Add messages for mismatched checks

This commit is contained in:
Dan 2022-12-25 15:08:02 +01:00
parent ae028ab4b6
commit b23e34494e
5 changed files with 59 additions and 34 deletions

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@ -982,7 +982,10 @@ class Client(Methods):
# https://core.telegram.org/cdn#verifying-files # https://core.telegram.org/cdn#verifying-files
for i, h in enumerate(hashes): for i, h in enumerate(hashes):
cdn_chunk = decrypted_chunk[h.limit * i: h.limit * (i + 1)] cdn_chunk = decrypted_chunk[h.limit * i: h.limit * (i + 1)]
CDNFileHashMismatch.check(h.hash == sha256(cdn_chunk).digest()) CDNFileHashMismatch.check(
h.hash == sha256(cdn_chunk).digest(),
"h.hash == sha256(cdn_chunk).digest()"
)
yield decrypted_chunk yield decrypted_chunk

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@ -62,7 +62,7 @@ def unpack(
auth_key_id: bytes, auth_key_id: bytes,
stored_msg_ids: List[int] stored_msg_ids: List[int]
) -> Message: ) -> Message:
SecurityCheckMismatch.check(b.read(8) == auth_key_id) SecurityCheckMismatch.check(b.read(8) == auth_key_id, "b.read(8) == auth_key_id")
msg_key = b.read(16) msg_key = b.read(16)
aes_key, aes_iv = kdf(auth_key, msg_key, False) aes_key, aes_iv = kdf(auth_key, msg_key, False)
@ -70,7 +70,7 @@ def unpack(
data.read(8) # Salt data.read(8) # Salt
# https://core.telegram.org/mtproto/security_guidelines#checking-session-id # https://core.telegram.org/mtproto/security_guidelines#checking-session-id
SecurityCheckMismatch.check(data.read(8) == session_id) SecurityCheckMismatch.check(data.read(8) == session_id, "data.read(8) == session_id")
try: try:
message = Message.read(data) message = Message.read(data)
@ -88,39 +88,40 @@ def unpack(
# https://core.telegram.org/mtproto/security_guidelines#checking-sha256-hash-value-of-msg-key # https://core.telegram.org/mtproto/security_guidelines#checking-sha256-hash-value-of-msg-key
# 96 = 88 + 8 (incoming message) # 96 = 88 + 8 (incoming message)
SecurityCheckMismatch.check(msg_key == sha256(auth_key[96:96 + 32] + data.getvalue()).digest()[8:24]) SecurityCheckMismatch.check(
msg_key == sha256(auth_key[96:96 + 32] + data.getvalue()).digest()[8:24],
"msg_key == sha256(auth_key[96:96 + 32] + data.getvalue()).digest()[8:24]"
)
# https://core.telegram.org/mtproto/security_guidelines#checking-message-length # https://core.telegram.org/mtproto/security_guidelines#checking-message-length
data.seek(32) # Get to the payload, skip salt (8) + session_id (8) + msg_id (8) + seq_no (4) + length (4) data.seek(32) # Get to the payload, skip salt (8) + session_id (8) + msg_id (8) + seq_no (4) + length (4)
payload = data.read() payload = data.read()
padding = payload[message.length:] padding = payload[message.length:]
SecurityCheckMismatch.check(12 <= len(padding) <= 1024) SecurityCheckMismatch.check(12 <= len(padding) <= 1024, "12 <= len(padding) <= 1024")
SecurityCheckMismatch.check(len(payload) % 4 == 0) SecurityCheckMismatch.check(len(payload) % 4 == 0, "len(payload) % 4 == 0")
# https://core.telegram.org/mtproto/security_guidelines#checking-msg-id # https://core.telegram.org/mtproto/security_guidelines#checking-msg-id
SecurityCheckMismatch.check(message.msg_id % 2 != 0) SecurityCheckMismatch.check(message.msg_id % 2 != 0, "message.msg_id % 2 != 0")
if len(stored_msg_ids) > STORED_MSG_IDS_MAX_SIZE: if len(stored_msg_ids) > STORED_MSG_IDS_MAX_SIZE:
del stored_msg_ids[:STORED_MSG_IDS_MAX_SIZE // 2] del stored_msg_ids[:STORED_MSG_IDS_MAX_SIZE // 2]
if stored_msg_ids: if stored_msg_ids:
# Ignored message: msg_id is lower than all of the stored values
if message.msg_id < stored_msg_ids[0]: if message.msg_id < stored_msg_ids[0]:
raise SecurityCheckMismatch raise SecurityCheckMismatch("The msg_id is lower than all the stored values")
# Ignored message: msg_id is equal to any of the stored values
if message.msg_id in stored_msg_ids: if message.msg_id in stored_msg_ids:
raise SecurityCheckMismatch raise SecurityCheckMismatch("The msg_id is equal to any of the stored values")
time_diff = (message.msg_id - MsgId()) / 2 ** 32 time_diff = (message.msg_id - MsgId()) / 2 ** 32
# Ignored message: msg_id belongs over 30 seconds in the future
if time_diff > 30: if time_diff > 30:
raise SecurityCheckMismatch raise SecurityCheckMismatch("The msg_id belongs to over 30 seconds in the future. "
"Most likely the client time has to be synchronized.")
# Ignored message: msg_id belongs over 300 seconds in the past
if time_diff < -300: if time_diff < -300:
raise SecurityCheckMismatch raise SecurityCheckMismatch("The msg_id belongs to over 300 seconds in the past. "
"Most likely the client time has to be synchronized.")
bisect.insort(stored_msg_ids, message.msg_id) bisect.insort(stored_msg_ids, message.msg_id)

