openssh_key_parser

Please don't use versions 0.0.1 - 0.0.5, which are affected by CVE-2022-31124, a High severity vulnerability. Upgrade to at least version 0.0.6.

This repository provides openssh_key, a Python package providing utilities to parse and pack OpenSSH private and public key files.

It supports parsing and packing keys of all types currently supported by OpenSSH:

• ssh-rsa
• ssh-ed25519
• ssh-dss
• ecdsa-sha2-{nistp256,nistp384,nistp521}
• sk-{ed25519,ecdsa-sha2-nistp256}@openssh.com FIDO/U2F security keys
• *[email protected] certificates

It can optionally encrypt and decrypt private keys using the bcrypt key derivation function and any cipher currently supported by OpenSSH:

• aes{128,192,256}-{ctr,cbc}
• aes{128,256}[email protected]
• [email protected]
• 3des-cbc

It is compliant with the OpenSSH private key vendor extension, in particular supporting multiple keys in a private key file.

Keys can be converted to corresponding classes provided by:

• cryptography
• pynacl

Check out the documentation.

Example

See what is in an OpenSSH key file

$ ssh-keygen -t ed25519 -N secret_passphrase -C my_comment -f test_id_ed25519
Generating public/private ed25519 key pair.
Your identification has been saved in test_id_ed25519.
Your public key has been saved in test_id_ed25519.pub.
The key fingerprint is:
SHA256:NbhmjL1RfNkYWOb63Rq2ugIzsmr9zLoSsn5ZUPa3Qic my_comment
The key's randomart image is:
+--[ED25519 256]--+
|           o+    |
|      o  o.o =   |
|     o .. = = .  |
|    .  +E+o+     |
|     ...S+..     |
|  . . oo=o.. . . |
|   o = o.=  . + .|
|  . = oo  .  . + |
| ..o.oo++  .ooo  |
+----[SHA256]-----+

