ext4: start refactor

2 files changed, 106 insertions, 38 deletions

diff --git a/ext4/ext4.go b/ext4/ext4.go
index 401d208..7419929 100644
--- a/ext4/ext4.go
+++ b/ext4/ext4.go
@@ -1,3 +1,22 @@
+/*
+ * ext4.go - Handles command line processing for fscrypt-ext4.
+ *
+ * Copyright 2017 Google Inc.
+ * Author: Joe Richey (joerichey@google.com)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
 package main
 
 import (
@@ -34,7 +53,7 @@ Arguments:
 `
 )
 
-func printUsageAndExit(err error) {
+func printAndExit(err error, printUsage bool) {
 	var w io.Writer
 	var rc int
 	if err == nil {
@@ -46,45 +65,44 @@ func printUsageAndExit(err error) {
 		rc = 1
 		fmt.Fprintf(w, "%s: %v\n", cmdName, err)
 	}
-
-	fmt.Fprintf(w, usageFmt, cmdName)
-	fmt.Fprintln(w, "\nOptions:")
-	set.VisitAll(func(f *flag.Flag) {
-		fmt.Fprintf(w, "\t--%s\n\t\t%s\n", f.Name, f.Usage)
-	})
-	fmt.Fprintf(w, "\nSee the %s man page for more info.\n", manPage)
+	if printUsage {
+		fmt.Fprintf(w, usageFmt, cmdName)
+		fmt.Fprintln(w, "\nOptions:")
+		set.VisitAll(func(f *flag.Flag) {
+			fmt.Fprintf(w, "\t--%s\n\t\t%s\n", f.Name, f.Usage)
+		})
+		fmt.Fprintf(w, "\nSee the %s man page for more info.\n", manPage)
+	}
 	os.Exit(rc)
 }
 
 func main() {
 	set.SetOutput(ioutil.Discard)
 	if err := set.Parse(os.Args[1:]); err != nil {
-		printUsageAndExit(err)
+		printAndExit(err, true)
 	}
 	if *helpFlag {
-		printUsageAndExit(nil)
+		printAndExit(nil, true)
 	}
 	if *versionFlag {
 		fmt.Println(version)
 		return
 	}
 	if set.NArg() != 2 {
-		printUsageAndExit(fmt.Errorf("expected 2 arguments, got %d", set.NArg()))
+		printAndExit(fmt.Errorf("expected 2 arguments (got %d)", set.NArg()), true)
+	}
+
+	_, err := NewExt4Filesystem(set.Arg(1))
+	if err != nil {
+		printAndExit(err, false)
 	}
 
-	command, mountpoint := set.Arg(0), set.Arg(1)
-	switch command {
+	switch command := set.Arg(0); command {
 	case "enable":
-		fmt.Println("Enabling encryption!!")
+		fmt.Println("Enabling encryption not implemented")
 	case "disable":
-		fmt.Println("Disabling encryption!!")
+		fmt.Println("Disabling encryption not implemented")
 	default:
-		printUsageAndExit(fmt.Errorf("invalid command %q", command))
-	}
-
-	if isExt4EncryptionEnabled(mountpoint) {
-		fmt.Printf("%q has encryption\n", mountpoint)
-	} else {
-		fmt.Printf("%q doesn't have encryption\n", mountpoint)
+		printAndExit(fmt.Errorf("invalid command %q", command), true)
 	}
 }
diff --git a/ext4/feature_flag.go b/ext4/feature_flag.go
index 4c64e0a..4b588d6 100644
--- a/ext4/feature_flag.go
+++ b/ext4/feature_flag.go
@@ -1,3 +1,22 @@
+/*
+ * feature_flag.go - Changes encryption flag for an ext4 filesystem.
+ *
+ * Copyright 2017 Google Inc.
+ * Author: Joe Richey (joerichey@google.com)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
 package main
 
 /*
@@ -10,27 +29,58 @@ package main
 import "C"
 import (
 	"fmt"
-	"unsafe"
+
+	"github.com/google/fscrypt/filesystem"
 )
 
-// isExt4EncryptionEnabled returns true if the provided ext4 filesystem (as a
-// path to a device or mountpoint) has the encrypt feature flag enabled.
-func isExt4EncryptionEnabled(path string) bool {
-	cPath := C.CString(path)
-	defer C.free(unsafe.Pointer(cPath))
+// Ext4Filesystem wraps the C structures returned from libext2fs.
+type Ext4Filesystem struct {
+	ptr     C.ext2_filsys
+	mounted bool
+	retVal  C.errcode_t
+}
 
-	var fs C.ext2_filsys
-	ret := C.ext2fs_open(cPath, 0, 0, 0, C.unix_io_manager, &fs)
-	if ret != 0 {
-		panic(fmt.Errorf("Got error code %v when opening %s", ret, path))
+// NewExt4Filesystem creates a new Ext4Filesystem from a mountpoint path. Fail
+// if the path is not the mountpoint of an ext4 filesystem or cannot be opened.
+func NewExt4Filesystem(mountpoint string) (*Ext4Filesystem, error) {
+	mount, err := filesystem.FindMount(set.Arg(1))
+	if err != nil {
+		return nil, err
 	}
+	if mount.Filesystem != "ext4" {
+		err := fmt.Errorf("%q is not an ext4 filesystem (type %q)", mount.Path, mount.Filesystem)
+		return nil, err
+	}
+	if mount.Device == "" {
+		err := fmt.Errorf("underlying device for %q is invalid", mount.Filesystem)
+		return nil, err
+	}
+	return nil, nil
+}
 
-	hasEncryption := C.ext2fs_has_feature_encrypt(fs.super)
-	return hasEncryption != 0
+// HasValidBlockSize returns true if the filesystem has the same block size as
+// the system's page size.
+func (fs *Ext4Filesystem) HasValidBlockSize() bool {
+	return true
 }
 
-// enableExt4Encryption enables encryption on the filesystem at the specified
-// path.
+// IsEncryptionEnabled return true if the "encrypt" feature flag is set.
+func (fs *Ext4Filesystem) IsEncryptionEnabled() bool {
+	return C.ext2fs_has_feature_encrypt(fs.ptr.super) != 0
+}
+
+// EnableEncryption sets the "encrypt" feature flag and writes the appropriate
+// information in the superblock to allow filesystem encryption.
+func (fs *Ext4Filesystem) EnableEncryption() error {
+	return nil
+}
 
-// disableExt4Encryption disables encryption on the filesystem at the specified
-// path. Note that this operation is not supported and can cause data loss.
+// DisableEncryption removes the "encrypt" feature flag.
+func (fs *Ext4Filesystem) DisableEncryption() error {
+	return nil
+}
+
+// Close safely closes, frees, and runs cleanup f9r the filesystem.
+func (fs *Ext4Filesystem) Close() error {
+	return nil
+}