How to encode the digest output with base64 in python on GDAX

Question

I am trying to use the api on the GDAX exchange. On their website, they give this code:

# Requires python-requests. Install with pip:
#
#   pip install requests
#
# or, with easy-install:
#
#   easy_install requests

import json, hmac, hashlib, time, requests, base64
from requests.auth import AuthBase

# Create custom authentication for Exchange
class CoinbaseExchangeAuth(AuthBase):
def __init__(self, api_key, secret_key, passphrase):
    self.api_key = api_key
    self.secret_key = secret_key
    self.passphrase = passphrase

def __call__(self, request):
    timestamp = str(time.time())
    message = timestamp + request.method + request.path_url + (request.body or '')
    hmac_key = base64.b64decode(self.secret_key)
    signature = hmac.new(hmac_key, message, hashlib.sha256)
    signature_b64 = signature.digest().encode('base64').rstrip('\n')

    request.headers.update({
        'CB-ACCESS-SIGN': signature_b64,
        'CB-ACCESS-TIMESTAMP': timestamp,
        'CB-ACCESS-KEY': self.api_key,
        'CB-ACCESS-PASSPHRASE': self.passphrase,
        'Content-Type': 'application/json'
    })
    return request

api_url = 'https://api.gdax.com/'
auth = CoinbaseExchangeAuth(API_KEY, API_SECRET, API_PASS)

# Get accounts
r = requests.get(api_url + 'accounts', auth=auth)
print r.json()


# Place an order
order = {
'size': 1.0,
'price': 1.0,
'side': 'buy',
'product_id': 'BTC-USD',
}
r = requests.post(api_url + 'orders', json=order, auth=auth)
print r.json()

They also say to "Remember to first base64-decode the alphanumeric secret string (resulting in 64 bytes) before using it as the key for HMAC. Also, base64-encode the digest output before sending in the header."

I believe that I have fixed the first part with:

API_SECRET = base64.b64decode(b'{secret}')

However I do not understand what the second part means. I get the error message:

TypeError: Unicode-objects must be encoded before hashing

Answer 1

I used same code as user above who had the same issue and it didn't quite work but was close. All I had left to was after getting the secret =bytes(...) I still needed to secret = base64.b64decode(secret)

adding this line before signature fixed it for me

Answer 2

i had this same issue, this will help:

def __call__(self, request):
    timestamp = str(time.time())
    message = timestamp + request.method + request.path_url + (request.body or '')

    message = bytes(message, 'utf-8')
    secret = bytes(self.secret_key, 'utf-8')
    signature = base64.b64encode(hmac.new(secret, message, digestmod=hashlib.sha256).digest())

    request.headers.update({
        'CB-ACCESS-SIGN': signature,
        'CB-ACCESS-TIMESTAMP': timestamp,
        'CB-ACCESS-KEY': self.api_key,
        'CB-ACCESS-PASSPHRASE': self.passphrase,
        'Content-Type': 'application/json'
    })
    return request