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Decrypt files downloaded from CDNs (closes #208)

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This commit is contained in:
Lonami Exo 2017-08-24 15:50:44 +02:00
parent 940a2896e8
commit e5e7715a31
1 changed files with 12 additions and 2 deletions
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14
telethon/telegram_bare_client.py
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@ -488,6 +488,7 @@ class TelegramBareClient:
try: try:
offset_index = 0 offset_index = 0
cdn_redirect = None cdn_redirect = None
cdn_aes = None
while True: while True:
offset = offset_index * part_size offset = offset_index * part_size
@ -504,6 +505,15 @@ class TelegramBareClient:
if isinstance(result, FileCdnRedirect): if isinstance(result, FileCdnRedirect):
# https://core.telegram.org/cdn # https://core.telegram.org/cdn
cdn_redirect = result cdn_redirect = result
cdn_aes = pyaes.AESModeOfOperationCTR(
result.encryption_key
)
# The returned IV is the counter used on CTR
cdn_aes._counter._counter = list(
result.encryption_iv[:12] +
(offset >> 4).to_bytes(4, 'big')
)
client, cdn_file = self._get_cdn_client( client, cdn_file = self._get_cdn_client(
result.dc_id, result.dc_id,
GetCdnFileRequest( GetCdnFileRequest(
@ -535,8 +545,8 @@ class TelegramBareClient:
if cdn_redirect: if cdn_redirect:
# We first need to decrypt the result # We first need to decrypt the result
# TODO Decrypt the file, and use libssl if available # TODO Use libssl if available
pass result.bytes = cdn_aes.encrypt(result.bytes)
f.write(result.bytes) f.write(result.bytes)
if progress_callback: if progress_callback: