chore: Use slices package where possible (#6585)

* chore: Use slices package where possible

* More, mostly using ContainsFunc

* Even more slice operations

21 files changed, 141 insertions, 267 deletions

diff --git a/admin.go b/admin.go
index ef78254ee..e78adeec9 100644
--- a/admin.go
+++ b/admin.go
@@ -34,6 +34,7 @@ import (
 	"os"
 	"path"
 	"regexp"
+	"slices"
 	"strconv"
 	"strings"
 	"sync"
@@ -675,13 +676,7 @@ func (remote RemoteAdmin) enforceAccessControls(r *http.Request) error {
 					// key recognized; make sure its HTTP request is permitted
 					for _, accessPerm := range adminAccess.Permissions {
 						// verify method
-						methodFound := accessPerm.Methods == nil
-						for _, method := range accessPerm.Methods {
-							if method == r.Method {
-								methodFound = true
-								break
-							}
-						}
+						methodFound := accessPerm.Methods == nil || slices.Contains(accessPerm.Methods, r.Method)
 						if !methodFound {
 							return APIError{
 								HTTPStatus: http.StatusForbidden,
@@ -877,13 +872,9 @@ func (h adminHandler) handleError(w http.ResponseWriter, r *http.Request, err er
 // a trustworthy/expected value. This helps to mitigate DNS
 // rebinding attacks.
 func (h adminHandler) checkHost(r *http.Request) error {
-	var allowed bool
-	for _, allowedOrigin := range h.allowedOrigins {
-		if r.Host == allowedOrigin.Host {
-			allowed = true
-			break
-		}
-	}
+	allowed := slices.ContainsFunc(h.allowedOrigins, func(u *url.URL) bool {
+		return r.Host == u.Host
+	})
 	if !allowed {
 		return APIError{
 			HTTPStatus: http.StatusForbidden,
diff --git a/caddyconfig/caddyfile/importgraph.go b/caddyconfig/caddyfile/importgraph.go
index d5037fe62..ca859299d 100644
--- a/caddyconfig/caddyfile/importgraph.go
+++ b/caddyconfig/caddyfile/importgraph.go
@@ -16,6 +16,7 @@ package caddyfile
 
 import (
 	"fmt"
+	"slices"
 )
 
 type adjacency map[string][]string
@@ -91,12 +92,7 @@ func (i *importGraph) areConnected(from, to string) bool {
 	if !ok {
 		return false
 	}
-	for _, v := range al {
-		if v == to {
-			return true
-		}
-	}
-	return false
+	return slices.Contains(al, to)
 }
 
 func (i *importGraph) willCycle(from, to string) bool {
diff --git a/caddyconfig/httpcaddyfile/directives.go b/caddyconfig/httpcaddyfile/directives.go
index 6972bb674..19ef4bc0e 100644
--- a/caddyconfig/httpcaddyfile/directives.go
+++ b/caddyconfig/httpcaddyfile/directives.go
@@ -17,6 +17,7 @@ package httpcaddyfile
 import (
 	"encoding/json"
 	"net"
+	"slices"
 	"sort"
 	"strconv"
 	"strings"
@@ -100,17 +101,6 @@ var defaultDirectiveOrder = []string{
 // plugins or by the user via the "order" global option.
 var directiveOrder = defaultDirectiveOrder
 
-// directiveIsOrdered returns true if dir is
-// a known, ordered (sorted) directive.
-func directiveIsOrdered(dir string) bool {
-	for _, d := range directiveOrder {
-		if d == dir {
-			return true
-		}
-	}
-	return false
-}
-
 // RegisterDirective registers a unique directive dir with an
 // associated unmarshaling (setup) function. When directive dir
 // is encountered in a Caddyfile, setupFunc will be called to
@@ -161,7 +151,7 @@ func RegisterHandlerDirective(dir string, setupFunc UnmarshalHandlerFunc) {
 // EXPERIMENTAL: This API may change or be removed.
 func RegisterDirectiveOrder(dir string, position Positional, standardDir string) {
 	// check if directive was already ordered
-	if directiveIsOrdered(dir) {
+	if slices.Contains(directiveOrder, dir) {
 		panic("directive '" + dir + "' already ordered")
 	}
 
@@ -172,12 +162,7 @@ func RegisterDirectiveOrder(dir string, position Positional, standardDir string)
 	// check if directive exists in standard distribution, since
 	// we can't allow plugins to depend on one another; we can't
 	// guarantee the order that plugins are loaded in.
-	foundStandardDir := false
-	for _, d := range defaultDirectiveOrder {
-		if d == standardDir {
-			foundStandardDir = true
-		}
-	}
+	foundStandardDir := slices.Contains(defaultDirectiveOrder, standardDir)
 	if !foundStandardDir {
 		panic("the 3rd argument '" + standardDir + "' must be a directive that exists in the standard distribution of Caddy")
 	}
@@ -603,23 +588,17 @@ func (sb serverBlock) hostsFromKeysNotHTTP(httpPort string) []string {
 // hasHostCatchAllKey returns true if sb has a key that
 // omits a host portion, i.e. it "catches all" hosts.
 func (sb serverBlock) hasHostCatchAllKey() bool {
-	for _, addr := range sb.keys {
-		if addr.Host == "" {
-			return true
-		}
-	}
-	return false
+	return slices.ContainsFunc(sb.keys, func(addr Address) bool {
+		return addr.Host == ""
+	})
 }
 
