httpcaddyfile: Add skip_install_trust global option (#4153)

Fixes https://github.com/caddyserver/caddy/issues/4002

caddyconfig/httpcaddyfile/options.go

@@ -39,6 +39,7 @@ func init() {
 	RegisterGlobalOption("acme_dns", parseOptACMEDNS)
 	RegisterGlobalOption("acme_eab", parseOptACMEEAB)
 	RegisterGlobalOption("cert_issuer", parseOptCertIssuer)
+	RegisterGlobalOption("skip_install_trust", parseOptTrue)
 	RegisterGlobalOption("email", parseOptSingleString)
 	RegisterGlobalOption("admin", parseOptAdmin)
 	RegisterGlobalOption("on_demand_tls", parseOptOnDemand)

caddyconfig/httpcaddyfile/pkiapp.go

@@ -27,15 +27,35 @@ func (st ServerType) buildPKIApp(
 
 	pkiApp := &caddypki.PKI{CAs: make(map[string]*caddypki.CA)}
 
+	skipInstallTrust := false
+	if _, ok := options["skip_install_trust"]; ok {
+		skipInstallTrust = true
+	}
+	falseBool := false
+
 	for _, p := range pairings {
 		for _, sblock := range p.serverBlocks {
 			// find all the CAs that were defined and add them to the app config
+			// i.e. from any "acme_server" directives
 			for _, caCfgValue := range sblock.pile["pki.ca"] {
 				ca := caCfgValue.Value.(*caddypki.CA)
+				if skipInstallTrust {
+					ca.InstallTrust = &falseBool
+				}
 				pkiApp.CAs[ca.ID] = ca
 			}
 		}
 	}
 
+	// if there was no CAs defined in any of the servers,
+	// and we were requested to not install trust, then
+	// add one for the default/local CA to do so
+	if len(pkiApp.CAs) == 0 && skipInstallTrust {
+		ca := new(caddypki.CA)
+		ca.ID = caddypki.DefaultCAID
+		ca.InstallTrust = &falseBool
+		pkiApp.CAs[ca.ID] = ca
+	}
+
 	return pkiApp, warnings, nil
 }

caddytest/integration/caddyfile_adapt/global_options_skip_install_trust.txt

@@ -0,0 +1,56 @@
+{
+	skip_install_trust
+}
+
+a.example.com {
+	tls internal
+}
+----------
+{
+	"apps": {
+		"http": {
+			"servers": {
+				"srv0": {
+					"listen": [
+						":443"
+					],
+					"routes": [
+						{
+							"match": [
+								{
+									"host": [
+										"a.example.com"
+									]
+								}
+							],
+							"terminal": true
+						}
+					]
+				}
+			}
+		},
+		"pki": {
+			"certificate_authorities": {
+				"local": {
+					"install_trust": false
+				}
+			}
+		},
+		"tls": {
+			"automation": {
+				"policies": [
+					{
+						"subjects": [
+							"a.example.com"
+						],
+						"issuers": [
+							{
+								"module": "internal"
+							}
+						]
+					}
+				]
+			}
+		}
+	}
+}