libsignal/sho.py

#
# Copyright (C) 2020 Signal Messenger, LLC.
# All rights reserved.
#
# SPDX-License-Identifier: GPL-3.0-only
#

import struct
import binascii
from hashlib import sha256

BLOCK_LEN = 64
HASH_LEN = 32
ZERO_PREFIX_SIZE = HASH_LEN
CHAIN_SIZE = HASH_LEN

# Encode integer as uint64 big-endian
def to_bytes8(x):
    return struct.pack('>Q', x)

def to_bytes2(x):
    return struct.pack('>H', x)

class SHO:

    def __init__(self, label=None):
        if label == None:
            label = bytearray(0)
        self.state = bytearray(ZERO_PREFIX_SIZE) + bytearray(CHAIN_SIZE)
        self.absorb(to_bytes2(len(label)) + label)
        self.pad_block()

    def absorb(self, data) :
        self.state += data

    def squeeze(self, outlen):
        inner_digest = sha256(self.state).digest()
        output = bytearray(0)
        counter = 0
        while counter * CHAIN_SIZE < outlen:
            counter += 1
            output += sha256(inner_digest + to_bytes8(counter) + to_bytes8(0)).digest()
        chain_key = sha256(inner_digest + to_bytes8(0) + to_bytes8(outlen)).digest()
        self.state = bytearray(ZERO_PREFIX_SIZE) + chain_key
        return output[:outlen]

    # Adds 0...BLOCKLEN-1 bytes to pad to BLOCKLEN
    def pad_block(self):
        pad_len = (BLOCK_LEN - (len(self.state) % BLOCK_LEN)) % BLOCK_LEN
        self.absorb(bytearray(pad_len))

if __name__ == "__main__":

    block31 = bytearray(31)
    block32 = bytearray(32)
    block33 = bytearray(33)
    block63 = bytearray(63)
    block64 = bytearray(64)
    block65 = bytearray(65)
    for i in range(31):
        block31[i] = i
    for i in range(32):
        block32[i] = i
    for i in range(33):
        block33[i] = i
    for i in range(63):
        block63[i] = i
    for i in range(64):
        block64[i] = i
    for i in range(65):
        block65[i] = i

    # empty label with different input lengths
    sho = SHO()
    out = sho.squeeze(16)
    assert(out == bytearray([0x5d, 0xd7, 0x7, 0x8, 0x6e, 0xed, 0x5b, 0xf, 0xf6, 0xaa, 0xb1, 0x5f, 0x5f, 0x6e, 0x27, 0x85]))

    sho = SHO()
    sho.absorb(block31)
    out = sho.squeeze(32)
    assert(out == bytearray([0xf3, 0x9a, 0x4e, 0x15, 0x19, 0x35, 0xbf, 0x73, 0x70, 0xfc, 0x35, 0xd3, 0xa2, 0xcc, 0x97, 0xa5, 0x11, 0x49, 0x5e, 0x65, 0x0, 0xdf, 0x70, 0x65, 0x1b, 0xf3, 0xc9, 0x6a, 0x2e, 0xaf, 0xb, 0x3]))

    sho = SHO()
    sho.absorb(block32)
    out = sho.squeeze(48)
    assert(out == bytearray([0x10, 0x70, 0xe2, 0x32, 0x1b, 0xbf, 0x56, 0xff, 0x5b, 0xef, 0xd2, 0xcb, 0x3, 0xd2, 0xd1, 0x5a, 0xd2, 0xff, 0x7, 0x11, 0xe3, 0x5d, 0xa0, 0x48, 0xd0, 0x14, 0x7f, 0x37, 0xb7, 0xa1, 0x0, 0xe8, 0x4a, 0x8c, 0xe7, 0xe1, 0x49, 0xf4, 0x9b, 0xdf, 0xbf, 0x71, 0xa8, 0xe6, 0xed, 0x49, 0xf6, 0xbe]))

    sho = SHO()
    sho.absorb(block33)
    out = sho.squeeze(64)
    assert(out == bytearray([0xa, 0xbd, 0x51, 0x9b, 0x17, 0x86, 0xf5, 0xa9, 0x4e, 0xc0, 0xc1, 0x97, 0x7b, 0xd, 0x34, 0xeb, 0xc7, 0xa4, 0x59, 0x1f, 0xf0, 0x40, 0x99, 0x89, 0xa4, 0xeb, 0xb2, 0xb7, 0xe2, 0x89, 0xf6, 0x9d, 0xc, 0x9a, 0x4d, 0xe6, 0x96, 0x15, 0x44, 0x55, 0x63, 0x49, 0x3e, 0xb8, 0xfc, 0x6b, 0x5a, 0x44, 0x6b, 0x74, 0x9f, 0x46, 0xce, 0x5, 0xed, 0x8e, 0x5f, 0xb, 0xb9, 0x88, 0x6, 0x74, 0x22, 0x52]))

