tls: Add tls_resolvers global option for DNS challenge configuration (#7297)

Co-authored-by: Francis Lavoie <lavofr@gmail.com>

caddyconfig/httpcaddyfile/options.go

@@ -64,6 +64,7 @@ func init() {
 	RegisterGlobalOption("preferred_chains", parseOptPreferredChains)
 	RegisterGlobalOption("persist_config", parseOptPersistConfig)
 	RegisterGlobalOption("dns", parseOptDNS)
+	RegisterGlobalOption("tls_resolvers", parseOptTLSResolvers)
 	RegisterGlobalOption("ech", parseOptECH)
 	RegisterGlobalOption("renewal_window_ratio", parseOptRenewalWindowRatio)
 }
@@ -306,6 +307,15 @@ func parseOptSingleString(d *caddyfile.Dispenser, _ any) (any, error) {
 	return val, nil
 }
 
+func parseOptTLSResolvers(d *caddyfile.Dispenser, _ any) (any, error) {
+	d.Next() // consume option name
+	resolvers := d.RemainingArgs()
+	if len(resolvers) == 0 {
+		return nil, d.ArgErr()
+	}
+	return resolvers, nil
+}
+
 func parseOptDefaultBind(d *caddyfile.Dispenser, _ any) (any, error) {
 	d.Next() // consume option name
 

caddyconfig/httpcaddyfile/options_test.go

@@ -1,9 +1,11 @@
 package httpcaddyfile
 
 import (
+	"encoding/json"
 	"testing"
 
 	"github.com/caddyserver/caddy/v2/caddyconfig/caddyfile"
+	"github.com/caddyserver/caddy/v2/modules/caddytls"
 	_ "github.com/caddyserver/caddy/v2/modules/logging"
 )
 
@@ -62,3 +64,105 @@ func TestGlobalLogOptionSyntax(t *testing.T) {
 		}
 	}
 }
+
+func TestGlobalResolversOption(t *testing.T) {
+	tests := []struct {
+		name            string
+		input           string
+		expectResolvers []string
+		expectError     bool
+	}{
+		{
+			name: "single resolver",
+			input: `{
+				tls_resolvers 1.1.1.1
+			}
+			example.com {
+			}`,
+			expectResolvers: []string{"1.1.1.1"},
+			expectError:     false,
+		},
+		{
+			name: "two resolvers",
+			input: `{
+				tls_resolvers 1.1.1.1 8.8.8.8
+			}
+			example.com {
+			}`,
+			expectResolvers: []string{"1.1.1.1", "8.8.8.8"},
+			expectError:     false,
+		},
+		{
+			name: "multiple resolvers",
+			input: `{
+				tls_resolvers 1.1.1.1 8.8.8.8 9.9.9.9
+			}
+			example.com {
+			}`,
+			expectResolvers: []string{"1.1.1.1", "8.8.8.8", "9.9.9.9"},
+			expectError:     false,
+		},
+		{
+			name: "no resolvers specified",
+			input: `{
+			}
+			example.com {
+			}`,
+			expectResolvers: nil,
+			expectError:     false,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			adapter := caddyfile.Adapter{
+				ServerType: ServerType{},
+			}
+
+			out, _, err := adapter.Adapt([]byte(tc.input), nil)
+
+			if (err != nil) != tc.expectError {
+				t.Errorf("error expectation failed. Expected error: %v, got: %v", tc.expectError, err)
+				return
+			}
+
+			if tc.expectError {
+				return
+			}
+
+			// Parse the output JSON to check resolvers
+			var config struct {
+				Apps struct {
+					TLS *caddytls.TLS `json:"tls"`
+				} `json:"apps"`
+			}
+
+			if err := json.Unmarshal(out, &config); err != nil {
+				t.Errorf("failed to unmarshal output: %v", err)
+				return
+			}
+
+			// Check if resolvers match expected
+			if config.Apps.TLS == nil {
+				if tc.expectResolvers != nil {
+					t.Errorf("Expected TLS config with resolvers %v, but TLS config is nil", tc.expectResolvers)
+				}
+				return
+			}
+
+			actualResolvers := config.Apps.TLS.Resolvers
+			if len(tc.expectResolvers) == 0 && len(actualResolvers) == 0 {
+				return // Both empty, ok
+			}
+			if len(actualResolvers) != len(tc.expectResolvers) {
+				t.Errorf("Expected %d resolvers, got %d. Expected: %v, got: %v", len(tc.expectResolvers), len(actualResolvers), tc.expectResolvers, actualResolvers)
+				return
+			}
+			for j, expected := range tc.expectResolvers {
+				if actualResolvers[j] != expected {
+					t.Errorf("Resolver %d mismatch. Expected: %s, got: %s", j, expected, actualResolvers[j])
+				}
+			}
+		})
+	}
+}

