caddyhttp: Add `MatchWithError` to replace SetVar hack (#6596)

* caddyhttp: Add `MatchWithError` to replace SetVar hack

* Error in IP matchers on TLS handshake not complete

* Use MatchWithError everywhere possible

* Move implementations to MatchWithError versions

* Looser interface checking to allow fallback

* CEL factories can return RequestMatcherWithError

* Clarifying comment since it's subtle that an err is returned

* Return 425 Too Early status in IP matchers

* Keep AnyMatch signature the same for now

* Apparently Deprecated can't be all-uppercase to get IDE linting

* Linter

13 files changed, 519 insertions, 190 deletions

diff --git a/modules/caddyhttp/caddyhttp.go b/modules/caddyhttp/caddyhttp.go
index e1e71f4a0..aacafc92e 100644
--- a/modules/caddyhttp/caddyhttp.go
+++ b/modules/caddyhttp/caddyhttp.go
@@ -36,10 +36,26 @@ func init() {
 // RequestMatcher is a type that can match to a request.
 // A route matcher MUST NOT modify the request, with the
 // only exception being its context.
+//
+// Deprecated: Matchers should now implement RequestMatcherWithError.
+// You may remove any interface guards for RequestMatcher
+// but keep your Match() methods for backwards compatibility.
 type RequestMatcher interface {
 	Match(*http.Request) bool
 }
 
+// RequestMatcherWithError is like RequestMatcher but can return an error.
+// An error during matching will abort the request middleware chain and
+// invoke the error middleware chain.
+//
+// This will eventually replace RequestMatcher. Matcher modules
+// should implement both interfaces, and once all modules have
+// been updated to use RequestMatcherWithError, the RequestMatcher
+// interface may eventually be dropped.
+type RequestMatcherWithError interface {
+	MatchWithError(*http.Request) (bool, error)
+}
+
 // Handler is like http.Handler except ServeHTTP may return an error.
 //
 // If any handler encounters an error, it should be returned for proper
diff --git a/modules/caddyhttp/celmatcher.go b/modules/caddyhttp/celmatcher.go
index 2a03ebba7..3d118ea79 100644
--- a/modules/caddyhttp/celmatcher.go
+++ b/modules/caddyhttp/celmatcher.go
@@ -202,17 +202,25 @@ func (m *MatchExpression) Provision(ctx caddy.Context) error {
 
 // Match returns true if r matches m.
 func (m MatchExpression) Match(r *http.Request) bool {
+	match, err := m.MatchWithError(r)
+	if err != nil {
+		SetVar(r.Context(), MatcherErrorVarKey, err)
+	}
+	return match
+}
+
+// MatchWithError returns true if r matches m.
+func (m MatchExpression) MatchWithError(r *http.Request) (bool, error) {
 	celReq := celHTTPRequest{r}
 	out, _, err := m.prg.Eval(celReq)
 	if err != nil {
 		m.log.Error("evaluating expression", zap.Error(err))
-		SetVar(r.Context(), MatcherErrorVarKey, err)
-		return false
+		return false, err
 	}
 	if outBool, ok := out.Value().(bool); ok {
-		return outBool
+		return outBool, nil
 	}
-	return false
+	return false, nil
 }
 
 // UnmarshalCaddyfile implements caddyfile.Unmarshaler.
@@ -380,7 +388,7 @@ type CELLibraryProducer interface {
 // limited set of function signatures. For strong type validation you may need
 // to provide a custom macro which does a more detailed analysis of the CEL
 // literal provided to the macro as an argument.
-func CELMatcherImpl(macroName, funcName string, matcherDataTypes []*cel.Type, fac CELMatcherFactory) (cel.Library, error) {
+func CELMatcherImpl(macroName, funcName string, matcherDataTypes []*cel.Type, fac any) (cel.Library, error) {
 	requestType := cel.ObjectType("http.Request")
 	var macro parser.Macro
 	switch len(matcherDataTypes) {
@@ -424,7 +432,11 @@ func CELMatcherImpl(macroName, funcName string, matcherDataTypes []*cel.Type, fa
 }
 
 // CELMatcherFactory converts a constant CEL value into a RequestMatcher.
-type CELMatcherFactory func(data ref.Val) (RequestMatcher, error)
+// Deprecated: Use CELMatcherWithErrorFactory instead.
+type CELMatcherFactory = func(data ref.Val) (RequestMatcher, error)
+
+// CELMatcherWithErrorFactory converts a constant CEL value into a RequestMatcherWithError.
+type CELMatcherWithErrorFactory = func(data ref.Val) (RequestMatcherWithError, error)
 
 // matcherCELLibrary is a simplistic configurable cel.Library implementation.
 type matcherCELLibrary struct {
@@ -452,7 +464,7 @@ func (lib *matcherCELLibrary) ProgramOptions() []cel.ProgramOption {
 // that takes a single argument, and optimizes the implementation to precompile
 // the matcher and return a function that references the precompiled and
 // provisioned matcher.
-func CELMatcherDecorator(funcName string, fac CELMatcherFactory) interpreter.InterpretableDecorator {
+func CELMatcherDecorator(funcName string, fac any) interpreter.InterpretableDecorator {
 	return func(i interpreter.Interpretable) (interpreter.Interpretable, error) {
 		call, ok := i.(interpreter.InterpretableCall)
 		if !ok {
@@ -481,35 +493,92 @@ func CELMatcherDecorator(funcName string, fac CELMatcherFactory) interpreter.Int
 			// and matcher provisioning should be handled at dynamically.
 			return i, nil
 		}
-		matcher, err := fac(matcherData.Value())
-		if err != nil {
-			return nil, err
+
+		if factory, ok := fac.(CELMatcherWithErrorFactory); ok {
+			matcher, err := factory(matcherData.Value())
+			if err != nil {
+				return nil, err
+			}
+			return interpreter.NewCall(
+				i.ID(), funcName, funcName+"_opt",
+				[]interpreter.Interpretable{reqAttr},
+				func(args ...ref.Val) ref.Val {
+					// The request value, guaranteed to be of type celHTTPRequest
+					celReq := args[0]
+					// If needed this call could be changed to convert the value
+					// to a *http.Request using CEL's ConvertToNative method.
+					httpReq := celReq.Value().(celHTTPRequest)
+					match, err := matcher.MatchWithError(httpReq.Request)
+					if err != nil {
+						return types.WrapErr(err)
+					}
+					return types.Bool(match)
+				},
+			), nil
 		}
-		return interpreter.NewCall(
-			i.ID(), funcName, funcName+"_opt",
-			[]interpreter.Interpretable{reqAttr},
-			func(args ...ref.Val) ref.Val {
-				// The request value, guaranteed to be of type celHTTPRequest
-				celReq := args[0]
-				// If needed this call could be changed to convert the value
-				// to a *http.Request using CEL's ConvertToNative method.
-				httpReq := celReq.Value().(celHTTPRequest)
-				return types.Bool(matcher.Match(httpReq.Request))
-			},
-		), nil
+
+		if factory, ok := fac.(CELMatcherFactory); ok {
+			matcher, err := factory(matcherData.Value())
+			if err != nil {
+				return nil, err
+			}
+			return interpreter.NewCall(
+				i.ID(), funcName, funcName+"_opt",
+				[]interpreter.Interpretable{reqAttr},
+				func(args ...ref.Val) ref.Val {
+					// The request value, guaranteed to be of type celHTTPRequest
+					celReq := args[0]
+					// If needed this call could be changed to convert the value
+					// to a *http.Request using CEL's ConvertToNative method.
+					httpReq := celReq.Value().(celHTTPRequest)
+					if m, ok := matcher.(RequestMatcherWithError); ok {
+						match, err := m.MatchWithError(httpReq.Request)
+						if err != nil {
+							return types.WrapErr(err)
+						}
+						return types.Bool(match)
+					}
+					return types.Bool(matcher.Match(httpReq.Request))
+				},
+			), nil
+		}
+
+		return nil, fmt.Errorf("invalid matcher factory, must be CELMatcherFactory or CELMatcherWithErrorFactory: %T", fac)
 	}
 }
 
