config: use --password-command to set config file password if supplied

Before this change, rclone ignored the --password-command on the
rclone config setting except when decrypting an existing config file.

This change allows for offloading the password storage/generation into
external hardware key or other protected password storage.

Fixes #7859

docs/content/docs.md

@@ -1928,7 +1928,8 @@ The default is `.partial`.
 
 This flag supplies a program which should supply the config password
 when run. This is an alternative to rclone prompting for the password
-or setting the `RCLONE_CONFIG_PASS` variable.
+or setting the `RCLONE_CONFIG_PASS` variable. It is also used when
+setting the config password for the first time.
 
 The argument to this should be a command with a space separated list
 of arguments. If one of the arguments has a space in then enclose it

fs/config/config_test.go

@@ -10,6 +10,10 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
+func init() {
+	configfile.Install()
+}
+
 func TestConfigLoad(t *testing.T) {
 	oldConfigPath := config.GetConfigPath()
 	assert.NoError(t, config.SetConfigPath("./testdata/plain.conf"))
@@ -17,7 +21,6 @@ func TestConfigLoad(t *testing.T) {
 		assert.NoError(t, config.SetConfigPath(oldConfigPath))
 	}()
 	config.ClearConfigPassword()
-	configfile.Install()
 	sections := config.Data().GetSectionList()
 	var expect = []string{"RCLONE_ENCRYPT_V0", "nounc", "unc"}
 	assert.Equal(t, expect, sections)

fs/config/crypt.go

@@ -310,8 +310,20 @@ func ClearConfigPassword() {
 // changeConfigPassword will query the user twice
 // for a password. If the same password is entered
 // twice the key is updated.
+//
+// This will use --password-command if configured to read the password.
 func changeConfigPassword() {
-	err := SetConfigPassword(ChangePassword("NEW configuration"))
+	pass, err := GetPasswordCommand(context.Background())
+	if err != nil {
+		fmt.Printf("Failed to read new password with --password-command: %v\n", err)
+		return
+	}
+	if pass == "" {
+		pass = ChangePassword("NEW configuration")
+	} else {
+		fmt.Printf("Read password using --password-command\n")
+	}
+	err = SetConfigPassword(pass)
 	if err != nil {
 		fmt.Printf("Failed to set config password: %v\n", err)
 		return

fs/config/crypt_internal_test.go

@@ -1,8 +1,10 @@
 package config
 
 import (
+	"context"
 	"testing"
 
+	"github.com/rclone/rclone/fs"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -46,3 +48,32 @@ func TestPassword(t *testing.T) {
 	hashedKeyCompare(t, "abcdef", "ABCDEF", false)
 
 }
+
+func TestChangeConfigPassword(t *testing.T) {
+	ci := fs.GetConfig(context.Background())
+
+	var err error
+	oldConfigPath := GetConfigPath()
+	assert.NoError(t, SetConfigPath("./testdata/encrypted.conf"))
+	defer func() {
+		assert.NoError(t, SetConfigPath(oldConfigPath))
+		ClearConfigPassword()
+		ci.PasswordCommand = nil
+	}()
+
+	// Get rid of any config password
+	ClearConfigPassword()
+
+	// Set correct password using --password command
+	ci.PasswordCommand = fs.SpaceSepList{"echo", "asdf"}
+	changeConfigPassword()
+	err = Data().Load()
+	require.NoError(t, err)
+	sections := Data().GetSectionList()
+	var expect = []string{"nounc", "unc"}
+	assert.Equal(t, expect, sections)
+
+	keys := Data().GetKeyList("nounc")
+	expect = []string{"type", "nounc"}
+	assert.Equal(t, expect, keys)
+}