105 lines
2.1 KiB
Go
105 lines
2.1 KiB
Go
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package cryptfs
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import (
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"errors"
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"io/ioutil"
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"encoding/json"
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)
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import "os"
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const (
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// Changing this string breaks backward compatability
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testBlockData = "gocryptfs test block"
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// The dot "." is not used in base64url (RFC4648), hence
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// we can never clash with an encrypted file.
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ConfDefaultName = "gocryptfs.conf"
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)
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type confFile struct {
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// File the config is saved in. Lowercase => not exported to JSON.
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filename string
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// Unencrypted AES key
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Key [16]byte
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// GCM ciphertext with auth tag to verify the key is correct
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TestBlock []byte
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}
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// CreateConfFile - create a new config file with "key" and write to "filename"
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func CreateConfFile(filename string, key [16]byte) error {
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var cf confFile
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cf.filename = filename
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cf.Key = key
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// Generate test block
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cfs := NewCryptFS(cf.Key, false)
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cf.TestBlock = cfs.EncryptBlock([]byte(testBlockData))
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// Write file to disk
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err := cf.WriteFile()
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return err
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}
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// LoadConfFile - read config file from disk and verify the key using the
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// embedded TestBlock
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func LoadConfFile(filename string) (*confFile, error) {
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// Read from disk
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js, err := ioutil.ReadFile(filename)
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if err != nil {
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return nil, err
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}
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var cf confFile
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err = json.Unmarshal(js, &cf)
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if err != nil {
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return nil, err
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}
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cf.filename = filename
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// Try to decrypt the test block to see if the key is correct
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//
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// Speed does not matter here. Use built-in crypto.
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cfs := NewCryptFS(cf.Key, false)
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d, err := cfs.DecryptBlock(cf.TestBlock)
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if err != nil {
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return nil, err
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}
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ds := string(d)
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if ds != testBlockData {
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return nil, errors.New("Invalid test block content: " + ds)
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}
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return &cf, nil
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}
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// WriteFile - write out config in JSON format to file "filename.tmp"
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// then rename over "filename"
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func (cf *confFile) WriteFile() error {
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tmp := cf.filename + ".tmp"
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fd, err := os.Create(tmp)
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if err != nil {
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return err
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}
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js, err := json.Marshal(cf)
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if err != nil {
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return err
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}
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_, err = fd.Write(js)
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if err != nil {
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return err
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}
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err = fd.Sync()
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if err != nil {
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return err
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}
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err = fd.Close()
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if err != nil {
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return err
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}
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err = os.Rename(tmp, cf.filename)
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if err != nil {
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return err
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}
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return nil
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}
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