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API cleanup for simplified update/final. Returns bytearrays when into is not used. Allows into buffers larger than needed. Misc other changes.

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LeoVasanko
2025-11-07 07:38:18 +00:00
parent 2e460b5796
commit cca78f4224
10 changed files with 1277 additions and 1254 deletions
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pyaegis/aegis128x2.py
+173 -208
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@@ -10,11 +10,10 @@ Error return codes from the C library raise ValueError.
# DO NOT EDIT OTHER ALGORITHM FILES MANUALLY!
import errno
from collections.abc import Buffer
from ._loader import ffi
from ._loader import lib as _lib
from .util import new_aligned_struct
from .util import Buffer, new_aligned_struct
# Constants exposed as functions in C; mirror them as integers at module import time
KEYBYTES = _lib.aegis128x2_keybytes()
@@ -39,7 +38,7 @@ def encrypt_detached(
maclen: int = ABYTES_MIN,
ct_into: Buffer | None = None,
mac_into: Buffer | None = None,
) -> tuple[memoryview, memoryview]:
) -> tuple[bytearray | memoryview, bytearray | memoryview]:
"""Encrypt message with associated data, returning ciphertext and MAC separately.
Args:
@@ -58,35 +57,34 @@ def encrypt_detached(
TypeError: If lengths are invalid.
RuntimeError: If encryption fails.
"""
nonce = memoryview(nonce)
key = memoryview(key)
message = memoryview(message)
ad = memoryview(ad) if ad is not None else None
ct_into = memoryview(ct_into) if ct_into is not None else None
mac_into = memoryview(mac_into) if mac_into is not None else None
if maclen not in (16, 32):
raise TypeError("maclen must be 16 or 32")
if key.nbytes != KEYBYTES:
if len(key) != KEYBYTES:
raise TypeError(f"key length must be {KEYBYTES}")
if nonce.nbytes != NPUBBYTES:
if len(nonce) != NPUBBYTES:
raise TypeError(f"nonce length must be {NPUBBYTES}")
c = ct_into if ct_into is not None else memoryview(bytearray(message.nbytes))
mac = mac_into if mac_into is not None else memoryview(bytearray(maclen))
if c.nbytes != message.nbytes:
raise TypeError("into length must equal len(message)")
if mac.nbytes != maclen:
raise TypeError("mac_into length must equal maclen")
if ct_into is None:
c = bytearray(len(message))
else:
if len(ct_into) < len(message):
raise TypeError("ct_into length must be at least len(message)")
c = ct_into
if mac_into is None:
mac = bytearray(maclen)
else:
if len(mac_into) < maclen:
raise TypeError("mac_into length must be at least maclen")
mac = mac_into
rc = _lib.aegis128x2_encrypt_detached(
ffi.from_buffer(c),
ffi.from_buffer(mac),
maclen,
_ptr(message),
message.nbytes,
len(message),
_ptr(ad),
0 if ad is None else ad.nbytes,
0 if ad is None else len(ad),
_ptr(nonce),
_ptr(key),
)
@@ -94,7 +92,10 @@ def encrypt_detached(
err_num = ffi.errno
err_name = errno.errorcode.get(err_num, f"errno_{err_num}")
raise RuntimeError(f"encrypt detached failed: {err_name}")
return c, mac
return (
c if ct_into is None else memoryview(c)[: len(message)],
mac if mac_into is None else memoryview(mac)[:maclen],
)
def decrypt_detached(
@@ -105,7 +106,7 @@ def decrypt_detached(
ad: Buffer | None = None,
*,
into: Buffer | None = None,
) -> memoryview:
) -> bytearray | memoryview:
"""Decrypt ciphertext with detached MAC and associated data.
Args:
@@ -117,44 +118,40 @@ def decrypt_detached(
into: Buffer to write plaintext into (default: bytearray created).
Returns:
Plaintext as bytearray if into not provided.
Plaintext as bytearray if into not provided, memoryview of into otherwise.
Raises:
TypeError: If lengths are invalid.
