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Commit fbe1ab5b authored by Luke Huang's avatar Luke Huang Committed by Automerger Merge Worker
Browse files

Skip the legacy stats recording if DNS requests are denied by network policy am: 8c45bfb8 

Change-Id: I49b2953515ba34861579724801f995511a79fc69
parents f9f30e3f 8c45bfb8

Android.bp

+1 −0
Original line number Diff line number Diff line
@@ -262,6 +262,7 @@ cc_test { 
    ],

    static_libs: [

        "dnsresolver_aidl_interface-unstable-ndk_platform",

        "netd_aidl_interface-ndk_platform",

        "netd_event_listener_interface-ndk_platform",

        "libcutils",

        "libgmock",

res_send.cpp

+24 −9
Original line number Diff line number Diff line
@@ -411,6 +411,15 @@ static DnsQueryEvent* addDnsQueryEvent(NetworkDnsEventReported* event) { 
    return event->mutable_dns_query_events()->add_dns_query_event();

}



static bool isNetworkRestricted(int terrno) {

    // It's possible that system was in some network restricted mode, which blocked

    // the operation of sending packet and resulted in EPERM errno.

    // It would be no reason to keep retrying on that case.

    // TODO: Check the system status to know if network restricted mode is

    // enabled.

    return (terrno == EPERM);

}



int res_nsend(res_state statp, const uint8_t* buf, int buflen, uint8_t* ans, int anssiz, int* rcode,

              uint32_t flags, std::chrono::milliseconds sleepTimeMs) {

    LOG(DEBUG) << __func__;
@@ -537,14 +546,14 @@ int res_nsend(res_state statp, const uint8_t* buf, int buflen, uint8_t* ans, int 
                    // TCP fallback retry and current server does not support TCP connectin

                    useTcp = false;

                }

                LOG(INFO) << __func__ << ": used send_vc " << resplen;

                LOG(INFO) << __func__ << ": used send_vc " << resplen << " terrno: " << terrno;

            } else {

                // UDP

                resplen = send_dg(statp, &params, buf, buflen, ans, anssiz, &terrno, &actualNs,

                                  &useTcp, &gotsomewhere, &query_time, rcode, &delay);

                fallbackTCP = useTcp ? true : false;

                retry_count_for_event = attempt;

                LOG(INFO) << __func__ << ": used send_dg " << resplen;

                LOG(INFO) << __func__ << ": used send_dg " << resplen << " terrno: " << terrno;

            }



            const IPSockAddr& receivedServerAddr = statp->nsaddrs[actualNs];
@@ -568,13 +577,19 @@ int res_nsend(res_state statp, const uint8_t* buf, int buflen, uint8_t* ans, int 
            // queries that deterministically fail (e.g., a name that always returns

            // SERVFAIL or times out) do not unduly affect the stats.

            if (shouldRecordStats) {

                // (b/151166599): This is a workaround to prevent that DnsResolver calculates the

                // reliability of DNS servers from being broken when network restricted mode is

                // enabled.

                // TODO: Introduce the new server selection instead of skipping stats recording.

                if (!isNetworkRestricted(terrno)) {

                    res_sample sample;

                    res_stats_set_sample(&sample, query_time, *rcode, delay);

                // KeepListening UDP mechanism is incompatible with usable_servers of legacy stats,

                // so keep the old logic for now.

                    // KeepListening UDP mechanism is incompatible with usable_servers of legacy

                    // stats, so keep the old logic for now.

