SMTP on C: STARTTLS via OpenSSL

Posted by Jackell on Stack Overflow See other posts from Stack Overflow or by Jackell
Published on 2010-04-01T19:24:35Z Indexed on 2010/04/02 15:53 UTC
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Hi all! I am using openssl to build secure smtp connections to gmail.com:25. So I can successfully connect to the server and sends a command STARTTLS (I receive 220 2.0.0 Ready to start TLS). Then execute the following code without disconnecting:

SSL_METHOD* method = NULL;

SSL_library_init();
SSL_load_error_strings();

method = SSLv23_client_method();

ctx = SSL_CTX_new(method);
if (ctx == NULL)
{
    ERR_print_errors_fp(stderr);
}
SSL_CTX_set_options(ctx, SSL_OP_NO_SSLv2);
ssl = SSL_new(ctx);
if (!SSL_set_fd(ssl, socket))
{
        ERR_print_errors_fp(stderr);
        return;
}
if (ssl)
{

    if (SSL_connect((SSL*)ssl) < 1)
    {
        ERR_print_errors_fp(stderr);
    }
    // then i think i need to send EHLO
}

But after calling SSL_connect I get an error:

24953:error:140770FC:SSL routines:SSL23_GET_SERVER_HELLO:unknown protocol:s23_clnt.c:601:

If I use SSLv3_client_method I get an error:

18143:error:1408F10B:SSL routines:SSL3_GET_RECORD:wrong version number:s3_pkt.c:284.

And If TLSv1_client_method:

21293:error:1408F10B:SSL routines:SSL3_GET_RECORD:wrong version number:s3_pkt.c:284:

Why? What I do wrong?

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