actions: generate a config file for fscrypt

This commit adds in the actions package. This package will be the
highest-level interface to the fscrypt packages. The public functions
in this package will be called directly from cmd/fscrypt.

The actions added in this commit pertain to creating and reading the
fscrypt global config file "fscrypt.conf". The challenging part about
creating this file is finding the correct hashing parameters for the
desired time target.

The getHashingCosts() function finds the desired costs by doubling the
costs and running the passphrase hash until the target is exceeded.
Then, a cost estimate is obtained using a linear interpolation between
the last two costs (and their time results).

Change-Id: I4a0eaf4856ec4ff49eb4360da3267f7caa9d07b2

1 files changed, 76 insertions, 0 deletions

diff --git a/actions/context_test.go b/actions/context_test.go
new file mode 100644
index 0000000..671b065
--- /dev/null
+++ b/actions/context_test.go
@@ -0,0 +1,76 @@
+/*
+ * config_test.go - tests for creating new contexts
+ *
+ * Copyright 2017 Google Inc.
+ * Author: Joe Richey (joerichey@google.com)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package actions
+
+import (
+	"os"
+	"testing"
+
+	"fscrypt/filesystem"
+)
+
+var mountpoint = os.Getenv("TEST_FILESYSTEM_ROOT")
+
+// Makes a context using the testing locations for the filesystem and
+// configuration file.
+func makeContext() (*Context, error) {
+	if err := NewConfigFile(testTime, true); err != nil {
+		return nil, err
+	}
+
+	mnt := filesystem.Mount{Path: mountpoint}
+	if err := mnt.Setup(); err != nil {
+		return nil, err
+	}
+
+	return NewContextFromMountpoint(mountpoint)
+}
+
+// Cleans up the testing config file and testing filesystem data.
+func cleaupContext() {
+	os.RemoveAll(ConfigFileLocation)
+	mnt := filesystem.Mount{Path: mountpoint}
+	mnt.RemoveAllMetadata()
+}
+
+// Tests that we can create a context
+func TestSetupContext(t *testing.T) {
+	_, err := makeContext()
+	defer cleaupContext()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+}
+
+// Tests that we cannot create a context without a config file.
+func TestNoConfigFile(t *testing.T) {
+	mnt := filesystem.Mount{Path: mountpoint}
+	if err := mnt.Setup(); err != nil {
+		t.Fatal(err)
+	}
+
+	_, err := NewContextFromMountpoint(mountpoint)
+	defer cleaupContext()
+
+	if err == nil {
+		t.Error("should not be able to create context without config file")
+	}
+}