• Registered: 2021-06-27
  • Posts: 2

Topic: OpenSSL compatibility layer: Setting dhparams automatically

Hi,

I'm looking for a function which sets Diffie Hellman parameters automatically (same size as RSA key size in certificate).
OpenSSL provides a macro SSL_CTX_set_dh_auto() but I can't find an equivalent in WolfSSL.

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  • From: Mobile, AL
  • Registered: 2013-12-11
  • Posts: 352

Re: OpenSSL compatibility layer: Setting dhparams automatically

Hello Georg,

We do not have support for that specific openSSL API. We do handle setting the DH key size automatically during the key exchange:
src/internal.c :: GetDhPublicKey

#ifdef HAVE_FFDHE
    switch (ssl->options.dhKeySz) {
    #ifdef HAVE_FFDHE_2048
        case 2048/8:
            params = wc_Dh_ffdhe2048_Get();
            group = WOLFSSL_FFDHE_2048;
            break;
    #endif
.
.
.

If you are interested in opening a feature request for `SSL_CTX_set_dh_auto` in wolfSSL, please send an email to support@wolfssl.com

Thanks,
Eric @wolfSSL Support

embhorn's Website

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  • Registered: 2021-06-27
  • Posts: 2

Re: OpenSSL compatibility layer: Setting dhparams automatically

Hi Eric,

thanks for you answer! Does it mean if I don't set dhparam this will be handled automatically (and dhparam size will correspond to rsa key size of server certificate) ?

/Georg

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  • From: Mobile, AL
  • Registered: 2013-12-11
  • Posts: 352

Re: OpenSSL compatibility layer: Setting dhparams automatically

It will be handled automatically only as part of TLS handshake key exchange. If you are building keys, the size will need to be set manually.

embhorn's Website

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