caddytls: Add support for ZeroSSL; add Caddyfile support for issuers (#3633)

* caddytls: Add support for ZeroSSL; add Caddyfile support for issuers

Configuring issuers explicitly in a Caddyfile is not easily compatible
with existing ACME-specific parameters such as email or acme_ca which
infer the kind of issuer it creates (this is complicated now because
the ZeroSSL issuer wraps the ACME issuer)... oh well, we can revisit
that later if we need to.

New Caddyfile global option:

    {
        cert_issuer <name> ...
    }

Or, alternatively, as a tls subdirective:

    tls {
        issuer <name> ...
    }

For example, to use ZeroSSL with an API key:

    {
        cert_issuser zerossl API_KEY
    }

For now, that still uses ZeroSSL's ACME endpoint; it fetches EAB
credentials for you. You can also provide the EAB credentials directly
just like any other ACME endpoint:

    {
        cert_issuer acme {
            eab KEY_ID MAC_KEY
        }
    }

All these examples use the new global option (or tls subdirective). You
can still use traditional/existing options with ZeroSSL, since it's
just another ACME endpoint:

    {
        acme_ca  https://acme.zerossl.com/v2/DV90
        acme_eab KEY_ID MAC_KEY
    }

That's all there is to it. You just can't mix-and-match acme_* options
with cert_issuer, because it becomes confusing/ambiguous/complicated to
merge the settings.

* Fix broken test

This test was asserting buggy behavior, oops - glad this branch both
discovers and fixes the bug at the same time!

* Fix broken test (post-merge)

* Update modules/caddytls/acmeissuer.go

Fix godoc comment

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

* Add support for ZeroSSL's EAB-by-email endpoint

Also transform the ACMEIssuer into ZeroSSLIssuer implicitly if set to
the ZeroSSL endpoint without EAB (the ZeroSSLIssuer is needed to
generate EAB if not already provided); this is now possible with either
an API key or an email address.

* go.mod: Use latest certmagic, acmez, and x/net

* Wrap underlying logic rather than repeating it

Oops, duh

* Form-encode email info into request body for EAB endpoint

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

3 files changed, 105 insertions, 16 deletions

diff --git a/caddyconfig/httpcaddyfile/builtins.go b/caddyconfig/httpcaddyfile/builtins.go
index 520796d..e8fbf23 100644
--- a/caddyconfig/httpcaddyfile/builtins.go
+++ b/caddyconfig/httpcaddyfile/builtins.go
@@ -29,6 +29,7 @@ import (
 	"github.com/caddyserver/caddy/v2/caddyconfig/caddyfile"
 	"github.com/caddyserver/caddy/v2/modules/caddyhttp"
 	"github.com/caddyserver/caddy/v2/modules/caddytls"
+	"github.com/caddyserver/certmagic"
 	"github.com/mholt/acmez/acme"
 	"go.uber.org/zap/zapcore"
 )
@@ -76,6 +77,7 @@ func parseBind(h Helper) ([]ConfigValue, error) {
 //         ca_root   <pem_file>
 //         dns       <provider_name>
 //         on_demand
+//         issuer <module_name> ...
 //     }
 //
 func parseTLS(h Helper) ([]ConfigValue, error) {
@@ -85,6 +87,7 @@ func parseTLS(h Helper) ([]ConfigValue, error) {
 	var certSelector caddytls.CustomCertSelectionPolicy
 	var acmeIssuer *caddytls.ACMEIssuer
 	var internalIssuer *caddytls.InternalIssuer
+	var issuer certmagic.Issuer
 	var onDemand bool
 
 	for h.Next() {
@@ -276,6 +279,28 @@ func parseTLS(h Helper) ([]ConfigValue, error) {
 					MACKey: arg[1],
 				}
 
