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>

1 files changed, 39 insertions, 18 deletions

diff --git a/modules/caddytls/internalissuer.go b/modules/caddytls/internalissuer.go
index ca43bf8..d70b8ca 100644
--- a/modules/caddytls/internalissuer.go
+++ b/modules/caddytls/internalissuer.go
@@ -23,6 +23,7 @@ import (
 	"time"
 
 	"github.com/caddyserver/caddy/v2"
+	"github.com/caddyserver/caddy/v2/caddyconfig/caddyfile"
 	"github.com/caddyserver/caddy/v2/modules/caddypki"
 	"github.com/caddyserver/certmagic"
 	"github.com/smallstep/certificates/authority/provisioner"
@@ -63,25 +64,25 @@ func (InternalIssuer) CaddyModule() caddy.ModuleInfo {
 }
 
 // Provision sets up the issuer.
-func (li *InternalIssuer) Provision(ctx caddy.Context) error {
+func (iss *InternalIssuer) Provision(ctx caddy.Context) error {
 	// get a reference to the configured CA
 	appModule, err := ctx.App("pki")
 	if err != nil {
 		return err
 	}
 	pkiApp := appModule.(*caddypki.PKI)
-	if li.CA == "" {
-		li.CA = caddypki.DefaultCAID
+	if iss.CA == "" {
+		iss.CA = caddypki.DefaultCAID
 	}
-	ca, ok := pkiApp.CAs[li.CA]
+	ca, ok := pkiApp.CAs[iss.CA]
 	if !ok {
-		return fmt.Errorf("no certificate authority configured with id: %s", li.CA)
+		return fmt.Errorf("no certificate authority configured with id: %s", iss.CA)
 	}
-	li.ca = ca
+	iss.ca = ca
 
 	// set any other default values
-	if li.Lifetime == 0 {
-		li.Lifetime = caddy.Duration(defaultInternalCertLifetime)
+	if iss.Lifetime == 0 {
+		iss.Lifetime = caddy.Duration(defaultInternalCertLifetime)
 	}
 
 	return nil
@@ -89,38 +90,38 @@ func (li *InternalIssuer) Provision(ctx caddy.Context) error {
 
 // IssuerKey returns the unique issuer key for the
 // confgured CA endpoint.
-func (li InternalIssuer) IssuerKey() string {
-	return li.ca.ID()
+func (iss InternalIssuer) IssuerKey() string {
+	return iss.ca.ID()
 }
 
 // Issue issues a certificate to satisfy the CSR.
-func (li InternalIssuer) Issue(ctx context.Context, csr *x509.CertificateRequest) (*certmagic.IssuedCertificate, error) {
+func (iss InternalIssuer) Issue(ctx context.Context, csr *x509.CertificateRequest) (*certmagic.IssuedCertificate, error) {
 	// prepare the signing authority
 	authCfg := caddypki.AuthorityConfig{
-		SignWithRoot: li.SignWithRoot,
+		SignWithRoot: iss.SignWithRoot,
 	}
-	auth, err := li.ca.NewAuthority(authCfg)
+	auth, err := iss.ca.NewAuthority(authCfg)
 	if err != nil {
 		return nil, err
 	}
 
 	// get the cert (public key) that will be used for signing
 	var issuerCert *x509.Certificate
-	if li.SignWithRoot {
-		issuerCert = li.ca.RootCertificate()
+	if iss.SignWithRoot {
+		issuerCert = iss.ca.RootCertificate()
 	} else {
-		issuerCert = li.ca.IntermediateCertificate()
+		issuerCert = iss.ca.IntermediateCertificate()
 	}
 
 	// ensure issued certificate does not expire later than its issuer
-	lifetime := time.Duration(li.Lifetime)
+	lifetime := time.Duration(iss.Lifetime)
 	if time.Now().Add(lifetime).After(issuerCert.NotAfter) {
 		// TODO: log this
 		lifetime = issuerCert.NotAfter.Sub(time.Now())
 	}
 
 	certChain, err := auth.Sign(csr, provisioner.Options{},
-		profileDefaultDuration(li.Lifetime),
+		profileDefaultDuration(iss.Lifetime),
 	)
 	if err != nil {
 		return nil, err
@@ -139,6 +140,26 @@ func (li InternalIssuer) Issue(ctx context.Context, csr *x509.CertificateRequest
 	}, nil
 }
 
+// UnmarshalCaddyfile deserializes Caddyfile tokens into iss.
+//
+//     ... internal {
+//         ca <name>
+//     }
+//
+func (iss *InternalIssuer) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
+	for d.Next() {
+		for d.NextBlock(0) {
+			switch d.Val() {
+			case "ca":
+				if !d.AllArgs(&iss.CA) {
+					return d.ArgErr()
+				}
+			}
+		}
+	}
+	return nil
+}
+
 // profileDefaultDuration is a wrapper against x509util.WithOption to conform
 // the SignOption interface.
 //