[Cryptography-dev] Extracting pub key from a csr

Glyph glyph at twistedmatrix.com
Fri Aug 30 01:57:54 EDT 2024 

You will note that https://cryptography.io/en/latest/hazmat/primitives/asymmetric/ed25519/#cryptography.hazmat.primitives.asymmetric.ed25519.Ed25519PrivateKey.public_key has parentheses after it in its description.  That's it.  You just forgot the parens.  i.e., try:

public_bytes = csr.public_key().public_bytes(
     encoding=serialization.Encoding.Raw,
     format=serialization.PublicFormat.Raw,
)

Hope that helps,

-g

> On Aug 29, 2024, at 8:59 PM, Robert Moskowitz <rgm at htt-consult.com> wrote:
> 
> I may know a lot about x.509 objects (and use openssl command line a lot), but I am a serious hack at anything python, so I am missing your point wrt what I need to do after reading in the csr to get a var that contains the public key in bytes I can use.
> 
> So, please, be a little understanding and convey some understanding to me.  I have spent a lot of hours trying to grok
> 
> https://cryptography.io/en/latest/hazmat/primitives/asymmetric/ed25519
> 
> And still come up short.
> 
> thanks
> 
> On 8/29/24 23:38, Paul Kehrer wrote:
>> public_key is a method on your csr object that returns the public_key,
>> not an attribute.
>> 
>> -Paul
>> 
>> On Thu, Aug 29, 2024 at 8:36 PM Robert Moskowitz <rgm at htt-consult.com> wrote:
>>> I tried that and:
>>> 
>>> public_bytes = public_key.public_bytes(
>>>      encoding=serialization.Encoding.Raw,
>>>      format=serialization.PublicFormat.Raw)
>>> 
>>>      public_bytes = public_key.public_bytes(
>>>                     ^^^^^^^^^^
>>> NameError: name 'public_key' is not defined
>>> 
>>> so I tried
>>> 
>>> public_bytes = csr.public_key.public_bytes(
>>>      encoding=serialization.Encoding.Raw,
>>>      format=serialization.PublicFormat.Raw)
>>> 
>>>      public_bytes = csr.public_key.public_bytes(
>>>                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>> AttributeError: 'builtin_function_or_method' object has no attribute
>>> 'public_bytes'
>>> 
>>> then
>>> 
>>> public_bytes = csr.public_bytes(
>>>      encoding=serialization.Encoding.DER)
>>> 
>>> b'0\x81\x8f0C\x02\x01\x000\x101\x0e0\x0c\x06\x03U\x04\x05\x13\x05x12240*0\x05\x06\x03+ep\x03!\x00*,\xeb\xfb\xde\x01|8\xc4\xfdv\xf5\xc8j-\x07;<\xa8OI\x16\x93\x0c\xe2\xb8\xf3\x9b\x9d\xbf\x8fm\xa0\x000\x05\x06\x03+ep\x03A\x00\xc6\xe4~\xbd\xf8\xe0\x01\x9b\xd8\xd1\xcc$\xe9;\x85Gd\x9eb\x98\xdds\xab\x00\xa2\x13-\xb14_\x93bK\x17\xecg\xca/,n\x12\x9eb\x04\x13\xce\xad\xe6\x95\x9fh\xf0\x05\x84\x9f-\xfa3\x06%L\xd0^\x03'
>>> 
>>> Which looks more like the whole csr, being to large to be 32 bytes.
>>> 
>>> 
>>> 
>>> 
>>> On 8/29/24 23:15, Alex Gaynor wrote:
>>>> All of our public key types have a public_bytes() method that can be
>>>> used to serialize the key as you wish:
>>>> https://cryptography.io/en/latest/hazmat/primitives/asymmetric/ed25519/#cryptography.hazmat.primitives.asymmetric.ed25519.Ed25519PublicKey.public_bytes
>>>> 
>>>> Alex
>>>> 
>>>> On Thu, Aug 29, 2024 at 11:12 PM Robert Moskowitz <rgm at htt-consult.com> wrote:
>>>>> I want a variable that is the bits of the public key so that if I print
>>>>> it, I get something like:
>>>>> 