 // CELMatcherRuntimeFunction creates a function binding for when the input to the matcher
 // is dynamically resolved rather than a set of static constant values.
-func CELMatcherRuntimeFunction(funcName string, fac CELMatcherFactory) functions.BinaryOp {
+func CELMatcherRuntimeFunction(funcName string, fac any) functions.BinaryOp {
 	return func(celReq, matcherData ref.Val) ref.Val {
-		matcher, err := fac(matcherData)
-		if err != nil {
-			return types.WrapErr(err)
+		if factory, ok := fac.(CELMatcherWithErrorFactory); ok {
+			matcher, err := factory(matcherData)
+			if err != nil {
+				return types.WrapErr(err)
+			}
+			httpReq := celReq.Value().(celHTTPRequest)
+			match, err := matcher.MatchWithError(httpReq.Request)
+			if err != nil {
+				return types.WrapErr(err)
+			}
+			return types.Bool(match)
+		}
+		if factory, ok := fac.(CELMatcherFactory); ok {
+			matcher, err := factory(matcherData)
+			if err != nil {
+				return types.WrapErr(err)
+			}
+			httpReq := celReq.Value().(celHTTPRequest)
+			if m, ok := matcher.(RequestMatcherWithError); ok {
+				match, err := m.MatchWithError(httpReq.Request)
+				if err != nil {
+					return types.WrapErr(err)
+				}
+				return types.Bool(match)
+			}
+			return types.Bool(matcher.Match(httpReq.Request))
 		}
-		httpReq := celReq.Value().(celHTTPRequest)
-		return types.Bool(matcher.Match(httpReq.Request))
+		return types.NewErr("CELMatcherRuntimeFunction invalid matcher factory: %T", fac)
 	}
 }
 
@@ -733,9 +802,9 @@ const MatcherNameCtxKey = "matcher_name"
 
 // Interface guards
 var (
-	_ caddy.Provisioner     = (*MatchExpression)(nil)
-	_ RequestMatcher        = (*MatchExpression)(nil)
-	_ caddyfile.Unmarshaler = (*MatchExpression)(nil)
-	_ json.Marshaler        = (*MatchExpression)(nil)
-	_ json.Unmarshaler      = (*MatchExpression)(nil)
+	_ caddy.Provisioner       = (*MatchExpression)(nil)
+	_ RequestMatcherWithError = (*MatchExpression)(nil)
+	_ caddyfile.Unmarshaler   = (*MatchExpression)(nil)
+	_ json.Marshaler          = (*MatchExpression)(nil)
+	_ json.Unmarshaler        = (*MatchExpression)(nil)
 )
diff --git a/modules/caddyhttp/celmatcher_test.go b/modules/caddyhttp/celmatcher_test.go
index 26491b7ca..a7e91529c 100644
--- a/modules/caddyhttp/celmatcher_test.go
+++ b/modules/caddyhttp/celmatcher_test.go
@@ -489,7 +489,11 @@ func TestMatchExpressionMatch(t *testing.T) {
 				}
 			}
 
-			if tc.expression.Match(req) != tc.wantResult {
+			matches, err := tc.expression.MatchWithError(req)
+			if err != nil {
+				t.Errorf("MatchExpression.Match() error = %v", err)
+			}
+			if matches != tc.wantResult {
 				t.Errorf("MatchExpression.Match() expected to return '%t', for expression : '%s'", tc.wantResult, tc.expression.Expr)
 			}
 		})
@@ -532,7 +536,7 @@ func BenchmarkMatchExpressionMatch(b *testing.B) {
 			}
 			b.ResetTimer()
 			for i := 0; i < b.N; i++ {
-				tc.expression.Match(req)
+				tc.expression.MatchWithError(req)
 			}
 		})
 	}
diff --git a/modules/caddyhttp/fileserver/matcher.go b/modules/caddyhttp/fileserver/matcher.go
index 28f7b89be..c42907491 100644
--- a/modules/caddyhttp/fileserver/matcher.go
+++ b/modules/caddyhttp/fileserver/matcher.go
@@ -173,7 +173,7 @@ func (m *MatchFile) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 func (MatchFile) CELLibrary(ctx caddy.Context) (cel.Library, error) {
 	requestType := cel.ObjectType("http.Request")
 
-	matcherFactory := func(data ref.Val) (caddyhttp.RequestMatcher, error) {
+	matcherFactory := func(data ref.Val) (caddyhttp.RequestMatcherWithError, error) {
 		values, err := caddyhttp.CELValueToMapStrList(data)
 		if err != nil {
 			return nil, err
@@ -313,12 +313,22 @@ func (m MatchFile) Validate() error {
 //   - http.matchers.file.type: file or directory
 //   - http.matchers.file.remainder: Portion remaining after splitting file path (if configured)
 func (m MatchFile) Match(r *http.Request) bool {
+	match, err := m.selectFile(r)
+	if err != nil {
+		// nolint:staticcheck
+		caddyhttp.SetVar(r.Context(), caddyhttp.MatcherErrorVarKey, err)
+	}
+	return match
+}
+
+// MatchWithError returns true if r matches m.
+func (m MatchFile) MatchWithError(r *http.Request) (bool, error) {
 	return m.selectFile(r)
 }
 
 // selectFile chooses a file according to m.TryPolicy by appending
 // the paths in m.TryFiles to m.Root, with placeholder replacements.
-func (m MatchFile) selectFile(r *http.Request) (matched bool) {
+func (m MatchFile) selectFile(r *http.Request) (bool, error) {
 	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 
 	root := filepath.Clean(repl.ReplaceAll(m.Root, "."))
@@ -330,7 +340,7 @@ func (m MatchFile) selectFile(r *http.Request) (matched bool) {
 		if c := m.logger.Check(zapcore.ErrorLevel, "use of unregistered filesystem"); c != nil {
 			c.Write(zap.String("fs", fsName))
 		}
-		return false
+		return false, nil
 	}
 	type matchCandidate struct {
 		fullpath, relative, splitRemainder string
@@ -421,15 +431,18 @@ func (m MatchFile) selectFile(r *http.Request) (matched bool) {
 	switch m.TryPolicy {
 	case "", tryPolicyFirstExist:
 		for _, pattern := range m.TryFiles {
+			// If the pattern is a status code, emit an error,
+			// which short-circuits the middleware pipeline and
+			// writes an HTTP error response.
 			if err := parseErrorCode(pattern); err != nil {
-				caddyhttp.SetVar(r.Context(), caddyhttp.MatcherErrorVarKey, err)
-				return
+				return false, err
 			}
+
 			candidates := makeCandidates(pattern)
 			for _, c := range candidates {
 				if info, exists := m.strictFileExists(fileSystem, c.fullpath); exists {
 					setPlaceholders(c, info)
-					return true
+					return true, nil
 				}
 			}
 		}
@@ -450,10 +463,10 @@ func (m MatchFile) selectFile(r *http.Request) (matched bool) {
 			}
 		}
 		if largestInfo == nil {
-			return false
+			return false, nil
 		}
 		setPlaceholders(largest, largestInfo)
-		return true
+		return true, nil
 
 	case tryPolicySmallestSize:
 		var smallestSize int64
@@ -471,10 +484,10 @@ func (m MatchFile) selectFile(r *http.Request) (matched bool) {
 			}
 		}
 		if smallestInfo == nil {
-			return false
+			return false, nil
 		}
 		setPlaceholders(smallest, smallestInfo)
-		return true
+		return true, nil
 
 	case tryPolicyMostRecentlyMod:
 		var recent matchCandidate
@@ -491,13 +504,13 @@ func (m MatchFile) selectFile(r *http.Request) (matched bool) {
 			}
 		}
 		if recentInfo == nil {
-			return false
+			return false, nil
 		}
 		setPlaceholders(recent, recentInfo)
-		return true
+		return true, nil
 	}
 
-	return
+	return false, nil
 }
 
 // parseErrorCode checks if the input is a status
@@ -703,7 +716,7 @@ const (
 
 // Interface guards
 var (
-	_ caddy.Validator              = (*MatchFile)(nil)
-	_ caddyhttp.RequestMatcher     = (*MatchFile)(nil)
-	_ caddyhttp.CELLibraryProducer = (*MatchFile)(nil)
+	_ caddy.Validator                   = (*MatchFile)(nil)
+	_ caddyhttp.RequestMatcherWithError = (*MatchFile)(nil)
+	_ caddyhttp.CELLibraryProducer      = (*MatchFile)(nil)
 )
diff --git a/modules/caddyhttp/fileserver/matcher_test.go b/modules/caddyhttp/fileserver/matcher_test.go
index 95eeb8216..b6697b9d8 100644
--- a/modules/caddyhttp/fileserver/matcher_test.go
+++ b/modules/caddyhttp/fileserver/matcher_test.go
@@ -130,7 +130,10 @@ func TestFileMatcher(t *testing.T) {
 		req := &http.Request{URL: u}
 		repl := caddyhttp.NewTestReplacer(req)
 
