netd/BpfHandler.cpp - platform/packages/modules/Connectivity - Gitiles

 /**
  * Copyright (c) 2022, 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.
  */

 #define LOG_TAG "BpfHandler"

 #include "BpfHandler.h"

 #include <linux/bpf.h>

 #include <android-base/unique_fd.h>
 #include <bpf/WaitForProgsLoaded.h>
 #include <log/log.h>
 #include <netdutils/UidConstants.h>
 #include <private/android_filesystem_config.h>

 #include "BpfSyscallWrappers.h"

 namespace android {
 namespace net {

 using base::unique_fd;
 using bpf::NONEXISTENT_COOKIE;
 using bpf::getSocketCookie;
 using bpf::retrieveProgram;
 using netdutils::Status;
 using netdutils::statusFromErrno;

 constexpr int PER_UID_STATS_ENTRIES_LIMIT = 500;
 // At most 90% of the stats map may be used by tagged traffic entries. This ensures
 // that 10% of the map is always available to count untagged traffic, one entry per UID.
 // Otherwise, apps would be able to avoid data usage accounting entirely by filling up the
 // map with tagged traffic entries.
 constexpr int TOTAL_UID_STATS_ENTRIES_LIMIT = STATS_MAP_SIZE * 0.9;

 static_assert(STATS_MAP_SIZE - TOTAL_UID_STATS_ENTRIES_LIMIT > 100,
               "The limit for stats map is to high, stats data may be lost due to overflow");

 static Status attachProgramToCgroup(const char* programPath, const unique_fd& cgroupFd,
                                     bpf_attach_type type) {
     unique_fd cgroupProg(retrieveProgram(programPath));
     if (cgroupProg == -1) {
         int ret = errno;
         ALOGE("Failed to get program from %s: %s", programPath, strerror(ret));
         return statusFromErrno(ret, "cgroup program get failed");
     }
     if (android::bpf::attachProgram(type, cgroupProg, cgroupFd)) {
         int ret = errno;
         ALOGE("Program from %s attach failed: %s", programPath, strerror(ret));
         return statusFromErrno(ret, "program attach failed");
     }
     return netdutils::status::ok;
 }

 static Status initPrograms(const char* cg2_path) {
     unique_fd cg_fd(open(cg2_path, O_DIRECTORY | O_RDONLY | O_CLOEXEC));
     if (cg_fd == -1) {
         int ret = errno;
         ALOGE("Failed to open the cgroup directory: %s", strerror(ret));
         return statusFromErrno(ret, "Open the cgroup directory failed");
     }
     RETURN_IF_NOT_OK(attachProgramToCgroup(BPF_EGRESS_PROG_PATH, cg_fd, BPF_CGROUP_INET_EGRESS));
     RETURN_IF_NOT_OK(attachProgramToCgroup(BPF_INGRESS_PROG_PATH, cg_fd, BPF_CGROUP_INET_INGRESS));

     // For the devices that support cgroup socket filter, the socket filter
     // should be loaded successfully by bpfloader. So we attach the filter to
     // cgroup if the program is pinned properly.
     // TODO: delete the if statement once all devices should support cgroup
     // socket filter (ie. the minimum kernel version required is 4.14).
     if (!access(CGROUP_SOCKET_PROG_PATH, F_OK)) {
         RETURN_IF_NOT_OK(
                 attachProgramToCgroup(CGROUP_SOCKET_PROG_PATH, cg_fd, BPF_CGROUP_INET_SOCK_CREATE));
     }
     return netdutils::status::ok;
 }

 BpfHandler::BpfHandler()
     : mPerUidStatsEntriesLimit(PER_UID_STATS_ENTRIES_LIMIT),
       mTotalUidStatsEntriesLimit(TOTAL_UID_STATS_ENTRIES_LIMIT) {}

 BpfHandler::BpfHandler(uint32_t perUidLimit, uint32_t totalLimit)
     : mPerUidStatsEntriesLimit(perUidLimit), mTotalUidStatsEntriesLimit(totalLimit) {}

