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borg/src/borg/crypto/key.py

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import binascii
import hmac
import os
import textwrap
from binascii import a2b_base64, b2a_base64, hexlify
from hashlib import sha256, pbkdf2_hmac
from typing import Literal, Callable, ClassVar
from ..logger import create_logger
logger = create_logger()
import argon2.low_level
from ..constants import * # NOQA
from ..helpers import StableDict
from ..helpers import Error, IntegrityError
from ..helpers import get_keys_dir, get_security_dir
from ..helpers import get_limited_unpacker
from ..helpers import bin_to_hex
from ..helpers.passphrase import Passphrase, PasswordRetriesExceeded, PassphraseWrong
from ..helpers import msgpack
from ..helpers import workarounds
from ..item import Key, EncryptedKey, want_bytes
from ..manifest import Manifest
from ..platform import SaveFile
from ..repoobj import RepoObj
from .low_level import AES, bytes_to_int, num_cipher_blocks, hmac_sha256, blake2b_256, hkdf_hmac_sha512
from .low_level import AES256_CTR_HMAC_SHA256, AES256_CTR_BLAKE2b, AES256_OCB, CHACHA20_POLY1305
from . import low_level
# workaround for lost passphrase or key in "authenticated" or "authenticated-blake2" mode
AUTHENTICATED_NO_KEY = "authenticated_no_key" in workarounds
class UnsupportedPayloadError(Error):
"""Unsupported payload type {}. A newer version is required to access this repository."""
class UnsupportedManifestError(Error):
"""Unsupported manifest envelope. A newer version is required to access this repository."""
class KeyfileNotFoundError(Error):
"""No key file for repository {} found in {}."""
class KeyfileInvalidError(Error):
"""Invalid key file for repository {} found in {}."""
class KeyfileMismatchError(Error):
"""Mismatch between repository {} and key file {}."""
class RepoKeyNotFoundError(Error):
"""No key entry found in the config of repository {}."""
class UnsupportedKeyFormatError(Error):
"""Your borg key is stored in an unsupported format. Try using a newer version of borg."""
class TAMRequiredError(IntegrityError):
__doc__ = textwrap.dedent(
"""
Manifest is unauthenticated, but it is required for this repository. Is somebody attacking you?
"""
).strip()
traceback = False
class ArchiveTAMRequiredError(TAMRequiredError):
__doc__ = textwrap.dedent(
"""
Archive '{}' is unauthenticated, but it is required for this repository.
"""
).strip()
traceback = False
class TAMInvalid(IntegrityError):
__doc__ = IntegrityError.__doc__
traceback = False
def __init__(self):
# Error message becomes: "Data integrity error: Manifest authentication did not verify"
super().__init__("Manifest authentication did not verify")
class ArchiveTAMInvalid(IntegrityError):
__doc__ = IntegrityError.__doc__
traceback = False
def __init__(self):
# Error message becomes: "Data integrity error: Archive authentication did not verify"
super().__init__("Archive authentication did not verify")
class TAMUnsupportedSuiteError(IntegrityError):
"""Could not verify manifest: Unsupported suite {!r}; a newer version is needed."""
traceback = False
def key_creator(repository, args, *, other_key=None):
for key in AVAILABLE_KEY_TYPES:
if key.ARG_NAME == args.encryption:
assert key.ARG_NAME is not None
return key.create(repository, args, other_key=other_key)
else:
raise ValueError('Invalid encryption mode "%s"' % args.encryption)
def key_argument_names():
return [key.ARG_NAME for key in AVAILABLE_KEY_TYPES if key.ARG_NAME]
def identify_key(manifest_data):
key_type = manifest_data[0]
if key_type == KeyType.PASSPHRASE: # legacy, see comment in KeyType class.
return RepoKey
for key in LEGACY_KEY_TYPES + AVAILABLE_KEY_TYPES:
if key.TYPE == key_type:
return key
else:
raise UnsupportedPayloadError(key_type)
def key_factory(repository, manifest_chunk, *, ro_cls=RepoObj):
manifest_data = ro_cls.extract_crypted_data(manifest_chunk)
assert manifest_data, "manifest data must not be zero bytes long"
return identify_key(manifest_data).detect(repository, manifest_data)
def uses_same_chunker_secret(other_key, key):
"""is the chunker secret the same?"""
# avoid breaking the deduplication by a different chunker secret
same_chunker_secret = other_key.chunk_seed == key.chunk_seed
return same_chunker_secret
def uses_same_id_hash(other_key, key):
"""other_key -> key upgrade: is the id hash the same?"""
# avoid breaking the deduplication by changing the id hash
old_sha256_ids = (PlaintextKey,)
new_sha256_ids = (PlaintextKey,)
old_hmac_sha256_ids = (RepoKey, KeyfileKey, AuthenticatedKey)
new_hmac_sha256_ids = (AESOCBRepoKey, AESOCBKeyfileKey, CHPORepoKey, CHPOKeyfileKey, AuthenticatedKey)
old_blake2_ids = (Blake2RepoKey, Blake2KeyfileKey, Blake2AuthenticatedKey)
new_blake2_ids = (
Blake2AESOCBRepoKey,
Blake2AESOCBKeyfileKey,
Blake2CHPORepoKey,
Blake2CHPOKeyfileKey,
Blake2AuthenticatedKey,
)
same_ids = (
isinstance(other_key, old_hmac_sha256_ids + new_hmac_sha256_ids)
and isinstance(key, new_hmac_sha256_ids)
or isinstance(other_key, old_blake2_ids + new_blake2_ids)
and isinstance(key, new_blake2_ids)
or isinstance(other_key, old_sha256_ids + new_sha256_ids)
and isinstance(key, new_sha256_ids)
)
return same_ids
class KeyBase:
