Implement auto_https prefer_wildcard option

caddyconfig/httpcaddyfile/httptype.go

@@ -573,6 +573,12 @@ func (st *ServerType) serversFromPairings(
 					srv.AutoHTTPS = new(caddyhttp.AutoHTTPSConfig)
 				}
 				srv.AutoHTTPS.IgnoreLoadedCerts = true
+
+			case "prefer_wildcard":
+				if srv.AutoHTTPS == nil {
+					srv.AutoHTTPS = new(caddyhttp.AutoHTTPSConfig)
+				}
+				srv.AutoHTTPS.PreferWildcard = true
 			}
 		}
 
@@ -725,6 +731,13 @@ func (st *ServerType) serversFromPairings(
 				}
 			}
 
+			wildcardHosts := []string{}
+			for _, addr := range sblock.keys {
+				if strings.HasPrefix(addr.Host, "*.") {
+					wildcardHosts = append(wildcardHosts, addr.Host[2:])
+				}
+			}
+
 			for _, addr := range sblock.keys {
 				// if server only uses HTTP port, auto-HTTPS will not apply
 				if listenersUseAnyPortOtherThan(srv.Listen, httpPort) {
@@ -740,6 +753,18 @@ func (st *ServerType) serversFromPairings(
 					}
 				}
 
+				// If prefer wildcard is enabled, then we add hosts that are
+				// already covered by the wildcard to the skip list
+				if srv.AutoHTTPS != nil && srv.AutoHTTPS.PreferWildcard && addr.Scheme == "https" {
+					baseDomain := addr.Host
+					if idx := strings.Index(baseDomain, "."); idx != -1 {
+						baseDomain = baseDomain[idx+1:]
+					}
+					if !strings.HasPrefix(addr.Host, "*.") && sliceContains(wildcardHosts, baseDomain) {
+						srv.AutoHTTPS.Skip = append(srv.AutoHTTPS.Skip, addr.Host)
+					}
+				}
+
 				// If TLS is specified as directive, it will also result in 1 or more connection policy being created
 				// Thus, catch-all address with non-standard port, e.g. :8443, can have TLS enabled without
 				// specifying prefix "https://"
@@ -878,7 +903,10 @@ func (st *ServerType) serversFromPairings(
 		if addressQualifiesForTLS &&
 			!hasCatchAllTLSConnPolicy &&
 			(len(srv.TLSConnPolicies) > 0 || !autoHTTPSWillAddConnPolicy || defaultSNI != "" || fallbackSNI != "") {
-			srv.TLSConnPolicies = append(srv.TLSConnPolicies, &caddytls.ConnectionPolicy{DefaultSNI: defaultSNI, FallbackSNI: fallbackSNI})
+			srv.TLSConnPolicies = append(srv.TLSConnPolicies, &caddytls.ConnectionPolicy{
+				DefaultSNI:  defaultSNI,
+				FallbackSNI: fallbackSNI,
+			})
 		}
 
 		// tidy things up a bit

caddyconfig/httpcaddyfile/options.go

@@ -417,10 +417,11 @@ func parseOptAutoHTTPS(d *caddyfile.Dispenser, _ any) (any, error) {
 		case "disable_redirects":
 		case "disable_certs":
 		case "ignore_loaded_certs":
+		case "prefer_wildcard":
 			break
 
 		default:
-			return "", d.Errf("auto_https must be one of 'off', 'disable_redirects', 'disable_certs', or 'ignore_loaded_certs'")
+			return "", d.Errf("auto_https must be one of 'off', 'disable_redirects', 'disable_certs', 'ignore_loaded_certs', or 'prefer_wildcard'")
 		}
 	}
 	return val, nil

caddyconfig/httpcaddyfile/tlsapp.go

@@ -416,7 +416,10 @@ func (st ServerType) buildTLSApp(
 		}
 
 		// consolidate automation policies that are the exact same
-		tlsApp.Automation.Policies = consolidateAutomationPolicies(tlsApp.Automation.Policies)
+		tlsApp.Automation.Policies = consolidateAutomationPolicies(
+			tlsApp.Automation.Policies,
+			sliceContains(autoHTTPS, "prefer_wildcard"),
+		)
 
