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sept: implement cryptographic meme

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This commit is contained in:
Michael Scire 2019-02-20 06:54:44 -08:00
parent 5fe24b620d
commit f58f7c8a16
1 changed files with 29 additions and 4 deletions
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33
sept/sept-secondary/sept_sign.py
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@ -5,7 +5,31 @@ from Crypto.Cipher import AES
from Crypto.Hash import CMAC
import KEYS
def sign_encrypt_code(code, sig_key, enc_key, iv):
def shift_left_xor_rb(s):
N = int(s.encode('hex'), 16)
if N & (1 << 127):
N = ((N << 1) ^ 0x87) & 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
else:
N = ((N << 1) ^ 0x00) & 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
return ('%032x' % N).decode('hex')
def sxor(x, y):
return ''.join(chr(ord(a) ^ ord(b)) for a,b in zip(x, y))
def get_last_block_for_desired_mac(key, data, desired_mac):
assert len(desired_mac) == 0x10
k1 = shift_left_xor_rb(AES.new(key, AES.MODE_ECB).encrypt('\x00'*0x10))
if len(data) & 0xF:
k1 = shift_left_xor_rb(k1)
data += '\x80'
data += '\x00' * ((0x10 - (len(data) & 0xF)) & 0xF)
num_blocks = (len(data) + 0xF) >> 4
last_block = sxor(AES.new(key, AES.MODE_ECB).decrypt(desired_mac), k1)
if len(data) > 0x0:
last_block = sxor(last_block, AES.new(key, AES.MODE_CBC, '\x00'*0x10).encrypt(data)[-0x10:])
return last_block
def sign_encrypt_code(code, sig_key, enc_key, iv, desired_mac):
# Pad with 0x20 of zeroes.
code += '\x00' * 0x20
code_len = len(code)
@ -14,11 +38,12 @@ def sign_encrypt_code(code, sig_key, enc_key, iv):
code += '\x00' * (code_len - len(code))
# Add empty trustzone, warmboot segments.
code += '\x00'*0x1FE0
code += '\x00'* (0x1FE0 - 0x10)
pk11_hdr = 'PK11' + pk('<IIIIIII', 0x1000, 0, 0, code_len - 0x20, 0, 0x1000, 0)
pk11 = pk11_hdr + code
enc_pk11 = AES.new(enc_key, AES.MODE_CBC, iv).encrypt(pk11)
enc_pk11 = pk('<IIII', len(pk11), 0, 0, 0) + iv + enc_pk11
enc_pk11 = pk('<IIII', len(pk11) + 0x10, 0, 0, 0) + iv + enc_pk11
enc_pk11 += get_last_block_for_desired_mac(sig_key, enc_pk11, desired_mac)
enc_pk11 += CMAC.new(sig_key, enc_pk11, AES).digest()
return enc_pk11
@ -31,7 +56,7 @@ def main(argc, argv):
assert (len(code) & 0xF) == 0
# TODO: Support dev unit crypto
with open(argv[2], 'wb') as f:
f.write(sign_encrypt_code(code, KEYS.HOVI_SIG_KEY_PRD, KEYS.HOVI_ENC_KEY_PRD, KEYS.IV))
f.write(sign_encrypt_code(code, KEYS.HOVI_SIG_KEY_PRD, KEYS.HOVI_ENC_KEY_PRD, KEYS.IV, 'THANKS_NVIDIA_<3'))
return 0
if __name__ == '__main__':