# Numeric key type ID, must fit in one byte.
TYPE: int = None # override in subclasses
# set of key type IDs the class can handle as input
TYPES_ACCEPTABLE: set[int] = None # override in subclasses
# Human-readable name
NAME = "UNDEFINED"
# Name used in command line / API (e.g. borg init --encryption=...)
ARG_NAME = "UNDEFINED"
# Storage type (no key blob storage / keyfile / repo)
STORAGE: ClassVar[str] = KeyBlobStorage.NO_STORAGE
# Seed for the buzhash chunker (borg.algorithms.chunker.Chunker)
# type is int
chunk_seed: int = None
# Whether this *particular instance* is encrypted from a practical point of view,
# i.e. when it's using encryption with a empty passphrase, then
# that may be *technically* called encryption, but for all intents and purposes
# that's as good as not encrypting in the first place, and this member should be False.
#
# The empty passphrase is also special because Borg tries it first when no passphrase
# was supplied, and if an empty passphrase works, then Borg won't ask for one.
logically_encrypted = False
def __init__(self, repository):
self.TYPE_STR = bytes([self.TYPE])
self.repository = repository
self.target = None # key location file path / repo obj
self.copy_crypt_key = False
def id_hash(self, data):
"""Return HMAC hash using the "id" HMAC key"""
raise NotImplementedError
def encrypt(self, id, data):
pass
def decrypt(self, id, data):
pass
def assert_id(self, id, data):
if id and id != Manifest.MANIFEST_ID:
id_computed = self.id_hash(data)
if not hmac.compare_digest(id_computed, id):
raise IntegrityError("Chunk %s: id verification failed" % bin_to_hex(id))
def assert_type(self, type_byte, id=None):
if type_byte not in self.TYPES_ACCEPTABLE:
id_str = bin_to_hex(id) if id is not None else "(unknown)"
raise IntegrityError(f"Chunk {id_str}: Invalid encryption envelope")
def _tam_key(self, salt, context):
return hkdf_hmac_sha512(
ikm=self.id_key + self.crypt_key,
salt=salt,
info=b"borg-metadata-authentication-" + context,
output_length=64,
)
def pack_and_authenticate_metadata(self, metadata_dict, context=b"manifest", salt=None):
if salt is None:
salt = os.urandom(64)
metadata_dict = StableDict(metadata_dict)
tam = metadata_dict["tam"] = StableDict({"type": "HKDF_HMAC_SHA512", "hmac": bytes(64), "salt": salt})
packed = msgpack.packb(metadata_dict)
tam_key = self._tam_key(salt, context)
tam["hmac"] = hmac.digest(tam_key, packed, "sha512")
return msgpack.packb(metadata_dict)
def unpack_and_verify_manifest(self, data):
"""Unpack msgpacked *data* and return manifest."""
if data.startswith(b"\xc1" * 4):
# This is a manifest from the future, we can't read it.
raise UnsupportedManifestError()
data = bytearray(data)
unpacker = get_limited_unpacker("manifest")
unpacker.feed(data)
unpacked = unpacker.unpack()
if AUTHENTICATED_NO_KEY:
return unpacked
if "tam" not in unpacked:
raise TAMRequiredError(self.repository._location.canonical_path())
tam = unpacked.pop("tam", None)
if not isinstance(tam, dict):
raise TAMInvalid()
tam_type = tam.get("type", "<none>")
if tam_type != "HKDF_HMAC_SHA512":
raise TAMUnsupportedSuiteError(repr(tam_type))
tam_hmac = tam.get("hmac")
tam_salt = tam.get("salt")
if not isinstance(tam_salt, (bytes, str)) or not isinstance(tam_hmac, (bytes, str)):
raise TAMInvalid()
tam_hmac = want_bytes(tam_hmac) # legacy
tam_salt = want_bytes(tam_salt) # legacy
offset = data.index(tam_hmac)
data[offset : offset + 64] = bytes(64)
tam_key = self._tam_key(tam_salt, context=b"manifest")
calculated_hmac = hmac.digest(tam_key, data, "sha512")
if not hmac.compare_digest(calculated_hmac, tam_hmac):
raise TAMInvalid()
logger.debug("TAM-verified manifest")
return unpacked
def unpack_and_verify_archive(self, data, force_tam_not_required=False):
"""Unpack msgpacked *data* and return (object, did_verify)."""
tam_required = self.tam_required
if force_tam_not_required and tam_required:
# for a long time, borg only checked manifest for "tam_required" and
# people might have archives without TAM, so don't be too annoyingly loud here:
logger.debug("Archive authentication DISABLED.")