                    // TODO: Replace usable_servers of legacy stats with new one.

                resolv_cache_add_resolver_stats_sample(statp->netid, revision_id, serverSockAddr,

                                                       sample, params.max_samples);

                    resolv_cache_add_resolver_stats_sample(

                            statp->netid, revision_id, serverSockAddr, sample, params.max_samples);

                }

                resolv_stats_add(statp->netid, receivedServerAddr, dnsQueryEvent);

            }

tests/Android.bp

+2 −0
Original line number Diff line number Diff line
@@ -11,8 +11,10 @@ cc_test_library { 
        "libutils",

    ],

    static_libs: [

        "netd_aidl_interface-ndk_platform",

        "libnetd_test_dnsresponder_ndk",

        "libnetdutils",

        "libgmock",

    ],

}

tests/resolv_integration_test.cpp

+36 −31
Original line number Diff line number Diff line
@@ -73,9 +73,6 @@ 
constexpr int TEST_VPN_NETID = 65502;

constexpr int MAXPACKET = (8 * 1024);



// Use maximum reserved appId for applications to avoid conflict with existing uids.

static const int TEST_UID = 99999;



// Semi-public Bionic hook used by the NDK (frameworks/base/native/android/net.c)

// Tested here for convenience.

extern "C" int android_getaddrinfofornet(const char* hostname, const char* servname,
@@ -4004,24 +4001,7 @@ TEST_F(ResolverTest, BlockDnsQueryWithUidRule) { 
    dns1.clearQueries();

    dns2.clearQueries();



    // Add drop rule for TEST_UID. Also enable the standby chain because it might not be enabled.

    // Unfortunately we cannot use FIREWALL_CHAIN_NONE, or custom iptables rules, for this purpose

    // because netd calls fchown() on the DNS query sockets, and "iptables -m owner" matches the

    // UID of the socket creator, not the UID set by fchown().

    //

    // TODO: migrate FIREWALL_CHAIN_NONE to eBPF as well.

    EXPECT_TRUE(netdService->firewallEnableChildChain(INetd::FIREWALL_CHAIN_STANDBY, true).isOk());

    EXPECT_TRUE(netdService

                        ->firewallSetUidRule(INetd::FIREWALL_CHAIN_STANDBY, TEST_UID,

                                             INetd::FIREWALL_RULE_DENY)

                        .isOk());



    // Save uid

    int suid = getuid();



    // Switch to TEST_UID

    EXPECT_TRUE(seteuid(TEST_UID) == 0);



    ScopeBlockedUIDRule scopeBlockUidRule(netdService, TEST_UID);

    // Dns Query

    int fd1 = resNetworkQuery(TEST_NETID, host_name, ns_c_in, ns_t_a, 0);

    int fd2 = resNetworkQuery(TEST_NETID, host_name, ns_c_in, ns_t_aaaa, 0);
@@ -4036,16 +4016,6 @@ TEST_F(ResolverTest, BlockDnsQueryWithUidRule) { 
    memset(buf, 0, MAXPACKET);

    res = getAsyncResponse(fd1, &rcode, buf, MAXPACKET);

    EXPECT_EQ(-ECONNREFUSED, res);



    // Restore uid

    EXPECT_TRUE(seteuid(suid) == 0);



    // Remove drop rule for TEST_UID, and disable the standby chain.

    EXPECT_TRUE(netdService

                        ->firewallSetUidRule(INetd::FIREWALL_CHAIN_STANDBY, TEST_UID,

                                             INetd::FIREWALL_RULE_ALLOW)

                        .isOk());

    EXPECT_TRUE(netdService->firewallEnableChildChain(INetd::FIREWALL_CHAIN_STANDBY, false).isOk());

}



namespace {
@@ -4996,3 +4966,38 @@ TEST_F(ResolverTest, GetAddrInfoParallelLookupSleepTime) { 
    EXPECT_GT(PARALLEL_LOOKUP_SLEEP_TIME_MS, timeTakenMs);

    EXPECT_EQ(0U, GetNumQueries(dns, kHelloExampleCom));

}



TEST_F(ResolverTest, BlockDnsQueryUidDoesNotLeadToBadServer) {

    // This test relies on blocking traffic on loopback, which xt_qtaguid does not do.

    // See aosp/358413 and b/34444781 for why.