-		result := m.Match(req)
+		result, err := m.MatchWithError(req)
+		if err != nil {
+			t.Errorf("Test %d: unexpected error: %v", i, err)
+		}
 		if result != tc.matched {
 			t.Errorf("Test %d: expected match=%t, got %t", i, tc.matched, result)
 		}
@@ -240,7 +243,10 @@ func TestPHPFileMatcher(t *testing.T) {
 		req := &http.Request{URL: u}
 		repl := caddyhttp.NewTestReplacer(req)
 
-		result := m.Match(req)
+		result, err := m.MatchWithError(req)
+		if err != nil {
+			t.Errorf("Test %d: unexpected error: %v", i, err)
+		}
 		if result != tc.matched {
 			t.Errorf("Test %d: expected match=%t, got %t", i, tc.matched, result)
 		}
@@ -389,7 +395,12 @@ func TestMatchExpressionMatch(t *testing.T) {
 			ctx := context.WithValue(req.Context(), caddy.ReplacerCtxKey, repl)
 			req = req.WithContext(ctx)
 
-			if tc.expression.Match(req) != tc.wantResult {
+			matches, err := tc.expression.MatchWithError(req)
+			if err != nil {
+				t.Errorf("MatchExpression.Match() error = %v", err)
+				return
+			}
+			if matches != tc.wantResult {
 				t.Errorf("MatchExpression.Match() expected to return '%t', for expression : '%s'", tc.wantResult, tc.expression.Expr)
 			}
 
diff --git a/modules/caddyhttp/ip_matchers.go b/modules/caddyhttp/ip_matchers.go
index 99eb39dff..5e0b356e7 100644
--- a/modules/caddyhttp/ip_matchers.go
+++ b/modules/caddyhttp/ip_matchers.go
@@ -108,7 +108,7 @@ func (MatchRemoteIP) CELLibrary(ctx caddy.Context) (cel.Library, error) {
 		// internal data type of the MatchPath value.
 		[]*cel.Type{cel.ListType(cel.StringType)},
 		// function to convert a constant list of strings to a MatchPath instance.
-		func(data ref.Val) (RequestMatcher, error) {
+		func(data ref.Val) (RequestMatcherWithError, error) {
 			refStringList := reflect.TypeOf([]string{})
 			strList, err := data.ConvertToNative(refStringList)
 			if err != nil {
@@ -145,9 +145,23 @@ func (m *MatchRemoteIP) Provision(ctx caddy.Context) error {
 
 // Match returns true if r matches m.
 func (m MatchRemoteIP) Match(r *http.Request) bool {
+	match, err := m.MatchWithError(r)
+	if err != nil {
+		SetVar(r.Context(), MatcherErrorVarKey, err)
+	}
+	return match
+}
+
+// MatchWithError returns true if r matches m.
+func (m MatchRemoteIP) MatchWithError(r *http.Request) (bool, error) {
+	// if handshake is not finished, we infer 0-RTT that has
+	// not verified remote IP; could be spoofed, so we throw
+	// HTTP 425 status to tell the client to try again after
+	// the handshake is complete
 	if r.TLS != nil && !r.TLS.HandshakeComplete {
-		return false // if handshake is not finished, we infer 0-RTT that has not verified remote IP; could be spoofed
+		return false, Error(http.StatusTooEarly, fmt.Errorf("TLS handshake not complete, remote IP cannot be verified"))
 	}
+
 	address := r.RemoteAddr
 	clientIP, zoneID, err := parseIPZoneFromString(address)
 	if err != nil {
@@ -155,7 +169,7 @@ func (m MatchRemoteIP) Match(r *http.Request) bool {
 			c.Write(zap.Error(err))
 		}
 
-		return false
+		return false, nil
 	}
 	matches, zoneFilter := matchIPByCidrZones(clientIP, zoneID, m.cidrs, m.zones)
 	if !matches && !zoneFilter {
@@ -163,7 +177,7 @@ func (m MatchRemoteIP) Match(r *http.Request) bool {
 			c.Write(zap.String("zone", zoneID))
 		}
 	}
-	return matches
+	return matches, nil
 }
 
 // CaddyModule returns the Caddy module information.
@@ -207,7 +221,7 @@ func (MatchClientIP) CELLibrary(ctx caddy.Context) (cel.Library, error) {
 		// internal data type of the MatchPath value.
 		[]*cel.Type{cel.ListType(cel.StringType)},
 		// function to convert a constant list of strings to a MatchPath instance.
-		func(data ref.Val) (RequestMatcher, error) {
+		func(data ref.Val) (RequestMatcherWithError, error) {
 			refStringList := reflect.TypeOf([]string{})
 			strList, err := data.ConvertToNative(refStringList)
 			if err != nil {
@@ -238,20 +252,34 @@ func (m *MatchClientIP) Provision(ctx caddy.Context) error {
 
 // Match returns true if r matches m.
 func (m MatchClientIP) Match(r *http.Request) bool {
+	match, err := m.MatchWithError(r)
+	if err != nil {
+		SetVar(r.Context(), MatcherErrorVarKey, err)
+	}
+	return match
+}
+
+// MatchWithError returns true if r matches m.
+func (m MatchClientIP) MatchWithError(r *http.Request) (bool, error) {
+	// if handshake is not finished, we infer 0-RTT that has
+	// not verified remote IP; could be spoofed, so we throw
+	// HTTP 425 status to tell the client to try again after
+	// the handshake is complete
 	if r.TLS != nil && !r.TLS.HandshakeComplete {
-		return false // if handshake is not finished, we infer 0-RTT that has not verified remote IP; could be spoofed
+		return false, Error(http.StatusTooEarly, fmt.Errorf("TLS handshake not complete, remote IP cannot be verified"))
 	}
+
 	address := GetVar(r.Context(), ClientIPVarKey).(string)
 	clientIP, zoneID, err := parseIPZoneFromString(address)
 	if err != nil {
 		m.logger.Error("getting client IP", zap.Error(err))
-		return false
+		return false, nil
 	}
 	matches, zoneFilter := matchIPByCidrZones(clientIP, zoneID, m.cidrs, m.zones)
 	if !matches && !zoneFilter {
 		m.logger.Debug("zone ID from client IP did not match", zap.String("zone", zoneID))
 	}
-	return matches
+	return matches, nil
 }
 
 func provisionCidrsZonesFromRanges(ranges []string) ([]*netip.Prefix, []string, error) {
@@ -326,13 +354,13 @@ func matchIPByCidrZones(clientIP netip.Addr, zoneID string, cidrs []*netip.Prefi
 
 // Interface guards
 var (
-	_ RequestMatcher        = (*MatchRemoteIP)(nil)
-	_ caddy.Provisioner     = (*MatchRemoteIP)(nil)
-	_ caddyfile.Unmarshaler = (*MatchRemoteIP)(nil)
-	_ CELLibraryProducer    = (*MatchRemoteIP)(nil)
-
-	_ RequestMatcher        = (*MatchClientIP)(nil)
-	_ caddy.Provisioner     = (*MatchClientIP)(nil)
-	_ caddyfile.Unmarshaler = (*MatchClientIP)(nil)
-	_ CELLibraryProducer    = (*MatchClientIP)(nil)
+	_ RequestMatcherWithError = (*MatchRemoteIP)(nil)
+	_ caddy.Provisioner       = (*MatchRemoteIP)(nil)
+	_ caddyfile.Unmarshaler   = (*MatchRemoteIP)(nil)
+	_ CELLibraryProducer      = (*MatchRemoteIP)(nil)
+
+	_ RequestMatcherWithError = (*MatchClientIP)(nil)
+	_ caddy.Provisioner       = (*MatchClientIP)(nil)
+	_ caddyfile.Unmarshaler   = (*MatchClientIP)(nil)
+	_ CELLibraryProducer      = (*MatchClientIP)(nil)
 )
diff --git a/modules/caddyhttp/matchers.go b/modules/caddyhttp/matchers.go
index 93a36237b..25fdc1fea 100644
--- a/modules/caddyhttp/matchers.go
+++ b/modules/caddyhttp/matchers.go
@@ -296,6 +296,12 @@ func (m MatchHost) Provision(_ caddy.Context) error {
 
 // Match returns true if r matches m.
 func (m MatchHost) Match(r *http.Request) bool {
+	match, _ := m.MatchWithError(r)
+	return match
+}
+
+// MatchWithError returns true if r matches m.
+func (m MatchHost) MatchWithError(r *http.Request) (bool, error) {
 	reqHost, _, err := net.SplitHostPort(r.Host)
 	if err != nil {
 		// OK; probably didn't have a port
@@ -315,7 +321,7 @@ func (m MatchHost) Match(r *http.Request) bool {
 			return m[i] >= reqHost
 		})
 		if pos < len(m) && m[pos] == reqHost {
-			return true
+			return true, nil
 		}
 	}
 