tam_required = False
data = bytearray(data)
unpacker = get_limited_unpacker("archive")
unpacker.feed(data)
unpacked = unpacker.unpack()
if "tam" not in unpacked:
if tam_required:
archive_name = unpacked.get("name", "<unknown>")
raise ArchiveTAMRequiredError(archive_name)
else:
logger.debug("Archive TAM not found and not required")
return unpacked, False, None
tam = unpacked.pop("tam", None)
if not isinstance(tam, dict):
raise ArchiveTAMInvalid()
tam_type = tam.get("type", "<none>")
if tam_type != "HKDF_HMAC_SHA512":
if tam_required:
raise TAMUnsupportedSuiteError(repr(tam_type))
else:
logger.debug(
"Ignoring archive TAM made with unsupported suite, since TAM is not required: %r", tam_type
)
return unpacked, False, None
tam_hmac = tam.get("hmac")
tam_salt = tam.get("salt")
if not isinstance(tam_salt, (bytes, str)) or not isinstance(tam_hmac, (bytes, str)):
raise ArchiveTAMInvalid()
tam_hmac = want_bytes(tam_hmac) # legacy
tam_salt = want_bytes(tam_salt) # legacy
offset = data.index(tam_hmac)
data[offset : offset + 64] = bytes(64)
tam_key = self._tam_key(tam_salt, context=b"archive")
calculated_hmac = hmac.digest(tam_key, data, "sha512")
if not hmac.compare_digest(calculated_hmac, tam_hmac):
raise ArchiveTAMInvalid()
logger.debug("TAM-verified archive")
return unpacked, True, tam_salt
class PlaintextKey(KeyBase):
TYPE = KeyType.PLAINTEXT
TYPES_ACCEPTABLE = {TYPE}
NAME = "plaintext"
ARG_NAME = "none"
chunk_seed = 0
logically_encrypted = False
@classmethod
def create(cls, repository, args, **kw):
logger.info('Encryption NOT enabled.\nUse the "--encryption=repokey|keyfile" to enable encryption.')
return cls(repository)
@classmethod
def detect(cls, repository, manifest_data):
return cls(repository)
def id_hash(self, data):
return sha256(data).digest()
def encrypt(self, id, data):
return b"".join([self.TYPE_STR, data])
def decrypt(self, id, data):
self.assert_type(data[0], id)
return memoryview(data)[1:]
def _tam_key(self, salt, context):
return salt + context
def random_blake2b_256_key():
# This might look a bit curious, but is the same construction used in the keyed mode of BLAKE2b.
# Why limit the key to 64 bytes and pad it with 64 nulls nonetheless? The answer is that BLAKE2b
# has a 128 byte block size, but only 64 bytes of internal state (this is also referred to as a
# "local wide pipe" design, because the compression function transforms (block, state) => state,
# and len(block) >= len(state), hence wide.)
# In other words, a key longer than 64 bytes would have simply no advantage, since the function
# has no way of propagating more than 64 bytes of entropy internally.
# It's padded to a full block so that the key is never buffered internally by blake2b_update, ie.
# it remains in a single memory location that can be tracked and could be erased securely, if we
# wanted to.
return os.urandom(64) + bytes(64)
class ID_BLAKE2b_256:
"""
Key mix-in class for using BLAKE2b-256 for the id key.
The id_key length must be 32 bytes.
"""
def id_hash(self, data):
return blake2b_256(self.id_key, data)
def init_from_random_data(self):
super().init_from_random_data()
enc_key = os.urandom(32)
enc_hmac_key = random_blake2b_256_key()
self.crypt_key = enc_key + enc_hmac_key
self.id_key = random_blake2b_256_key()
class ID_HMAC_SHA_256:
"""
Key mix-in class for using HMAC-SHA-256 for the id key.
The id_key length must be 32 bytes.
"""
def id_hash(self, data):
return hmac_sha256(self.id_key, data)
class AESKeyBase(KeyBase):
"""
Chunks are encrypted using 256bit AES in Counter Mode (CTR)
Payload layout: TYPE(1) + HMAC(32) + NONCE(8) + CIPHERTEXT
To reduce payload size only 8 bytes of the 16 bytes nonce is saved
in the payload, the first 8 bytes are always zeros. This does not
affect security but limits the maximum repository capacity to
only 295 exabytes!
"""
PAYLOAD_OVERHEAD = 1 + 32 + 8 # TYPE + HMAC + NONCE
CIPHERSUITE: Callable = None # override in derived class
logically_encrypted = True
def encrypt(self, id, data):
# legacy, this is only used by the tests.
next_iv = self.cipher.next_iv()
return self.cipher.encrypt(data, header=self.TYPE_STR, iv=next_iv)
def decrypt(self, id, data):
self.assert_type(data[0], id)
try:
return self.cipher.decrypt(data)
except IntegrityError as e:
raise IntegrityError(f"Chunk {bin_to_hex(id)}: Could not decrypt [{str(e)}]")
def init_from_given_data(self, *, crypt_key, id_key, chunk_seed):
assert len(crypt_key) in (32 + 32, 32 + 128)
assert len(id_key) in (32, 128)
assert isinstance(chunk_seed, int)
self.crypt_key = crypt_key
self.id_key = id_key
self.chunk_seed = chunk_seed
def init_from_random_data(self):
data = os.urandom(100)
chunk_seed = bytes_to_int(data[96:100])
# Convert to signed int32
if chunk_seed & 0x80000000:
chunk_seed = chunk_seed - 0xFFFFFFFF - 1
self.init_from_given_data(crypt_key=data[0:64], id_key=data[64:96], chunk_seed=chunk_seed)
def init_ciphers(self, manifest_data=None):
enc_key, enc_hmac_key = self.crypt_key[0:32], self.crypt_key[32:]
self.cipher = self.CIPHERSUITE(mac_key=enc_hmac_key, enc_key=enc_key, header_len=1, aad_offset=1)
if manifest_data is None:
nonce = 0
else:
self.assert_type(manifest_data[0])
