Allow multiple backends

lib/http.go

@@ -3,16 +3,21 @@ package lib
 import (
 	"bytes"
 	"codeberg.org/meta/gzipped/v2"
+	"context"
 	"crypto/rand"
 	"encoding/base64"
 	"errors"
 	"fmt"
 	go_away "git.gammaspectra.live/git/go-away"
+	"git.gammaspectra.live/git/go-away/lib/network"
 	"git.gammaspectra.live/git/go-away/lib/policy"
 	"github.com/google/cel-go/common/types"
 	"html/template"
 	"maps"
+	"net"
 	"net/http"
+	"net/http/httputil"
+	"net/url"
 	"path/filepath"
 	"strings"
 	"time"
@@ -54,6 +59,34 @@ func init() {
 	}
 }
 
+func makeReverseProxy(target string) (http.Handler, error) {
+	u, err := url.Parse(target)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse target URL: %w", err)
+	}
+
+	transport := http.DefaultTransport.(*http.Transport).Clone()
+
+	// https://github.com/oauth2-proxy/oauth2-proxy/blob/4e2100a2879ef06aea1411790327019c1a09217c/pkg/upstream/http.go#L124
+	if u.Scheme == "unix" {
+		// clean path up so we don't use the socket path in proxied requests
+		addr := u.Path
+		u.Path = ""
+		// tell transport how to dial unix sockets
+		transport.DialContext = func(ctx context.Context, _, _ string) (net.Conn, error) {
+			dialer := net.Dialer{}
+			return dialer.DialContext(ctx, "unix", addr)
+		}
+		// tell transport how to handle the unix url scheme
+		transport.RegisterProtocol("unix", network.UnixRoundTripper{Transport: transport})
+	}
+
+	rp := httputil.NewSingleHostReverseProxy(u)
+	rp.Transport = transport
+
+	return rp, nil
+}
+
 func (state *State) challengePage(w http.ResponseWriter, status int, challenge string, params map[string]any) error {
 	input := make(map[string]any)
 	input["Random"] = cacheBust
@@ -104,8 +137,17 @@ func (state *State) errorPage(w http.ResponseWriter, status int, err error) erro
 
 func (state *State) handleRequest(w http.ResponseWriter, r *http.Request) {
 
+	host := r.Host
+
+	backend, ok := state.Backends[host]
+	if !ok {
+		http.Error(w, http.StatusText(http.StatusServiceUnavailable), http.StatusServiceUnavailable)
+		return
+	}
+
 	//TODO better matcher! combo ast?
 	env := map[string]any{
+		"host":          host,
 		"method":        r.Method,
 		"remoteAddress": state.GetRequestAddress(r),
 		"userAgent":     r.UserAgent(),
@@ -127,6 +169,10 @@ func (state *State) handleRequest(w http.ResponseWriter, r *http.Request) {
 	}
 
 	for _, rule := range state.Rules {
+		// skip rules that have host match
+		if rule.Host != nil && *rule.Host != host {
+			continue
+		}
 		if out, _, err := rule.Program.Eval(env); err != nil {
 			//TODO error
 			panic(err)
@@ -136,7 +182,7 @@ func (state *State) handleRequest(w http.ResponseWriter, r *http.Request) {
 				default:
 					panic(fmt.Errorf("unknown action %s", rule.Action))
 				case policy.RuleActionPASS:
-					state.Backend.ServeHTTP(w, r)
+					backend.ServeHTTP(w, r)
 					return
 				case policy.RuleActionCHALLENGE, policy.RuleActionCHECK:
 					expiry := time.Now().UTC().Add(DefaultValidity).Round(DefaultValidity)
@@ -154,7 +200,7 @@ func (state *State) handleRequest(w http.ResponseWriter, r *http.Request) {
 							}
 							// we passed the challenge!
 							//TODO log?
-							state.Backend.ServeHTTP(w, r)
+							backend.ServeHTTP(w, r)
 							return
 						}
 					}
@@ -174,7 +220,7 @@ func (state *State) handleRequest(w http.ResponseWriter, r *http.Request) {
 									goto nextRule
 								}
 								// we pass the challenge early!
-								state.Backend.ServeHTTP(w, r)
+								backend.ServeHTTP(w, r)
 								return
 							}
 						} else {
@@ -197,7 +243,7 @@ func (state *State) handleRequest(w http.ResponseWriter, r *http.Request) {
 	nextRule:
 	}
 