@@ -346,13 +352,13 @@ outer:
 					continue outer
 				}
 			}
-			return true
+			return true, nil
 		} else if strings.EqualFold(reqHost, host) {
-			return true
+			return true, nil
 		}
 	}
 
-	return false
+	return false, nil
 }
 
 // CELLibrary produces options that expose this matcher for use in CEL
@@ -366,7 +372,7 @@ func (MatchHost) CELLibrary(ctx caddy.Context) (cel.Library, error) {
 		"host",
 		"host_match_request_list",
 		[]*cel.Type{cel.ListType(cel.StringType)},
-		func(data ref.Val) (RequestMatcher, error) {
+		func(data ref.Val) (RequestMatcherWithError, error) {
 			refStringList := reflect.TypeOf([]string{})
 			strList, err := data.ConvertToNative(refStringList)
 			if err != nil {
@@ -411,6 +417,12 @@ func (m MatchPath) Provision(_ caddy.Context) error {
 
 // Match returns true if r matches m.
 func (m MatchPath) Match(r *http.Request) bool {
+	match, _ := m.MatchWithError(r)
+	return match
+}
+
+// MatchWithError returns true if r matches m.
+func (m MatchPath) MatchWithError(r *http.Request) (bool, error) {
 	// Even though RFC 9110 says that path matching is case-sensitive
 	// (https://www.rfc-editor.org/rfc/rfc9110.html#section-4.2.3),
 	// we do case-insensitive matching to mitigate security issues
@@ -436,7 +448,7 @@ func (m MatchPath) Match(r *http.Request) bool {
 		// special case: whole path is wildcard; this is unnecessary
 		// as it matches all requests, which is the same as no matcher
 		if matchPattern == "*" {
-			return true
+			return true, nil
 		}
 
 		// Clean the path, merge doubled slashes, etc.
@@ -464,7 +476,7 @@ func (m MatchPath) Match(r *http.Request) bool {
 		if strings.Contains(matchPattern, "%") {
 			reqPathForPattern := CleanPath(r.URL.EscapedPath(), mergeSlashes)
 			if m.matchPatternWithEscapeSequence(reqPathForPattern, matchPattern) {
-				return true
+				return true, nil
 			}
 
 			// doing prefix/suffix/substring matches doesn't make sense
@@ -483,7 +495,7 @@ func (m MatchPath) Match(r *http.Request) bool {
 			strings.HasPrefix(matchPattern, "*") &&
 			strings.HasSuffix(matchPattern, "*") {
 			if strings.Contains(reqPathForPattern, matchPattern[1:len(matchPattern)-1]) {
-				return true
+				return true, nil
 			}
 			continue
 		}
@@ -495,7 +507,7 @@ func (m MatchPath) Match(r *http.Request) bool {
 			// treat it as a fast suffix match
 			if strings.HasPrefix(matchPattern, "*") {
 				if strings.HasSuffix(reqPathForPattern, matchPattern[1:]) {
-					return true
+					return true, nil
 				}
 				continue
 			}
@@ -504,7 +516,7 @@ func (m MatchPath) Match(r *http.Request) bool {
 			// treat it as a fast prefix match
 			if strings.HasSuffix(matchPattern, "*") {
 				if strings.HasPrefix(reqPathForPattern, matchPattern[:len(matchPattern)-1]) {
-					return true
+					return true, nil
 				}
 				continue
 			}
@@ -515,10 +527,10 @@ func (m MatchPath) Match(r *http.Request) bool {
 		// because we can't handle it anyway
 		matches, _ := path.Match(matchPattern, reqPathForPattern)
 		if matches {
-			return true
+			return true, nil
 		}
 	}
-	return false
+	return false, nil
 }
 
 func (MatchPath) matchPatternWithEscapeSequence(escapedPath, matchPath string) bool {
@@ -642,7 +654,7 @@ func (MatchPath) CELLibrary(ctx caddy.Context) (cel.Library, error) {
 		// internal data type of the MatchPath value.
 		[]*cel.Type{cel.ListType(cel.StringType)},
 		// function to convert a constant list of strings to a MatchPath instance.
-		func(data ref.Val) (RequestMatcher, error) {
+		func(data ref.Val) (RequestMatcherWithError, error) {
 			refStringList := reflect.TypeOf([]string{})
 			strList, err := data.ConvertToNative(refStringList)
 			if err != nil {
@@ -677,6 +689,12 @@ func (MatchPathRE) CaddyModule() caddy.ModuleInfo {
 
 // Match returns true if r matches m.
 func (m MatchPathRE) Match(r *http.Request) bool {
+	match, _ := m.MatchWithError(r)
+	return match
+}
+
+// MatchWithError returns true if r matches m.
+func (m MatchPathRE) MatchWithError(r *http.Request) (bool, error) {
 	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 
 	// Clean the path, merges doubled slashes, etc.
@@ -684,7 +702,7 @@ func (m MatchPathRE) Match(r *http.Request) bool {
 	// the path matcher. See #4407
 	cleanedPath := cleanPath(r.URL.Path)
 
-	return m.MatchRegexp.Match(cleanedPath, repl)
+	return m.MatchRegexp.Match(cleanedPath, repl), nil
 }
 
 // CELLibrary produces options that expose this matcher for use in CEL
@@ -698,7 +716,7 @@ func (MatchPathRE) CELLibrary(ctx caddy.Context) (cel.Library, error) {
 		"path_regexp",
 		"path_regexp_request_string",
 		[]*cel.Type{cel.StringType},
-		func(data ref.Val) (RequestMatcher, error) {
+		func(data ref.Val) (RequestMatcherWithError, error) {
 			pattern := data.(types.String)
 			matcher := MatchPathRE{MatchRegexp{
 				Name:    ctx.Value(MatcherNameCtxKey).(string),
@@ -715,7 +733,7 @@ func (MatchPathRE) CELLibrary(ctx caddy.Context) (cel.Library, error) {
 		"path_regexp",
 		"path_regexp_request_string_string",
 		[]*cel.Type{cel.StringType, cel.StringType},
-		func(data ref.Val) (RequestMatcher, error) {
+		func(data ref.Val) (RequestMatcherWithError, error) {
 			refStringList := reflect.TypeOf([]string{})
 			params, err := data.ConvertToNative(refStringList)
 			if err != nil {
@@ -764,7 +782,13 @@ func (m *MatchMethod) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 
 // Match returns true if r matches m.
 func (m MatchMethod) Match(r *http.Request) bool {
-	return slices.Contains(m, r.Method)
+	match, _ := m.MatchWithError(r)
+	return match
+}
+
+// MatchWithError returns true if r matches m.
+func (m MatchMethod) MatchWithError(r *http.Request) (bool, error) {
+	return slices.Contains(m, r.Method), nil
 }
 
 // CELLibrary produces options that expose this matcher for use in CEL
@@ -778,7 +802,7 @@ func (MatchMethod) CELLibrary(_ caddy.Context) (cel.Library, error) {
 		"method",
 		"method_request_list",
 		[]*cel.Type{cel.ListType(cel.StringType)},
-		func(data ref.Val) (RequestMatcher, error) {
+		func(data ref.Val) (RequestMatcherWithError, error) {
 			refStringList := reflect.TypeOf([]string{})
 			strList, err := data.ConvertToNative(refStringList)
 			if err != nil {
@@ -823,10 +847,17 @@ func (m *MatchQuery) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 
 // Match returns true if r matches m. An empty m matches an empty query string.
 func (m MatchQuery) Match(r *http.Request) bool {
+	match, _ := m.MatchWithError(r)
+	return match
+}
+
+// MatchWithError returns true if r matches m.
+// An empty m matches an empty query string.
+func (m MatchQuery) MatchWithError(r *http.Request) (bool, error) {
 	// If no query keys are configured, this only
 	// matches an empty query string.
 	if len(m) == 0 {
-		return len(r.URL.Query()) == 0
+		return len(r.URL.Query()) == 0, nil
 	}
 
 	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
@@ -843,7 +874,7 @@ func (m MatchQuery) Match(r *http.Request) bool {
 		// "Relying on parser alignment for security is doomed." Overall conclusion is that
 		// splitting on & and rejecting ; in key=value pairs is safer than accepting raw ;.
 		// We regard the Go team's decision as sound and thus reject malformed query strings.
-		return false
+		return false, nil
 	}
 