# manifest_blocks is a safe upper bound on the amount of cipher blocks needed
# to encrypt the manifest. depending on the ciphersuite and overhead, it might
# be a bit too high, but that does not matter.
manifest_blocks = num_cipher_blocks(len(manifest_data))
nonce = self.cipher.extract_iv(manifest_data) + manifest_blocks
self.cipher.set_iv(nonce)
class FlexiKey:
FILE_ID = "BORG_KEY"
STORAGE: ClassVar[str] = KeyBlobStorage.NO_STORAGE # override in subclass
@classmethod
def detect(cls, repository, manifest_data):
key = cls(repository)
target = key.find_key()
prompt = "Enter passphrase for key %s: " % target
passphrase = Passphrase.env_passphrase()
if passphrase is None:
passphrase = Passphrase()
if not key.load(target, passphrase):
for retry in range(0, 3):
passphrase = Passphrase.getpass(prompt)
if key.load(target, passphrase):
break
else:
raise PasswordRetriesExceeded
else:
if not key.load(target, passphrase):
raise PassphraseWrong
key.init_ciphers(manifest_data)
key._passphrase = passphrase
return key
def _load(self, key_data, passphrase):
cdata = a2b_base64(key_data)
data = self.decrypt_key_file(cdata, passphrase)
if data:
data = msgpack.unpackb(data)
key = Key(internal_dict=data)
if key.version not in (1, 2): # legacy: item.Key can still process v1 keys
raise UnsupportedKeyFormatError()
self.repository_id = key.repository_id
self.crypt_key = key.crypt_key
self.id_key = key.id_key
self.chunk_seed = key.chunk_seed
return True
return False
def decrypt_key_file(self, data, passphrase):
unpacker = get_limited_unpacker("key")
unpacker.feed(data)
data = unpacker.unpack()
encrypted_key = EncryptedKey(internal_dict=data)
if encrypted_key.version != 1:
raise UnsupportedKeyFormatError()
else:
self._encrypted_key_algorithm = encrypted_key.algorithm
if encrypted_key.algorithm == "sha256":
return self.decrypt_key_file_pbkdf2(encrypted_key, passphrase)
elif encrypted_key.algorithm == "argon2 chacha20-poly1305":
return self.decrypt_key_file_argon2(encrypted_key, passphrase)
else:
raise UnsupportedKeyFormatError()
@staticmethod
def pbkdf2(passphrase, salt, iterations, output_len_in_bytes):
if os.environ.get("BORG_TESTONLY_WEAKEN_KDF") == "1":
iterations = 1
return pbkdf2_hmac("sha256", passphrase.encode("utf-8"), salt, iterations, output_len_in_bytes)
@staticmethod
def argon2(
passphrase: str,
output_len_in_bytes: int,
salt: bytes,
time_cost: int,
memory_cost: int,
parallelism: int,
type: Literal["i", "d", "id"],
) -> bytes:
if os.environ.get("BORG_TESTONLY_WEAKEN_KDF") == "1":
time_cost = 1
parallelism = 1
# 8 is the smallest value that avoids the "Memory cost is too small" exception
memory_cost = 8
type_map = {"i": argon2.low_level.Type.I, "d": argon2.low_level.Type.D, "id": argon2.low_level.Type.ID}
key = argon2.low_level.hash_secret_raw(
secret=passphrase.encode("utf-8"),
hash_len=output_len_in_bytes,
salt=salt,
time_cost=time_cost,
memory_cost=memory_cost,
parallelism=parallelism,
type=type_map[type],
)
return key
def decrypt_key_file_pbkdf2(self, encrypted_key, passphrase):
key = self.pbkdf2(passphrase, encrypted_key.salt, encrypted_key.iterations, 32)
data = AES(key, b"\0" * 16).decrypt(encrypted_key.data)
if hmac.compare_digest(hmac_sha256(key, data), encrypted_key.hash):
return data
return None
def decrypt_key_file_argon2(self, encrypted_key, passphrase):
key = self.argon2(
passphrase,
output_len_in_bytes=32,
salt=encrypted_key.salt,
time_cost=encrypted_key.argon2_time_cost,
memory_cost=encrypted_key.argon2_memory_cost,
parallelism=encrypted_key.argon2_parallelism,
type=encrypted_key.argon2_type,
)
ae_cipher = CHACHA20_POLY1305(key=key, iv=0, header_len=0, aad_offset=0)
try:
return ae_cipher.decrypt(encrypted_key.data)
except low_level.IntegrityError:
return None
def encrypt_key_file(self, data, passphrase, algorithm):
if algorithm == "sha256":
return self.encrypt_key_file_pbkdf2(data, passphrase)
elif algorithm == "argon2 chacha20-poly1305":
return self.encrypt_key_file_argon2(data, passphrase)
else:
raise ValueError(f"Unexpected algorithm: {algorithm}")
def encrypt_key_file_pbkdf2(self, data, passphrase):
salt = os.urandom(32)
iterations = PBKDF2_ITERATIONS
key = self.pbkdf2(passphrase, salt, iterations, 32)
hash = hmac_sha256(key, data)
cdata = AES(key, b"\0" * 16).encrypt(data)
enc_key = EncryptedKey(version=1, salt=salt, iterations=iterations, algorithm="sha256", hash=hash, data=cdata)
return msgpack.packb(enc_key.as_dict())
def encrypt_key_file_argon2(self, data, passphrase):
salt = os.urandom(ARGON2_SALT_BYTES)
key = self.argon2(passphrase, output_len_in_bytes=32, salt=salt, **ARGON2_ARGS)
ae_cipher = CHACHA20_POLY1305(key=key, iv=0, header_len=0, aad_offset=0)
encrypted_key = EncryptedKey(
version=1,
algorithm="argon2 chacha20-poly1305",
salt=salt,
data=ae_cipher.encrypt(data),
**{"argon2_" + k: v for k, v in ARGON2_ARGS.items()},
)
return msgpack.packb(encrypted_key.as_dict())
def _save(self, passphrase, algorithm):
key = Key(
version=2,
repository_id=self.repository_id,
crypt_key=self.crypt_key,
id_key=self.id_key,
chunk_seed=self.chunk_seed,
)
data = self.encrypt_key_file(msgpack.packb(key.as_dict()), passphrase, algorithm)
key_data = "\n".join(textwrap.wrap(b2a_base64(data).decode("ascii")))
return key_data
def change_passphrase(self, passphrase=None):
if passphrase is None:
passphrase = Passphrase.new(allow_empty=True)
self.save(self.target, passphrase, algorithm=self._encrypted_key_algorithm)
@classmethod
def create(cls, repository, args, *, other_key=None):
key = cls(repository)
key.repository_id = repository.id
if other_key is not None:
if isinstance(other_key, PlaintextKey):
raise Error("Copying key material from an unencrypted repository is not possible.")
