I have a server application which uses OpenSSL (0.9.9-current as of about
four months ago) in nonblocking mode.
As a test, I added an option to call SSL_renegotiate every 100 successful
SSL_read or SSL_write calls. I am seeing very strange behavior and I wonder
if SSL_renegotiate actually works in non-blocking mode.
My application normally uses SSL_MODE_ENABLE_PARTIAL_WRITE to avoid
pointless trips around its select loop (the application can generate 32K
of data at a time, so without PARTIAL_WRITE, I end up selecting twice and
calling SSL_write twice for every write, since it always rejects a write
of 32K the first time). If I turn it off, the problem described below goes
away.
Essentially, I get SSL_ERROR_SSL back from an SSL_read() call which should
have successfully finished the negotiation and returned 0 (because the
client sends me one request and never generates more payload, while
the server responds then closes the connection).
The pattern is like this:
1) I have data to write, and the SSL session's descriptor
selects as ready-to-write.
2) I call SSL_renegotiate. I do understand that in a server
application this merely sends the client a request to
do a new handshake, which the client can ignore.
3) I generate more data and several more SSL_writes() complete
normally.
4) Eventualy the SSL session's file descriptor selects as
ready-to-read.
5) I call SSL_read with a 4096-byte buffer. SSL_read returns
-1 and error is SSL_ERROR_WANT_READ.
6) I set a flag to ensure I do not call SSL_write() (it isn't
clear to me this is necessary -- the documentation is vague)
and select on the SSL session's descriptor for read.
7) The SSL session's file descriptor selects as ready for read,
I call SSL with the same 4096 byte buffer at the same address,
and SSL_read returns -1 and error is SSL_ERROR_SSL.
I cannot understand why #7 occurs. Is SSL_MODE_ENABLE_PARTIAL_WRITE just
incompatible with non-blocking mode and renegotiations?
Thor
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