SSL: explicit session id length checking.

Session ids are not expected to be longer than 32 bytes, but this is
theoretically possible with TLSv1.3, where session ids are essentially
arbitrary and sent as session tickets.  Since on 64-bit platforms we
use fixed 32-byte buffer for session ids, added an explicit length check
to make sure the buffer is large enough.

1 files changed, 8 insertions, 2 deletions

diff --git a/src/event/ngx_event_openssl.c b/src/event/ngx_event_openssl.c
index e2b0b3a26..c6d9af4cd 100644
--- a/src/event/ngx_event_openssl.c
+++ b/src/event/ngx_event_openssl.c
@@ -3848,6 +3848,14 @@ ngx_ssl_new_session(ngx_ssl_conn_t *ssl_conn, ngx_ssl_session_t *sess)
     p = buf;
     i2d_SSL_SESSION(sess, &p);
 
+    session_id = (u_char *) SSL_SESSION_get_id(sess, &session_id_length);
+
+    /* do not cache sessions with too long session id */
+
+    if (session_id_length > 32) {
+        return 0;
+    }
+
     c = ngx_ssl_get_connection(ssl_conn);
 
     ssl_ctx = c->ssl->session_ctx;
@@ -3892,8 +3900,6 @@ ngx_ssl_new_session(ngx_ssl_conn_t *ssl_conn, ngx_ssl_session_t *sess)
         }
     }
 
-    session_id = (u_char *) SSL_SESSION_get_id(sess, &session_id_length);
-
 #if (NGX_PTR_SIZE == 8)
 
     id = sess_id->sess_id;