httpcaddyfile: Fix panic in automation policy consolidation (#4104)

* httpcaddyfile: Add reproduce test

* httpcaddyfile: Don't allow `i` to go below zero

caddyconfig/httpcaddyfile/tlsapp.go

@@ -491,13 +491,13 @@ func consolidateAutomationPolicies(aps []*caddytls.AutomationPolicy) []*caddytls
 	}
 
 	// remove or combine duplicate policies
+outer:
 	for i := 0; i < len(aps); i++ {
 		// compare only with next policies; we sorted by specificity so we must not delete earlier policies
 		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:]...)
-				i--
 				break
 			}
 
@@ -524,6 +524,7 @@ func consolidateAutomationPolicies(aps []*caddytls.AutomationPolicy) []*caddytls
 					if automationPolicyShadows(i, aps) >= j {
 						aps = append(aps[:i], aps[i+1:]...)
 						i--
+						continue outer
 					}
 				} else {
 					// avoid repeated subjects

caddytest/integration/caddyfile_adapt/tls_automation_policies_4.txt

@@ -0,0 +1,155 @@
+{
+	email my.email@example.com
+}
+
+:82 {
+	redir https://example.com{uri}
+}
+
+:83 {
+	redir https://example.com{uri}
+}
+
+:84 {
+	redir https://example.com{uri}
+}
+
+abc.de {
+	redir https://example.com{uri}
+}
+----------
+{
+	"apps": {
+		"http": {
+			"servers": {
+				"srv0": {
+					"listen": [
+						":443"
+					],
+					"routes": [
+						{
+							"match": [
+								{
+									"host": [
+										"abc.de"
+									]
+								}
+							],
+							"handle": [
+								{
+									"handler": "subroute",
+									"routes": [
+										{
+											"handle": [
+												{
+													"handler": "static_response",
+													"headers": {
+														"Location": [
+															"https://example.com{http.request.uri}"
+														]
+													},
+													"status_code": 302
+												}
+											]
+										}
+									]
+								}
+							],
+							"terminal": true
+						}
+					]
+				},
+				"srv1": {
+					"listen": [
+						":82"
+					],
+					"routes": [
+						{
+							"handle": [
+								{
+									"handler": "static_response",
+									"headers": {
+										"Location": [
+											"https://example.com{http.request.uri}"
+										]
+									},
+									"status_code": 302
+								}
+							]
+						}
+					]
+				},
+				"srv2": {
+					"listen": [
+						":83"
+					],
+					"routes": [
+						{
+							"handle": [
+								{
+									"handler": "static_response",
+									"headers": {
+										"Location": [
+											"https://example.com{http.request.uri}"
+										]
+									},
+									"status_code": 302
+								}
+							]
+						}
+					]
+				},
+				"srv3": {
+					"listen": [
+						":84"
+					],
+					"routes": [
+						{
+							"handle": [
+								{
+									"handler": "static_response",
+									"headers": {
+										"Location": [
+											"https://example.com{http.request.uri}"
+										]
+									},
+									"status_code": 302
+								}
+							]
+						}
+					]
+				}
+			}
+		},
+		"tls": {
+			"automation": {
+				"policies": [
+					{
+						"issuers": [
+							{
+								"email": "my.email@example.com",
+								"module": "acme"
+							},
+							{
+								"email": "my.email@example.com",
+								"module": "zerossl"
+							}
+						]
+					},
+					{
+						"issuers": [
+							{
+								"email": "my.email@example.com",
+								"module": "acme"
+							},
+							{
+								"email": "my.email@example.com",
+								"module": "zerossl"
+							}
+						]
+					}
+				]
+			}
+		}
+	}
+}