_DNSTLSTRANSPORT_H