acmeserver: support specifying the allowed challenge types (#5794)

* acmeserver: support specifying the allowed challenge types

* add caddyfile adapt tests

* introduce basic acme_server test

* skip acme test on unsuitable environments

* skip integration tests of ACME

* documentation

* add negative-scenario test for mismatched allowed challenges

* a bit more docs

* fix tests for ACME challenges

* appease the linter

* skip ACME tests on s390x

* enable ACME challenge tests on all machines

* Apply suggestions from code review

Co-authored-by: Matt Holt <[email protected]>

---------

Co-authored-by: Matt Holt <[email protected]>

4 files changed, 454 insertions, 0 deletions

diff --git a/caddytest/integration/acme_test.go b/caddytest/integration/acme_test.go
new file mode 100644
index 000000000..00a3a6c4e
--- /dev/null
+++ b/caddytest/integration/acme_test.go
@@ -0,0 +1,261 @@
+package integration
+
+import (
+	"context"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/tls"
+	"crypto/x509"
+	"fmt"
+	"net"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/caddyserver/caddy/v2"
+	"github.com/caddyserver/caddy/v2/caddytest"
+	"github.com/mholt/acmez"
+	"github.com/mholt/acmez/acme"
+	smallstepacme "github.com/smallstep/certificates/acme"
+	"go.uber.org/zap"
+)
+
+const acmeChallengePort = 8080
+
+// Test the basic functionality of Caddy's ACME server
+func TestACMEServerWithDefaults(t *testing.T) {
+	ctx := context.Background()
+	logger, err := zap.NewDevelopment()
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	tester := caddytest.NewTester(t)
+	tester.InitServer(`
+	{
+		skip_install_trust
+		admin localhost:2999
+		http_port     9080
+		https_port    9443
+		local_certs
+	}
+	acme.localhost {
+		acme_server
+	}
+  `, "caddyfile")
+
+	datadir := caddy.AppDataDir()
+	rootCertsGlob := filepath.Join(datadir, "pki", "authorities", "local", "*.crt")
+	matches, err := filepath.Glob(rootCertsGlob)
+	if err != nil {
+		t.Errorf("could not find root certs: %s", err)
+		return
+	}
+	certPool := x509.NewCertPool()
+	for _, m := range matches {
+		certPem, err := os.ReadFile(m)
+		if err != nil {
+			t.Errorf("reading cert file '%s' error: %s", m, err)
+			return
+		}
+		if !certPool.AppendCertsFromPEM(certPem) {
+			t.Errorf("failed to append the cert: %s", m)
+			return
+		}
+	}
+
+	client := acmez.Client{
+		Client: &acme.Client{
+			Directory: "https://acme.localhost:9443/acme/local/directory",
+			HTTPClient: &http.Client{
+				Transport: &http.Transport{
+					TLSClientConfig: &tls.Config{
+						RootCAs: certPool,
+					},
+				},
+			},
+			Logger: logger,
+		},
+		ChallengeSolvers: map[string]acmez.Solver{
+			acme.ChallengeTypeHTTP01: &naiveHTTPSolver{logger: logger},
+		},
+	}
+
+	accountPrivateKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Errorf("generating account key: %v", err)
+	}
+	account := acme.Account{
+		Contact:              []string{"mailto:[email protected]"},
+		TermsOfServiceAgreed: true,
+		PrivateKey:           accountPrivateKey,
+	}
+	account, err = client.NewAccount(ctx, account)
+	if err != nil {
+		t.Errorf("new account: %v", err)
+		return
+	}
+
+	// Every certificate needs a key.
+	certPrivateKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Errorf("generating certificate key: %v", err)
+		return
+	}
+
+	certs, err := client.ObtainCertificate(ctx, account, certPrivateKey, []string{"localhost"})
+	if err != nil {
+		t.Errorf("obtaining certificate: %v", err)
+		return
+	}
+
+	// ACME servers should usually give you the entire certificate chain
+	// in PEM format, and sometimes even alternate chains! It's up to you
+	// which one(s) to store and use, but whatever you do, be sure to
+	// store the certificate and key somewhere safe and secure, i.e. don't
+	// lose them!
+	for _, cert := range certs {
+		t.Logf("Certificate %q:\n%s\n\n", cert.URL, cert.ChainPEM)
