Add initial automated connection throttling

CHANGELOG.md

@@ -11,15 +11,17 @@ New release of Oragono!
 
 ### Added
 * Added ARM build (for Raspberry PIs and similar).
-* Added `KLINE` and `UNDLINE` commands. Complementing `KLINE`, this lets you ban masks from the server.
+* Added automated connection throttling! To enable this, copy the `connection-throttling` section from the config.
+* Added `KLINE` and `UNDLINE` commands. Complementing `DLINE`'s per-IP and per-network bans, this lets you ban masks from the server.
 
 ### Changed
+* Connection limits can now be freely enabled or disabled. To enable automated limit handling, see the new `enabled` flag in the config, under `connection-limits`.
 
 ### Removed
 
 ### Fixed
 * Fixed an issue where `UNDLINE` didn't save across server launches.
-* Removed several race conditions and made the server more resiliant to these bugs.
+* Removed several race conditions which could result in server panics.
 
 
 ## [0.5.0] - 2016-12-10

irc/config.go

@@ -12,6 +12,7 @@ import (
 	"io/ioutil"
 	"log"
 	"strings"
+	"time"
 
 	"gopkg.in/yaml.v2"
 )
@@ -95,12 +96,26 @@ type RestAPIConfig struct {
 }
 
 type ConnectionLimitsConfig struct {
+	Enabled     bool
 	CidrLenIPv4 int `yaml:"cidr-len-ipv4"`
 	CidrLenIPv6 int `yaml:"cidr-len-ipv6"`
 	IPsPerCidr  int `yaml:"ips-per-subnet"`
 	Exempted    []string
 }
 
+type ConnectionThrottleConfig struct {
+	Enabled            bool
+	CidrLenIPv4        int           `yaml:"cidr-len-ipv4"`
+	CidrLenIPv6        int           `yaml:"cidr-len-ipv6"`
+	ConnectionsPerCidr int           `yaml:"max-connections"`
+	DurationString     string        `yaml:"duration"`
+	Duration           time.Duration `yaml:"duration-time"`
+	BanDurationString  string        `yaml:"ban-duration"`
+	BanDuration        time.Duration
+	BanMessage         string `yaml:"ban-message"`
+	Exempted           []string
+}
+
 type Config struct {
 	Network struct {
 		Name string
@@ -118,6 +133,7 @@ type Config struct {
 		Log                string
 		MOTD               string
 		ConnectionLimits   ConnectionLimitsConfig   `yaml:"connection-limits"`
+		ConnectionThrottle ConnectionThrottleConfig `yaml:"connection-throttling"`
 	}
 
 	Datastore struct {
@@ -309,6 +325,16 @@ func LoadConfig(filename string) (config *Config, err error) {
 	if config.Limits.NickLen < 1 || config.Limits.ChannelLen < 2 || config.Limits.AwayLen < 1 || config.Limits.KickLen < 1 || config.Limits.TopicLen < 1 {
 		return nil, errors.New("Limits aren't setup properly, check them and make them sane")
 	}
+	if config.Server.ConnectionThrottle.Enabled {
+		config.Server.ConnectionThrottle.Duration, err = time.ParseDuration(config.Server.ConnectionThrottle.DurationString)
+		if err != nil {
+			return nil, fmt.Errorf("Could not parse connection-throttle duration: %s", err.Error())
+		}
+		config.Server.ConnectionThrottle.BanDuration, err = time.ParseDuration(config.Server.ConnectionThrottle.BanDurationString)
+		if err != nil {
+			return nil, fmt.Errorf("Could not parse connection-throttle ban-duration: %s", err.Error())
+		}
+	}
 
 	return config, nil
 }

irc/connection_limits.go

@@ -15,6 +15,7 @@ var (
 
 // ConnectionLimits manages the automated client connection limits.
 type ConnectionLimits struct {
+	enabled  bool
 	ipv4Mask net.IPMask
 	ipv6Mask net.IPMask
 	// subnetLimit is the maximum number of clients per subnet
@@ -44,6 +45,10 @@ func (cl *ConnectionLimits) maskAddr(addr net.IP) net.IP {
 // AddClient adds a client to our population if possible. If we can't, throws an error instead.
 // 'force' is used to add already-existing clients (i.e. ones that are already on the network).
 func (cl *ConnectionLimits) AddClient(addr net.IP, force bool) error {
+	if !cl.enabled {
+		return nil
+	}
+
 	// check exempted lists
 	// we don't track populations for exempted addresses or nets - this is by design
 	if cl.exemptedIPs[addr.String()] {
@@ -70,6 +75,10 @@ func (cl *ConnectionLimits) AddClient(addr net.IP, force bool) error {
 