$ python -m openssh_key test_id_ed25519 --passphrase secret_passphrase

{
    "data": [
        [
            {
                "header": {
                    "key_type": "ssh-ed25519"
                },
                "params": {
                    "data": {
                        "public": "b'\\xd0\\x96\\x7f\\xcd\\x02K\\x8e\\xfe)\\xc1\\xd1p\\x00\\xbd\\xcf\\xe3\\xf6\\xe8\\x91\\xc9\\x84\\xf5\\x9e\\xacL\\xe0\\x9c/2i8R'"
                    }
                },
                "footer": {},
                "clear": {}
            },
            {
                "header": {
                    "key_type": "ssh-ed25519"
                },
                "params": {
                    "data": {
                        "public": "b'\\xd0\\x96\\x7f\\xcd\\x02K\\x8e\\xfe)\\xc1\\xd1p\\x00\\xbd\\xcf\\xe3\\xf6\\xe8\\x91\\xc9\\x84\\xf5\\x9e\\xacL\\xe0\\x9c/2i8R'",
                        "private_public": "b'\\x99\\x08;#\\x07\\xb970\\xc3\\xeb\\\\\\x0e\\xe4\\xc1\\x1a\\xd4\\x12\\xa6\\x05\\x88v\\xae\\x9e9\\xc28\\x1a\\xb8\\x92b0\\x8c\\xd0\\x96\\x7f\\xcd\\x02K\\x8e\\xfe)\\xc1\\xd1p\\x00\\xbd\\xcf\\xe3\\xf6\\xe8\\x91\\xc9\\x84\\xf5\\x9e\\xacL\\xe0\\x9c/2i8R'"
                    }
                },
                "footer": {
                    "comment": "my_comment"
                },
                "clear": {}
            }
        ]
    ],
    "byte_string": "b'openssh-key-v1\\x00\\x00\\x00\\x00\\naes256-ctr\\x00\\x00\\x00\\x06bcrypt\\x00\\x00\\x00\\x18\\x00\\x00\\x00\\x10\\xfa\\xca\\x90\\x04\\x96\\x83\\xbb\\xe9\\x00\\x05\\'\\x8ev\\x06,t\\x00\\x00\\x00\\x10\\x00\\x00\\x00\\x01\\x00\\x00\\x003\\x00\\x00\\x00\\x0bssh-ed25519\\x00\\x00\\x00 \\xd0\\x96\\x7f\\xcd\\x02K\\x8e\\xfe)\\xc1\\xd1p\\x00\\xbd\\xcf\\xe3\\xf6\\xe8\\x91\\xc9\\x84\\xf5\\x9e\\xacL\\xe0\\x9c/2i8R\\x00\\x00\\x00\\x90\\xf9Iu\\x91\\x7f\\x82V\\xe1E2\\x98\\x17\\x82g8jmdy\\xabZz\\x85\\xa5\\xa1\\x05%\\x9a\\xdds\\x18/\\xd2[\\xad\\xd6\\xc6\\xe3\\xb14\\x92\\xa85\\x05BI#7\\x93#\\x07\\x9cu\\xe4\\xcb\\xccJ\\xe2\\x98\\xb4\\xde\\xf8\\x96\\x8f/)2P\\xef\\x02DgO\\x1d\\xe9\\x82\\xc2\\xa0D\\xbe\\x88\\xef\\xb4\\x86\\xbb\"I\\xc0\\x10\\x91\\xebT|\\x9a:\\xaf\\r6MZq\\xba\\xa7|r\\x17=\\xe7\\xaa\\xdeq.\\xa4\\xef\\xdc!\\x12N\\xdf\\x14\\x98\\xec-,~6\\x81.\\xa0\\xec\\xfe[.\\x17\\xf3z\\xbf\\xa1Q\\xbf\\xda\\xb3\\xeeY'",
    "header": {
        "auth_magic": "b'openssh-key-v1\\x00'",
        "cipher": "aes256-ctr",
        "kdf": "bcrypt",
        "kdf_options": "b\"\\x00\\x00\\x00\\x10\\xfa\\xca\\x90\\x04\\x96\\x83\\xbb\\xe9\\x00\\x05'\\x8ev\\x06,t\\x00\\x00\\x00\\x10\"",
        "num_keys": 1
    },
    "cipher_bytes": "b'\\xf9Iu\\x91\\x7f\\x82V\\xe1E2\\x98\\x17\\x82g8jmdy\\xabZz\\x85\\xa5\\xa1\\x05%\\x9a\\xdds\\x18/\\xd2[\\xad\\xd6\\xc6\\xe3\\xb14\\x92\\xa85\\x05BI#7\\x93#\\x07\\x9cu\\xe4\\xcb\\xccJ\\xe2\\x98\\xb4\\xde\\xf8\\x96\\x8f/)2P\\xef\\x02DgO\\x1d\\xe9\\x82\\xc2\\xa0D\\xbe\\x88\\xef\\xb4\\x86\\xbb\"I\\xc0\\x10\\x91\\xebT|\\x9a:\\xaf\\r6MZq\\xba\\xa7|r\\x17=\\xe7\\xaa\\xdeq.\\xa4\\xef\\xdc!\\x12N\\xdf\\x14\\x98\\xec-,~6\\x81.\\xa0\\xec\\xfe[.\\x17\\xf3z\\xbf\\xa1Q\\xbf\\xda\\xb3\\xeeY'",
    "kdf_options": {
        "salt": "b\"\\xfa\\xca\\x90\\x04\\x96\\x83\\xbb\\xe9\\x00\\x05'\\x8ev\\x06,t\"",
        "rounds": 16
    },
    "decipher_bytes": "b'\\xb1\\xe5\\x03+\\xb1\\xe5\\x03+\\x00\\x00\\x00\\x0bssh-ed25519\\x00\\x00\\x00 \\xd0\\x96\\x7f\\xcd\\x02K\\x8e\\xfe)\\xc1\\xd1p\\x00\\xbd\\xcf\\xe3\\xf6\\xe8\\x91\\xc9\\x84\\xf5\\x9e\\xacL\\xe0\\x9c/2i8R\\x00\\x00\\x00@\\x99\\x08;#\\x07\\xb970\\xc3\\xeb\\\\\\x0e\\xe4\\xc1\\x1a\\xd4\\x12\\xa6\\x05\\x88v\\xae\\x9e9\\xc28\\x1a\\xb8\\x92b0\\x8c\\xd0\\x96\\x7f\\xcd\\x02K\\x8e\\xfe)\\xc1\\xd1p\\x00\\xbd\\xcf\\xe3\\xf6\\xe8\\x91\\xc9\\x84\\xf5\\x9e\\xacL\\xe0\\x9c/2i8R\\x00\\x00\\x00\\nmy_comment\\x01\\x02\\x03'",
    "decipher_bytes_header": {
        "check_int_1": 2984575787,
        "check_int_2": 2984575787
    },
    "decipher_padding": "b'\\x01\\x02\\x03'"
}

