Class: MTProto::EncryptedMessage

Inherits:
Object
  • Object
show all
Defined in:
lib/mtproto/encrypted_message.rb

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(auth_key_id:, msg_key:, encrypted_data:) ⇒ EncryptedMessage

Returns a new instance of EncryptedMessage.



10
11
12
13
14
 
# File 'lib/mtproto/encrypted_message.rb', line 10

def initialize(auth_key_id:, msg_key:, encrypted_data:)
  @auth_key_id = auth_key_id
  @msg_key = msg_key
  @encrypted_data = encrypted_data
end

Instance Attribute Details

#auth_key_id ⇒ Object (readonly)

Returns the value of attribute auth_key_id.



8
9
10
 
# File 'lib/mtproto/encrypted_message.rb', line 8

def auth_key_id
  @auth_key_id
end

#encrypted_data ⇒ Object (readonly)

Returns the value of attribute encrypted_data.



8
9
10
 
# File 'lib/mtproto/encrypted_message.rb', line 8

def encrypted_data
  @encrypted_data
end

#msg_key ⇒ Object (readonly)

Returns the value of attribute msg_key.



8
9
10
 
# File 'lib/mtproto/encrypted_message.rb', line 8

def msg_key
  @msg_key
end

Class Method Details

.decrypt(auth_key:, encrypted_message_data:, sender: :server) ⇒ Object 



40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
 
# File 'lib/mtproto/encrypted_message.rb', line 40

def self.decrypt(auth_key:, encrypted_message_data:, sender: :server)
  auth_key_id = encrypted_message_data[0, 8].unpack1('Q<')
  msg_key = encrypted_message_data[8, 16]
  encrypted_data = encrypted_message_data[24..]

  keys = Crypto::MessageKey.derive_aes_key_iv(auth_key, msg_key, sender: sender)

  plaintext = Crypto::AES_IGE.decrypt_ige(encrypted_data, keys[:aes_key], keys[:aes_iv])

  expected_msg_key = Crypto::MessageKey.generate_msg_key(auth_key, plaintext, sender: sender)
  raise 'msg_key mismatch!' unless msg_key == expected_msg_key

  offset = 0
  server_salt = plaintext[offset, 8].unpack1('Q<')
  offset += 8

  session_id = plaintext[offset, 8].unpack1('Q<')
  offset += 8

  msg_id = plaintext[offset, 8].unpack1('Q<')
  offset += 8

  seq_no = plaintext[offset, 4].unpack1('L<')
  offset += 4

  body_length = plaintext[offset, 4].unpack1('L<')
  offset += 4

  body = plaintext[offset, body_length]

  {
    auth_key_id: auth_key_id,
    msg_key: msg_key,
    server_salt: server_salt,
    session_id: session_id,
    msg_id: msg_id,
    seq_no: seq_no,
    body: body
  }
end

.encrypt(auth_key:, server_salt:, session_id:, msg_id:, seq_no:, body:) ⇒ Object 



16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
 
# File 'lib/mtproto/encrypted_message.rb', line 16

def self.encrypt(auth_key:, server_salt:, session_id:, msg_id:, seq_no:, body:)
  salt_bytes = [server_salt].pack('Q<')
  session_id_bytes = [session_id].pack('Q<')
  msg_id_bytes = [msg_id].pack('Q<')
  seq_no_bytes = [seq_no].pack('L<')
  body_length_bytes = [body.bytesize].pack('L<')

  plaintext = salt_bytes + session_id_bytes + msg_id_bytes + seq_no_bytes + body_length_bytes + body

  padding_length = (16 - (plaintext.bytesize % 16)) % 16
  padding_length += 16 if padding_length < 12
  plaintext += SecureRandom.random_bytes(padding_length)

  msg_key = Crypto::MessageKey.generate_msg_key(auth_key, plaintext, sender: :client)

  keys = Crypto::MessageKey.derive_aes_key_iv(auth_key, msg_key, sender: :client)

  encrypted_data = Crypto::AES_IGE.encrypt_ige(plaintext, keys[:aes_key], keys[:aes_iv])

  auth_key_id = Digest::SHA1.digest(auth_key)[-8..].unpack1('Q<')

  new(auth_key_id: auth_key_id, msg_key: msg_key, encrypted_data: encrypted_data)
end

Instance Method Details

#serialize ⇒ Object 



81
82
83
84
 
# File 'lib/mtproto/encrypted_message.rb', line 81

def serialize
  auth_key_id_bytes = [@auth_key_id].pack('Q<')
  auth_key_id_bytes + @msg_key + @encrypted_data
end