Add constellation node state

Signed-off-by: Malte Poll <mp@edgeless.systems>

coordinator/nodestate/nodestate.go

@@ -0,0 +1,31 @@
+package nodestate
+
+import (
+	"fmt"
+
+	"github.com/edgelesssys/constellation/cli/file"
+	"github.com/edgelesssys/constellation/coordinator/role"
+)
+
+const nodeStatePath = "/run/state/constellation/node_state.json"
+
+// NodeState is the state of a constellation node that is required to recover from a reboot.
+// Can be persisted to disk and reloaded later.
+type NodeState struct {
+	Role       role.Role
+	VPNPrivKey []byte
+}
+
+// FromFile reads a NodeState from disk.
+func FromFile(fileHandler file.Handler) (*NodeState, error) {
+	nodeState := &NodeState{}
+	if err := fileHandler.ReadJSON(nodeStatePath, nodeState); err != nil {
+		return nil, fmt.Errorf("could not load node state: %w", err)
+	}
+	return nodeState, nil
+}
+
+// ToFile writes a NodeState to disk.
+func (nodeState *NodeState) ToFile(fileHandler file.Handler) error {
+	return fileHandler.WriteJSON(nodeStatePath, nodeState, false)
+}

coordinator/nodestate/nodestate_test.go

@@ -0,0 +1,100 @@
+package nodestate
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/edgelesssys/constellation/cli/file"
+	"github.com/edgelesssys/constellation/coordinator/role"
+	"github.com/spf13/afero"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestFromFile(t *testing.T) {
+	testCases := map[string]struct {
+		fileContents  string
+		expectedState *NodeState
+		errExpected   bool
+	}{
+		"nodestate exists": {
+			fileContents: `{	"Role": "Coordinator",	"VPNPrivKey": "dGVzdA=="	}`,
+			expectedState: &NodeState{
+				Role:       role.Coordinator,
+				VPNPrivKey: []byte("test"),
+			},
+		},
+		"nodestate file does not exist": {
+			errExpected: true,
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			assert := assert.New(t)
+			require := require.New(t)
+
+			fs := afero.NewMemMapFs()
+			if tc.fileContents != "" {
+				require.NoError(fs.MkdirAll(filepath.Dir(nodeStatePath), 0o755))
+				require.NoError(afero.WriteFile(fs, nodeStatePath, []byte(tc.fileContents), 0o644))
+			}
+			fileHandler := file.NewHandler(fs)
+			state, err := FromFile(fileHandler)
+			if tc.errExpected {
+				assert.Error(err)
+				return
+			}
+			require.NoError(err)
+			assert.Equal(tc.expectedState, state)
+		})
+	}
+}
+
+func TestToFile(t *testing.T) {
+	testCases := map[string]struct {
+		precreateFile bool
+		state         *NodeState
+		expectedFile  string
+		errExpected   bool
+	}{
+		"writing works": {
+			state: &NodeState{
+				Role:       role.Coordinator,
+				VPNPrivKey: []byte("test"),
+			},
+			expectedFile: `{
+	"Role": "Coordinator",
+	"VPNPrivKey": "dGVzdA=="
+}`,
+		},
+		"file exists already": {
+			precreateFile: true,
+			errExpected:   true,
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			assert := assert.New(t)
+			require := require.New(t)
+
+			fs := afero.NewMemMapFs()
+			require.NoError(fs.MkdirAll(filepath.Dir(nodeStatePath), 0o755))
+			if tc.precreateFile {
+				require.NoError(afero.WriteFile(fs, nodeStatePath, []byte("pre-existing"), 0o644))
+			}
+			fileHandler := file.NewHandler(fs)
+			err := tc.state.ToFile(fileHandler)
+			if tc.errExpected {
+				assert.Error(err)
+				return
+			}
+			require.NoError(err)
+
+			fileContents, err := afero.ReadFile(fs, nodeStatePath)
+			require.NoError(err)
+			assert.Equal(tc.expectedFile, string(fileContents))
+		})
+	}
+}