 Status BpfHandler::init(const char* cg2_path) {
     // Make sure BPF programs are loaded before doing anything
     android::bpf::waitForProgsLoaded();
     ALOGI("BPF programs are loaded");

     RETURN_IF_NOT_OK(initPrograms(cg2_path));
     RETURN_IF_NOT_OK(initMaps());

     return netdutils::status::ok;
 }

 Status BpfHandler::initMaps() {
     std::lock_guard guard(mMutex);
     RETURN_IF_NOT_OK(mCookieTagMap.init(COOKIE_TAG_MAP_PATH));
     RETURN_IF_NOT_OK(mStatsMapA.init(STATS_MAP_A_PATH));
     RETURN_IF_NOT_OK(mStatsMapB.init(STATS_MAP_B_PATH));
     RETURN_IF_NOT_OK(mConfigurationMap.init(CONFIGURATION_MAP_PATH));
     RETURN_IF_NOT_OK(mUidPermissionMap.init(UID_PERMISSION_MAP_PATH));

     return netdutils::status::ok;
 }

 bool BpfHandler::hasUpdateDeviceStatsPermission(uid_t uid) {
     // This implementation is the same logic as method ActivityManager#checkComponentPermission.
     // It implies that the real uid can never be the same as PER_USER_RANGE.
     uint32_t appId = uid % PER_USER_RANGE;
     auto permission = mUidPermissionMap.readValue(appId);
     if (permission.ok() && (permission.value() & BPF_PERMISSION_UPDATE_DEVICE_STATS)) {
         return true;
     }
     return ((appId == AID_ROOT) || (appId == AID_SYSTEM) || (appId == AID_DNS));
 }

 int BpfHandler::tagSocket(int sockFd, uint32_t tag, uid_t chargeUid, uid_t realUid) {
     std::lock_guard guard(mMutex);
     if (chargeUid != realUid && !hasUpdateDeviceStatsPermission(realUid)) {
         return -EPERM;
     }

     // Note that tagging the socket to AID_CLAT is only implemented in JNI ClatCoordinator.
     // The process is not allowed to tag socket to AID_CLAT via tagSocket() which would cause
     // process data usage accounting to be bypassed. Tagging AID_CLAT is used for avoiding counting
     // CLAT traffic data usage twice. See packages/modules/Connectivity/service/jni/
     // com_android_server_connectivity_ClatCoordinator.cpp
     if (chargeUid == AID_CLAT) {
         return -EPERM;
     }

     // The socket destroy listener only monitors on the group {INET_TCP, INET_UDP, INET6_TCP,
     // INET6_UDP}. Tagging listener unsupported socket causes that the tag can't be removed from
     // tag map automatically. Eventually, the tag map may run out of space because of dead tag
     // entries. Note that although tagSocket() of net client has already denied the family which
     // is neither AF_INET nor AF_INET6, the family validation is still added here just in case.
     // See tagSocket in system/netd/client/NetdClient.cpp and
     // TrafficController::makeSkDestroyListener in
     // packages/modules/Connectivity/service/native/TrafficController.cpp
     // TODO: remove this once the socket destroy listener can detect more types of socket destroy.
     int socketFamily;
     socklen_t familyLen = sizeof(socketFamily);
     if (getsockopt(sockFd, SOL_SOCKET, SO_DOMAIN, &socketFamily, &familyLen)) {
         ALOGE("Failed to getsockopt SO_DOMAIN: %s, fd: %d", strerror(errno), sockFd);
         return -errno;
     }
     if (socketFamily != AF_INET && socketFamily != AF_INET6) {
         ALOGE("Unsupported family: %d", socketFamily);
         return -EAFNOSUPPORT;
     }

