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/*
* Copyright (C) 2018 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 "resolv"
#include "PrivateDnsConfiguration.h"
#include <algorithm>
#include <android-base/format.h>
#include <android-base/logging.h>
#include <android/binder_ibinder.h>
#include <netdutils/Slice.h>
#include <netdutils/ThreadUtil.h>
#include <sys/socket.h>
#include "DnsTlsTransport.h"
#include "ResolverEventReporter.h"
#include "doh.h"
#include "netd_resolv/resolv.h"
#include "resolv_cache.h"
#include "resolv_private.h"
#include "util.h"
using aidl::android::net::resolv::aidl::IDnsResolverUnsolicitedEventListener;
using aidl::android::net::resolv::aidl::PrivateDnsValidationEventParcel;
using android::netdutils::IPAddress;
using android::netdutils::IPSockAddr;
using android::netdutils::setThreadName;
using android::netdutils::Slice;
using std::chrono::milliseconds;
namespace android {
namespace net {
int PrivateDnsConfiguration::set(int32_t netId, uint32_t mark,
const std::vector<std::string>& servers, const std::string& name,
const std::string& caCert) {
LOG(DEBUG) << "PrivateDnsConfiguration::set(" << netId << ", 0x" << std::hex << mark << std::dec
<< ", " << servers.size() << ", " << name << ")";
// Parse the list of servers that has been passed in
PrivateDnsTracker tmp;
for (const auto& s : servers) {
IPAddress ip;
if (!IPAddress::forString(s, &ip)) {
LOG(WARNING) << "Failed to parse server address (" << s << ")";
return -EINVAL;
}
auto server = std::make_unique<DnsTlsServer>(ip);
server->name = name;
server->certificate = caCert;
server->mark = mark;
tmp[ServerIdentity(*server)] = std::move(server);
}
std::lock_guard guard(mPrivateDnsLock);
if (!name.empty()) {
mPrivateDnsModes[netId] = PrivateDnsMode::STRICT;
} else if (!tmp.empty()) {
mPrivateDnsModes[netId] = PrivateDnsMode::OPPORTUNISTIC;
} else {
mPrivateDnsModes[netId] = PrivateDnsMode::OFF;
mPrivateDnsTransports.erase(netId);
// TODO: signal validation threads to stop.
return 0;
}
// Create the tracker if it was not present
auto& tracker = mPrivateDnsTransports[netId];
// Add the servers if not contained in tracker.
for (auto& [identity, server] : tmp) {
if (tracker.find(identity) == tracker.end()) {
tracker[identity] = std::move(server);
}
}
for (auto& [identity, server] : tracker) {
const bool active = tmp.find(identity) != tmp.end();
server->setActive(active);
// For simplicity, deem the validation result of inactive servers as unreliable.
if (!server->active() && server->validationState() == Validation::success) {
updateServerState(identity, Validation::success_but_expired, netId);
}
if (needsValidation(*server)) {
updateServerState(identity, Validation::in_process, netId);
startValidation(identity, netId, false);
}
}
return 0;
}
PrivateDnsStatus PrivateDnsConfiguration::getStatus(unsigned netId) const {
PrivateDnsStatus status{
.mode = PrivateDnsMode::OFF,
.dotServersMap = {},
.dohServersMap = {},
};
std::lock_guard guard(mPrivateDnsLock);
const auto mode = mPrivateDnsModes.find(netId);
if (mode == mPrivateDnsModes.end()) return status;
status.mode = mode->second;
const auto netPair = mPrivateDnsTransports.find(netId);
if (netPair != mPrivateDnsTransports.end()) {
for (const auto& [_, server] : netPair->second) {
if (server->isDot() && server->active()) {
DnsTlsServer& dotServer = *static_cast<DnsTlsServer*>(server.get());
status.dotServersMap.emplace(dotServer, server->validationState());
}
}
}
auto it = mDohTracker.find(netId);
if (it != mDohTracker.end()) {
status.dohServersMap.emplace(
netdutils::IPSockAddr::toIPSockAddr(it->second.ipAddr, kDohPort),
it->second.status);
}
return status;
}
void PrivateDnsConfiguration::clear(unsigned netId) {
LOG(DEBUG) << "PrivateDnsConfiguration::clear(" << netId << ")";
std::lock_guard guard(mPrivateDnsLock);
mPrivateDnsModes.erase(netId);
mPrivateDnsTransports.erase(netId);
}
base::Result<void> PrivateDnsConfiguration::requestValidation(unsigned netId,
const ServerIdentity& identity,
uint32_t mark) {
std::lock_guard guard(mPrivateDnsLock);
// Running revalidation requires to mark the server as in_process, which means the server
// won't be used until the validation passes. It's necessary and safe to run revalidation
// when in private DNS opportunistic mode, because there's a fallback mechanics even if
// all of the private DNS servers are in in_process state.
