How to use a .pfx file with Python requests – also works with .p12 files

use_pfx_with_requests.py

import contextlib
import OpenSSL.crypto
import os
import requests
import ssl
import tempfile

@contextlib.contextmanager
def pfx_to_pem(pfx_path, pfx_password):
    ''' Decrypts the .pfx file to be used with requests. '''
    with tempfile.NamedTemporaryFile(suffix='.pem') as t_pem:
        f_pem = open(t_pem.name, 'wb')
        pfx = open(pfx_path, 'rb').read()
        p12 = OpenSSL.crypto.load_pkcs12(pfx, pfx_password)
        f_pem.write(OpenSSL.crypto.dump_privatekey(OpenSSL.crypto.FILETYPE_PEM, p12.get_privatekey()))
        f_pem.write(OpenSSL.crypto.dump_certificate(OpenSSL.crypto.FILETYPE_PEM, p12.get_certificate()))
        ca = p12.get_ca_certificates()
        if ca is not None:
            for cert in ca:
                f_pem.write(OpenSSL.crypto.dump_certificate(OpenSSL.crypto.FILETYPE_PEM, cert))
        f_pem.close()
        yield t_pem.name

# HOW TO USE:
# with pfx_to_pem('foo.pem', 'bar') as cert:
#     requests.post(url, cert=cert, data=payload)

This only took me like three hours to figure out – posting it here in case it's useful to anyone else!

@erikbern thank you for this snippet! Works like a charm.

@erikbern, In my attempt p12.get_ca_certificates() returns None. I dont know much about it. Do you know what am I missing?

@talespadua lol I actually googled "python requests p12" right now, found my own gist (which I had forgotten about), and saw your comment. pretty weird coincidence given that you commented on it 40 minutes ago. i'll let you know if i figure out how to make it work

Looks like just filtering out all the missing certs is fine. Code has been updated

@erikbern Yeah, I just saw you commenting in a issue on similar subject. The code now appears to work, although I am having bad handshake for some reason. I can acess the website with selenium + firefox, but having a hard time with requests or selenium + phantomjs. Thanks you for the answer!

@erikbern I am new to python and am trying to send a request using the client cert. You code helps me understand how to attach the pfx. One thing I am confused is what get_cert() is used for? and how do I call the method pfx_to_pem.

Your quick response will help me.

I am getting error something like this - "PermissionError: [Errno 13] Permission denied:", can you please help?

@erikbern, 👍

Anyone get a ''tlsv1 alert unknown ca' error trying this?

👍 @erikbern

Nice! Exactly what I'm looking for, thanks a lot man!

If anyone's getting Permission denied or file not found error, and you're on Windows, you need to

1. Remove the open temp file line because NamedTemporaryFile opens it for you and it can't be opened again on Windows
2. Pass "delete=False" to NamedTemporaryFile as well, otherwise your key gets nuked after the file is closed.

@erikbern
hi, I have a .pfx file and I want to sign some data in PKCS7 format in python. In Java, it is done by first converting .pfx file to .jks(java key store) file and then I use .jks file to sign the data in PKCS7 format. how do I do this in Python?

Thanks @erikbern! This has saved me a good bit of troubleshooting time trying to figure out why my requests weren't working :)

So I got through the [Errno 13] issue (thanks @d1t69 for the heads up about delete=False), but it seems my credentials are being rejected. They work fine in Postman (Make the request, it asks me to pick my cert, then returns the info I need), so I assume something's going wrong with how it's translating the cert. I checked the contents of the generated .pem file, and the Certificate matches the .pem I used to make the .pfx file but the Key doesn't match the .key file (and trying to substitute that out for the original key gives an SSL Error about asn1 encoding issues).

I also tried this method to no avail. Any insight would be greatly appreciated!

@d1t69 would you mind posting your actual code adjustment I seem to be messing it up somewhere along the road

@daultonoryan On Windows, all I had to do was change Line 11 to with tempfile.NamedTemporaryFile(suffix='.pem', delete=False) as t_pem:

The file remains in the folder after the script runs if you leave it like this, so I guess either manually delete it or add a line to delete it after the loop wraps up to clean it out.

@erikbern works great and nice simple example of the implementation. Thank you for sharing 👍

I combined this with a hider based on: (https://benkurtovic.com/2014/06/01/obfuscating-hello-world.html)

that way at least the password is not there when you read the code

def pfx_helper(nIn):
    return (lambda f, n: f(f, n))(
        lambda f, n: chr(n % 256) + f(f, n // 256) if n else "",
        nIn)
def pfx_helperInverse(strInverse):
    codes = [ord(c) for c in strInverse]
    return sum(codes[i] * 256 ** i for i in range(len(codes)))

inverse = pfx_helperInverse("yourpasswordhere")
print ("pfx_helper(",inverse, ")")
print (pfx_helper(inverse))

# HOW TO USE:
# with pfx_to_pem('foo.pem', 'bar') as cert:
#     requests.post(url, cert=cert, data=payload)

Is it correct usage? What will happen, if you will send 100k signed requests?

This is a really nice workaround, but there is a library called requests_pkcs12 which does this job 🙂

This was a huge help! Thank You. Worked perfectly for me.

I am getting permission denier error upon executing this piece of code
but when i keep delete=False , pem is getting created and not getting deleted, upon executing with this i get SSL Error

I am getting error something like this - "OpenSSL.SSL.Error: [('memory buffer routines', 'BUF_MEM_grow_clean', 'malloc failure'), ('SSL routines', 'read_state_machine', 'BUF lib')]", can you please help? This error occurs every 1 week, more or less.
Thanks.

Thanks a lot

Worked fine just about 5 months ago and now when I try to run my program I am getting an error 'certificate verify failed'. Can you please help?? Any suggestions?
Certificates are up to date((

VOCÊ É UM ARROMBADO!!! Valeuuuuuuuu!

With this technique, for me anyway, I'm able to decrypt a .pfx file without error, but then it fails authentication when submitting to the server per the example, even though the same .pfx file with same password submits fine via Postman. Don't know why it won't work, but I used these instructions to "decompose" the .pfx into a pair of .pem files, and those can be submitted directly from python requests. And with that technique, you only have to do it once, not on every request.

It works on *nix machine but on Windows, it is giving error

[WinError 32] The process cannot access the file because it is being used by another process: 'C:\\path\to\\\tmpbnb1dy2v.pem'

For anyone having "Permission Denied" error, here is the fix (delete=False):

with tempfile.NamedTemporaryFile(suffix='.pem', dir=mainDir, delete=False) as t_pem:

with tempfile.NamedTemporaryFile(suffix='.pem') as t_pem:
        t_pem.close() # better solution on Windows than delete=False
        f_pem = open(t_pem.name, 'wb')