 // isAllHTTP returns true if all sb keys explicitly specify
 // the http:// scheme
 func (sb serverBlock) isAllHTTP() bool {
-	for _, addr := range sb.keys {
-		if addr.Scheme != "http" {
-			return false
-		}
-	}
-	return true
+	return !slices.ContainsFunc(sb.keys, func(addr Address) bool {
+		return addr.Scheme != "http"
+	})
 }
 
 // Positional are the supported modes for ordering directives.
diff --git a/caddyconfig/httpcaddyfile/httptype.go b/caddyconfig/httpcaddyfile/httptype.go
index a8a2ae5b3..c858ee564 100644
--- a/caddyconfig/httpcaddyfile/httptype.go
+++ b/caddyconfig/httpcaddyfile/httptype.go
@@ -536,7 +536,7 @@ func (st *ServerType) serversFromPairings(
 					if k == j {
 						continue
 					}
-					if sliceContains(sblock2.block.GetKeysText(), key) {
+					if slices.Contains(sblock2.block.GetKeysText(), key) {
 						return nil, fmt.Errorf("ambiguous site definition: %s", key)
 					}
 				}
@@ -720,7 +720,7 @@ func (st *ServerType) serversFromPairings(
 						if srv.AutoHTTPS == nil {
 							srv.AutoHTTPS = new(caddyhttp.AutoHTTPSConfig)
 						}
-						if !sliceContains(srv.AutoHTTPS.Skip, addr.Host) {
+						if !slices.Contains(srv.AutoHTTPS.Skip, addr.Host) {
 							srv.AutoHTTPS.Skip = append(srv.AutoHTTPS.Skip, addr.Host)
 						}
 					}
@@ -734,7 +734,7 @@ func (st *ServerType) serversFromPairings(
 				// https://caddy.community/t/making-sense-of-auto-https-and-why-disabling-it-still-serves-https-instead-of-http/9761
 				createdTLSConnPolicies, ok := sblock.pile["tls.connection_policy"]
 				hasTLSEnabled := (ok && len(createdTLSConnPolicies) > 0) ||
-					(addr.Host != "" && srv.AutoHTTPS != nil && !sliceContains(srv.AutoHTTPS.Skip, addr.Host))
+					(addr.Host != "" && srv.AutoHTTPS != nil && !slices.Contains(srv.AutoHTTPS.Skip, addr.Host))
 
 				// we'll need to remember if the address qualifies for auto-HTTPS, so we
 				// can add a TLS conn policy if necessary
@@ -1061,7 +1061,7 @@ func consolidateConnPolicies(cps caddytls.ConnectionPolicies) (caddytls.Connecti
 				} else if cps[i].CertSelection != nil && cps[j].CertSelection != nil {
 					// if both have one, then combine AnyTag
 					for _, tag := range cps[j].CertSelection.AnyTag {
-						if !sliceContains(cps[i].CertSelection.AnyTag, tag) {
+						if !slices.Contains(cps[i].CertSelection.AnyTag, tag) {
 							cps[i].CertSelection.AnyTag = append(cps[i].CertSelection.AnyTag, tag)
 						}
 					}
@@ -1144,7 +1144,7 @@ func appendSubrouteToRouteList(routeList caddyhttp.RouteList,
 func buildSubroute(routes []ConfigValue, groupCounter counter, needsSorting bool) (*caddyhttp.Subroute, error) {
 	if needsSorting {
 		for _, val := range routes {
-			if !directiveIsOrdered(val.directive) {
+			if !slices.Contains(directiveOrder, val.directive) {
 				return nil, fmt.Errorf("directive '%s' is not an ordered HTTP handler, so it cannot be used here - try placing within a route block or using the order global option", val.directive)
 			}
 		}
@@ -1354,17 +1354,8 @@ func (st *ServerType) compileEncodedMatcherSets(sblock serverBlock) ([]caddy.Mod
 
 		// add this server block's keys to the matcher
 		// pair if it doesn't already exist
-		if addr.Host != "" {
-			var found bool
-			for _, h := range chosenMatcherPair.hostm {
-				if h == addr.Host {
-					found = true
-					break
-				}
-			}
-			if !found {
-				chosenMatcherPair.hostm = append(chosenMatcherPair.hostm, addr.Host)
-			}
+		if addr.Host != "" && !slices.Contains(chosenMatcherPair.hostm, addr.Host) {
+			chosenMatcherPair.hostm = append(chosenMatcherPair.hostm, addr.Host)
 		}
 	}
 
@@ -1540,16 +1531,6 @@ func tryDuration(val any, warnings *[]caddyconfig.Warning) caddy.Duration {
 	return durationVal
 }
 
