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ssh: Remove AES-CBC ciphers from default server and client lists

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A base system OpenSSH update in 2016 or so removed a number of ciphers
from the default lists offered by the server/client, due to known
weaknesses.  This caused POLA issues for some users and prompted
PR207679; the ciphers were restored to the default lists in r296634.

When upstream removed these ciphers from the default server list, they
moved them to the client-only default list.  They were subsequently
removed from the client default, in OpenSSH 7.9p1.

The change has persisted long enough.  Remove these extra ciphers from
both the server and client default lists, in advance of FreeBSD 13.

Reviewed by:	markm, rgrimes
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D25833
This commit is contained in:
Ed Maste 2020-07-28 00:24:12 +00:00
parent 855e49f3b0
commit 952d18a214
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=363627
3 changed files with 2 additions and 12 deletions
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7
crypto/openssh/FREEBSD-upgrade
View file

@ -168,13 +168,6 @@
ignore HPN-related configuration options to avoid breaking existing
configurations.
9) AES-CBC
The AES-CBC ciphers were removed from the server-side proposal list
in 6.7p1 due to theoretical weaknesses and the availability of
superior ciphers (including AES-CTR and AES-GCM). We have re-added
them for compatibility with third-party clients.
This port was brought to you by (in no particular order) DARPA, NAI

4
crypto/openssh/myproposal.h
View file

@ -1,5 +1,4 @@
/* $OpenBSD: myproposal.h,v 1.57 2018/09/12 01:34:02 djm Exp $ */
/* $FreeBSD$ */
/*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
@ -122,8 +121,7 @@
#define KEX_SERVER_ENCRYPT \
"chacha20-poly1305@openssh.com," \
"aes128-ctr,aes192-ctr,aes256-ctr" \
AESGCM_CIPHER_MODES \
",aes128-cbc,aes192-cbc,aes256-cbc"
AESGCM_CIPHER_MODES
#define KEX_CLIENT_ENCRYPT KEX_SERVER_ENCRYPT

3
crypto/openssh/sshd_config.5
View file

@ -495,8 +495,7 @@ The default is:
.Bd -literal -offset indent
chacha20-poly1305@openssh.com,
aes128-ctr,aes192-ctr,aes256-ctr,
aes128-gcm@openssh.com,aes256-gcm@openssh.com,
aes128-cbc,aes192-cbc,aes256-cbc
aes128-gcm@openssh.com,aes256-gcm@openssh.com
.Ed
.Pp
The list of available ciphers may also be obtained using