bundlewrap/libs/ssh.py

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from base64 import b64decode, b64encode
from functools import lru_cache
from hashlib import sha3_224
from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey
from cryptography.hazmat.primitives.serialization import (
Encoding,
NoEncryption,
PrivateFormat,
PublicFormat,
)
from bundlewrap.utils import Fault
@lru_cache(maxsize=None)
def generate_ed25519_private_key(username, node):
return Fault(
f'private key {username}@{node.name}',
lambda username, node: _generate_ed25519_private_key(username, node),
username=username,
node=node,
)
@lru_cache(maxsize=None)
def generate_ed25519_public_key(username, node):
return Fault(
f'public key {username}@{node.name}',
lambda username, node: _generate_ed25519_public_key(username, node),
username=username,
node=node,
)
def _generate_ed25519_private_key(username, node):
privkey_bytes = Ed25519PrivateKey.from_private_bytes(_secret(username, node))
nondeterministic_privatekey = privkey_bytes.private_bytes(
encoding=Encoding.PEM,
format=PrivateFormat.OpenSSH,
encryption_algorithm=NoEncryption(),
).decode()
# get relevant lines from string
nondeterministic_bytes = b64decode(
''.join(nondeterministic_privatekey.split('\n')[1:-2])
)
# sanity check
if nondeterministic_bytes[98:102] != nondeterministic_bytes[102:106]:
raise Exception("checksums should be the same: whats going on here?")
# replace random bytes with deterministic values
random_bytes = sha3_224(_secret(username, node)).digest()[0:4]
deterministic_bytes = (
nondeterministic_bytes[:98]
+ random_bytes
+ random_bytes
+ nondeterministic_bytes[106:]
)
# reassemble file
deterministic_privatekey = '\n'.join(
[
'-----BEGIN OPENSSH PRIVATE KEY-----',
b64encode(deterministic_bytes).decode(),
'-----END OPENSSH PRIVATE KEY-----',
]
) + '\n'
return deterministic_privatekey
def _generate_ed25519_public_key(username, node):
return (
Ed25519PrivateKey.from_private_bytes(_secret(username, node))
.public_key()
.public_bytes(
encoding=Encoding.OpenSSH,
format=PublicFormat.OpenSSH,
)
.decode()
+ f' {username}@{node.name}'
)
@lru_cache(maxsize=None)
def _secret(username, node):
return b64decode(
str(
node.repo.vault.random_bytes_as_base64_for(
f"{username}@{node.name}", length=32
)
)
)