if isinstance(key, AESKeyBase):
# user must use an AEADKeyBase subclass (AEAD modes with session keys)
raise Error("Copying key material to an AES-CTR based mode is insecure and unsupported.")
if not uses_same_id_hash(other_key, key):
raise Error("You must keep the same ID hash (HMAC-SHA256 or BLAKE2b) or deduplication will break.")
if other_key.copy_crypt_key:
# give the user the option to use the same authenticated encryption (AE) key
crypt_key = other_key.crypt_key
else:
# borg transfer re-encrypts all data anyway, thus we can default to a new, random AE key
crypt_key = os.urandom(64)
key.init_from_given_data(crypt_key=crypt_key, id_key=other_key.id_key, chunk_seed=other_key.chunk_seed)
passphrase = other_key._passphrase
else:
key.init_from_random_data()
passphrase = Passphrase.new(allow_empty=True)
key.init_ciphers()
target = key.get_new_target(args)
key.save(target, passphrase, create=True, algorithm=KEY_ALGORITHMS["argon2"])
logger.info('Key in "%s" created.' % target)
logger.info("Keep this key safe. Your data will be inaccessible without it.")
return key
def sanity_check(self, filename, id):
file_id = self.FILE_ID.encode() + b" "
repo_id = hexlify(id)
with open(filename, "rb") as fd:
# we do the magic / id check in binary mode to avoid stumbling over
# decoding errors if somebody has binary files in the keys dir for some reason.
if fd.read(len(file_id)) != file_id:
raise KeyfileInvalidError(self.repository._location.canonical_path(), filename)
if fd.read(len(repo_id)) != repo_id:
raise KeyfileMismatchError(self.repository._location.canonical_path(), filename)
# we get here if it really looks like a borg key for this repo,
# do some more checks that are close to how borg reads/parses the key.
with open(filename, "r") as fd:
lines = fd.readlines()
if len(lines) < 2:
logger.warning(f"borg key sanity check: expected 2+ lines total. [{filename}]")
raise KeyfileInvalidError(self.repository._location.canonical_path(), filename)
if len(lines[0].rstrip()) > len(file_id) + len(repo_id):
logger.warning(f"borg key sanity check: key line 1 seems too long. [{filename}]")
raise KeyfileInvalidError(self.repository._location.canonical_path(), filename)
key_b64 = "".join(lines[1:])
try:
key = a2b_base64(key_b64)
except binascii.Error:
logger.warning(f"borg key sanity check: key line 2+ does not look like base64. [{filename}]")
raise KeyfileInvalidError(self.repository._location.canonical_path(), filename)
if len(key) < 20:
# this is in no way a precise check, usually we have about 400b key data.
logger.warning(
f"borg key sanity check: binary encrypted key data from key line 2+ suspiciously short."
f" [{filename}]"
)
raise KeyfileInvalidError(self.repository._location.canonical_path(), filename)
# looks good!
return filename
def find_key(self):
if self.STORAGE == KeyBlobStorage.KEYFILE:
keyfile = self._find_key_file_from_environment()
if keyfile is not None:
return self.sanity_check(keyfile, self.repository.id)
keyfile = self._find_key_in_keys_dir()
if keyfile is not None:
return keyfile
raise KeyfileNotFoundError(self.repository._location.canonical_path(), get_keys_dir())
elif self.STORAGE == KeyBlobStorage.REPO:
loc = self.repository._location.canonical_path()
key = self.repository.load_key()
if not key:
