Replicating a Chef Request with Python RSA
Goal: I need a Python 3 wrapper for the Chef REST API. Because its Python-3, PyChef is out of the question.
Problem: I am trying to replicate a Chef request using RSA Python. But I get an error message in the wrapper: Invalid signature for user or client 'XXX'.
I went to a wrapper trying to replicate the cURL script shown in Chef Authentication and Authorization with cURL using the RSA Python package: RSA Signing and Verification .
Here is my rewrite. It might be easier, but I started getting paranoid messages about line breaks and header order, so I added a few unnecessary things:
import base64
import hashlib
import datetime
import rsa
import requests
import os
from collections import OrderedDict
body = ""
path = "/nodes"
client_name = "anton"
client_key = "/Users/velvetbaldmime/.chef/anton.pem"
# client_pub_key = "/Users/velvetbaldmime/.chef/anton.pub"
hashed_body = base64.b64encode(hashlib.sha1(body.encode()).digest()).decode("ASCII")
hashed_path = base64.b64encode(hashlib.sha1(path.encode()).digest()).decode("ASCII")
timestamp = datetime.datetime.now().strftime("%Y-%m-%dT%H:%M:%SZ")
canonical_request = 'Method:GET\\nHashed Path:{hashed_path}\\nX-Ops-Content-Hash:{hashed_body}\\nX-Ops-Timestamp:{timestamp}\\nX-Ops-UserId:{client_name}'
canonical_request = canonical_request.format(
hashed_body=hashed_body, hashed_path=hashed_path, timestamp=timestamp, client_name=client_name)
headers = "X-Ops-Timestamp:{timestamp}\nX-Ops-Userid:{client_name}\nX-Chef-Version:0.10.4\nAccept:application/json\nX-Ops-Content-Hash:{hashed_body}\nX-Ops-Sign:version=1.0"
headers = headers.format(
hashed_body=hashed_body, hashed_path=hashed_path, timestamp=timestamp, client_name=client_name)
headers = OrderedDict((a.split(":", 2)[0], a.split(":", 2)[1]) for a in headers.split("\n"))
headers["X-Ops-Timestamp"] = timestamp
with open(client_key, 'rb') as privatefile:
keydata = privatefile.read()
privkey = rsa.PrivateKey.load_pkcs1(keydata)
with open("pubkey.pem", 'rb') as pubfile:
keydata = pubfile.read()
pubkey = rsa.PublicKey.load_pkcs1_openssl_pem(keydata)
signed_request = base64.b64encode(rsa.sign(canonical_request.encode(), privkey, "SHA-1"))
dummy_sign = base64.b64encode(rsa.sign("hello".encode(), privkey, "SHA-1"))
print(dummy_sign)
def chunks(l, n):
n = max(1, n)
return [l[i:i + n] for i in range(0, len(l), n)]
auth_headers = OrderedDict(("X-Ops-Authorization-{0}".format(i+1), chunk) for i, chunk in enumerate(chunks(signed_request, 60)))
all_headers = OrderedDict(headers)
all_headers.update(auth_headers)
# print('curl '+' \\\n'.join("-H {0}: {1}".format(i[0], i[1]) for i in all_headers.items())+" \\\nhttps://chef.local/nodes")
print(requests.get("https://chef.local"+path, headers=all_headers).text)
At each step I tried to check if the variables have the same results as their counterparts in the curl script.
The problem seems to be at the signing stage - there is a clear mismatch between the python output packages and my mac openssl tools. Due to this discrepancy, the Chief returns {"error":["Invalid signature for user or client 'anton'"]}
. Curl script with the same values and keys works fine.
dummy_sign = base64.b64encode(rsa.sign("hello".encode(), privkey, "SHA-1"))
from Python matters
N7QSZRD495vV9cC35vQsDyxfOvbMN3TcnU78in911R54IwhzPUKnJTdFZ4D/KpzyTVmVBPoR4nY5um9QVcihhqTJQKy+oPF+8w61HyR7YyXZRqmx6sjiJRffC4uOGb5Wjot8csAuRSeUuHaNTl6HCcfRKnwUZnB7SctKoK6fXv0skWN2CzV9CjfHByct3oiy/xAdTz6IB+fLIwSQUf1k7lJ4/CmLJLP/Gu/qALkvWOYDAKxmavv3vYX/kNhzApKgTYPMw6l5k1aDJGRVm9Ch/BNQbg1WfZiT6LK+m4KAMFbTORfEH45KGWBCj9zsyETyMCAtUycebjqMujMqEwzv7w==
whereas the output echo -n "hello" | openssl rsautl -sign -inkey ~/.chef/anton.pem | openssl enc -base64
is
WfoASF1f5DPT3CVPlWDrIiTwuEnjr5yCV+WIlbQLFmwm3nfhIqfTPLyTM56SwTSg CKdboVU4EBFxC3RsU2aPpELqRH6+Fnl2Tl273vo6kLzvC/8+tUBTdNZdzSPhx6S8 x+6wzVFXsd3QeGAWoHkEgTKodSByFzARnZFxO2JzUe4dnygijwruHdf9S4ldrRo6 eaShwaxuNzM0cIl+Umz5iym3cCD6GFL13njmXZs3cHRLesBtLKA7pNxJ1UDf2WN2 OK09aK+bHaM4jl5HeQ2SdNzBQIKvyDcxX4Divnf2I/0tzD16J6BEMGCfTfsI2f3K TVGulq81+sH9zo8lGnpDrw==
I could not find information on the default hashing algorithm in openssl for rsautl
, but I think it is SHA-1.
