AW: OpenSSL 1.1.1: How to get signature algorithm id? (no EVP_MD_FLAG_PKEY_METHOD_SIGNATURE)

[Andrew Lynch]

That works, for both 1.1.1 and 1.0.2.  Thanks.

So I can do some spring cleaning and remove that particular #ifdef altogether...

Regards,
Andrew.

-----Ursprüngliche Nachricht-----
Von: Tomas Mraz <tomas at openssl.org> 
Gesendet: Samstag, 11. Februar 2023 14:24
An: Andrew Lynch <andrew.lynch at atos.net>; openssl-users at openssl.org
Betreff: Re: OpenSSL 1.1.1: How to get signature algorithm id? (no EVP_MD_FLAG_PKEY_METHOD_SIGNATURE)

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You can use OBJ_find_sigid_by_algs() and pass the
EVP_PKEY_base_id(pkey) and EVP_MD_type(md) values to it. It should find the signature algorithm id.

Tomas Mraz, OpenSSL

On Thu, 2023-02-09 at 15:21 +0000, Andrew Lynch via openssl-users
wrote:
> Hi,
>
> I have some old code that determines the signature algorithm OID given 
> a combination of EVP_PKEY *pkey and EVP_MD *digest.  It contains an 
> #ifdef EVP_MD_FLAG_PKEY_METHOD_SIGNATURE.  If true, it uses 
> OBJ_find_sigid_by_algs() with the digest and pkey->ameth-
> >pkey_id to get the OID.  The else case uses EVP_MD_pkey_type() with
> only the digest.
>
> Given an ECDSA pkey and a SHA256 digest the application using OpenSSL
> 1.0.2 outputs the expected ecdsa-with-SHA256.  With OpenSSL 1.1.1 it 
> incorrectly outputs sha256WithRSAEncryption.
>
> OpenSSL 1.0.2 has the flag defined whereas it does not exist at all in 
> 1.1.1.  As EVP_MD_pkey_type() only has the digest to work with it will 
> always return NID_sha256WithRSAEncryption regardless of the type of 
> EVP_PKEY that is actually used with the digest to create a signature.
>
> Which API calls can I use in OpenSSL 1.1.1 to get the correct 
> signature algorithm id given some combination of EVP_PKEY and EVP_MD?
>
> Regards,
> Andrew.
>

--
Tomáš Mráz, OpenSSL