caddyconfig/httpcaddyfile/tlsapp.go

@@ -334,6 +334,11 @@ func (st ServerType) buildTLSApp(
 		tlsApp.DNSRaw = caddyconfig.JSONModuleObject(globalDNS, "name", globalDNS.(caddy.Module).CaddyModule().ID.Name(), nil)
 	}
 
+	// set up "global" (to the TLS app) DNS resolvers config
+	if globalResolvers, ok := options["tls_resolvers"]; ok && globalResolvers != nil {
+		tlsApp.Resolvers = globalResolvers.([]string)
+	}
+
 	// set up ECH from Caddyfile options
 	if ech, ok := options["ech"].(*caddytls.ECH); ok {
 		tlsApp.EncryptedClientHello = ech
@@ -595,6 +600,15 @@ func fillInGlobalACMEDefaults(issuer certmagic.Issuer, options map[string]any) e
 	if globalCertLifetime != nil && acmeIssuer.CertificateLifetime == 0 {
 		acmeIssuer.CertificateLifetime = globalCertLifetime.(caddy.Duration)
 	}
+	// apply global resolvers if DNS challenge is configured and resolvers are not already set
+	globalResolvers := options["tls_resolvers"]
+	if globalResolvers != nil && acmeIssuer.Challenges != nil && acmeIssuer.Challenges.DNS != nil {
+		// Check if DNS challenge is actually configured
+		hasDNSChallenge := globalACMEDNSok || acmeIssuer.Challenges.DNS.ProviderRaw != nil
+		if hasDNSChallenge && len(acmeIssuer.Challenges.DNS.Resolvers) == 0 {
+			acmeIssuer.Challenges.DNS.Resolvers = globalResolvers.([]string)
+		}
+	}
 	return nil
 }
 

caddytest/integration/caddyfile_adapt/global_options_resolvers.caddyfiletest

@@ -0,0 +1,77 @@
+{
+	email test@example.com
+	dns mock
+	tls_resolvers 1.1.1.1 8.8.8.8
+	acme_dns
+}
+
+example.com {
+}
+----------
+{
+	"apps": {
+		"http": {
+			"servers": {
+				"srv0": {
+					"listen": [
+						":443"
+					],
+					"routes": [
+						{
+							"match": [
+								{
+									"host": [
+										"example.com"
+									]
+								}
+							],
+							"terminal": true
+						}
+					]
+				}
+			}
+		},
+		"tls": {
+			"automation": {
+				"policies": [
+					{
+						"issuers": [
+							{
+								"challenges": {
+									"dns": {
+										"resolvers": [
+											"1.1.1.1",
+											"8.8.8.8"
+										]
+									}
+								},
+								"email": "test@example.com",
+								"module": "acme"
+							},
+							{
+								"ca": "https://acme.zerossl.com/v2/DV90",
+								"challenges": {
+									"dns": {
+										"resolvers": [
+											"1.1.1.1",
+											"8.8.8.8"
+										]
+									}
+								},
+								"email": "test@example.com",
+								"module": "acme"
+							}
+						]
+					}
+				]
+			},
+			"dns": {
+				"name": "mock"
+			},
+			"resolvers": [
+				"1.1.1.1",
+				"8.8.8.8"
+			]
+		}
+	}
+}

caddytest/integration/caddyfile_adapt/global_options_resolvers_http_challenge.caddyfiletest