-// sliceContains returns true if needle is in haystack.
-func sliceContains(haystack []string, needle string) bool {
-	for _, s := range haystack {
-		if s == needle {
-			return true
-		}
-	}
-	return false
-}
-
 // listenersUseAnyPortOtherThan returns true if there are any
 // listeners in addresses that use a port which is not otherPort.
 // Mostly borrowed from unexported method in caddyhttp package.
diff --git a/caddyconfig/httpcaddyfile/options.go b/caddyconfig/httpcaddyfile/options.go
index db9be52ca..53687d32a 100644
--- a/caddyconfig/httpcaddyfile/options.go
+++ b/caddyconfig/httpcaddyfile/options.go
@@ -15,6 +15,7 @@
 package httpcaddyfile
 
 import (
+	"slices"
 	"strconv"
 
 	"github.com/caddyserver/certmagic"
@@ -110,17 +111,12 @@ func parseOptOrder(d *caddyfile.Dispenser, _ any) (any, error) {
 	}
 	pos := Positional(d.Val())
 
-	newOrder := directiveOrder
+	// if directive already had an order, drop it
+	newOrder := slices.DeleteFunc(directiveOrder, func(d string) bool {
+		return d == dirName
+	})
 
-	// if directive exists, first remove it
-	for i, d := range newOrder {
-		if d == dirName {
-			newOrder = append(newOrder[:i], newOrder[i+1:]...)
-			break
-		}
-	}
-
-	// act on the positional
+	// act on the positional; if it's First or Last, we're done right away
 	switch pos {
 	case First:
 		newOrder = append([]string{dirName}, newOrder...)
@@ -129,6 +125,7 @@ func parseOptOrder(d *caddyfile.Dispenser, _ any) (any, error) {
 		}
 		directiveOrder = newOrder
 		return newOrder, nil
+
 	case Last:
 		newOrder = append(newOrder, dirName)
 		if d.NextArg() {
@@ -136,8 +133,11 @@ func parseOptOrder(d *caddyfile.Dispenser, _ any) (any, error) {
 		}
 		directiveOrder = newOrder
 		return newOrder, nil
+
+	// if it's Before or After, continue
 	case Before:
 	case After:
+
 	default:
 		return nil, d.Errf("unknown positional '%s'", pos)
 	}
@@ -151,17 +151,17 @@ func parseOptOrder(d *caddyfile.Dispenser, _ any) (any, error) {
 		return nil, d.ArgErr()
 	}
 
-	// insert directive into proper position
-	for i, d := range newOrder {
-		if d == otherDir {
-			if pos == Before {
-				newOrder = append(newOrder[:i], append([]string{dirName}, newOrder[i:]...)...)
-			} else if pos == After {
-				newOrder = append(newOrder[:i+1], append([]string{dirName}, newOrder[i+1:]...)...)
-			}
-			break
-		}
+	// get the position of the target directive
+	targetIndex := slices.Index(newOrder, otherDir)
+	if targetIndex == -1 {
+		return nil, d.Errf("directive '%s' not found", otherDir)
+	}
+	// if we're inserting after, we need to increment the index to go after
+	if pos == After {
+		targetIndex++
 	}
+	// insert the directive into the new order
+	newOrder = slices.Insert(newOrder, targetIndex, dirName)
 
 	directiveOrder = newOrder
 
diff --git a/caddyconfig/httpcaddyfile/serveroptions.go b/caddyconfig/httpcaddyfile/serveroptions.go
index 4246cd7dc..7087cdba5 100644
--- a/caddyconfig/httpcaddyfile/serveroptions.go
+++ b/caddyconfig/httpcaddyfile/serveroptions.go
@@ -17,6 +17,7 @@ package httpcaddyfile
 import (
 	"encoding/json"
 	"fmt"
+	"slices"
 
 	"github.com/dustin/go-humanize"
 
@@ -180,7 +181,7 @@ func unmarshalCaddyfileServerOptions(d *caddyfile.Dispenser) (any, error) {
 				if proto != "h1" && proto != "h2" && proto != "h2c" && proto != "h3" {
 					return nil, d.Errf("unknown protocol '%s': expected h1, h2, h2c, or h3", proto)
 				}
-				if sliceContains(serverOpts.Protocols, proto) {
+				if slices.Contains(serverOpts.Protocols, proto) {
 					return nil, d.Errf("protocol %s specified more than once", proto)
 				}
 				serverOpts.Protocols = append(serverOpts.Protocols, proto)
@@ -229,7 +230,7 @@ func unmarshalCaddyfileServerOptions(d *caddyfile.Dispenser) (any, error) {
 		case "client_ip_headers":
 			headers := d.RemainingArgs()
 			for _, header := range headers {
-				if sliceContains(serverOpts.ClientIPHeaders, header) {
+				if slices.Contains(serverOpts.ClientIPHeaders, header) {
 					return nil, d.Errf("client IP header %s specified more than once", header)
 				}
 				serverOpts.ClientIPHeaders = append(serverOpts.ClientIPHeaders, header)
@@ -288,24 +289,15 @@ func applyServerOptions(
 
 	for key, server := range servers {
 		// find the options that apply to this server
-		opts := func() *serverOptions {
-			for _, entry := range serverOpts {
-				if entry.ListenerAddress == "" {
-					return &entry
-				}
-				for _, listener := range server.Listen {
-					if entry.ListenerAddress == listener {
-						return &entry
-					}
-				}
-			}
-			return nil
-		}()
+		optsIndex := slices.IndexFunc(serverOpts, func(s serverOptions) bool {
+			return s.ListenerAddress == "" || slices.Contains(server.Listen, s.ListenerAddress)
+		})
 
 		// if none apply, then move to the next server
-		if opts == nil {
+		if optsIndex == -1 {
 			continue
 		}
+		opts := serverOpts[optsIndex]
 
 		// set all the options
 		server.ListenerWrappersRaw = opts.ListenerWrappersRaw
diff --git a/caddyconfig/httpcaddyfile/tlsapp.go b/caddyconfig/httpcaddyfile/tlsapp.go
index f69e2c54a..157a3113e 100644
--- a/caddyconfig/httpcaddyfile/tlsapp.go
+++ b/caddyconfig/httpcaddyfile/tlsapp.go
@@ -19,6 +19,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"reflect"
+	"slices"
 	"sort"
 	"strconv"
 	"strings"
@@ -57,19 +58,20 @@ func (st ServerType) buildTLSApp(
 		for _, pair := range pairings {
 			for _, sb := range pair.serverBlocks {
 				for _, addr := range sb.keys {
-					if addr.Host == "" {
-						// this server block has a hostless key, now
-						// go through and add all the hosts to the set
-						for _, otherAddr := range sb.keys {
-							if otherAddr.Original == addr.Original {
-								continue
-							}
-							if otherAddr.Host != "" && otherAddr.Scheme != "http" && otherAddr.Port != httpPort {
-								httpsHostsSharedWithHostlessKey[otherAddr.Host] = struct{}{}
-							}
+					if addr.Host != "" {
+						continue
+					}
+					// this server block has a hostless key, now
+					// go through and add all the hosts to the set
+					for _, otherAddr := range sb.keys {
+						if otherAddr.Original == addr.Original {
+							continue
+						}
+						if otherAddr.Host != "" && otherAddr.Scheme != "http" && otherAddr.Port != httpPort {
+							httpsHostsSharedWithHostlessKey[otherAddr.Host] = struct{}{}
 						}
-						break
 					}
+					break
 				}
 			}
 		}
@@ -465,7 +467,7 @@ func fillInGlobalACMEDefaults(issuer certmagic.Issuer, options map[string]any) e
 	if globalACMECA != nil && acmeIssuer.CA == "" {
 		acmeIssuer.CA = globalACMECA.(string)
 	}
-	if globalACMECARoot != nil && !sliceContains(acmeIssuer.TrustedRootsPEMFiles, globalACMECARoot.(string)) {
+	if globalACMECARoot != nil && !slices.Contains(acmeIssuer.TrustedRootsPEMFiles, globalACMECARoot.(string)) {
 		acmeIssuer.TrustedRootsPEMFiles = append(acmeIssuer.TrustedRootsPEMFiles, globalACMECARoot.(string))
 	}
 	if globalACMEDNS != nil && (acmeIssuer.Challenges == nil || acmeIssuer.Challenges.DNS == nil) {
@@ -580,7 +582,7 @@ func consolidateAutomationPolicies(aps []*caddytls.AutomationPolicy) []*caddytls
 			if !automationPolicyHasAllPublicNames(aps[i]) {
 				// if this automation policy has internal names, we might as well remove it
 				// so auto-https can implicitly use the internal issuer
-				aps = append(aps[:i], aps[i+1:]...)
+				aps = slices.Delete(aps, i, i+1)
 				i--
 			}
 		}
@@ -597,7 +599,7 @@ outer:
 		for j := i + 1; j < len(aps); j++ {
 			// if they're exactly equal in every way, just keep one of them
 			if reflect.DeepEqual(aps[i], aps[j]) {
-				aps = append(aps[:j], aps[j+1:]...)
+				aps = slices.Delete(aps, j, j+1)
 				// must re-evaluate current i against next j; can't skip it!
 				// even if i decrements to -1, will be incremented to 0 immediately
 				i--
@@ -627,18 +629,18 @@ outer:
 					// cause example.com to be served by the less specific policy for
 					// '*.com', which might be different (yes we've seen this happen)
 					if automationPolicyShadows(i, aps) >= j {
-						aps = append(aps[:i], aps[i+1:]...)
+						aps = slices.Delete(aps, i, i+1)
 						i--
 						continue outer
 					}
 				} else {
 					// avoid repeated subjects
 					for _, subj := range aps[j].SubjectsRaw {
-						if !sliceContains(aps[i].SubjectsRaw, subj) {
+						if !slices.Contains(aps[i].SubjectsRaw, subj) {
 							aps[i].SubjectsRaw = append(aps[i].SubjectsRaw, subj)
 						}
 					}
-					aps = append(aps[:j], aps[j+1:]...)
+					aps = slices.Delete(aps, j, j+1)
 					j--
 				}
 			}
@@ -658,13 +660,9 @@ func automationPolicyIsSubset(a, b *caddytls.AutomationPolicy) bool {
 		return false
 	}
 	for _, aSubj := range a.SubjectsRaw {
-		var inSuperset bool
-		for _, bSubj := range b.SubjectsRaw {
-			if certmagic.MatchWildcard(aSubj, bSubj) {
-				inSuperset = true
-				break
-			}
-		}
+		inSuperset := slices.ContainsFunc(b.SubjectsRaw, func(bSubj string) bool {
+			return certmagic.MatchWildcard(aSubj, bSubj)
+		})
 		if !inSuperset {
 			return false
 		}
@@ -709,12 +707,9 @@ func subjectQualifiesForPublicCert(ap *caddytls.AutomationPolicy, subj string) b
 // automationPolicyHasAllPublicNames returns true if all the names on the policy
 // do NOT qualify for public certs OR are tailscale domains.
 func automationPolicyHasAllPublicNames(ap *caddytls.AutomationPolicy) bool {
-	for _, subj := range ap.SubjectsRaw {
-		if !subjectQualifiesForPublicCert(ap, subj) || isTailscaleDomain(subj) {
-			return false
-		}
-	}
-	return true
+	return !slices.ContainsFunc(ap.SubjectsRaw, func(i string) bool {
+		return !subjectQualifiesForPublicCert(ap, i) || isTailscaleDomain(i)
+	})
 }
 
