/*
* InspIRCd -- Internet Relay Chat Daemon
*
* Copyright (C) 2021 Dominic Hamon
* Copyright (C) 2020 Matt Schatz <genius3000@g3k.solutions>
* Copyright (C) 2018-2019 linuxdaemon <linuxdaemon.irc@gmail.com>
* Copyright (C) 2017-2024 Sadie Powell <sadie@witchery.services>
* Copyright (C) 2013, 2016 Adam <Adam@anope.org>
* Copyright (C) 2013, 2015-2016 Attila Molnar <attilamolnar@hush.com>
* Copyright (C) 2012 Robby <robby@chatbelgie.be>
* Copyright (C) 2009-2010 Daniel De Graaf <danieldg@inspircd.org>
* Copyright (C) 2007 Dennis Friis <peavey@inspircd.org>
* Copyright (C) 2007 Craig Edwards <brain@inspircd.org>
* Copyright (C) 2006-2007, 2009 Robin Burchell <robin+git@viroteck.net>
*
* This file is part of InspIRCd. InspIRCd is free software: you can
* redistribute it and/or modify it under the terms of the GNU General Public
* License as published by the Free Software Foundation, version 2.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef _WIN32
# include <arpa/inet.h>
#endif
#include "inspircd.h"
#include "extension.h"
#include "modules/dns.h"
#include "modules/shun.h"
#include "modules/stats.h"
#include "numerichelper.h"
#include "timeutils.h"
#include "xline.h"
class DNSBLEntry final
{
public:
enum class Action
: uint8_t
{
// G-line users who's IP address is in the DNSBL.
GLINE,
// Kill users who's IP address is in the DNSBL.
KILL,
// K-line users who's IP address is in the DNSBL.
KLINE,
// Mark users who's IP address is in the DNSBL.
MARK,
// Shun users who's IP address is in the DNSBL.
SHUN,
// Z-line users who's IP address is in the DNSBL.
ZLINE,
};
enum class Type
: uint8_t
{
// DNSBL results will be compared against the specified bit mask.
BITMASK,
// DNSBL results will be compared against a numeric range of values.
RECORD,
};
// The action to take against users who's IP address is in this DNSBL.
Action action;
// A bitmask of DNSBL result types to match against.
unsigned int bitmask;
// The domain name of this DNSBL.
std::string domain;
// If action is set to mark then a new hostname to set on users who's IP address is in this DNSBL.
std::string markhost;
// If action is set to mark then a new username to set on users who's IP address is in this DNSBL.
std::string markuser;
// The human readable name of this DNSBL.
std::string name;
// A range of DNSBL result types to match against.
CharState records;
// The message to send to users who's IP address is in a DNSBL.
std::string reason;
// The number of seconds to wait for a DNSBL request before assuming it has failed.
unsigned int timeout;
// The type of result that this DNSBL will provide.
Type type;
// The number of errors which have occurred when querying this DNSBL.
unsigned long stats_errors = 0;
// The number of hits which have occurred when querying this DNSBL.
unsigned long stats_hits = 0;
// The number of misses which have occurred when querying this DNSBL.
unsigned long stats_misses = 0;
// If action is set to gline, kline, or zline then the duration for an X-line to last for.