     int socketProto;
     socklen_t protoLen = sizeof(socketProto);
     if (getsockopt(sockFd, SOL_SOCKET, SO_PROTOCOL, &socketProto, &protoLen)) {
         ALOGE("Failed to getsockopt SO_PROTOCOL: %s, fd: %d", strerror(errno), sockFd);
         return -errno;
     }
     if (socketProto != IPPROTO_UDP && socketProto != IPPROTO_TCP) {
         ALOGE("Unsupported protocol: %d", socketProto);
         return -EPROTONOSUPPORT;
     }

     uint64_t sock_cookie = getSocketCookie(sockFd);
     if (sock_cookie == NONEXISTENT_COOKIE) return -errno;
     UidTagValue newKey = {.uid = (uint32_t)chargeUid, .tag = tag};

     uint32_t totalEntryCount = 0;
     uint32_t perUidEntryCount = 0;
     // Now we go through the stats map and count how many entries are associated
     // with chargeUid. If the uid entry hit the limit for each chargeUid, we block
     // the request to prevent the map from overflow. It is safe here to iterate
     // over the map since when mMutex is hold, system server cannot toggle
     // the live stats map and clean it. So nobody can delete entries from the map.
     const auto countUidStatsEntries = [chargeUid, &totalEntryCount, &perUidEntryCount](
                                               const StatsKey& key,
                                               const BpfMap<StatsKey, StatsValue>&) {
         if (key.uid == chargeUid) {
             perUidEntryCount++;
         }
         totalEntryCount++;
         return base::Result<void>();
     };
     auto configuration = mConfigurationMap.readValue(CURRENT_STATS_MAP_CONFIGURATION_KEY);
     if (!configuration.ok()) {
         ALOGE("Failed to get current configuration: %s, fd: %d",
               strerror(configuration.error().code()), mConfigurationMap.getMap().get());
         return -configuration.error().code();
     }
     if (configuration.value() != SELECT_MAP_A && configuration.value() != SELECT_MAP_B) {
         ALOGE("unknown configuration value: %d", configuration.value());
         return -EINVAL;
     }

     BpfMap<StatsKey, StatsValue>& currentMap =
             (configuration.value() == SELECT_MAP_A) ? mStatsMapA : mStatsMapB;
     // HACK: mStatsMapB becomes RW BpfMap here, but countUidStatsEntries doesn't modify so it works
     base::Result<void> res = currentMap.iterate(countUidStatsEntries);
     if (!res.ok()) {
         ALOGE("Failed to count the stats entry in map %d: %s", currentMap.getMap().get(),
               strerror(res.error().code()));
         return -res.error().code();
     }

     if (totalEntryCount > mTotalUidStatsEntriesLimit ||
         perUidEntryCount > mPerUidStatsEntriesLimit) {
         ALOGE("Too many stats entries in the map, total count: %u, chargeUid(%u) count: %u,"
               " blocking tag request to prevent map overflow",
               totalEntryCount, chargeUid, perUidEntryCount);
         return -EMFILE;
     }
     // Update the tag information of a socket to the cookieUidMap. Use BPF_ANY
     // flag so it will insert a new entry to the map if that value doesn't exist
     // yet. And update the tag if there is already a tag stored. Since the eBPF
     // program in kernel only read this map, and is protected by rcu read lock. It
     // should be fine to cocurrently update the map while eBPF program is running.
     res = mCookieTagMap.writeValue(sock_cookie, newKey, BPF_ANY);
     if (!res.ok()) {
         ALOGE("Failed to tag the socket: %s, fd: %d", strerror(res.error().code()),
               mCookieTagMap.getMap().get());
         return -res.error().code();
     }
     return 0;
 }

 int BpfHandler::untagSocket(int sockFd) {
     std::lock_guard guard(mMutex);
     uint64_t sock_cookie = getSocketCookie(sockFd);

     if (sock_cookie == NONEXISTENT_COOKIE) return -errno;
     base::Result<void> res = mCookieTagMap.deleteValue(sock_cookie);
     if (!res.ok()) {
         ALOGE("Failed to untag socket: %s\n", strerror(res.error().code()));
         return -res.error().code();
     }
     return 0;
 }