 // RemoveClient removes the given address from our population
 func (cl *ConnectionLimits) RemoveClient(addr net.IP) {
+	if !cl.enabled {
+		return
+	}
+
 	addrString := addr.String()
 	cl.population[addrString] = cl.population[addrString] - 1
 
@@ -82,6 +91,8 @@ func (cl *ConnectionLimits) RemoveClient(addr net.IP) {
 // NewConnectionLimits returns a new connection limit handler.
 func NewConnectionLimits(config ConnectionLimitsConfig) (*ConnectionLimits, error) {
 	var cl ConnectionLimits
+	cl.enabled = config.Enabled
+
 	cl.population = make(map[string]int)
 	cl.exemptedIPs = make(map[string]bool)
 

irc/connection_throttling.go

@@ -0,0 +1,142 @@
+// Copyright (c) 2016- Daniel Oaks <daniel@danieloaks.net>
+// released under the MIT license
+
+package irc
+
+import (
+	"fmt"
+	"net"
+	"time"
+
+	"github.com/DanielOaks/girc-go/ircmsg"
+)
+
+// ThrottleDetails holds the connection-throttling details for a subnet/IP.
+type ThrottleDetails struct {
+	Start       time.Time
+	ClientCount int
+}
+
+// ConnectionThrottle manages automated client connection throttling.
+type ConnectionThrottle struct {
+	enabled     bool
+	ipv4Mask    net.IPMask
+	ipv6Mask    net.IPMask
+	subnetLimit int
+	duration    time.Duration
+	population  map[string]ThrottleDetails
+
+	// used by the server to ban clients that go over this limit
+	BanDuration     time.Duration
+	BanMessage      string
+	BanMessageBytes []byte
+
+	// exemptedIPs holds IPs that are exempt from limits
+	exemptedIPs map[string]bool
+	// exemptedNets holds networks that are exempt from limits
+	exemptedNets []net.IPNet
+}
+
+// maskAddr masks the given IPv4/6 address with our cidr limit masks.
+func (ct *ConnectionThrottle) maskAddr(addr net.IP) net.IP {
+	if addr.To4() == nil {
+		// IPv6 addr
+		addr = addr.Mask(ct.ipv6Mask)
+	} else {
+		// IPv4 addr
+		addr = addr.Mask(ct.ipv4Mask)
+	}
+
+	return addr
+}
+
+// ResetFor removes any existing count for the given address.
+func (ct *ConnectionThrottle) ResetFor(addr net.IP) {
+	if !ct.enabled {
+		return
+	}
+
+	// remove
+	ct.maskAddr(addr)
+	addrString := addr.String()
+	delete(ct.population, addrString)
+}
+
+// AddClient introduces a new client connection if possible. If we can't, throws an error instead.
+func (ct *ConnectionThrottle) AddClient(addr net.IP) error {
+	if !ct.enabled {
+		return nil
+	}
+
+	// check exempted lists
+	if ct.exemptedIPs[addr.String()] {
+		return nil
+	}
+	for _, ex := range ct.exemptedNets {
+		if ex.Contains(addr) {
+			return nil
+		}
+	}
+
+	// check throttle
+	ct.maskAddr(addr)
+	addrString := addr.String()
+
+	details, exists := ct.population[addrString]
+	if !exists || details.Start.Add(ct.duration).Before(time.Now()) {
+		details = ThrottleDetails{
+			Start: time.Now(),
+		}
+	}
+
+	if details.ClientCount+1 > ct.subnetLimit {
+		return errTooManyClients
+	}
+
+	details.ClientCount++
+	ct.population[addrString] = details
+
+	return nil
+}
+
+// NewConnectionThrottle returns a new client connection throttler.
+func NewConnectionThrottle(config ConnectionThrottleConfig) (*ConnectionThrottle, error) {
+	var ct ConnectionThrottle
+	ct.enabled = config.Enabled
+
+	ct.population = make(map[string]ThrottleDetails)
+	ct.exemptedIPs = make(map[string]bool)
+
+	ct.ipv4Mask = net.CIDRMask(config.CidrLenIPv4, 32)
+	ct.ipv6Mask = net.CIDRMask(config.CidrLenIPv6, 128)
+	ct.subnetLimit = config.ConnectionsPerCidr
+
+	ct.duration = config.Duration
+
+	ct.BanDuration = config.BanDuration
+	ct.BanMessage = config.BanMessage
+	ircmsgOutput := ircmsg.MakeMessage(nil, "", "ERROR", ct.BanMessage)
+	msg, err := ircmsgOutput.Line()
+	if err != nil {
+		return nil, fmt.Errorf("Could not make error message: %s", err.Error())
+	}
+	ct.BanMessageBytes = []byte(msg)
+
+	// assemble exempted nets
+	for _, cidr := range config.Exempted {
+		ipaddr := net.ParseIP(cidr)
+		_, netaddr, err := net.ParseCIDR(cidr)
+
+		if ipaddr == nil && err != nil {
+			return nil, fmt.Errorf("Could not parse exempted IP/network [%s]", cidr)
+		}
+
+		if ipaddr != nil {
+			ct.exemptedIPs[ipaddr.String()] = true
+		} else {
+			ct.exemptedNets = append(ct.exemptedNets, *netaddr)
+		}
+	}
+
+	return &ct, nil
+}