 func isTailscaleDomain(name string) bool {
diff --git a/modules/caddyevents/app.go b/modules/caddyevents/app.go
index fe76a6757..2e4a6f2c0 100644
--- a/modules/caddyevents/app.go
+++ b/modules/caddyevents/app.go
@@ -124,18 +124,19 @@ func (app *App) Provision(ctx caddy.Context) error {
 	app.subscriptions = make(map[string]map[caddy.ModuleID][]Handler)
 
 	for _, sub := range app.Subscriptions {
-		if sub.HandlersRaw != nil {
-			handlersIface, err := ctx.LoadModule(sub, "HandlersRaw")
-			if err != nil {
-				return fmt.Errorf("loading event subscriber modules: %v", err)
-			}
-			for _, h := range handlersIface.([]any) {
-				sub.Handlers = append(sub.Handlers, h.(Handler))
-			}
-			if len(sub.Handlers) == 0 {
-				// pointless to bind without any handlers
-				return fmt.Errorf("no handlers defined")
-			}
+		if sub.HandlersRaw == nil {
+			continue
+		}
+		handlersIface, err := ctx.LoadModule(sub, "HandlersRaw")
+		if err != nil {
+			return fmt.Errorf("loading event subscriber modules: %v", err)
+		}
+		for _, h := range handlersIface.([]any) {
+			sub.Handlers = append(sub.Handlers, h.(Handler))
+		}
+		if len(sub.Handlers) == 0 {
+			// pointless to bind without any handlers
+			return fmt.Errorf("no handlers defined")
 		}
 	}
 
diff --git a/modules/caddyhttp/autohttps.go b/modules/caddyhttp/autohttps.go
index 263cd14c7..ea5a07b3c 100644
--- a/modules/caddyhttp/autohttps.go
+++ b/modules/caddyhttp/autohttps.go
@@ -17,6 +17,7 @@ package caddyhttp
 import (
 	"fmt"
 	"net/http"
+	"slices"
 	"strconv"
 	"strings"
 
@@ -66,17 +67,6 @@ type AutoHTTPSConfig struct {
 	IgnoreLoadedCerts bool `json:"ignore_loaded_certificates,omitempty"`
 }
 
-// Skipped returns true if name is in skipSlice, which
-// should be either the Skip or SkipCerts field on ahc.
-func (ahc AutoHTTPSConfig) Skipped(name string, skipSlice []string) bool {
-	for _, n := range skipSlice {
-		if name == n {
-			return true
-		}
-	}
-	return false
-}
-
 // automaticHTTPSPhase1 provisions all route matchers, determines
 // which domain names found in the routes qualify for automatic
 // HTTPS, and sets up HTTP->HTTPS redirects. This phase must occur
@@ -158,7 +148,7 @@ func (app *App) automaticHTTPSPhase1(ctx caddy.Context, repl *caddy.Replacer) er
 								return fmt.Errorf("%s: route %d, matcher set %d, matcher %d, host matcher %d: %v",
 									srvName, routeIdx, matcherSetIdx, matcherIdx, hostMatcherIdx, err)
 							}
-							if !srv.AutoHTTPS.Skipped(d, srv.AutoHTTPS.Skip) {
+							if !slices.Contains(srv.AutoHTTPS.Skip, d) {
 								serverDomainSet[d] = struct{}{}
 							}
 						}
@@ -193,7 +183,7 @@ func (app *App) automaticHTTPSPhase1(ctx caddy.Context, repl *caddy.Replacer) er
 		} else {
 			for d := range serverDomainSet {
 				if certmagic.SubjectQualifiesForCert(d) &&
-					!srv.AutoHTTPS.Skipped(d, srv.AutoHTTPS.SkipCerts) {
+					!slices.Contains(srv.AutoHTTPS.SkipCerts, d) {
 					// if a certificate for this name is already loaded,
 					// don't obtain another one for it, unless we are
 					// supposed to ignore loaded certificates
diff --git a/modules/caddyhttp/encode/encode.go b/modules/caddyhttp/encode/encode.go
index 00e507277..f0d56a90d 100644
--- a/modules/caddyhttp/encode/encode.go
+++ b/modules/caddyhttp/encode/encode.go
@@ -24,6 +24,7 @@ import (
 	"io"
 	"math"
 	"net/http"
+	"slices"
 	"sort"
 	"strconv"
 	"strings"
@@ -441,12 +442,9 @@ func AcceptedEncodings(r *http.Request, preferredOrder []string) []string {
 		}
 
