sagecipher 0.7.0

Uses SSH agent to encrypt/decrypt arbitrary data

sagecipher (ssh agent cipher) provides an AES cipher, whose key is obtained by signing nonce data via SSH agent. The cipher is illustrated in the diagram below.

Contents

• Installation

• Usage

• Using sagecipher in a Python program

• Using the cli tool to provide on-demand decryption

Installation

pip install sagecipher

Usage

Before using, ssh-agent must be running with at least one ssh-key available for producing cipher key material:

$ source <(ssh-agent)
Agent pid 3710

$ ssh-add
Enter passphrase for /home/somebody/.ssh/id_rsa:
Identity added: /home/somebody/.ssh/id_rsa (/home/somebody/.ssh/id_rsa)

If ssh-agent is not available or does not have any keys available, expect to see a

sagecipher.cipher.SshAgentKeyError Exception:

>>> from sagecipher import *
>>> cfail = SshAgentCipher()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "sagecipher/cipher.py", line 101, in __init__
    signature = sign_via_agent(self.challenge, self.fingerprint)
  File "sagecipher/cipher.py", line 230, in sign_via_agent
    raise SshAgentKeyError(SshAgentKeyError.E_NO_KEYS)
sagecipher.cipher.SshAgentKeyError: SSH agent is not running or no keys are available

Using sagecipher in a Python program

>>> from sagecipher import Cipher
>>>
>>> # Encrypts using the first SSH key available from SSH agent...
>>> enc_text = Cipher.encrypt_string("hello, world")
>>> text = Cipher.decrypt_string(enc_text)
>>> text
"hello, world"

Using the cli tool to provide on-demand decryption to other tools

Check sagecipher --help for usage. By default, the ‘decrypt’ operation will create a FIFO file, and then start a loop to decrypt out to the FIFO whenever it is opened.

$ sagecipher encrypt - encfile
Key not specified.  Please select from the following...
[1] ssh-rsa AA:AA:AA:AA:AA:AA:AA:AA:AA:AA:AA:AA:AA:AA:AA:AA
Selection (1..2): [1]:
Reading from STDIN...

secret sauce
(CTRL-D)
$ sagecipher decrypt encfile
secret sauce
$ mkfifo decfile
$ sagecipher decrypt encfile decfile &
[1] 16753
$ cat decfile # decfile is just a FIFO
secret sauce
$