# if we got an empty key, it means there is no key.
raise RepoKeyNotFoundError(loc) from None
return loc
else:
raise TypeError("Unsupported borg key storage type")
def get_existing_or_new_target(self, args):
keyfile = self._find_key_file_from_environment()
if keyfile is not None:
return keyfile
keyfile = self._find_key_in_keys_dir()
if keyfile is not None:
return keyfile
return self._get_new_target_in_keys_dir(args)
def _find_key_in_keys_dir(self):
id = self.repository.id
keys_dir = get_keys_dir()
for name in os.listdir(keys_dir):
filename = os.path.join(keys_dir, name)
try:
return self.sanity_check(filename, id)
except (KeyfileInvalidError, KeyfileMismatchError):
pass
def get_new_target(self, args):
if self.STORAGE == KeyBlobStorage.KEYFILE:
keyfile = self._find_key_file_from_environment()
if keyfile is not None:
return keyfile
return self._get_new_target_in_keys_dir(args)
elif self.STORAGE == KeyBlobStorage.REPO:
return self.repository
else:
raise TypeError("Unsupported borg key storage type")
def _find_key_file_from_environment(self):
keyfile = os.environ.get("BORG_KEY_FILE")
if keyfile:
return os.path.abspath(keyfile)
def _get_new_target_in_keys_dir(self, args):
filename = args.location.to_key_filename()
path = filename
i = 1
while os.path.exists(path):
i += 1
path = filename + ".%d" % i
return path
def load(self, target, passphrase):
if self.STORAGE == KeyBlobStorage.KEYFILE:
with open(target) as fd:
key_data = "".join(fd.readlines()[1:])
elif self.STORAGE == KeyBlobStorage.REPO:
# While the repository is encrypted, we consider a repokey repository with a blank
# passphrase an unencrypted repository.
self.logically_encrypted = passphrase != ""
# what we get in target is just a repo location, but we already have the repo obj:
target = self.repository
key_data = target.load_key()
if not key_data:
# if we got an empty key, it means there is no key.
loc = target._location.canonical_path()
raise RepoKeyNotFoundError(loc) from None
key_data = key_data.decode("utf-8") # remote repo: msgpack issue #99, getting bytes
else:
raise TypeError("Unsupported borg key storage type")
success = self._load(key_data, passphrase)
if success:
self.target = target
return success
def save(self, target, passphrase, algorithm, create=False):
key_data = self._save(passphrase, algorithm)
if self.STORAGE == KeyBlobStorage.KEYFILE:
if create and os.path.isfile(target):
# if a new keyfile key repository is created, ensure that an existing keyfile of another
# keyfile key repo is not accidentally overwritten by careless use of the BORG_KEY_FILE env var.
# see issue #6036
raise Error('Aborting because key in "%s" already exists.' % target)
with SaveFile(target) as fd:
fd.write(f"{self.FILE_ID} {bin_to_hex(self.repository_id)}\n")
fd.write(key_data)
fd.write("\n")
elif self.STORAGE == KeyBlobStorage.REPO:
self.logically_encrypted = passphrase != ""
key_data = key_data.encode("utf-8") # remote repo: msgpack issue #99, giving bytes
target.save_key(key_data)
else:
raise TypeError("Unsupported borg key storage type")
self.target = target
def remove(self, target):
if self.STORAGE == KeyBlobStorage.KEYFILE:
os.remove(target)
elif self.STORAGE == KeyBlobStorage.REPO:
target.save_key(b"") # save empty key (no new api at remote repo necessary)
else:
raise TypeError("Unsupported borg key storage type")
class KeyfileKey(ID_HMAC_SHA_256, AESKeyBase, FlexiKey):
TYPES_ACCEPTABLE = {KeyType.KEYFILE, KeyType.REPO, KeyType.PASSPHRASE}
TYPE = KeyType.KEYFILE
NAME = "key file"
ARG_NAME = "keyfile"
STORAGE = KeyBlobStorage.KEYFILE
CIPHERSUITE = AES256_CTR_HMAC_SHA256
class RepoKey(ID_HMAC_SHA_256, AESKeyBase, FlexiKey):
TYPES_ACCEPTABLE = {KeyType.KEYFILE, KeyType.REPO, KeyType.PASSPHRASE}
TYPE = KeyType.REPO
NAME = "repokey"
ARG_NAME = "repokey"
STORAGE = KeyBlobStorage.REPO
CIPHERSUITE = AES256_CTR_HMAC_SHA256
class Blake2KeyfileKey(ID_BLAKE2b_256, AESKeyBase, FlexiKey):
TYPES_ACCEPTABLE = {KeyType.BLAKE2KEYFILE, KeyType.BLAKE2REPO}
TYPE = KeyType.BLAKE2KEYFILE
NAME = "key file BLAKE2b"
ARG_NAME = "keyfile-blake2"
STORAGE = KeyBlobStorage.KEYFILE
CIPHERSUITE = AES256_CTR_BLAKE2b
class Blake2RepoKey(ID_BLAKE2b_256, AESKeyBase, FlexiKey):
TYPES_ACCEPTABLE = {KeyType.BLAKE2KEYFILE, KeyType.BLAKE2REPO}
TYPE = KeyType.BLAKE2REPO
NAME = "repokey BLAKE2b"
ARG_NAME = "repokey-blake2"
STORAGE = KeyBlobStorage.REPO
CIPHERSUITE = AES256_CTR_BLAKE2b
class AuthenticatedKeyBase(AESKeyBase, FlexiKey):
