I'm working with an API provided by a client, who provided sample code on authorizing via C#, but my company works in Python. They authorize via HMAC, and following their sample code (on .net fiddle), I finally got to the point where our byte key and byte message match those of the C# call.
However, when we get to this in their code:
using (HMACSHA256 sha = new HMACSHA256(secretKeyByteArray))
{
// Sign the request
byte[] signatureBytes = sha.ComputeHash(signature);
Where our equivalent is
signature_hmac = hmac.new(
base64.b64decode(secretKey),
bytes(message, "utf8"),
digestmod=hashlib.sha256,
)
The byte value of their signatureBytes doesn't match with the byte value of our signature_hmac.digest(). If using the same hashing libraries, and the byte values of the inputs match, we should get the same result, right?
To make sure, when I say byte values match, the value of base64.b64decode(secretKey) (Python) matched var secretKeyByteArray = Convert.FromBase64String(secretKey); (C#).
Worked for me, make sure your input arrays are EXACTLY the same on both. I think you might be missing a base64 decode or encoding the strings differently.
Here's my 2 tests:
secretKey = "wxyz".encode()
message = "abcd".encode()
signature_hmac = hmac.new(
secretKey,
message,
digestmod=hashlib.sha256,
)
x = signature_hmac.hexdigest()
and C#
byte[] signatureBytes;
byte[] secretKeyByteArray = Encoding.UTF8.GetBytes("wxyz");
byte[] signature = Encoding.UTF8.GetBytes("abcd");
using (HMACSHA256 sha = new HMACSHA256(secretKeyByteArray))
{
signatureBytes = sha.ComputeHash(signature);
};
string x = Convert.ToHexString(signatureBytes);
Related
I'm writting a little program using SSL sockets. A client sends values to a server and when the server gets the value it checks the client's public key to make sure he's expected to send something. So at first the server is getting all the public keys like this :
cert = f.read()
crtObj = crypto.load_certificate(crypto.FILETYPE_PEM, cert)
pubKeyObject = crtObj.get_pubkey()
pubKeyString = crypto.dump_publickey(crypto.FILETYPE_PEM,pubKeyObject)
with this method, the public key is :
b'-----BEGIN PUBLIC KEY-----\nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA7GIzek5JgfFzFCGwnx7X\ncE4QULV/9uyoGgd9HbHYyYcItEcSPU39ORXCrNQGxh09k4oFPBYntjD2gIORF8V4\n6EAC10bFaT18OuM1F/37v+K/+BuvCDTqcS9Y0CRalwPFVYB+yttvZ8fnvO2l/TxF\nsLmZh0yY/ajaHxey/ppUQycGy4xA8XD6VlWFM7+I0t/19rrLN9iMFSym/TgYpBbn\nxyZel8rMW/ACS09nSprEu1BuI+myhhej+cuy3wU8byRTwANpqHxsx5cTwp642TVx\nBKbuO8GHAzEKcrFZnrKcsXr9emWV5ouYiVzehOT4Pd3I2W8qSy6x/Ovv/iS3ojT4\ndQIDAQAB\n-----END PUBLIC KEY-----\n'
and when the server wants to get it from the socket connection like this :
test1 = writer.get_extra_info('ssl_object')
der =test1.getpeercert(binary_form=True)
test = test1.getpeercert()
cert = x509.Certificate.load(der)
pubkey= cert.public_key.unwrap()
print(pem.armor("PUBLIC KEY", pubkey.contents).decode("ASCII"))
the public key printed is :
-----BEGIN PUBLIC KEY-----
AoIBAQDsYjN6TkmB8XMUIbCfHtdwThBQtX/27KgaB30dsdjJhwi0RxI9Tf05FcKs
1AbGHT2TigU8Fie2MPaAg5EXxXjoQALXRsVpPXw64zUX/fu/4r/4G68INOpxL1jQ
JFqXA8VVgH7K229nx+e87aX9PEWwuZmHTJj9qNofF7L+mlRDJwbLjEDxcPpWVYUz
v4jS3/X2uss32IwVLKb9OBikFufHJl6Xysxb8AJLT2dKmsS7UG4j6bKGF6P5y7Lf
BTxvJFPAA2mofGzHlxPCnrjZNXEEpu47wYcDMQpysVmespyxev16ZZXmi5iJXN6E
5Pg93cjZbypLLrH86+/+JLeiNPh1AgMBAAE=
-----END PUBLIC KEY-----
So I don't know if it's a matter of format or if it's really not the same public key I'm getting... but it should be.
