[Cryptography-dev] Extracting pub key from a csr

[Robert Moskowitz]

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
>>>>>>
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