 		// set server preference
-		prefOrder := -1
-		for i, p := range preferredOrder {
-			if encName == p {
-				prefOrder = len(preferredOrder) - i
-				break
-			}
+		prefOrder := slices.Index(preferredOrder, encName)
+		if prefOrder > -1 {
+			prefOrder = len(preferredOrder) - prefOrder
 		}
 
 		prefs = append(prefs, encodingPreference{
diff --git a/modules/caddyhttp/fileserver/browsetplcontext.go b/modules/caddyhttp/fileserver/browsetplcontext.go
index 37e1cc3dd..8e5d138f1 100644
--- a/modules/caddyhttp/fileserver/browsetplcontext.go
+++ b/modules/caddyhttp/fileserver/browsetplcontext.go
@@ -21,6 +21,7 @@ import (
 	"os"
 	"path"
 	"path/filepath"
+	"slices"
 	"sort"
 	"strconv"
 	"strings"
@@ -281,12 +282,9 @@ type fileInfo struct {
 
 // HasExt returns true if the filename has any of the given suffixes, case-insensitive.
 func (fi fileInfo) HasExt(exts ...string) bool {
-	for _, ext := range exts {
-		if strings.HasSuffix(strings.ToLower(fi.Name), strings.ToLower(ext)) {
-			return true
-		}
-	}
-	return false
+	return slices.ContainsFunc(exts, func(ext string) bool {
+		return strings.HasSuffix(strings.ToLower(fi.Name), strings.ToLower(ext))
+	})
 }
 
 // HumanSize returns the size of the file as a
diff --git a/modules/caddyhttp/headers/headers.go b/modules/caddyhttp/headers/headers.go
index bdb185f46..a3279d913 100644
--- a/modules/caddyhttp/headers/headers.go
+++ b/modules/caddyhttp/headers/headers.go
@@ -135,13 +135,14 @@ type HeaderOps struct {
 func (ops *HeaderOps) Provision(_ caddy.Context) error {
 	for fieldName, replacements := range ops.Replace {
 		for i, r := range replacements {
-			if r.SearchRegexp != "" {
-				re, err := regexp.Compile(r.SearchRegexp)
-				if err != nil {
-					return fmt.Errorf("replacement %d for header field '%s': %v", i, fieldName, err)
-				}
-				replacements[i].re = re
+			if r.SearchRegexp == "" {
+				continue
+			}
+			re, err := regexp.Compile(r.SearchRegexp)
+			if err != nil {
+				return fmt.Errorf("replacement %d for header field '%s': %v", i, fieldName, err)
 			}
+			replacements[i].re = re
 		}
 	}
 	return nil
diff --git a/modules/caddyhttp/map/map.go b/modules/caddyhttp/map/map.go
index 336f25723..d02085e76 100644
--- a/modules/caddyhttp/map/map.go
+++ b/modules/caddyhttp/map/map.go
@@ -18,6 +18,7 @@ import (
 	"fmt"
 	"net/http"
 	"regexp"
+	"slices"
 	"strings"
 
 	"github.com/caddyserver/caddy/v2"
@@ -126,7 +127,7 @@ func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhtt
 	// defer work until a variable is actually evaluated by using replacer's Map callback
 	repl.Map(func(key string) (any, bool) {
 		// return early if the variable is not even a configured destination
-		destIdx := h.destinationIndex(key)
+		destIdx := slices.Index(h.Destinations, key)
 		if destIdx < 0 {
 			return nil, false
 		}
@@ -170,17 +171,6 @@ func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhtt
 	return next.ServeHTTP(w, r)
 }
 
-// destinationIndex returns the positional index of the destination
-// is name is a known destination; otherwise it returns -1.
-func (h Handler) destinationIndex(name string) int {
-	for i, dest := range h.Destinations {
-		if dest == name {
-			return i
-		}
-	}
-	return -1
-}
-
 // Mapping describes a mapping from input to outputs.
 type Mapping struct {
 	// The input value to match. Must be distinct from other mappings.
diff --git a/modules/caddyhttp/matchers.go b/modules/caddyhttp/matchers.go
index b7952ab69..a0bc6d63a 100644
--- a/modules/caddyhttp/matchers.go
+++ b/modules/caddyhttp/matchers.go
@@ -764,12 +764,7 @@ func (m *MatchMethod) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 
 // Match returns true if r matches m.
 func (m MatchMethod) Match(r *http.Request) bool {
-	for _, method := range m {
-		if r.Method == method {
-			return true
-		}
-	}
-	return false
+	return slices.Contains(m, r.Method)
 }
 
