Detect integrity file system request

Signed-off-by: Daniel Weiße <dw@edgeless.systems>

mount/cryptmapper/cryptmapper.go

@@ -7,6 +7,7 @@ import (
 	"io/fs"
 	"os"
 	"path/filepath"
+	"strings"
 	"sync"
 
 	cryptsetup "github.com/martinjungblut/go-cryptsetup"
@@ -18,6 +19,7 @@ import (
 const (
 	cryptPrefix       = "/dev/mapper/"
 	integritySuffix   = "_dif"
+	integrityFSSuffix = "-integrity"
 	keySizeIntegrity  = 96
 	keySizeCrypt      = 64
 )
@@ -311,3 +313,12 @@ func performWipe(device DeviceMapper, volumeID, dek string) error {
 	klog.V(4).Info("dm-integrity successfully initiated")
 	return nil
 }
+
+// IsIntegrityFS checks if the fstype string contains an integrity suffix.
+// If yes, returns the trimmed fstype and true, fstype and false otherwise.
+func IsIntegrityFS(fstype string) (string, bool) {
+	if strings.HasSuffix(fstype, integrityFSSuffix) {
+		return strings.TrimSuffix(fstype, integrityFSSuffix), true
+	}
+	return fstype, false
+}

mount/cryptmapper/cryptmapper_test.go

@@ -231,3 +231,48 @@ func TestOpenCryptDevice(t *testing.T) {
 	_, err := mapper.OpenCryptDevice(context.Background(), "/dev/some-device", "volume01", false)
 	assert.NoError(t, err)
 }
+
+func TestIsIntegrityFS(t *testing.T) {
+	testCases := map[string]struct {
+		wantIntegrity bool
+		fstype        string
+	}{
+		"plain ext4": {
+			wantIntegrity: false,
+			fstype:        "ext4",
+		},
+		"integrity ext4": {
+			wantIntegrity: true,
+			fstype:        "ext4",
+		},
+		"integrity fs": {
+			wantIntegrity: false,
+			fstype:        "integrity",
+		},
+		"double integrity": {
+			wantIntegrity: true,
+			fstype:        "ext4-integrity",
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			assert := assert.New(t)
+
+			request := tc.fstype
+			if tc.wantIntegrity {
+				request = tc.fstype + integrityFSSuffix
+			}
+
+			fstype, isIntegrity := IsIntegrityFS(request)
+
+			if tc.wantIntegrity {
+				assert.True(isIntegrity)
+				assert.Equal(tc.fstype, fstype)
+			} else {
+				assert.False(isIntegrity)
+				assert.Equal(tc.fstype, fstype)
+			}
+		})
+	}
+}