unsigned long xlineduration;
DNSBLEntry(const Module* mod, const std::shared_ptr<ConfigTag>& tag)
{
name = tag->getString("name");
if (name.empty())
throw ModuleException(mod, "<dnsbl:name> can not be empty at " + tag->source.str());
domain = tag->getString("domain");
if (domain.empty())
throw ModuleException(mod, "<dnsbl:domain> can not be empty at " + tag->source.str());
action = tag->getEnum("action", Action::KILL, {
{ "gline", Action::GLINE },
{ "kill", Action::KILL },
{ "kline", Action::KLINE },
{ "mark", Action::MARK },
{ "shun", Action::SHUN },
{ "zline", Action::ZLINE },
});
const std::string typestr = tag->getString("type");
if (insp::equalsci(typestr, "bitmask"))
{
type = Type::BITMASK;
bitmask = tag->getNum<unsigned int>("bitmask", 0);
records = 0;
}
else if (insp::equalsci(typestr, "record"))
{
type = Type::RECORD;
irc::portparser recordrange(tag->getString("records"), false);
for (long record = 0; (record = recordrange.GetToken()); )
{
if (record < 0 || record > UCHAR_MAX)
throw ModuleException(mod, "<dnsbl:records> can only hold records between 0 and 255 at " + tag->source.str());
records.set(record);
}
}
else
{
throw ModuleException(mod, typestr + " is an invalid value for <dnsbl:type>; acceptable values are 'bitmask' or 'records' at "
+ tag->source.str());
}
reason = tag->getString("reason", "Your IP (%ip%) has been blacklisted by the %dnsbl% DNSBL.", 1, ServerInstance->Config->Limits.MaxLine);
timeout = static_cast<unsigned int>(tag->getDuration("timeout", 0, 1, 60));
markuser = tag->getString("user", tag->getString("ident"));
markhost = tag->getString("host");
xlineduration = tag->getDuration("duration", 60*60, 1);
}
};
class DNSBLMask final
{
public:
// The username to give a user because they were in a DNSBL (<dnsbl:user>).
std::string user;
// The hostname to give a user because they were in a DNSBL (<dnsbl:host>).
std::string host;
// The reason why the user was given this user@host (<dnsbl:reason>).
std::string reason;
DNSBLMask(const std::shared_ptr<DNSBLEntry>& cfg, const std::string& msg)
: user(cfg->markuser)
, host(cfg->markhost)
, reason(msg)
{
}
};
typedef std::vector<std::shared_ptr<DNSBLEntry>> DNSBLEntries;
typedef SimpleExtItem<DNSBLMask> MaskExtItem;
typedef ListExtItem<std::vector<std::string>> MarkExtItem;
// Data which is shared with DNS lookup classes.
class SharedData final
{
private:
std::string ReverseIP(const irc::sockets::sockaddrs& sa)
{
switch (sa.family())
{
case AF_INET:
{
auto a = (unsigned int) sa.in4.sin_addr.s_addr & 0xFF;
auto b = (unsigned int) (sa.in4.sin_addr.s_addr >> 8) & 0xFF;
auto c = (unsigned int) (sa.in4.sin_addr.s_addr >> 16) & 0xFF;
auto d = (unsigned int) (sa.in4.sin_addr.s_addr >> 24) & 0xFF;
return INSP_FORMAT("{}.{}.{}.{}", d, c, b, a);
}
case AF_INET6:
{
const std::string hexaddr = Hex::Encode(sa.in6.sin6_addr.s6_addr, 16);
std::string reversedip;
reversedip.reserve(hexaddr.length() * 2);
for (const auto hexchr : insp::reverse_range(hexaddr))
{
reversedip.push_back(hexchr);
reversedip.push_back('.');
}
reversedip.pop_back();
return reversedip;
}
default:
break;
}
// Clients can't be in a DNSBL if they aren't connected via IPv4 or IPv6.
return {};
}
public:
// Counts the number of DNSBL lookups waiting for this user.
IntExtItem countext;
// Reference to the DNS manager.
DNS::ManagerRef dns;
// The DNSBL entries from the config.
DNSBLEntries dnsbls;
// The DNSBL marks which are set on a user.
MarkExtItem markext;
// The user@host to set on a marked user when they are connected.
MaskExtItem maskext;
SharedData(Module* mod)
: countext(mod, "dnsbl-pending", ExtensionType::USER)
, dns(mod)
, markext(mod, "dnsbl-match", ExtensionType::USER)
, maskext(mod, "dnsbl-mask", ExtensionType::USER)
{
}
// Performs one or more DNSBL lookups on the specified user.
void Lookup(LocalUser* user);
};
class DNSBLResolver final
: public DNS::Request
{
private:
std::shared_ptr<DNSBLEntry> config;
SharedData& data;
const irc::sockets::sockaddrs sa;
const std::string uuid;
template <typename Line, typename... Extra>
void AddLine(const char* type, const std::string& reason, unsigned long duration, LocalUser* user, Extra&&... extra)
{
if (user->exempt)
return; // This user shouldn't be banned.