ValueError: If authentication fails.
"""
nonce = memoryview(nonce)
key = memoryview(key)
ct = memoryview(ct)
mac = memoryview(mac)
ad = memoryview(ad) if ad is not None else None
into = memoryview(into) if into is not None else None
if key.nbytes != KEYBYTES:
if len(key) != KEYBYTES:
raise TypeError(f"key length must be {KEYBYTES}")
if nonce.nbytes != NPUBBYTES:
if len(nonce) != NPUBBYTES:
raise TypeError(f"nonce length must be {NPUBBYTES}")
maclen = mac.nbytes
maclen = len(mac)
if maclen not in (16, 32):
raise TypeError("mac length must be 16 or 32")
m_out = into if into is not None else memoryview(bytearray(ct.nbytes))
if m_out.nbytes != ct.nbytes:
raise TypeError("into length must equal len(ciphertext)")
if into is None:
out = bytearray(len(ct))
else:
if len(into) < len(ct):
raise TypeError("into length must be at least len(ciphertext)")
out = into
rc = _lib.aegis128x2_decrypt_detached(
ffi.from_buffer(m_out),
ffi.from_buffer(out),
_ptr(ct),
ct.nbytes,
len(ct),
_ptr(mac),
maclen,
_ptr(ad),
0 if ad is None else ad.nbytes,
0 if ad is None else len(ad),
_ptr(nonce),
_ptr(key),
)
if rc != 0:
raise ValueError("authentication failed")
return memoryview(m_out)
return out if into is None else memoryview(out)[: len(ct)] # type: ignore
def encrypt(
@@ -165,7 +162,7 @@ def encrypt(
*,
maclen: int = ABYTES_MIN,
into: Buffer | None = None,
) -> memoryview:
) -> bytearray | memoryview:
"""Encrypt message with associated data, returning ciphertext with appended MAC.
Args:
@@ -177,35 +174,32 @@ def encrypt(
into: Buffer to write ciphertext+MAC into (default: bytearray created).
Returns:
Ciphertext with appended MAC as bytearray if into not provided.
Ciphertext with appended MAC as bytearray if into not provided, memoryview of into otherwise.
Raises:
TypeError: If lengths are invalid.
RuntimeError: If encryption fails.
"""
nonce = memoryview(nonce)
key = memoryview(key)
message = memoryview(message)
ad = memoryview(ad) if ad is not None else None
into = memoryview(into) if into is not None else None
if maclen not in (16, 32):
raise TypeError("maclen must be 16 or 32")
if key.nbytes != KEYBYTES:
if len(key) != KEYBYTES:
raise TypeError(f"key length must be {KEYBYTES}")
if nonce.nbytes != NPUBBYTES:
if len(nonce) != NPUBBYTES:
raise TypeError(f"nonce length must be {NPUBBYTES}")
out = into if into is not None else memoryview(bytearray(message.nbytes + maclen))
if out.nbytes != message.nbytes + maclen:
raise TypeError("into length must be len(message)+maclen")
if into is None:
out = bytearray(len(message) + maclen)
else:
if len(into) < len(message) + maclen:
raise TypeError("into length must be at least len(message)+maclen")
out = into
rc = _lib.aegis128x2_encrypt(
ffi.from_buffer(out),
maclen,
_ptr(message),
message.nbytes,
len(message),
_ptr(ad),
0 if ad is None else ad.nbytes,
0 if ad is None else len(ad),
_ptr(nonce),
_ptr(key),
)
@@ -213,7 +207,7 @@ def encrypt(
err_num = ffi.errno
err_name = errno.errorcode.get(err_num, f"errno_{err_num}")
raise RuntimeError(f"encrypt failed: {err_name}")
return out
return out if into is None else memoryview(out)[: len(message) + maclen] # type: ignore
def decrypt(
@@ -224,7 +218,7 @@ def decrypt(
*,
maclen: int = ABYTES_MIN,
into: Buffer | None = None,
) -> memoryview:
) -> bytearray | memoryview:
"""Decrypt ciphertext with appended MAC and associated data.
