SSL_accept() Not Working

Question

I have researched for a while now, and didn't see my exact same problem anywhere. I'm just having a specific, quite simple problem: whenever my echo_server tries to run SSL_accept() function, it won't block the server waiting for a client to connect, function will just return 0, and if I go into SSL_get_error(), it will give me SSL_ERROR_SYSCALL, so I'm guessing the problem is, quoting from the manual, "an EOF was observed that violates the protocol."

Truth is I have no idea what does that mean, and it's getting really frustrating because I think I'm missing something very simple, but I don't know what.

Here's the code for my accept function (SSL_ctx previously initialized and socket opened):

SSL * sslconnection;

if((sslconnection = SSL_new(ctx)) == NULL){
    return NULL;
}

if(SSL_set_fd(sslconnection, socketd) != 1){
    return NULL;
}

if(SSL_accept(sslconnection) != 1){
    return NULL;
}

return sslconnection;

Also, I've tried to check my certificates with "openssl verify -verbose -purpose sslserver -CAfile 'CACertificate' 'ServerCertificate'", but it would say my Server Certificate is ok.

Any help is welcome, thanks in advance. Hope it's something really stupid and I'm just so obfuscated I can't see it.

Answer 1

whenever my echo_server tries to run SSL_accept() function, it won't block the server waiting for a client to connect

SSL_accept does not call accept for you. It expects that accept has already been called.

The correct sequence of calls is:

1. socket
2. bind
3. listen
4. accept
5. SSL_new
6. SSL_set_fd
7. SSL_accept

Download openssl sources from https://www.openssl.org/source/ and see demos/ssl/serv.cpp.