upstream commit

Remove support for pre-authentication compression. Doing
compression early in the protocol probably seemed reasonable in the 1990s,
but today it's clearly a bad idea in terms of both cryptography (cf. multiple
compression oracle attacks in TLS) and attack surface.

Moreover, to support it across privilege-separation zlib needed
the assistance of a complex shared-memory manager that made the
required attack surface considerably larger.

Prompted by Guido Vranken pointing out a compiler-elided security
check in the shared memory manager found by Stack
(http://css.csail.mit.edu/stack/); ok deraadt@ markus@

NB. pre-auth authentication has been disabled by default in sshd
for >10 years.

Upstream-ID: 32af9771788d45a0779693b41d06ec199d849caf

1 files changed, 1 insertions, 47 deletions

diff --git a/monitor.c b/monitor.c
index bea8d8b27..43f484709 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: monitor.c,v 1.165 2016/09/05 13:57:31 djm Exp $ */
+/* $OpenBSD: monitor.c,v 1.166 2016/09/28 16:33:06 djm Exp $ */
 /*
  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
  * Copyright 2002 Markus Friedl <markus@openbsd.org>
@@ -94,7 +94,6 @@
 #include "misc.h"
 #include "servconf.h"
 #include "monitor.h"
-#include "monitor_mm.h"
 #ifdef GSSAPI
 #include "ssh-gss.h"
 #endif
@@ -411,31 +410,6 @@ monitor_child_postauth(struct monitor *pmonitor)
                 monitor_read(pmonitor, mon_dispatch, NULL);
 }
 
-void
-monitor_sync(struct monitor *pmonitor)
-{
-        if (options.compression) {
-                /* The member allocation is not visible, so sync it */
-                mm_share_sync(&pmonitor->m_zlib, &pmonitor->m_zback);
-        }
-}
-
-/* Allocation functions for zlib */
-static void *
-mm_zalloc(struct mm_master *mm, u_int ncount, u_int size)
-{
-        if (size == 0 || ncount == 0 || ncount > SIZE_MAX / size)
-                fatal("%s: mm_zalloc(%u, %u)", __func__, ncount, size);
-
-        return mm_malloc(mm, size * ncount);
-}
-
-static void
-mm_zfree(struct mm_master *mm, void *address)
-{
-        mm_free(mm, address);
-}
-
 static int
 monitor_read_log(struct monitor *pmonitor)
 {
@@ -1632,13 +1606,6 @@ monitor_apply_keystate(struct monitor *pmonitor)
                 kex->host_key_index=&get_hostkey_index;
                 kex->sign = sshd_hostkey_sign;
         }
-
-        /* Update with new address */
-        if (options.compression) {
-                ssh_packet_set_compress_hooks(ssh, pmonitor->m_zlib,
-                    (ssh_packet_comp_alloc_func *)mm_zalloc,
-                    (ssh_packet_comp_free_func *)mm_zfree);
-        }
 }
 
 /* This function requries careful sanity checking */
@@ -1691,24 +1658,11 @@ monitor_openfds(struct monitor *mon, int do_logfds)
 struct monitor *
 monitor_init(void)
 {
-        struct ssh *ssh = active_state;                 /* XXX */
         struct monitor *mon;
 
         mon = xcalloc(1, sizeof(*mon));
-
         monitor_openfds(mon, 1);
 
-        /* Used to share zlib space across processes */
-        if (options.compression) {
-                mon->m_zback = mm_create(NULL, MM_MEMSIZE);
-                mon->m_zlib = mm_create(mon->m_zback, 20 * MM_MEMSIZE);
-
-                /* Compression needs to share state across borders */
-                ssh_packet_set_compress_hooks(ssh, mon->m_zlib,
-                    (ssh_packet_comp_alloc_func *)mm_zalloc,
-                    (ssh_packet_comp_free_func *)mm_zfree);
-        }
-
         return mon;
 }