At this point I really don't know what way to look like, hope someone can help make it right.
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From Chef Authentication and Authorization with cURL ,
timestamp=$(date -u "+%Y-%m-%dT%H:%M:%SZ")
the time is in UTC, so in Python it should be
timestamp = datetime.datetime.now(datetime.timezone.utc).strftime("%Y-%m-%dT%H:%M:%SZ")
openssl
Python equivalent,
dummy_sign = base64.b64encode(rsa.sign("hello".encode(), privkey, "SHA-1"))
there is
echo -n hello|openssl dgst -sha1 -sign ~/.chef/anton.pem -keyform PEM|openssl enc -base64
In Python code, you sign the message with the SHA-1 message of the message. This is called a separate signature.
echo -n "hello" | openssl rsautl -sign -inkey ~/.chef/anton.pem | openssl enc -base64
but this sign signs the entire message without digesting.
Python module rsa
has no equivalent openssl rsautl -sign
. Therefore, I have defined a function to fill this space.
from rsa import common, transform, core, varblock
from rsa.pkcs1 import _pad_for_signing
def pure_sign(message, priv_key):
'''Signs the message with the private key.
:param message: the message to sign. Can be an 8-bit string or a file-like
object. If ``message`` has a ``read()`` method, it is assumed to be a
file-like object.
:param priv_key: the :py:class:`rsa.PrivateKey` to sign with
:return: a message signature block.
:raise OverflowError: if the private key is too small to contain the
requested hash.
'''
keylength = common.byte_size(priv_key.n)
padded = _pad_for_signing(message, keylength)
payload = transform.bytes2int(padded)
encrypted = core.encrypt_int(payload, priv_key.d, priv_key.n)
block = transform.int2bytes(encrypted, keylength)
return block
Test;
OpenSSL
echo -n hello|openssl rsautl -sign -inkey .chef/anton.pem |base64
foIy6HVpfIpNk4hMYg8YWCEZwZ7w4Qexr6KXDbJ7/vr5Jym56joofkn1qUak57iSercqQ1xqBsIT
fo6bDs2suYUKu15nj3FRQ54+LcVKjDrUUEyl2kfJgVtXLsdhzYj1SBFJZnbz32irVMVytARWQusy
b2f2GQKLTogGhCywFFyhw5YpAHmKc2CQIHw+SsVngcPrmVAAtvCZQRNV5zR61ICipckNEXnya8/J
Ga34ntyELxWDradY74726OlJSgszpHbAOMK02C4yx7OU32GWlPlsZBUGAqS5Tu4MSjlD1f/eQBsF
x/pn8deP4yuR1294DTP7dsZ9ml64ZlcIlg==
Python
base64.b64encode(pure_sign.pure_sign(b'hello',prik)).decode()
'foIy6HVpfIpNk4hMYg8YWCEZwZ7w4Qexr6KXDbJ7/vr5Jym56joofkn1qUak57iSercqQ1xqBsITfo6bDs2suYUKu15nj3FRQ54+LcVKjDrUUEyl2kfJgVtXLsdhzYj1SBFJZnbz32irVMVytARWQusyb2f2GQKLTogGhCywFFyhw5YpAHmKc2CQIHw+SsVngcPrmVAAtvCZQRNV5zR61ICipckNEXnya8/JGa34ntyELxWDradY74726OlJSgszpHbAOMK02C4yx7OU32GWlPlsZBUGAqS5Tu4MSjlD1f/eQBsFx/pn8deP4yuR1294DTP7dsZ9ml64ZlcIlg=='
Change the line;
signed_request = base64.b64encode(rsa.sign(canonical_request.encode(), privkey, "SHA-1"))
to
signed_request = base64.b64encode(pure_sign(canonical_request.encode(), privkey))
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I recently wrote a chef client library for python 2.7 and 3.x built on top of pyca / cryptography and requests . It includes built-in support for the chef authentication protocol :
https://github.com/samstav/okchef
>>> import chef
>>>
>>> client = chef.ChefClient('https://api.opscode.com')
>>> client.authenticate('chef-user', '~/chef-user.pem')
>>> response = client.get('/users/chef-user')
>>> print(response.json())
{'display_name': 'chef-user',
'email': 'chef-user@example.com',
'first_name': 'Chef',
'last_name': 'User',
'middle_name': '',
'public_key': '-----BEGIN PUBLIC KEY-----\nMIIBIj...IDAQAB\n-----END PUBLIC KEY-----\n',
'username': 'chef-user'}
I created a separate repository for the code that handles the rsa / authentication bits:
https://github.com/samstav/requests-chef
The nuts and bolts for the auth implementation are in this file:
https://github.com/samstav/requests-chef/blob/master/requests_chef/mixlib_auth.py
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You can automate your interaction with the chef - using these tools:
Note:
As pointed out jww
, the OP mentioned that he doesn't want to use Selenium.
However, I wanted my answer to be complete (it can be used by others (including me) besides the OP), I included Selenium in the list.
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