/**
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* Copyright (c) 2019, The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#define LOG_TAG "DnsResolverService"
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#include "DnsResolverService.h"
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#include <set>
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#include <vector>
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#include <android-base/stringprintf.h>
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#include <android-base/strings.h>
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#include <android/binder_manager.h>
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#include <android/binder_process.h>
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#include <json/value.h>
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#include <json/writer.h>
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#include <log/log.h>
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#include <netdutils/DumpWriter.h>
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#include <openssl/base64.h>
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#include <private/android_filesystem_config.h> // AID_SYSTEM
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#include "BinderUtil.h"
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#include "DnsResolver.h"
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#include "NetdConstants.h" // SHA256_SIZE
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#include "NetdPermissions.h" // PERM_*
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#include "ResolverEventReporter.h"
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#include "resolv_cache.h"
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using aidl::android::net::ResolverParamsParcel;
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using android::base::Join;
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using android::base::StringPrintf;
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using android::netdutils::DumpWriter;
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namespace android {
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namespace net {
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namespace {
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#define ENFORCE_ANY_PERMISSION(...) \
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do { \
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::ndk::ScopedAStatus status = checkAnyPermission({__VA_ARGS__}); \
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if (!status.isOk()) { \
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return status; \
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} \
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} while (0)
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#define ENFORCE_INTERNAL_PERMISSIONS() \
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ENFORCE_ANY_PERMISSION(PERM_CONNECTIVITY_INTERNAL, PERM_MAINLINE_NETWORK_STACK)
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#define ENFORCE_NETWORK_STACK_PERMISSIONS() \
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ENFORCE_ANY_PERMISSION(PERM_NETWORK_STACK, PERM_MAINLINE_NETWORK_STACK)
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inline ::ndk::ScopedAStatus statusFromErrcode(int ret) {
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if (ret) {
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return ::ndk::ScopedAStatus(
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AStatus_fromServiceSpecificErrorWithMessage(-ret, strerror(-ret)));
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}
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return ::ndk::ScopedAStatus(AStatus_newOk());
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}
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} // namespace
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DnsResolverService::DnsResolverService() {
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// register log callback to BnDnsResolver::logFunc
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BnDnsResolver::logFunc =
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std::bind(binderCallLogFn, std::placeholders::_1,
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[](const std::string& msg) { gResNetdCallbacks.log(msg.c_str()); });
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}
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binder_status_t DnsResolverService::start() {
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// TODO: Add disableBackgroundScheduling(true) after libbinder_ndk support it. b/126506010
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// NetdNativeService does call disableBackgroundScheduling currently, so it is fine now.
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DnsResolverService* resolverService = new DnsResolverService();
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binder_status_t status =
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AServiceManager_addService(resolverService->asBinder().get(), getServiceName());
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if (status != STATUS_OK) {
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return status;
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}
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ABinderProcess_startThreadPool();
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// TODO: register log callback if binder NDK backend support it. b/126501406
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return STATUS_OK;
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}
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binder_status_t DnsResolverService::dump(int fd, const char**, uint32_t) {
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auto dump_permission = checkAnyPermission({PERM_DUMP});
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if (!dump_permission.isOk()) {
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return STATUS_PERMISSION_DENIED;
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}
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// This method does not grab any locks. If individual classes need locking
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// their dump() methods MUST handle locking appropriately.
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DumpWriter dw(fd);
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for (auto netId : resolv_list_caches()) {
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dw.println("NetId: %u", netId);
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gDnsResolv->resolverCtrl.dump(dw, netId);
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dw.blankline();
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}
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return STATUS_OK;
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}
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::ndk::ScopedAStatus DnsResolverService::isAlive(bool* alive) {
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ENFORCE_INTERNAL_PERMISSIONS();
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*alive = true;
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return ::ndk::ScopedAStatus(AStatus_newOk());
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}
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::ndk::ScopedAStatus DnsResolverService::registerEventListener(
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const std::shared_ptr<aidl::android::net::metrics::INetdEventListener>& listener) {
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ENFORCE_NETWORK_STACK_PERMISSIONS();
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int res = ResolverEventReporter::getInstance().addListener(listener);
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return statusFromErrcode(res);
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}
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::ndk::ScopedAStatus DnsResolverService::checkAnyPermission(
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const std::vector<const char*>& permissions) {
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// TODO: Remove callback and move this to unnamed namespace after libbiner_ndk supports
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// check_permission.
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if (!gResNetdCallbacks.check_calling_permission) {
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return ::ndk::ScopedAStatus(AStatus_fromExceptionCodeWithMessage(
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EX_NULL_POINTER, "check_calling_permission is null"));
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}
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pid_t pid = AIBinder_getCallingPid();
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uid_t uid = AIBinder_getCallingUid();
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// If the caller is the system UID, don't check permissions.
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// Otherwise, if the system server's binder thread pool is full, and all the threads are
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// blocked on a thread that's waiting for us to complete, we deadlock. http://b/69389492
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//
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// From a security perspective, there is currently no difference, because:
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// 1. The only permissions we check in netd's binder interface are CONNECTIVITY_INTERNAL
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// and NETWORK_STACK, which the system server always has (or MAINLINE_NETWORK_STACK, which
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// is equivalent to having both CONNECTIVITY_INTERNAL and NETWORK_STACK).
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// 2. AID_SYSTEM always has all permissions. See ActivityManager#checkComponentPermission.
