upstream: As defined in the RFC, the SSH protocol has negotiable

compression support (which is requested as the name "zlib"). Compression
starts very early in the session. Relative early in OpenSSH lifetime, privsep
was added to sshd, and this required a shared-memory hack so the two
processes could see what was going on in the dataflow.  This shared-memory
hack was soon recognized as a tremendous complexity risk, because it put libz
(which very much trusts it's memory) in a dangerous place, and a new option
("zlib@openssh.com") was added begins compression after authentication (aka
delayed-compression).  That change also permitted removal of the
shared-memory hack. Despite removal from the server, the old "zlib" support
remained in the client, to allow negotiation with non-OpenSSH daemons which
lack the delayed-compression option. This commit deletes support for the
older "zlib" option in the client. It reduces our featureset in a small way,
and encourages other servers to move to a better design. The SSH protocol is
different enough that compressed-key-material attacks like BEAST are
unlikely, but who wants to take the chance? We encourage other ssh servers
who care about optional compression support to add delayed-zlib support.
(Some already do "zlib@openssh.com") ok djm markus

OpenBSD-Commit-ID: 6df986f38e4ab389f795a6e39e7c6857a763ba72

diff --git a/cipher.c b/cipher.c
index 9c2fbd6cfc3d9d5a0b20fc3de998923dcc23afad..7d6e7d8c65ea3e3c391b42ef7f66843ad5e18bba 100644 (file)
--- a/cipher.c
+++ b/cipher.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: cipher.c,v 1.122 2024/08/14 15:42:18 tobias Exp $ */
+/* $OpenBSD: cipher.c,v 1.123 2024/08/23 04:51:00 deraadt Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -143,8 +143,8 @@ const char *
 compression_alg_list(int compression)
 {
 #ifdef WITH_ZLIB
-       return compression ? "zlib@openssh.com,zlib,none" :
-           "none,zlib@openssh.com,zlib";
+       return compression ? "zlib@openssh.com,none" :
+           "none,zlib@openssh.com";
 #else
        return "none";
 #endif

diff --git a/kex.c b/kex.c
index 63aae5d71eeed24863895f5dd813342fca53674c..6b957e5e18f57281fc7caf461589db5f7bb69a60 100644 (file)
--- a/kex.c
+++ b/kex.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kex.c,v 1.186 2024/05/17 00:30:23 djm Exp $ */
+/* $OpenBSD: kex.c,v 1.187 2024/08/23 04:51:00 deraadt Exp $ */
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  *
@@ -842,8 +842,6 @@ choose_comp(struct sshcomp *comp, char *client, char *server)
 #ifdef WITH_ZLIB
        if (strcmp(name, "zlib@openssh.com") == 0) {
                comp->type = COMP_DELAYED;
-       } else if (strcmp(name, "zlib") == 0) {
-               comp->type = COMP_ZLIB;
        } else
 #endif /* WITH_ZLIB */
        if (strcmp(name, "none") == 0) {

diff --git a/kex.h b/kex.h
index 4b3ece669dacc1533cd578d2f9c33623a5514ba7..6700302137ff474ab15f992b0ce5af0da119df1f 100644 (file)
--- a/kex.h
+++ b/kex.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: kex.h,v 1.124 2024/08/22 23:11:30 djm Exp $ */
+/* $OpenBSD: kex.h,v 1.125 2024/08/23 04:51:00 deraadt Exp $ */
 
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
@@ -66,8 +66,6 @@
 #define        KEX_SNTRUP761X25519_SHA512_OLD  "sntrup761x25519-sha512@openssh.com"
 
 #define COMP_NONE      0
-/* pre-auth compression (COMP_ZLIB) is only supported in the client */
-#define COMP_ZLIB      1
 #define COMP_DELAYED   2
 
 #define CURVE25519_SIZE 32

diff --git a/packet.c b/packet.c
index e6ae2013b2bfb30674aa0b5708bb5c514fd92293..486f8515746eb97324cd607326580c53fda6d1cf 100644 (file)
--- a/packet.c
+++ b/packet.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: packet.c,v 1.316 2024/08/15 00:51:51 djm Exp $ */
+/* $OpenBSD: packet.c,v 1.317 2024/08/23 04:51:00 deraadt Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1015,9 +1015,8 @@ ssh_set_newkeys(struct ssh *ssh, int mode)
        /* explicit_bzero(enc->iv,  enc->block_size);
           explicit_bzero(enc->key, enc->key_len);
           explicit_bzero(mac->key, mac->key_len); */
-       if ((comp->type == COMP_ZLIB ||
-           (comp->type == COMP_DELAYED &&
-           state->after_authentication)) && comp->enabled == 0) {
+       if (((comp->type == COMP_DELAYED && state->after_authentication)) &&
+           comp->enabled == 0) {
                if ((r = ssh_packet_init_compression(ssh)) < 0)
                        return r;
                if (mode == MODE_OUT) {

diff --git a/readconf.c b/readconf.c
index 4e3791cb7cc608c00bda39fe737d7891751e302d..1d0ba0e723ae639295ffdc4b10f0e957efd9c843 100644 (file)
--- a/readconf.c
+++ b/readconf.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: readconf.c,v 1.387 2024/05/17 02:39:11 jsg Exp $ */
+/* $OpenBSD: readconf.c,v 1.388 2024/08/23 04:51:00 deraadt Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1002,7 +1002,7 @@ static const struct multistate multistate_pubkey_auth[] = {
 };
 static const struct multistate multistate_compression[] = {
 #ifdef WITH_ZLIB
-       { "yes",                        COMP_ZLIB },
+       { "yes",                        COMP_DELAYED },
 #endif
        { "no",                         COMP_NONE },
        { NULL, -1 }