Charybdis currently leaks about 45-50k per configuration parse,
including every rehash. This change plugs these leaks by properly
iterating through all conf_parm_t structures to seek all strings that
should be freed and also by freeing the conf_parm_t structures
themselves.
These leaks have been present since the original rewrite of the
configuration parsing system in ircd-ratbox r11953.
Additionally, this change also cleans up and documents the parsing code
a bit.
SSL_OP_NO_COMPRESSION was presumably added in an attempt to prevent
information leakage in a manner similar to recent attacks on HTTPS.
However, assuming that IRC is vulnerable to the same class of attacks is
incorrect: the behavior of the IRC protocol (a single long-running
connection) is not the same as that of HTTPS (multiple ephemeral
connections). HTTPS's use of ephemeral connections means that certain
assumptions can be made about the contents of the compression
algorithm's dictionaries and the content exchanged between the client
and server (e.g. the content being nearly the same for each connection),
which is not true for IRC. Additionally, they rely on the attacker being
able to coerce the client into creating many HTTPS connections (and
resending some secret token belonging to the user, along with
attacker-controlled data) each time, none of which is possible with IRC.
Lastly, since compression is no longer performed, this option will
result in leaking the lengths of messages transmitted to and from the
client. This option does reduce CPU utilization on Charybdis servers but
also increases bandwidth consumed.
The C standard does not allow constructing pointers beyond one past the end
of an array. Therefore, if size is an unsigned type (size_t), then
buf + size is never less than buf.
Clang on 32-bit took advantage of the undefined behaviour, causing
segfaults.
Lightly tested.
Note that these are not available in old versions of OpenSSL (like FreeBSD
9.x base OpenSSL), so allow them to be missing.
A side effect may be slightly higher CPU consumption and network traffic.
Without a session id context and if client certificates are used, OpenSSL
fails the handshake if an attempt is made to reuse an old session. Various
clients could not reconnect after a disconnection because of this.
See https://bugzilla.mozilla.org/show_bug.cgi?id=858394#c34 for a bug
report.