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if (uid == AID_SYSTEM) {
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return ::ndk::ScopedAStatus(AStatus_newOk());
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}
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for (const char* permission : permissions) {
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if (gResNetdCallbacks.check_calling_permission(permission)) {
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return ::ndk::ScopedAStatus(AStatus_newOk());
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}
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}
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auto err = StringPrintf("UID %d / PID %d does not have any of the following permissions: %s",
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uid, pid, Join(permissions, ',').c_str());
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return ::ndk::ScopedAStatus(AStatus_fromExceptionCodeWithMessage(EX_SECURITY, err.c_str()));
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}
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namespace {
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// Parse a base64 encoded string into a vector of bytes.
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// On failure, return an empty vector.
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static std::vector<uint8_t> parseBase64(const std::string& input) {
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std::vector<uint8_t> decoded;
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size_t out_len;
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if (EVP_DecodedLength(&out_len, input.size()) != 1) {
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return decoded;
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}
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// out_len is now an upper bound on the output length.
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decoded.resize(out_len);
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if (EVP_DecodeBase64(decoded.data(), &out_len, decoded.size(),
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reinterpret_cast<const uint8_t*>(input.data()), input.size()) == 1) {
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// Possibly shrink the vector if the actual output was smaller than the bound.
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decoded.resize(out_len);
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} else {
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decoded.clear();
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}
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if (out_len != SHA256_SIZE) {
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decoded.clear();
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}
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return decoded;
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}
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} // namespace
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::ndk::ScopedAStatus DnsResolverService::setResolverConfiguration(
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const ResolverParamsParcel& resolverParams) {
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// Locking happens in PrivateDnsConfiguration and res_* functions.
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ENFORCE_INTERNAL_PERMISSIONS();
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// TODO: Remove this log after AIDL gen_log supporting more types, b/129732660
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auto entry =
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gDnsResolverLog.newEntry()
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.prettyFunction(__PRETTY_FUNCTION__)
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.args(resolverParams.netId, resolverParams.servers, resolverParams.domains,
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resolverParams.sampleValiditySeconds, resolverParams.successThreshold,
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resolverParams.minSamples, resolverParams.maxSamples,
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resolverParams.baseTimeoutMsec, resolverParams.retryCount,
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resolverParams.tlsServers, resolverParams.tlsFingerprints);
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std::set<std::vector<uint8_t>> decoded_fingerprints;
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for (const std::string& fingerprint : resolverParams.tlsFingerprints) {
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std::vector<uint8_t> decoded = parseBase64(fingerprint);
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if (decoded.empty()) {
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return ::ndk::ScopedAStatus(AStatus_fromServiceSpecificErrorWithMessage(
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EINVAL, "ResolverController error: bad fingerprint"));
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}
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decoded_fingerprints.emplace(decoded);
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}
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int res =
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gDnsResolv->resolverCtrl.setResolverConfiguration(resolverParams, decoded_fingerprints);
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gResNetdCallbacks.log(entry.returns(res).withAutomaticDuration().toString().c_str());
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return statusFromErrcode(res);
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}
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::ndk::ScopedAStatus DnsResolverService::getResolverInfo(
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int32_t netId, std::vector<std::string>* servers, std::vector<std::string>* domains,
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std::vector<std::string>* tlsServers, std::vector<int32_t>* params,
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std::vector<int32_t>* stats, std::vector<int32_t>* wait_for_pending_req_timeout_count) {
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// Locking happens in PrivateDnsConfiguration and res_* functions.
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ENFORCE_NETWORK_STACK_PERMISSIONS();
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int res = gDnsResolv->resolverCtrl.getResolverInfo(netId, servers, domains, tlsServers, params,
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stats, wait_for_pending_req_timeout_count);
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return statusFromErrcode(res);
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}
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::ndk::ScopedAStatus DnsResolverService::startPrefix64Discovery(int32_t netId) {
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// Locking happens in Dns64Configuration.
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ENFORCE_NETWORK_STACK_PERMISSIONS();
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gDnsResolv->resolverCtrl.startPrefix64Discovery(netId);
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return ::ndk::ScopedAStatus(AStatus_newOk());
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}
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::ndk::ScopedAStatus DnsResolverService::stopPrefix64Discovery(int32_t netId) {
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// Locking happens in Dns64Configuration.
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ENFORCE_NETWORK_STACK_PERMISSIONS();
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gDnsResolv->resolverCtrl.stopPrefix64Discovery(netId);
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return ::ndk::ScopedAStatus(AStatus_newOk());
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}
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::ndk::ScopedAStatus DnsResolverService::getPrefix64(int netId, std::string* stringPrefix) {
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ENFORCE_NETWORK_STACK_PERMISSIONS();
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netdutils::IPPrefix prefix{};
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int res = gDnsResolv->resolverCtrl.getPrefix64(netId, &prefix);
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*stringPrefix = prefix.toString();
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return statusFromErrcode(res);
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}
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::ndk::ScopedAStatus DnsResolverService::setLogSeverity(int32_t logSeverity) {
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ENFORCE_NETWORK_STACK_PERMISSIONS();
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int res = gDnsResolv->setLogSeverity(logSeverity);
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return statusFromErrcode(res);
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}
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::ndk::ScopedAStatus DnsResolverService::destroyNetworkCache(int netId) {
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// Locking happens in res_cache.cpp functions.
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ENFORCE_NETWORK_STACK_PERMISSIONS();
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gDnsResolv->resolverCtrl.destroyNetworkCache(netId);
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return ::ndk::ScopedAStatus(AStatus_newOk());
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}
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::ndk::ScopedAStatus DnsResolverService::createNetworkCache(int netId) {
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// Locking happens in res_cache.cpp functions.
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ENFORCE_NETWORK_STACK_PERMISSIONS();
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int res = gDnsResolv->resolverCtrl.createNetworkCache(netId);
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return statusFromErrcode(res);
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}
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} // namespace net
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} // namespace android
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