caddyhttp: Add support for listener wrapper modules

Wrapping listeners is useful for composing custom behavior related
to accepting, closing, reading/writing connections (etc) below the
application layer; for example, the PROXY protocol.
This commit is contained in:
Matthew Holt 2020-03-15 21:26:17 -06:00
parent 0433f9d075
commit f596fd77bb
No known key found for this signature in database
GPG Key ID: 2A349DD577D586A5
3 changed files with 87 additions and 0 deletions

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@ -386,6 +386,19 @@ func JoinNetworkAddress(network, host, port string) string {
return a
}
// ListenerWrapper is a type that wraps a listener
// so it can modify the input listener's methods.
// Modules that implement this interface are found
// in the caddy.listeners namespace. Usually, to
// wrap a listener, you will define your own struct
// type that embeds the input listener, then
// implement your own methods that you want to wrap,
// calling the underlying listener's methods where
// appropriate.
type ListenerWrapper interface {
WrapListener(net.Listener) net.Listener
}
var (
listeners = make(map[string]*globalListener)
listenersMu sync.Mutex

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@ -40,6 +40,11 @@ func init() {
if err != nil {
caddy.Log().Fatal(err.Error())
}
err = caddy.RegisterModule(tlsPlaceholderWrapper{})
if err != nil {
caddy.Log().Fatal(err.Error())
}
}
// App is a robust, production-ready HTTP server.
@ -181,6 +186,7 @@ func (app *App) Provision(ctx caddy.Context) error {
srv.StrictSNIHost = &trueBool
}
// process each listener address
for i := range srv.Listen {
lnOut, err := repl.ReplaceOrErr(srv.Listen[i], true, true)
if err != nil {
@ -190,6 +196,37 @@ func (app *App) Provision(ctx caddy.Context) error {
srv.Listen[i] = lnOut
}
// set up each listener modifier
if srv.ListenerWrappersRaw != nil {
vals, err := ctx.LoadModule(srv, "ListenerWrappersRaw")
if err != nil {
return fmt.Errorf("loading listener wrapper modules: %v", err)
}
var hasTLSPlaceholder bool
for i, val := range vals.([]interface{}) {
if _, ok := val.(*tlsPlaceholderWrapper); ok {
if i == 0 {
// putting the tls placeholder wrapper first is nonsensical because
// that is the default, implicit setting: without it, all wrappers
// will go after the TLS listener anyway
return fmt.Errorf("it is unnecessary to specify the TLS listener wrapper in the first position because that is the default")
}
if hasTLSPlaceholder {
return fmt.Errorf("TLS listener wrapper can only be specified once")
}
hasTLSPlaceholder = true
}
srv.listenerWrappers = append(srv.listenerWrappers, val.(caddy.ListenerWrapper))
}
// if any wrappers were configured but the TLS placeholder wrapper is
// absent, prepend it so all defined wrappers come after the TLS
// handshake; this simplifies logic when starting the server, since we
// can simply assume the TLS placeholder will always be there
if !hasTLSPlaceholder && len(srv.listenerWrappers) > 0 {
srv.listenerWrappers = append([]caddy.ListenerWrapper{new(tlsPlaceholderWrapper)}, srv.listenerWrappers...)
}
}
// pre-compile the primary handler chain, and be sure to wrap it in our
// route handler so that important security checks are done, etc.
primaryRoute := emptyHandler
@ -265,12 +302,23 @@ func (app *App) Start() error {
return fmt.Errorf("%s: parsing listen address '%s': %v", srvName, lnAddr, err)
}
for portOffset := uint(0); portOffset < listenAddr.PortRangeSize(); portOffset++ {
// create the listener for this socket
hostport := listenAddr.JoinHostPort(portOffset)
ln, err := caddy.Listen(listenAddr.Network, hostport)
if err != nil {
return fmt.Errorf("%s: listening on %s: %v", listenAddr.Network, hostport, err)
}
// wrap listener before TLS (up to the TLS placeholder wrapper)
var lnWrapperIdx int
for i, lnWrapper := range srv.listenerWrappers {
if _, ok := lnWrapper.(*tlsPlaceholderWrapper); ok {
lnWrapperIdx = i + 1 // mark the next wrapper's spot
break
}
ln = lnWrapper.WrapListener(ln)
}
// enable TLS if there is a policy and if this is not the HTTP port
useTLS := len(srv.TLSConnPolicies) > 0 && int(listenAddr.StartPort+portOffset) != app.httpPort()
if useTLS {
@ -303,6 +351,11 @@ func (app *App) Start() error {
/////////
}
// finish wrapping listener where we left off before TLS
for i := lnWrapperIdx; i < len(srv.listenerWrappers); i++ {
ln = srv.listenerWrappers[i].WrapListener(ln)
}
app.logger.Debug("starting server loop",
zap.String("address", lnAddr),
zap.Bool("http3", srv.ExperimentalHTTP3),
@ -544,6 +597,19 @@ func StatusCodeMatches(actual, configured int) bool {
return false
}
// tlsPlaceholderWrapper is a no-op listener wrapper that marks
// where the TLS listener should be in a chain of listener wrappers.
type tlsPlaceholderWrapper struct{}
func (tlsPlaceholderWrapper) CaddyModule() caddy.ModuleInfo {
return caddy.ModuleInfo{
ID: "caddy.listeners.tls",
New: func() caddy.Module { return new(tlsPlaceholderWrapper) },
}
}
func (tlsPlaceholderWrapper) WrapListener(ln net.Listener) net.Listener { return ln }
const (
// DefaultHTTPPort is the default port for HTTP.
DefaultHTTPPort = 80
@ -557,4 +623,6 @@ var (
_ caddy.App = (*App)(nil)
_ caddy.Provisioner = (*App)(nil)
_ caddy.Validator = (*App)(nil)
_ caddy.ListenerWrapper = (*tlsPlaceholderWrapper)(nil)
)

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@ -16,6 +16,7 @@ package caddyhttp
import (
"context"
"encoding/json"
"fmt"
"net"
"net/http"
@ -38,6 +39,10 @@ type Server struct {
// that may include port ranges.
Listen []string `json:"listen,omitempty"`
// A list of listener wrapper modules, which can modify the behavior
// of the base listener. They are applied in the given order.
ListenerWrappersRaw []json.RawMessage `json:"listener_wrappers,omitempty" caddy:"namespace=caddy.listeners inline_key=wrapper"`
// How long to allow a read from a client's upload. Setting this
// to a short, non-zero value can mitigate slowloris attacks, but
// may also affect legitimately slow clients.
@ -106,6 +111,7 @@ type Server struct {
primaryHandlerChain Handler
errorHandlerChain Handler
listenerWrappers []caddy.ListenerWrapper
tlsApp *caddytls.TLS
logger *zap.Logger