SSL handshake with a web server using Memory BIOs?
doa379 at gmail.com
Mon Oct 25 20:45:38 UTC 2021
Suppose the TLS layer is initialized in the form:
SSL_CTX *ctx = SSL_CTX_new(TLS_client_method());
BIO *r = BIO_new(BIO_s_mem());
BIO *w = BIO_new(BIO_s_mem());
SSL *ssl = SSL_new(ctx);
SSL_set_bio(ssl, r, w);
I want to use BIO so that I can control IO to/from the TCP layer
underneath using standard system-esque calls (connect(),
read(), write() on a socket fd).
The transfer itself is carried out through SSL_write() then followed by
BIO_read(), and BIO_write() followed by SSL_read() in/from the
respective BIO *w, *r.
This is all fine and dandy but how should the manual handshake be
Something akin to:
if ((nbytes = BIO_read(w, buffer, sizeof buffer)) > 0)
write(fd, buffer, nbytes);
else if ((nbytes = read(fd, buffer, sizeof buffer)) > 0)
BIO_write(r, buffer, nbytes);
Such a handshake can be put in wherever the server/client needs to
connect, eg called during initialization.
The handshake works fine when the client-server is on a localhost.
However when connecting to a web server the handshake takes long to
return and doesn't do the handshake either. So the question is, what
further provisions need to be made to connect to a non-local web server?
Or perhaps the above handshake should be integral to BIO_write() and
BIO_read() calls. I'm not sure, I have not looked at the actual
library sources as what SSL_() precisely does. Anyone care to send some
info my way in this particular case..?
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