fix(lib): add the ability to set a custom slog Logger (#915)

* fix(lib): add the ability to set a custom slog Logger

Closes #864

* test(lib): amend s.check usage

Signed-off-by: Xe Iaso <me@xeiaso.net>

---------

Signed-off-by: Xe Iaso <me@xeiaso.net>
Signed-off-by: Xe Iaso <xe.iaso@techaro.lol>

docs/docs/CHANGELOG.md

@@ -13,6 +13,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 <!-- This changes the project to: -->
 
+- Downstream consumers can change the default [log/slog#Logger](https://pkg.go.dev/log/slog#Logger) instance that Anubis uses by setting `opts.Logger` to your slog instance of choice ([#864](https://github.com/TecharoHQ/anubis/issues/864)).
 - The [Thoth client](https://anubis.techaro.lol/docs/admin/thoth) is now public in the repo instead of being an internal package.
 - [Custom-AsyncHttpClient](https://github.com/AsyncHttpClient/async-http-client)'s default User-Agent has an increased weight by default ([#852](https://github.com/TecharoHQ/anubis/issues/852)).
 - The [`segments`](./admin/configuration/expressions.mdx#segments) function was added for splitting a path into its slash-separated segments.

internal/log.go

@@ -26,8 +26,8 @@ func InitSlog(level string) {
 	slog.SetDefault(slog.New(h))
 }
 
-func GetRequestLogger(r *http.Request) *slog.Logger {
+func GetRequestLogger(base *slog.Logger, r *http.Request) *slog.Logger {
-	return slog.With(
+	return base.With(
 		"host", r.Host,
 		"method", r.Method,
 		"path", r.URL.Path,

lib/anubis.go

@@ -75,6 +75,7 @@ type Server struct {
 	hs512Secret []byte
 	opts        Options
 	store       store.Interface
+	logger      *slog.Logger
 }
 
 func (s *Server) getTokenKeyfunc() jwt.Keyfunc {
@@ -150,7 +151,7 @@ func (s *Server) maybeReverseProxyOrPage(w http.ResponseWriter, r *http.Request)
 }
 
 func (s *Server) maybeReverseProxy(w http.ResponseWriter, r *http.Request, httpStatusOnly bool) {
-	lg := internal.GetRequestLogger(r)
+	lg := internal.GetRequestLogger(s.logger, r)
 
 	// Adjust cookie path if base prefix is not empty
 	cookiePath := "/"
@@ -158,7 +159,7 @@ func (s *Server) maybeReverseProxy(w http.ResponseWriter, r *http.Request, httpS
 		cookiePath = strings.TrimSuffix(anubis.BasePrefix, "/") + "/"
 	}
 
-	cr, rule, err := s.check(r)
+	cr, rule, err := s.check(r, lg)
 	if err != nil {
 		lg.Error("check failed", "err", err)
 		localizer := localization.GetLocalizer(r)
@@ -274,7 +275,7 @@ func (s *Server) checkRules(w http.ResponseWriter, r *http.Request, cr policy.Ch
 		return true
 	default:
 		s.ClearCookie(w, CookieOpts{Path: cookiePath, Host: r.Host})
-		slog.Error("CONFIG ERROR: unknown rule", "rule", cr.Rule)
+		lg.Error("CONFIG ERROR: unknown rule", "rule", cr.Rule)
 		s.respondWithError(w, r, fmt.Sprintf("%s \"maybeReverseProxy.Rules\"", localizer.T("internal_server_error")))
 		return true
 	}
@@ -310,7 +311,7 @@ func (s *Server) handleDNSBL(w http.ResponseWriter, r *http.Request, ip string,
 }
 
 func (s *Server) MakeChallenge(w http.ResponseWriter, r *http.Request) {
-	lg := internal.GetRequestLogger(r)
+	lg := internal.GetRequestLogger(s.logger, r)
 	localizer := localization.GetLocalizer(r)
 
 	redir := r.FormValue("redir")
@@ -329,7 +330,7 @@ func (s *Server) MakeChallenge(w http.ResponseWriter, r *http.Request) {
 	r.URL.Path = redir
 
 	encoder := json.NewEncoder(w)
-	cr, rule, err := s.check(r)
+	cr, rule, err := s.check(r, lg)
 	if err != nil {
 		lg.Error("check failed", "err", err)
 		w.WriteHeader(http.StatusInternalServerError)
@@ -381,7 +382,7 @@ func (s *Server) MakeChallenge(w http.ResponseWriter, r *http.Request) {
 }
 
 func (s *Server) PassChallenge(w http.ResponseWriter, r *http.Request) {
-	lg := internal.GetRequestLogger(r)
+	lg := internal.GetRequestLogger(s.logger, r)
 	localizer := localization.GetLocalizer(r)
 
 	redir := r.FormValue("redir")
@@ -428,7 +429,7 @@ func (s *Server) PassChallenge(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	cr, rule, err := s.check(r)
+	cr, rule, err := s.check(r, lg)
 	if err != nil {
 		lg.Error("check failed", "err", err)
 		s.respondWithError(w, r, fmt.Sprintf("%s \"passChallenge\"", localizer.T("internal_server_error")))
@@ -509,7 +510,7 @@ func cr(name string, rule config.Rule, weight int) policy.CheckResult {
 }
 