+			case "issuer":
+				if !h.NextArg() {
+					return nil, h.ArgErr()
+				}
+				modName := h.Val()
+				mod, err := caddy.GetModule("tls.issuance." + modName)
+				if err != nil {
+					return nil, h.Errf("getting issuer module '%s': %v", modName, err)
+				}
+				unm, ok := mod.New().(caddyfile.Unmarshaler)
+				if !ok {
+					return nil, h.Errf("issuer module '%s' is not a Caddyfile unmarshaler", mod.ID)
+				}
+				err = unm.UnmarshalCaddyfile(h.NewFromNextSegment())
+				if err != nil {
+					return nil, err
+				}
+				issuer, ok = unm.(certmagic.Issuer)
+				if !ok {
+					return nil, h.Errf("module %s is not a certmagic.Issuer", mod.ID)
+				}
+
 			case "dns":
 				if !h.NextArg() {
 					return nil, h.ArgErr()
@@ -350,7 +375,24 @@ func parseTLS(h Helper) ([]ConfigValue, error) {
 		// the logic to support this would be complex
 		return nil, h.Err("cannot use both ACME and internal issuers in same server block")
 	}
-	if acmeIssuer != nil {
+	if issuer != nil && (acmeIssuer != nil || internalIssuer != nil) {
+		// similarly, the logic to support this would be complex
+		return nil, h.Err("when defining an issuer, all its config must be in its block, rather than from separate tls subdirectives")
+	}
+	switch {
+	case issuer != nil:
+		configVals = append(configVals, ConfigValue{
+			Class: "tls.cert_issuer",
+			Value: issuer,
+		})
+
+	case internalIssuer != nil:
+		configVals = append(configVals, ConfigValue{
+			Class: "tls.cert_issuer",
+			Value: internalIssuer,
+		})
+
+	case acmeIssuer != nil:
 		// fill in global defaults, if configured
 		if email := h.Option("email"); email != nil && acmeIssuer.Email == "" {
 			acmeIssuer.Email = email.(string)
@@ -361,15 +403,9 @@ func parseTLS(h Helper) ([]ConfigValue, error) {
 		if caPemFile := h.Option("acme_ca_root"); caPemFile != nil {
 			acmeIssuer.TrustedRootsPEMFiles = append(acmeIssuer.TrustedRootsPEMFiles, caPemFile.(string))
 		}
-
 		configVals = append(configVals, ConfigValue{
 			Class: "tls.cert_issuer",
-			Value: acmeIssuer,
-		})
-	} else if internalIssuer != nil {
-		configVals = append(configVals, ConfigValue{
-			Class: "tls.cert_issuer",
-			Value: internalIssuer,
+			Value: disambiguateACMEIssuer(acmeIssuer),
 		})
 	}
 
diff --git a/caddyconfig/httpcaddyfile/options.go b/caddyconfig/httpcaddyfile/options.go
index 613bbc6..7d34805 100644
--- a/caddyconfig/httpcaddyfile/options.go
+++ b/caddyconfig/httpcaddyfile/options.go
@@ -20,6 +20,7 @@ import (
 	"github.com/caddyserver/caddy/v2"
 	"github.com/caddyserver/caddy/v2/caddyconfig/caddyfile"
 	"github.com/caddyserver/caddy/v2/modules/caddytls"
+	"github.com/caddyserver/certmagic"
 	"github.com/mholt/acmez/acme"
 )
 
@@ -35,6 +36,7 @@ func init() {
 	RegisterGlobalOption("acme_ca_root", parseOptSingleString)
 	RegisterGlobalOption("acme_dns", parseOptSingleString)
 	RegisterGlobalOption("acme_eab", parseOptACMEEAB)
+	RegisterGlobalOption("cert_issuer", parseOptCertIssuer)
 	RegisterGlobalOption("email", parseOptSingleString)
 	RegisterGlobalOption("admin", parseOptAdmin)
 	RegisterGlobalOption("on_demand_tls", parseOptOnDemand)
@@ -210,6 +212,33 @@ func parseOptACMEEAB(d *caddyfile.Dispenser) (interface{}, error) {
 	return eab, nil
 }
 
+func parseOptCertIssuer(d *caddyfile.Dispenser) (interface{}, error) {
+	if !d.Next() { // consume option name
+		return nil, d.ArgErr()
+	}
+	if !d.Next() { // get issuer module name
+		return nil, d.ArgErr()
+	}
+	modName := d.Val()
+	mod, err := caddy.GetModule("tls.issuance." + modName)
+	if err != nil {
+		return nil, d.Errf("getting issuer module '%s': %v", modName, err)
+	}
+	unm, ok := mod.New().(caddyfile.Unmarshaler)
+	if !ok {
+		return nil, d.Errf("issuer module '%s' is not a Caddyfile unmarshaler", mod.ID)
+	}
+	err = unm.UnmarshalCaddyfile(d.NewFromNextSegment())
+	if err != nil {
+		return nil, err
+	}
+	iss, ok := unm.(certmagic.Issuer)
+	if !ok {
+		return nil, d.Errf("module %s is not a certmagic.Issuer", mod.ID)
+	}
+	return iss, nil
+}
+
 func parseOptSingleString(d *caddyfile.Dispenser) (interface{}, error) {
 	d.Next() // consume parameter name
 	if !d.Next() {
diff --git a/caddyconfig/httpcaddyfile/tlsapp.go b/caddyconfig/httpcaddyfile/tlsapp.go
index db6bf98..a721fee 100644
--- a/caddyconfig/httpcaddyfile/tlsapp.go
+++ b/caddyconfig/httpcaddyfile/tlsapp.go
@@ -21,6 +21,7 @@ import (
 	"reflect"
 	"sort"
 	"strconv"
+	"strings"
 
