Validator key files: allow symlinks (#5679)

* traverse symlinks
* Merge branch 'master' into account-keys-symlinks
* unit test
* Merge branch 'account-keys-symlinks' of github.com:prysmaticlabs/prysm into account-keys-symlinks
* Merge refs/heads/master into account-keys-symlinks
* removes unncecessary line
* Merge branch 'account-keys-symlinks' of github.com:prysmaticlabs/prysm into account-keys-symlinks
* fixes tests
* better teardown of resources

shared/keystore/keystore.go

@@ -28,6 +28,7 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
+	"os"
 	"path/filepath"
 	"strings"
 
@@ -96,6 +97,15 @@ func (ks Store) GetKeys(directory, fileprefix, password string, warnOnFail bool)
 		n := f.Name()
 		filePath := filepath.Join(directory, n)
 		filePath = filepath.Clean(filePath)
+		if f.Mode()&os.ModeSymlink == os.ModeSymlink {
+			if targetFilePath, err := filepath.EvalSymlinks(filePath); err == nil {
+				filePath = targetFilePath
+				// Override link stats with target file's stats.
+				if f, err = os.Stat(filePath); err != nil {
+					return nil, err
+				}
+			}
+		}
 		cp := strings.Contains(n, strings.TrimPrefix(fileprefix, "/"))
 		if f.Mode().IsRegular() && cp {
 			// #nosec G304

shared/keystore/keystore_test.go

@@ -122,3 +122,42 @@ func TestEncryptDecryptKey(t *testing.T) {
 	}
 
 }
+
+func TestGetSymlinkedKeys(t *testing.T) {
+	tmpdir := testutil.TempDir() + "/symlinked-keystore"
+	defer func() {
+		if err := os.RemoveAll(tmpdir); err != nil {
+			t.Logf("unable to remove temporary files: %v", err)
+		}
+	}()
+	ks := &Store{
+		scryptN: LightScryptN,
+		scryptP: LightScryptP,
+	}
+
+	key, err := NewKey()
+	if err != nil {
+		t.Fatalf("key generation failed %v", err)
+	}
+
+	if err := ks.StoreKey(tmpdir+"/files/test-1", key, "password"); err != nil {
+		t.Fatalf("unable to store key %v", err)
+	}
+
+	if err := os.Symlink(tmpdir+"/files/test-1", tmpdir+"/test-1"); err != nil {
+		t.Fatalf("unable to create symlink: %v", err)
+	}
+
+	newkeys, err := ks.GetKeys(tmpdir, "test", "password", false)
+	if err != nil {
+		t.Fatalf("unable to get key %v", err)
+	}
+	if len(newkeys) != 1 {
+		t.Errorf("unexpected number of keys returned, want: %d, got: %d", 1, len(newkeys))
+	}
+	for _, s := range newkeys {
+		if !bytes.Equal(s.SecretKey.Marshal(), key.SecretKey.Marshal()) {
+			t.Fatalf("retrieved secret keys are not equal %v ", s.SecretKey.Marshal())
+		}
+	}
+}