> It isn't possible to do what you are wanting. RAND_METHOD replaces the RNG > everywhere. It cannot be done on a per thread process.
Well, technically it *is* possible. However, I'm still in doubt whether it is
really necessary and should be done.
The following example assumes you are compiling for linux (or another unix-ish
os) and using pthreads:
Assume that you recorded the thread id of your thread T1 (which you obtained
from pthread_create())
in the static variable 'tid1'. Then you could take the code from [1] and modify
it as follows:
```
static int my_rand_bytes(unsigned char *out, int count)
{
int ret;
if (pthread_equal(pthread_self(), tid1) {
// ... call your special RNG here
} else {
RAND_DRBG *drbg = RAND_DRBG_get0_public();
if (drbg == NULL)
return 0;
ret = RAND_DRBG_bytes(drbg, out, count);
}
return ret;
}
```
This is just a rough sketch, note that there are more RAND_METHODs to be
considered [2].
Matthias
[1]
https://github.com/openssl/openssl/blob/OpenSSL_1_1_1-stable/crypto/rand/drbg_lib.c#L958-L970
[2]
https://github.com/openssl/openssl/blob/OpenSSL_1_1_1-stable/crypto/rand/drbg_lib.c#L1146-L1153
From: openssl-users <openssl-users-boun...@openssl.org> On Behalf Of Dr Paul
Dale
Sent: Monday, April 5, 2021 3:18 AM
To: openssl-users@openssl.org
Subject: Re: openssl-users Digest, Vol 77, Issue 6
Vishwanath,
It isn't possible to do what you are wanting. RAND_METHOD replaces the RNG
everywhere. It cannot be done on a per thread process.
Pauli
On 4/4/21 9:55 pm, Vishwanath Mahajanshetty wrote:
Hi Paul,
Thanks for your response. I understand the concern for good random numbers; but
in this scenario when second thread calls SSL_CTX_new it is waiting forever in
RAND_priv_bytes(). Looks like entropy functions defined by first (bind) thread
are very specific for its own use case and can't be used by other treads.
So I am thinking of using default OpenSSL RAND_METHOD for second thread and
keep first thread (bind) to use its own random number generators.
Please let me know how can I make one thread use default RAND_METHOD and keep
other thread to use its own method. I have gone through RAND_bytes() and
drbg_bytes() but not getting enough idea. It would be really helpful if you
point out APIs which help me to achieve this requirement.
Thank You,
Vishwanath M
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