auto line = new Line(ServerInstance->Time(), duration, MODNAME "@" + ServerInstance->Config->ServerName, reason, std::forward<Extra>(extra)...);
if (!ServerInstance->XLines->AddLine(line, nullptr))
{
ServerInstance->Users.QuitUser(user, "Killed (" + reason + ")");
delete line;
return;
}
ServerInstance->SNO.WriteToSnoMask('x', "{} added a timed {} on {}, expires in {} (on {}): {}",
line->source, type, line->Displayable(), Duration::ToString(line->duration),
Time::ToString(line->expiry), line->reason);
ServerInstance->XLines->ApplyLines();
}
public:
DNSBLResolver(Module* mod, SharedData& sd, const std::string& hostname, LocalUser* u, const std::shared_ptr<DNSBLEntry>& cfg)
: DNS::Request(*sd.dns, mod, hostname, DNS::QUERY_A, true, cfg->timeout)
, config(cfg)
, data(sd)
, sa(u->client_sa)
, uuid(u->uuid)
{
}
/* Note: This may be called multiple times for multiple A record results */
void OnLookupComplete(const DNS::Query* r) override
{
/* Check the user still exists */
LocalUser* them = ServerInstance->Users.FindUUID<LocalUser>(uuid);
if (!them || them->client_sa != sa)
{
config->stats_misses++;
return;
}
intptr_t i = data.countext.Get(them);
if (i)
data.countext.Set(them, i - 1);
// The DNSBL reply must contain an A result.
const DNS::ResourceRecord* const ans_record = r->FindAnswerOfType(DNS::QUERY_A);
if (!ans_record)
{
config->stats_errors++;
ServerInstance->SNO.WriteGlobalSno('d', "{} returned an result with no IPv4 address.",
config->name);
return;
}
// The DNSBL reply must be a valid IPv4 address.
in_addr resultip;
if (inet_pton(AF_INET, ans_record->rdata.c_str(), &resultip) != 1)
{
config->stats_errors++;
ServerInstance->SNO.WriteGlobalSno('d', "{} returned an invalid IPv4 address: {}",
config->name, ans_record->rdata);
return;
}
// The DNSBL reply should be in the 127.0.0.0/8 range.
if ((resultip.s_addr & 0xFF) != 127)
{
config->stats_errors++;
ServerInstance->SNO.WriteGlobalSno('d', "{} returned an IPv4 address which is outside of the 127.0.0.0/8 subnet: {}",
config->name, ans_record->rdata);
return;
}
bool match = false;
unsigned int result = 0;
switch (config->type)
{
case DNSBLEntry::Type::BITMASK:
{
result = (resultip.s_addr >> 24) & config->bitmask;
match = (result != 0);
break;
}
case DNSBLEntry::Type::RECORD:
{
result = resultip.s_addr >> 24;
match = (config->records[result] == 1);
break;
}
}
if (match)
{
const std::string reason = Template::Replace(config->reason, {
{ "dnsbl", config->name },
{ "dnsbl.url", Percent::Encode(config->name) },
{ "ip", them->GetAddress() },
{ "network", ServerInstance->Config->Network },
{ "network.url", Percent::Encode(ServerInstance->Config->Network) },
{ "result", ConvToStr(result) },
});
config->stats_hits++;
switch (config->action)
{
case DNSBLEntry::Action::KILL:
{
if (!them->exempt)
ServerInstance->Users.QuitUser(them, "Killed (" + reason + ")");
break;
}
case DNSBLEntry::Action::MARK:
{
if (!config->markuser.empty() || !config->markhost.empty())
{
// Store the u@h mask for later to avoid being overwritten by username/hostname lookups.
data.maskext.SetFwd(them, config, reason);
// If the user is already connected we should just do this now.