Sorry for the long post and thank you very much for reading.
Most(if not all) base64 encoding variants use A-Z, a-z, 0-9 characters to represent data the total is 62 character and some base64 encodings varies in the last 2 characters but most of them use + and / which will complete 64. So the above 2 keys seems to be completely different and the second key is also padded because of = sign at end. The standard base64 encoding is RFC 4648 variant which use + and / and make padding as optional not mandatory like RFC 4880 openpgp base64 encoding.
It was in fact the same keys but the way of getting it was wrong : here the right one from the ssl object :
test1 = writer.get_extra_info('ssl_object')
der =test1.getpeercert(binary_form=True)
crtObj = crypto.load_certificate(crypto.FILETYPE_ASN1, der)
pubKeyObject = crtObj.get_pubkey()
pubKeyString = crypto.dump_publickey(crypto.FILETYPE_PEM, pubKeyObject)
I'm a little bit confused by what I need to do here for Python, but from the Yubikey API documentation for verifying Yubikeys that have YubiOTP the HMAC signature needs to be generated a specific way - from their documentation:
Generating signatures
The protocol uses HMAC-SHA-1 signatures. The HMAC key to use is the
client API key.
Generate the signature over the parameters in the message. Each
message contains a set of key/value pairs, and the signature is always
over the entire set (excluding the signature itself), and sorted in
alphabetical order of the keys. More precisely, to generate a message
signature do:
Alphabetically sort the set of key/value pairs by key order.
Construct a single line with each ordered key/value pair
concatenated using &, and each key and value contatenated with =. Do
not add any linebreaks. Do not add whitespace. For example:
a=2&b=1&c=3.
Apply the HMAC-SHA-1 algorithm on the line as an octet string using
the API key as key (remember to base64decode the API key obtained from
Yubico).
Base 64 encode the resulting value according to RFC 4648, for
example, t2ZMtKeValdA+H0jVpj3LIichn4=.
Append the value under key h to the message.
Now my understanding of their API from their documentation states the following valid request parameters:
id - the Client ID from Yubico API
otp - the YubiOTP value from the YubiOTP component of a yubikey.
h - the HMAC-SHA1 signature for the request
timestamp - empty does nothing, 1 includes the timestamp in the reply from the server
nonce - A 16 to 40 character long string with random unique data.
sl - a value of 0 to 100 indicating percentage of syncing required by client, or strings "fast" or "Secure" to use server values; if nonexistent server decides
timeout - # of seconds to wait for sync responses; let server decide if absent.
I have a total of two functions I'm trying to use to try and handle all these things and generate the URL. Namely, we the HMAC support function and the verify_url_generate which generates the URL (and API_KEY is statically coded - my API Secret Key from Yubico):
def generate_signature(message, key=base64.b64decode(API_KEY)):
message = bytes(message, 'UTF-8')
digester = hmac.new(key, message, hashlib.sha1)
digest = digester.digest()
signature = base64.urlsafe_b64encode(digest)
return str(signature, 'UTF-8')
def verify_url_generate(otp):
nonce = "".join(secrets.choice(ascii_lowercase) for _ in range(40))
data = OrderedDict(
{
"id": None,
"nonce": None,
"otp": None,
"sl": 50,
"timeout": 10,
"timestamp": 1
}
)
data['otp'] = otp
data['id'] = CLIENT_ID
data['nonce'] = nonce
args = ""
for key, value in data.items():
args += f"{key}={value}&"
sig = generate_signature(args[:-1])
url = YUBICO_API_URL + args + "&h=" + sig
print(url)
return
Any URL generated by this triggers a notice about "BAD_SIGNATURE" from the remote site - any URL generated minus the HMAC sig (h=) parameter works. So we know the issue isn't the URL, it's the HMAC signature.
Does anyone know what I'm doing wrong with my HMAC generation approach, by passing the HMAC sig generator the concatenated args from the ordered dict in key=value separated by & for each parameter format?
