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

13 files changed, 18 insertions, 598 deletions

diff --git a/Makefile.in b/Makefile.in
index d6df2ff3c..3990f5525 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -104,7 +104,7 @@ SSHDOBJS=sshd.o auth-rhosts.o auth-passwd.o \
         auth2-chall.o groupaccess.o \
         auth-skey.o auth-bsdauth.o auth2-hostbased.o auth2-kbdint.o \
         auth2-none.o auth2-passwd.o auth2-pubkey.o \
-        monitor_mm.o monitor.o monitor_wrap.o auth-krb5.o \
+        monitor.o monitor_wrap.o auth-krb5.o \
         auth2-gss.o gss-serv.o gss-serv-krb5.o \
         loginrec.o auth-pam.o auth-shadow.o auth-sia.o md5crypt.o \
         sftp-server.o sftp-common.o \
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;
 }
 
diff --git a/monitor.h b/monitor.h
index 93b8b66dd..d68f67458 100644
--- a/monitor.h
+++ b/monitor.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: monitor.h,v 1.19 2015/01/19 19:52:16 markus Exp $ */
+/* $OpenBSD: monitor.h,v 1.20 2016/09/28 16:33:07 djm Exp $ */
 
 /*
  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
@@ -67,21 +67,17 @@ enum monitor_reqtype {
 
 };
 
-struct mm_master;
 struct monitor {
         int                      m_recvfd;
         int                      m_sendfd;
         int                      m_log_recvfd;
         int                      m_log_sendfd;
-        struct mm_master        *m_zback;
-        struct mm_master        *m_zlib;
         struct kex              **m_pkex;
         pid_t                    m_pid;
 };
 
 struct monitor *monitor_init(void);
 void monitor_reinit(struct monitor *);
-void monitor_sync(struct monitor *);
 
