feat(caddy): add Caddy support for Outline services

.gitignore

@@ -31,3 +31,6 @@
 # Go workspace
 go.work
 go.work.sum
+
+# Custom caddy binary
+/caddy/caddy

caddy/README.md

@@ -0,0 +1,25 @@
+# Caddy Module
+
+The Caddy module provides an app and handler for Caddy Server
+(https://caddyserver.com/) allowing it to turn any Caddy Server into an Outline
+Shadowsocks backend.
+
+## Prerequisites
+
+- [xcaddy](https://github.com/caddyserver/xcaddy)
+
+## Usage
+
+From this directory, build and run a custom binary with `xcaddy`:
+
+```sh
+xcaddy run --config config_example.json --watch
+```
+
+In a separate window, confirm you can fetch a page using this server:
+
+```sh
+go run github.com/Jigsaw-Code/outline-sdk/x/examples/fetch -transport "ss://chacha20-ietf-poly1305:Secret1@:9000" http://ipinfo.io
+```
+
+Prometheus metrics are available on http://localhost:9091/metrics.

caddy/app.go

@@ -0,0 +1,130 @@
+// Copyright 2024 The Outline Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package caddy provides an app and handler for Caddy Server (https://caddyserver.com/)
+// allowing it to turn any handler into one supporting the Vulcain protocol.
+
+package caddy
+
+import (
+	"errors"
+	"log/slog"
+
+	outline_prometheus "github.com/Jigsaw-Code/outline-ss-server/prometheus"
+	outline "github.com/Jigsaw-Code/outline-ss-server/service"
+	"github.com/caddyserver/caddy/v2"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+func init() {
+	caddy.RegisterModule(OutlineApp{})
+}
+
+const outlineModuleName = "outline"
+
+type ShadowsocksConfig struct {
+	ReplayHistory int `json:"replay_history,omitempty"`
+}
+
+type OutlineApp struct {
+	ShadowsocksConfig *ShadowsocksConfig `json:"shadowsocks,omitempty"`
+
+	ReplayCache outline.ReplayCache
+	logger      *slog.Logger
+	Metrics     outline.ServiceMetrics
+	buildInfo   *prometheus.GaugeVec
+}
+
+var (
+	_ caddy.App         = (*OutlineApp)(nil)
+	_ caddy.Provisioner = (*OutlineApp)(nil)
+)
+
+func (OutlineApp) CaddyModule() caddy.ModuleInfo {
+	return caddy.ModuleInfo{
+		ID:  outlineModuleName,
+		New: func() caddy.Module { return new(OutlineApp) },
+	}
+}
+
+// Provision sets up Outline.
+func (app *OutlineApp) Provision(ctx caddy.Context) error {
+	app.logger = ctx.Slogger()
+
+	app.logger.Info("provisioning app instance")
+
+	if app.ShadowsocksConfig != nil {
+		app.ReplayCache = outline.NewReplayCache(app.ShadowsocksConfig.ReplayHistory)
+	}
+
+	if err := app.defineMetrics(); err != nil {
+		app.logger.Error("failed to define Prometheus metrics", "err", err)
+	}
+	// TODO: Set version at build time.
+	app.buildInfo.WithLabelValues("dev").Set(1)
+	// TODO: Add replacement metrics for `shadowsocks_keys` and `shadowsocks_ports`.
+
+	return nil
+}
+
+func (app *OutlineApp) defineMetrics() error {
+	r := prometheus.WrapRegistererWithPrefix("outline_", prometheus.DefaultRegisterer)
+
+	var err error
+	buildInfo := prometheus.NewGaugeVec(prometheus.GaugeOpts{
+		Name: "build_info",
+		Help: "Information on the outline-ss-server build",
+	}, []string{"version"})
+	app.buildInfo, err = registerCollector(r, buildInfo)
+	if err != nil {
+		return err
+	}
+
+	// TODO: Allow the configuration of ip2info.
+	metrics, err := outline_prometheus.NewServiceMetrics(nil)
+	if err != nil {
+		return err
+	}
+	app.Metrics, err = registerCollector(r, metrics)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func registerCollector[T prometheus.Collector](registerer prometheus.Registerer, coll T) (T, error) {
+	if err := registerer.Register(coll); err != nil {
+		are := &prometheus.AlreadyRegisteredError{}
+		if !errors.As(err, are) {
+			// This collector has been registered before. This is expected during a config reload.
+			coll = are.ExistingCollector.(T)
+		} else {
+			// Something else went wrong.
+			return coll, err
+		}
+	}
+	return coll, nil
+}
+
+// Start starts the App.
+func (app *OutlineApp) Start() error {
+	app.logger.Debug("started app instance")
+	return nil
+}
+
+// Stop stops the App.
+func (app *OutlineApp) Stop() error {
+	app.logger.Debug("stopped app instance")
+	return nil
+}

