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Harden private key handling, owner only file and no stdout or log exposure #71

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Harden private key handling, owner only file and no stdout or log exposure #71

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3284577
Write the generated private key with owner only file permissions
quantova-inc Nov 2, 2026
932063c
Stop writing the generated private key to stdout and the debug log
quantova-inc Nov 2, 2026
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18 changes: 11 additions & 7 deletions encryption_helper/main.py
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
It handles the generation process, file I/O operations, and logging.
"""

import os
from pathlib import Path
from typing import Tuple
from cryptography.hazmat.primitives.asymmetric import rsa
Expand Down Expand Up @@ -64,23 +65,26 @@ def generate_rsa_key() -> Tuple[bytes, bytes]:
keys_dir = Path("keys/pem")
keys_dir.mkdir(parents=True, exist_ok=True)

# Write the private key to a file
with open(keys_dir / "private-key.pem", "wb") as file_out:
# Write the private key to a file with owner only permissions
private_key_path = keys_dir / "private-key.pem"
private_key_fd = os.open(
private_key_path, os.O_WRONLY | os.O_CREAT | os.O_TRUNC, 0o600
)
with os.fdopen(private_key_fd, "wb") as file_out:
file_out.write(private_key)
os.chmod(private_key_path, 0o600)

# Write the public key to a file
with open(keys_dir / "public-key.pem", "wb") as file_out:
file_out.write(public_key)

# Log the keys
# Log only the public key, the private key is never logged
logger.debug(f"Public key:\n{public_key.decode()}\n")
logger.debug(f"Private key:\n{private_key.decode()}\n")

# Print the keys to console
# Print only the public key, the private key is written to file only
print("Public key:")
print(public_key.decode())
print("\nPrivate key:")
print(private_key.decode())
print("\nPrivate key written to keys/pem/private-key.pem")

return public_key, private_key

Expand Down