if (auto it = mPrivateDnsModes.find(netId); it == mPrivateDnsModes.end()) {
return Errorf("NetId not found in mPrivateDnsModes");
} else if (it->second != PrivateDnsMode::OPPORTUNISTIC) {
return Errorf("Private DNS setting is not opportunistic mode");
}
auto result = getPrivateDnsLocked(identity, netId);
if (!result.ok()) {
return result.error();
}
const IPrivateDnsServer* server = result.value();
if (!server->active()) return Errorf("Server is not active");
if (server->validationState() != Validation::success) {
return Errorf("Server validation state mismatched");
}
// Don't run the validation if |mark| (from android_net_context.dns_mark) is different.
// This is to protect validation from running on unexpected marks.
// Validation should be associated with a mark gotten by system permission.
if (server->validationMark() != mark) return Errorf("Socket mark mismatched");
updateServerState(identity, Validation::in_process, netId);
startValidation(identity, netId, true);
return {};
}
void PrivateDnsConfiguration::startValidation(const ServerIdentity& identity, unsigned netId,
bool isRevalidation) {
// This ensures that the thread sends probe at least once in case
// the server is removed before the thread starts running.
// TODO: consider moving these code to the thread.
const auto result = getPrivateDnsLocked(identity, netId);
if (!result.ok()) return;
DnsTlsServer server = *static_cast<const DnsTlsServer*>(result.value());
std::thread validate_thread([this, identity, server, netId, isRevalidation] {
setThreadName(fmt::format("TlsVerify_{}", netId));
// cat /proc/sys/net/ipv4/tcp_syn_retries yields "6".
//
// Start with a 1 minute delay and backoff to once per hour.
//
// Assumptions:
// [1] Each TLS validation is ~10KB of certs+handshake+payload.
// [2] Network typically provision clients with <=4 nameservers.
// [3] Average month has 30 days.
//
// Each validation pass in a given hour is ~1.2MB of data. And 24
// such validation passes per day is about ~30MB per month, in the
// worst case. Otherwise, this will cost ~600 SYNs per month
// (6 SYNs per ip, 4 ips per validation pass, 24 passes per day).
auto backoff = mBackoffBuilder.build();
while (true) {
// ::validate() is a blocking call that performs network operations.
// It can take milliseconds to minutes, up to the SYN retry limit.
LOG(WARNING) << "Validating DnsTlsServer " << server.toIpString() << " with mark 0x"
<< std::hex << server.validationMark();
const bool success = DnsTlsTransport::validate(server, server.validationMark());
LOG(WARNING) << "validateDnsTlsServer returned " << success << " for "
<< server.toIpString();
const bool needs_reeval =
this->recordPrivateDnsValidation(identity, netId, success, isRevalidation);
if (!needs_reeval) {
break;
}
if (backoff.hasNextTimeout()) {
// TODO: make the thread able to receive signals to shutdown early.
std::this_thread::sleep_for(backoff.getNextTimeout());
} else {
break;
}
}
});
validate_thread.detach();
}
void PrivateDnsConfiguration::sendPrivateDnsValidationEvent(const ServerIdentity& identity,
unsigned netId, bool success) const {
LOG(DEBUG) << "Sending validation " << (success ? "success" : "failure") << " event on netId "
<< netId << " for " << identity.sockaddr.toString() << " with hostname {"
<< identity.provider << "}";
// Send a validation event to NetdEventListenerService.
const auto& listeners = ResolverEventReporter::getInstance().getListeners();
if (listeners.empty()) {
LOG(ERROR)
<< "Validation event not sent since no INetdEventListener receiver is available.";
}
for (const auto& it : listeners) {
it->onPrivateDnsValidationEvent(netId, identity.sockaddr.ip().toString(), identity.provider,
success);
}
// Send a validation event to unsolicited event listeners.