+	}
+}
+
+func TestACMEServerWithMismatchedChallenges(t *testing.T) {
+	ctx := context.Background()
+	logger := caddy.Log().Named("acmez")
+
+	tester := caddytest.NewTester(t)
+	tester.InitServer(`
+	{
+		skip_install_trust
+		admin localhost:2999
+		http_port     9080
+		https_port    9443
+		local_certs
+	}
+	acme.localhost {
+		acme_server {
+			challenges tls-alpn-01
+		}
+	}
+  `, "caddyfile")
+
+	datadir := caddy.AppDataDir()
+	rootCertsGlob := filepath.Join(datadir, "pki", "authorities", "local", "*.crt")
+	matches, err := filepath.Glob(rootCertsGlob)
+	if err != nil {
+		t.Errorf("could not find root certs: %s", err)
+		return
+	}
+	certPool := x509.NewCertPool()
+	for _, m := range matches {
+		certPem, err := os.ReadFile(m)
+		if err != nil {
+			t.Errorf("reading cert file '%s' error: %s", m, err)
+			return
+		}
+		if !certPool.AppendCertsFromPEM(certPem) {
+			t.Errorf("failed to append the cert: %s", m)
+			return
+		}
+	}
+
+	client := acmez.Client{
+		Client: &acme.Client{
+			Directory: "https://acme.localhost:9443/acme/local/directory",
+			HTTPClient: &http.Client{
+				Transport: &http.Transport{
+					TLSClientConfig: &tls.Config{
+						RootCAs: certPool,
+					},
+				},
+			},
+			Logger: logger,
+		},
+		ChallengeSolvers: map[string]acmez.Solver{
+			acme.ChallengeTypeHTTP01: &naiveHTTPSolver{logger: logger},
+		},
+	}
+
+	accountPrivateKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Errorf("generating account key: %v", err)
+	}
+	account := acme.Account{
+		Contact:              []string{"mailto:[email protected]"},
+		TermsOfServiceAgreed: true,
+		PrivateKey:           accountPrivateKey,
+	}
+	account, err = client.NewAccount(ctx, account)
+	if err != nil {
+		t.Errorf("new account: %v", err)
+		return
+	}
+
+	// Every certificate needs a key.
+	certPrivateKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Errorf("generating certificate key: %v", err)
+		return
+	}
+
+	certs, err := client.ObtainCertificate(ctx, account, certPrivateKey, []string{"localhost"})
+	if len(certs) > 0 {
+		t.Errorf("expected '0' certificates, but received '%d'", len(certs))
+	}
+	if err == nil {
+		t.Error("expected errors, but received none")
+	}
+	const expectedErrMsg = "no solvers available for remaining challenges (configured=[http-01] offered=[tls-alpn-01] remaining=[tls-alpn-01])"
+	if !strings.Contains(err.Error(), expectedErrMsg) {
+		t.Errorf(`received error message does not match expectation: expected="%s" received="%s"`, expectedErrMsg, err.Error())
+	}
+}
+
+// naiveHTTPSolver is a no-op acmez.Solver for example purposes only.
+type naiveHTTPSolver struct {
+	srv    *http.Server
+	logger *zap.Logger
+}
+
+func (s *naiveHTTPSolver) Present(ctx context.Context, challenge acme.Challenge) error {
+	smallstepacme.InsecurePortHTTP01 = acmeChallengePort
+	s.srv = &http.Server{
+		Addr: fmt.Sprintf("localhost:%d", acmeChallengePort),
+		Handler: http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			host, _, err := net.SplitHostPort(r.Host)
+			if err != nil {
+				host = r.Host
+			}
+			if r.Method == "GET" && r.URL.Path == challenge.HTTP01ResourcePath() && strings.EqualFold(host, challenge.Identifier.Value) {
+				w.Header().Add("Content-Type", "text/plain")
+				w.Write([]byte(challenge.KeyAuthorization))
+				r.Close = true
+				s.logger.Info("served key authentication",
+					zap.String("identifier", challenge.Identifier.Value),
+					zap.String("challenge", "http-01"),
+					zap.String("remote", r.RemoteAddr),
+				)
+			}
+		}),
+	}
+	l, err := net.Listen("tcp", fmt.Sprintf(":%d", acmeChallengePort))
+	if err != nil {
+		return err
+	}
+	s.logger.Info("present challenge", zap.Any("challenge", challenge))
+	go s.srv.Serve(l)
+	return nil
+}
+
+func (s naiveHTTPSolver) CleanUp(ctx context.Context, challenge acme.Challenge) error {
