blob: 32b856a673abc7d81d18c5ee29f912522eda9152 [file] [log] [blame]
* Copyright (C) 2014 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include "FwmarkServer.h"
#include "Fwmark.h"
#include "FwmarkCommand.h"
#include "NetdConstants.h"
#include "NetworkController.h"
#include "TrafficController.h"
#include "resolv_netid.h"
#include <netinet/in.h>
#include <selinux/selinux.h>
#include <sys/socket.h>
#include <unistd.h>
#include <utils/String16.h>
#include <binder/IServiceManager.h>
using android::String16;
using android::net::metrics::INetdEventListener;
namespace android {
namespace net {
constexpr const char *UPDATE_DEVICE_STATS = "android.permission.UPDATE_DEVICE_STATS";
constexpr const char *SYSTEM_SERVER_CONTEXT = "u:r:system_server:s0";
bool isSystemServer(SocketClient* client) {
if (client->getUid() != AID_SYSTEM) {
return false;
char *context;
if (getpeercon(client->getSocket(), &context)) {
return false;
// We can't use context_new and context_type_get as they're private to libselinux. So just do
// a string match instead.
bool ret = !strcmp(context, SYSTEM_SERVER_CONTEXT);
return ret;
bool hasUpdateDeviceStatsPermission(SocketClient* client) {
// If the caller is the system server, allow without any further checks.
// Otherwise, if the system server's binder thread pool is full, and all the threads are
// blocked on a thread that's waiting for us to complete, we deadlock. http://b/69389492
return isSystemServer(client) ||
checkPermission(String16(UPDATE_DEVICE_STATS), client->getPid(), client->getUid());
FwmarkServer::FwmarkServer(NetworkController* networkController, EventReporter* eventReporter,
TrafficController* trafficCtrl)
: SocketListener(SOCKET_NAME, true),
mTrafficCtrl(trafficCtrl) {}
bool FwmarkServer::onDataAvailable(SocketClient* client) {
int socketFd = -1;
int error = processClient(client, &socketFd);
if (socketFd >= 0) {
// Always send a response even if there were connection errors or read errors, so that we don't
// inadvertently cause the client to hang (which always waits for a response).
client->sendData(&error, sizeof(error));
// Always close the client connection (by returning false). This prevents a DoS attack where
// the client issues multiple commands on the same connection, never reading the responses,
// causing its receive buffer to fill up, and thus causing our client->sendData() to block.
return false;
int FwmarkServer::processClient(SocketClient* client, int* socketFd) {
FwmarkCommand command;
FwmarkConnectInfo connectInfo;
iovec iov[2] = {
{ &command, sizeof(command) },
{ &connectInfo, sizeof(connectInfo) },
msghdr message;
memset(&message, 0, sizeof(message));
message.msg_iov = iov;
message.msg_iovlen = ARRAY_SIZE(iov);
union {
cmsghdr cmh;
char cmsg[CMSG_SPACE(sizeof(*socketFd))];
} cmsgu;
memset(cmsgu.cmsg, 0, sizeof(cmsgu.cmsg));
message.msg_control = cmsgu.cmsg;
message.msg_controllen = sizeof(cmsgu.cmsg);
int messageLength = TEMP_FAILURE_RETRY(recvmsg(client->getSocket(), &message, MSG_CMSG_CLOEXEC));
if (messageLength <= 0) {
return -errno;
if (!((command.cmdId != FwmarkCommand::ON_CONNECT_COMPLETE && messageLength == sizeof(command))
|| (command.cmdId == FwmarkCommand::ON_CONNECT_COMPLETE
&& messageLength == sizeof(command) + sizeof(connectInfo)))) {
return -EBADMSG;
Permission permission = mNetworkController->getPermissionForUser(client->getUid());
if (command.cmdId == FwmarkCommand::QUERY_USER_ACCESS) {
return -EPERM;
return mNetworkController->checkUserNetworkAccess(command.uid, command.netId);
if (command.cmdId == FwmarkCommand::SET_COUNTERSET) {
if (!hasUpdateDeviceStatsPermission(client)) {
return -EPERM;
return mTrafficCtrl->setCounterSet(command.trafficCtrlInfo, command.uid);
if (command.cmdId == FwmarkCommand::DELETE_TAGDATA) {
if (!hasUpdateDeviceStatsPermission(client)) {
return -EPERM;
return mTrafficCtrl->deleteTagData(command.trafficCtrlInfo, command.uid);
cmsghdr* const cmsgh = CMSG_FIRSTHDR(&message);
if (cmsgh && cmsgh->cmsg_level == SOL_SOCKET && cmsgh->cmsg_type == SCM_RIGHTS &&
cmsgh->cmsg_len == CMSG_LEN(sizeof(*socketFd))) {
memcpy(socketFd, CMSG_DATA(cmsgh), sizeof(*socketFd));
if (*socketFd < 0) {
return -EBADF;
Fwmark fwmark;
socklen_t fwmarkLen = sizeof(fwmark.intValue);
if (getsockopt(*socketFd, SOL_SOCKET, SO_MARK, &fwmark.intValue, &fwmarkLen) == -1) {
return -errno;
switch (command.cmdId) {
case FwmarkCommand::ON_ACCEPT: {
// Called after a socket accept(). The kernel would've marked the NetId and necessary
// permissions bits, so we just add the rest of the user's permissions here.
permission = static_cast<Permission>(permission | fwmark.permission);
case FwmarkCommand::ON_CONNECT: {
// Called before a socket connect() happens. Set an appropriate NetId into the fwmark so
// that the socket routes consistently over that network. Do this even if the socket
// already has a NetId, so that calling connect() multiple times still works.
