package repository import ( "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.New("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.New("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 id restic.ID } // 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 const ( // 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(ctx context.Context, s *Repository, password string) (*Key, error) { return AddKey(ctx, s, password, "", "", nil) } // OpenKey tries do decrypt the key specified by name with the given password. func OpenKey(ctx context.Context, s *Repository, id restic.ID, password string) (*Key, error) { k, err := LoadKey(ctx, s, id) if err != nil { debug.Log("LoadKey(%v) returned error %v", id.String(), 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.id = id 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, keyHint string) (k *Key, err error) { checked := 0 if len(keyHint) > 0 { id, err := restic.Find(ctx, s, restic.KeyFile, keyHint) if err == nil { key, err := OpenKey(ctx, s, id, password) if err == nil { debug.Log("successfully opened hinted key %v", id) return key, nil } debug.Log("could not open hinted key %v", id) } else { debug.Log("Could not find hinted key %v", keyHint) } } listCtx, cancel := context.WithCancel(ctx) defer cancel() // try at most maxKeys keys in repo err = s.List(listCtx, restic.KeyFile, func(id restic.ID, _ int64) error { checked++ if maxKeys > 0 && checked > maxKeys { return ErrMaxKeysReached } debug.Log("trying key %q", id.String()) key, err := OpenKey(ctx, s, id, password) if err != nil { debug.Log("key %v returned error %v", id.String(), err) // ErrUnauthenticated means the password is wrong, try the next key if errors.Is(err, crypto.ErrUnauthenticated) { return nil } return err } debug.Log("successfully opened key %v", id.String()) k = key cancel() return nil }) if err == context.Canceled { err = nil } if err != nil { return nil, err } if k == nil { return nil, ErrNoKeyFound } return k, nil } // LoadKey loads a key from the backend. func LoadKey(ctx context.Context, s *Repository, id restic.ID) (k *Key, err error) { data, err := s.LoadRaw(ctx, restic.KeyFile, id) 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, username, hostname 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(), Username: username, Hostname: hostname, KDF: "scrypt", N: params.N, R: params.R, P: params.P, } if newkey.Hostname == "" { newkey.Hostname, _ = os.Hostname() } if newkey.Username == "" { usr, err := user.Current() if err == nil { newkey.Username = usr.Username } } // generate random salt var err error 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, crypto.CiphertextLength(len(buf))) 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") } id := restic.Hash(buf) // store in repository and return h := backend.Handle{ Type: restic.KeyFile, Name: id.String(), } err = s.be.Save(ctx, h, backend.NewByteReader(buf, s.be.Hasher())) if err != nil { return nil, err } newkey.id = id return newkey, nil } func RemoveKey(ctx context.Context, repo *Repository, id restic.ID) error { if id == repo.KeyID() { return errors.New("refusing to remove key currently used to access repository") } h := backend.Handle{Type: restic.KeyFile, Name: id.String()} return repo.be.Remove(ctx, h) } func (k *Key) String() string { if k == nil { return "<Key nil>" } return fmt.Sprintf("<Key of %s@%s, created on %s>", k.Username, k.Hostname, k.Created) } // ID returns an identifier for the key. func (k Key) ID() restic.ID { return k.id } // 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() }