if (them->IsFullyConnected())
creator->OnUserConnect(them);
}
data.markext.GetRef(them).push_back(config->name);
break;
}
case DNSBLEntry::Action::KLINE:
{
AddLine<KLine>("K-line", reason, config->xlineduration, them, them->GetBanUser(true), them->GetAddress());
break;
}
case DNSBLEntry::Action::GLINE:
{
AddLine<GLine>("G-line", reason, config->xlineduration, them, them->GetBanUser(true), them->GetAddress());
break;
}
case DNSBLEntry::Action::ZLINE:
{
AddLine<ZLine>("Z-line", reason, config->xlineduration, them, them->GetAddress());
break;
}
case DNSBLEntry::Action::SHUN:
{
AddLine<Shun>("Shun", reason, config->xlineduration, them, them->GetAddress());
break;
}
}
ServerInstance->SNO.WriteGlobalSno('d', "{} {} ({}) detected as being on the '{}' DNSBL with result {}{}",
them->IsFullyConnected() ? "User" : "Connecting user", them->GetRealMask(), them->GetAddress(),
config->name, result, them->exempt ? " -- exempt" : "");
}
else
config->stats_misses++;
}
void OnError(const DNS::Query* q) override
{
bool is_miss = true;
switch (q->error)
{
case DNS::ERROR_NO_RECORDS:
case DNS::ERROR_DOMAIN_NOT_FOUND:
config->stats_misses++;
break;
default:
config->stats_errors++;
is_miss = false;
break;
}
LocalUser* them = ServerInstance->Users.FindUUID<LocalUser>(uuid);
if (!them || them->client_sa != sa)
return;
intptr_t i = data.countext.Get(them);
if (i)
data.countext.Set(them, i - 1);
if (is_miss)
return;
ServerInstance->SNO.WriteGlobalSno('d', "An error occurred whilst checking whether {} ({}) is on the '{}' DNSBL: {}",
them->GetRealMask(), them->GetAddress(), config->name, data.dns->GetErrorStr(q->error));
}
};
class CommandDNSBL final
: public Command
{
private:
SharedData& data;
public:
CommandDNSBL(Module* mod, SharedData& sd)
: Command(mod, "DNSBL", 1, 2)
, data(sd)
{
access_needed = CmdAccess::OPERATOR;
syntax = { "[<nick> [<reason>]]" };
translation = { TR_NICK, TR_TEXT };
}
CmdResult Handle(User* user, const Params& parameters) override
{
User* target;
if (IS_LOCAL(user))
target = ServerInstance->Users.FindNick(parameters[0], true);
else
target = ServerInstance->Users.FindUUID(parameters[0], true);
// We couldn't find the user so just give up.
if (!target)
{
user->WriteNumeric(Numerics::NoSuchNick(parameters[0]));
return CmdResult::FAILURE;
}
auto* ltarget = IS_LOCAL(target);
if (!ltarget)
return CmdResult::SUCCESS; // The user is on another server so just let it forward.
intptr_t count = data.countext.Get(ltarget);
if (count)
{
// TODO: replace this with a FAIL stdrpl when we can network those.
user->WriteRemoteNotice("*** DNSBL: Unable to recheck {}: still waiting on {} DNSBLs from the previous check.",
ltarget->nick, count);
return CmdResult::FAILURE;
}
// TODO: replace this with a NOTE stdrpl when we can network those.
user->WriteRemoteNotice("*** DNSBL: Rechecking {} against {} DNSBLs.", ltarget->nick, data.dnsbls.size());
const bool has_reason = parameters.size() > 1;
ServerInstance->SNO.WriteGlobalSno('d', "{} is rechecking whether {} ({}) is in a DNSBL{}{}", user->nick,
ltarget->nick, ltarget->GetAddress(), has_reason ? ": " : "", has_reason ? parameters[1] : ".");
data.Lookup(ltarget);
return CmdResult::SUCCESS;
}
RouteDescriptor GetRouting(User* user, const Params& parameters) override
{
return ROUTE_OPT_UCAST(parameters[0]);
}
};
void SharedData::Lookup(LocalUser* user)
{
if (!dns)
return; // The core_dns module is not loaded.
if (!user->GetClass()->config->getBool("usednsbl", true))
return; // The user's class is exempt from DNSBL lookups.
const std::string reversedip = ReverseIP(user->client_sa);
ServerInstance->Logs.Debug(MODNAME, "Reversed IP {} => {}", user->GetAddress(), reversedip);
countext.Set(user, dnsbls.size());
// For each DNSBL, we will run through this lookup
for (const auto& dnsbl : dnsbls)
{
// Fill hostname with a dnsbl style host (d.c.b.a.domain.tld)
const std::string hostname = reversedip + "." + dnsbl->domain;
// Try to do the DNSBL lookup.
auto* r = new DNSBLResolver(dns->creator, *this, hostname, user, dnsbl);
try
{
dns->Process(r);
}
catch (const DNS::Exception& ex)
{
delete r;
ServerInstance->Logs.Debug(MODNAME, "DNSBL lookup error: {}", ex.GetReason());
}
if (user->quitting)
break; // DNS resolver found a cached hit.