caddy/config_example.json

@@ -0,0 +1,97 @@
+{
+    "admin": {
+        "disabled": true
+    },
+    "logging": {
+      "logs": {
+        "default": {"level":"DEBUG", "encoder": {"format":"console"}}
+      }
+    },
+    "apps": {
+        "http": {
+            "servers": {
+				"": {
+					"listen": [
+						":9091"
+					],
+					"routes": [
+						{
+							"match": [
+								{
+									"path": [
+										"/metrics"
+									]
+								}
+							],
+							"handle": [
+								{
+									"disable_openmetrics": true,
+									"handler": "metrics"
+								}
+							]
+						}
+					]
+				}
+            }
+        },
+        "layer4": {
+            "servers": {
+
+                "1": {
+                    "listen": [
+                        "tcp/[::]:9000",
+                        "udp/[::]:9000"
+                    ],
+                    "routes": [
+                        {
+                            "handle": [
+                                {
+                                    "handler": "shadowsocks",
+                                    "keys": [
+                                        {
+                                            "id": "user-0",
+                                            "cipher": "chacha20-ietf-poly1305",
+                                            "secret": "Secret0"
+                                        },
+                                        {
+                                            "id": "user-1",
+                                            "cipher": "chacha20-ietf-poly1305",
+                                            "secret": "Secret1"
+                                        }
+                                    ]
+                                }
+                            ]
+                        }
+                    ]
+                },
+                "2": {
+                    "listen": [
+                        "tcp/[::]:9001",
+                        "udp/[::]:9001"
+                    ],
+                    "routes": [
+                        {
+                            "handle": [
+                                {
+                                    "handler": "shadowsocks",
+                                    "keys": [
+                                        {
+                                            "id": "user-2",
+                                            "cipher": "chacha20-ietf-poly1305",
+                                            "secret": "Secret2"
+                                        }
+                                    ]
+                                }
+                            ]
+                        }
+                    ]
+                }
+            }
+        },
+        "outline": {
+            "shadowsocks": {
+                "replay_history": 10000
+            }
+        }
+    }
+}

