httpcaddyfile: Revise automation policy generation (#3824)

* httpcaddyfile: Revise automation policy generation

This should fix a frustrating edge case where wildcard subjects are
used, which potentially get shadowed by more specific versions of
themselves; see the new tests for an example. This change is motivated
by an actual customer requirement.

Although all the tests pass, this logic is incredibly complex and
nuanced, and I'm worried it is not correct. But it took me about 4 days
to get this far on a solution. I did my best.

* Fix typo

caddyconfig/httpcaddyfile/tlsapp.go

@@ -76,30 +76,35 @@ func (st ServerType) buildTLSApp(
 		}
 	}
 
+	// a catch-all automation policy is used as a "default" for all subjects that
+	// don't have custom configuration explicitly associated with them; this
+	// is only to add if the global settings or defaults are non-empty
 	catchAllAP, err := newBaseAutomationPolicy(options, warnings, false)
 	if err != nil {
 		return nil, warnings, err
 	}
+	if catchAllAP != nil {
+		if tlsApp.Automation == nil {
+			tlsApp.Automation = new(caddytls.AutomationConfig)
+		}
+		tlsApp.Automation.Policies = append(tlsApp.Automation.Policies, catchAllAP)
+	}
 
 	for _, p := range pairings {
 		for _, sblock := range p.serverBlocks {
 			// get values that populate an automation policy for this block
-			var ap *caddytls.AutomationPolicy
+			ap, err := newBaseAutomationPolicy(options, warnings, true)
+			if err != nil {
+				return nil, warnings, err
+			}
 
 			sblockHosts := sblock.hostsFromKeys(false)
-			if len(sblockHosts) == 0 {
+			if len(sblockHosts) == 0 && catchAllAP != nil {
 				ap = catchAllAP
 			}
 
 			// on-demand tls
 			if _, ok := sblock.pile["tls.on_demand"]; ok {
-				if ap == nil {
-					var err error
-					ap, err = newBaseAutomationPolicy(options, warnings, true)
-					if err != nil {
-						return nil, warnings, err
-					}
-				}
 				ap.OnDemand = true
 			}
 
@@ -107,13 +112,6 @@ func (st ServerType) buildTLSApp(
 			if issuerVals, ok := sblock.pile["tls.cert_issuer"]; ok {
 				for _, issuerVal := range issuerVals {
 					issuer := issuerVal.Value.(certmagic.Issuer)
-					if ap == nil {
-						var err error
-						ap, err = newBaseAutomationPolicy(options, warnings, true)
-						if err != nil {
-							return nil, warnings, err
-						}
-					}
 					if ap == catchAllAP && !reflect.DeepEqual(ap.Issuer, issuer) {
 						return nil, warnings, fmt.Errorf("automation policy from site block is also default/catch-all policy because of key without hostname, and the two are in conflict: %#v != %#v", ap.Issuer, issuer)
 					}
@@ -123,15 +121,6 @@ func (st ServerType) buildTLSApp(
 
 			// custom bind host
 			for _, cfgVal := range sblock.pile["bind"] {
-				// either an existing issuer is already configured (and thus, ap is not
-				// nil), or we need to configure an issuer, so we need ap to be non-nil
-				if ap == nil {
-					ap, err = newBaseAutomationPolicy(options, warnings, true)
-					if err != nil {
-						return nil, warnings, err
-					}
-				}
-
 				// if an issuer was already configured and it is NOT an ACME
 				// issuer, skip, since we intend to adjust only ACME issuers
 				var acmeIssuer *caddytls.ACMEIssuer
@@ -164,13 +153,6 @@ func (st ServerType) buildTLSApp(
 				ap.Issuer = acmeIssuer // we'll encode it later
 			}
 
-			if ap != nil {
-				if ap.Issuer != nil {
-					// encode issuer now that it's all set up
-					issuerName := ap.Issuer.(caddy.Module).CaddyModule().ID.Name()
-					ap.IssuerRaw = caddyconfig.JSONModuleObject(ap.Issuer, "module", issuerName, &warnings)
-				}
-
 			// first make sure this block is allowed to create an automation policy;
 			// doing so is forbidden if it has a key with no host (i.e. ":443")
 			// and if there is a different server block that also has a key with no
@@ -196,13 +178,9 @@ func (st ServerType) buildTLSApp(
 				}
 			}
 
-				// associate our new automation policy with this server block's hosts,
-				// unless, of course, the server block has a key with no hosts, in which
-				// case its automation policy becomes or blends with the default/global
-				// automation policy because, of necessity, it applies to all hostnames
-				// (i.e. it has no Subjects filter) -- in that case, we'll append it last
-				if ap != catchAllAP {
+			// associate our new automation policy with this server block's hosts
 			ap.Subjects = sblockHosts
+			sort.Strings(ap.Subjects) // solely for deterministic test results
 