@@ -0,0 +1,38 @@
+{
+	tls_resolvers 1.1.1.1 8.8.8.8
+}
+
+example.com {
+}
+----------
+{
+	"apps": {
+		"http": {
+			"servers": {
+				"srv0": {
+					"listen": [
+						":443"
+					],
+					"routes": [
+						{
+							"match": [
+								{
+									"host": [
+										"example.com"
+									]
+								}
+							],
+							"terminal": true
+						}
+					]
+				}
+			}
+		},
+		"tls": {
+			"resolvers": [
+				"1.1.1.1",
+				"8.8.8.8"
+			]
+		}
+	}
+}

caddytest/integration/caddyfile_adapt/global_options_resolvers_local_dns_inherit.caddyfiletest

@@ -0,0 +1,72 @@
+{
+	email test@example.com
+	dns mock
+	tls_resolvers 1.1.1.1 8.8.8.8
+}
+
+example.com {
+	tls {
+		dns mock
+	}
+}
+----------
+{
+	"apps": {
+		"http": {
+			"servers": {
+				"srv0": {
+					"listen": [
+						":443"
+					],
+					"routes": [
+						{
+							"match": [
+								{
+									"host": [
+										"example.com"
+									]
+								}
+							],
+							"terminal": true
+						}
+					]
+				}
+			}
+		},
+		"tls": {
+			"automation": {
+				"policies": [
+					{
+						"subjects": [
+							"example.com"
+						],
+						"issuers": [
+							{
+								"challenges": {
+									"dns": {
+										"provider": {
+											"name": "mock"
+										},
+										"resolvers": [
+											"1.1.1.1",
+											"8.8.8.8"
+										]
+									}
+								},
+								"email": "test@example.com",
+								"module": "acme"
+							}
+						]
+					}
+				]
+			},
+			"dns": {
+				"name": "mock"
+			},
+			"resolvers": [
+				"1.1.1.1",
+				"8.8.8.8"
+			]
+		}
+	}
+}

caddytest/integration/caddyfile_adapt/global_options_resolvers_local_override.caddyfiletest

@@ -0,0 +1,98 @@
+{
+	email test@example.com
+	dns mock
+	tls_resolvers 1.1.1.1 8.8.8.8
+	acme_dns
+}
+
+example.com {
+	tls {
+		resolvers 9.9.9.9
+	}
+}
+----------
+{
+	"apps": {
+		"http": {
+			"servers": {
+				"srv0": {
+					"listen": [
+						":443"
+					],
+					"routes": [
+						{
+							"match": [
+								{
+									"host": [
+										"example.com"
+									]
+								}
+							],
+							"terminal": true
+						}
+					]
+				}
+			}
+		},
+		"tls": {
+			"automation": {
+				"policies": [
+					{
+						"subjects": [
+							"example.com"
+						],
+						"issuers": [
+							{
+								"challenges": {
+									"dns": {
+										"resolvers": [
+											"9.9.9.9"
+										]
+									}
+								},
+								"email": "test@example.com",
+								"module": "acme"
+							}
+						]
+					},
+					{
+						"issuers": [
+							{
+								"challenges": {
+									"dns": {
+										"resolvers": [
+											"1.1.1.1",
+											"8.8.8.8"
+										]
+									}
+								},
+								"email": "test@example.com",
+								"module": "acme"
+							},
+							{
+								"ca": "https://acme.zerossl.com/v2/DV90",
+								"challenges": {
+									"dns": {
+										"resolvers": [
+											"1.1.1.1",
+											"8.8.8.8"
+										]
+									}
+								},
+								"email": "test@example.com",
+								"module": "acme"
+							}
+						]
+					}
+				]
+			},
+			"dns": {
+				"name": "mock"
+			},
+			"resolvers": [
+				"1.1.1.1",
+				"8.8.8.8"
+			]
+		}
+	}
+}

caddytest/integration/caddyfile_adapt/global_options_resolvers_mixed.caddyfiletest