 		// ensure automation policies don't overlap subjects (this should be
 		// an error at provision-time as well, but catch it in the adapt phase
@@ -535,7 +538,7 @@ func newBaseAutomationPolicy(options map[string]any, warnings []caddyconfig.Warn
 
 // consolidateAutomationPolicies combines automation policies that are the same,
 // for a cleaner overall output.
-func consolidateAutomationPolicies(aps []*caddytls.AutomationPolicy) []*caddytls.AutomationPolicy {
+func consolidateAutomationPolicies(aps []*caddytls.AutomationPolicy, preferWildcard bool) []*caddytls.AutomationPolicy {
 	// sort from most specific to least specific; we depend on this ordering
 	sort.SliceStable(aps, func(i, j int) bool {
 		if automationPolicyIsSubset(aps[i], aps[j]) {
@@ -620,6 +623,31 @@ outer:
 					j--
 				}
 			}
+
+			if preferWildcard {
+				// remove subjects from i if they're covered by a wildcard in j
+				iSubjs := aps[i].SubjectsRaw
+				for iSubj := 0; iSubj < len(iSubjs); iSubj++ {
+					for jSubj := range aps[j].SubjectsRaw {
+						if !strings.HasPrefix(aps[j].SubjectsRaw[jSubj], "*.") {
+							continue
+						}
+						if certmagic.MatchWildcard(aps[i].SubjectsRaw[iSubj], aps[j].SubjectsRaw[jSubj]) {
+							iSubjs = append(iSubjs[:iSubj], iSubjs[iSubj+1:]...)
+							iSubj--
+							break
+						}
+					}
+				}
+				aps[i].SubjectsRaw = iSubjs
+
+				// remove i if it has no subjects left
+				if len(aps[i].SubjectsRaw) == 0 {
+					aps = append(aps[:i], aps[i+1:]...)
+					i--
+					continue outer
+				}
+			}
 		}
 	}
 

modules/caddyhttp/autohttps.go

@@ -64,6 +64,12 @@ type AutoHTTPSConfig struct {
 	// enabled. To force automated certificate management
 	// regardless of loaded certificates, set this to true.
 	IgnoreLoadedCerts bool `json:"ignore_loaded_certificates,omitempty"`
+
+	// If true, automatic HTTPS will prefer wildcard names
+	// and ignore non-wildcard names if both are available.
+	// This allows for writing a config with top-level host
+	// matchers without having those names produce certificates.
+	PreferWildcard bool `json:"prefer_wildcard,omitempty"`
 }
 
 // Skipped returns true if name is in skipSlice, which
@@ -167,6 +173,27 @@ func (app *App) automaticHTTPSPhase1(ctx caddy.Context, repl *caddy.Replacer) er
 			}
 		}
 
+		if srv.AutoHTTPS.PreferWildcard {
+			wildcards := make(map[string]struct{})
+			for d := range serverDomainSet {
+				if strings.HasPrefix(d, "*.") {
+					wildcards[d[2:]] = struct{}{}
+				}
+			}
+			for d := range serverDomainSet {
+				if strings.HasPrefix(d, "*.") {
+					continue
+				}
+				base := d
+				if idx := strings.Index(d, "."); idx != -1 {
+					base = d[idx+1:]
+				}
+				if _, ok := wildcards[base]; ok {
+					delete(serverDomainSet, d)
+				}
+			}
+		}
+
 		// nothing more to do here if there are no domains that qualify for
 		// automatic HTTPS and there are no explicit TLS connection policies:
 		// if there is at least one domain but no TLS conn policy (F&&T), we'll