caddy/go.mod

@@ -0,0 +1,123 @@
+module github.com/Jigsaw-Code/outline-ss-server/caddy
+
+go 1.23
+
+require (
+	github.com/Jigsaw-Code/outline-sdk v0.0.16
+	github.com/Jigsaw-Code/outline-ss-server v1.6.0
+	github.com/caddyserver/caddy/v2 v2.8.4
+	github.com/mholt/caddy-l4 v0.0.0-20240812213304-afa78d72257b
+	github.com/prometheus/client_golang v1.20.0
+	go.uber.org/zap v1.27.0
+)
+
+require (
+	filippo.io/edwards25519 v1.1.0 // indirect
+	github.com/AndreasBriese/bbloom v0.0.0-20190825152654-46b345b51c96 // indirect
+	github.com/Masterminds/goutils v1.1.1 // indirect
+	github.com/Masterminds/semver/v3 v3.2.1 // indirect
+	github.com/Masterminds/sprig/v3 v3.2.3 // indirect
+	github.com/Microsoft/go-winio v0.6.1 // indirect
+	github.com/antlr4-go/antlr/v4 v4.13.0 // indirect
+	github.com/aryann/difflib v0.0.0-20210328193216-ff5ff6dc229b // indirect
+	github.com/beorn7/perks v1.0.1 // indirect
+	github.com/caddyserver/certmagic v0.21.3 // indirect
+	github.com/caddyserver/zerossl v0.1.3 // indirect
+	github.com/cespare/xxhash v1.1.0 // indirect
+	github.com/cespare/xxhash/v2 v2.3.0 // indirect
+	github.com/chzyer/readline v1.5.1 // indirect
+	github.com/cpuguy83/go-md2man/v2 v2.0.3 // indirect
+	github.com/dgraph-io/badger v1.6.2 // indirect
+	github.com/dgraph-io/badger/v2 v2.2007.4 // indirect
+	github.com/dgraph-io/ristretto v0.1.1 // indirect
+	github.com/dgryski/go-farm v0.0.0-20200201041132-a6ae2369ad13 // indirect
+	github.com/dustin/go-humanize v1.0.1 // indirect
+	github.com/go-jose/go-jose/v3 v3.0.3 // indirect
+	github.com/go-kit/kit v0.13.0 // indirect
+	github.com/go-kit/log v0.2.1 // indirect
+	github.com/go-logfmt/logfmt v0.6.0 // indirect
+	github.com/go-sql-driver/mysql v1.7.1 // indirect
+	github.com/go-task/slim-sprig v0.0.0-20230315185526-52ccab3ef572 // indirect
+	github.com/golang/glog v1.2.0 // indirect
+	github.com/golang/protobuf v1.5.4 // indirect
+	github.com/golang/snappy v0.0.4 // indirect
+	github.com/google/cel-go v0.20.1 // indirect
+	github.com/google/pprof v0.0.0-20240207164012-fb44976bdcd5 // indirect
+	github.com/google/uuid v1.6.0 // indirect
+	github.com/huandu/xstrings v1.4.0 // indirect
+	github.com/imdario/mergo v0.3.16 // indirect
+	github.com/inconshreveable/mousetrap v1.1.0 // indirect
+	github.com/jackc/chunkreader/v2 v2.0.1 // indirect
+	github.com/jackc/pgconn v1.14.3 // indirect
+	github.com/jackc/pgio v1.0.0 // indirect
+	github.com/jackc/pgpassfile v1.0.0 // indirect
+	github.com/jackc/pgproto3/v2 v2.3.3 // indirect
+	github.com/jackc/pgservicefile v0.0.0-20221227161230-091c0ba34f0a // indirect
+	github.com/jackc/pgtype v1.14.0 // indirect
+	github.com/jackc/pgx/v4 v4.18.3 // indirect
+	github.com/klauspost/compress v1.17.9 // indirect
+	github.com/klauspost/cpuid/v2 v2.2.7 // indirect
+	github.com/libdns/libdns v0.2.2 // indirect
+	github.com/manifoldco/promptui v0.9.0 // indirect
+	github.com/mattn/go-colorable v0.1.13 // indirect
+	github.com/mattn/go-isatty v0.0.20 // indirect
+	github.com/mgutz/ansi v0.0.0-20200706080929-d51e80ef957d // indirect
+	github.com/mholt/acmez/v2 v2.0.1 // indirect
+	github.com/miekg/dns v1.1.59 // indirect
+	github.com/mitchellh/copystructure v1.2.0 // indirect
+	github.com/mitchellh/go-ps v1.0.0 // indirect
+	github.com/mitchellh/reflectwalk v1.0.2 // indirect
+	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
+	github.com/onsi/ginkgo/v2 v2.15.0 // indirect
+	github.com/oschwald/geoip2-golang v1.8.0 // indirect
+	github.com/oschwald/maxminddb-golang v1.10.0 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
+	github.com/prometheus/client_model v0.6.1 // indirect
+	github.com/prometheus/common v0.55.0 // indirect
+	github.com/prometheus/procfs v0.15.1 // indirect
+	github.com/quic-go/qpack v0.4.0 // indirect
+	github.com/quic-go/quic-go v0.44.0 // indirect
+	github.com/rs/xid v1.5.0 // indirect
+	github.com/russross/blackfriday/v2 v2.1.0 // indirect
+	github.com/shadowsocks/go-shadowsocks2 v0.1.5 // indirect
+	github.com/shopspring/decimal v1.3.1 // indirect
+	github.com/shurcooL/sanitized_anchor_name v1.0.0 // indirect
+	github.com/slackhq/nebula v1.7.2 // indirect
+	github.com/smallstep/certificates v0.26.1 // indirect
+	github.com/smallstep/nosql v0.6.1 // indirect
+	github.com/smallstep/pkcs7 v0.0.0-20231024181729-3b98ecc1ca81 // indirect
+	github.com/smallstep/scep v0.0.0-20231024192529-aee96d7ad34d // indirect
+	github.com/smallstep/truststore v0.13.0 // indirect
+	github.com/spf13/cast v1.5.1 // indirect
+	github.com/spf13/cobra v1.8.0 // indirect
+	github.com/spf13/pflag v1.0.5 // indirect
+	github.com/stoewer/go-strcase v1.3.0 // indirect
+	github.com/tailscale/tscert v0.0.0-20240517230440-bbccfbf48933 // indirect
+	github.com/urfave/cli v1.22.14 // indirect
+	github.com/zeebo/blake3 v0.2.3 // indirect
+	go.etcd.io/bbolt v1.3.9 // indirect
+	go.step.sm/cli-utils v0.9.0 // indirect
+	go.step.sm/crypto v0.45.0 // indirect
+	go.step.sm/linkedca v0.20.1 // indirect
+	go.uber.org/automaxprocs v1.5.3 // indirect
+	go.uber.org/mock v0.4.0 // indirect
+	go.uber.org/multierr v1.11.0 // indirect
+	go.uber.org/zap/exp v0.2.0 // indirect
+	golang.org/x/crypto v0.24.0 // indirect
+	golang.org/x/crypto/x509roots/fallback v0.0.0-20240507223354-67b13616a595 // indirect
+	golang.org/x/exp v0.0.0-20240506185415-9bf2ced13842 // indirect
+	golang.org/x/mod v0.17.0 // indirect
+	golang.org/x/net v0.26.0 // indirect
+	golang.org/x/sync v0.7.0 // indirect
+	golang.org/x/sys v0.22.0 // indirect
+	golang.org/x/term v0.21.0 // indirect
+	golang.org/x/text v0.16.0 // indirect
+	golang.org/x/time v0.5.0 // indirect
+	golang.org/x/tools v0.21.1-0.20240508182429-e35e4ccd0d2d // indirect
+	google.golang.org/genproto/googleapis/api v0.0.0-20240506185236-b8a5c65736ae // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20240429193739-8cf5692501f6 // indirect
+	google.golang.org/grpc v1.63.2 // indirect
+	google.golang.org/protobuf v1.34.2 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+	howett.net/plist v1.0.0 // indirect
+)