Args:
@@ -236,43 +230,43 @@ def decrypt(
into: Buffer to write plaintext into (default: bytearray created).
Returns:
Plaintext as bytearray if into not provided.
Plaintext as bytearray if into not provided, memoryview of into otherwise.
Raises:
TypeError: If lengths are invalid.
ValueError: If authentication fails.
"""
nonce = memoryview(nonce)
key = memoryview(key)
ct = memoryview(ct)
ad = memoryview(ad) if ad is not None else None
into = memoryview(into) if into is not None else None
if maclen not in (16, 32):
raise TypeError("maclen must be 16 or 32")
if key.nbytes != KEYBYTES:
if len(key) != KEYBYTES:
raise TypeError(f"key length must be {KEYBYTES}")
if nonce.nbytes != NPUBBYTES:
if len(nonce) != NPUBBYTES:
raise TypeError(f"nonce length must be {NPUBBYTES}")
if ct.nbytes < maclen:
if len(ct) < maclen:
raise TypeError("ciphertext too short for tag")
m_out = into if into is not None else memoryview(bytearray(ct.nbytes - maclen))
if m_out.nbytes != ct.nbytes - maclen:
raise TypeError("into length must be len(ciphertext_with_tag)-maclen")
expected_out = len(ct) - maclen
if into is None:
out = bytearray(expected_out)
else:
if len(into) < expected_out:
raise TypeError(
"into length must be at least len(ciphertext_with_tag)-maclen"
)
out = into
rc = _lib.aegis128x2_decrypt(
ffi.from_buffer(m_out),
ffi.from_buffer(out),
_ptr(ct),
ct.nbytes,
len(ct),
maclen,
_ptr(ad),
0 if ad is None else ad.nbytes,
0 if ad is None else len(ad),
_ptr(nonce),
_ptr(key),
)
if rc != 0:
raise ValueError("authentication failed")
return m_out
return out if into is None else memoryview(out)[:expected_out] # type: ignore
def stream(
@@ -281,7 +275,7 @@ def stream(
length: int | None = None,
*,
into: Buffer | None = None,
) -> memoryview:
) -> bytearray | Buffer:
"""Generate a stream of pseudorandom bytes.
Args:
@@ -291,29 +285,30 @@ def stream(
into: Buffer to write stream into (default: bytearray created).
Returns:
Pseudorandom bytes as bytearray if into not provided.
Pseudorandom bytes as bytearray, or into returned directly.
Raises:
TypeError: If lengths are invalid or neither length nor into provided.
"""
nonce = memoryview(nonce) if nonce is not None else None
key = memoryview(key)
into = memoryview(into) if into is not None else None
if key.nbytes != KEYBYTES:
if len(key) != KEYBYTES:
raise TypeError(f"key length must be {KEYBYTES}")
if nonce is not None and nonce.nbytes != NPUBBYTES:
if nonce is not None and len(nonce) != NPUBBYTES:
raise TypeError(f"nonce length must be {NPUBBYTES}")
if into is None and length is None:
raise TypeError("provide either into or length")
out = into if into is not None else memoryview(bytearray(int(length or 0)))
if into is None:
if length is None:
raise TypeError("provide either into or length")
out = bytearray(length)
else:
if length is not None and len(into) < length:
raise TypeError("into length must be at least length")
out = into
_lib.aegis128x2_stream(
ffi.from_buffer(out),
out.nbytes,
len(out),
_ptr(nonce),
_ptr(key),
)
return out
return out if into is None else memoryview(out)[: length or len(out)] # type: ignore
def encrypt_unauthenticated(
@@ -322,7 +317,7 @@ def encrypt_unauthenticated(
message: Buffer,
*,
into: Buffer | None = None,
) -> memoryview:
) -> bytearray | memoryview:
"""Encrypt message without authentication (for testing/debugging).
