Improve handling of errors when binary store handles bad data.

Signed-off-by: Felix Fontein <felix@fontein.de>

stores/json/store.go

@@ -42,15 +42,25 @@ func (store BinaryStore) EmitEncryptedFile(in sops.Tree) ([]byte, error) {
 	return store.store.EmitEncryptedFile(in)
 }
 
+const NOT_BINARY_HINT = ("This is likely not an encrypted binary file?" +
+	" If not, use --output-type to select the correct output type.")
+
 // EmitPlainFile produces plaintext json file's bytes from its corresponding sops.TreeBranches object
 func (store BinaryStore) EmitPlainFile(in sops.TreeBranches) ([]byte, error) {
+	if len(in) != 1 {
+		return nil, fmt.Errorf("There must be exactly one tree branch. " + NOT_BINARY_HINT)
+	}
 	// JSON stores a single object per file
 	for _, item := range in[0] {
 		if item.Key == "data" {
-			return []byte(item.Value.(string)), nil
+			if value, ok := item.Value.(string); ok {
+				return []byte(value), nil
+			} else {
+				return nil, fmt.Errorf("'data' key in tree does not have a string value. " + NOT_BINARY_HINT)
+			}
 		}
 	}
-	return nil, fmt.Errorf("No binary data found in tree")
+	return nil, fmt.Errorf("No binary data found in tree. " + NOT_BINARY_HINT)
 }
 
 // EmitValue extracts a value from a generic interface{} object representing a structured set

stores/json/store_test.go

@@ -3,8 +3,8 @@ package json
 import (
 	"testing"
 
-	"github.com/stretchr/testify/assert"
 	"github.com/getsops/sops/v3"
+	"github.com/stretchr/testify/assert"
 )
 
 func TestDecodeJSON(t *testing.T) {
@@ -320,6 +320,75 @@ func TestLoadJSONFormattedBinaryFile(t *testing.T) {
 	assert.Equal(t, "data", branches[0][0].Key)
 }
 
+func TestEmitBinaryFile(t *testing.T) {
+	store := BinaryStore{}
+	data, err := store.EmitPlainFile(sops.TreeBranches{
+		sops.TreeBranch{
+			sops.TreeItem{
+				Key:   "data",
+				Value: "foo",
+			},
+		},
+	})
+	assert.Nil(t, err)
+	assert.Equal(t, []byte("foo"), data)
+}
+
+func TestEmitBinaryFileWrongBranches(t *testing.T) {
+	store := BinaryStore{}
+	data, err := store.EmitPlainFile(sops.TreeBranches{
+		sops.TreeBranch{
+			sops.TreeItem{
+				Key:   "data",
+				Value: "bar",
+			},
+		},
+		sops.TreeBranch{
+			sops.TreeItem{
+				Key:   "data",
+				Value: "bar",
+			},
+		},
+	})
+	assert.Nil(t, data)
+	assert.Contains(t, err.Error(), "There must be exactly one tree branch")
+
+	data, err = store.EmitPlainFile(sops.TreeBranches{})
+	assert.Nil(t, data)
+	assert.Contains(t, err.Error(), "There must be exactly one tree branch")
+}
+
+func TestEmitBinaryFileNoData(t *testing.T) {
+	store := BinaryStore{}
+	data, err := store.EmitPlainFile(sops.TreeBranches{
+		sops.TreeBranch{
+			sops.TreeItem{
+				Key:   "foo",
+				Value: "bar",
+			},
+		},
+	})
+	assert.Nil(t, data)
+	assert.Contains(t, err.Error(), "No binary data found in tree")
+}
+
+func TestEmitBinaryFileWrongDataType(t *testing.T) {
+	store := BinaryStore{}
+	data, err := store.EmitPlainFile(sops.TreeBranches{
+		sops.TreeBranch{
+			sops.TreeItem{
+				Key: "data",
+				Value: sops.TreeItem{
+					Key:   "foo",
+					Value: "bar",
+				},
+			},
+		},
+	})
+	assert.Nil(t, data)
+	assert.Contains(t, err.Error(), "'data' key in tree does not have a string value")
+}
+
 func TestEmitValueString(t *testing.T) {
 	bytes, err := (&Store{}).EmitValue("hello")
 	assert.Nil(t, err)