Fix uninitialized tlsInfo causing random SSL_read/write on plain sockets

TCPSocket's SSL_CTX*-taking constructor - the one every accepted
TCPSession actually goes through (TCPSession(EPoll&, TCPServer*, ...)
passes server->ctx into it) - never initialized the `tlsInfo` member,
and TCPSocket.h gave it no default either. Every session's `tlsInfo`
was uninitialized garbage.

receiveData()/sendData() key their TLS-vs-plain dispatch on
`if(tlsInfo)`. Since that garbage value is non-zero often enough on a
real stack, sessions on a plain, non-TLS server were intermittently
routed through TLS::receiveData()/sendData() (SSL_read()/SSL_write())
against an also-uninitialized SSL*, segfaulting inside libssl. Confirmed
via dmesg: repeated "general protection fault ... in libssl.so.3",
signal 11, non-deterministic timing consistent with depending on
whatever garbage happened to be on the stack for a given session.

Fixed by dispatching on `ctx` instead of `tlsInfo`. `ctx` (TLS.h) now
defaults to NULL (previously also uninitialized) and is the value that
actually gets set for real in TLS::createContext() and correctly
inherited by every session via TLS(SSL_CTX*) - unlike `tlsInfo`, which
is only ever set on the listening TCPServer's own constructor and never
propagated to sessions at all. For the previously-working TLS-enabled
case this is a no-op: ctx and tlsInfo were always both set (or both
unset) together on the listening server, so the observable behavior
there is unchanged - only the previously-undefined session-level
behavior is fixed.

Verified live: restarted the APIServer test instance (a plain, non-TLS
TCPServer - the exact configuration that was crashing), ran 100
sequential requests with no failures, and confirmed no new libssl
segfaults in dmesg since the fix (three separate pre-fix crash
incidents are all still visible in the dmesg history for comparison).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

TCPSocket.cpp

@@ -28,7 +28,16 @@ namespace core {
    }
 
    void TCPSocket::receiveData(coreutils::ZString &buffer) {
-      if(tlsInfo) {
+      // Dispatch on `ctx`, not `tlsInfo` - the SSL_CTX*-taking constructor
+      // (used for every accepted TCPSession) never sets `tlsInfo` at all,
+      // leaving it as uninitialized garbage that intermittently (whenever
+      // that garbage happened to be non-zero) routed a plain, non-TLS
+      // session's data through SSL_read()/SSL_write() against an
+      // uninitialized SSL*, segfaulting inside libssl. `ctx` is the
+      // reliable signal: real and non-NULL for an actual TLS server/
+      // session (set in TLS::createContext(), inherited by sessions via
+      // TLS(SSL_CTX*)), safely NULL by default otherwise (see TLS.h).
+      if(ctx) {
 	 int len = TLS::receiveData(buffer);
 	 if(len >= 0) {
 	    coreutils::ZString zbuffer(buffer.getData(), len);
@@ -40,7 +49,7 @@ namespace core {
    }
 
    int TCPSocket::sendData(const char *data, int length) {
-      if(tlsInfo)
+      if(ctx)
 	return TLS::sendData(data, length);
       else
 	return Socket::sendData(data, length);

TLS.h

@@ -46,7 +46,12 @@ namespace core {
 
       void createContext(TLSInfo *tlsInfo);
 
-      SSL_CTX *ctx;   
+      // A never-configured TLS object (either the listening TCPServer
+      // itself when constructed with tlsInfo=NULL, or a TCPSession spawned
+      // from one via TLS(SSL_CTX*)) must default to a real NULL here, not
+      // garbage - TCPSocket::receiveData()/sendData() key their TLS-vs-
+      // plain dispatch on this exact value (see TCPSocket.cpp).
+      SSL_CTX *ctx = NULL;
       
     protected:
       int receiveData(coreutils::ZString &buffer);