Question

JWT with Python SDK giving "Could not unserialize key data."

Forum|Forum|1 year ago
May 21, 2025
10 replies
44 views

C

community-manager
Box Employee

I am using Python 3.5. Here is my code,which is straight out of the docs, followed by the error.

from boxsdk import JWTAuth

auth = JWTAuth(

client_id='k29xaarbpae4znkghpay6rsixiitg1xc',

client_secret='AajZ60HOdKhsuX0PRe0mkv5agV1J61sf',

enterprise_id='XXXXXXX',

jwt_key_id='XXXXX',

rsa_private_key_file_sys_path='C:\\Users\\H470722\\Documents\\Keys\\private_key.pem',

rsa_private_key_passphrase='XXXXXXX',

store_tokens=lambda x, y: None,

)

access_token = auth.authenticate_instance()

Error:

>>>

RESTART: C:/Users/H470722/Documents/EIV Reporting ETL/Python Scripts/BoxTest.py

From cffi callback :

Traceback (most recent call last):

File "C:\Users\H470722\AppData\Roaming\Python\Python35\site-packages\cryptography\hazmat\backends\openssl\backend.py", line 101, in _pem_password_cb

pw_buf[:len(ud.password)] = ud.password

TypeError: a bytes-like object is required, not 'str'

Traceback (most recent call last):

File "C:/Users/H470722/Documents/EIV Reporting ETL/Python Scripts/BoxTest.py", line 10, in

store_tokens=lambda x, y: None,

File "C:\Users\H470722\AppData\Roaming\Python\Python35\site-packages\boxsdk\auth\jwt_auth.py", line 102, in __init__

backend=default_backend(),

File "C:\Users\H470722\AppData\Roaming\Python\Python35\site-packages\cryptography\hazmat\primitives\serialization.py", line 20, in load_pem_private_key

return backend.load_pem_private_key(data, password)

File "C:\Users\H470722\AppData\Roaming\Python\Python35\site-packages\cryptography\hazmat\backends\multibackend.py", line 305, in load_pem_private_key

return b.load_pem_private_key(data, password)

File "C:\Users\H470722\AppData\Roaming\Python\Python35\site-packages\cryptography\hazmat\backends\openssl\backend.py", line 1084, in load_pem_private_key

password,

File "C:\Users\H470722\AppData\Roaming\Python\Python35\site-packages\cryptography\hazmat\backends\openssl\backend.py", line 1253, in _load_key

self._handle_key_loading_error()

File "C:\Users\H470722\AppData\Roaming\Python\Python35\site-packages\cryptography\hazmat\backends\openssl\backend.py", line 1325, in _handle_key_loading_error

raise ValueError("Could not unserialize key data.")

ValueError: Could not unserialize key data.

What am I doing wrong?

C

community-manager
Author
Box Employee
Forum|Forum|1 year ago
May 21, 2025

I'm also running into this same issue.

Like

C

community-manager
Author
Box Employee
Forum|Forum|1 year ago
May 21, 2025

I am not sure why you are seeing this error, but according to this thread it might be an issue with the format of the private key you are using.

Like

C

community-manager
Author
Box Employee
Forum|Forum|1 year ago
May 21, 2025

I was looking at the Box SDK and it looks like it's in the JWTAuth object (jwt_auth.py) specifically:

```

with open(rsa_private_key_file_sys_path) as key_file:
self._rsa_private_key = serialization.load_pem_private_key(
        key_file.read(),
        password=rsa_private_key_passphrase,
        backend=default_backend(),
    )

```

key_file.read() is passing it a string and it expects a bytes array (https://cryptography.io/en/latest/hazmat/primitives/asymmetric/serialization/#cryptography.hazmat.primitives.serialization.load_pem_private_key)

I am just manually writing my JWT Auth but I believe the key_file.read() should be wrapped with bytes.

```

with open(rsa_private_key_file_sys_path) as key_file:
self._rsa_private_key = serialization.load_pem_private_key(
        bytes(key_file.read()),
        password=rsa_private_key_passphrase,
        backend=default_backend(),
    )

```