Args:
@@ -332,31 +327,29 @@ def encrypt_unauthenticated(
into: Buffer to write ciphertext into (default: bytearray created).
Returns:
Ciphertext as bytearray if into not provided.
Ciphertext as bytearray if into not provided, memoryview of into otherwise.
Raises:
TypeError: If lengths are invalid.
"""
message = memoryview(message)
nonce = memoryview(nonce)
key = memoryview(key)
into = memoryview(into) if into is not None else None
if key.nbytes != KEYBYTES:
if len(key) != KEYBYTES:
raise TypeError(f"key length must be {KEYBYTES}")
if nonce.nbytes != NPUBBYTES:
if len(nonce) != NPUBBYTES:
raise TypeError(f"nonce length must be {NPUBBYTES}")
out = into if into is not None else memoryview(bytearray(message.nbytes))
if out.nbytes != message.nbytes:
raise TypeError("into length must equal len(message)")
if into is None:
out = bytearray(len(message))
else:
if len(into) < len(message):
raise TypeError("into length must be at least len(message)")
out = into
_lib.aegis128x2_encrypt_unauthenticated(
ffi.from_buffer(out),
_ptr(message),
message.nbytes,
len(message),
_ptr(nonce),
_ptr(key),
)
return out
return out if into is None else memoryview(out)[: len(message)] # type: ignore
def decrypt_unauthenticated(
@@ -365,7 +358,7 @@ def decrypt_unauthenticated(
ct: Buffer,
*,
into: Buffer | None = None,
) -> memoryview:
) -> bytearray | memoryview:
"""Decrypt ciphertext without authentication (for testing/debugging).
Args:
@@ -375,31 +368,29 @@ def decrypt_unauthenticated(
into: Buffer to write plaintext into (default: bytearray created).
Returns:
Plaintext as bytearray if into not provided.
Plaintext as bytearray if into not provided, memoryview of into otherwise.
Raises:
TypeError: If lengths are invalid.
"""
ct = memoryview(ct)
nonce = memoryview(nonce)
key = memoryview(key)
into = memoryview(into) if into is not None else None
if key.nbytes != KEYBYTES:
if len(key) != KEYBYTES:
raise TypeError(f"key length must be {KEYBYTES}")
if nonce.nbytes != NPUBBYTES:
if len(nonce) != NPUBBYTES:
raise TypeError(f"nonce length must be {NPUBBYTES}")
out = into if into is not None else memoryview(bytearray(ct.nbytes))
if out.nbytes != ct.nbytes:
raise TypeError("into length must equal len(ciphertext)")
if into is None:
out = bytearray(len(ct))
else:
if len(into) < len(ct):
raise TypeError("into length must be at least len(ciphertext)")
out = into
_lib.aegis128x2_decrypt_unauthenticated(
ffi.from_buffer(out),
_ptr(ct),
ct.nbytes,
len(ct),
_ptr(nonce),
_ptr(key),
)
return out
return out if into is None else memoryview(out)[: len(ct)] # type: ignore
# This is missing from C API but convenient to have here
@@ -408,7 +399,8 @@ def mac(
nonce: Buffer,
data: Buffer,
maclen: int = ABYTES_MIN,
) -> memoryview:
into: Buffer | None = None,
) -> bytearray | memoryview:
"""Compute a MAC for the given data in one shot.
Args:
@@ -416,13 +408,14 @@ def mac(
nonce: Nonce (32 bytes)
data: Data to MAC
maclen: MAC length (16 or 32, default 16)
into: Buffer to write MAC into (default: bytearray created)
Returns:
MAC bytes
MAC bytes as bytearray if into not provided, memoryview of into otherwise
"""
mac_state = Mac(key, nonce)
mac_state.update(data)
return mac_state.final(maclen)
return mac_state.final(maclen, into)
class Mac:
@@ -460,11 +453,9 @@ class Mac:
_lib.aegis128x2_mac_state_clone(self._st, _other._st)
return
# Normal init path
nonce = memoryview(nonce)
key = memoryview(key)
if key.nbytes != KEYBYTES:
if len(key) != KEYBYTES:
raise TypeError(f"key length must be {KEYBYTES}")
if nonce.nbytes != NPUBBYTES:
if len(nonce) != NPUBBYTES:
raise TypeError(f"nonce length must be {NPUBBYTES}")
_lib.aegis128x2_mac_init(self._st, _ptr(key), _ptr(nonce))
@@ -487,8 +478,7 @@ class Mac:
Raises:
RuntimeError: If the underlying C function reports an error.
