ext/session_ticket: avoid calling memcpy on overlapping memory areas

In _gnutls_encrypt_session_ticket, ticket.encrypted_state is allocated
from ticket_data->data, thus those memory areas may overlap.  Using
memcpy here leads to undefined behavior.

Spotted by valgrind run on ppc64le.

==95231== Source and destination overlap in memcpy(0x47ce3a2, 0x47ce3a2, 160)
==95231==    at 0x408A840: memcpy (vg_replace_strmem.c:1023)
==95231==    by 0x424EE9F: pack_ticket (session_ticket.c:139)
==95231==    by 0x424FA4F: _gnutls_encrypt_session_ticket (session_ticket.c:335)
==95231==    by 0x4199E3B: generate_session_ticket (session_ticket.c:249)
==95231==    by 0x419A333: _gnutls13_send_session_ticket (session_ticket.c:307)
==95231==    by 0x40F8817: _gnutls13_handshake_server (handshake-tls13.c:511)
==95231==    by 0x4110DEB: handshake_server (handshake.c:3331)
==95231==    by 0x410C70B: gnutls_handshake (handshake.c:2727)
==95231==    by 0x10009EBF: retry_handshake (serv.c:1306)
==95231==    by 0x1000AB67: tcp_server (serv.c:1500)
==95231==    by 0x10009E5B: main (serv.c:1297)
==95231==

Signed-off-by: Daiki Ueno <dueno@redhat.com>

diff --git a/lib/ext/session_ticket.c b/lib/ext/session_ticket.c
index 09e240c2d085ae61ab4dd304d87cea547be5204b..98db39ff889501b2b11c050c013196445e417ce1 100644 (file)
--- a/lib/ext/session_ticket.c
+++ b/lib/ext/session_ticket.c
@@ -136,7 +136,11 @@ pack_ticket(const struct ticket_st *ticket, gnutls_datum_t *ticket_data)
        _gnutls_write_uint16(ticket->encrypted_state_len, p);
        p += 2;
 
-       memcpy(p, ticket->encrypted_state, ticket->encrypted_state_len);
+       /* We use memmove instead of memcpy here because
+        * ticket->encrypted_state is allocated from
+        * ticket_data->data, and thus both memory areas may overlap.
+        */
+       memmove(p, ticket->encrypted_state, ticket->encrypted_state_len);
        p += ticket->encrypted_state_len;
 
        memcpy(p, ticket->mac, TICKET_MAC_SIZE);