 struct Authctxt;
 void monitor_child_preauth(struct Authctxt *, struct monitor *);
diff --git a/monitor_mm.c b/monitor_mm.c
deleted file mode 100644
index aa47b2ed5..000000000
--- a/monitor_mm.c
+++ /dev/null
@@ -1,357 +0,0 @@
-/* $OpenBSD: monitor_mm.c,v 1.21 2015/02/06 23:21:59 millert Exp $ */
-/*
- * Copyright 2002 Niels Provos <provos@citi.umich.edu>
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
- * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
- * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
- * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
- * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#include "includes.h"
-
-#include <sys/types.h>
-#ifdef HAVE_SYS_MMAN_H
-#include <sys/mman.h>
-#endif
-#include "openbsd-compat/sys-tree.h"
-
-#include <errno.h>
-#include <stdarg.h>
-#include <stddef.h>
-#ifdef HAVE_STDINT_H
-#include <stdint.h>
-#endif
-#include <stdlib.h>
-#include <string.h>
-
-#include "xmalloc.h"
-#include "ssh.h"
-#include "log.h"
-#include "monitor_mm.h"
-
-static int
-mm_compare(struct mm_share *a, struct mm_share *b)
-{
-        ptrdiff_t diff = (char *)a->address - (char *)b->address;
-
-        if (diff == 0)
-                return (0);
-        else if (diff < 0)
-                return (-1);
-        else
-                return (1);
-}
-
-RB_GENERATE(mmtree, mm_share, next, mm_compare)
-
-static struct mm_share *
-mm_make_entry(struct mm_master *mm, struct mmtree *head,
-    void *address, size_t size)
-{
-        struct mm_share *tmp, *tmp2;
-
-        if (mm->mmalloc == NULL)
-                tmp = xcalloc(1, sizeof(struct mm_share));
-        else
-                tmp = mm_xmalloc(mm->mmalloc, sizeof(struct mm_share));
-        tmp->address = address;
-        tmp->size = size;
-
-        tmp2 = RB_INSERT(mmtree, head, tmp);
-        if (tmp2 != NULL)
-                fatal("mm_make_entry(%p): double address %p->%p(%zu)",
-                    mm, tmp2, address, size);
-
-        return (tmp);
-}
-
-/* Creates a shared memory area of a certain size */
-
-struct mm_master *
-mm_create(struct mm_master *mmalloc, size_t size)
-{
-        void *address;
-        struct mm_master *mm;
-
-        if (mmalloc == NULL)
-                mm = xcalloc(1, sizeof(struct mm_master));
-        else
-                mm = mm_xmalloc(mmalloc, sizeof(struct mm_master));
-
-        /*
-         * If the memory map has a mm_master it can be completely
-         * shared including authentication between the child
-         * and the client.
-         */
-        mm->mmalloc = mmalloc;
-
-        address = xmmap(size);
-        if (address == (void *)MAP_FAILED)
-                fatal("mmap(%zu): %s", size, strerror(errno));
-
-        mm->address = address;
-        mm->size = size;
-
-        RB_INIT(&mm->rb_free);
-        RB_INIT(&mm->rb_allocated);
-
-        mm_make_entry(mm, &mm->rb_free, address, size);
-
-        return (mm);
-}
-
-/* Frees either the allocated or the free list */
-
-static void
-mm_freelist(struct mm_master *mmalloc, struct mmtree *head)
-{
-        struct mm_share *mms, *next;
-
-        for (mms = RB_ROOT(head); mms; mms = next) {
-                next = RB_NEXT(mmtree, head, mms);
-                RB_REMOVE(mmtree, head, mms);
-                if (mmalloc == NULL)
-                        free(mms);
-                else
-                        mm_free(mmalloc, mms);
-        }
-}
-
-/* Destroys a memory mapped area */
-
-void
-mm_destroy(struct mm_master *mm)
-{
-        mm_freelist(mm->mmalloc, &mm->rb_free);
-        mm_freelist(mm->mmalloc, &mm->rb_allocated);
-
-#ifdef HAVE_MMAP
-        if (munmap(mm->address, mm->size) == -1)
-                fatal("munmap(%p, %zu): %s", mm->address, mm->size,
-                    strerror(errno));
-#else
-        fatal("%s: UsePrivilegeSeparation=yes and Compression=yes not supported",
-            __func__);
-#endif
-        if (mm->mmalloc == NULL)
-                free(mm);
-        else
-                mm_free(mm->mmalloc, mm);
-}
-
-void *
-mm_xmalloc(struct mm_master *mm, size_t size)
-{
-        void *address;
-
-        address = mm_malloc(mm, size);
-        if (address == NULL)
-                fatal("%s: mm_malloc(%zu)", __func__, size);
-        memset(address, 0, size);
-        return (address);
-}
-
-
-/* Allocates data from a memory mapped area */
-
-void *
-mm_malloc(struct mm_master *mm, size_t size)
-{
-        struct mm_share *mms, *tmp;
-
-        if (size == 0)
-                fatal("mm_malloc: try to allocate 0 space");
-        if (size > SIZE_MAX - MM_MINSIZE + 1)
-                fatal("mm_malloc: size too big");
-
-        size = ((size + (MM_MINSIZE - 1)) / MM_MINSIZE) * MM_MINSIZE;
-
-        RB_FOREACH(mms, mmtree, &mm->rb_free) {
-                if (mms->size >= size)
-                        break;
-        }
-
-        if (mms == NULL)
-                return (NULL);
-
-        /* Debug */
-        memset(mms->address, 0xd0, size);
-
-        tmp = mm_make_entry(mm, &mm->rb_allocated, mms->address, size);
-
-        /* Does not change order in RB tree */
-        mms->size -= size;
-        mms->address = (char *)mms->address + size;
-
-        if (mms->size == 0) {
-                RB_REMOVE(mmtree, &mm->rb_free, mms);
-                if (mm->mmalloc == NULL)
-                        free(mms);
-                else
-                        mm_free(mm->mmalloc, mms);
-        }
-
-        return (tmp->address);
-}
-
-/* Frees memory in a memory mapped area */
-
-void
-mm_free(struct mm_master *mm, void *address)
-{
-        struct mm_share *mms, *prev, tmp;
-
-        tmp.address = address;
-        mms = RB_FIND(mmtree, &mm->rb_allocated, &tmp);
-        if (mms == NULL)
-                fatal("mm_free(%p): can not find %p", mm, address);
-
-        /* Debug */
-        memset(mms->address, 0xd0, mms->size);
-
-        /* Remove from allocated list and insert in free list */
-        RB_REMOVE(mmtree, &mm->rb_allocated, mms);