"""
data = memoryview(data)
rc = _lib.aegis128x2_mac_update(self._st, _ptr(data), data.nbytes)
rc = _lib.aegis128x2_mac_update(self._st, _ptr(data), len(data))
if rc != 0:
err_num = ffi.errno
err_name = errno.errorcode.get(err_num, f"errno_{err_num}")
@@ -498,7 +488,7 @@ class Mac:
self,
maclen: int = ABYTES_MIN,
into: Buffer | None = None,
) -> memoryview:
) -> bytearray | memoryview:
"""Finalize and return the MAC tag.
Args:
@@ -506,7 +496,7 @@ class Mac:
into: Optional buffer to write the tag into (default: bytearray created).
Returns:
The tag as a memoryview; if ``into`` is provided, it views that buffer.
The tag as bytearray if into not provided, memoryview of into otherwise.
Raises:
TypeError: If lengths are invalid.
@@ -514,16 +504,19 @@ class Mac:
"""
if maclen not in (16, 32):
raise TypeError("maclen must be 16 or 32")
out = into if into is not None else bytearray(maclen)
out = memoryview(out)
if out.nbytes != maclen:
raise TypeError("into length must equal maclen")
rc = _lib.aegis128x2_mac_final(self._st, ffi.from_buffer(out), maclen)
if into is None:
out = bytearray(maclen)
else:
if len(into) < maclen:
raise TypeError("into length must be at least maclen")
out = into
out_mv = memoryview(out)
rc = _lib.aegis128x2_mac_final(self._st, ffi.from_buffer(out_mv), maclen)
if rc != 0:
err_num = ffi.errno
err_name = errno.errorcode.get(err_num, f"errno_{err_num}")
raise RuntimeError(f"mac final failed: {err_name}")
return out
return out if into is None else memoryview(out)[:maclen] # type: ignore
def verify(self, mac: Buffer) -> bool:
"""Verify a tag for the current MAC state.
@@ -538,8 +531,7 @@ class Mac:
TypeError: If tag length is invalid.
ValueError: If verification fails.
"""
mac = memoryview(mac)
maclen = mac.nbytes
maclen = len(mac)
if maclen not in (16, 32):
raise TypeError("mac length must be 16 or 32")
rc = _lib.aegis128x2_mac_verify(self._st, _ptr(mac), maclen)
@@ -569,23 +561,20 @@ class Encryptor:
Raises:
TypeError: If key or nonce lengths are invalid.
"""
key = memoryview(key)
nonce = memoryview(nonce)
if key.nbytes != KEYBYTES:
if len(key) != KEYBYTES:
raise TypeError(f"key length must be {KEYBYTES}")
if nonce.nbytes != NPUBBYTES:
if len(nonce) != NPUBBYTES:
raise TypeError(f"nonce length must be {NPUBBYTES}")
st, owner = new_aligned_struct("aegis128x2_state", ALIGNMENT)
_lib.aegis128x2_state_init(
st,
_ptr(ad) if ad is not None else ffi.NULL,
0 if ad is None else memoryview(ad).nbytes,
0 if ad is None else len(ad),
_ptr(nonce),
_ptr(key),
)
self._st = st
self._owner = owner
# Track total plaintext bytes passed through update() so far
self._bytes_in = 0
self._bytes_out = 0
@@ -602,7 +591,9 @@ class Encryptor:
"""
return self._bytes_out
def update(self, message: Buffer, into: Buffer | None = None) -> memoryview:
def update(
self, message: Buffer, into: Buffer | None = None
) -> bytearray | memoryview:
"""Encrypt a chunk of the message.
