caddytls: Add support for externalAccountBinding ACME extension

3 files changed, 42 insertions, 9 deletions

diff --git a/go.mod b/go.mod
index 3cd325c..76fa514 100644
--- a/go.mod
+++ b/go.mod
@@ -5,7 +5,7 @@ go 1.14
 require (
 	github.com/Masterminds/sprig/v3 v3.0.2
 	github.com/alecthomas/chroma v0.7.2-0.20200305040604-4f3623dce67a
-	github.com/caddyserver/certmagic v0.10.5
+	github.com/caddyserver/certmagic v0.10.6
 	github.com/dustin/go-humanize v1.0.1-0.20200219035652-afde56e7acac
 	github.com/go-acme/lego/v3 v3.5.0
 	github.com/google/cel-go v0.4.1
@@ -21,7 +21,7 @@ require (
 	github.com/smallstep/cli v0.14.0-rc.3
 	github.com/smallstep/truststore v0.9.4
 	github.com/vulcand/oxy v1.1.0
-	github.com/yuin/goldmark v1.1.26
+	github.com/yuin/goldmark v1.1.27
 	github.com/yuin/goldmark-highlighting v0.0.0-20200307114337-60d527fdb691
 	go.uber.org/zap v1.14.1
 	golang.org/x/crypto v0.0.0-20200323165209-0ec3e9974c59
diff --git a/go.sum b/go.sum
index 3099908..aca4ed9 100644
--- a/go.sum
+++ b/go.sum
@@ -120,8 +120,8 @@ github.com/bombsimon/wsl/v2 v2.0.0/go.mod h1:mf25kr/SqFEPhhcxW1+7pxzGlW+hIl/hYTK
 github.com/boombuler/barcode v1.0.0/go.mod h1:paBWMcWSl3LHKBqUq+rly7CNSldXjb2rDl3JlRe0mD8=
 github.com/bradfitz/go-smtpd v0.0.0-20170404230938-deb6d6237625/go.mod h1:HYsPBTaaSFSlLx/70C2HPIMNZpVV8+vt/A+FMnYP11g=
 github.com/buger/jsonparser v0.0.0-20181115193947-bf1c66bbce23/go.mod h1:bbYlZJ7hK1yFx9hf58LP0zeX7UjIGs20ufpu3evjr+s=
-github.com/caddyserver/certmagic v0.10.5 h1:Dg4ipO1y23rWvFmiiRqhtUTh5Hy7PmfoFvPfDpnE8Z8=
-github.com/caddyserver/certmagic v0.10.5/go.mod h1:Y8jcUBctgk/IhpAzlHKfimZNyXCkfGgRTC0orl8gROQ=
+github.com/caddyserver/certmagic v0.10.6 h1:sCya6FmfaN74oZE46kqfaFOVoROD/mF36rTQfjN7TZc=
+github.com/caddyserver/certmagic v0.10.6/go.mod h1:Y8jcUBctgk/IhpAzlHKfimZNyXCkfGgRTC0orl8gROQ=
 github.com/cenkalti/backoff/v4 v4.0.0 h1:6VeaLF9aI+MAUQ95106HwWzYZgJJpZ4stumjj6RFYAU=
 github.com/cenkalti/backoff/v4 v4.0.0/go.mod h1:eEew/i+1Q6OrCDZh3WiXYv3+nJwBASZ8Bog/87DQnVg=
 github.com/census-instrumentation/opencensus-proto v0.2.0/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
@@ -758,8 +758,8 @@ github.com/xeipuuv/gojsonschema v1.2.0/go.mod h1:anYRn/JVcOK2ZgGU+IjEV4nwlhoK5sQ
 github.com/xiang90/probing v0.0.0-20190116061207-43a291ad63a2/go.mod h1:UETIi67q53MR2AWcXfiuqkDkRtnGDLqkBTpCHuJHxtU=
 github.com/xordataexchange/crypt v0.0.3-0.20170626215501-b2862e3d0a77/go.mod h1:aYKd//L2LvnjZzWKhF00oedf4jCCReLcmhLdhm1A27Q=
 github.com/yuin/goldmark v1.1.22/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
-github.com/yuin/goldmark v1.1.26 h1:81MfIApzizD8JqKIjnWy2Vxj7GgmQUrJlh/jYWH8yGk=
-github.com/yuin/goldmark v1.1.26/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
+github.com/yuin/goldmark v1.1.27 h1:nqDD4MMMQA0lmWq03Z2/myGPYLQoXtmi0rGVs95ntbo=
+github.com/yuin/goldmark v1.1.27/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark-highlighting v0.0.0-20200307114337-60d527fdb691 h1:VWSxtAiQNh3zgHJpdpkpVYjTPqRE3P6UZCOPa1nRDio=
 github.com/yuin/goldmark-highlighting v0.0.0-20200307114337-60d527fdb691/go.mod h1:YLF3kDffRfUH/bTxOxHhV6lxwIB3Vfj91rEwNMS9MXo=
 go.etcd.io/bbolt v1.3.2 h1:Z/90sZLPOeCy2PwprqkFa25PdkusRzaj9P8zm/KNyvk=
diff --git a/modules/caddytls/acmeissuer.go b/modules/caddytls/acmeissuer.go
index 0e43046..133d007 100644
--- a/modules/caddytls/acmeissuer.go
+++ b/modules/caddytls/acmeissuer.go
@@ -17,6 +17,7 @@ package caddytls
 import (
 	"context"
 	"crypto/x509"
+	"encoding/base64"
 	"fmt"
 	"io/ioutil"
 	"net/url"
@@ -54,6 +55,10 @@ type ACMEIssuer struct {
 	// other than ACME transactions.
 	Email string `json:"email,omitempty"`
 
