From e62e4f32d68c933168a0ff83114facce4b73d223 Mon Sep 17 00:00:00 2001
From: Jan-Lukas Else <mail@jlelse.de>
Date: Thu, 29 Jul 2021 15:31:49 +0200
Subject: [PATCH] Automatic ActivityPub key generation, doesn't need config
 anymore

---
 activityPub.go      | 49 ++++++++++++++++++++++++++++++++++++---------
 activityPub_test.go | 44 ++++++++++++++++++++++++++++++++++++++++
 config.go           |  2 --
 example-config.yml  |  2 ++
 4 files changed, 85 insertions(+), 12 deletions(-)
 create mode 100644 activityPub_test.go

diff --git a/activityPub.go b/activityPub.go
index d50ab37..419b252 100644
--- a/activityPub.go
+++ b/activityPub.go
@@ -1,6 +1,8 @@
 package main
 
 import (
+	"crypto/rand"
+	"crypto/rsa"
 	"crypto/x509"
 	"database/sql"
 	"encoding/json"
@@ -11,7 +13,6 @@ import (
 	"log"
 	"net/http"
 	"net/url"
-	"os"
 	"strings"
 	"time"
 
@@ -54,15 +55,7 @@ func (a *goBlog) initActivityPub() error {
 		a.webfingerAccts[a.apIri(blog)] = acct
 	}
 	// Read key and prepare signing
-	pkfile, err := os.ReadFile(a.cfg.ActivityPub.KeyPath)
-	if err != nil {
-		return err
-	}
-	privateKeyDecoded, _ := pem.Decode(pkfile)
-	if privateKeyDecoded == nil {
-		return errors.New("failed to decode private key")
-	}
-	a.apPrivateKey, err = x509.ParsePKCS1PrivateKey(privateKeyDecoded.Bytes)
+	err := a.loadActivityPubPrivateKey()
 	if err != nil {
 		return err
 	}
@@ -422,3 +415,39 @@ func (a *goBlog) apIri(b *configBlog) string {
 func apRequestIsSuccess(code int) bool {
 	return code == http.StatusOK || code == http.StatusCreated || code == http.StatusAccepted || code == http.StatusNoContent
 }
+
+// Load or generate key for ActivityPub communication
+func (a *goBlog) loadActivityPubPrivateKey() error {
+	// Check if already loaded
+	if a.apPrivateKey != nil {
+		return nil
+	}
+	// Check if already generated
+	if keyData, err := a.db.retrievePersistentCache("activitypub_key"); err == nil && keyData != nil {
+		privateKeyDecoded, _ := pem.Decode(keyData)
+		if privateKeyDecoded == nil {
+			log.Println("failed to decode cached private key")
+			// continue
+		} else {
+			key, err := x509.ParsePKCS1PrivateKey(privateKeyDecoded.Bytes)
+			if err == nil && key != nil {
+				a.apPrivateKey = key
+				return nil
+			}
+		}
+	}
+	// Generate and cache key
+	key, err := rsa.GenerateKey(rand.Reader, 2048)
+	if err != nil {
+		return err
+	}
+	encodedKey := x509.MarshalPKCS1PrivateKey(key)
+	pemEncoded := pem.EncodeToMemory(&pem.Block{Type: "PRIVATE KEY", Bytes: encodedKey})
+	err = a.db.cachePersistently("activitypub_key", pemEncoded)
+	if err != nil {
+		return err
+	}
+	a.apPrivateKey = key
+	// Return key
+	return nil
+}
diff --git a/activityPub_test.go b/activityPub_test.go
new file mode 100644
index 0000000..c4121a0
--- /dev/null
+++ b/activityPub_test.go
@@ -0,0 +1,44 @@
+package main
+
+import (
+	"crypto/x509"
+	"encoding/pem"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func Test_loadActivityPubPrivateKey(t *testing.T) {
+
+	app := &goBlog{
+		cfg: &config{
+			Db: &configDb{
+				File: filepath.Join(t.TempDir(), "test.db"),
+			},
+		},
+	}
+	_ = app.initDatabase(false)
+
+	// Generate
+	err := app.loadActivityPubPrivateKey()
+	require.NoError(t, err)
+
+	assert.NotNil(t, app.apPrivateKey)
+
+	oldEncodedKey := x509.MarshalPKCS1PrivateKey(app.apPrivateKey)
+	oldPemEncoded := pem.EncodeToMemory(&pem.Block{Type: "PRIVATE KEY", Bytes: oldEncodedKey})
+
+	// Reset and reload
+	err = app.loadActivityPubPrivateKey()
+	require.NoError(t, err)
+
+	assert.NotNil(t, app.apPrivateKey)
+
+	newEncodedKey := x509.MarshalPKCS1PrivateKey(app.apPrivateKey)
+	newPemEncoded := pem.EncodeToMemory(&pem.Block{Type: "PRIVATE KEY", Bytes: newEncodedKey})
+
+	assert.Equal(t, string(oldPemEncoded), string(newPemEncoded))
+
+}
diff --git a/config.go b/config.go
index 4b1994d..0f73cfa 100644
--- a/config.go
+++ b/config.go
@@ -232,7 +232,6 @@ type configRegexRedirect struct {
 
 type configActivityPub struct {
 	Enabled        bool     `mapstructure:"enabled"`
-	KeyPath        string   `mapstructure:"keyPath"`
 	TagsTaxonomies []string `mapstructure:"tagsTaxonomies"`
 }
 
@@ -288,7 +287,6 @@ func (a *goBlog) initConfig() error {
 	viper.SetDefault("micropub.photoParam", "images")
 	viper.SetDefault("micropub.photoDescriptionParam", "imagealts")
 	viper.SetDefault("micropub.locationParam", "location")
-	viper.SetDefault("activityPub.keyPath", "data/private.pem")
 	viper.SetDefault("activityPub.tagsTaxonomies", []string{"tags"})
 	// Unmarshal config
 	a.cfg = &config{}
diff --git a/example-config.yml b/example-config.yml
index ff9e8d5..02d6451 100644
--- a/example-config.yml
+++ b/example-config.yml
@@ -69,6 +69,8 @@ hooks:
 # ActivityPub
 activityPub:
   enabled: true # Enable ActivityPub
+  tagsTaxonomies: # Post taxonomies to use as "Hashtags"
+    - tags
 
 # Webmention
 webmention: