3 files changed, 26 insertions, 6 deletions
diff --git a/internal/configfile/config_file.go b/internal/configfile/config_file.go
index c27ecd4..e4921f7 100644
--- a/internal/configfile/config_file.go
+++ b/internal/configfile/config_file.go
@@ -10,12 +10,13 @@ import (
 	"log"
 	"syscall"
 
+	"os"
+
 	"github.com/rfjakob/gocryptfs/internal/contentenc"
 	"github.com/rfjakob/gocryptfs/internal/cryptocore"
 	"github.com/rfjakob/gocryptfs/internal/exitcodes"
 	"github.com/rfjakob/gocryptfs/internal/tlog"
 )
-import "os"
 
 const (
 	// ConfDefaultName is the default configuration file name.
@@ -28,6 +29,14 @@ const (
 	ConfReverseName = ".gocryptfs.reverse.conf"
 )
 
+// FIDO2Params is a structure for storing FIDO2 parameters.
+type FIDO2Params struct {
+	// FIDO2 credential
+	CredentialID []byte
+	// FIDO2 hmac-secret salt
+	HMACSalt []byte
+}
+
 // ConfFile is the content of a config file.
 type ConfFile struct {
 	// Creator is the gocryptfs version string.
@@ -46,6 +55,8 @@ type ConfFile struct {
 	// mounting. This mechanism is analogous to the ext4 feature flags that are
 	// stored in the superblock.
 	FeatureFlags []string
+	// FIDO2 parameters
+	FIDO2 FIDO2Params
 	// Filename is the name of the config file. Not exported to JSON.
 	filename string
 }
@@ -69,7 +80,7 @@ func randBytesDevRandom(n int) []byte {
 // "password" and write it to "filename".
 // Uses scrypt with cost parameter logN.
 func Create(filename string, password []byte, plaintextNames bool,
-	logN int, creator string, aessiv bool, devrandom bool) error {
+	logN int, creator string, aessiv bool, devrandom bool, fido2CredentialID []byte, fido2HmacSalt []byte) error {
 	var cf ConfFile
 	cf.filename = filename
 	cf.Creator = creator
@@ -89,6 +100,11 @@ func Create(filename string, password []byte, plaintextNames bool,
 	if aessiv {
 		cf.FeatureFlags = append(cf.FeatureFlags, knownFlags[FlagAESSIV])
 	}
+	if len(fido2CredentialID) > 0 {
+		cf.FeatureFlags = append(cf.FeatureFlags, knownFlags[FlagFIDO2])
+		cf.FIDO2.CredentialID = fido2CredentialID
+		cf.FIDO2.HMACSalt = fido2HmacSalt
+	}
 	{
 		// Generate new random master key
 		var key []byte
diff --git a/internal/configfile/config_test.go b/internal/configfile/config_test.go
index 832867c..ce35531 100644
--- a/internal/configfile/config_test.go
+++ b/internal/configfile/config_test.go
@@ -62,7 +62,7 @@ func TestLoadV2StrangeFeature(t *testing.T) {
 }
 
 func TestCreateConfDefault(t *testing.T) {
-	err := Create("config_test/tmp.conf", testPw, false, 10, "test", false, false)
+	err := Create("config_test/tmp.conf", testPw, false, 10, "test", false, false, nil, nil)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -83,14 +83,14 @@ func TestCreateConfDefault(t *testing.T) {
 }
 
 func TestCreateConfDevRandom(t *testing.T) {
-	err := Create("config_test/tmp.conf", testPw, false, 10, "test", false, true)
+	err := Create("config_test/tmp.conf", testPw, false, 10, "test", false, true, nil, nil)
 	if err != nil {
 		t.Fatal(err)
 	}
 }
 
 func TestCreateConfPlaintextnames(t *testing.T) {
-	err := Create("config_test/tmp.conf", testPw, true, 10, "test", false, false)
+	err := Create("config_test/tmp.conf", testPw, true, 10, "test", false, false, nil, nil)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -111,7 +111,7 @@ func TestCreateConfPlaintextnames(t *testing.T) {
 
 // Reverse mode uses AESSIV
 func TestCreateConfFileAESSIV(t *testing.T) {
-	err := Create("config_test/tmp.conf", testPw, false, 10, "test", true, false)
+	err := Create("config_test/tmp.conf", testPw, false, 10, "test", true, false, nil, nil)
 	if err != nil {
 		t.Fatal(err)
 	}
diff --git a/internal/configfile/feature_flags.go b/internal/configfile/feature_flags.go
index 2d609f2..5964a53 100644
--- a/internal/configfile/feature_flags.go
+++ b/internal/configfile/feature_flags.go
@@ -25,6 +25,9 @@ const (
 	// Note that this flag does not change the password hashing algorithm
 	// which always is scrypt.
 	FlagHKDF
+	// FlagFIDO2 means that "-fido2" was used when creating the filesystem.
+	// The masterkey is protected using a FIDO2 token instead of a password.
+	FlagFIDO2
 )
 
 // knownFlags stores the known feature flags and their string representation
@@ -37,6 +40,7 @@ var knownFlags = map[flagIota]string{
 	FlagAESSIV:         "AESSIV",
 	FlagRaw64:          "Raw64",
 	FlagHKDF:           "HKDF",
+	FlagFIDO2:          "FIDO2",
 }
 
 // Filesystems that do not have these feature flags set are deprecated.