-        if (RB_INSERT(mmtree, &mm->rb_free, mms) != NULL)
-                fatal("mm_free(%p): double address %p", mm, address);
-
-        /* Find previous entry */
-        prev = mms;
-        if (RB_LEFT(prev, next)) {
-                prev = RB_LEFT(prev, next);
-                while (RB_RIGHT(prev, next))
-                        prev = RB_RIGHT(prev, next);
-        } else {
-                if (RB_PARENT(prev, next) &&
-                    (prev == RB_RIGHT(RB_PARENT(prev, next), next)))
-                        prev = RB_PARENT(prev, next);
-                else {
-                        while (RB_PARENT(prev, next) &&
-                            (prev == RB_LEFT(RB_PARENT(prev, next), next)))
-                                prev = RB_PARENT(prev, next);
-                        prev = RB_PARENT(prev, next);
-                }
-        }
-
-        /* Check if range does not overlap */
-        if (prev != NULL && MM_ADDRESS_END(prev) > address)
-                fatal("mm_free: memory corruption: %p(%zu) > %p",
-                    prev->address, prev->size, address);
-
-        /* See if we can merge backwards */
-        if (prev != NULL && MM_ADDRESS_END(prev) == address) {
-                prev->size += mms->size;
-                RB_REMOVE(mmtree, &mm->rb_free, mms);
-                if (mm->mmalloc == NULL)
-                        free(mms);
-                else
-                        mm_free(mm->mmalloc, mms);
-        } else
-                prev = mms;
-
-        if (prev == NULL)
-                return;
-
-        /* Check if we can merge forwards */
-        mms = RB_NEXT(mmtree, &mm->rb_free, prev);
-        if (mms == NULL)
-                return;
-
-        if (MM_ADDRESS_END(prev) > mms->address)
-                fatal("mm_free: memory corruption: %p < %p(%zu)",
-                    mms->address, prev->address, prev->size);
-        if (MM_ADDRESS_END(prev) != mms->address)
-                return;
-
-        prev->size += mms->size;
-        RB_REMOVE(mmtree, &mm->rb_free, mms);
-
-        if (mm->mmalloc == NULL)
-                free(mms);
-        else
-                mm_free(mm->mmalloc, mms);
-}
-
-static void
-mm_sync_list(struct mmtree *oldtree, struct mmtree *newtree,
-    struct mm_master *mm, struct mm_master *mmold)
-{
-        struct mm_master *mmalloc = mm->mmalloc;
-        struct mm_share *mms, *new;
-
-        /* Sync free list */
-        RB_FOREACH(mms, mmtree, oldtree) {
-                /* Check the values */
-                mm_memvalid(mmold, mms, sizeof(struct mm_share));
-                mm_memvalid(mm, mms->address, mms->size);
-
-                new = mm_xmalloc(mmalloc, sizeof(struct mm_share));
-                memcpy(new, mms, sizeof(struct mm_share));
-                RB_INSERT(mmtree, newtree, new);
-        }
-}
-
-void
-mm_share_sync(struct mm_master **pmm, struct mm_master **pmmalloc)
-{
-        struct mm_master *mm;
-        struct mm_master *mmalloc;
-        struct mm_master *mmold;
-        struct mmtree rb_free, rb_allocated;
-
-        debug3("%s: Share sync", __func__);
-
-        mm = *pmm;
-        mmold = mm->mmalloc;
-        mm_memvalid(mmold, mm, sizeof(*mm));
-
-        mmalloc = mm_create(NULL, mm->size);
-        mm = mm_xmalloc(mmalloc, sizeof(struct mm_master));
-        memcpy(mm, *pmm, sizeof(struct mm_master));
-        mm->mmalloc = mmalloc;
-
-        rb_free = mm->rb_free;
-        rb_allocated = mm->rb_allocated;
-
-        RB_INIT(&mm->rb_free);
-        RB_INIT(&mm->rb_allocated);
-
-        mm_sync_list(&rb_free, &mm->rb_free, mm, mmold);
-        mm_sync_list(&rb_allocated, &mm->rb_allocated, mm, mmold);
-
-        mm_destroy(mmold);
-
-        *pmm = mm;
-        *pmmalloc = mmalloc;
-
-        debug3("%s: Share sync end", __func__);
-}
-
-void
-mm_memvalid(struct mm_master *mm, void *address, size_t size)
-{
-        void *end = (char *)address + size;
-
-        if (address < mm->address)
-                fatal("mm_memvalid: address too small: %p", address);
-        if (end < address)
-                fatal("mm_memvalid: end < address: %p < %p", end, address);
-        if (end > MM_ADDRESS_END(mm))
-                fatal("mm_memvalid: address too large: %p", address);
-}
diff --git a/monitor_mm.h b/monitor_mm.h
deleted file mode 100644
index f1fae7e3b..000000000
--- a/monitor_mm.h
+++ /dev/null
@@ -1,62 +0,0 @@
-/* $OpenBSD: monitor_mm.h,v 1.6 2014/01/04 17:50:55 tedu Exp $ */
-
-/*
- * Copyright 2002 Niels Provos <provos@citi.umich.edu>
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
- * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
- * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
- * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
- * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#ifndef _MM_H_
-#define _MM_H_
-
-struct mm_share {
-        RB_ENTRY(mm_share) next;
-        void *address;
-        size_t size;
-};
-
-struct mm_master {
-        RB_HEAD(mmtree, mm_share) rb_free;
-        struct mmtree rb_allocated;
-        void *address;
-        size_t size;
-
-        struct mm_master *mmalloc;      /* Used to completely share */
-};
-
-RB_PROTOTYPE(mmtree, mm_share, next, mm_compare)
-
-#define MM_MINSIZE              128
-
-#define MM_ADDRESS_END(x)       (void *)((char *)(x)->address + (x)->size)
-
-struct mm_master *mm_create(struct mm_master *, size_t);
-void mm_destroy(struct mm_master *);
-
-void mm_share_sync(struct mm_master **, struct mm_master **);
-
-void *mm_malloc(struct mm_master *, size_t);
-void *mm_xmalloc(struct mm_master *, size_t);
-void mm_free(struct mm_master *, void *);
-
-void mm_memvalid(struct mm_master *, void *, size_t);
-#endif /* _MM_H_ */
diff --git a/monitor_wrap.h b/monitor_wrap.h
index 1bc76afff..db5902f55 100644
--- a/monitor_wrap.h
+++ b/monitor_wrap.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: monitor_wrap.h,v 1.31 2016/08/13 17:47:41 markus Exp $ */
+/* $OpenBSD: monitor_wrap.h,v 1.32 2016/09/28 16:33:07 djm Exp $ */
 