 	// Count the amount of matched keys, to ensure we AND
@@ -854,7 +885,7 @@ func (m MatchQuery) Match(r *http.Request) bool {
 		param = repl.ReplaceAll(param, "")
 		paramVal, found := parsed[param]
 		if !found {
-			return false
+			return false, nil
 		}
 		for _, v := range vals {
 			v = repl.ReplaceAll(v, "")
@@ -864,7 +895,7 @@ func (m MatchQuery) Match(r *http.Request) bool {
 			}
 		}
 	}
-	return matchedKeys == len(m)
+	return matchedKeys == len(m), nil
 }
 
 // CELLibrary produces options that expose this matcher for use in CEL
@@ -878,7 +909,7 @@ func (MatchQuery) CELLibrary(_ caddy.Context) (cel.Library, error) {
 		"query",
 		"query_matcher_request_map",
 		[]*cel.Type{CELTypeJSON},
-		func(data ref.Val) (RequestMatcher, error) {
+		func(data ref.Val) (RequestMatcherWithError, error) {
 			mapStrListStr, err := CELValueToMapStrList(data)
 			if err != nil {
 				return nil, err
@@ -940,8 +971,14 @@ func (m *MatchHeader) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 
 // Match returns true if r matches m.
 func (m MatchHeader) Match(r *http.Request) bool {
+	match, _ := m.MatchWithError(r)
+	return match
+}
+
+// MatchWithError returns true if r matches m.
+func (m MatchHeader) MatchWithError(r *http.Request) (bool, error) {
 	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
-	return matchHeaders(r.Header, http.Header(m), r.Host, repl)
+	return matchHeaders(r.Header, http.Header(m), r.Host, repl), nil
 }
 
 // CELLibrary produces options that expose this matcher for use in CEL
@@ -956,7 +993,7 @@ func (MatchHeader) CELLibrary(_ caddy.Context) (cel.Library, error) {
 		"header",
 		"header_matcher_request_map",
 		[]*cel.Type{CELTypeJSON},
-		func(data ref.Val) (RequestMatcher, error) {
+		func(data ref.Val) (RequestMatcherWithError, error) {
 			mapStrListStr, err := CELValueToMapStrList(data)
 			if err != nil {
 				return nil, err
@@ -1075,6 +1112,12 @@ func (m *MatchHeaderRE) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 
 // Match returns true if r matches m.
 func (m MatchHeaderRE) Match(r *http.Request) bool {
+	match, _ := m.MatchWithError(r)
+	return match
+}
+
+// MatchWithError returns true if r matches m.
+func (m MatchHeaderRE) MatchWithError(r *http.Request) (bool, error) {
 	for field, rm := range m {
 		actualFieldVals := getHeaderFieldVals(r.Header, field, r.Host)
 		match := false
@@ -1087,10 +1130,10 @@ func (m MatchHeaderRE) Match(r *http.Request) bool {
 			}
 		}
 		if !match {
-			return false
+			return false, nil
 		}
 	}
-	return true
+	return true, nil
 }
 
 // Provision compiles m's regular expressions.
@@ -1126,7 +1169,7 @@ func (MatchHeaderRE) CELLibrary(ctx caddy.Context) (cel.Library, error) {
 		"header_regexp",
 		"header_regexp_request_string_string",
 		[]*cel.Type{cel.StringType, cel.StringType},
-		func(data ref.Val) (RequestMatcher, error) {
+		func(data ref.Val) (RequestMatcherWithError, error) {
 			refStringList := reflect.TypeOf([]string{})
 			params, err := data.ConvertToNative(refStringList)
 			if err != nil {
@@ -1149,7 +1192,7 @@ func (MatchHeaderRE) CELLibrary(ctx caddy.Context) (cel.Library, error) {
 		"header_regexp",
 		"header_regexp_request_string_string_string",
 		[]*cel.Type{cel.StringType, cel.StringType, cel.StringType},
-		func(data ref.Val) (RequestMatcher, error) {
+		func(data ref.Val) (RequestMatcherWithError, error) {
 			refStringList := reflect.TypeOf([]string{})
 			params, err := data.ConvertToNative(refStringList)
 			if err != nil {
@@ -1187,31 +1230,37 @@ func (MatchProtocol) CaddyModule() caddy.ModuleInfo {
 
 // Match returns true if r matches m.
 func (m MatchProtocol) Match(r *http.Request) bool {
+	match, _ := m.MatchWithError(r)
+	return match
+}
+
+// MatchWithError returns true if r matches m.
+func (m MatchProtocol) MatchWithError(r *http.Request) (bool, error) {
 	switch string(m) {
 	case "grpc":
-		return strings.HasPrefix(r.Header.Get("content-type"), "application/grpc")
+		return strings.HasPrefix(r.Header.Get("content-type"), "application/grpc"), nil
 	case "https":
-		return r.TLS != nil
+		return r.TLS != nil, nil
 	case "http":
-		return r.TLS == nil
+		return r.TLS == nil, nil
 	case "http/1.0":
-		return r.ProtoMajor == 1 && r.ProtoMinor == 0
+		return r.ProtoMajor == 1 && r.ProtoMinor == 0, nil
 	case "http/1.0+":
-		return r.ProtoAtLeast(1, 0)
+		return r.ProtoAtLeast(1, 0), nil
 	case "http/1.1":
-		return r.ProtoMajor == 1 && r.ProtoMinor == 1
+		return r.ProtoMajor == 1 && r.ProtoMinor == 1, nil
 	case "http/1.1+":
-		return r.ProtoAtLeast(1, 1)
+		return r.ProtoAtLeast(1, 1), nil
 	case "http/2":
-		return r.ProtoMajor == 2
+		return r.ProtoMajor == 2, nil
 	case "http/2+":
-		return r.ProtoAtLeast(2, 0)
+		return r.ProtoAtLeast(2, 0), nil
 	case "http/3":
-		return r.ProtoMajor == 3
+		return r.ProtoMajor == 3, nil
 	case "http/3+":
-		return r.ProtoAtLeast(3, 0)
+		return r.ProtoAtLeast(3, 0), nil
 	}
-	return false
+	return false, nil
 }
 
 // UnmarshalCaddyfile implements caddyfile.Unmarshaler.
@@ -1238,7 +1287,7 @@ func (MatchProtocol) CELLibrary(_ caddy.Context) (cel.Library, error) {
 		"protocol",
 		"protocol_request_string",
 		[]*cel.Type{cel.StringType},
-		func(data ref.Val) (RequestMatcher, error) {
+		func(data ref.Val) (RequestMatcherWithError, error) {
 			protocolStr, ok := data.(types.String)
 			if !ok {
 				return nil, errors.New("protocol argument was not a string")
@@ -1258,16 +1307,22 @@ func (MatchTLS) CaddyModule() caddy.ModuleInfo {
 
 // Match returns true if r matches m.
 func (m MatchTLS) Match(r *http.Request) bool {
+	match, _ := m.MatchWithError(r)
+	return match
+}
+
+// MatchWithError returns true if r matches m.
+func (m MatchTLS) MatchWithError(r *http.Request) (bool, error) {
 	if r.TLS == nil {
-		return false
+		return false, nil
 	}
 	if m.HandshakeComplete != nil {
 		if (!*m.HandshakeComplete && r.TLS.HandshakeComplete) ||
 			(*m.HandshakeComplete && !r.TLS.HandshakeComplete) {
-			return false
+			return false, nil
 		}
 	}
-	return true
+	return true, nil
 }
 
 // UnmarshalCaddyfile parses Caddyfile tokens for this matcher. Syntax:
@@ -1337,7 +1392,15 @@ func (m *MatchNot) Provision(ctx caddy.Context) error {
 	for _, modMap := range matcherSets.([]map[string]any) {
 		var ms MatcherSet
 		for _, modIface := range modMap {
-			ms = append(ms, modIface.(RequestMatcher))
+			if mod, ok := modIface.(RequestMatcherWithError); ok {
+				ms = append(ms, mod)
+				continue
+			}
+			if mod, ok := modIface.(RequestMatcher); ok {
+				ms = append(ms, mod)
+				continue
+			}
+			return fmt.Errorf("module is not a request matcher: %T", modIface)
 		}
 		m.MatcherSets = append(m.MatcherSets, ms)
 	}
@@ -1348,12 +1411,24 @@ func (m *MatchNot) Provision(ctx caddy.Context) error {
 // the embedded matchers, false is returned if any of its matcher
 // sets return true.
 func (m MatchNot) Match(r *http.Request) bool {
+	match, _ := m.MatchWithError(r)
+	return match
+}
+
+// MatchWithError returns true if r matches m. Since this matcher
+// negates the embedded matchers, false is returned if any of its
+// matcher sets return true.
+func (m MatchNot) MatchWithError(r *http.Request) (bool, error) {
 	for _, ms := range m.MatcherSets {
-		if ms.Match(r) {
-			return false
+		matches, err := ms.MatchWithError(r)
+		if err != nil {
+			return false, err
+		}
+		if matches {
+			return false, nil
 		}
 	}
-	return true
+	return true, nil
 }
 