 			// if a combination of public and internal names were given
 			// for this same server block and no issuer was specified, we
@@ -244,8 +222,6 @@ func (st ServerType) buildTLSApp(
 			if ap2 != nil {
 				tlsApp.Automation.Policies = append(tlsApp.Automation.Policies, ap2)
 			}
-				}
-			}
 
 			// certificate loaders
 			if clVals, ok := sblock.pile["tls.cert_loader"]; ok {
@@ -319,23 +295,17 @@ func (st ServerType) buildTLSApp(
 		tlsApp.Automation.Policies = append(tlsApp.Automation.Policies, internalAP)
 	}
 
-	// if there is a global/catch-all automation policy, ensure it goes last
-	if catchAllAP != nil {
-		// first, encode its issuer, if there is one
-		if catchAllAP.Issuer != nil {
-			issuerName := catchAllAP.Issuer.(caddy.Module).CaddyModule().ID.Name()
-			catchAllAP.IssuerRaw = caddyconfig.JSONModuleObject(catchAllAP.Issuer, "module", issuerName, &warnings)
-		}
-
-		// then append it to the end of the policies list
-		if tlsApp.Automation == nil {
-			tlsApp.Automation = new(caddytls.AutomationConfig)
-		}
-		tlsApp.Automation.Policies = append(tlsApp.Automation.Policies, catchAllAP)
-	}
-
-	// do a little verification & cleanup
+	// finalize and verify policies; do cleanup
 	if tlsApp.Automation != nil {
+		// encode any issuer values we created, so they will be rendered in the output
+		for _, ap := range tlsApp.Automation.Policies {
+			if ap.Issuer != nil && ap.IssuerRaw == nil {
+				// encode issuer now that it's all set up
+				issuerName := ap.Issuer.(caddy.Module).CaddyModule().ID.Name()
+				ap.IssuerRaw = caddyconfig.JSONModuleObject(ap.Issuer, "module", issuerName, &warnings)
+			}
+		}
+
 		// consolidate automation policies that are the exact same
 		tlsApp.Automation.Policies = consolidateAutomationPolicies(tlsApp.Automation.Policies)
 
@@ -351,6 +321,14 @@ func (st ServerType) buildTLSApp(
 				automationHostSet[s] = struct{}{}
 			}
 		}
+
+		// if nothing remains, remove any excess values to clean up the resulting config
+		if len(tlsApp.Automation.Policies) == 0 {
+			tlsApp.Automation.Policies = nil
+		}
+		if reflect.DeepEqual(tlsApp.Automation, new(caddytls.AutomationConfig)) {
+			tlsApp.Automation = nil
+		}
 	}
 
 	return tlsApp, warnings, nil
@@ -448,12 +426,30 @@ func disambiguateACMEIssuer(acmeIssuer *caddytls.ACMEIssuer) certmagic.Issuer {
 // consolidateAutomationPolicies combines automation policies that are the same,
 // for a cleaner overall output.
 func consolidateAutomationPolicies(aps []*caddytls.AutomationPolicy) []*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]) {
+			return true
+		}
+		if automationPolicyIsSubset(aps[j], aps[i]) {
+			return false
+		}
+		return len(aps[i].Subjects) > len(aps[j].Subjects)
+	})
+
+	// remove any empty policies (except subjects, of course)
+	emptyAP := new(caddytls.AutomationPolicy)
 	for i := 0; i < len(aps); i++ {
-		for j := 0; j < len(aps); j++ {
-			if j == i {
-				continue
+		emptyAP.Subjects = aps[i].Subjects
+		if reflect.DeepEqual(aps[i], emptyAP) {
+			aps = append(aps[:i], aps[i+1:]...)
+			i--
+		}
 	}
 
+	// remove or combine duplicate policies
+	for i := 0; i < len(aps); i++ {
+		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:]...)
@@ -473,10 +469,17 @@ func consolidateAutomationPolicies(aps []*caddytls.AutomationPolicy) []*caddytls
 				aps[i].KeyType == aps[j].KeyType &&
 				aps[i].OnDemand == aps[j].OnDemand &&
 				aps[i].RenewalWindowRatio == aps[j].RenewalWindowRatio {
-				if len(aps[i].Subjects) == 0 && len(aps[j].Subjects) > 0 {
-					aps = append(aps[:j], aps[j+1:]...)
-				} else if len(aps[i].Subjects) > 0 && len(aps[j].Subjects) == 0 {
+				if len(aps[i].Subjects) > 0 && len(aps[j].Subjects) == 0 {
+					// later policy (at j) has no subjects ("catch-all"), so we can
+					// remove the identical-but-more-specific policy that comes first
+					// AS LONG AS it is not shadowed by another policy before it; e.g.
+					// if policy i is for example.com, policy i+1 is '*.com', and policy
+					// j is catch-all, we cannot remove policy i because that would
+					// 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:]...)
+					}
 				} else {
 					// avoid repeated subjects
 					for _, subj := range aps[j].Subjects {
@@ -486,16 +489,48 @@ func consolidateAutomationPolicies(aps []*caddytls.AutomationPolicy) []*caddytls
 					}
 					aps = append(aps[:j], aps[j+1:]...)
 				}
-				i--
-				break
 			}
 		}
 	}
 
