crypto

Documentation

Overview

Package crypto implements cryptographical primitives for MTproto.

Reference:

• https://core.telegram.org/mtproto/auth_key

Index

• func CheckDHParams(dhPrime, g, gA, gB *big.Int) error
• func DataWithHash(data []byte, randomSource io.Reader) ([]byte, error)
• func DecomposePQ(pq *big.Int, randSource io.Reader) (p, q *big.Int, err error)
• func GuessDataWithHash(dataWithHash []byte) []byte
• func InRange(x, min, max *big.Int) bool
• func Keys(authKey AuthKey, msgKey bin.Int128, mode Side) (key, iv bin.Int256)
• func MessageKey(authKey AuthKey, plaintextPadded []byte, mode Side) bin.Int128
• func NewSessionID(reader io.Reader) (int64, error)
• func ParseRSAPublicKeys(data []byte) ([]*rsa.PublicKey, error)
• func RSADecryptHashed(data []byte, key *rsa.PrivateKey) (r []byte)
• func RSAEncryptHashed(data []byte, key *rsa.PublicKey, randomSource io.Reader) ([]byte, error)
• func RSAFingerprint(key *rsa.PublicKey) int64
• func RandInt128(randSource io.Reader) (bin.Int128, error)
• func RandInt256(randSource io.Reader) (bin.Int256, error)
• func RandInt64(randSource io.Reader) (int64, error)
• func TempAESKeys(newNonce, serverNonce *big.Int) (key, iv []byte)
• type AuthKey
  • func (k AuthKey) AuxHash() [8]byte
  • func (k AuthKey) ID() [8]byte
  • func (k AuthKey) Zero() bool
• type Cipher
  • func NewClientCipher(rand io.Reader) Cipher
  • func NewServerCipher(rand io.Reader) Cipher
  • func (c Cipher) DecryptDataFrom(authKey AuthKey, sessionID int64, b *bin.Buffer) (*EncryptedMessageData, error)
  • func (c Cipher) DecryptMessage(authKey AuthKey, encrypted *EncryptedMessage) ([]byte, error)
  • func (c Cipher) EncryptDataTo(authKey AuthKey, data EncryptedMessageData, b *bin.Buffer) error
  • func (c Cipher) EncryptMessage(authKey AuthKey, plaintext []byte) (*EncryptedMessage, error)
  • func (c Cipher) Rand() io.Reader
• type EncryptedMessage
  • func (e *EncryptedMessage) Decode(b *bin.Buffer) error
  • func (e EncryptedMessage) Encode(b *bin.Buffer) error
• type EncryptedMessageData
  • func (e *EncryptedMessageData) Data() []byte
  • func (e *EncryptedMessageData) Decode(b *bin.Buffer) error
  • func (e EncryptedMessageData) Encode(b *bin.Buffer) error
• type Side
  • func (s Side) DecryptSide() Side

Functions

func CheckDHParams

func CheckDHParams(dhPrime, g, gA, gB *big.Int) error

CheckDHParams checks that g_a, g_b and g params meet key exchange conditions.

https://core.telegram.org/mtproto/auth_key#dh-key-exchange-complete

func DataWithHash

func DataWithHash(data []byte, randomSource io.Reader) ([]byte, error)

DataWithHash prepends data with SHA1(data) and 0..15 random bytes so result length is divisible by 16.

Use GuessDataWithHash(result) to obtain data.

func DecomposePQ

func DecomposePQ(pq *big.Int, randSource io.Reader) (p, q *big.Int, err error)

DecomposePQ decomposes pq into prime factors such that p < q.

func GuessDataWithHash

func GuessDataWithHash(dataWithHash []byte) []byte

GuessDataWithHash guesses data from data_with_hash.

func InRange

func InRange(x, min, max *big.Int) bool

InRange checks whether x is in (min, max) range, i.e. min < x < max.

func Keys

func Keys(authKey AuthKey, msgKey bin.Int128, mode Side) (key, iv bin.Int256)

Keys returns (aes_key, aes_iv) pair for AES-IGE.

Reference: * https://core.telegram.org/mtproto/description#defining-aes-key-and-initialization-vector

Example:

key, iv := crypto.Keys(authKey, messageKey, crypto.Client)
cipher, err := aes.NewCipher(key[:])
if err != nil {
	return nil, err
}
encryptor := ige.NewIGEEncrypter(cipher, iv[:])

func MessageKey

func MessageKey(authKey AuthKey, plaintextPadded []byte, mode Side) bin.Int128

MessageKey computes message key for provided auth_key and padded payload.

func NewSessionID

func NewSessionID(reader io.Reader) (int64, error)

NewSessionID generates new random int64 from reader.