const auto& unsolEventListeners = ResolverEventReporter::getInstance().getUnsolEventListeners();
const PrivateDnsValidationEventParcel validationEvent = {
.netId = static_cast<int32_t>(netId),
.ipAddress = identity.sockaddr.ip().toString(),
.hostname = identity.provider,
.validation = success ? IDnsResolverUnsolicitedEventListener::VALIDATION_RESULT_SUCCESS
: IDnsResolverUnsolicitedEventListener::VALIDATION_RESULT_FAILURE,
.protocol = (identity.sockaddr.port() == kDotPort)
? IDnsResolverUnsolicitedEventListener::PROTOCOL_DOT
: IDnsResolverUnsolicitedEventListener::PROTOCOL_DOH,
};
for (const auto& it : unsolEventListeners) {
it->onPrivateDnsValidationEvent(validationEvent);
}
}
bool PrivateDnsConfiguration::recordPrivateDnsValidation(const ServerIdentity& identity,
unsigned netId, bool success,
bool isRevalidation) {
constexpr bool NEEDS_REEVALUATION = true;
constexpr bool DONT_REEVALUATE = false;
std::lock_guard guard(mPrivateDnsLock);
auto netPair = mPrivateDnsTransports.find(netId);
if (netPair == mPrivateDnsTransports.end()) {
LOG(WARNING) << "netId " << netId << " was erased during private DNS validation";
notifyValidationStateUpdate(identity.sockaddr, Validation::fail, netId);
return DONT_REEVALUATE;
}
const auto mode = mPrivateDnsModes.find(netId);
if (mode == mPrivateDnsModes.end()) {
LOG(WARNING) << "netId " << netId << " has no private DNS validation mode";
notifyValidationStateUpdate(identity.sockaddr, Validation::fail, netId);
return DONT_REEVALUATE;
}
bool reevaluationStatus = NEEDS_REEVALUATION;
if (success) {
reevaluationStatus = DONT_REEVALUATE;
} else if (mode->second == PrivateDnsMode::OFF) {
reevaluationStatus = DONT_REEVALUATE;
} else if (mode->second == PrivateDnsMode::OPPORTUNISTIC && !isRevalidation) {
reevaluationStatus = DONT_REEVALUATE;
}
auto& tracker = netPair->second;
auto serverPair = tracker.find(identity);
if (serverPair == tracker.end()) {
LOG(WARNING) << "Server " << identity.sockaddr.ip().toString()
<< " was removed during private DNS validation";
success = false;
reevaluationStatus = DONT_REEVALUATE;
} else if (!serverPair->second->active()) {
LOG(WARNING) << "Server " << identity.sockaddr.ip().toString()
<< " was removed from the configuration";
success = false;
reevaluationStatus = DONT_REEVALUATE;
}
// Send private dns validation result to listeners.
if (needReportEvent(netId, identity, success)) {
sendPrivateDnsValidationEvent(identity, netId, success);
}
if (success) {
updateServerState(identity, Validation::success, netId);
} else {
// Validation failure is expected if a user is on a captive portal.
// TODO: Trigger a second validation attempt after captive portal login
// succeeds.
const auto result = (reevaluationStatus == NEEDS_REEVALUATION) ? Validation::in_process
: Validation::fail;
updateServerState(identity, result, netId);
}
LOG(WARNING) << "Validation " << (success ? "success" : "failed");
return reevaluationStatus;
}
void PrivateDnsConfiguration::updateServerState(const ServerIdentity& identity, Validation state,
uint32_t netId) {
const auto result = getPrivateDnsLocked(identity, netId);
if (!result.ok()) {
notifyValidationStateUpdate(identity.sockaddr, Validation::fail, netId);
return;
}
auto* server = result.value();
server->setValidationState(state);
notifyValidationStateUpdate(identity.sockaddr, state, netId);
RecordEntry record(netId, identity, state);
mPrivateDnsLog.push(std::move(record));
}
bool PrivateDnsConfiguration::needsValidation(const IPrivateDnsServer& server) const {
// The server is not expected to be used on the network.
if (!server.active()) return false;
// The server is newly added.
if (server.validationState() == Validation::unknown_server) return true;
// The server has failed at least one validation attempt. Give it another try.
if (server.validationState() == Validation::fail) return true;
// The previous validation result might be unreliable.