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@ -45,21 +45,21 @@ class SecurityError(Exception):
"""Generic security error.""" """Generic security error."""
@classmethod @classmethod
def check(cls, cond: bool): def check(cls, cond: bool, msg: str):
"""Raises this exception if the condition is false""" """Raises this exception if the condition is false"""
if not cond: if not cond:
raise cls raise cls(f"Check failed: {msg}")
class SecurityCheckMismatch(SecurityError): class SecurityCheckMismatch(SecurityError):
"""Raised when a security check mismatch occurs.""" """Raised when a security check mismatch occurs."""
def __init__(self): def __init__(self, msg: str = None):
super().__init__("A security check mismatch has occurred.") super().__init__("A security check mismatch has occurred." if msg is None else msg)
class CDNFileHashMismatch(SecurityError): class CDNFileHashMismatch(SecurityError):
"""Raised when a CDN file hash mismatch occurs.""" """Raised when a CDN file hash mismatch occurs."""
def __init__(self): def __init__(self, msg: str = None):
super().__init__("A CDN file hash mismatch has occurred.") super().__init__("A CDN file hash mismatch has occurred." if msg is None else msg)

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@ -211,33 +211,51 @@ class Auth:
# Security checks # Security checks
####################### #######################
SecurityCheckMismatch.check(dh_prime == prime.CURRENT_DH_PRIME) SecurityCheckMismatch.check(dh_prime == prime.CURRENT_DH_PRIME, "dh_prime == prime.CURRENT_DH_PRIME")
log.debug("DH parameters check: OK") log.debug("DH parameters check: OK")
# https://core.telegram.org/mtproto/security_guidelines#g-a-and-g-b-validation # https://core.telegram.org/mtproto/security_guidelines#g-a-and-g-b-validation
g_b = int.from_bytes(g_b, "big") g_b = int.from_bytes(g_b, "big")
SecurityCheckMismatch.check(1 < g < dh_prime - 1) SecurityCheckMismatch.check(1 < g < dh_prime - 1, "1 < g < dh_prime - 1")
SecurityCheckMismatch.check(1 < g_a < dh_prime - 1) SecurityCheckMismatch.check(1 < g_a < dh_prime - 1, "1 < g_a < dh_prime - 1")
SecurityCheckMismatch.check(1 < g_b < dh_prime - 1) SecurityCheckMismatch.check(1 < g_b < dh_prime - 1, "1 < g_b < dh_prime - 1")
SecurityCheckMismatch.check(2 ** (2048 - 64) < g_a < dh_prime - 2 ** (2048 - 64)) SecurityCheckMismatch.check(
SecurityCheckMismatch.check(2 ** (2048 - 64) < g_b < dh_prime - 2 ** (2048 - 64)) 2 ** (2048 - 64) < g_a < dh_prime - 2 ** (2048 - 64),
"2 ** (2048 - 64) < g_a < dh_prime - 2 ** (2048 - 64)"
)
SecurityCheckMismatch.check(
2 ** (2048 - 64) < g_b < dh_prime - 2 ** (2048 - 64),
"2 ** (2048 - 64) < g_b < dh_prime - 2 ** (2048 - 64)"
)
log.debug("g_a and g_b validation: OK") log.debug("g_a and g_b validation: OK")
