adb/adbconnection/adbconnection_client.cpp

/*
 * Copyright (C) 2020 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.
 */

#include "adbconnection/client.h"

#include <pwd.h>
#include <stddef.h>
#include <stdint.h>
#include <sys/socket.h>
#include <sys/un.h>

#include <memory>
#include <optional>

#include <android-base/cmsg.h>
#include <android-base/logging.h>
#include <android-base/unique_fd.h>

using android::base::unique_fd;

static constexpr char kJdwpControlName[] = "\0jdwp-control";

struct AdbConnectionClientContext {
  unique_fd control_socket_;
};

bool SocketPeerIsTrusted(int fd) {
  ucred cr;
  socklen_t cr_length = sizeof(cr);
  if (getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &cr, &cr_length) != 0) {
    PLOG(ERROR) << "couldn't get socket credentials";
    return false;
  }

  passwd* shell = getpwnam("shell");
  if (cr.uid != 0 && cr.uid != shell->pw_uid) {
    LOG(ERROR) << "untrusted uid " << cr.uid << " on other end of socket";
    return false;
  }

  return true;
}

AdbConnectionClientContext* adbconnection_client_new(
    const AdbConnectionClientInfo* const* info_elems, size_t info_count) {
  auto ctx = std::make_unique<AdbConnectionClientContext>();

  std::optional<uint64_t> pid;
  std::optional<bool> debuggable;

  for (size_t i = 0; i < info_count; ++i) {
    auto info = info_elems[i];
    switch (info->type) {
      case AdbConnectionClientInfoType::pid:
        if (pid) {
          LOG(ERROR) << "multiple pid entries in AdbConnectionClientInfo, ignoring";
          continue;
        }
        pid = info->data.pid;
        break;

      case AdbConnectionClientInfoType::debuggable:
        if (debuggable) {
          LOG(ERROR) << "multiple debuggable entries in AdbConnectionClientInfo, ignoring";
          continue;
        }
        debuggable = info->data.pid;
        break;
    }
  }

  if (!pid) {
    LOG(ERROR) << "AdbConnectionClientInfo missing required field pid";
    return nullptr;
  }

  if (!debuggable) {
    LOG(ERROR) << "AdbConnectionClientInfo missing required field debuggable";
    return nullptr;
  }

  ctx->control_socket_.reset(socket(AF_UNIX, SOCK_SEQPACKET | SOCK_CLOEXEC, 0));
  if (ctx->control_socket_ < 0) {
    PLOG(ERROR) << "failed to create Unix domain socket";
    return nullptr;
  }

  struct timeval timeout;
  timeout.tv_sec = 1;
  timeout.tv_usec = 0;
  setsockopt(ctx->control_socket_.get(), SOL_SOCKET, SO_SNDTIMEO, &timeout, sizeof(timeout));

  sockaddr_un addr = {};
  addr.sun_family = AF_UNIX;
  memcpy(addr.sun_path, kJdwpControlName, sizeof(kJdwpControlName));
  size_t addr_len = offsetof(sockaddr_un, sun_path) + sizeof(kJdwpControlName) - 1;

  int rc = connect(ctx->control_socket_.get(), reinterpret_cast<sockaddr*>(&addr), addr_len);
  if (rc != 0) {
    PLOG(ERROR) << "failed to connect to jdwp control socket";
    return nullptr;
  }

  bool trusted = SocketPeerIsTrusted(ctx->control_socket_.get());
  if (!trusted) {
    LOG(ERROR) << "adb socket is not trusted, aborting connection";
    return nullptr;
  }

  uint32_t pid_u32 = static_cast<uint32_t>(*pid);
  rc = TEMP_FAILURE_RETRY(write(ctx->control_socket_.get(), &pid_u32, sizeof(pid_u32)));
  if (rc != sizeof(pid_u32)) {
    PLOG(ERROR) << "failed to send JDWP process pid to adbd";
  }

  return ctx.release();
}

void adbconnection_client_destroy(AdbConnectionClientContext* ctx) {
  delete ctx;
}

int adbconnection_client_pollfd(AdbConnectionClientContext* ctx) {
  return ctx->control_socket_.get();
}

int adbconnection_client_receive_jdwp_fd(AdbConnectionClientContext* ctx) {
  char dummy;
  unique_fd jdwp_fd;
  ssize_t rc = android::base::ReceiveFileDescriptors(ctx->control_socket_, &dummy, 1, &jdwp_fd);
  if (rc != 1) {
    return rc;
  }
  return jdwp_fd.release();
}