if (server.validationState() == Validation::success_but_expired) return true;
return false;
}
base::Result<IPrivateDnsServer*> PrivateDnsConfiguration::getPrivateDns(
const ServerIdentity& identity, unsigned netId) {
std::lock_guard guard(mPrivateDnsLock);
return getPrivateDnsLocked(identity, netId);
}
base::Result<IPrivateDnsServer*> PrivateDnsConfiguration::getPrivateDnsLocked(
const ServerIdentity& identity, unsigned netId) {
auto netPair = mPrivateDnsTransports.find(netId);
if (netPair == mPrivateDnsTransports.end()) {
return Errorf("Failed to get private DNS: netId {} not found", netId);
}
auto iter = netPair->second.find(identity);
if (iter == netPair->second.end()) {
return Errorf("Failed to get private DNS: server {{{}/{}}} not found", identity.sockaddr,
identity.provider);
}
return iter->second.get();
}
void PrivateDnsConfiguration::setObserver(PrivateDnsValidationObserver* observer) {
std::lock_guard guard(mPrivateDnsLock);
mObserver = observer;
}
base::Result<netdutils::IPSockAddr> PrivateDnsConfiguration::getDohServer(unsigned netId) const {
std::lock_guard guard(mPrivateDnsLock);
auto it = mDohTracker.find(netId);
if (it != mDohTracker.end()) {
return netdutils::IPSockAddr::toIPSockAddr(it->second.ipAddr, kDohPort);
}
return Errorf("Failed to get DoH Server: netId {} not found", netId);
}
void PrivateDnsConfiguration::notifyValidationStateUpdate(const netdutils::IPSockAddr& sockaddr,
Validation validation,
uint32_t netId) const {
if (mObserver) {
mObserver->onValidationStateUpdate(sockaddr.ip().toString(), validation, netId);
}
}
void PrivateDnsConfiguration::dump(netdutils::DumpWriter& dw) const {
dw.println("PrivateDnsLog:");
netdutils::ScopedIndent indentStats(dw);
for (const auto& record : mPrivateDnsLog.copy()) {
dw.println(fmt::format(
"{} - netId={} PrivateDns={{{}/{}}} state={}", timestampToString(record.timestamp),
record.netId, record.serverIdentity.sockaddr.toString(),
record.serverIdentity.provider, validationStatusToString(record.state)));
}
dw.blankline();
}
void PrivateDnsConfiguration::initDoh() {
std::lock_guard guard(mPrivateDnsLock);
initDohLocked();
}
void PrivateDnsConfiguration::initDohLocked() {
if (mDohDispatcher != nullptr) return;
mDohDispatcher = doh_dispatcher_new(
[](uint32_t net_id, bool success, const char* ip_addr, const char* host) {
android::net::PrivateDnsConfiguration::getInstance().onDohStatusUpdate(
net_id, success, ip_addr, host);
},
[](int32_t sock) { resolv_tag_socket(sock, AID_DNS, NET_CONTEXT_INVALID_PID); });
}
int PrivateDnsConfiguration::setDoh(int32_t netId, uint32_t mark,
const std::vector<std::string>& servers,
const std::string& name, const std::string& caCert) {
LOG(DEBUG) << "PrivateDnsConfiguration::setDoh(" << netId << ", 0x" << std::hex << mark
<< std::dec << ", " << servers.size() << ", " << name << ")";
std::lock_guard guard(mPrivateDnsLock);
if (servers.empty()) {
clearDohLocked(netId);
return 0;
}
const auto getTimeoutFromFlag = [&](const std::string_view key, int defaultValue) -> uint64_t {
static constexpr int kMinTimeoutMs = 1000;
uint64_t timeout = Experiments::getInstance()->getFlag(key, defaultValue);
if (timeout < kMinTimeoutMs) {
timeout = kMinTimeoutMs;
}
return timeout;
};
// Sort the input servers to ensure that we could get the server vector at the same order.
std::vector<std::string> sortedServers = servers;
// Prefer ipv6.
std::sort(sortedServers.begin(), sortedServers.end(), [](std::string a, std::string b) {
IPAddress ipa = IPAddress::forString(a);
IPAddress ipb = IPAddress::forString(b);
return ipa > ipb;
});
initDohLocked();
// TODO: 1. Improve how to choose the server
// TODO: 2. Support multiple servers
for (const auto& entry : mAvailableDoHProviders) {
const auto& doh = entry.getDohIdentity(sortedServers, name);
if (!doh.ok()) continue;
// Since the DnsResolver is expected to be configured by the system server, add the
// restriction to prevent ResolverTestProvider from being used other than testing.
if (entry.requireRootPermission && AIBinder_getCallingUid() != AID_ROOT) continue;
auto it = mDohTracker.find(netId);
// Skip if the same server already exists and its status == success.