-	state.Backend.ServeHTTP(w, r)
+	backend.ServeHTTP(w, r)
 	return
 }
 

lib/policy/policy.go

@@ -43,4 +43,6 @@ type Policy struct {
 	Challenges map[string]Challenge `yaml:"challenges"`
 
 	Rules []Rule `yaml:"rules"`
+
+	Backends map[string]string `json:"backends"`
 }

lib/policy/rule.go

@@ -12,6 +12,7 @@ const (
 
 type Rule struct {
 	Name       string   `yaml:"name"`
+	Host       *string  `yaml:"host"`
 	Conditions []string `yaml:"conditions"`
 
 	Action string `yaml:"action"`

lib/state.go

@@ -40,7 +40,7 @@ type State struct {
 	Settings StateSettings
 	UrlPath  string
 	Mux      *http.ServeMux
-	Backend  http.Handler
+	Backends map[string]http.Handler
 
 	Networks map[string]cidranger.Ranger
 
@@ -61,6 +61,8 @@ type RuleState struct {
 	Name string
 	Hash string
 
+	Host *string
+
 	Program    cel.Program
 	Action     policy.RuleAction
 	Challenges []string
@@ -94,7 +96,6 @@ type ChallengeState struct {
 }
 
 type StateSettings struct {
-	Backend           http.Handler
 	PackagePath       string
 	ChallengeTemplate string
 }
@@ -108,7 +109,16 @@ func NewState(p policy.Policy, settings StateSettings) (state *State, err error)
 		},
 	}
 	state.UrlPath = "/.well-known/." + state.Settings.PackagePath
-	state.Backend = settings.Backend
+
+	state.Backends = make(map[string]http.Handler)
+
+	for k, v := range p.Backends {
+		backend, err := makeReverseProxy(v)
+		if err != nil {
+			return nil, fmt.Errorf("backend %s: failed to make reverse proxy: %w", k, err)
+		}
+		state.Backends[k] = backend
+	}
 
 	state.PublicKey, state.PrivateKey, err = ed25519.GenerateKey(rand.Reader)
 	if err != nil {
@@ -492,6 +502,7 @@ func NewState(p policy.Policy, settings StateSettings) (state *State, err error)
 	state.RulesEnv, err = cel.NewEnv(
 		cel.DefaultUTCTimeZone(true),
 		cel.Variable("remoteAddress", cel.BytesType),
+		cel.Variable("host", cel.StringType),
 		cel.Variable("method", cel.StringType),
 		cel.Variable("userAgent", cel.StringType),
 		cel.Variable("path", cel.StringType),
@@ -565,12 +576,18 @@ func NewState(p policy.Policy, settings StateSettings) (state *State, err error)
 	for _, rule := range p.Rules {
 		hasher := sha256.New()
 		hasher.Write([]byte(rule.Name))
+		hasher.Write([]byte{0})
+		if rule.Host != nil {
+			hasher.Write([]byte(*rule.Host))
+		}
+		hasher.Write([]byte{0})
 		hasher.Write(privateKeyFingerprint[:])
 		sum := hasher.Sum(nil)
 
 		r := RuleState{
 			Name:       rule.Name,
 			Hash:       hex.EncodeToString(sum[:8]),
+			Host:       rule.Host,
 			Action:     policy.RuleAction(strings.ToUpper(rule.Action)),
 			Challenges: rule.Challenges,
 		}