httpcaddyfile: Don't put localhost in public APs (fix #4220)

If an email is specified in global options, a site called 'localhost' shouldn't be bunched together with public DNS names in the automation policies, which get the default, public-CA issuers. Fix old test that did this.

I also noticed that these two:

    localhost {
    }
    example.com {
    }

and

    localhost, example.com {
    }

produce slightly different TLS automation policies. The former is what the new test case covers, and we have logic that removes the empty automation policy for localhost so that auto-HTTPS can implicitly create one. (We prefer that whenever possible.) But the latter case produces two automation policies, with the second one being for localhost, with an explicit internal issuer. It's not wrong, just more explicit than it needs to be.

I'd really like to completely rewrite the code from scratch that generates automation policies, hopefully there is a simpler, more correct algorithm.

caddyconfig/httpcaddyfile/tlsapp.go

@@ -211,7 +211,7 @@ func (st ServerType) buildTLSApp(
 					// it that we would need to check here) since the hostname is known at handshake;
 					// and it is unexpected to switch to internal issuer when the user wants to get
 					// regular certificates on-demand for a class of certs like *.*.tld.
-					if !certmagic.SubjectIsIP(s) && !certmagic.SubjectIsInternal(s) && (strings.Count(s, "*.") < 2 || ap.OnDemand) {
+					if subjectQualifiesForPublicCert(ap, s) {
 						external = append(external, s)
 					} else {
 						internal = append(internal, s)
@@ -324,8 +324,12 @@ func (st ServerType) buildTLSApp(
 		globalPreferredChains := options["preferred_chains"]
 		hasGlobalACMEDefaults := globalEmail != nil || globalACMECA != nil || globalACMECARoot != nil || globalACMEDNS != nil || globalACMEEAB != nil || globalPreferredChains != nil
 		if hasGlobalACMEDefaults {
-			for _, ap := range tlsApp.Automation.Policies {
-				if len(ap.Issuers) == 0 {
+			// for _, ap := range tlsApp.Automation.Policies {
+			for i := 0; i < len(tlsApp.Automation.Policies); i++ {
+				ap := tlsApp.Automation.Policies[i]
+				if len(ap.Issuers) == 0 && automationPolicyHasAllPublicNames(ap) {
+					// for public names, create default issuers which will later be filled in with configured global defaults
+					// (internal names will implicitly use the internal issuer at auto-https time)
 					ap.Issuers = caddytls.DefaultIssuers()
 
 					// if a specific endpoint is configured, can't use multiple default issuers
@@ -494,16 +498,23 @@ func consolidateAutomationPolicies(aps []*caddytls.AutomationPolicy) []*caddytls
 	})
 
 	emptyAPCount := 0
+	origLenAPs := len(aps)
 	// compute the number of empty policies (disregarding subjects) - see #4128
 	emptyAP := new(caddytls.AutomationPolicy)
 	for i := 0; i < len(aps); i++ {
 		emptyAP.Subjects = aps[i].Subjects
 		if reflect.DeepEqual(aps[i], emptyAP) {
 			emptyAPCount++
+			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:]...)
+				i--
+			}
 		}
 	}
 	// If all policies are empty, we can return nil, as there is no need to set any policy
-	if emptyAPCount == len(aps) {
+	if emptyAPCount == origLenAPs {
 		return nil
 	}
 
@@ -601,3 +612,21 @@ func automationPolicyShadows(i int, aps []*caddytls.AutomationPolicy) int {
 	}
 	return -1
 }
+
+// subjectQualifiesForPublicCert is like certmagic.SubjectQualifiesForPublicCert() except
+// that this allows domains with multiple wildcard levels like '*.*.example.com' to qualify
+// if the automation policy has OnDemand enabled (i.e. this function is more lenient).
+func subjectQualifiesForPublicCert(ap *caddytls.AutomationPolicy, subj string) bool {
+	return !certmagic.SubjectIsIP(subj) &&
+		!certmagic.SubjectIsInternal(subj) &&
+		(strings.Count(subj, "*.") < 2 || ap.OnDemand)
+}
+
+func automationPolicyHasAllPublicNames(ap *caddytls.AutomationPolicy) bool {
+	for _, subj := range ap.Subjects {
+		if !subjectQualifiesForPublicCert(ap, subj) {
+			return false
+		}
+	}
+	return true
+}

caddytest/integration/caddyfile_adapt/global_options_preferred_chains.txt

@@ -2,7 +2,7 @@
 	preferred_chains smallest
 }
 
-localhost
+example.com
 ----------
 {
 	"apps": {
@@ -17,7 +17,7 @@ localhost
 							"match": [
 								{
 									"host": [
-										"localhost"
+										"example.com"
 									]
 								}
 							],
@@ -32,7 +32,7 @@ localhost
 				"policies": [
 					{
 						"subjects": [
-							"localhost"
+							"example.com"
 						],
 						"issuers": [
 							{

caddytest/integration/caddyfile_adapt/tls_automation_policies_global_email_localhost.txt

@@ -0,0 +1,66 @@
+{
+	email foo@bar
+}
+
+localhost {
+}
+
+example.com {
+}
+----------
+{
+	"apps": {
+		"http": {
+			"servers": {
+				"srv0": {
+					"listen": [
+						":443"
+					],
+					"routes": [
+						{
+							"match": [
+								{
+									"host": [
+										"example.com"
+									]
+								}
+							],
+							"terminal": true
+						},
+						{
+							"match": [
+								{
+									"host": [
+										"localhost"
+									]
+								}
+							],
+							"terminal": true
+						}
+					]
+				}
+			}
+		},
+		"tls": {
+			"automation": {
+				"policies": [
+					{
+						"subjects": [
+							"example.com"
+						],
+						"issuers": [
+							{
+								"email": "foo@bar",
+								"module": "acme"
+							},
+							{
+								"email": "foo@bar",
+								"module": "zerossl"
+							}
+						]
+					}
+				]
+			}
+		}
+	}
+}