@@ -0,0 +1,112 @@
+{
+	email test@example.com
+	dns mock
+	tls_resolvers 1.1.1.1 8.8.8.8
+	acme_dns
+}
+
+site1.example.com {
+}
+
+site2.example.com {
+	tls {
+		resolvers 9.9.9.9 8.8.4.4
+	}
+}
+----------
+{
+	"apps": {
+		"http": {
+			"servers": {
+				"srv0": {
+					"listen": [
+						":443"
+					],
+					"routes": [
+						{
+							"match": [
+								{
+									"host": [
+										"site1.example.com"
+									]
+								}
+							],
+							"terminal": true
+						},
+						{
+							"match": [
+								{
+									"host": [
+										"site2.example.com"
+									]
+								}
+							],
+							"terminal": true
+						}
+					]
+				}
+			}
+		},
+		"tls": {
+			"automation": {
+				"policies": [
+					{
+						"subjects": [
+							"site2.example.com"
+						],
+						"issuers": [
+							{
+								"challenges": {
+									"dns": {
+										"resolvers": [
+											"9.9.9.9",
+											"8.8.4.4"
+										]
+									}
+								},
+								"email": "test@example.com",
+								"module": "acme"
+							}
+						]
+					},
+					{
+						"issuers": [
+							{
+								"challenges": {
+									"dns": {
+										"resolvers": [
+											"1.1.1.1",
+											"8.8.8.8"
+										]
+									}
+								},
+								"email": "test@example.com",
+								"module": "acme"
+							},
+							{
+								"ca": "https://acme.zerossl.com/v2/DV90",
+								"challenges": {
+									"dns": {
+										"resolvers": [
+											"1.1.1.1",
+											"8.8.8.8"
+										]
+									}
+								},
+								"email": "test@example.com",
+								"module": "acme"
+							}
+						]
+					}
+				]
+			},
+			"dns": {
+				"name": "mock"
+			},
+			"resolvers": [
+				"1.1.1.1",
+				"8.8.8.8"
+			]
+		}
+	}
+}

modules/caddypki/acmeserver/acmeserver.go

@@ -40,6 +40,7 @@ import (
 	"github.com/caddyserver/caddy/v2"
 	"github.com/caddyserver/caddy/v2/modules/caddyhttp"
 	"github.com/caddyserver/caddy/v2/modules/caddypki"
+	"github.com/caddyserver/caddy/v2/modules/caddytls"
 )
 
 func init() {
@@ -304,7 +305,19 @@ func (ash Handler) openDatabase() (*db.AuthDB, error) {
 // makeClient creates an ACME client which will use a custom
 // resolver instead of net.DefaultResolver.
 func (ash Handler) makeClient() (acme.Client, error) {
-	for _, v := range ash.Resolvers {
+	// If no local resolvers are configured, check for global resolvers from TLS app
+	resolversToUse := ash.Resolvers
+	if len(resolversToUse) == 0 {
+		tlsAppIface, err := ash.ctx.App("tls")
+		if err == nil {
+			tlsApp := tlsAppIface.(*caddytls.TLS)
+			if len(tlsApp.Resolvers) > 0 {
+				resolversToUse = tlsApp.Resolvers
+			}
+		}
+	}
+
+	for _, v := range resolversToUse {
 		addr, err := caddy.ParseNetworkAddressWithDefaults(v, "udp", 53)
 		if err != nil {
 			return nil, err

modules/caddytls/tls.go

@@ -123,8 +123,15 @@ type TLS struct {
 	//
 	// EXPERIMENTAL: Subject to change.
 	DNSRaw json.RawMessage `json:"dns,omitempty" caddy:"namespace=dns.providers inline_key=name"`
-	dns    any             // technically, it should be any/all of the libdns interfaces (RecordSetter, RecordAppender, etc.)
 
+	// The default DNS resolvers to use for TLS-related DNS operations, specifically
+	// for ACME DNS challenges and ACME server DNS validations.
+	// If not specified, the system default resolvers will be used.
+	//
+	// EXPERIMENTAL: Subject to change.
+	Resolvers []string `json:"resolvers,omitempty"`
+
+	dns                any // technically, it should be any/all of the libdns interfaces (RecordSetter, RecordAppender, etc.)
 	certificateLoaders []CertificateLoader
 	automateNames      map[string]struct{}
 	ctx                caddy.Context