Always ensure that init_msg is initialised for a CCS

We read it later in grow_init_buf(). If CCS is the first thing received in
a flight, then it will use the init_msg from the last flight we received. If
the init_buf has been grown in the meantime then it will point to some
arbitrary other memory location. This is likely to result in grow_init_buf()
attempting to grow to some excessively large amount which is likely to
fail. In practice this should never happen because the only time we receive
a CCS as the first thing in a flight is in an abbreviated handshake. None
of the preceding messages from the server flight would be large enough to
trigger this.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(cherry picked from commit c437757466e7bef632b26eaaf429a9e693330999)

1 files changed, 1 insertions, 0 deletions

diff --git a/ssl/statem/statem_lib.c b/ssl/statem/statem_lib.c
index 31a84e4428..637c610ac3 100644
--- a/ssl/statem/statem_lib.c
+++ b/ssl/statem/statem_lib.c
@@ -370,6 +370,7 @@ int tls_get_message_header(SSL *s, int *mt)
                 }
                 s->s3->tmp.message_type = *mt = SSL3_MT_CHANGE_CIPHER_SPEC;
                 s->init_num = i - 1;
+                s->init_msg = s->init_buf->data;
                 s->s3->tmp.message_size = i;
                 return 1;
             } else if (recvd_type != SSL3_RT_HANDSHAKE) {