Can you try using standard_b64encode and then using urllib.parse.quote(url) in your final URL?
I ask because this page says that "As such, all parameters must be properly URL encoded. In particular, some base64 characters (such as "+") in the value fields needs to be escaped." which means it is expecting +(or %2B) in the args and does a unquote and then normal decode.
I need to access an API that uses JSON Web Tokens as their authentication method. Is there a good way to use a python code step to create this token then add that token as a header to a custom request webhook step?
My experience authenticating with APIs has been using the simple API key method. As such I first read your question and didn't fully understand. I decided to do some research and hopefully learn something along the way, and I certainly did. I share my findings and answer below:
For starters I began reading into JSON Web Tokens(JWT) which lead me to the JWT website, which was an excellent resource. It very clearly spells out the components that make up a JWT and how they need to be formatted, I would highly recommend having a look.
From the JWT website I found that a JWT is made up of three components:
A base64 URL safe encoded header.
A base64 URL safe encoded payload.
A base64 URL safe encoded signature.
All three of the above combined form the correctly formatted JWT. Fortunately the JWT website has a list of libraries made for Python. Unfortunately none of these third-party libraries are available in the vanilla Python offered by the Zapier code module. To get this done required reading some source code and leveraging what libraries we do have available. So after a few hours and lots of trial and error I was able to come up with the following solution for generating a correctly formatted JWT:
import hashlib
import hmac
import requests
from base64 import urlsafe_b64encode
def base64url_encode(payload):
if not isinstance(payload, bytes):
payload = payload.encode('utf-8')
encode = urlsafe_b64encode(payload)
return encode.decode('utf-8').rstrip('=')
def generate_JWT(header, payload, secret):
encoded_header = base64url_encode(header)
encoded_payload = base64url_encode(payload)
signature = hmac.new(secret,
encoded_header + "." + encoded_payload,
hashlib.sha256)
encoded_signature = base64url_encode(signature.digest())
return encoded_header + "." + encoded_payload + "." + encoded_signature
def get_request(url, jwt):
headers = {
"Authorization" : "Bearer " + jwt
}
result = requests.get(url, headers=headers)
return result
secret = "yoursecrettoken"
header = '{"alg":"HS256","typ":"JWT"}'
payload = '{"sub":"1234567890","name":"John Doe","iat":1516239022}'
jwt = generate_JWT(header, payload, secret)
response = get_request("https://SomeApiEndpoint.com/api/", jwt)
You can test the output of this against the JWT's debugger here.
Note: For the encoding to work properly for the header and payload objects you have to convert them to a string object. I tried doing this by calling the JSON.dumps() function and passing the dictionary objects, but when I encoded the return values they did not match what was shown on the JWT debugger. The only solution I could find was by wrapping the dictionary objects in quotations and ensuring there were no spaces within it.
And so with the JWT in hand you can use it in your Zapier Webhooks custom get request step, or you could save the zap and send the request in the same code module using Python's request library as I have in my code example.
Thanks for the learning opportunity, and I hope this helps.
I had a similar issue trying to generate and use a JWT in a custom integration. Unfortunately, this code above did not work for my situation. I'm currently using the below javascript and it seems to be functioning perfectly.
const toBase64 = obj => {
const str = JSON.stringify (obj);
return Buffer.from(str).toString ('base64');
};
const replaceSpecialChars = b64string => {
// this will match the special characters and replace them with url-safe substitutes
return b64string.replace (/[=+/]/g, charToBeReplaced => {
switch (charToBeReplaced) {
case '=':
return '';
case '+':
return '-';
case '/':
return '_';
}
});
};
const crypto = require('crypto');
const signatureFunction = crypto.createSign('RSA-SHA256');
const headerObj = {
alg: 'RS256',
typ: 'JWT',
};
const payloadObj = {
iat: Math.round(Date.now() / 1000), // lists the current Epoch time
exp: Math.round(Date.now() / 1000) + 3600, // adds one hour
sub: '1234567890'
name: 'John Doe'
};
const base64Header = toBase64(headerObj);
const base64Payload = toBase64(payloadObj);
const base64UrlHeader = replaceSpecialChars(base64Header);
const base64UrlPayload = replaceSpecialChars(base64Payload);
signatureFunction.write(base64UrlHeader + '.' + base64UrlPayload);
signatureFunction.end();
// The private key without line breaks
const privateKey = `-----BEGIN PRIVATE KEY-----
MIIJQwIBADANBgkqhkiG9w0BAQEFAASCCS0wggkpAgEAAoICAQC5Q+0Je6sZ6BuX
cTsN7pEzAaj4819UE7gM+Tf7U5AKHSKk3hN5UILtp5EuEO7h7H+lyknn/5txltA4
-----END PRIVATE KEY-----`;
const signatureBase64 = signatureFunction.sign(privateKey, 'base64');
const signatureBase64Url = replaceSpecialChars(signatureBase64);
console.log("Your JWT is: " + base64UrlHeader + "." + base64UrlPayload + "." + signatureBase64Url);
I have this code in a Zapier code-step prior to calling the custom integration and pass in the generated token object to authenticate the call.