if (it != mDohTracker.end() && it->second == doh.value() &&
it->second.status == Validation::success) {
return 0;
}
const auto& [dohIt, _] = mDohTracker.insert_or_assign(netId, doh.value());
const auto& dohId = dohIt->second;
RecordEntry record(netId,
{netdutils::IPSockAddr::toIPSockAddr(dohId.ipAddr, kDohPort), name},
dohId.status);
mPrivateDnsLog.push(std::move(record));
LOG(INFO) << __func__ << ": Upgrading server to DoH: " << name;
resolv_stats_set_addrs(netId, PROTO_DOH, {dohId.ipAddr}, kDohPort);
const FeatureFlags flags = {
.probe_timeout_ms =
getTimeoutFromFlag("doh_probe_timeout_ms", kDohProbeDefaultTimeoutMs),
.idle_timeout_ms =
getTimeoutFromFlag("doh_idle_timeout_ms", kDohIdleDefaultTimeoutMs),
.use_session_resumption =
Experiments::getInstance()->getFlag("doh_session_resumption", 0) == 1,
};
LOG(DEBUG) << __func__ << ": probe_timeout_ms=" << flags.probe_timeout_ms
<< ", idle_timeout_ms=" << flags.idle_timeout_ms
<< ", use_session_resumption=" << flags.use_session_resumption;
return doh_net_new(mDohDispatcher, netId, dohId.httpsTemplate.c_str(), dohId.host.c_str(),
dohId.ipAddr.c_str(), mark, caCert.c_str(), &flags);
}
LOG(INFO) << __func__ << ": No suitable DoH server found";
clearDohLocked(netId);
return 0;
}
void PrivateDnsConfiguration::clearDohLocked(unsigned netId) {
LOG(DEBUG) << "PrivateDnsConfiguration::clearDohLocked (" << netId << ")";
if (mDohDispatcher != nullptr) doh_net_delete(mDohDispatcher, netId);
mDohTracker.erase(netId);
resolv_stats_set_addrs(netId, PROTO_DOH, {}, kDohPort);
}
void PrivateDnsConfiguration::clearDoh(unsigned netId) {
std::lock_guard guard(mPrivateDnsLock);
clearDohLocked(netId);
}
ssize_t PrivateDnsConfiguration::dohQuery(unsigned netId, const Slice query, const Slice answer,
uint64_t timeoutMs) {
{
std::lock_guard guard(mPrivateDnsLock);
// It's safe because mDohDispatcher won't be deleted after initializing.
if (mDohDispatcher == nullptr) return DOH_RESULT_CAN_NOT_SEND;
}
return doh_query(mDohDispatcher, netId, query.base(), query.size(), answer.base(),
answer.size(), timeoutMs);
}
void PrivateDnsConfiguration::onDohStatusUpdate(uint32_t netId, bool success, const char* ipAddr,
const char* host) {
LOG(INFO) << __func__ << ": " << netId << ", " << success << ", " << ipAddr << ", " << host;
std::lock_guard guard(mPrivateDnsLock);
// Update the server status.
auto it = mDohTracker.find(netId);
if (it == mDohTracker.end() || (it->second.ipAddr != ipAddr && it->second.host != host)) {
LOG(WARNING) << __func__ << ": Obsolete event";
return;
}
Validation status = success ? Validation::success : Validation::fail;
it->second.status = status;
// Send the events to registered listeners.
ServerIdentity identity = {netdutils::IPSockAddr::toIPSockAddr(ipAddr, kDohPort), host};
if (needReportEvent(netId, identity, success)) {
sendPrivateDnsValidationEvent(identity, netId, success);
}
// Add log.
RecordEntry record(netId, identity, status);
mPrivateDnsLog.push(std::move(record));
}
bool PrivateDnsConfiguration::needReportEvent(uint32_t netId, ServerIdentity identity,
bool success) const {
// If the result is success or DoH is not enable, no concern to report the events.
if (success || !isDoHEnabled()) return true;
// If the result is failure, check another transport's status to determine if we should report
// the event.
switch (identity.sockaddr.port()) {
// DoH
case kDohPort: {
auto netPair = mPrivateDnsTransports.find(netId);
if (netPair == mPrivateDnsTransports.end()) return true;
for (const auto& [id, server] : netPair->second) {
if ((identity.sockaddr.ip() == id.sockaddr.ip()) &&
(identity.sockaddr.port() != id.sockaddr.port()) &&
(server->validationState() == Validation::success)) {
LOG(DEBUG) << __func__
<< ": Skip reporting DoH validation failure event, server addr: "
<< identity.sockaddr.ip().toString();
return false;
}
}
break;
}
// DoT
case kDotPort: {
auto it = mDohTracker.find(netId);
if (it == mDohTracker.end()) return true;
if (it->second == identity && it->second.status == Validation::success) {
LOG(DEBUG) << __func__
<< ": Skip reporting DoT validation failure event, server addr: "
<< identity.sockaddr.ip().toString();
return false;
}
break;
}
}
return true;
}
} // namespace net
} // namespace android