-	// ensure any catch-all policies go last
-	sort.SliceStable(aps, func(i, j int) bool {
-		return len(aps[i].Subjects) > len(aps[j].Subjects)
-	})
-
 	return aps
 }
+
+// automationPolicyIsSubset returns true if a's subjects are a subset
+// of b's subjects.
+func automationPolicyIsSubset(a, b *caddytls.AutomationPolicy) bool {
+	if len(b.Subjects) == 0 {
+		return true
+	}
+	if len(a.Subjects) == 0 {
+		return false
+	}
+	for _, aSubj := range a.Subjects {
+		var inSuperset bool
+		for _, bSubj := range b.Subjects {
+			if certmagic.MatchWildcard(aSubj, bSubj) {
+				inSuperset = true
+				break
+			}
+		}
+		if !inSuperset {
+			return false
+		}
+	}
+	return true
+}
+
+// automationPolicyShadows returns the index of a policy that aps[i] shadows;
+// in other words, for all policies after position i, if that policy covers
+// the same subjects but is less specific, that policy's position is returned,
+// or -1 if no shadowing is found. For example, if policy i is for
+// "foo.example.com" and policy i+2 is for "*.example.com", then i+2 will be
+// returned, since that policy is shadowed by i, which is in front.
+func automationPolicyShadows(i int, aps []*caddytls.AutomationPolicy) int {
+	for j := i + 1; j < len(aps); j++ {
+		if automationPolicyIsSubset(aps[i], aps[j]) {
+			return j
+		}
+	}
+	return -1
+}

caddyconfig/httpcaddyfile/tlsapp_test.go

@@ -0,0 +1,56 @@
+package httpcaddyfile
+
+import (
+	"testing"
+
+	"github.com/caddyserver/caddy/v2/modules/caddytls"
+)
+
+func TestAutomationPolicyIsSubset(t *testing.T) {
+	for i, test := range []struct {
+		a, b   []string
+		expect bool
+	}{
+		{
+			a:      []string{"example.com"},
+			b:      []string{},
+			expect: true,
+		},
+		{
+			a:      []string{},
+			b:      []string{"example.com"},
+			expect: false,
+		},
+		{
+			a:      []string{"foo.example.com"},
+			b:      []string{"*.example.com"},
+			expect: true,
+		},
+		{
+			a:      []string{"foo.example.com"},
+			b:      []string{"foo.example.com"},
+			expect: true,
+		},
+		{
+			a:      []string{"foo.example.com"},
+			b:      []string{"example.com"},
+			expect: false,
+		},
+		{
+			a:      []string{"example.com", "foo.example.com"},
+			b:      []string{"*.com", "*.*.com"},
+			expect: true,
+		},
+		{
+			a:      []string{"example.com", "foo.example.com"},
+			b:      []string{"*.com"},
+			expect: false,
+		},
+	} {
+		apA := &caddytls.AutomationPolicy{Subjects: test.a}
+		apB := &caddytls.AutomationPolicy{Subjects: test.b}
+		if actual := automationPolicyIsSubset(apA, apB); actual != test.expect {
+			t.Errorf("Test %d: Expected %t but got %t (A: %v  B: %v)", i, test.expect, actual, test.a, test.b)
+		}
+	}
+}

caddytest/integration/caddyfile_adapt/tls_automation_policies.txt

@@ -0,0 +1,80 @@
+{
+	local_certs
+}
+
+*.tld, *.*.tld {
+	tls {
+		on_demand
+	}
+}
+
+foo.tld, www.foo.tld {
+}
+----------
+{
+	"apps": {
+		"http": {
+			"servers": {
+				"srv0": {
+					"listen": [
+						":443"
+					],
+					"routes": [
+						{
+							"match": [
+								{
+									"host": [
+										"foo.tld",
+										"www.foo.tld"
+									]
+								}
+							],
+							"terminal": true
+						},
+						{
+							"match": [
+								{
+									"host": [
+										"*.tld",
+										"*.*.tld"
+									]
+								}
+							],
+							"terminal": true
+						}
+					]
+				}
+			}
+		},
+		"tls": {
+			"automation": {
+				"policies": [
+					{
+						"subjects": [
+							"foo.tld",
+							"www.foo.tld"
+						],
+						"issuer": {
+							"module": "internal"
+						}
+					},
+					{
+						"subjects": [
+							"*.*.tld",
+							"*.tld"
+						],
+						"issuer": {
+							"module": "internal"
+						},
+						"on_demand": true
+					},
+					{
+						"issuer": {
+							"module": "internal"
+						}
+					}
+				]
+			}
+		}
+	}
+}