+	// If using an ACME CA that requires an external account
+	// binding, specify the CA-provided credentials here.
+	ExternalAccount *ExternalAccountBinding `json:"external_account,omitempty"`
+
 	// Time to wait before timing out an ACME operation.
 	ACMETimeout caddy.Duration `json:"acme_timeout,omitempty"`
 
@@ -107,12 +112,16 @@ func (m *ACMEIssuer) Provision(ctx caddy.Context) error {
 		}
 	}
 
-	m.template = m.makeIssuerTemplate()
+	var err error
+	m.template, err = m.makeIssuerTemplate()
+	if err != nil {
+		return err
+	}
 
 	return nil
 }
 
-func (m *ACMEIssuer) makeIssuerTemplate() certmagic.ACMEManager {
+func (m *ACMEIssuer) makeIssuerTemplate() (certmagic.ACMEManager, error) {
 	template := certmagic.ACMEManager{
 		CA:                m.CA,
 		Email:             m.Email,
@@ -120,6 +129,20 @@ func (m *ACMEIssuer) makeIssuerTemplate() certmagic.ACMEManager {
 		TrustedRoots:      m.rootPool,
 	}
 
+	if m.ExternalAccount != nil {
+		hmac, err := base64.StdEncoding.DecodeString(m.ExternalAccount.EncodedHMAC)
+		if err != nil {
+			return template, err
+		}
+		if m.ExternalAccount.KeyID == "" || len(hmac) == 0 {
+			return template, fmt.Errorf("when an external account binding is specified, both key ID and HMAC are required")
+		}
+		template.ExternalAccount = &certmagic.ExternalAccountBinding{
+			KeyID: m.ExternalAccount.KeyID,
+			HMAC:  hmac,
+		}
+	}
+
 	if m.Challenges != nil {
 		if m.Challenges.HTTP != nil {
 			template.DisableHTTPChallenge = m.Challenges.HTTP.Disabled
@@ -132,7 +155,7 @@ func (m *ACMEIssuer) makeIssuerTemplate() certmagic.ACMEManager {
 		template.DNSProvider = m.Challenges.DNS
 	}
 
-	return template
+	return template, nil
 }
 
 // SetConfig sets the associated certmagic config for this issuer.
@@ -201,6 +224,16 @@ type DNSProviderMaker interface {
 	NewDNSProvider() (challenge.Provider, error)
 }
 
+// ExternalAccountBinding contains information for
+// binding an external account to an ACME account.
+type ExternalAccountBinding struct {
+	// The key identifier.
+	KeyID string `json:"key_id,omitempty"`
+
+	// The base64-encoded HMAC.
+	EncodedHMAC string `json:"hmac,omitempty"`
+}
+
 // Interface guards
 var (
 	_ certmagic.PreChecker = (*ACMEIssuer)(nil)