HMAC DRBG incorrect output

Mbed TLS Crypto and SSL questions
4

@roneld01: Thanks for the wonderful explanation.
Now I’ve updated my code to look like hmac_drbg you mentioned in the comment above. I’m using hmac_drbg_pr() as my reference.

My mbedtls_test_entropy_func() now matches whatever is in that file. Apart from that, all my calls match hmac_drbg_pr() from the file you mentioned.

    mbedtls_hmac_drbg_init (&hmac_ctx);
    md_info = mbedtls_md_info_from_type( MBEDTLS_MD_SHA1 );
    p_entropy.p = entropy_inputs;
    p_entropy.len = strlen(entropy_inputs);

    rc = mbedtls_hmac_drbg_seed( &hmac_ctx, md_info, mbedtls_test_entropy_func, entropy_inputs, nonce_pers, strlen(nonce_pers) );
    
    mbedtls_hmac_drbg_set_prediction_resistance(&hmac_ctx, MBEDTLS_HMAC_DRBG_PR_ON );
    
    rc = mbedtls_hmac_drbg_random_with_add(&hmac_ctx, result, resultLen, addInput1, addInputLength);
    rc = mbedtls_hmac_drbg_random_with_add(&hmac_ctx, result, resultLen, addInput2, addInputLength);

It exactly matches hmac_drbg_pr(). However, I get an error in entropy function at line memcpy( buf, ctx->p, len );

I’ve printed the values:

(gdb) print len
$2 = 24
(gdb) print ctx->len
$3 = 11840012698478436789

ctx->len seems to be wrong. May be that’s what is causing the error?

entropy_ctx *ctx = (entropy_ctx *) data;
This line is not assigning anything to ctx->len is it?
In mbedtls_test_entropy_func() we just declare ctx of type entropy_ctx and assign data to it but nothing is assigned to ctx->len.