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/*
* context.go - top-level interface to fscrypt packages
*
* 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 is the high-level interface to the fscrypt packages. The
// functions here roughly correspond with commands for the tool in cmd/fscrypt.
// All of the actions include a significant amount of logging, so that good
// output can be provided for cmd/fscrypt's verbose mode.
// The top-level actions currently include:
// - Creating a new config file
// - Creating a context on which to perform actions
// - Creating, unlocking, and modifying Protectors
// - Creating, unlocking, and modifying Policies
package actions
import (
"log"
"os/user"
"golang.org/x/sys/unix"
"github.com/pkg/errors"
"github.com/google/fscrypt/filesystem"
"github.com/google/fscrypt/metadata"
"github.com/google/fscrypt/util"
)
// Errors relating to Config files or Config structures.
var (
ErrNoConfigFile = errors.New("global config file does not exist")
ErrBadConfigFile = errors.New("global config file has invalid data")
ErrConfigFileExists = errors.New("global config file already exists")
ErrBadConfig = errors.New("invalid Config structure provided")
ErrLocked = errors.New("key needs to be unlocked first")
)
// Context contains the necessary global state to perform most of fscrypt's
// actions.
type Context struct {
// Config is the struct loaded from the global config file. It can be
// modified after being loaded to customise parameters.
Config *metadata.Config
// Mount is the filesystem relitive to which all Protectors and Policies
// are added, edited, removed, and applied.
Mount *filesystem.Mount
// TargetUser is the user for which protectors are created and to whose
// keyring policies are provisioned.
TargetUser *user.User
}
// NewContextFromPath makes a context for the filesystem containing the
// specified path and whose Config is loaded from the global config file. On
// success, the Context contains a valid Config and Mount. The target defaults
// the the current effective user if none is specified.
func NewContextFromPath(path string, target *user.User) (*Context, error) {
ctx, err := newContextFromUser(target)
if err != nil {
return nil, err
}
if ctx.Mount, err = filesystem.FindMount(path); err != nil {
return nil, err
}
log.Printf("%s is on %s filesystem %q (%s)", path,
ctx.Mount.Filesystem, ctx.Mount.Path, ctx.Mount.Device)
return ctx, nil
}
// NewContextFromMountpoint makes a context for the filesystem at the specified
// mountpoint and whose Config is loaded from the global config file. On
// success, the Context contains a valid Config and Mount. The target defaults
// the the current effective user if none is specified.
func NewContextFromMountpoint(mountpoint string, target *user.User) (*Context, error) {
ctx, err := newContextFromUser(target)
if err != nil {
return nil, err
}
if ctx.Mount, err = filesystem.GetMount(mountpoint); err != nil {
return nil, err
}
log.Printf("found %s filesystem %q (%s)", ctx.Mount.Filesystem,
ctx.Mount.Path, ctx.Mount.Device)
return ctx, nil
}
// newContextFromUser makes a context with the corresponding target user, and
// whose Config is loaded from the global config file. If the target is nil, the
// effective user is used.
func newContextFromUser(target *user.User) (*Context, error) {
var err error
if target == nil {
target = util.CurrentUser()
}
ctx := &Context{TargetUser: target}
if ctx.Config, err = getConfig(); err != nil {
return nil, err
}
log.Printf("creating context for %q", target.Username)
return ctx, nil
}
// checkContext verifies that the context contains an valid config and a mount
// which is being used with fscrypt.
func (ctx *Context) checkContext() error {
if err := ctx.Config.CheckValidity(); err != nil {
return errors.Wrap(ErrBadConfig, err.Error())
}
return ctx.Mount.CheckSetup()
}
// getService returns the keyring service for this context. We use the presence
// of the LegacyConfig flag to determine if we should use the legacy services.
// For ext4 systems before v4.8 and f2fs systems before v4.6, filesystem
// specific services must be used (these legacy services will still work with
// later kernels).
func (ctx *Context) getService() string {
// For legacy configurations, we may need non-standard services
if ctx.Config.HasCompatibilityOption(LegacyConfig) {
switch ctx.Mount.Filesystem {
case "ext4", "f2fs":
return ctx.Mount.Filesystem + ":"
}
}
return unix.FS_KEY_DESC_PREFIX
}
// getProtectorOption returns the ProtectorOption for the protector on the
// context's mountpoint with the specified descriptor.
func (ctx *Context) getProtectorOption(protectorDescriptor string) *ProtectorOption {
mnt, data, err := ctx.Mount.GetProtector(protectorDescriptor)
if err != nil {
return &ProtectorOption{ProtectorInfo{}, nil, err}
}
info := ProtectorInfo{data}
// No linked path if on the same mountpoint
if mnt == ctx.Mount {
return &ProtectorOption{info, nil, nil}
}
return &ProtectorOption{info, mnt, nil}
}
// ProtectorOptions creates a slice of all the options for all of the Protectors
// on the Context's mountpoint.
func (ctx *Context) ProtectorOptions() ([]*ProtectorOption, error) {
if err := ctx.checkContext(); err != nil {
return nil, err
}
descriptors, err := ctx.Mount.ListProtectors()
if err != nil {
return nil, err
}
options := make([]*ProtectorOption, len(descriptors))
for i, descriptor := range descriptors {
options[i] = ctx.getProtectorOption(descriptor)
}
return options, nil
}
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