STORAGE = KeyBlobStorage.REPO
# It's only authenticated, not encrypted.
logically_encrypted = False
def _load(self, key_data, passphrase):
if AUTHENTICATED_NO_KEY:
# fake _load if we have no key or passphrase
NOPE = bytes(32) # 256 bit all-zero
self.repository_id = NOPE
self.enc_key = NOPE
self.enc_hmac_key = NOPE
self.id_key = NOPE
self.chunk_seed = 0
self.tam_required = False
return True
return super()._load(key_data, passphrase)
def load(self, target, passphrase):
success = super().load(target, passphrase)
self.logically_encrypted = False
return success
def save(self, target, passphrase, algorithm, create=False):
super().save(target, passphrase, algorithm, create=create)
self.logically_encrypted = False
def init_ciphers(self, manifest_data=None):
if manifest_data is not None:
self.assert_type(manifest_data[0])
def encrypt(self, id, data):
return b"".join([self.TYPE_STR, data])
def decrypt(self, id, data):
self.assert_type(data[0], id)
return memoryview(data)[1:]
class AuthenticatedKey(ID_HMAC_SHA_256, AuthenticatedKeyBase):
TYPE = KeyType.AUTHENTICATED
TYPES_ACCEPTABLE = {TYPE}
NAME = "authenticated"
ARG_NAME = "authenticated"
class Blake2AuthenticatedKey(ID_BLAKE2b_256, AuthenticatedKeyBase):
TYPE = KeyType.BLAKE2AUTHENTICATED
TYPES_ACCEPTABLE = {TYPE}
NAME = "authenticated BLAKE2b"
ARG_NAME = "authenticated-blake2"
# ------------ new crypto ------------
class AEADKeyBase(KeyBase):
"""
Chunks are encrypted and authenticated using some AEAD ciphersuite
Layout: suite:4 keytype:4 reserved:8 messageIV:48 sessionID:192 auth_tag:128 payload:... [bits]
^-------------------- AAD ----------------------------^
Offsets:0 1 2 8 32 48 [bytes]
suite: 1010b for new AEAD crypto, 0000b is old crypto
keytype: see constants.KeyType (suite+keytype)
reserved: all-zero, for future use
messageIV: a counter starting from 0 for all new encrypted messages of one session
sessionID: 192bit random, computed once per session (the session key is derived from this)
auth_tag: authentication tag output of the AEAD cipher (computed over payload and AAD)
payload: encrypted chunk data
"""
PAYLOAD_OVERHEAD = 1 + 1 + 6 + 24 + 16 # [bytes], see Layout
CIPHERSUITE: Callable = None # override in subclass
logically_encrypted = True
MAX_IV = 2**48 - 1
def assert_id(self, id, data):
# Comparing the id hash here would not be needed any more for the new AEAD crypto **IF** we
# could be sure that chunks were created by normal (not tampered, not evil) borg code:
# We put the id into AAD when storing the chunk, so it gets into the authentication tag computation.
# when decrypting, we provide the id we **want** as AAD for the auth tag verification, so
# decrypting only succeeds if we got the ciphertext we wrote **for that chunk id**.
# So, basically the **repository** can not cheat on us by giving us a different chunk.
#
# **BUT**, if chunks are created by tampered, evil borg code, the borg client code could put
# a wrong chunkid into AAD and then AEAD-encrypt-and-auth this and store it into the
# repository using this bad chunkid as key (violating the usual chunkid == id_hash(data)).
# Later, when reading such a bad chunk, AEAD-auth-and-decrypt would not notice any
# issue and decrypt successfully.
# Thus, to notice such evil borg activity, we must check for such violations here:
if id and id != Manifest.MANIFEST_ID:
id_computed = self.id_hash(data)
if not hmac.compare_digest(id_computed, id):
raise IntegrityError("Chunk %s: id verification failed" % bin_to_hex(id))
def encrypt(self, id, data):
# to encrypt new data in this session we use always self.cipher and self.sessionid
reserved = b"\0"
iv = self.cipher.next_iv()
if iv > self.MAX_IV: # see the data-structures docs about why the IV range is enough
raise IntegrityError("IV overflow, should never happen.")
iv_48bit = iv.to_bytes(6, "big")
header = self.TYPE_STR + reserved + iv_48bit + self.sessionid
return self.cipher.encrypt(data, header=header, iv=iv, aad=id)
def decrypt(self, id, data):
# to decrypt existing data, we need to get a cipher configured for the sessionid and iv from header
self.assert_type(data[0], id)
iv_48bit = data[2:8]
sessionid = data[8:32]
iv = int.from_bytes(iv_48bit, "big")
cipher = self._get_cipher(sessionid, iv)