}
}
class ModuleDNSBL final
: public Module
, public Stats::EventListener
{
private:
SharedData data;
CommandDNSBL cmd;
public:
ModuleDNSBL()
: Module(VF_VENDOR, "Allows the server administrator to check the IP address of connecting users against a DNSBL.")
, Stats::EventListener(this)
, data(this)
, cmd(this, data)
{
}
void init() override
{
ServerInstance->SNO.EnableSnomask('d', "DNSBL");
}
void Prioritize() override
{
Module* corexline = ServerInstance->Modules.Find("core_xline");
ServerInstance->Modules.SetPriority(this, I_OnChangeRemoteAddress, PRIORITY_AFTER, corexline);
}
void ReadConfig(ConfigStatus& status) override
{
DNSBLEntries newdnsbls;
for (const auto& [_, tag] : ServerInstance->Config->ConfTags("dnsbl"))
{
auto entry = std::make_shared<DNSBLEntry>(this, tag);
newdnsbls.push_back(entry);
}
data.dnsbls.swap(newdnsbls);
}
void OnChangeRemoteAddress(LocalUser* user) override
{
if (!user->quitting && user->GetClass())
data.Lookup(user);
}
ModResult OnPreChangeConnectClass(LocalUser* user, const std::shared_ptr<ConnectClass>& klass, std::optional<Numeric::Numeric>& errnum) override
{
const std::string dnsbl = klass->config->getString("dnsbl");
if (dnsbl.empty())
return MOD_RES_PASSTHRU;
MarkExtItem::List* match = data.markext.Get(user);
if (!match)
{
ServerInstance->Logs.Debug("CONNECTCLASS", "The {} connect class is not suitable as it requires a DNSBL mark.",
klass->GetName());
return MOD_RES_DENY;
}
for (const auto& mark : *match)
{
if (InspIRCd::Match(mark, dnsbl))
return MOD_RES_PASSTHRU;
}
ServerInstance->Logs.Debug("CONNECTCLASS", "The {} connect class is not suitable as the DNSBL marks ({}) do not match {}.",
klass->GetName(), insp::join(*match, ", "), dnsbl);
return MOD_RES_DENY;
}
ModResult OnCheckReady(LocalUser* user) override
{
// Block until all of the DNSBL lookups are complete.
return data.countext.Get(user) ? MOD_RES_DENY : MOD_RES_PASSTHRU;
}
void OnUserConnect(LocalUser* user) override
{
DNSBLMask* ih = data.maskext.Get(user);
if (ih)
{
if (!ih->user.empty())
{
user->ChangeDisplayedUser(ih->user);
user->WriteNotice("Your username has been set to " + ih->user + ": " + ih->reason);
}
if (!ih->host.empty())
{
user->ChangeDisplayedHost(ih->host);
user->WriteNotice("Your hostname has been set to " + ih->host + ": " + ih->reason);
}
data.maskext.Unset(user);
}
}
ModResult OnStats(Stats::Context& stats) override
{
if (stats.GetSymbol() != 'd')
return MOD_RES_PASSTHRU;
unsigned long total_hits = 0;
unsigned long total_misses = 0;
unsigned long total_errors = 0;
for (const auto& dnsbl : data.dnsbls)
{
total_hits += dnsbl->stats_hits;
total_misses += dnsbl->stats_misses;
total_errors += dnsbl->stats_errors;
stats.AddGenericRow(INSP_FORMAT("The \"{}\" DNSBL had {} hits, {} misses, and {} errors",
dnsbl->name, dnsbl->stats_hits, dnsbl->stats_misses, dnsbl->stats_errors));
}
stats.AddGenericRow("Total DNSBL hits: " + ConvToStr(total_hits));
stats.AddGenericRow("Total DNSBL misses: " + ConvToStr(total_misses));
stats.AddGenericRow("Total DNSBL errors: " + ConvToStr(total_errors));
return MOD_RES_DENY;
}
};
MODULE_INIT(ModuleDNSBL)