 }  // namespace net
 }  // namespace android
	/**
	* Copyright (c) 2022, 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.
	*/

	#define LOG_TAG "BpfHandler"

	#include "BpfHandler.h"

	#include <linux/bpf.h>

	#include <android-base/unique_fd.h>
	#include <bpf/WaitForProgsLoaded.h>
	#include <log/log.h>
	#include <netdutils/UidConstants.h>
	#include <private/android_filesystem_config.h>

	#include "BpfSyscallWrappers.h"

	namespace android {
	namespace net {

	using base::unique_fd;
	using bpf::NONEXISTENT_COOKIE;
	using bpf::getSocketCookie;
	using bpf::retrieveProgram;
	using netdutils::Status;
	using netdutils::statusFromErrno;

	constexpr int PER_UID_STATS_ENTRIES_LIMIT = 500;
	// At most 90% of the stats map may be used by tagged traffic entries. This ensures
	// that 10% of the map is always available to count untagged traffic, one entry per UID.
	// Otherwise, apps would be able to avoid data usage accounting entirely by filling up the
	// map with tagged traffic entries.
	constexpr int TOTAL_UID_STATS_ENTRIES_LIMIT = STATS_MAP_SIZE * 0.9;

	static_assert(STATS_MAP_SIZE - TOTAL_UID_STATS_ENTRIES_LIMIT > 100,
	"The limit for stats map is to high, stats data may be lost due to overflow");

	static Status attachProgramToCgroup(const char* programPath, const unique_fd& cgroupFd,
	bpf_attach_type type) {
	unique_fd cgroupProg(retrieveProgram(programPath));
	if (cgroupProg == -1) {
	int ret = errno;
	ALOGE("Failed to get program from %s: %s", programPath, strerror(ret));
	return statusFromErrno(ret, "cgroup program get failed");
	}
	if (android::bpf::attachProgram(type, cgroupProg, cgroupFd)) {
	int ret = errno;
	ALOGE("Program from %s attach failed: %s", programPath, strerror(ret));
	return statusFromErrno(ret, "program attach failed");
	}
	return netdutils::status::ok;
	}

	static Status initPrograms(const char* cg2_path) {
	unique_fd cg_fd(open(cg2_path, O_DIRECTORY \| O_RDONLY \| O_CLOEXEC));
	if (cg_fd == -1) {
	int ret = errno;
	ALOGE("Failed to open the cgroup directory: %s", strerror(ret));
	return statusFromErrno(ret, "Open the cgroup directory failed");
	}
	RETURN_IF_NOT_OK(attachProgramToCgroup(BPF_EGRESS_PROG_PATH, cg_fd, BPF_CGROUP_INET_EGRESS));
	RETURN_IF_NOT_OK(attachProgramToCgroup(BPF_INGRESS_PROG_PATH, cg_fd, BPF_CGROUP_INET_INGRESS));

	// For the devices that support cgroup socket filter, the socket filter
	// should be loaded successfully by bpfloader. So we attach the filter to
	// cgroup if the program is pinned properly.
	// TODO: delete the if statement once all devices should support cgroup
	// socket filter (ie. the minimum kernel version required is 4.14).
	if (!access(CGROUP_SOCKET_PROG_PATH, F_OK)) {
	RETURN_IF_NOT_OK(
	attachProgramToCgroup(CGROUP_SOCKET_PROG_PATH, cg_fd, BPF_CGROUP_INET_SOCK_CREATE));
	}
	return netdutils::status::ok;
	}

	BpfHandler::BpfHandler()
	: mPerUidStatsEntriesLimit(PER_UID_STATS_ENTRIES_LIMIT),
	mTotalUidStatsEntriesLimit(TOTAL_UID_STATS_ENTRIES_LIMIT) {}

	BpfHandler::BpfHandler(uint32_t perUidLimit, uint32_t totalLimit)
	: mPerUidStatsEntriesLimit(perUidLimit), mTotalUidStatsEntriesLimit(totalLimit) {}