Hopefully, this helps someone!
I am writing a basic TACACS client module. I can get the packets on the wire via struct.pack ok, as I've checked against wireshark. But I am not sure how to handle the byte-wise XOR of the md5 and not even sure if I am creating the hash properly. The RFCs for TACACS say take specific items from the TACACS header and 'secret key' and encrypt it five times, concatenating the previous hash during each run. See below
def encrypt(packet, tac_key):
key = packet[4:8] + bytes(tac_key, 'utf-8') + packet[:1] + packet[2:3]
h1 = md5()
h1.update(key)
hash = h1.digest()
previous = h1.digest()
for i in range(2, 6):
new = md5()
key = key + previous
new.update(key)
hash += new.digest()
previous = new.digest()
return hash
The packet has already been run through struct.pack
body = struct.pack(fmt, TAC_AUTHEN_LOGIN, TAC_PLUS_PRIV_LVL_USER, TAC_PLUS_AUTHEN_TYPE_PAP, TAC_PLUS_AUTHEN_SVC_LOGIN,
user_len, port_len, rem_addr_len, data_len, bytearray(user, 'utf-8'),
bytearray(port, 'utf-8'), bytearray(data, 'utf-8)'))
Is this the correct way to do this or should I not use struct.pack on the body of the packet and just encrypt it?
I was not generating a new pseudo_pad with server's response header. Therefore, the response remained obfuscated.
I have pkcs8_rsa_private_key file which generate by openssl from a rsa_private_key.pem file.
I need make a signature by the private key in python, make the same signature with below java code.
public static final String SIGN_ALGORITHMS = "SHA1WithRSA";
public static String sign(String content, String privateKey) {
String charset = "utf-8";
try {
PKCS8EncodedKeySpec priPKCS8 = new PKCS8EncodedKeySpec(
Base64.decode(privateKey));
KeyFactory keyf = KeyFactory.getInstance("RSA");
PrivateKey priKey = keyf.generatePrivate(priPKCS8);
java.security.Signature signature = java.security.Signature
.getInstance(SIGN_ALGORITHMS);
signature.initSign(priKey);
signature.update(content.getBytes(charset));
byte[] signed = signature.sign();
return Base64.encode(signed);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
PKCS#8 defines a way to encode and transport secret keys and it is not specific to OpenSSL; PKCS#1 defines a way to use an RSA key (no matter how it was loaded into your application, with PKCS#8 or not) to carry out and verify digital signature on data.
The piece of code you have does three things:
It decodes Base64 into PKCS#8
It decodes PKCS#8 into the actual key in memory (mind you may need to provide a passphrase here)
It performs PKCS#1 v1.5 signature using SHA-1 using said key
It encodes the signature in Base64
The example for PKCS#1 v1.5 signing in the API of PyCrypto does exactly steps #2 and #3.
from Crypto.Signature import PKCS1_v1_5 as pk
from Crypto.Hash import SHA
class Crypt(object):
pkcs8_private_key = RSA.importKey(open('pkcs8_rsa_private_key.pem', 'r').read())
def rsa_sign(cls, des_reqdata):
"""
#:param reqdata: request reqData
"""
h = SHA.new(des_reqdata)
signer = pk.new(cls.pkcs8_private_key)
signature = signer.sign(h)
return base64.b64encode(signature)