Args:
@@ -610,28 +601,27 @@ class Encryptor:
into: Optional destination buffer; must be >= len(message).
Returns:
The ciphertext for this chunk as a memoryview; when ``into`` is
provided, a view of that buffer up to the number of bytes written.
The ciphertext for this chunk as bytearray if into not provided, memoryview of into otherwise.
Raises:
TypeError: If destination buffer is too small.
RuntimeError: If the C update call fails.
"""
message = memoryview(message)
expected_out = message.nbytes
out = memoryview(into if into is not None else bytearray(expected_out))
if out.nbytes < expected_out:
expected_out = len(message)
out = into if into is not None else bytearray(expected_out)
out_mv = memoryview(out)
if len(out_mv) < expected_out:
raise TypeError(
"into length must be >= expected output size for this update"
)
written = ffi.new("size_t *")
rc = _lib.aegis128x2_state_encrypt_update(
self._st,
ffi.from_buffer(out),
out.nbytes,
ffi.from_buffer(out_mv),
len(out_mv),
written,
_ptr(message),
message.nbytes,
len(message),
)
if rc != 0:
err_num = ffi.errno
@@ -641,11 +631,13 @@ class Encryptor:
)
w = int(written[0])
assert w == expected_out
self._bytes_in += message.nbytes
self._bytes_in += len(message)
self._bytes_out += w
return out[:w]
return out if into is None else memoryview(out)[:w] # type: ignore
def final(self, into: Buffer | None = None, maclen: int = ABYTES_MIN) -> memoryview:
def final(
self, into: Buffer | None = None, maclen: int = ABYTES_MIN
) -> bytearray | memoryview:
"""Finalize encryption, writing any remaining bytes and the tag.
Args:
@@ -653,9 +645,7 @@ class Encryptor:
maclen: Tag length (16 or 32). Defaults to 16.
Returns:
A memoryview of the produced bytes (tail + tag). When ``into`` is
provided, the returned view references that buffer up to the number
of bytes written.
A memoryview of the produced bytes (tail + tag) if into provided, bytearray slice otherwise.
Raises:
TypeError: If maclen is invalid.
@@ -663,14 +653,13 @@ class Encryptor:
"""
if maclen not in (16, 32):
raise TypeError("maclen must be 16 or 32")
# Worst-case final length is leftover tail (<= TAILBYTES_MAX) plus tag
out = into if into is not None else bytearray(TAILBYTES_MAX + maclen)
out = memoryview(out)
# Only the authentication tag is produced here; allocate exactly maclen
out = into if into is not None else bytearray(maclen)
written = ffi.new("size_t *")
rc = _lib.aegis128x2_state_encrypt_final(
self._st,
ffi.from_buffer(out),
out.nbytes,
len(out),
written,
maclen,
)
@@ -679,15 +668,18 @@ class Encryptor:
err_name = errno.errorcode.get(err_num, f"errno_{err_num}")
raise RuntimeError(f"state encrypt final failed: {err_name}")
w = int(written[0])
if into is None:
# Only the tag bytes are returned when we allocate the buffer
assert w == maclen
self._bytes_out += w
return out[:w]
return out if into is None else memoryview(out)[:w] # type: ignore
class Decryptor:
"""Incremental decryptor.
- update(ciphertext[, into]) -> returns plaintext bytes
- final(mac[, into]) -> returns any remaining plaintext bytes
- final(mac) -> verifies the MAC tag
"""
__slots__ = ("_st", "_owner", "_bytes_in", "_bytes_out")
@@ -703,23 +695,20 @@ class Decryptor:
Raises:
TypeError: If key or nonce lengths are invalid.