 // MatchRegexp is an embedable type for matching
@@ -1469,7 +1544,7 @@ func (mre *MatchRegexp) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 // ParseCaddyfileNestedMatcher parses the Caddyfile tokens for a nested
 // matcher set, and returns its raw module map value.
 func ParseCaddyfileNestedMatcherSet(d *caddyfile.Dispenser) (caddy.ModuleMap, error) {
-	matcherMap := make(map[string]RequestMatcher)
+	matcherMap := make(map[string]any)
 
 	// in case there are multiple instances of the same matcher, concatenate
 	// their tokens (we expect that UnmarshalCaddyfile should be able to
@@ -1494,11 +1569,15 @@ func ParseCaddyfileNestedMatcherSet(d *caddyfile.Dispenser) (caddy.ModuleMap, er
 		if err != nil {
 			return nil, err
 		}
-		rm, ok := unm.(RequestMatcher)
-		if !ok {
-			return nil, fmt.Errorf("matcher module '%s' is not a request matcher", matcherName)
+		if rm, ok := unm.(RequestMatcherWithError); ok {
+			matcherMap[matcherName] = rm
+			continue
 		}
-		matcherMap[matcherName] = rm
+		if rm, ok := unm.(RequestMatcher); ok {
+			matcherMap[matcherName] = rm
+			continue
+		}
+		return nil, fmt.Errorf("matcher module '%s' is not a request matcher", matcherName)
 	}
 
 	// we should now have a functional matcher, but we also
@@ -1524,24 +1603,28 @@ const regexpPlaceholderPrefix = "http.regexp"
 // holds an optional error emitted from a request matcher,
 // to short-circuit the handler chain, since matchers cannot
 // return errors via the RequestMatcher interface.
+//
+// Deprecated: Matchers should implement RequestMatcherWithError
+// which can return an error directly, instead of smuggling it
+// through the vars map.
 const MatcherErrorVarKey = "matchers.error"
 
 // Interface guards
 var (
-	_ RequestMatcher    = (*MatchHost)(nil)
-	_ caddy.Provisioner = (*MatchHost)(nil)
-	_ RequestMatcher    = (*MatchPath)(nil)
-	_ RequestMatcher    = (*MatchPathRE)(nil)
-	_ caddy.Provisioner = (*MatchPathRE)(nil)
-	_ RequestMatcher    = (*MatchMethod)(nil)
-	_ RequestMatcher    = (*MatchQuery)(nil)
-	_ RequestMatcher    = (*MatchHeader)(nil)
-	_ RequestMatcher    = (*MatchHeaderRE)(nil)
-	_ caddy.Provisioner = (*MatchHeaderRE)(nil)
-	_ RequestMatcher    = (*MatchProtocol)(nil)
-	_ RequestMatcher    = (*MatchNot)(nil)
-	_ caddy.Provisioner = (*MatchNot)(nil)
-	_ caddy.Provisioner = (*MatchRegexp)(nil)
+	_ RequestMatcherWithError = (*MatchHost)(nil)
+	_ caddy.Provisioner       = (*MatchHost)(nil)
+	_ RequestMatcherWithError = (*MatchPath)(nil)
+	_ RequestMatcherWithError = (*MatchPathRE)(nil)
+	_ caddy.Provisioner       = (*MatchPathRE)(nil)
+	_ RequestMatcherWithError = (*MatchMethod)(nil)
+	_ RequestMatcherWithError = (*MatchQuery)(nil)
+	_ RequestMatcherWithError = (*MatchHeader)(nil)
+	_ RequestMatcherWithError = (*MatchHeaderRE)(nil)
+	_ caddy.Provisioner       = (*MatchHeaderRE)(nil)
+	_ RequestMatcherWithError = (*MatchProtocol)(nil)
+	_ RequestMatcherWithError = (*MatchNot)(nil)
+	_ caddy.Provisioner       = (*MatchNot)(nil)
+	_ caddy.Provisioner       = (*MatchRegexp)(nil)
 
 	_ caddyfile.Unmarshaler = (*MatchHost)(nil)
 	_ caddyfile.Unmarshaler = (*MatchPath)(nil)
diff --git a/modules/caddyhttp/matchers_test.go b/modules/caddyhttp/matchers_test.go
index 05eaade5b..f7be6909e 100644
--- a/modules/caddyhttp/matchers_test.go
+++ b/modules/caddyhttp/matchers_test.go
@@ -158,7 +158,10 @@ func TestHostMatcher(t *testing.T) {
 			t.Errorf("Test %d %v: provisioning failed: %v", i, tc.match, err)
 		}
 
-		actual := tc.match.Match(req)
+		actual, err := tc.match.MatchWithError(req)
+		if err != nil {
+			t.Errorf("Test %d %v: matching failed: %v", i, tc.match, err)
+		}
 		if actual != tc.expect {
 			t.Errorf("Test %d %v: Expected %t, got %t for '%s'", i, tc.match, tc.expect, actual, tc.input)
 			continue
@@ -430,7 +433,10 @@ func TestPathMatcher(t *testing.T) {
 		ctx := context.WithValue(req.Context(), caddy.ReplacerCtxKey, repl)
 		req = req.WithContext(ctx)
 
-		actual := tc.match.Match(req)
+		actual, err := tc.match.MatchWithError(req)
+		if err != nil {
+			t.Errorf("Test %d %v: matching failed: %v", i, tc.match, err)
+		}
 		if actual != tc.expect {
 			t.Errorf("Test %d %v: Expected %t, got %t for '%s'", i, tc.match, tc.expect, actual, tc.input)
 			continue
@@ -451,7 +457,10 @@ func TestPathMatcherWindows(t *testing.T) {
 	req = req.WithContext(ctx)
 
 	match := MatchPath{"*.php"}
-	matched := match.Match(req)
+	matched, err := match.MatchWithError(req)
+	if err != nil {
+		t.Errorf("Expected no error, but got: %v", err)
+	}
 	if !matched {
 		t.Errorf("Expected to match; should ignore trailing dots and spaces")
 	}
@@ -555,7 +564,10 @@ func TestPathREMatcher(t *testing.T) {
 		req = req.WithContext(ctx)
 		addHTTPVarsToReplacer(repl, req, httptest.NewRecorder())
 
-		actual := tc.match.Match(req)
+		actual, err := tc.match.MatchWithError(req)
+		if err != nil {
+			t.Errorf("Test %d %v: matching failed: %v", i, tc.match, err)
+		}
 		if actual != tc.expect {
 			t.Errorf("Test %d [%v]: Expected %t, got %t for input '%s'",
 				i, tc.match.Pattern, tc.expect, actual, tc.input)
@@ -691,7 +703,10 @@ func TestHeaderMatcher(t *testing.T) {
 		ctx := context.WithValue(req.Context(), caddy.ReplacerCtxKey, repl)
 		req = req.WithContext(ctx)
 
-		actual := tc.match.Match(req)
+		actual, err := tc.match.MatchWithError(req)
+		if err != nil {
+			t.Errorf("Test %d %v: matching failed: %v", i, tc.match, err)
+		}
 		if actual != tc.expect {
 			t.Errorf("Test %d %v: Expected %t, got %t for '%s'", i, tc.match, tc.expect, actual, tc.input)
 			continue
@@ -818,7 +833,10 @@ func TestQueryMatcher(t *testing.T) {
 		repl.Set("http.vars.debug", "1")
 		repl.Set("http.vars.key", "somekey")
 		req = req.WithContext(ctx)
-		actual := tc.match.Match(req)
+		actual, err := tc.match.MatchWithError(req)
+		if err != nil {
+			t.Errorf("Test %d %v: matching failed: %v", i, tc.match, err)
+		}
 		if actual != tc.expect {
 			t.Errorf("Test %d %v: Expected %t, got %t for '%s'", i, tc.match, tc.expect, actual, tc.input)
 			continue
@@ -887,7 +905,10 @@ func TestHeaderREMatcher(t *testing.T) {
 		req = req.WithContext(ctx)
 		addHTTPVarsToReplacer(repl, req, httptest.NewRecorder())
 