    # longer labels with different input lengths
    sho = SHO(b"label")
    out = sho.squeeze(16)
    assert(out == bytearray([0xf7, 0xbc, 0xb8, 0xc0, 0xe0, 0xc, 0xa0, 0xb4, 0x65, 0xeb, 0xaf, 0x70, 0xeb, 0x4e, 0x98, 0x95]))

    sho = SHO(block31)
    sho.absorb(block63)
    out = sho.squeeze(33)
    assert(out == bytearray([0xde, 0xba, 0x7d, 0x15, 0x5a, 0x6a, 0x72, 0x1f, 0xf0, 0x4a, 0x8, 0x9a, 0x75, 0x2c, 0x74, 0x79, 0x55, 0xe7, 0x9c, 0x48, 0xc1, 0x37, 0xa9, 0x6d, 0x4d, 0xa, 0x62, 0x2c, 0x8, 0x57, 0x19, 0x7b, 0x2b]))

    sho = SHO(block32)
    sho.absorb(block64)
    out = sho.squeeze(47)
    assert(out == bytearray([0x31, 0x70, 0x44, 0x3b, 0x33, 0xfe, 0xae, 0xc3, 0xeb, 0xda, 0x58, 0xd4, 0xa0, 0x8c, 0xf8, 0x91, 0xee, 0x6c, 0x56, 0xf9, 0x13, 0xbe, 0xe1, 0x7b, 0xd1, 0x9e, 0xbc, 0xb0, 0x78, 0xa3, 0xf5, 0x33, 0x29, 0xf3, 0xb6, 0x32, 0xdf, 0x40, 0x53, 0x95, 0x5, 0x32, 0xe5, 0xeb, 0x5a, 0x66, 0xd3]))

    sho = SHO(block33)
    sho.absorb(block65)
    out = sho.squeeze(80)
    assert(out == bytearray([0x96, 0xe5, 0xf6, 0x1f, 0x94, 0x30, 0x1c, 0x34, 0x1, 0xfd, 0xe6, 0xdc, 0x26, 0x4b, 0x58, 0x59, 0x7f, 0x17, 0xdb, 0xe7, 0x4, 0x9f, 0x70, 0x4f, 0xf9, 0x1b, 0xb6, 0x2, 0xf6, 0xdc, 0xa3, 0x4b, 0x94, 0xfa, 0xf8, 0x2d, 0xed, 0xf5, 0x83, 0xf0, 0x1a, 0x28, 0x94, 0xe2, 0x62, 0xf2, 0x1d, 0x3c, 0x5d, 0x40, 0xab, 0x6, 0x7, 0xb2, 0x7f, 0x30, 0x1f, 0xab, 0x93, 0x6d, 0x57, 0xc, 0x94, 0x6e, 0xf7, 0x7f, 0xf9, 0xd7, 0xf7, 0x7f, 0x95, 0x44, 0x14, 0x0, 0x1d, 0x1a, 0x4b, 0xfe, 0x19, 0xe3]))

    sho = SHO(block64)
    sho.pad_block()
    sho.squeeze(64)
    sho.squeeze(17)
    sho.absorb(block31)
    sho.pad_block()
    sho.absorb(block32)
    sho.squeeze(128)
    sho.absorb(block33)
    sho.squeeze(32)
    sho.absorb(block31)
    sho.absorb(block31)
    sho.pad_block()
    sho.pad_block()
    sho.absorb(block32)
    sho.absorb(block32)
    sho.squeeze(1)
    sho.absorb(block63)
    sho.squeeze(33)
    sho.squeeze(31)
    sho.absorb(block64)
    sho.squeeze(1025)
    sho.absorb(block65)
    sho.squeeze(63)
    sho.absorb(bytearray(1))
    out = sho.squeeze(15)
    assert(out == bytearray([0x61, 0x6d, 0x7b, 0x38, 0xcf, 0xcf, 0xf8, 0x72, 0x70, 0x9d, 0x7f, 0xf5, 0x90, 0x9b, 0xde]))
    print "OK"