	Status BpfHandler::init(const char* cg2_path) {
	// Make sure BPF programs are loaded before doing anything
	android::bpf::waitForProgsLoaded();
	ALOGI("BPF programs are loaded");

	RETURN_IF_NOT_OK(initPrograms(cg2_path));
	RETURN_IF_NOT_OK(initMaps());

	return netdutils::status::ok;
	}

	Status BpfHandler::initMaps() {
	std::lock_guard guard(mMutex);
	RETURN_IF_NOT_OK(mCookieTagMap.init(COOKIE_TAG_MAP_PATH));
	RETURN_IF_NOT_OK(mStatsMapA.init(STATS_MAP_A_PATH));
	RETURN_IF_NOT_OK(mStatsMapB.init(STATS_MAP_B_PATH));
	RETURN_IF_NOT_OK(mConfigurationMap.init(CONFIGURATION_MAP_PATH));
	RETURN_IF_NOT_OK(mUidPermissionMap.init(UID_PERMISSION_MAP_PATH));

	return netdutils::status::ok;
	}

	bool BpfHandler::hasUpdateDeviceStatsPermission(uid_t uid) {
	// This implementation is the same logic as method ActivityManager#checkComponentPermission.
	// It implies that the real uid can never be the same as PER_USER_RANGE.
	uint32_t appId = uid % PER_USER_RANGE;
	auto permission = mUidPermissionMap.readValue(appId);
	if (permission.ok() && (permission.value() & BPF_PERMISSION_UPDATE_DEVICE_STATS)) {
	return true;
	}
	return ((appId == AID_ROOT) \|\| (appId == AID_SYSTEM) \|\| (appId == AID_DNS));
	}

	int BpfHandler::tagSocket(int sockFd, uint32_t tag, uid_t chargeUid, uid_t realUid) {
	std::lock_guard guard(mMutex);
	if (chargeUid != realUid && !hasUpdateDeviceStatsPermission(realUid)) {
	return -EPERM;
	}

	// Note that tagging the socket to AID_CLAT is only implemented in JNI ClatCoordinator.
	// The process is not allowed to tag socket to AID_CLAT via tagSocket() which would cause
	// process data usage accounting to be bypassed. Tagging AID_CLAT is used for avoiding counting
	// CLAT traffic data usage twice. See packages/modules/Connectivity/service/jni/
	// com_android_server_connectivity_ClatCoordinator.cpp
	if (chargeUid == AID_CLAT) {
	return -EPERM;
	}

	// The socket destroy listener only monitors on the group {INET_TCP, INET_UDP, INET6_TCP,
	// INET6_UDP}. Tagging listener unsupported socket causes that the tag can't be removed from
	// tag map automatically. Eventually, the tag map may run out of space because of dead tag
	// entries. Note that although tagSocket() of net client has already denied the family which
	// is neither AF_INET nor AF_INET6, the family validation is still added here just in case.
	// See tagSocket in system/netd/client/NetdClient.cpp and
	// TrafficController::makeSkDestroyListener in
	// packages/modules/Connectivity/service/native/TrafficController.cpp
	// TODO: remove this once the socket destroy listener can detect more types of socket destroy.
	int socketFamily;
	socklen_t familyLen = sizeof(socketFamily);
	if (getsockopt(sockFd, SOL_SOCKET, SO_DOMAIN, &socketFamily, &familyLen)) {
	ALOGE("Failed to getsockopt SO_DOMAIN: %s, fd: %d", strerror(errno), sockFd);
	return -errno;
	}
	if (socketFamily != AF_INET && socketFamily != AF_INET6) {
	ALOGE("Unsupported family: %d", socketFamily);
	return -EAFNOSUPPORT;
	}