try:
return cipher.decrypt(data, aad=id)
except IntegrityError as e:
raise IntegrityError(f"Chunk {bin_to_hex(id)}: Could not decrypt [{str(e)}]")
def init_from_given_data(self, *, crypt_key, id_key, chunk_seed):
assert len(crypt_key) in (32 + 32, 32 + 128)
assert len(id_key) in (32, 128)
assert isinstance(chunk_seed, int)
self.crypt_key = crypt_key
self.id_key = id_key
self.chunk_seed = chunk_seed
def init_from_random_data(self):
data = os.urandom(100)
chunk_seed = bytes_to_int(data[96:100])
# Convert to signed int32
if chunk_seed & 0x80000000:
chunk_seed = chunk_seed - 0xFFFFFFFF - 1
self.init_from_given_data(crypt_key=data[0:64], id_key=data[64:96], chunk_seed=chunk_seed)
def _get_session_key(self, sessionid):
assert len(sessionid) == 24 # 192bit
key = hkdf_hmac_sha512(
ikm=self.crypt_key,
salt=sessionid,
info=b"borg-session-key-" + self.CIPHERSUITE.__name__.encode(),
output_length=32,
)
return key
def _get_cipher(self, sessionid, iv):
assert isinstance(iv, int)
key = self._get_session_key(sessionid)
cipher = self.CIPHERSUITE(key=key, iv=iv, header_len=1 + 1 + 6 + 24, aad_offset=0)
return cipher
def init_ciphers(self, manifest_data=None, iv=0):
# in every new session we start with a fresh sessionid and at iv == 0, manifest_data and iv params are ignored
self.sessionid = os.urandom(24)
self.cipher = self._get_cipher(self.sessionid, iv=0)
class AESOCBKeyfileKey(ID_HMAC_SHA_256, AEADKeyBase, FlexiKey):
TYPES_ACCEPTABLE = {KeyType.AESOCBKEYFILE, KeyType.AESOCBREPO}
TYPE = KeyType.AESOCBKEYFILE
NAME = "key file AES-OCB"
ARG_NAME = "keyfile-aes-ocb"
STORAGE = KeyBlobStorage.KEYFILE
CIPHERSUITE = AES256_OCB
class AESOCBRepoKey(ID_HMAC_SHA_256, AEADKeyBase, FlexiKey):
TYPES_ACCEPTABLE = {KeyType.AESOCBKEYFILE, KeyType.AESOCBREPO}
TYPE = KeyType.AESOCBREPO
NAME = "repokey AES-OCB"
ARG_NAME = "repokey-aes-ocb"
STORAGE = KeyBlobStorage.REPO
CIPHERSUITE = AES256_OCB
class CHPOKeyfileKey(ID_HMAC_SHA_256, AEADKeyBase, FlexiKey):
TYPES_ACCEPTABLE = {KeyType.CHPOKEYFILE, KeyType.CHPOREPO}
TYPE = KeyType.CHPOKEYFILE
NAME = "key file ChaCha20-Poly1305"
ARG_NAME = "keyfile-chacha20-poly1305"
STORAGE = KeyBlobStorage.KEYFILE
CIPHERSUITE = CHACHA20_POLY1305
class CHPORepoKey(ID_HMAC_SHA_256, AEADKeyBase, FlexiKey):
TYPES_ACCEPTABLE = {KeyType.CHPOKEYFILE, KeyType.CHPOREPO}
TYPE = KeyType.CHPOREPO
NAME = "repokey ChaCha20-Poly1305"
ARG_NAME = "repokey-chacha20-poly1305"
STORAGE = KeyBlobStorage.REPO
CIPHERSUITE = CHACHA20_POLY1305
class Blake2AESOCBKeyfileKey(ID_BLAKE2b_256, AEADKeyBase, FlexiKey):
TYPES_ACCEPTABLE = {KeyType.BLAKE2AESOCBKEYFILE, KeyType.BLAKE2AESOCBREPO}
TYPE = KeyType.BLAKE2AESOCBKEYFILE
NAME = "key file BLAKE2b AES-OCB"
ARG_NAME = "keyfile-blake2-aes-ocb"
STORAGE = KeyBlobStorage.KEYFILE
CIPHERSUITE = AES256_OCB
class Blake2AESOCBRepoKey(ID_BLAKE2b_256, AEADKeyBase, FlexiKey):
TYPES_ACCEPTABLE = {KeyType.BLAKE2AESOCBKEYFILE, KeyType.BLAKE2AESOCBREPO}
TYPE = KeyType.BLAKE2AESOCBREPO
NAME = "repokey BLAKE2b AES-OCB"
ARG_NAME = "repokey-blake2-aes-ocb"
STORAGE = KeyBlobStorage.REPO
CIPHERSUITE = AES256_OCB
class Blake2CHPOKeyfileKey(ID_BLAKE2b_256, AEADKeyBase, FlexiKey):
TYPES_ACCEPTABLE = {KeyType.BLAKE2CHPOKEYFILE, KeyType.BLAKE2CHPOREPO}
TYPE = KeyType.BLAKE2CHPOKEYFILE
NAME = "key file BLAKE2b ChaCha20-Poly1305"
ARG_NAME = "keyfile-blake2-chacha20-poly1305"
STORAGE = KeyBlobStorage.KEYFILE
CIPHERSUITE = CHACHA20_POLY1305
class Blake2CHPORepoKey(ID_BLAKE2b_256, AEADKeyBase, FlexiKey):
TYPES_ACCEPTABLE = {KeyType.BLAKE2CHPOKEYFILE, KeyType.BLAKE2CHPOREPO}
TYPE = KeyType.BLAKE2CHPOREPO
NAME = "repokey BLAKE2b ChaCha20-Poly1305"
ARG_NAME = "repokey-blake2-chacha20-poly1305"
STORAGE = KeyBlobStorage.REPO
CIPHERSUITE = CHACHA20_POLY1305
LEGACY_KEY_TYPES = (
# legacy (AES-CTR based) crypto
KeyfileKey,
RepoKey,
Blake2KeyfileKey,
Blake2RepoKey,
)
AVAILABLE_KEY_TYPES = (
# these are available encryption modes for new repositories
# not encrypted modes
PlaintextKey,
AuthenticatedKey,
Blake2AuthenticatedKey,
# new crypto
AESOCBKeyfileKey,
AESOCBRepoKey,
CHPOKeyfileKey,
CHPORepoKey,
Blake2AESOCBKeyfileKey,
Blake2AESOCBRepoKey,
Blake2CHPOKeyfileKey,
Blake2CHPORepoKey,
)
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