+	smallstepacme.InsecurePortHTTP01 = 0
+	s.logger.Info("cleanup", zap.Any("challenge", challenge))
+	if s.srv != nil {
+		s.srv.Close()
+	}
+	return nil
+}
diff --git a/caddytest/integration/caddyfile_adapt/acme_server_custom_challenges.txt b/caddytest/integration/caddyfile_adapt/acme_server_custom_challenges.txt
new file mode 100644
index 000000000..2a7a51492
--- /dev/null
+++ b/caddytest/integration/caddyfile_adapt/acme_server_custom_challenges.txt
@@ -0,0 +1,65 @@
+{
+	pki {
+		ca custom-ca {
+			name "Custom CA"
+		}
+	}
+}
+
+acme.example.com {
+	acme_server {
+		ca custom-ca
+		challenges dns-01
+	}
+}
+----------
+{
+	"apps": {
+		"http": {
+			"servers": {
+				"srv0": {
+					"listen": [
+						":443"
+					],
+					"routes": [
+						{
+							"match": [
+								{
+									"host": [
+										"acme.example.com"
+									]
+								}
+							],
+							"handle": [
+								{
+									"handler": "subroute",
+									"routes": [
+										{
+											"handle": [
+												{
+													"ca": "custom-ca",
+													"challenges": [
+														"dns-01"
+													],
+													"handler": "acme_server"
+												}
+											]
+										}
+									]
+								}
+							],
+							"terminal": true
+						}
+					]
+				}
+			}
+		},
+		"pki": {
+			"certificate_authorities": {
+				"custom-ca": {
+					"name": "Custom CA"
+				}
+			}
+		}
+	}
+}
diff --git a/caddytest/integration/caddyfile_adapt/acme_server_default_challenges.txt b/caddytest/integration/caddyfile_adapt/acme_server_default_challenges.txt
new file mode 100644
index 000000000..26d345047
--- /dev/null
+++ b/caddytest/integration/caddyfile_adapt/acme_server_default_challenges.txt
@@ -0,0 +1,62 @@
+{
+	pki {
+		ca custom-ca {
+			name "Custom CA"
+		}
+	}
+}
+
+acme.example.com {
+	acme_server {
+		ca custom-ca
+		challenges
+	}
+}
+----------
+{
+	"apps": {
+		"http": {
+			"servers": {
+				"srv0": {
+					"listen": [
+						":443"
+					],
+					"routes": [
+						{
+							"match": [
+								{
+									"host": [
+										"acme.example.com"
+									]
+								}
+							],
+							"handle": [
+								{
+									"handler": "subroute",
+									"routes": [
+										{
+											"handle": [
+												{
+													"ca": "custom-ca",
+													"handler": "acme_server"
+												}
+											]
+										}
+									]
+								}
+							],
+							"terminal": true
+						}
+					]
+				}
+			}
+		},
+		"pki": {
+			"certificate_authorities": {
+				"custom-ca": {
+					"name": "Custom CA"
+				}
+			}
+		}
+	}
+}
diff --git a/caddytest/integration/caddyfile_adapt/acme_server_multi_custom_challenges.txt b/caddytest/integration/caddyfile_adapt/acme_server_multi_custom_challenges.txt
new file mode 100644
index 000000000..7fe3ca663
--- /dev/null
+++ b/caddytest/integration/caddyfile_adapt/acme_server_multi_custom_challenges.txt
@@ -0,0 +1,66 @@
+{
+	pki {
+		ca custom-ca {
+			name "Custom CA"
+		}
+	}
+}
+
+acme.example.com {
+	acme_server {
+		ca custom-ca
+		challenges dns-01 http-01
+	}
+}
+----------
+{
+	"apps": {
+		"http": {
+			"servers": {
+				"srv0": {
+					"listen": [
+						":443"
+					],
+					"routes": [
+						{
+							"match": [
+								{
+									"host": [
+										"acme.example.com"
+									]
+								}
+							],
+							"handle": [
+								{
+									"handler": "subroute",
+									"routes": [
+										{
+											"handle": [
+												{
+													"ca": "custom-ca",
+													"challenges": [
+														"dns-01",
+														"http-01"
+													],
+													"handler": "acme_server"
+												}
+											]
+										}
+									]
+								}
+							],
+							"terminal": true
+						}
+					]
+				}
+			}
+		},
+		"pki": {
+			"certificate_authorities": {
+				"custom-ca": {
+					"name": "Custom CA"
+				}
+			}
+		}
+	}
+}