 /*
  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
@@ -95,7 +95,4 @@ int mm_bsdauth_respond(void *, u_int, char **);
 int mm_skey_query(void *, char **, char **, u_int *, char ***, u_int **);
 int mm_skey_respond(void *, u_int, char **);
 
-/* zlib allocation hooks */
-void mm_init_compression(struct mm_master *);
-
 #endif /* _MM_WRAP_H_ */
diff --git a/myproposal.h b/myproposal.h
index 4729b30b0..072e36ec7 100644
--- a/myproposal.h
+++ b/myproposal.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: myproposal.h,v 1.53 2016/09/22 17:52:53 djm Exp $ */
+/* $OpenBSD: myproposal.h,v 1.54 2016/09/28 16:33:07 djm Exp $ */
 
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
@@ -167,7 +167,7 @@
 
 #endif /* WITH_OPENSSL */
 
-#define KEX_DEFAULT_COMP        "none,zlib@openssh.com,zlib"
+#define KEX_DEFAULT_COMP        "none,zlib@openssh.com"
 #define KEX_DEFAULT_LANG        ""
 
 #define KEX_CLIENT \
diff --git a/opacket.h b/opacket.h
index 16322ec6f..d2a63a355 100644
--- a/opacket.h
+++ b/opacket.h
@@ -133,9 +133,6 @@ void	packet_disconnect(const char *, ...)
         ssh_packet_get_input(active_state)
 #define packet_get_output() \
         ssh_packet_get_output(active_state)
-#define packet_set_compress_hooks(ctx, allocfunc, freefunc) \
-        ssh_packet_set_compress_hooks(active_state, ctx, \
-            allocfunc, freefunc);
 #define packet_check_eom() \
         ssh_packet_check_eom(active_state)
 #define set_newkeys(mode) \
diff --git a/packet.c b/packet.c
index fb316acbc..002e8d49a 100644
--- a/packet.c
+++ b/packet.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: packet.c,v 1.238 2016/09/19 19:02:19 markus Exp $ */
+/* $OpenBSD: packet.c,v 1.239 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
@@ -756,86 +756,6 @@ uncompress_buffer(struct ssh *ssh, struct sshbuf *in, struct sshbuf *out)
         /* NOTREACHED */
 }
 