irc/server.go

@@ -28,7 +28,7 @@ import (
 
 var (
 	// cached because this may be used lots
-	tooManyClientsMsg      = ircmsg.MakeMessage(nil, "", "ERROR", "Too many clients from your IP or network")
+	tooManyClientsMsg      = ircmsg.MakeMessage(nil, "", "ERROR", "Too many clients from your network")
 	tooManyClientsBytes, _ = tooManyClientsMsg.Line()
 
 	bannedFromServerMsg      = ircmsg.MakeMessage(nil, "", "ERROR", "You are banned from this server (%s)")
@@ -80,6 +80,8 @@ type Server struct {
 	clients                 *ClientLookupSet
 	commands                chan Command
 	configFilename          string
+	connectionThrottle      *ConnectionThrottle
+	connectionThrottleMutex sync.Mutex // used when affecting the connection limiter, to make sure rehashing doesn't make things go out-of-whack
 	connectionLimits        *ConnectionLimits
 	connectionLimitsMutex   sync.Mutex // used when affecting the connection limiter, to make sure rehashing doesn't make things go out-of-whack
 	ctime                   time.Time
@@ -157,6 +159,10 @@ func NewServer(configFilename string, config *Config) *Server {
 	if err != nil {
 		log.Fatal("Error loading connection limits:", err.Error())
 	}
+	connectionThrottle, err := NewConnectionThrottle(config.Server.ConnectionThrottle)
+	if err != nil {
+		log.Fatal("Error loading connection throttler:", err.Error())
+	}
 
 	server := &Server{
 		accounts:              make(map[string]*ClientAccount),
@@ -166,6 +172,7 @@ func NewServer(configFilename string, config *Config) *Server {
 		commands:              make(chan Command),
 		configFilename:        configFilename,
 		connectionLimits:      connectionLimits,
+		connectionThrottle:    connectionThrottle,
 		ctime:                 time.Now(),
 		currentOpers:          make(map[*Client]bool),
 		idle:                  make(chan *Client),
@@ -403,6 +410,27 @@ func (server *Server) Run() {
 					continue
 				}
 
