package repository import ( "bytes" "context" "encoding/json" "fmt" "os" "os/user" "time" "github.com/restic/restic/internal/errors" "github.com/restic/restic/internal/restic" "github.com/restic/restic/internal/backend" "github.com/restic/restic/internal/crypto" "github.com/restic/restic/internal/debug" ) var ( // ErrNoKeyFound is returned when no key for the repository could be decrypted. ErrNoKeyFound = errors.Fatal("wrong password or no key found") // ErrMaxKeysReached is returned when the maximum number of keys was checked and no key could be found. ErrMaxKeysReached = errors.Fatal("maximum number of keys reached") ) // 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 } // Params tracks the parameters used for the KDF. If not set, it will be // calibrated on the first run of AddKey(). var Params *crypto.Params var ( // KDFTimeout specifies the maximum runtime for the KDF. KDFTimeout = 500 * time.Millisecond // KDFMemory limits the memory the KDF is allowed to use. KDFMemory = 60 ) // createMasterKey creates a new master key in the given backend and encrypts // it with the password. func createMasterKey(s *Repository, password string) (*Key, error) { return AddKey(context.TODO(), s, password, nil) } // OpenKey tries do decrypt the key specified by name with the given password. func OpenKey(ctx context.Context, s *Repository, name string, password string) (*Key, error) { k, err := LoadKey(ctx, s, name) if err != nil { debug.Log("LoadKey(%v) returned error %v", name, err) return nil, err } // check KDF if k.KDF != "scrypt" { return nil, errors.New("only supported KDF is scrypt()") } // derive user key params := crypto.Params{ N: k.N, R: k.R, P: k.P, } k.user, err = crypto.KDF(params, k.Salt, password) if err != nil { return nil, errors.Wrap(err, "crypto.KDF") } // decrypt master keys nonce, ciphertext := k.Data[:k.user.NonceSize()], k.Data[k.user.NonceSize():] buf, err := k.user.Open(nil, nonce, ciphertext, nil) if err != nil { return nil, err } // restore json k.master = &crypto.Key{} err = json.Unmarshal(buf, k.master) if err != nil { debug.Log("Unmarshal() returned error %v", err) return nil, errors.Wrap(err, "Unmarshal") } k.name = name if !k.Valid() { return nil, errors.New("Invalid key for repository") } return k, nil } // SearchKey tries to decrypt at most maxKeys keys in the backend with the // given password. If none could be found, ErrNoKeyFound is returned. When // maxKeys is reached, ErrMaxKeysReached is returned. When setting maxKeys to // zero, all keys in the repo are checked. func SearchKey(ctx context.Context, s *Repository, password string, maxKeys int) (*Key, error) { checked := 0 // try at most maxKeysForSearch keys in repo for name := range s.Backend().List(ctx, restic.KeyFile) { if maxKeys > 0 && checked > maxKeys { return nil, ErrMaxKeysReached } debug.Log("trying key %q", name) key, err := OpenKey(ctx, s, name, password) if err != nil { debug.Log("key %v returned error %v", name, err) // ErrUnauthenticated means the password is wrong, try the next key if errors.Cause(err) == crypto.ErrUnauthenticated { continue } if err != nil { debug.Log("unable to open key %v: %v\n", err) continue } } debug.Log("successfully opened key %v", name) return key, nil } return nil, ErrNoKeyFound } // LoadKey loads a key from the backend. func LoadKey(ctx context.Context, s *Repository, name string) (k *Key, err error) { h := restic.Handle{Type: restic.KeyFile, Name: name} data, err := backend.LoadAll(ctx, s.be, h) if err != nil { return nil, err } k = &Key{} err = json.Unmarshal(data, k) if err != nil { return nil, errors.Wrap(err, "Unmarshal") } return k, nil } // AddKey adds a new key to an already existing repository. func AddKey(ctx context.Context, s *Repository, password string, template *crypto.Key) (*Key, error) { // make sure we have valid KDF parameters if Params == nil { p, err := crypto.Calibrate(KDFTimeout, KDFMemory) if err != nil { return nil, errors.Wrap(err, "Calibrate") } Params = &p debug.Log("calibrated KDF parameters are %v", p) } // fill meta data about key newkey := &Key{ Created: time.Now(), KDF: "scrypt", N: Params.N, R: Params.R, P: Params.P, } 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, err = crypto.NewSalt() if err != nil { panic("unable to read enough random bytes for salt: " + err.Error()) } // call KDF to derive user key newkey.user, err = crypto.KDF(*Params, newkey.Salt, password) if err != nil { return nil, err } if template == nil { // generate new random master keys newkey.master = crypto.NewRandomKey() } else { // copy master keys from old key newkey.master = template } // encrypt master keys (as json) with user key buf, err := json.Marshal(newkey.master) if err != nil { return nil, errors.Wrap(err, "Marshal") } nonce := crypto.NewRandomNonce() ciphertext := make([]byte, 0, len(buf)+newkey.user.Overhead()+newkey.user.NonceSize()) ciphertext = append(ciphertext, nonce...) ciphertext = newkey.user.Seal(ciphertext, nonce, buf, nil) newkey.Data = ciphertext // dump as json buf, err = json.Marshal(newkey) if err != nil { return nil, errors.Wrap(err, "Marshal") } // store in repository and return h := restic.Handle{ Type: restic.KeyFile, Name: restic.Hash(buf).String(), } err = s.be.Save(ctx, h, bytes.NewReader(buf)) if err != nil { return nil, err } newkey.name = h.Name return newkey, nil } func (k *Key) String() string { if k == nil { return "" } return fmt.Sprintf("", k.Username, k.Hostname, k.Created) } // Name returns an identifier for the key. func (k Key) Name() string { return k.name } // Valid tests whether the mac and encryption keys are valid (i.e. not zero) func (k *Key) Valid() bool { return k.user.Valid() && k.master.Valid() }