SSH public key parser
Project description
Major changes between versions 2 and 3
Dropped support for Python 2.6 and 3.3
Even in loose mode, DSA keys must be 1024, 2048, or 3072 bits (earlier this was looser)
The interface (API) is exactly the same
Usage
Native implementation for validating OpenSSH public keys.
Currently ssh-rsa, ssh-dss (DSA), ssh-ed25519 and ecdsa keys with NIST curves are supported.
Installation:
pip install sshpubkeys
or clone the repository and use
python setup.py install
Usage:
import sys from sshpubkeys import SSHKey ssh = SSHKey("ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAAAYQCxO38tKAJXIs9ivPxt7AY" "dfybgtAR1ow3Qkb9GPQ6wkFHQqcFDe6faKCxH6iDRteo4D8L8B" "xwzN42uZSB0nfmjkIxFTcEU3mFSXEbWByg78aoddMrAAjatyrh" "H1pON6P0= ojarva@ojar-laptop", strict=True) try: ssh.parse() except InvalidKeyError as err: print("Invalid key:", err) sys.exit(1) except NotImplementedError as err: print("Invalid key type:", err) sys.exit(1) print(ssh.bits) # 768 print(ssh.hash_md5()) # 56:84:1e:90:08:3b:60:c7:29:70:5f:5e:25:a6:3b:86 print(ssh.hash_sha256()) # SHA256:xk3IEJIdIoR9MmSRXTP98rjDdZocmXJje/28ohMQEwM print(ssh.hash_sha512()) # SHA512:1C3lNBhjpDVQe39hnyy+xvlZYU3IPwzqK1rVneGavy6O3/ebjEQSFvmeWoyMTplIanmUK1hmr9nA8Skmj516HA print(ssh.comment) # ojar@ojar-laptop print(ssh.options_raw) # None (string of optional options at the beginning of public key) print(ssh.options) # None (options as a dictionary, parsed and validated)
Parsing of authorized_keys files:
import os from sshpubkeys import AuthorizedKeysFile f = open(os.environ["HOME"] + "/.ssh/authorized_keys", "r") key_file = AuthorizedKeysFile(f, strict=False) for key in key_file.keys: print(key.key_type, key.bits, key.hash_sha512())
Options
Set options in constructor as a keywords (i.e., SSHKey(None, strict=False))
strict: defaults to True. Disallows keys OpenSSH’s ssh-keygen refuses to create. For instance, this includes DSA keys where length != 1024 bits and RSA keys shorter than 1024-bit. If set to False, tries to allow all keys OpenSSH accepts, including highly insecure 1-bit DSA keys.
skip_option_parsing: if set to True, options string is not parsed (ssh.options_raw is populated, but ssh.options is not).
disallow_options: if set to True, options are not allowed and it will raise an InvalidOptionsError.
Exceptions
NotImplementedError if invalid ecdsa curve or unknown key type is encountered.
- InvalidKeyError if any other error is encountered:
TooShortKeyError if key is too short (<768 bits for RSA, <1024 for DSA, <256 for ED25519)
TooLongKeyError if key is too long (>16384 for RSA, >1024 for DSA, >256 for ED25519)
InvalidTypeError if key type (“ssh-rsa” in above example) does not match to what is included in base64 encoded data.
MalformedDataError if decoding and extracting the data fails.
- InvalidOptionsError if options string is invalid.
- InvalidOptionNameError if option name contains invalid characters.
UnknownOptionNameError if option name is not recognized.
MissingMandatoryOptionValueError if option needs to have parameter, but it is absent.
Tests
See “tests/” folder for unit tests. Use
python setup.py test
or
python3 setup.py test
to run test suite. If you have keys that are not parsed properly, or malformed keys that raise incorrect exception, please send your public key to olli@jarva.fi, and I’ll include it. Alternatively, create a new issue or make a pull request in github.
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