How to import RSA keys by command line argument?

Question

I have been using Pycrypto module to generate RSA public/private key pair and trying to import keys by sending the public key as command line argument:

from Crypto.PublicKey import RSA
from Crypto import Random
import sys

input_key = sys.argv[1]
print('\n')
print(type(input_key))
print('\n')
print(input_key)
print('\n')

public_key = RSA.importKey(input_key)
print(type(public_key))

but I get the output:

$ python3 encrypt.py '-----BEGIN PUBLIC KEY-----\nMIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCaIRYO3hxr0ObcYcgKtxFequ6p\n9HVV8E95ghUUHmydVJYy16Ip9F6ik7G8wBU7X3VIfjdxHAtrwY9doCy8Ype6NNio\nS/ErGRtUQ1jgyT2f9okIdroEipnh1zwbXQcxveaxlwBhp7OFGZ/0W3FKgJLYtyzW\nEhfPO+8GkT0eLH5FaQIDAQAB\n-----END'
  >>> <class 'str'>

-----BEGIN PUBLIC KEY-----\nMIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCaIRYO3hxr0ObcYcgKtxFequ6p\n9HVV8E95ghUUHmydVJYy16Ip9F6ik7G8wBU7X3VIfjdxHAtrwY9doCy8Ype6NNio\nS/ErGRtUQ1jgyT2f9okIdroEipnh1zwbXQcxveaxlwBhp7OFGZ/0W3FKgJLYtyzW\nEhfPO+8GkT0eLH5FaQIDAQAB\n-----END PUBLIC KEY-----

   Traceback (most recent call last):
File "encrypt.py", line 13, in <module>
  public_key = RSA.importKey(input_key)
File "/usr/lib/python3/dist-packages/Crypto/PublicKey/RSA.py", line 638, in importKey
if lines[1].startswith(b('Proc-Type:4,ENCRYPTED')):
  IndexError: list index out of range

But when I copy paste the same key into Python Interpreter, I get these:

>>> input_key = '-----BEGIN PUBLIC KEY-----\nMIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCaIRYO3hxr0ObcYcgKtxFequ6p\n9HVV8E95ghUUHmydVJYy16Ip9F6ik7G8wBU7X3VIfjdxHAtrwY9doCy8Ype6NNio\nS/ErGRtUQ1jgyT2f9okIdroEipnh1zwbXQcxveaxlwBhp7OFGZ/0W3FKgJLYtyzW\nEhfPO+8GkT0eLH5FaQIDAQAB\n-----END PUBLIC KEY-----'
>>> pub_key = RSA.importKey(input_key)
>>> type(pub_key)
    <class 'Crypto.PublicKey.RSA._RSAobj'>

How to import them as a command line argument ?

You're supplying the wohle key as command line argument? You're probably losing the newline characters from the encoded key as your first argument only consists of one line. How exactly are you calling your program? — mata, Jan 31 '16 at 12:50
the whole key is input right, i have tried to input and print the key.. it works absolutely fine.. — Manuj Mittal, Jan 31 '16 at 12:55

mata · Accepted Answer · 2016-01-31T13:14:31.427

When you execute

$ python3 encrypt.py '-----BEGIN PUBLIC KEY-----\nMIG...'

the shell does not interpret \n as newline escapes, but as literal backslash+n, and that's what your program sees within sys.argv[1].

You can have newlines within en escaped shell string, so this should work:

$ python3 encrypt.py '-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCaIRYO3hxr0ObcYcgKtxFequ6p
9HVV8E95ghUUHmydVJYy16Ip9F6ik7G8wBU7X3VIfjdxHAtrwY9doCy8Ype6NNio
S/ErGRtUQ1jgyT2f9okIdroEipnh1zwbXQcxveaxlwBhp7OFGZ/0W3FKgJLYtyzW
EhfPO+8GkT0eLH5FaQIDAQAB
-----END PUBLIC KEY-----'

If you really want to use a string with escapes, you can either handle the escapes yourself in your program by doing input_key = sys.argv[1].replace('\\n', '\n'), or let the shell do the escaping e.g by passing the string through echo: $ python3 encrypt.py "$(echo -ne '-----BEGIN PUBLIC KEY-----\nMIG...')".

how to do this ? i tried **Shift+Enter** at the place of **\n** but it does'nt work.. — Manuj Mittal, Jan 31 '16 at 13:11
You shouldn't need to do anything special, when you press enter while within an unterminated string literal you should be able to resume on the next line. — mata, Jan 31 '16 at 13:15

How to import RSA keys by command line argument?

1 Answers1