-/* Serialise compression state into a blob for privsep */
-static int
-ssh_packet_get_compress_state(struct sshbuf *m, struct ssh *ssh)
-{
-        struct session_state *state = ssh->state;
-        struct sshbuf *b;
-        int r;
-
-        if ((b = sshbuf_new()) == NULL)
-                return SSH_ERR_ALLOC_FAIL;
-        if (state->compression_in_started) {
-                if ((r = sshbuf_put_string(b, &state->compression_in_stream,
-                    sizeof(state->compression_in_stream))) != 0)
-                        goto out;
-        } else if ((r = sshbuf_put_string(b, NULL, 0)) != 0)
-                goto out;
-        if (state->compression_out_started) {
-                if ((r = sshbuf_put_string(b, &state->compression_out_stream,
-                    sizeof(state->compression_out_stream))) != 0)
-                        goto out;
-        } else if ((r = sshbuf_put_string(b, NULL, 0)) != 0)
-                goto out;
-        r = sshbuf_put_stringb(m, b);
- out:
-        sshbuf_free(b);
-        return r;
-}
-
-/* Deserialise compression state from a blob for privsep */
-static int
-ssh_packet_set_compress_state(struct ssh *ssh, struct sshbuf *m)
-{
-        struct session_state *state = ssh->state;
-        struct sshbuf *b = NULL;
-        int r;
-        const u_char *inblob, *outblob;
-        size_t inl, outl;
-
-        if ((r = sshbuf_froms(m, &b)) != 0)
-                goto out;
-        if ((r = sshbuf_get_string_direct(b, &inblob, &inl)) != 0 ||
-            (r = sshbuf_get_string_direct(b, &outblob, &outl)) != 0)
-                goto out;
-        if (inl == 0)
-                state->compression_in_started = 0;
-        else if (inl != sizeof(state->compression_in_stream)) {
-                r = SSH_ERR_INTERNAL_ERROR;
-                goto out;
-        } else {
-                state->compression_in_started = 1;
-                memcpy(&state->compression_in_stream, inblob, inl);
-        }
-        if (outl == 0)
-                state->compression_out_started = 0;
-        else if (outl != sizeof(state->compression_out_stream)) {
-                r = SSH_ERR_INTERNAL_ERROR;
-                goto out;
-        } else {
-                state->compression_out_started = 1;
-                memcpy(&state->compression_out_stream, outblob, outl);
-        }
-        r = 0;
- out:
-        sshbuf_free(b);
-        return r;
-}
-
-void
-ssh_packet_set_compress_hooks(struct ssh *ssh, void *ctx,
-    void *(*allocfunc)(void *, u_int, u_int),
-    void (*freefunc)(void *, void *))
-{
-        ssh->state->compression_out_stream.zalloc = (alloc_func)allocfunc;
-        ssh->state->compression_out_stream.zfree = (free_func)freefunc;
-        ssh->state->compression_out_stream.opaque = ctx;
-        ssh->state->compression_in_stream.zalloc = (alloc_func)allocfunc;
-        ssh->state->compression_in_stream.zfree = (free_func)freefunc;
-        ssh->state->compression_in_stream.opaque = ctx;
-}
-
 /*
  * Causes any further packets to be encrypted using the given key.  The same
  * key is used for both sending and reception.  However, both directions are
@@ -2450,21 +2370,14 @@ ssh_packet_get_output(struct ssh *ssh)
 static int
 ssh_packet_set_postauth(struct ssh *ssh)
 {
-        struct sshcomp *comp;
-        int r, mode;
+        int r;
 
         debug("%s: called", __func__);
         /* This was set in net child, but is not visible in user child */
         ssh->state->after_authentication = 1;
         ssh->state->rekeying = 0;
-        for (mode = 0; mode < MODE_MAX; mode++) {
-                if (ssh->state->newkeys[mode] == NULL)
-                        continue;
-                comp = &ssh->state->newkeys[mode]->comp;
-                if (comp && comp->enabled &&
-                    (r = ssh_packet_init_compression(ssh)) != 0)
-                        return r;
-        }
+        if ((r = ssh_packet_enable_delayed_compress(ssh)) != 0)
+                return r;
         return 0;
 }
 
@@ -2528,7 +2441,6 @@ newkeys_to_blob(struct sshbuf *m, struct ssh *ssh, int mode)
                         goto out;
         }
         if ((r = sshbuf_put_u32(b, comp->type)) != 0 ||
-            (r = sshbuf_put_u32(b, comp->enabled)) != 0 ||
             (r = sshbuf_put_cstring(b, comp->name)) != 0)
                 goto out;
         r = sshbuf_put_stringb(m, b);
@@ -2589,9 +2501,7 @@ ssh_packet_get_state(struct ssh *ssh, struct sshbuf *m)
                 return r;
         if (cipher_get_keycontext(state->receive_context, p) != (int)rlen)
                 return SSH_ERR_INTERNAL_ERROR;
-
-        if ((r = ssh_packet_get_compress_state(m, ssh)) != 0 ||
-            (r = sshbuf_put_stringb(m, state->input)) != 0 ||
+        if ((r = sshbuf_put_stringb(m, state->input)) != 0 ||
             (r = sshbuf_put_stringb(m, state->output)) != 0)
                 return r;
 