	int socketProto;
	socklen_t protoLen = sizeof(socketProto);
	if (getsockopt(sockFd, SOL_SOCKET, SO_PROTOCOL, &socketProto, &protoLen)) {
	ALOGE("Failed to getsockopt SO_PROTOCOL: %s, fd: %d", strerror(errno), sockFd);
	return -errno;
	}
	if (socketProto != IPPROTO_UDP && socketProto != IPPROTO_TCP) {
	ALOGE("Unsupported protocol: %d", socketProto);
	return -EPROTONOSUPPORT;
	}

	uint64_t sock_cookie = getSocketCookie(sockFd);
	if (sock_cookie == NONEXISTENT_COOKIE) return -errno;
	UidTagValue newKey = {.uid = (uint32_t)chargeUid, .tag = tag};

	uint32_t totalEntryCount = 0;
	uint32_t perUidEntryCount = 0;
	// Now we go through the stats map and count how many entries are associated
	// with chargeUid. If the uid entry hit the limit for each chargeUid, we block
	// the request to prevent the map from overflow. It is safe here to iterate
	// over the map since when mMutex is hold, system server cannot toggle
	// the live stats map and clean it. So nobody can delete entries from the map.
	const auto countUidStatsEntries = [chargeUid, &totalEntryCount, &perUidEntryCount](
	const StatsKey& key,
	const BpfMap<StatsKey, StatsValue>&) {
	if (key.uid == chargeUid) {
	perUidEntryCount++;
	}
	totalEntryCount++;
	return base::Result<void>();
	};
	auto configuration = mConfigurationMap.readValue(CURRENT_STATS_MAP_CONFIGURATION_KEY);
	if (!configuration.ok()) {
	ALOGE("Failed to get current configuration: %s, fd: %d",
	strerror(configuration.error().code()), mConfigurationMap.getMap().get());
	return -configuration.error().code();
	}
	if (configuration.value() != SELECT_MAP_A && configuration.value() != SELECT_MAP_B) {
	ALOGE("unknown configuration value: %d", configuration.value());
	return -EINVAL;
	}

	BpfMap<StatsKey, StatsValue>& currentMap =
	(configuration.value() == SELECT_MAP_A) ? mStatsMapA : mStatsMapB;
	// HACK: mStatsMapB becomes RW BpfMap here, but countUidStatsEntries doesn't modify so it works
	base::Result<void> res = currentMap.iterate(countUidStatsEntries);
	if (!res.ok()) {
	ALOGE("Failed to count the stats entry in map %d: %s", currentMap.getMap().get(),
	strerror(res.error().code()));
	return -res.error().code();
	}

	if (totalEntryCount > mTotalUidStatsEntriesLimit \|\|
	perUidEntryCount > mPerUidStatsEntriesLimit) {
	ALOGE("Too many stats entries in the map, total count: %u, chargeUid(%u) count: %u,"
	" blocking tag request to prevent map overflow",
	totalEntryCount, chargeUid, perUidEntryCount);
	return -EMFILE;
	}
	// Update the tag information of a socket to the cookieUidMap. Use BPF_ANY
	// flag so it will insert a new entry to the map if that value doesn't exist
	// yet. And update the tag if there is already a tag stored. Since the eBPF
	// program in kernel only read this map, and is protected by rcu read lock. It
	// should be fine to cocurrently update the map while eBPF program is running.
	res = mCookieTagMap.writeValue(sock_cookie, newKey, BPF_ANY);
	if (!res.ok()) {
	ALOGE("Failed to tag the socket: %s, fd: %d", strerror(res.error().code()),
	mCookieTagMap.getMap().get());
	return -res.error().code();
	}
	return 0;
	}

	int BpfHandler::untagSocket(int sockFd) {
	std::lock_guard guard(mMutex);
	uint64_t sock_cookie = getSocketCookie(sockFd);

	if (sock_cookie == NONEXISTENT_COOKIE) return -errno;
	base::Result<void> res = mCookieTagMap.deleteValue(sock_cookie);
	if (!res.ok()) {
	ALOGE("Failed to untag socket: %s\n", strerror(res.error().code()));
	return -res.error().code();
	}
	return 0;
	}

	} // namespace net
	} // namespace android