Re: EVP_MAC_init - specify the hash algorithm

[Dr Paul Dale <pauli@xxxxxxxxxxx>]

    Please don't do it the PKEY way :)
    
    Your code should look more like:
> OSSL_PARAMS params[2];
>       EVP_MAC *mac = EVP_MAC_new(NULL, "HMAC",
>         NULL);
>       EVP_MAC_CTX *mac_ctx =
>         EVP_MAC_CTX_new(mac);
>       EVP_MAC_free(mac); /* Now or later is all
>         good and depends on the app reusing it or not */
>       
>       params[0] =
>         OSSL_PARAMS_construct_utf8_string("digest", "SHA256", 0);
>       params[1] = OSSL_PARAMS_construct_end();
>       
>       EVP_MAC_init(mac_ctx, key, key_len,
>         params);
>       EVP_MAC_update(mac_ctx, data1, data1_len);
>         EVP_MAC_update(mac_ctx, data2, data2_len);
>       EVP_MAC_update(mac_ctx, data3,
>         data3_len);
>       EVP_MAC_final(mac_ctx, out, &out_size,
>         out_len);
>       EVP_MAC_CTX_free(mac_ctx);
>     
    There are various other calls that tweak the flow but this is the
    basic idea.
    
    
    Pauli

On 14/7/21 8:48 am, Thomas Dwyer III wrote:

This seems to work for me in 3.0, passing the EVP_MD to EVP_DigestSignInit():

pkey = EVP_PKEY_new_mac_key()

EVP_DigestSignInit()

EVP_DigestSignUpdate()

EVP_DigestSignUpdate()

.

.

.

EVP_DigestSignFinal()

Regards,

Tom.III

On Tue, Jul 13, 2021 at 11:02 AM Ken Goldman <kgoldman@xxxxxxxxxx> wrote:

Porting to 3.0 ... HMAC_Init_ex() had a place for
the hash algorithm.  EVP_MAC_init() does not,
unless it's embedded in the 'params' parameter.

Any advice?  Or a sample for doing an
HMAC with 3.0?