 	"github.com/caddyserver/caddy/v2"
 	"github.com/caddyserver/caddy/v2/caddyconfig"
@@ -135,8 +136,11 @@ func (st ServerType) buildTLSApp(
 				// issuer, skip, since we intend to adjust only ACME issuers
 				var acmeIssuer *caddytls.ACMEIssuer
 				if ap.Issuer != nil {
-					var ok bool
-					if acmeIssuer, ok = ap.Issuer.(*caddytls.ACMEIssuer); !ok {
+					// ensure we include any issuer that embeds/wraps an underlying ACME issuer
+					type acmeCapable interface{ GetACMEIssuer() *caddytls.ACMEIssuer }
+					if acmeWrapper, ok := ap.Issuer.(acmeCapable); ok {
+						acmeIssuer = acmeWrapper.GetACMEIssuer()
+					} else {
 						break
 					}
 				}
@@ -348,6 +352,8 @@ func (st ServerType) buildTLSApp(
 // returned if there are no default/global options. However, if always is
 // true, a non-nil value will always be returned (unless there is an error).
 func newBaseAutomationPolicy(options map[string]interface{}, warnings []caddyconfig.Warning, always bool) (*caddytls.AutomationPolicy, error) {
+	issuer, hasIssuer := options["cert_issuer"]
+
 	acmeCA, hasACMECA := options["acme_ca"]
 	acmeCARoot, hasACMECARoot := options["acme_ca_root"]
 	acmeDNS, hasACMEDNS := options["acme_dns"]
@@ -357,7 +363,7 @@ func newBaseAutomationPolicy(options map[string]interface{}, warnings []caddycon
 	localCerts, hasLocalCerts := options["local_certs"]
 	keyType, hasKeyType := options["key_type"]
 
-	hasGlobalAutomationOpts := hasACMECA || hasACMECARoot || hasACMEDNS || hasACMEEAB || hasEmail || hasLocalCerts || hasKeyType
+	hasGlobalAutomationOpts := hasIssuer || hasACMECA || hasACMECARoot || hasACMEDNS || hasACMEEAB || hasEmail || hasLocalCerts || hasKeyType
 
 	// if there are no global options related to automation policies
 	// set, then we can just return right away
@@ -369,8 +375,16 @@ func newBaseAutomationPolicy(options map[string]interface{}, warnings []caddycon
 	}
 
 	ap := new(caddytls.AutomationPolicy)
+	if keyType != nil {
+		ap.KeyType = keyType.(string)
+	}
 
-	if localCerts != nil {
+	if hasIssuer {
+		if hasACMECA || hasACMEDNS || hasACMEEAB || hasEmail || hasLocalCerts {
+			return nil, fmt.Errorf("global options are ambiguous: cert_issuer is confusing when combined with acme_*, email, or local_certs options")
+		}
+		ap.Issuer = issuer.(certmagic.Issuer)
+	} else if localCerts != nil {
 		// internal issuer enabled trumps any ACME configurations; useful in testing
 		ap.Issuer = new(caddytls.InternalIssuer) // we'll encode it later
 	} else {
@@ -402,15 +416,25 @@ func newBaseAutomationPolicy(options map[string]interface{}, warnings []caddycon
 		if acmeEAB != nil {
 			mgr.ExternalAccount = acmeEAB.(*acme.EAB)
 		}
-		if keyType != nil {
-			ap.KeyType = keyType.(string)
-		}
-		ap.Issuer = mgr // we'll encode it later
+		ap.Issuer = disambiguateACMEIssuer(mgr) // we'll encode it later
 	}
 
 	return ap, nil
 }
 
+// disambiguateACMEIssuer returns an issuer based on the properties of acmeIssuer.
+// If acmeIssuer implicitly configures a certain kind of ACMEIssuer (for example,
+// ZeroSSL), the proper wrapper over acmeIssuer will be returned instead.
+func disambiguateACMEIssuer(acmeIssuer *caddytls.ACMEIssuer) certmagic.Issuer {
+	// as a special case, we integrate with ZeroSSL's ACME endpoint if it looks like an
+	// implicit ZeroSSL configuration (this requires a  wrapper type over ACMEIssuer
+	// because of the EAB generation; if EAB is provided, we can use plain ACMEIssuer)
+	if strings.Contains(acmeIssuer.CA, "acme.zerossl.com") && acmeIssuer.ExternalAccount == nil {
+		return &caddytls.ZeroSSLIssuer{ACMEIssuer: acmeIssuer}
+	}
+	return acmeIssuer
+}
+
 // consolidateAutomationPolicies combines automation policies that are the same,
 // for a cleaner overall output.
 func consolidateAutomationPolicies(aps []*caddytls.AutomationPolicy) []*caddytls.AutomationPolicy {