# https://core.telegram.org/mtproto/security_guidelines#checking-sha1-hash-values # https://core.telegram.org/mtproto/security_guidelines#checking-sha1-hash-values
answer = server_dh_inner_data.write() # Call .write() to remove padding answer = server_dh_inner_data.write() # Call .write() to remove padding
SecurityCheckMismatch.check(answer_with_hash[:20] == sha1(answer).digest()) SecurityCheckMismatch.check(
answer_with_hash[:20] == sha1(answer).digest(),
"answer_with_hash[:20] == sha1(answer).digest()"
)
log.debug("SHA1 hash values check: OK") log.debug("SHA1 hash values check: OK")
# https://core.telegram.org/mtproto/security_guidelines#checking-nonce-server-nonce-and-new-nonce-fields # https://core.telegram.org/mtproto/security_guidelines#checking-nonce-server-nonce-and-new-nonce-fields
# 1st message # 1st message
SecurityCheckMismatch.check(nonce == res_pq.nonce) SecurityCheckMismatch.check(nonce == res_pq.nonce, "nonce == res_pq.nonce")
# 2nd message # 2nd message
server_nonce = int.from_bytes(server_nonce, "little", signed=True) server_nonce = int.from_bytes(server_nonce, "little", signed=True)
SecurityCheckMismatch.check(nonce == server_dh_params.nonce) SecurityCheckMismatch.check(nonce == server_dh_params.nonce, "nonce == server_dh_params.nonce")
SecurityCheckMismatch.check(server_nonce == server_dh_params.server_nonce) SecurityCheckMismatch.check(
server_nonce == server_dh_params.server_nonce,
"server_nonce == server_dh_params.server_nonce"
)
# 3rd message # 3rd message
SecurityCheckMismatch.check(nonce == set_client_dh_params_answer.nonce) SecurityCheckMismatch.check(
SecurityCheckMismatch.check(server_nonce == set_client_dh_params_answer.server_nonce) nonce == set_client_dh_params_answer.nonce,
"nonce == set_client_dh_params_answer.nonce"
)
SecurityCheckMismatch.check(
server_nonce == set_client_dh_params_answer.server_nonce,
"server_nonce == set_client_dh_params_answer.server_nonce"
)
server_nonce = server_nonce.to_bytes(16, "little", signed=True) server_nonce = server_nonce.to_bytes(16, "little", signed=True)
log.debug("Nonce fields check: OK") log.debug("Nonce fields check: OK")
@ -248,6 +266,8 @@ class Auth:
log.info(f"Done auth key exchange: {set_client_dh_params_answer.__class__.__name__}") log.info(f"Done auth key exchange: {set_client_dh_params_answer.__class__.__name__}")
except Exception as e: except Exception as e:
log.info(f"Retrying due to {type(e).__name__}: {e}")
if retries_left: if retries_left:
retries_left -= 1 retries_left -= 1
else: else:

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@ -188,7 +188,8 @@ class Session:
self.auth_key_id, self.auth_key_id,
self.stored_msg_ids self.stored_msg_ids
) )
except SecurityCheckMismatch: except SecurityCheckMismatch as e:
log.info(f"Discarding packet: {e}")
return return
messages = ( messages = (