zeek/src/DNS_Mapping.cc

// See the file "COPYING" in the main distribution directory for copyright.

#include "zeek/DNS_Mapping.h"

#include <ares_nameser.h>
#include <cinttypes>

#include "zeek/DNS_Mgr.h"
#include "zeek/Reporter.h"

#include "zeek/3rdparty/doctest.h"

namespace zeek::detail {

DNS_Mapping::DNS_Mapping(std::string host, struct hostent* h, uint32_t ttl, int type) {
    Init(h);
    req_host = host;
    req_ttl = ttl;
    req_type = type;

    if ( names.empty() )
        names.push_back(std::move(host));
}

DNS_Mapping::DNS_Mapping(const IPAddr& addr, struct hostent* h, uint32_t ttl) {
    Init(h);
    req_addr = addr;
    req_ttl = ttl;
    req_type = T_PTR;
}

DNS_Mapping::DNS_Mapping(FILE* f) {
    Clear();
    init_failed = true;

    req_ttl = 0;
    creation_time = 0;

    char buf[512];

    if ( ! fgets(buf, sizeof(buf), f) ) {
        no_mapping = true;
        return;
    }

    char req_buf[512 + 1];
    char name_buf[512 + 1];
    int is_req_host;
    int failed_local;
    int num_addrs;

    if ( sscanf(buf, "%lf %d %512s %d %512s %d %d %" SCNu32, &creation_time, &is_req_host, req_buf, &failed_local,
                name_buf, &req_type, &num_addrs, &req_ttl) != 8 ) {
        no_mapping = true;
        return;
    }

    failed = static_cast<bool>(failed_local);

    if ( is_req_host )
        req_host = req_buf;
    else
        req_addr = IPAddr(req_buf);

    names.emplace_back(name_buf);

    for ( int i = 0; i < num_addrs; ++i ) {
        if ( ! fgets(buf, sizeof(buf), f) )
            return;

        char* newline = strchr(buf, '\n');
        if ( newline )
            *newline = '\0';

        addrs.emplace_back(buf);
    }

    init_failed = false;
}

ListValPtr DNS_Mapping::Addrs() {
    if ( failed )
        return nullptr;

    if ( ! addrs_val ) {
        addrs_val = make_intrusive<ListVal>(TYPE_ADDR);

        for ( const auto& addr : addrs )
            addrs_val->Append(make_intrusive<AddrVal>(addr));
    }

    return addrs_val;
}

TableValPtr DNS_Mapping::AddrsSet() {
    auto l = Addrs();

    if ( ! l || l->Length() == 0 )
        return DNS_Mgr::empty_addr_set();

    return l->ToSetVal();
}

StringValPtr DNS_Mapping::Host() {
    if ( failed || names.empty() )
        return nullptr;

    if ( ! host_val )
        host_val = make_intrusive<StringVal>(names[0]);

    return host_val;
}

void DNS_Mapping::Init(struct hostent* h) {
    no_mapping = false;
    init_failed = false;
    creation_time = util::current_time();
    host_val = nullptr;
    addrs_val = nullptr;

    if ( ! h ) {
        Clear();
        return;
    }

    if ( h->h_name )
        // for now, just use the official name
        // TODO: this could easily be expanded to include all of the aliases as well
        names.emplace_back(h->h_name);

    if ( h->h_addr_list ) {
        for ( int i = 0; h->h_addr_list[i] != nullptr; ++i ) {
            if ( h->h_addrtype == AF_INET )
                addrs.emplace_back(IPv4, (uint32_t*)h->h_addr_list[i], IPAddr::Network);
            else if ( h->h_addrtype == AF_INET6 )
                addrs.emplace_back(IPv6, (uint32_t*)h->h_addr_list[i], IPAddr::Network);
        }
    }

    failed = false;
}

void DNS_Mapping::Clear() {
    names.clear();
    host_val = nullptr;
    addrs.clear();
    addrs_val = nullptr;
    no_mapping = false;
    req_type = 0;
    failed = true;
}

void DNS_Mapping::Save(FILE* f) const {
    fprintf(f, "%.0f %d %s %d %s %d %zu %" PRIu32 "\n", creation_time, ! req_host.empty(),
            req_host.empty() ? req_addr.AsString().c_str() : req_host.c_str(), failed,
            names.empty() ? "*" : names[0].c_str(), req_type, addrs.size(), req_ttl);

    for ( const auto& addr : addrs )
        fprintf(f, "%s\n", addr.AsString().c_str());
}

void DNS_Mapping::Merge(const DNS_MappingPtr& other) {
    std::copy(other->names.begin(), other->names.end(), std::back_inserter(names));
    std::copy(other->addrs.begin(), other->addrs.end(), std::back_inserter(addrs));
}