    SKIP_IF_BPF_NOT_SUPPORTED;



    constexpr char listen_addr1[] = "127.0.0.4";

    constexpr char listen_addr2[] = "::1";

    test::DNSResponder dns1(listen_addr1);

    test::DNSResponder dns2(listen_addr2);

    StartDns(dns1, {});

    StartDns(dns2, {});



    std::vector<std::string> servers = {listen_addr1, listen_addr2};

    ASSERT_TRUE(mDnsClient.SetResolversForNetwork(servers));

    dns1.clearQueries();

    dns2.clearQueries();

    {

        ScopeBlockedUIDRule scopeBlockUidRule(mDnsClient.netdService(), TEST_UID);

        // Start querying ten times.

        for (int i = 0; i < 10; i++) {

            std::string hostName = fmt::format("blocked{}.com", i);

            const addrinfo hints = {.ai_family = AF_INET, .ai_socktype = SOCK_DGRAM};

            EXPECT_EQ(safe_getaddrinfo(hostName.c_str(), nullptr, &hints), nullptr);

        }

    }

    // Since all query packets are blocked, we should not see any stats of them.

    const std::vector<NameserverStats> expectedEmptyDnsStats = {

            NameserverStats(listen_addr1),

            NameserverStats(listen_addr2),

    };

    expectStatsFromGetResolverInfo(expectedEmptyDnsStats);

    EXPECT_EQ(dns1.queries().size(), 0U);

    EXPECT_EQ(dns2.queries().size(), 0U);

}

tests/resolv_test_utils.h

+37 −0
Original line number Diff line number Diff line
@@ -23,10 +23,45 @@ 
#include <string>

#include <vector>



#include <aidl/android/net/INetd.h>

#include <gtest/gtest.h>

#include <netdutils/InternetAddresses.h>



#include "dns_responder/dns_responder.h"



class ScopeBlockedUIDRule {

    using INetd = aidl::android::net::INetd;



  public:

    ScopeBlockedUIDRule(INetd* netSrv, uid_t testUid)

        : mNetSrv(netSrv), mTestUid(testUid), mSavedUid(getuid()) {

        // Add drop rule for testUid. Also enable the standby chain because it might not be

        // enabled. Unfortunately we cannot use FIREWALL_CHAIN_NONE, or custom iptables rules, for

        // this purpose because netd calls fchown() on the DNS query sockets, and "iptables -m

        // owner" matches the UID of the socket creator, not the UID set by fchown().

        // TODO: migrate FIREWALL_CHAIN_NONE to eBPF as well.

        EXPECT_TRUE(mNetSrv->firewallEnableChildChain(INetd::FIREWALL_CHAIN_STANDBY, true).isOk());

        EXPECT_TRUE(mNetSrv->firewallSetUidRule(INetd::FIREWALL_CHAIN_STANDBY, mTestUid,

                                                INetd::FIREWALL_RULE_DENY)

                            .isOk());

        EXPECT_TRUE(seteuid(mTestUid) == 0);

    };

    ~ScopeBlockedUIDRule() {

        // Restore uid

        EXPECT_TRUE(seteuid(mSavedUid) == 0);

        // Remove drop rule for testUid, and disable the standby chain.

        EXPECT_TRUE(mNetSrv->firewallSetUidRule(INetd::FIREWALL_CHAIN_STANDBY, mTestUid,

                                                INetd::FIREWALL_RULE_ALLOW)

                            .isOk());

        EXPECT_TRUE(mNetSrv->firewallEnableChildChain(INetd::FIREWALL_CHAIN_STANDBY, false).isOk());

    }



  private:

    INetd* mNetSrv;

    const uid_t mTestUid;

    const uid_t mSavedUid;

};



struct DnsRecord {

    std::string host_name;  // host name

    ns_type type;           // record type
@@ -35,6 +70,8 @@ struct DnsRecord { 


// TODO: make this dynamic and stop depending on implementation details.

constexpr int TEST_NETID = 30;

// Use maximum reserved appId for applications to avoid conflict with existing uids.

constexpr int TEST_UID = 99999;



static constexpr char kLocalHost[] = "localhost";

static constexpr char kLocalHostAddr[] = "127.0.0.1";