 // Check evaluates the list of rules, and returns the result
-func (s *Server) check(r *http.Request) (policy.CheckResult, *policy.Bot, error) {
+func (s *Server) check(r *http.Request, lg *slog.Logger) (policy.CheckResult, *policy.Bot, error) {
 	host := r.Header.Get("X-Real-Ip")
 	if host == "" {
 		return decaymap.Zilch[policy.CheckResult](), nil, fmt.Errorf("[misconfiguration] X-Real-Ip header is not set")
@@ -533,7 +534,7 @@ func (s *Server) check(r *http.Request) (policy.CheckResult, *policy.Bot, error)
 			case config.RuleDeny, config.RuleAllow, config.RuleBenchmark, config.RuleChallenge:
 				return cr("bot/"+b.Name, b.Action, weight), &b, nil
 			case config.RuleWeigh:
-				slog.Debug("adjusting weight", "name", b.Name, "delta", b.Weight.Adjust)
+				lg.Debug("adjusting weight", "name", b.Name, "delta", b.Weight.Adjust)
 				weight += b.Weight.Adjust
 			}
 		}
@@ -542,7 +543,7 @@ func (s *Server) check(r *http.Request) (policy.CheckResult, *policy.Bot, error)
 	for _, t := range s.policy.Thresholds {
 		result, _, err := t.Program.ContextEval(r.Context(), &policy.ThresholdRequest{Weight: weight})
 		if err != nil {
-			slog.Error("error when evaluating threshold expression", "expression", t.Expression.String(), "err", err)
+			lg.Error("error when evaluating threshold expression", "expression", t.Expression.String(), "err", err)
 			continue
 		}
 

lib/anubis_test.go

@@ -343,7 +343,7 @@ func TestCheckDefaultDifficultyMatchesPolicy(t *testing.T) {
 
 			req.Header.Add("X-Real-Ip", "127.0.0.1")
 
-			cr, bot, err := s.check(req)
+			cr, bot, err := s.check(req, s.logger)
 			if err != nil {
 				t.Fatal(err)
 			}
@@ -583,7 +583,7 @@ func TestCloudflareWorkersRule(t *testing.T) {
 				req.Header.Add("X-Real-Ip", "127.0.0.1")
 				req.Header.Add("Cf-Worker", "true")
 
-				cr, _, err := s.check(req)
+				cr, _, err := s.check(req, s.logger)
 				if err != nil {
 					t.Fatal(err)
 				}
@@ -601,7 +601,7 @@ func TestCloudflareWorkersRule(t *testing.T) {
 
 				req.Header.Add("X-Real-Ip", "127.0.0.1")
 
-				cr, _, err := s.check(req)
+				cr, _, err := s.check(req, s.logger)
 				if err != nil {
 					t.Fatal(err)
 				}

lib/config.go

@@ -43,6 +43,7 @@ type Options struct {
 	OpenGraph           config.OpenGraph
 	ServeRobotsTXT      bool
 	CookieSecure        bool
+	Logger              *slog.Logger
 }
 
 func LoadPoliciesOrDefault(ctx context.Context, fname string, defaultDifficulty int) (*policy.ParsedConfig, error) {
@@ -89,8 +90,12 @@ func LoadPoliciesOrDefault(ctx context.Context, fname string, defaultDifficulty
 }
 
 func New(opts Options) (*Server, error) {
+	if opts.Logger == nil {
+		opts.Logger = slog.With("subsystem", "anubis")
+	}
+
 	if opts.ED25519PrivateKey == nil && opts.HS512Secret == nil {
-		slog.Debug("opts.PrivateKey not set, generating a new one")
+		opts.Logger.Debug("opts.PrivateKey not set, generating a new one")
 		_, priv, err := ed25519.GenerateKey(rand.Reader)
 		if err != nil {
 			return nil, fmt.Errorf("lib: can't generate private key: %v", err)
@@ -108,6 +113,7 @@ func New(opts Options) (*Server, error) {
 		opts:        opts,
 		OGTags:      ogtags.NewOGTagCache(opts.Target, opts.Policy.OpenGraph, opts.Policy.Store),
 		store:       opts.Policy.Store,
+		logger:      opts.Logger,
 	}
 
 	mux := http.NewServeMux()

lib/http.go

@@ -120,7 +120,7 @@ func (s *Server) RenderIndex(w http.ResponseWriter, r *http.Request, cr policy.C
 		return
 	}
 
-	lg := internal.GetRequestLogger(r)
+	lg := internal.GetRequestLogger(s.logger, r)
 
 	if !strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") && randomChance(64) {
 		lg.Error("client was given a challenge but does not in fact support gzip compression")