// This value needs to be incremented if something changes in the data stored by Save(). This
// allows us to change the structure of the cache without breaking something in DNS_Mgr.
constexpr int FILE_VERSION = 1;

void DNS_Mapping::InitializeCache(FILE* f) { fprintf(f, "%d\n", FILE_VERSION); }

bool DNS_Mapping::ValidateCacheVersion(FILE* f) {
    char buf[512];
    if ( ! fgets(buf, sizeof(buf), f) )
        return false;

    int version;
    if ( sscanf(buf, "%d", &version) != 1 ) {
        reporter->Warning("Existing DNS cache did not have correct version, ignoring");
        return false;
    }

    return FILE_VERSION == version;
}

//////////////////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////////////////

TEST_CASE("dns_mapping init null hostent") {
    DNS_Mapping mapping("www.apple.com", nullptr, 123, T_A);

    CHECK(! mapping.Valid());
    CHECK(mapping.Addrs() == nullptr);
    CHECK(mapping.AddrsSet()->EqualTo(DNS_Mgr::empty_addr_set()));
    CHECK(mapping.Host() == nullptr);
}

TEST_CASE("dns_mapping init host") {
    IPAddr addr("1.2.3.4");
    in4_addr in4;
    addr.CopyIPv4(&in4);

    struct hostent he;
    he.h_name = util::copy_string("testing.home");
    he.h_aliases = nullptr;
    he.h_addrtype = AF_INET;
    he.h_length = sizeof(in_addr);

    std::vector<in_addr*> addrs = {&in4, nullptr};
    he.h_addr_list = reinterpret_cast<char**>(addrs.data());

    DNS_Mapping mapping("testing.home", &he, 123, T_A);
    CHECK(mapping.Valid());
    CHECK(mapping.ReqAddr() == IPAddr::v6_unspecified);
    CHECK(strcmp(mapping.ReqHost(), "testing.home") == 0);
    CHECK(mapping.ReqStr() == "testing.home");

    auto lva = mapping.Addrs();
    REQUIRE(lva != nullptr);
    CHECK(lva->Length() == 1);
    auto lvae = lva->Idx(0)->AsAddrVal();
    REQUIRE(lvae != nullptr);
    CHECK(lvae->Get().AsString() == "1.2.3.4");

    auto tvas = mapping.AddrsSet();
    REQUIRE(tvas != nullptr);
    CHECK_FALSE(tvas->EqualTo(DNS_Mgr::empty_addr_set()));

    auto svh = mapping.Host();
    REQUIRE(svh != nullptr);
    CHECK(svh->ToStdString() == "testing.home");

    delete[] he.h_name;
}

TEST_CASE("dns_mapping init addr") {
    IPAddr addr("1.2.3.4");
    in4_addr in4;
    addr.CopyIPv4(&in4);

    struct hostent he;
    he.h_name = util::copy_string("testing.home");
    he.h_aliases = nullptr;
    he.h_addrtype = AF_INET;
    he.h_length = sizeof(in_addr);

    std::vector<in_addr*> addrs = {&in4, nullptr};
    he.h_addr_list = reinterpret_cast<char**>(addrs.data());

    DNS_Mapping mapping(addr, &he, 123);
    CHECK(mapping.Valid());
    CHECK(mapping.ReqAddr() == addr);
    CHECK(mapping.ReqHost() == nullptr);
    CHECK(mapping.ReqStr() == "1.2.3.4");

    auto lva = mapping.Addrs();
    REQUIRE(lva != nullptr);
    CHECK(lva->Length() == 1);
    auto lvae = lva->Idx(0)->AsAddrVal();
    REQUIRE(lvae != nullptr);
    CHECK(lvae->Get().AsString() == "1.2.3.4");

    auto tvas = mapping.AddrsSet();
    REQUIRE(tvas != nullptr);
    CHECK_FALSE(tvas->EqualTo(DNS_Mgr::empty_addr_set()));

    auto svh = mapping.Host();
    REQUIRE(svh != nullptr);
    CHECK(svh->ToStdString() == "testing.home");

    delete[] he.h_name;
}

TEST_CASE("dns_mapping save reload") {
    // TODO: this test uses fmemopen and mkdtemp, both of which aren't available on
    // Windows. We'll have to figure out another way to do this test there.
#ifndef _MSC_VER
    IPAddr addr("1.2.3.4");
    in4_addr in4;
    addr.CopyIPv4(&in4);

    struct hostent he;
    he.h_name = util::copy_string("testing.home");
    he.h_aliases = nullptr;
    he.h_addrtype = AF_INET;
    he.h_length = sizeof(in_addr);

    std::vector<in_addr*> addrs = {&in4, nullptr};
    he.h_addr_list = reinterpret_cast<char**>(addrs.data());

