Re: Supporting Windows SChannel as OpenSSL replacement

Heikki Linnakangas wrote:

> I did again the refactoring you did back in 2006, patch attached.
> One thing I did differently: I moved the raw, non-encrypted,
> read/write functions to separate functions: pqsecure_raw_read and
> pqsecure_raw_write. Those functions encapsulate the SIGPIPE
> handling. The OpenSSL code implements a custom BIO, which calls to
> pqsecure_raw_read/write to do the low-level I/O. Similarly in the
> server-side, there are be_tls_raw_read and pg_tls_raw_write
> functions, which do the
> prepare_for_client_read()/client_read_ended() dance, so that the SSL
> implementation doesn't need to know about that.

I'm skimming over this patch (0001). There are some issues:

* You duplicated the long comment under the IDENTIFICATION tag that was
in be-secure.c; it's now both in that file and also in
be-secure-openssl.c. I think it should be removed from be-secure.c.
Also, the hardcoded DH params are duplicated in be-secure.c, but they
belong in -openssl.c only now.

* There is some mixup regarding USE_SSL and USE_OPENSSL in be-secure.c.
I think anything that's OpenSSL-specific should be in
be-secure-openssl.c only; any new SSL implementation will need to
implement all those functions. For instance, be_tls_init().
I imagine that if we select any SSL implementation, USE_SSL would get
defined, and each SSL implementation would additionally define its own
symbol. Unless the idea is to get rid of USE_OPENSSL completely, and
use only the Makefile bit to decide which implementation to use? If
so, then USE_OPENSSL as a preprocessor symbol is useless ...

* ssl_renegotiation_limit is also duplicated. But removing this one is
probably not going to be as easy as deleting a line from be-secure.c,
because guc.c depends on that one. I think that variable should be
defined in be-secure.c (i.e. delete it from -openssl) and make sure
that all SSL implementations enforce it on their own somehow.

The DISABLE_SIGPIPE thingy looks wrong in pqsecure_write. I think it
should be like this:

ssize_t
pqsecure_write(PGconn *conn, const void *ptr, size_t len)
{
ssize_t n;

#ifdef USE_SSL
if (conn->ssl_in_use)
{
DECLARE_SIGPIPE_INFO(spinfo);

DISABLE_SIGPIPE(conn, spinfo, return -1);

n = pgtls_write(conn, ptr, len);

RESTORE_SIGPIPE(spinfo);
}
else
#endif /* USE_OPENSSL */
{
n = pqsecure_raw_write(conn, ptr, len);
}

return n;
}

You are missing the restore call, and I moved the declaration inside the
ssl_in_use block since otherwise it's not useful. The other path is
fine since pqsecure_raw_write disables and restores the flag by itself.
Also, you're missing DECLARE/DISABLE/RESTORE in the ssl_in_use block in
pqsecure_read. (The original code does not have that code in the
non-SSL path. I assume, without checking, that that's okay.) I also
assume without checking that all SSL implementations would be fine with
this SIGPIPE handling.

Another thing that seems wrong is the REMEMBER_EPIPE stuff. The
fe-secure-openssl.c code should be setting the flag, but AFAICS only the
non-SSL code is doing it.

Thanks for working on this -- I'm sure many distributors will be happy
to be able to enable other, less license-broken TLS implementations.

--
Álvaro Herrera http://www.2ndQuadrant.com/
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