$ python -m openssh_key test_id_ed25519.pub

[
    {
        "header": {
            "key_type": "ssh-ed25519"
        },
        "params": {
            "data": {
                "public": "b'\\xd0\\x96\\x7f\\xcd\\x02K\\x8e\\xfe)\\xc1\\xd1p\\x00\\xbd\\xcf\\xe3\\xf6\\xe8\\x91\\xc9\\x84\\xf5\\x9e\\xacL\\xe0\\x9c/2i8R'"
            }
        },
        "footer": {},
        "clear": {
            "key_type": "ssh-ed25519",
            "comment": "my_comment"
        }
    }
]

Manipulate a private key file

$ python

>>> import openssh_key.private_key_list as pkl
>>> sk_list = pkl.PrivateKeyList.from_string(open('test_id_ed25519').read(), passphrase='secret_passphrase')
>>> sk_list
[PublicPrivateKeyPair(public=<openssh_key.key.PublicKey object at 0x7fd0808f6400>, private=<openssh_key.key.PrivateKey object at 0x7fd07f781640>)]
>>> sk_list[0].private.footer
{'comment': 'my_comment'}
>>> sk_list[0].private.footer['comment'] = 'new_comment'
>>> _ = open('modified_test_id_ed25519', 'w').write(sk_list.pack_string(passphrase='new_secret_passphrase'))
>>> _ = open('modified_test_id_ed25519.pub', 'w').write(sk_list[0].public.pack_public_string())

Generate a private key

>>> pk_sk_pair = pkl.PublicPrivateKeyPair.generate('ssh-rsa', 'comment')
>>> generated_sk_list = pkl.PrivateKeyList.from_list([pk_sk_pair], cipher='aes256-ctr', kdf='bcrypt')
>>> _ = open('generated_test_id_rsa', 'w').write(generated_sk_list.pack_string(passphrase='secret_passphrase'))
>>> _ = open('generated_test_id_rsa.pub', 'w').write(generated_pk_key.pack_public_string())

Convert keys to external classes

>>> import cryptography.hazmat.primitives.asymmetric.rsa as rsa
>>> sk_params.convert_to(rsa.RSAPrivateKey)
<cryptography.hazmat.backends.openssl.rsa._RSAPrivateKey object at 0x7f74522fadc0>
>>> sk_params.convert_to(rsa.RSAPublicKey)
<cryptography.hazmat.backends.openssl.rsa._RSAPublicKey object at 0x7f74522faac0>

Tests

The package provides a full-coverage test suite and complete type annotations.

$ git clone https://github.com/scottcwang/openssh_key_parser.git
$ pip install .
$ pip install -r requirements-dev.txt
$ pytest

Changelog

0.0.7

• Fix - Support Python 3.9; migrate setup.cfg to pyproject.toml (@KOLANICH)

0.0.6

• Fix - Don't dump raw bytes in pascal_style_byte_stream exception message. Fixes CVE-2022-31124, a High severity vulnerability. (@mike-arnica)
• Fix - Raise ValueError instead of NotImplementedError

0.0.5

• Fix - Fix incorrect key type name for ecdsa-sha2-*
• Fix - Fix bad import of nacl.signing in ed25519
• Breaking change - The create_{cipher,kdf_options,public_key_params,private_key_params} factory methods are renamed to get_*_class
• Migrate to pyproject.toml

0.0.4

• Breaking change - The encrypt and decrypt methods of the Cipher class now take as arguments an instance of the KDF class and a passphrase (and no longer cipher_key and initialization_vector)
• Breaking change - The kdf module has been renamed to kdf_options
• Support aes128-ctr, aes192-ctr, aes128-cbc, aes192-cbc, aes256-cbc, 3des-cbc, [email protected], [email protected], and [email protected] ciphers for private key encryption
• Add a generate static method to PublicPrivateKeyPair
• Fix - Write an additional newline at the end of a private key file, which is required by OpenSSH ssh-keygen

0.0.3

• 0.0.2 and on requires Python >=3.10 (@FloLie)

0.0.2

• Support ssh-dss, ssh-ecdsa-*, sk-*@openssh.com (FIDO/U2F security key) and *[email protected] (certificate) key types

0.0.1

Initial release, supporting:

• ssh-rsa and ssh-ed25519 key types
• none and aes256-ctr ciphers for private keys
• none and bcrypt key derivation functions for ciphers
• OpenSSH key formats

Security

I'm grateful to Mike Doyle (@mike-arnica), Head of Security Research at Arnica.io, for performing a security review of version 0.0.5 of openssh_key_parser and finding CVE-2022-31124. Here's Mike's blog post about the process he undertook.

To report a vulnerability, please open a new draft security advisory.