 // CELLibrary produces options that expose this matcher for use in CEL
diff --git a/modules/caddyhttp/reverseproxy/healthchecks.go b/modules/caddyhttp/reverseproxy/healthchecks.go
index 179805f20..319cc9248 100644
--- a/modules/caddyhttp/reverseproxy/healthchecks.go
+++ b/modules/caddyhttp/reverseproxy/healthchecks.go
@@ -23,6 +23,7 @@ import (
 	"net/url"
 	"regexp"
 	"runtime/debug"
+	"slices"
 	"strconv"
 	"strings"
 	"time"
@@ -397,12 +398,8 @@ func (h *Handler) doActiveHealthCheck(dialInfo DialInfo, hostAddr string, networ
 		u.Scheme = "https"
 
 		// if the port is in the except list, flip back to HTTP
-		if ht, ok := h.Transport.(*HTTPTransport); ok {
-			for _, exceptPort := range ht.TLS.ExceptPorts {
-				if exceptPort == port {
-					u.Scheme = "http"
-				}
-			}
+		if ht, ok := h.Transport.(*HTTPTransport); ok && slices.Contains(ht.TLS.ExceptPorts, port) {
+			u.Scheme = "http"
 		}
 	}
 
diff --git a/modules/caddyhttp/reverseproxy/httptransport.go b/modules/caddyhttp/reverseproxy/httptransport.go
index 144960cf9..bc8233788 100644
--- a/modules/caddyhttp/reverseproxy/httptransport.go
+++ b/modules/caddyhttp/reverseproxy/httptransport.go
@@ -27,6 +27,7 @@ import (
 	"net/url"
 	"os"
 	"reflect"
+	"slices"
 	"strings"
 	"time"
 
@@ -381,7 +382,7 @@ func (h *HTTPTransport) NewTransport(caddyCtx caddy.Context) (*http.Transport, e
 		rt.DisableCompression = !*h.Compression
 	}
 
-	if sliceContains(h.Versions, "2") {
+	if slices.Contains(h.Versions, "2") {
 		if err := http2.ConfigureTransport(rt); err != nil {
 			return nil, err
 		}
@@ -400,13 +401,13 @@ func (h *HTTPTransport) NewTransport(caddyCtx caddy.Context) (*http.Transport, e
 				return nil, fmt.Errorf("making TLS client config for HTTP/3 transport: %v", err)
 			}
 		}
-	} else if len(h.Versions) > 1 && sliceContains(h.Versions, "3") {
+	} else if len(h.Versions) > 1 && slices.Contains(h.Versions, "3") {
 		return nil, fmt.Errorf("if HTTP/3 is enabled to the upstream, no other HTTP versions are supported")
 	}
 
 	// if h2c is enabled, configure its transport (std lib http.Transport
 	// does not "HTTP/2 over cleartext TCP")
-	if sliceContains(h.Versions, "h2c") {
+	if slices.Contains(h.Versions, "h2c") {
 		// crafting our own http2.Transport doesn't allow us to utilize
 		// most of the customizations/preferences on the http.Transport,
 		// because, for some reason, only http2.ConfigureTransport()
@@ -783,16 +784,6 @@ func decodeBase64DERCert(certStr string) (*x509.Certificate, error) {
 	return x509.ParseCertificate(derBytes)
 }
 
-// sliceContains returns true if needle is in haystack.
-func sliceContains(haystack []string, needle string) bool {
-	for _, s := range haystack {
-		if s == needle {
-			return true
-		}
-	}
-	return false
-}
-
 // Interface guards
 var (
 	_ caddy.Provisioner  = (*HTTPTransport)(nil)
diff --git a/modules/caddyhttp/server.go b/modules/caddyhttp/server.go
index 54b1c3b34..ece3f1cd2 100644
--- a/modules/caddyhttp/server.go
+++ b/modules/caddyhttp/server.go
@@ -25,6 +25,7 @@ import (
 	"net/netip"
 	"net/url"
 	"runtime"
+	"slices"
 	"strings"
 	"sync"
 	"time"
@@ -543,12 +544,9 @@ func (s *Server) hasListenerAddress(fullAddr string) bool {
 }
 
 func (s *Server) hasTLSClientAuth() bool {
-	for _, cp := range s.TLSConnPolicies {
-		if cp.ClientAuthentication != nil && cp.ClientAuthentication.Active() {
-			return true
-		}
-	}
-	return false
+	return slices.ContainsFunc(s.TLSConnPolicies, func(cp *caddytls.ConnectionPolicy) bool {
+		return cp.ClientAuthentication != nil && cp.ClientAuthentication.Active()
+	})
 }
 
 // findLastRouteWithHostMatcher returns the index of the last route
@@ -849,12 +847,7 @@ func (s *Server) logRequest(
 