-		actual := tc.match.Match(req)
+		actual, err := tc.match.MatchWithError(req)
+		if err != nil {
+			t.Errorf("Test %d %v: matching failed: %v", i, tc.match, err)
+		}
 		if actual != tc.expect {
 			t.Errorf("Test %d [%v]: Expected %t, got %t for input '%s'",
 				i, tc.match, tc.expect, actual, tc.input)
@@ -927,7 +948,7 @@ func BenchmarkHeaderREMatcher(b *testing.B) {
 	req = req.WithContext(ctx)
 	addHTTPVarsToReplacer(repl, req, httptest.NewRecorder())
 	for run := 0; run < b.N; run++ {
-		match.Match(req)
+		match.MatchWithError(req)
 	}
 }
 
@@ -998,7 +1019,10 @@ func TestVarREMatcher(t *testing.T) {
 
 			tc.input.ServeHTTP(httptest.NewRecorder(), req, emptyHandler)
 
-			actual := tc.match.Match(req)
+			actual, err := tc.match.MatchWithError(req)
+			if err != nil {
+				t.Errorf("Test %d %v: matching failed: %v", i, tc.match, err)
+			}
 			if actual != tc.expect {
 				t.Errorf("Test %d [%v]: Expected %t, got %t for input '%s'",
 					i, tc.match, tc.expect, actual, tc.input)
@@ -1123,7 +1147,10 @@ func TestNotMatcher(t *testing.T) {
 		ctx := context.WithValue(req.Context(), caddy.ReplacerCtxKey, repl)
 		req = req.WithContext(ctx)
 
-		actual := tc.match.Match(req)
+		actual, err := tc.match.MatchWithError(req)
+		if err != nil {
+			t.Errorf("Test %d %v: matching failed: %v", i, tc.match, err)
+		}
 		if actual != tc.expect {
 			t.Errorf("Test %d %+v: Expected %t, got %t for: host=%s path=%s'", i, tc.match, tc.expect, actual, tc.host, tc.path)
 			continue
@@ -1155,7 +1182,7 @@ func BenchmarkLargeHostMatcher(b *testing.B) {
 
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		matcher.Match(req)
+		matcher.MatchWithError(req)
 	}
 }
 
@@ -1169,7 +1196,7 @@ func BenchmarkHostMatcherWithoutPlaceholder(b *testing.B) {
 
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		match.Match(req)
+		match.MatchWithError(req)
 	}
 }
 
@@ -1187,6 +1214,6 @@ func BenchmarkHostMatcherWithPlaceholder(b *testing.B) {
 
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		match.Match(req)
+		match.MatchWithError(req)
 	}
 }
diff --git a/modules/caddyhttp/reverseproxy/healthchecks.go b/modules/caddyhttp/reverseproxy/healthchecks.go
index 1735e45a4..f0ffee5b8 100644
--- a/modules/caddyhttp/reverseproxy/healthchecks.go
+++ b/modules/caddyhttp/reverseproxy/healthchecks.go
@@ -72,7 +72,7 @@ type HealthChecks struct {
 // health checks (that is, health checks which occur in a
 // background goroutine independently).
 type ActiveHealthChecks struct {
-	// DEPRECATED: Use 'uri' instead. This field will be removed. TODO: remove this field
+	// Deprecated: Use 'uri' instead. This field will be removed. TODO: remove this field
 	Path string `json:"path,omitempty"`
 
 	// The URI (path and query) to use for health checks
diff --git a/modules/caddyhttp/reverseproxy/httptransport.go b/modules/caddyhttp/reverseproxy/httptransport.go
index 2b4c3f094..910033ca1 100644
--- a/modules/caddyhttp/reverseproxy/httptransport.go
+++ b/modules/caddyhttp/reverseproxy/httptransport.go
@@ -545,11 +545,11 @@ type TLSConfig struct {
 	// Certificate authority module which provides the certificate pool of trusted certificates
 	CARaw json.RawMessage `json:"ca,omitempty" caddy:"namespace=tls.ca_pool.source inline_key=provider"`
 
-	// DEPRECATED: Use the `ca` field with the `tls.ca_pool.source.inline` module instead.
+	// Deprecated: Use the `ca` field with the `tls.ca_pool.source.inline` module instead.
 	// Optional list of base64-encoded DER-encoded CA certificates to trust.
 	RootCAPool []string `json:"root_ca_pool,omitempty"`
 
-	// DEPRECATED: Use the `ca` field with the `tls.ca_pool.source.file` module instead.
+	// Deprecated: Use the `ca` field with the `tls.ca_pool.source.file` module instead.
 	// List of PEM-encoded CA certificate files to add to the same trust
 	// store as RootCAPool (or root_ca_pool in the JSON).
 	RootCAPEMFiles []string `json:"root_ca_pem_files,omitempty"`
diff --git a/modules/caddyhttp/reverseproxy/reverseproxy.go b/modules/caddyhttp/reverseproxy/reverseproxy.go
index 1250eae6c..5ef37a4e8 100644
--- a/modules/caddyhttp/reverseproxy/reverseproxy.go
+++ b/modules/caddyhttp/reverseproxy/reverseproxy.go
@@ -496,7 +496,7 @@ func (h *Handler) proxyLoopIteration(r *http.Request, origReq *http.Request, w h
 		if proxyErr == nil {
 			proxyErr = caddyhttp.Error(http.StatusServiceUnavailable, errNoUpstream)
 		}
-		if !h.LoadBalancing.tryAgain(h.ctx, start, retries, proxyErr, r) {
+		if !h.LoadBalancing.tryAgain(h.ctx, start, retries, proxyErr, r, h.logger) {
 			return true, proxyErr
 		}
 		return false, proxyErr
@@ -562,7 +562,7 @@ func (h *Handler) proxyLoopIteration(r *http.Request, origReq *http.Request, w h
 	h.countFailure(upstream)
 
 	// if we've tried long enough, break
-	if !h.LoadBalancing.tryAgain(h.ctx, start, retries, proxyErr, r) {
+	if !h.LoadBalancing.tryAgain(h.ctx, start, retries, proxyErr, r, h.logger) {
 		return true, proxyErr
 	}
 
@@ -1089,7 +1089,7 @@ func (h *Handler) finalizeResponse(
 // If true is returned, it has already blocked long enough before
 // the next retry (i.e. no more sleeping is needed). If false is
 // returned, the handler should stop trying to proxy the request.
-func (lb LoadBalancing) tryAgain(ctx caddy.Context, start time.Time, retries int, proxyErr error, req *http.Request) bool {
+func (lb LoadBalancing) tryAgain(ctx caddy.Context, start time.Time, retries int, proxyErr error, req *http.Request, logger *zap.Logger) bool {
 	// no retries are configured
 	if lb.TryDuration == 0 && lb.Retries == 0 {
 		return false
@@ -1124,7 +1124,12 @@ func (lb LoadBalancing) tryAgain(ctx caddy.Context, start time.Time, retries int
 				return false
 			}
 
-			if !lb.RetryMatch.AnyMatch(req) {
+			match, err := lb.RetryMatch.AnyMatchWithError(req)
+			if err != nil {
+				logger.Error("error matching request for retry", zap.Error(err))
+				return false
+			}
+			if !match {
 				return false
 			}
 		}
diff --git a/modules/caddyhttp/routes.go b/modules/caddyhttp/routes.go
index 939d01e55..ccb5f2515 100644
--- a/modules/caddyhttp/routes.go
+++ b/modules/caddyhttp/routes.go
@@ -254,18 +254,13 @@ func wrapRoute(route Route) Middleware {
 			nextCopy := next
 
 			// route must match at least one of the matcher sets
-			if !route.MatcherSets.AnyMatch(req) {
+			matches, err := route.MatcherSets.AnyMatchWithError(req)
+			if err != nil {
 				// allow matchers the opportunity to short circuit
 				// the request and trigger the error handling chain
-				err, ok := GetVar(req.Context(), MatcherErrorVarKey).(error)
-				if ok {
-					// clear out the error from context, otherwise
-					// it will cascade to the error routes (#4916)
-					SetVar(req.Context(), MatcherErrorVarKey, nil)
-					// return the matcher's error
-					return err
-				}
-
+				return err
+			}
+			if !matches {
 				// call the next handler, and skip this one,
 				// since the matcher didn't match
 				return nextCopy.ServeHTTP(rw, req)
@@ -341,19 +336,58 @@ func wrapMiddleware(ctx caddy.Context, mh MiddlewareHandler, metrics *Metrics) M
 // MatcherSet is a set of matchers which
 // must all match in order for the request
 // to be matched successfully.
-type MatcherSet []RequestMatcher
+type MatcherSet []any
 