@@ -2645,7 +2555,6 @@ newkeys_from_blob(struct sshbuf *m, struct ssh *ssh, int mode)
                 mac->key_len = maclen;
         }
         if ((r = sshbuf_get_u32(b, &comp->type)) != 0 ||
-            (r = sshbuf_get_u32(b, (u_int *)&comp->enabled)) != 0 ||
             (r = sshbuf_get_cstring(b, &comp->name, NULL)) != 0)
                 goto out;
         if (enc->name == NULL ||
@@ -2773,8 +2682,7 @@ ssh_packet_set_state(struct ssh *ssh, struct sshbuf *m)
         cipher_set_keycontext(state->send_context, keyout);
         cipher_set_keycontext(state->receive_context, keyin);
 
-        if ((r = ssh_packet_set_compress_state(ssh, m)) != 0 ||
-            (r = ssh_packet_set_postauth(ssh)) != 0)
+        if ((r = ssh_packet_set_postauth(ssh)) != 0)
                 return r;
 
         sshbuf_reset(state->input);
diff --git a/packet.h b/packet.h
index 464d83b1a..690f2ec7e 100644
--- a/packet.h
+++ b/packet.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: packet.h,v 1.71 2016/03/07 19:02:43 djm Exp $ */
+/* $OpenBSD: packet.h,v 1.72 2016/09/28 16:33:07 djm Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -120,11 +120,6 @@ void     ssh_packet_send_debug(struct ssh *, const char *fmt, ...) __attribute__
 int      ssh_set_newkeys(struct ssh *, int mode);
 void     ssh_packet_get_bytes(struct ssh *, u_int64_t *, u_int64_t *);
 
-typedef void *(ssh_packet_comp_alloc_func)(void *, u_int, u_int);
-typedef void (ssh_packet_comp_free_func)(void *, void *);
-void     ssh_packet_set_compress_hooks(struct ssh *, void *,
-    ssh_packet_comp_alloc_func *, ssh_packet_comp_free_func *);
-
 int      ssh_packet_write_poll(struct ssh *);
 int      ssh_packet_write_wait(struct ssh *);
 int      ssh_packet_have_data_to_write(struct ssh *);
diff --git a/servconf.c b/servconf.c
index acd903a88..51feb051f 100644
--- a/servconf.c
+++ b/servconf.c
@@ -1,5 +1,5 @@
 
-/* $OpenBSD: servconf.c,v 1.295 2016/08/25 23:57:54 djm Exp $ */
+/* $OpenBSD: servconf.c,v 1.296 2016/09/28 16:33:07 djm Exp $ */
 /*
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
  *                    All rights reserved
@@ -921,7 +921,7 @@ static const struct multistate multistate_permitrootlogin[] = {
 };
 static const struct multistate multistate_compression[] = {
         { "delayed",                    COMP_DELAYED },
-        { "yes",                        COMP_ZLIB },
+        { "yes",                        COMP_DELAYED },
         { "no",                         COMP_NONE },
         { NULL, -1 }
 };
diff --git a/sshconnect2.c b/sshconnect2.c
index 5e7d07dc5..a633e76cb 100644
--- a/sshconnect2.c
+++ b/sshconnect2.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshconnect2.c,v 1.248 2016/09/22 02:29:57 dtucker Exp $ */
+/* $OpenBSD: sshconnect2.c,v 1.249 2016/09/28 16:33:07 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  * Copyright (c) 2008 Damien Miller.  All rights reserved.
@@ -174,7 +174,7 @@ ssh_kex2(char *host, struct sockaddr *hostaddr, u_short port)
             compat_cipher_proposal(options.ciphers);
         myproposal[PROPOSAL_COMP_ALGS_CTOS] =
             myproposal[PROPOSAL_COMP_ALGS_STOC] = options.compression ?
-            "zlib@openssh.com,zlib,none" : "none,zlib@openssh.com,zlib";
+            "zlib@openssh.com,none" : "none,zlib@openssh.com";
         myproposal[PROPOSAL_MAC_ALGS_CTOS] =
             myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
         if (options.hostkeyalgorithms != NULL) {
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)