>>>>> 0xf32938f7ff6918d5bbdc52483f31e3725875456a9aeb83f915461a5ea629acda
>>>>> 
>>>>> or whatever type that I can then change to what I need elsewhere.
>>>>> 
>>>>> On 8/29/24 23:02, Alex Gaynor wrote:
>>>>>> You're getting back the public key object for that CSR. When you say
>>>>>> you want the "public key itself" what do you mean?
>>>>>> 
>>>>>> Alex
>>>>>> 
>>>>>> On Thu, Aug 29, 2024 at 10:54 PM Robert Moskowitz <rgm at htt-consult.com> wrote:
>>>>>>> I have a csr with an eddsa25519 key:
>>>>>>> 
>>>>>>> -----BEGIN CERTIFICATE REQUEST-----
>>>>>>> MIGPMEMCAQAwEDEOMAwGA1UEBRMFeDEyMjQwKjAFBgMrZXADIQAqLOv73gF8OMT9
>>>>>>> dvXIai0HOzyoT0kWkwziuPObnb+PbaAAMAUGAytlcANBAMbkfr344AGb2NHMJOk7
>>>>>>> hUdknmKY3XOrAKITLbE0X5NiSxfsZ8ovLG4SnmIEE86t5pWfaPAFhJ8t+jMGJUzQ
>>>>>>> XgM=
>>>>>>> -----END CERTIFICATE REQUEST-----
>>>>>>> 
>>>>>>> I want the Pbkey of
>>>>>>> 
>>>>>>>            Subject Public Key Info:
>>>>>>>                Public Key Algorithm: ED25519
>>>>>>>                    ED25519 Public-Key:
>>>>>>>                    pub:
>>>>>>>                        e7:3f:5c:a1:b7:78:8a:75:e4:7b:91:4c:0c:1c:48:
>>>>>>>                        d7:f8:06:c1:f1:9d:58:b0:4d:c9:48:7f:3d:1d:bc:
>>>>>>>                        ac:16
>>>>>>> 
>>>>>>> I am following
>>>>>>> 
>>>>>>> https://cryptography.io/en/3.4.7/x509/reference.html#loading-certificate-signing-requests
>>>>>>> and
>>>>>>> https://cryptography.io/en/3.4.7/x509/reference.html#x-509-csr-certificate-signing-request-builder-object
>>>>>>> 
>>>>>>> I tried the following to get the key:
>>>>>>> 
>>>>>>> from cryptography.hazmat.primitives import serialization
>>>>>>> from cryptography.hazmat.primitives.asymmetric import ed25519
>>>>>>> from cryptography import x509
>>>>>>> from cryptography.x509.oid import NameOID
>>>>>>> from cryptography.hazmat.primitives.serialization import load_pem_private_key
>>>>>>> 
>>>>>>> with open(uacsr, "rb") as f:
>>>>>>>        pem_req_data = f.read()
>>>>>>>        csr = x509.load_pem_x509_csr(pem_req_data)
>>>>>>> csr_pbkey = csr.public_key()
>>>>>>> print(csr_pbkey)
>>>>>>> 
>>>>>>> and get:
>>>>>>> 
>>>>>>> <cryptography.hazmat.backends.openssl.ed25519._Ed25519PublicKey object at 0x7f513f0d39d0>
>>>>>>> 
>>>>>>> not the public key itself.
>>>>>>> 
>>>>>>> What am I missing here?
>>>>>>> 
>>>>>>> thanks
>>>>>>> 
>>>>>>> _______________________________________________
>>>>>>> Cryptography-dev mailing list
>>>>>>> Cryptography-dev at python.org
>>>>>>> https://mail.python.org/mailman/listinfo/cryptography-dev
>>> _______________________________________________
>>> Cryptography-dev mailing list
>>> Cryptography-dev at python.org
>>> https://mail.python.org/mailman/listinfo/cryptography-dev
>> _______________________________________________
>> Cryptography-dev mailing list
>> Cryptography-dev at python.org
>> https://mail.python.org/mailman/listinfo/cryptography-dev
> 
> _______________________________________________
> Cryptography-dev mailing list
> Cryptography-dev at python.org
> https://mail.python.org/mailman/listinfo/cryptography-dev

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mail.python.org/pipermail/cryptography-dev/attachments/20240829/eec338bc/attachment-0001.html>

More information about the Cryptography-dev mailing list