Use crypto/rand.Reader if session id should be cryptographically safe.

func ParseRSAPublicKeys

func ParseRSAPublicKeys(data []byte) ([]*rsa.PublicKey, error)

ParseRSAPublicKeys parses data as list of PEM-encdoed public keys.

func RSADecryptHashed

func RSADecryptHashed(data []byte, key *rsa.PrivateKey) (r []byte)

RSADecryptHashed decrypts given data with RSA, prefixing with a hash.

func RSAEncryptHashed

func RSAEncryptHashed(data []byte, key *rsa.PublicKey, randomSource io.Reader) ([]byte, error)

RSAEncryptHashed encrypts given data with RSA, prefixing with a hash.

func RSAFingerprint

func RSAFingerprint(key *rsa.PublicKey) int64

RSAFingerprint returns fingerprint of RSA public key as defined in MTProto.

func RandInt128

func RandInt128(randSource io.Reader) (bin.Int128, error)

RandInt128 generates and returns new random 128-bit integer.

Use crypto/rand.Reader as randSource in production.

func RandInt256

func RandInt256(randSource io.Reader) (bin.Int256, error)

RandInt256 generates and returns new random 256-bit integer.

Use crypto/rand.Reader as randSource in production.

func RandInt64

func RandInt64(randSource io.Reader) (int64, error)

RandInt64 returns random int64 from randSource.

func TempAESKeys

func TempAESKeys(newNonce, serverNonce *big.Int) (key, iv []byte)

TempAESKeys returns tmp_aes_key and tmp_aes_iv based on new_nonce and server_nonce as defined in "Creating an Authorization Key".

Types

type AuthKey

type AuthKey [256]byte

AuthKey represents 2048-bit authorization key.

func (AuthKey) AuxHash

func (k AuthKey) AuxHash() [8]byte

AuxHash returns aux_hash value of key.

func (AuthKey) ID

func (k AuthKey) ID() [8]byte

ID returns auth_key_id.

func (AuthKey) Zero

func (k AuthKey) Zero() bool

Zero reports whether AuthKey is zero value.

type Cipher

type Cipher struct {
	// contains filtered or unexported fields
}

Cipher is message encryption utility struct.

func NewClientCipher

func NewClientCipher(rand io.Reader) Cipher

NewClientCipher creates new client-side Cipher.

func NewServerCipher

func NewServerCipher(rand io.Reader) Cipher

NewServerCipher creates new server-side Cipher.

func (Cipher) DecryptDataFrom

func (c Cipher) DecryptDataFrom(authKey AuthKey, sessionID int64, b *bin.Buffer) (*EncryptedMessageData, error)

DecryptDataFrom decrypts data from buffer with EncryptedMessage using AES-IGE.

func (Cipher) DecryptMessage

func (c Cipher) DecryptMessage(authKey AuthKey, encrypted *EncryptedMessage) ([]byte, error)

DecryptMessage decrypts data from encrypted message using AES-IGE.

func (Cipher) EncryptDataTo

func (c Cipher) EncryptDataTo(authKey AuthKey, data EncryptedMessageData, b *bin.Buffer) error

EncryptDataTo encrypts EncryptedMessageData using AES-IGE to given buffer.

func (Cipher) EncryptMessage

func (c Cipher) EncryptMessage(authKey AuthKey, plaintext []byte) (*EncryptedMessage, error)

EncryptMessage encrypts plaintext using AES-IGE.

func (Cipher) Rand

func (c Cipher) Rand() io.Reader

Rand returns random generator.

type EncryptedMessage

type EncryptedMessage struct {
	AuthKeyID [8]byte
	MsgKey    bin.Int128

	EncryptedData []byte
}

EncryptedMessage of protocol.

func (*EncryptedMessage) Decode

func (e *EncryptedMessage) Decode(b *bin.Buffer) error

Decode implements bin.Decoder.

func (EncryptedMessage) Encode

func (e EncryptedMessage) Encode(b *bin.Buffer) error

Encode implements bin.Encoder.

type EncryptedMessageData

type EncryptedMessageData struct {
	Salt                   int64
	SessionID              int64
	MessageID              int64
	SeqNo                  int32
	MessageDataLen         int32
	MessageDataWithPadding []byte
}

EncryptedMessageData is stored in EncryptedMessage.EncryptedData.

func (*EncryptedMessageData) Data

func (e *EncryptedMessageData) Data() []byte

Data returns message data without hash.

func (*EncryptedMessageData) Decode

func (e *EncryptedMessageData) Decode(b *bin.Buffer) error

Decode implements bin.Decoder.

func (EncryptedMessageData) Encode

func (e EncryptedMessageData) Encode(b *bin.Buffer) error

Encode implements bin.Encoder.

type Side

type Side byte

Side on which encryption is performed.

const (
	// Client side of encryption (e.g. messages from client).
	Client Side = 0
	// Server side of encryption (e.g. RPC responses).
	Server Side = 1
)

func (Side) DecryptSide

func (s Side) DecryptSide() Side

DecryptSide returns Side for decryption.