Dynamic grpc client credentials (#204)

* Add an aTLS wrapper for grpc credentials

* Move grpc dialers to internal and use aTLS grpc credentials

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

internal/grpc/dialer/dialer_test.go

@@ -0,0 +1,102 @@
+package dialer
+
+import (
+	"context"
+	"testing"
+
+	"github.com/edgelesssys/constellation/coordinator/core"
+	"github.com/edgelesssys/constellation/internal/grpc/atlscredentials"
+	"github.com/edgelesssys/constellation/internal/grpc/testdialer"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/test/grpc_testing"
+)
+
+func TestDial(t *testing.T) {
+	testCases := map[string]struct {
+		tls     bool
+		dialFn  func(dialer *Dialer, ctx context.Context, target string) (*grpc.ClientConn, error)
+		wantErr bool
+	}{
+		"Dial with tls on server works": {
+			tls: true,
+			dialFn: func(dialer *Dialer, ctx context.Context, target string) (*grpc.ClientConn, error) {
+				return dialer.Dial(ctx, target)
+			},
+		},
+		"Dial without tls on server fails": {
+			dialFn: func(dialer *Dialer, ctx context.Context, target string) (*grpc.ClientConn, error) {
+				return dialer.Dial(ctx, target)
+			},
+			wantErr: true,
+		},
+		"DialNoVerify with tls on server works": {
+			tls: true,
+			dialFn: func(dialer *Dialer, ctx context.Context, target string) (*grpc.ClientConn, error) {
+				return dialer.DialNoVerify(ctx, target)
+			},
+		},
+		"DialNoVerify without tls on server fails": {
+			dialFn: func(dialer *Dialer, ctx context.Context, target string) (*grpc.ClientConn, error) {
+				return dialer.DialNoVerify(ctx, target)
+			},
+			wantErr: true,
+		},
+		"DialInsecure without tls on server works": {
+			dialFn: func(dialer *Dialer, ctx context.Context, target string) (*grpc.ClientConn, error) {
+				return dialer.DialInsecure(ctx, target)
+			},
+		},
+		"DialInsecure with tls on server fails": {
+			tls: true,
+			dialFn: func(dialer *Dialer, ctx context.Context, target string) (*grpc.ClientConn, error) {
+				return dialer.DialInsecure(ctx, target)
+			},
+			wantErr: true,
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			assert := assert.New(t)
+			require := require.New(t)
+
+			netDialer := testdialer.NewBufconnDialer()
+			dialer := New(nil, &core.MockValidator{}, netDialer)
+			server := newServer(tc.tls)
+			api := &testAPI{}
+			grpc_testing.RegisterTestServiceServer(server, api)
+			go server.Serve(netDialer.GetListener("192.0.2.1:1234"))
+			defer server.Stop()
+			conn, err := tc.dialFn(dialer, context.Background(), "192.0.2.1:1234")
+			require.NoError(err)
+			defer conn.Close()
+
+			client := grpc_testing.NewTestServiceClient(conn)
+			_, err = client.EmptyCall(context.Background(), &grpc_testing.Empty{})
+
+			if tc.wantErr {
+				assert.Error(err)
+				return
+			}
+			require.NoError(err)
+		})
+	}
+}
+
+func newServer(tls bool) *grpc.Server {
+	if tls {
+		creds := atlscredentials.New(&core.MockIssuer{}, nil)
+		return grpc.NewServer(grpc.Creds(creds))
+	}
+	return grpc.NewServer()
+}
+
+type testAPI struct {
+	grpc_testing.UnimplementedTestServiceServer
+}
+
+func (s *testAPI) EmptyCall(ctx context.Context, in *grpc_testing.Empty) (*grpc_testing.Empty, error) {
+	return &grpc_testing.Empty{}, nil
+}