OSSL api example to write DH params

[Samiya Khanum via openssl-users <openssl-users@xxxxxxxxxxx>]

Hi All,

"PEM_write_DHparams" is deprecated in openssl3.0. 

I am trying to replace "PEM_write_DHparams" with the OSSL api. But  getting below compilation error while assigning the dh.

Could you please provide an example to use "OSSL_ENCODER_CTX_new_for_pkey" in the correct way and also please provide your inputs on the below error.

FYI, I have included the openssl/evp.h and openssl/dh.h header files.

error: dereferencing pointer to incomplete type
       dh = pkey->pkey.dh;
                ^

PEM_write_DHparams code is replaced with OSSL_ENCODER_CTX_new_for_pkey.

 EVP_PKEY *pkey = NULL;
 OSSL_ENCODER_CTX *ectx = NULL;

 ectx = OSSL_ENCODER_CTX_new_for_pkey(pkey,
                                         OSSL_KEYMGMT_SELECT_DOMAIN_PARAMETERS,
                                         "PEM",
                                         NULL, NULL);

    if (NULL != ectx)
    {
      if (!OSSL_ENCODER_to_fp(ectx, fp))
      {
        OSSL_ENCODER_CTX_free(ectx);
        EVP_PKEY_free(dhkey);
        fclose(fp);
        return ;
      }
      dh = pkey->pkey.dh;
    }

Thanks & Regards,

Samiya khanum

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