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#!/usr/bin/env python3
"""
Simple password store, backed by a JSON file.
Also contains an entry point for managing the store.
"""
import hashlib
import json
import os
from typing import (
TypedDict,
)
def gen_salt(length: int = 10) -> str:
# urandom is stated to be suitable for cryptographic use.
return bytearray(os.urandom(length)).hex()
# Manual list of entries, to stop someone from executing arbitrary
# code by modyfying password database
hash_methods = {
'sha256': hashlib.sha256
}
class PasswordEntry(TypedDict):
hash: str
salt: str
# One of the keys of hash_methods
method: str
class Passwords:
"""
Simple password store.
[Parameters]
fname - Path of json file to load and store from.
"""
def __init__(self, fname: os.PathLike):
self.fname = fname
self.db: dict[str, PasswordEntry]
try:
with open(fname) as f:
self.db = json.load(f)
except Exception:
self.db = {}
def save(self) -> None:
"""Dump current data to disk."""
try:
with open(os.fspath(self.fname) + '.tmp', 'w') as f:
json.dump(self.db, f)
f.write('\n')
os.rename(os.fspath(self.fname) + '.tmp', self.fname)
except Exception as e:
print(f'Saving password failed {e}')
def add(self, username: str, password: str) -> None:
"""Add (or modify) entry in store."""
if cur := self.db.get(username):
salt = cur['salt']
hashed = hashlib.sha256((salt + password).encode('UTF-8'))
self.db[username] = {
'hash': hashed.hexdigest(),
'salt': salt,
'method': 'sha256',
}
else:
salt = gen_salt()
hashed = hashlib.sha256((salt + password).encode('UTF-8'))
self.db[username] = {
'hash': hashed.hexdigest(),
'salt': salt,
'method': 'sha256'
}
def validate(self, username: str, password: str) -> bool:
"""Check if user exists, and if it has a correct password."""
# These shall fail when key is missing
data = self.db.get(username)
if not data:
return False
proc = hash_methods[data['method']]
digest = proc((data['salt'] + password).encode('UTF-8')).hexdigest()
return data['hash'] == digest
def main() -> None:
import argparse
parser = argparse.ArgumentParser()
parser.add_argument('--file', default='passwords.json')
subparsers = parser.add_subparsers(dest='cmd')
add_parser = subparsers.add_parser('add')
add_parser.add_argument('username')
add_parser.add_argument('password')
val_parser = subparsers.add_parser('validate')
val_parser.add_argument('username')
val_parser.add_argument('password')
args = parser.parse_args()
passwords = Passwords(args.file)
if args.cmd == 'add':
passwords.add(args.username, args.password)
passwords.save()
elif args.cmd == 'validate':
print(passwords.validate(args.username, args.password))
else:
parser.print_help()
if __name__ == '__main__':
main()
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