Make the output of 'fscrypt status' unambiguous

Following the example of /proc/self/mountinfo, replace the space,
newline, tab, and backslash characters with octal escape sequences so
that the output can be parsed unambiguously.

3 files changed, 35 insertions, 2 deletions

diff --git a/cmd/fscrypt/status.go b/cmd/fscrypt/status.go
index 255bb2b..d10dfd8 100644
--- a/cmd/fscrypt/status.go
+++ b/cmd/fscrypt/status.go
@@ -114,8 +114,11 @@ func writeGlobalStatus(w io.Writer) error {
 			continue
 		}
 
-		fmt.Fprintf(t, "%s\t%s\t%s\t%s\t%s\n", mount.Path, mount.Device,
-			mount.FilesystemType, supportString, yesNoString(usingFscrypt))
+		fmt.Fprintf(t, "%s\t%s\t%s\t%s\t%s\n",
+			filesystem.EscapeString(mount.Path),
+			filesystem.EscapeString(mount.Device),
+			filesystem.EscapeString(mount.FilesystemType),
+			supportString, yesNoString(usingFscrypt))
 
 		if supportErr == nil {
 			supportCount++
diff --git a/filesystem/mountpoint.go b/filesystem/mountpoint.go
index 182cafa..0b0693b 100644
--- a/filesystem/mountpoint.go
+++ b/filesystem/mountpoint.go
@@ -77,6 +77,21 @@ func unescapeString(str string) string {
 	return sb.String()
 }
 
+// EscapeString is the reverse of unescapeString.  Use this to avoid injecting
+// spaces or newlines into output that uses these characters as separators.
+func EscapeString(str string) string {
+	var sb strings.Builder
+	for _, b := range []byte(str) {
+		switch b {
+		case ' ', '\t', '\n', '\\':
+			sb.WriteString(fmt.Sprintf("\\%03o", b))
+		default:
+			sb.WriteByte(b)
+		}
+	}
+	return sb.String()
+}
+
 // We get the device name via the device number rather than use the mount source
 // field directly.  This is necessary to handle a rootfs that was mounted via
 // the kernel command line, since mountinfo always shows /dev/root for that.
diff --git a/filesystem/mountpoint_test.go b/filesystem/mountpoint_test.go
index 749e5e3..99d4b55 100644
--- a/filesystem/mountpoint_test.go
+++ b/filesystem/mountpoint_test.go
@@ -179,6 +179,21 @@ func TestLoadMountWithSpecialCharacters(t *testing.T) {
 	}
 }
 
+// Tests the EscapeString() and unescapeString() functions.
+func TestStringEscaping(t *testing.T) {
+	charsNeedEscaping := " \t\n\\"
+	charsDontNeedEscaping := "ABCDEF\u2603\xff\xff\v"
+
+	orig := charsNeedEscaping + charsDontNeedEscaping
+	escaped := `\040\011\012\134` + charsDontNeedEscaping
+	if EscapeString(orig) != escaped {
+		t.Fatal("EscapeString gave wrong result")
+	}
+	if unescapeString(escaped) != orig {
+		t.Fatal("unescapeString gave wrong result")
+	}
+}
+
 // Test parsing some invalid mountinfo lines.
 func TestLoadBadMountInfo(t *testing.T) {
 	mountinfos := []string{"a",