package server import ( "crypto/rand" "crypto/sha256" "encoding/json" "errors" "fmt" "io" "os" "os/user" "time" "github.com/restic/restic/backend" "github.com/restic/restic/chunker" "github.com/restic/restic/crypto" "github.com/restic/restic/debug" ) var ( // ErrNoKeyFound is returned when no key for the repository could be decrypted. ErrNoKeyFound = errors.New("no key could be found") ) // TODO: figure out scrypt values on the fly depending on the current // hardware. const ( scryptN = 65536 scryptR = 8 scryptP = 1 scryptSaltsize = 64 ) // Key represents an encrypted master key for a repository. type Key struct { Created time.Time `json:"created"` Username string `json:"username"` Hostname string `json:"hostname"` KDF string `json:"kdf"` N int `json:"N"` R int `json:"r"` P int `json:"p"` Salt []byte `json:"salt"` Data []byte `json:"data"` user *crypto.Key master *crypto.Key name string } // CreateKey initializes a master key in the given backend and encrypts it with // the password. func CreateKey(s *Server, password string) (*Key, error) { return AddKey(s, password, nil) } // OpenKey tries do decrypt the key specified by name with the given password. func OpenKey(s *Server, name string, password string) (*Key, error) { k, err := LoadKey(s, name) if err != nil { return nil, err } // check KDF if k.KDF != "scrypt" { return nil, errors.New("only supported KDF is scrypt()") } // derive user key k.user, err = crypto.KDF(k.N, k.R, k.P, k.Salt, password) if err != nil { return nil, err } // decrypt master keys buf, err := crypto.Decrypt(k.user, []byte{}, k.Data) if err != nil { return nil, err } // restore json k.master = &crypto.Key{} err = json.Unmarshal(buf, k.master) if err != nil { return nil, err } k.name = name // test if polynomial is valid and irreducible if k.master.ChunkerPolynomial == 0 { return nil, errors.New("Polynomial for content defined chunking is zero") } if !k.master.ChunkerPolynomial.Irreducible() { return nil, errors.New("Polynomial for content defined chunking is invalid") } debug.Log("OpenKey", "Master keys loaded, polynomial %v", k.master.ChunkerPolynomial) return k, nil } // SearchKey tries to decrypt all keys in the backend with the given password. // If none could be found, ErrNoKeyFound is returned. func SearchKey(s *Server, password string) (*Key, error) { // try all keys in repo done := make(chan struct{}) defer close(done) for name := range s.List(backend.Key, done) { key, err := OpenKey(s, name, password) if err != nil { continue } return key, nil } return nil, ErrNoKeyFound } // LoadKey loads a key from the backend. func LoadKey(s *Server, name string) (*Key, error) { // extract data from repo rd, err := s.be.Get(backend.Key, name) if err != nil { return nil, err } defer rd.Close() // restore json dec := json.NewDecoder(rd) k := Key{} err = dec.Decode(&k) if err != nil { return nil, err } return &k, nil } // AddKey adds a new key to an already existing repository. func AddKey(s *Server, password string, template *Key) (*Key, error) { // fill meta data about key newkey := &Key{ Created: time.Now(), KDF: "scrypt", N: scryptN, R: scryptR, P: scryptP, } hn, err := os.Hostname() if err == nil { newkey.Hostname = hn } usr, err := user.Current() if err == nil { newkey.Username = usr.Username } // generate random salt newkey.Salt = make([]byte, scryptSaltsize) n, err := rand.Read(newkey.Salt) if n != scryptSaltsize || err != nil { panic("unable to read enough random bytes for salt") } // call KDF to derive user key newkey.user, err = crypto.KDF(newkey.N, newkey.R, newkey.P, newkey.Salt, password) if err != nil { return nil, err } if template == nil { // generate new random master keys newkey.master = crypto.NewRandomKey() // generate random polynomial for cdc p, err := chunker.RandomPolynomial() if err != nil { debug.Log("AddKey", "error generating new polynomial for cdc: %v", err) return nil, err } debug.Log("AddKey", "generated new polynomial for cdc: %v", p) newkey.master.ChunkerPolynomial = p } else { // copy master keys from old key newkey.master = template.master } // encrypt master keys (as json) with user key buf, err := json.Marshal(newkey.master) if err != nil { return nil, err } newkey.Data, err = crypto.Encrypt(newkey.user, nil, buf) // dump as json buf, err = json.Marshal(newkey) if err != nil { return nil, err } // store in repository and return blob, err := s.be.Create() if err != nil { return nil, err } plainhw := backend.NewHashingWriter(blob, sha256.New()) _, err = plainhw.Write(buf) if err != nil { return nil, err } name := backend.ID(plainhw.Sum(nil)).String() err = blob.Finalize(backend.Key, name) if err != nil { return nil, err } newkey.name = name return newkey, nil } // Encrypt encrypts and signs data with the master key. Stored in ciphertext is // IV || Ciphertext || MAC. Returns the ciphertext, which is extended if // necessary. func (k *Key) Encrypt(ciphertext, plaintext []byte) ([]byte, error) { return crypto.Encrypt(k.master, ciphertext, plaintext) } // EncryptTo encrypts and signs data with the master key. The returned // io.Writer writes IV || Ciphertext || HMAC. For the hash function, SHA256 is // used. func (k *Key) EncryptTo(wr io.Writer) io.WriteCloser { return crypto.EncryptTo(k.master, wr) } // Decrypt verifes and decrypts the ciphertext with the master key. Ciphertext // must be in the form IV || Ciphertext || MAC. func (k *Key) Decrypt(plaintext, ciphertext []byte) ([]byte, error) { return crypto.Decrypt(k.master, plaintext, ciphertext) } // DecryptFrom verifies and decrypts the ciphertext read from rd and makes it // available on the returned Reader. Ciphertext must be in the form IV || // Ciphertext || MAC. In order to correctly verify the ciphertext, rd is // drained, locally buffered and made available on the returned Reader // afterwards. If an MAC verification failure is observed, it is returned // immediately. func (k *Key) DecryptFrom(rd io.Reader) (io.ReadCloser, error) { return crypto.DecryptFrom(k.master, rd) } // Master() returns the master keys for this repository. Only included for // debug purposes. func (k *Key) Master() *crypto.Key { return k.master } // User() returns the user keys for this key. Only included for debug purposes. func (k *Key) User() *crypto.Key { return k.user } func (k *Key) String() string { if k == nil { return "" } return fmt.Sprintf("", k.Username, k.Hostname, k.Created) } func (k Key) Name() string { return k.name }