// But if the explicit bit was set, the existing NetId was explicitly preferred (and not
// a case of connect() being called multiple times). Don't reset the NetId in that case.
// An "appropriate" NetId is the NetId of a bypassable VPN that applies to the user, or
// failing that, the default network. We'll never set the NetId of a secure VPN here.
// See the comments in the implementation of getNetworkForConnect() for more details.
// If the protect bit is set, this could be either a system proxy (e.g.: the dns proxy
// or the download manager) acting on behalf of another user, or a VPN provider. If it's
// a proxy, we shouldn't reset the NetId. If it's a VPN provider, we should set the
// default network's NetId.
// There's no easy way to tell the difference between a proxy and a VPN app. We can't
// use PERMISSION_SYSTEM to identify the proxy because a VPN app may also have those
// permissions. So we use the following heuristic:
// If it's a proxy, but the existing NetId is not a VPN, that means the user (that the
// proxy is acting on behalf of) is not subject to a VPN, so the proxy must have picked
// the default network's NetId. So, it's okay to replace that with the current default
// network's NetId (which in all likelihood is the same).
// Conversely, if it's a VPN provider, the existing NetId cannot be a VPN. The only time
// we set a VPN's NetId into a socket without setting the explicit bit is here, in
// ON_CONNECT, but we won't do that if the socket has the protect bit set. If the VPN
// provider connect()ed (and got the VPN NetId set) and then called protect(), we
// would've unset the NetId in PROTECT_FROM_VPN below.
// So, overall (when the explicit bit is not set but the protect bit is set), if the
// existing NetId is a VPN, don't reset it. Else, set the default network's NetId.
if (!fwmark.explicitlySelected) {
if (!fwmark.protectedFromVpn) {
fwmark.netId = mNetworkController->getNetworkForConnect(client->getUid());
} else if (!mNetworkController->isVirtualNetwork(fwmark.netId)) {
fwmark.netId = mNetworkController->getDefaultNetwork();
case FwmarkCommand::ON_CONNECT_COMPLETE: {
// Called after a socket connect() completes.
// This reports connect event including netId, destination IP address, destination port,
// uid, connect latency, and connect errno if any.
// Skip reporting if connect() happened on a UDP socket.
int socketProto;
socklen_t intSize = sizeof(socketProto);
const int ret = getsockopt(*socketFd, SOL_SOCKET, SO_PROTOCOL, &socketProto, &intSize);
if ((ret != 0) || (socketProto == IPPROTO_UDP)) {
android::sp<android::net::metrics::INetdEventListener> netdEventListener =
if (netdEventListener != nullptr) {
char addrstr[INET6_ADDRSTRLEN];
char portstr[sizeof("65536")];
const int ret = getnameinfo((sockaddr*) &connectInfo.addr, sizeof(connectInfo.addr),
addrstr, sizeof(addrstr), portstr, sizeof(portstr),
netdEventListener->onConnectEvent(fwmark.netId, connectInfo.error,
(ret == 0) ? String16(addrstr) : String16(""),
(ret == 0) ? strtoul(portstr, NULL, 10) : 0, client->getUid());
case FwmarkCommand::SELECT_NETWORK: {
fwmark.netId = command.netId;
if (command.netId == NETID_UNSET) {
fwmark.explicitlySelected = false;
fwmark.protectedFromVpn = false;
permission = PERMISSION_NONE;
} else {
if (int ret = mNetworkController->checkUserNetworkAccess(client->getUid(),
command.netId)) {
return ret;
fwmark.explicitlySelected = true;
fwmark.protectedFromVpn = mNetworkController->canProtect(client->getUid());
case FwmarkCommand::PROTECT_FROM_VPN: {
if (!mNetworkController->canProtect(client->getUid())) {
return -EPERM;
// If a bypassable VPN's provider app calls connect() and then protect(), it will end up
// with a socket that looks like that of a system proxy but is not (see comments for
// ON_CONNECT above). So, reset the NetId.
// In any case, it's appropriate that if the socket has an implicit VPN NetId mark, the
// PROTECT_FROM_VPN command should unset it.
if (!fwmark.explicitlySelected && mNetworkController->isVirtualNetwork(fwmark.netId)) {
fwmark.netId = mNetworkController->getDefaultNetwork();
fwmark.protectedFromVpn = true;
permission = static_cast<Permission>(permission | fwmark.permission);
case FwmarkCommand::SELECT_FOR_USER: {
return -EPERM;
fwmark.netId = mNetworkController->getNetworkForUser(command.uid);
fwmark.protectedFromVpn = true;
case FwmarkCommand::TAG_SOCKET: {
// If the UID is -1, tag as the caller's UID:
// - TrafficStats and NetworkManagementSocketTagger use -1 to indicate "use the
// caller's UID".
// - xt_qtaguid will see -1 on the command line, fail to parse it as a uint32_t, and
// fall back to current_fsuid().
if (static_cast<int>(command.uid) == -1) {
command.uid = client->getUid();
if (command.uid != client->getUid() && !hasUpdateDeviceStatsPermission(client)) {
return -EPERM;
return mTrafficCtrl->tagSocket(*socketFd, command.trafficCtrlInfo, command.uid);
case FwmarkCommand::UNTAG_SOCKET: {
// Any process can untag a socket it has an fd for.
return mTrafficCtrl->untagSocket(*socketFd);
default: {
// unknown command
return -EPROTO;
fwmark.permission = permission;
if (setsockopt(*socketFd, SOL_SOCKET, SO_MARK, &fwmark.intValue,
sizeof(fwmark.intValue)) == -1) {
return -errno;
return 0;
} // namespace net
} // namespace android