    // Create a temporary file in memory and fseek to the end of it so we're at
    // EOF for the next bit.
    char buffer[4096];
    memset(buffer, 0, 4096);
    FILE* tmpfile = fmemopen(buffer, 4096, "r+");
    if ( fseek(tmpfile, 0, SEEK_END) < 0 )
        reporter->Error("DNS_Mapping: seek failed");

    // Try loading from the file at EOF. This should cause a mapping failure.
    DNS_Mapping mapping(tmpfile);
    CHECK(mapping.NoMapping());
    fseek(tmpfile, 0, SEEK_SET);

    // Try reading from the empty file. This should cause an init failure.
    DNS_Mapping mapping2(tmpfile);
    CHECK(mapping2.InitFailed());
    fseek(tmpfile, 0, SEEK_SET);

    // Save a valid mapping into the file and rewind to the start.
    DNS_Mapping mapping3(addr, &he, 123);
    mapping3.Save(tmpfile);
    fseek(tmpfile, 0, SEEK_SET);

    // Test loading the mapping back out of the file
    DNS_Mapping mapping4(tmpfile);
    fclose(tmpfile);
    CHECK(mapping4.Valid());
    CHECK(mapping4.ReqAddr() == addr);
    CHECK(mapping4.ReqHost() == nullptr);
    CHECK(mapping4.ReqStr() == "1.2.3.4");

    auto lva = mapping4.Addrs();
    REQUIRE(lva != nullptr);
    CHECK(lva->Length() == 1);
    auto lvae = lva->Idx(0)->AsAddrVal();
    REQUIRE(lvae != nullptr);
    CHECK(lvae->Get().AsString() == "1.2.3.4");

    auto tvas = mapping4.AddrsSet();
    REQUIRE(tvas != nullptr);
    CHECK(tvas != DNS_Mgr::empty_addr_set());

    auto svh = mapping4.Host();
    REQUIRE(svh != nullptr);
    CHECK(svh->ToStdString() == "testing.home");

    delete[] he.h_name;
#endif
}

TEST_CASE("dns_mapping multiple addresses") {
    IPAddr addr("1.2.3.4");
    in4_addr in4_1;
    addr.CopyIPv4(&in4_1);

    IPAddr addr2("5.6.7.8");
    in4_addr in4_2;
    addr2.CopyIPv4(&in4_2);

    struct hostent he;
    he.h_name = util::copy_string("testing.home");
    he.h_aliases = nullptr;
    he.h_addrtype = AF_INET;
    he.h_length = sizeof(in_addr);

    std::vector<in_addr*> addrs = {&in4_1, &in4_2, nullptr};
    he.h_addr_list = reinterpret_cast<char**>(addrs.data());

    DNS_Mapping mapping("testing.home", &he, 123, T_A);
    CHECK(mapping.Valid());

    auto lva = mapping.Addrs();
    REQUIRE(lva != nullptr);
    CHECK(lva->Length() == 2);

    auto lvae = lva->Idx(0)->AsAddrVal();
    REQUIRE(lvae != nullptr);
    CHECK(lvae->Get().AsString() == "1.2.3.4");

    lvae = lva->Idx(1)->AsAddrVal();
    REQUIRE(lvae != nullptr);
    CHECK(lvae->Get().AsString() == "5.6.7.8");

    delete[] he.h_name;
}

TEST_CASE("dns_mapping ipv6") {
    IPAddr addr("64:ff9b:1::");
    in6_addr in6;
    addr.CopyIPv6(&in6);

    struct hostent he;
    he.h_name = util::copy_string("testing.home");
    he.h_aliases = nullptr;
    he.h_addrtype = AF_INET6;
    he.h_length = sizeof(in6_addr);

    std::vector<in6_addr*> addrs = {&in6, nullptr};
    he.h_addr_list = reinterpret_cast<char**>(addrs.data());

    DNS_Mapping mapping(addr, &he, 123);
    CHECK(mapping.Valid());
    CHECK(mapping.ReqAddr() == addr);
    CHECK(mapping.ReqHost() == nullptr);
    CHECK(mapping.ReqStr() == "64:ff9b:1::");

    auto lva = mapping.Addrs();
    REQUIRE(lva != nullptr);
    CHECK(lva->Length() == 1);
    auto lvae = lva->Idx(0)->AsAddrVal();
    REQUIRE(lvae != nullptr);
    CHECK(lvae->Get().AsString() == "64:ff9b:1::");

    delete[] he.h_name;
}

} // namespace zeek::detail