 // protocol returns true if the protocol proto is configured/enabled.
 func (s *Server) protocol(proto string) bool {
-	for _, p := range s.Protocols {
-		if p == proto {
-			return true
-		}
-	}
-	return false
+	return slices.Contains(s.Protocols, proto)
 }
 
 // Listeners returns the server's listeners. These are active listeners,
@@ -959,12 +952,9 @@ func determineTrustedProxy(r *http.Request, s *Server) (bool, string) {
 // isTrustedClientIP returns true if the given IP address is
 // in the list of trusted IP ranges.
 func isTrustedClientIP(ipAddr netip.Addr, trusted []netip.Prefix) bool {
-	for _, ipRange := range trusted {
-		if ipRange.Contains(ipAddr) {
-			return true
-		}
-	}
-	return false
+	return slices.ContainsFunc(trusted, func(prefix netip.Prefix) bool {
+		return prefix.Contains(ipAddr)
+	})
 }
 
 // trustedRealClientIP finds the client IP from the request assuming it is
diff --git a/modules/caddyhttp/templates/frontmatter.go b/modules/caddyhttp/templates/frontmatter.go
index 3f7bd0cc4..fb62a4184 100644
--- a/modules/caddyhttp/templates/frontmatter.go
+++ b/modules/caddyhttp/templates/frontmatter.go
@@ -40,6 +40,7 @@ func extractFrontMatter(input string) (map[string]any, string, error) {
 		if firstLine == fmType.FenceOpen {
 			closingFence = fmType.FenceClose
 			fmParser = fmType.ParseFunc
+			break
 		}
 	}
 
diff --git a/modules/caddytls/automation.go b/modules/caddytls/automation.go
index e2e02221d..1f1042ba0 100644
--- a/modules/caddytls/automation.go
+++ b/modules/caddytls/automation.go
@@ -21,6 +21,7 @@ import (
 	"errors"
 	"fmt"
 	"net"
+	"slices"
 	"strings"
 
 	"github.com/caddyserver/certmagic"
@@ -373,12 +374,9 @@ func (ap *AutomationPolicy) Subjects() []string {
 
 // AllInternalSubjects returns true if all the subjects on this policy are internal.
 func (ap *AutomationPolicy) AllInternalSubjects() bool {
-	for _, subj := range ap.subjects {
-		if !certmagic.SubjectIsInternal(subj) {
-			return false
-		}
-	}
-	return true
+	return !slices.ContainsFunc(ap.subjects, func(s string) bool {
+		return !certmagic.SubjectIsInternal(s)
+	})
 }
 
 func (ap *AutomationPolicy) onlyInternalIssuer() bool {
diff --git a/modules/caddytls/certselection.go b/modules/caddytls/certselection.go
index 84ca2e118..a561e3a1d 100644
--- a/modules/caddytls/certselection.go
+++ b/modules/caddytls/certselection.go
@@ -20,6 +20,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"math/big"
+	"slices"
 
 	"github.com/caddyserver/certmagic"
 
@@ -72,15 +73,9 @@ nextChoice:
 		}
 
 		if len(p.SubjectOrganization) > 0 {
-			var found bool
-			for _, subjOrg := range p.SubjectOrganization {
-				for _, org := range cert.Leaf.Subject.Organization {
-					if subjOrg == org {
-						found = true
-						break
-					}
-				}
-			}
+			found := slices.ContainsFunc(p.SubjectOrganization, func(s string) bool {
+				return slices.Contains(cert.Leaf.Subject.Organization, s)
+			})
 			if !found {
 				continue
 			}
diff --git a/modules/caddytls/matchers.go b/modules/caddytls/matchers.go
index f44b4c02a..a74d6ea80 100644
--- a/modules/caddytls/matchers.go
+++ b/modules/caddytls/matchers.go
@@ -20,6 +20,7 @@ import (
 	"net"
 	"net/netip"
 	"regexp"
+	"slices"
 	"strconv"
 	"strings"
 
@@ -321,12 +322,9 @@ func (MatchRemoteIP) parseIPRange(str string) ([]netip.Prefix, error) {
 }
 
 func (MatchRemoteIP) matches(ip netip.Addr, ranges []netip.Prefix) bool {
-	for _, ipRange := range ranges {
-		if ipRange.Contains(ip) {
-			return true
-		}
-	}
-	return false
+	return slices.ContainsFunc(ranges, func(prefix netip.Prefix) bool {
+		return prefix.Contains(ip)
+	})
 }
 
 // UnmarshalCaddyfile sets up the MatchRemoteIP from Caddyfile tokens. Syntax:
@@ -439,12 +437,9 @@ func (MatchLocalIP) parseIPRange(str string) ([]netip.Prefix, error) {
 }
 
 func (MatchLocalIP) matches(ip netip.Addr, ranges []netip.Prefix) bool {
-	for _, ipRange := range ranges {
-		if ipRange.Contains(ip) {
-			return true
-		}
-	}
-	return false
+	return slices.ContainsFunc(ranges, func(prefix netip.Prefix) bool {
+		return prefix.Contains(ip)
+	})
 }
 
 // UnmarshalCaddyfile sets up the MatchLocalIP from Caddyfile tokens. Syntax: