MEDIUM: ssl: add a rwlock for SSL server session cache
When adding the server side support for certificate update over the CLI
we encountered a design problem with the SSL session cache which was not
locked.
Indeed, once a certificate is updated we need to flush the cache, but we
also need to ensure that the cache is not used during the update.
To prevent the use of the cache during an update, this patch introduce a
rwlock for the SSL server session cache.
In the SSL session part this patch only lock in read, even if it writes.
The reason behind this, is that in the session part, there is one cache
storage per thread so it is not a problem to write in the cache from
several threads. The problem is only when trying to write in the cache
from the CLI (which could be on any thread) when a session is trying to
access the cache. So there is a write lock in the CLI part to prevent
simultaneous access by a session and the CLI.
This patch also remove the thread_isolate attempt which is eating too
much CPU time and was not protecting from the use of a free ptr in the
session.
diff --git a/src/ssl_ckch.c b/src/ssl_ckch.c
index f9b8f18..f654b4b 100644
--- a/src/ssl_ckch.c
+++ b/src/ssl_ckch.c
@@ -1400,14 +1400,11 @@
/* The bind_conf will be null on server ckch_instances. */
if (ckchi->is_server_instance) {
int i;
-
- /* The certificate update on the server side (backend)
- * can be done by rewriting a single pointer so no
- * locks are needed here. */
+ /* a lock is needed here since we have to free the SSL cache */
+ HA_RWLOCK_WRLOCK(SSL_SERVER_LOCK, &ckchi->server->ssl_ctx.lock);
/* free the server current SSL_CTX */
SSL_CTX_free(ckchi->server->ssl_ctx.ctx);
/* Actual ssl context update */
- thread_isolate();
SSL_CTX_up_ref(ckchi->ctx);
ckchi->server->ssl_ctx.ctx = ckchi->ctx;
ckchi->server->ssl_ctx.inst = ckchi;
@@ -1417,7 +1414,7 @@
free(ckchi->server->ssl_ctx.reused_sess[i].ptr);
ckchi->server->ssl_ctx.reused_sess[i].ptr = NULL;
}
- thread_release();
+ HA_RWLOCK_WRUNLOCK(SSL_SERVER_LOCK, &ckchi->server->ssl_ctx.lock);
} else {
HA_RWLOCK_WRLOCK(SNI_LOCK, &ckchi->bind_conf->sni_lock);