"""
key = memoryview(key)
nonce = memoryview(nonce)
if key.nbytes != KEYBYTES:
if len(key) != KEYBYTES:
raise TypeError(f"key length must be {KEYBYTES}")
if nonce.nbytes != NPUBBYTES:
if len(nonce) != NPUBBYTES:
raise TypeError(f"nonce length must be {NPUBBYTES}")
st, owner = new_aligned_struct("aegis128x2_state", ALIGNMENT)
_lib.aegis128x2_state_init(
st,
_ptr(ad) if ad is not None else ffi.NULL,
0 if ad is None else memoryview(ad).nbytes,
0 if ad is None else len(ad),
_ptr(nonce),
_ptr(key),
)
self._st = st
self._owner = owner
# Track total ciphertext bytes passed through update() so far
self._bytes_in = 0
self._bytes_out = 0
@@ -730,13 +719,10 @@ class Decryptor:
@property
def bytes_out(self) -> int:
"""Total plaintext bytes produced so far.
Includes bytes written by update() and by final().
"""
"""Total plaintext bytes produced so far."""
return self._bytes_out
def update(self, ct: Buffer, into: Buffer | None = None) -> memoryview:
def update(self, ct: Buffer, into: Buffer | None = None) -> bytearray | memoryview:
"""Process a chunk of ciphertext.
Args:
@@ -744,75 +730,54 @@ class Decryptor:
into: Optional destination buffer; must be >= len(ciphertext).
Returns:
A memoryview of the decrypted bytes for this chunk. When ``into`` is
provided, the returned view references that buffer up to the number
of bytes written.
A memoryview of the decrypted bytes for this chunk if into provided, bytearray otherwise.
Raises:
TypeError: If destination buffer is too small.
RuntimeError: If the C update call fails.
"""
ct = memoryview(ct)
expected_out = ct.nbytes
expected_out = len(ct)
out = into if into is not None else bytearray(expected_out)
out = memoryview(out)
if out.nbytes < expected_out:
out_mv = memoryview(out)
if len(out_mv) < expected_out:
raise TypeError("into length must be >= required capacity for this update")
written = ffi.new("size_t *")
rc = _lib.aegis128x2_state_decrypt_detached_update(
self._st,
ffi.from_buffer(out),
out.nbytes,
ffi.from_buffer(out_mv),
len(out_mv),
written,
_ptr(ct),
ct.nbytes,
len(ct),
)
if rc != 0:
err_num = ffi.errno
err_name = errno.errorcode.get(err_num, f"errno_{err_num}")
raise RuntimeError(f"state decrypt update failed: {err_name}")
w = int(written[0])
assert w == expected_out
self._bytes_in += ct.nbytes
assert w == expected_out, f"got {w}, expected {expected_out}, len(ct)={len(ct)}"
self._bytes_in += len(ct)
self._bytes_out += w
return out[:w]
return out if into is None else memoryview(out)[:w] # type: ignore
def final(self, mac: Buffer, into: Buffer | None = None) -> memoryview:
"""Finalize decryption by verifying tag and flushing remaining bytes.
def final(self, mac: Buffer) -> None:
"""Finalize decryption by verifying the MAC tag.
Args:
mac: Tag to verify (16 or 32 bytes).
into: Optional destination buffer for the remaining plaintext bytes.
Returns:
A memoryview of the remaining plaintext bytes. When ``into`` is
provided, the returned view references that buffer up to the number
of bytes written.
Raises:
TypeError: If tag length is invalid.
ValueError: If authentication fails.
"""
mac = memoryview(mac)
maclen = mac.nbytes
maclen = len(mac)
if maclen not in (16, 32):
raise TypeError("mac length must be 16 or 32")
out = into if into is not None else bytearray(TAILBYTES_MAX)
out = memoryview(out)
written = ffi.new("size_t *")
rc = _lib.aegis128x2_state_decrypt_detached_final(
self._st,
ffi.from_buffer(out),
out.nbytes,
written,
_ptr(mac),
maclen,
self._st, ffi.NULL, 0, ffi.NULL, _ptr(mac), maclen
)
if rc != 0:
raise ValueError("authentication failed")
w = int(written[0])
self._bytes_out += w
return out[:w]
def new_state():