+				// check connection throttle
+				server.connectionThrottleMutex.Lock()
+				err = server.connectionThrottle.AddClient(ipaddr)
+				server.connectionThrottleMutex.Unlock()
+				if err != nil {
+					// too many connections too quickly from client, tell them and close the connection
+					length := &IPRestrictTime{
+						Duration: server.connectionThrottle.BanDuration,
+						Expires:  time.Now().Add(server.connectionThrottle.BanDuration),
+					}
+					server.dlines.AddIP(ipaddr, length, server.connectionThrottle.BanMessage, "Exceeded automated connection throttle")
+
+					// reset ban on connectionThrottle
+					server.connectionThrottle.ResetFor(ipaddr)
+
+					// this might not show up properly on some clients, but our objective here is just to close it out before it has a load impact on us
+					conn.Conn.Write([]byte(server.connectionThrottle.BanMessageBytes))
+					conn.Conn.Close()
+					continue
+				}
+
 				go NewClient(server, conn.Conn, conn.IsTLS)
 				continue
 			}
@@ -1066,23 +1094,29 @@ func (server *Server) rehash() error {
 	config, err := LoadConfig(server.configFilename)
 
 	if err != nil {
-		return fmt.Errorf("Error rehashing config file: %s", err.Error())
+		return fmt.Errorf("Error rehashing config file config: %s", err.Error())
 	}
 
 	// confirm connectionLimits are fine
 	connectionLimits, err := NewConnectionLimits(config.Server.ConnectionLimits)
 	if err != nil {
-		return fmt.Errorf("Error rehashing config file: %s", err.Error())
+		return fmt.Errorf("Error rehashing config file connection-limits: %s", err.Error())
+	}
+
+	// confirm connectionThrottler is fine
+	connectionThrottle, err := NewConnectionThrottle(config.Server.ConnectionThrottle)
+	if err != nil {
+		return fmt.Errorf("Error rehashing config file connection-throttle: %s", err.Error())
 	}
 
 	// confirm operator stuff all exists and is fine
 	operclasses, err := config.OperatorClasses()
 	if err != nil {
-		return fmt.Errorf("Error rehashing config file: %s", err.Error())
+		return fmt.Errorf("Error rehashing config file operclasses: %s", err.Error())
 	}
 	opers, err := config.Operators(operclasses)
 	if err != nil {
-		return fmt.Errorf("Error rehashing config file: %s", err.Error())
+		return fmt.Errorf("Error rehashing config file opers: %s", err.Error())
 	}
 	for client := range server.currentOpers {
 		_, exists := opers[client.operName]
@@ -1094,6 +1128,8 @@ func (server *Server) rehash() error {
 	// apply new connectionlimits
 	server.connectionLimitsMutex.Lock()
 	server.connectionLimits = connectionLimits
+	server.connectionThrottleMutex.Lock()
+	server.connectionThrottle = connectionThrottle
 
 	server.clients.ByNickMutex.RLock()
 	for _, client := range server.clients.ByNick {

oragono.yaml

@@ -51,6 +51,9 @@ server:
 
     # maximum number of connections per subnet
     connection-limits:
+        # whether to throttle limits or not
+        enabled: true
+
         # how wide the cidr should be for IPv4 
         cidr-len-ipv4: 24
 
@@ -66,6 +69,34 @@ server:
             - "127.0.0.1/8"
             - "::1/128"
 
+    # automated connection throttling
+    connection-throttling:
+        # whether to throttle connections or not
+        enabled: true
+
+        # how wide the cidr should be for IPv4 
+        cidr-len-ipv4: 32
+
+        # how wide the cidr should be for IPv6
+        cidr-len-ipv6: 128
+
+        # how long to keep track of connections for
+        duration: 10m
+
+        # maximum number of connections, per subnet, within the given duration
+        max-connections: 12
+
+        # how long to ban offenders for, and the message to use
+        # after banning them, the number of connections is reset (which lets you use UNDLINE to unban people)
+        ban-duration: 10m
+        ban-message: You have attempted to connect too many times within a short duration. Wait a while, and you will be able to connect.
+
+        # IPs/networks which are exempted from connection limits
+        exempted:
+            - "127.0.0.1"
+            - "127.0.0.1/8"
+            - "::1/128"
+
 # account/channel registration
 registration:
     # account registration