| /* |
| * 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 |
| * |
| * 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 "FwmarkServer.h" |
| |
| #include "Fwmark.h" |
| #include "FwmarkCommand.h" |
| #include "NetworkController.h" |
| #include "resolv_netid.h" |
| |
| #include <sys/socket.h> |
| #include <unistd.h> |
| |
| FwmarkServer::FwmarkServer(NetworkController* networkController) : |
| SocketListener("fwmarkd", true), mNetworkController(networkController) { |
| } |
| |
| bool FwmarkServer::onDataAvailable(SocketClient* client) { |
| int socketFd = -1; |
| int error = processClient(client, &socketFd); |
| if (socketFd >= 0) { |
| close(socketFd); |
| } |
| |
| // 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; |
| |
| iovec iov; |
| iov.iov_base = &command; |
| iov.iov_len = sizeof(command); |
| |
| msghdr message; |
| memset(&message, 0, sizeof(message)); |
| message.msg_iov = &iov; |
| message.msg_iovlen = 1; |
| |
| 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, 0)); |
| if (messageLength <= 0) { |
| return -errno; |
| } |
| |
| if (messageLength != sizeof(command)) { |
| return -EBADMSG; |
| } |
| |
| Permission permission = mNetworkController->getPermissionForUser(client->getUid()); |
| |
| if (command.cmdId == FwmarkCommand::QUERY_USER_ACCESS) { |
| if ((permission & PERMISSION_SYSTEM) != PERMISSION_SYSTEM) { |
| return -EPERM; |
| } |
| return mNetworkController->checkUserNetworkAccess(command.uid, command.netId); |
| } |
| |
| 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); |
| break; |
| } |
| |
| 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(); |
| } |
| } |
| break; |
| } |
| |
| 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()); |
| } |
| break; |
| } |
| |
| 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); |
| break; |
| } |
| |
| case FwmarkCommand::SELECT_FOR_USER: { |
| if ((permission & PERMISSION_SYSTEM) != PERMISSION_SYSTEM) { |
| return -EPERM; |
| } |
| fwmark.netId = mNetworkController->getNetworkForUser(command.uid); |
| fwmark.protectedFromVpn = true; |
| break; |
| } |
| |
| 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; |
| } |