 // Match returns true if the request matches all
 // matchers in mset or if there are no matchers.
 func (mset MatcherSet) Match(r *http.Request) bool {
 	for _, m := range mset {
-		if !m.Match(r) {
-			return false
+		if me, ok := m.(RequestMatcherWithError); ok {
+			match, _ := me.MatchWithError(r)
+			if !match {
+				return false
+			}
+			continue
+		}
+		if me, ok := m.(RequestMatcher); ok {
+			if !me.Match(r) {
+				return false
+			}
+			continue
 		}
+		return false
 	}
 	return true
 }
 
+// MatchWithError returns true if r matches m.
+func (mset MatcherSet) MatchWithError(r *http.Request) (bool, error) {
+	for _, m := range mset {
+		if me, ok := m.(RequestMatcherWithError); ok {
+			match, err := me.MatchWithError(r)
+			if err != nil || !match {
+				return match, err
+			}
+			continue
+		}
+		if me, ok := m.(RequestMatcher); ok {
+			if !me.Match(r) {
+				// for backwards compatibility
+				err, ok := GetVar(r.Context(), MatcherErrorVarKey).(error)
+				if ok {
+					// clear out the error from context since we've consumed it
+					SetVar(r.Context(), MatcherErrorVarKey, nil)
+					return false, err
+				}
+				return false, nil
+			}
+			continue
+		}
+		return false, fmt.Errorf("matcher is not a RequestMatcher or RequestMatcherWithError: %#v", m)
+	}
+	return true, nil
+}
+
 // RawMatcherSets is a group of matcher sets
 // in their raw, JSON form.
 type RawMatcherSets []caddy.ModuleMap
@@ -366,25 +400,50 @@ type MatcherSets []MatcherSet
 // AnyMatch returns true if req matches any of the
 // matcher sets in ms or if there are no matchers,
 // in which case the request always matches.
+//
+// Deprecated: Use AnyMatchWithError instead.
 func (ms MatcherSets) AnyMatch(req *http.Request) bool {
 	for _, m := range ms {
-		if m.Match(req) {
-			return true
+		match, err := m.MatchWithError(req)
+		if err != nil {
+			SetVar(req.Context(), MatcherErrorVarKey, err)
+			return false
+		}
+		if match {
+			return match
 		}
 	}
 	return len(ms) == 0
 }
 
+// AnyMatchWithError returns true if req matches any of the
+// matcher sets in ms or if there are no matchers, in which
+// case the request always matches. If any matcher returns
+// an error, we cut short and return the error.
+func (ms MatcherSets) AnyMatchWithError(req *http.Request) (bool, error) {
+	for _, m := range ms {
+		match, err := m.MatchWithError(req)
+		if err != nil || match {
+			return match, err
+		}
+	}
+	return len(ms) == 0, nil
+}
+
 // FromInterface fills ms from an 'any' value obtained from LoadModule.
 func (ms *MatcherSets) FromInterface(matcherSets any) error {
 	for _, matcherSetIfaces := range matcherSets.([]map[string]any) {
 		var matcherSet MatcherSet
 		for _, matcher := range matcherSetIfaces {
-			reqMatcher, ok := matcher.(RequestMatcher)
-			if !ok {
-				return fmt.Errorf("decoded module is not a RequestMatcher: %#v", matcher)
+			if m, ok := matcher.(RequestMatcherWithError); ok {
+				matcherSet = append(matcherSet, m)
+				continue
+			}
+			if m, ok := matcher.(RequestMatcher); ok {
+				matcherSet = append(matcherSet, m)
+				continue
 			}
-			matcherSet = append(matcherSet, reqMatcher)
+			return fmt.Errorf("decoded module is not a RequestMatcher or RequestMatcherWithError: %#v", matcher)
 		}
 		*ms = append(*ms, matcherSet)
 	}
diff --git a/modules/caddyhttp/vars.go b/modules/caddyhttp/vars.go
index 77e06e3cb..7ab891fc0 100644
--- a/modules/caddyhttp/vars.go
+++ b/modules/caddyhttp/vars.go
@@ -166,8 +166,14 @@ func (m *VarsMatcher) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 // Match matches a request based on variables in the context,
 // or placeholders if the key is not a variable.
 func (m VarsMatcher) Match(r *http.Request) bool {
+	match, _ := m.MatchWithError(r)
+	return match
+}
+
+// MatchWithError returns true if r matches m.
+func (m VarsMatcher) MatchWithError(r *http.Request) (bool, error) {
 	if len(m) == 0 {
-		return true
+		return true, nil
 	}
 
 	vars := r.Context().Value(VarsCtxKey).(map[string]any)
@@ -200,11 +206,11 @@ func (m VarsMatcher) Match(r *http.Request) bool {
 				varStr = fmt.Sprintf("%v", vv)
 			}
 			if varStr == matcherValExpanded {
-				return true
+				return true, nil
 			}
 		}
 	}
-	return false
+	return false, nil
 }
 
 // CELLibrary produces options that expose this matcher for use in CEL
@@ -219,7 +225,7 @@ func (VarsMatcher) CELLibrary(_ caddy.Context) (cel.Library, error) {
 		"vars",
 		"vars_matcher_request_map",
 		[]*cel.Type{CELTypeJSON},
-		func(data ref.Val) (RequestMatcher, error) {
+		func(data ref.Val) (RequestMatcherWithError, error) {
 			mapStrListStr, err := CELValueToMapStrList(data)
 			if err != nil {
 				return nil, err
@@ -294,6 +300,12 @@ func (m MatchVarsRE) Provision(ctx caddy.Context) error {
 
 // Match returns true if r matches m.
 func (m MatchVarsRE) Match(r *http.Request) bool {
+	match, _ := m.MatchWithError(r)
+	return match
+}
+
+// MatchWithError returns true if r matches m.
+func (m MatchVarsRE) MatchWithError(r *http.Request) (bool, error) {
 	vars := r.Context().Value(VarsCtxKey).(map[string]any)
 	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 	for key, val := range m {
@@ -322,10 +334,10 @@ func (m MatchVarsRE) Match(r *http.Request) bool {
 
 		valExpanded := repl.ReplaceAll(varStr, "")
 		if match := val.Match(valExpanded, repl); match {
-			return match
+			return match, nil
 		}
 	}
-	return false
+	return false, nil
 }
 
 // CELLibrary produces options that expose this matcher for use in CEL
@@ -340,7 +352,7 @@ func (MatchVarsRE) CELLibrary(ctx caddy.Context) (cel.Library, error) {
 		"vars_regexp",
 		"vars_regexp_request_string_string",
 		[]*cel.Type{cel.StringType, cel.StringType},
-		func(data ref.Val) (RequestMatcher, error) {
+		func(data ref.Val) (RequestMatcherWithError, error) {
 			refStringList := reflect.TypeOf([]string{})
 			params, err := data.ConvertToNative(refStringList)
 			if err != nil {
@@ -363,7 +375,7 @@ func (MatchVarsRE) CELLibrary(ctx caddy.Context) (cel.Library, error) {
 		"vars_regexp",
 		"vars_regexp_request_string_string_string",
 		[]*cel.Type{cel.StringType, cel.StringType, cel.StringType},
-		func(data ref.Val) (RequestMatcher, error) {
+		func(data ref.Val) (RequestMatcherWithError, error) {
 			refStringList := reflect.TypeOf([]string{})
 			params, err := data.ConvertToNative(refStringList)
 			if err != nil {
@@ -435,8 +447,10 @@ func SetVar(ctx context.Context, key string, value any) {
 
 // Interface guards
 var (
-	_ MiddlewareHandler     = (*VarsMiddleware)(nil)
-	_ caddyfile.Unmarshaler = (*VarsMiddleware)(nil)
-	_ RequestMatcher        = (*VarsMatcher)(nil)
-	_ caddyfile.Unmarshaler = (*VarsMatcher)(nil)
+	_ MiddlewareHandler       = (*VarsMiddleware)(nil)
+	_ caddyfile.Unmarshaler   = (*VarsMiddleware)(nil)
+	_ RequestMatcherWithError = (*VarsMatcher)(nil)
+	_ caddyfile.Unmarshaler   = (*VarsMatcher)(nil)
+	_ RequestMatcherWithError = (*MatchVarsRE)(nil)
+	_ caddyfile.Unmarshaler   = (*MatchVarsRE)(nil)
 )