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, 9 deletions

diff --git a/sshd.c b/sshd.c
index 6d182239b..816611c93 100644
--- a/sshd.c
+++ b/sshd.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshd.c,v 1.475 2016/08/28 22:28:12 djm Exp $ */
+/* $OpenBSD: sshd.c,v 1.476 2016/09/28 16:33:07 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -114,7 +114,6 @@
 #include "dispatch.h"
 #include "channels.h"
 #include "session.h"
-#include "monitor_mm.h"
 #include "monitor.h"
 #ifdef GSSAPI
 #include "ssh-gss.h"
@@ -582,9 +581,6 @@ privsep_preauth(Authctxt *authctxt)
                         ssh_sandbox_parent_preauth(box, pid);
                 monitor_child_preauth(authctxt, pmonitor);
 
-                /* Sync memory */
-                monitor_sync(pmonitor);
-
                 /* Wait for the child's exit status */
                 while (waitpid(pid, &status, 0) < 0) {
                         if (errno == EINTR)
@@ -2152,10 +2148,6 @@ do_ssh2_kex(void)
         if (options.compression == COMP_NONE) {
                 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
                     myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
-        } else if (options.compression == COMP_DELAYED) {
-                myproposal[PROPOSAL_COMP_ALGS_CTOS] =
-                    myproposal[PROPOSAL_COMP_ALGS_STOC] =
-                    "none,zlib@openssh.com";
         }
 
         if (options.rekey_limit || options.rekey_interval)