From: "Peter Müller" <peter.mueller@ipfire.org>
To: "IPFire: Development" <development@lists.ipfire.org>
Subject: [PATCH 1/3] OpenSSH: Prefer AES-GCM ciphers over AES-CTR
Date: Sun, 28 Sep 2025 21:05:00 +0000 [thread overview]
Message-ID: <5d3b4fdd-fe49-4997-b00c-c2fd723f0e4a@ipfire.org> (raw)
This reflects the following change made upstream in OpenSSH 9.9:
* ssh(1): prefer AES-GCM to AES-CTR mode when selecting a cipher
for the connection. The default cipher preference list is now
Chacha20/Poly1305, AES-GCM (128/256) followed by AES-CTR
(128/192/256).
However, we keep preferring AES-GCM over Chacha/Poly, as hardware
acceleration often grants the former a better performance, while there
is no security advance of Chacha/Poly usage over 256 bit AES-GCM.
Signed-off-by: Peter Müller <peter.mueller@ipfire.org>
---
config/ssh/ssh_config | 2 +-
config/ssh/sshd_config | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/config/ssh/ssh_config b/config/ssh/ssh_config
index d5f63f315..a248001ff 100644
--- a/config/ssh/ssh_config
+++ b/config/ssh/ssh_config
@@ -10,7 +10,7 @@ Host *
# Only use secure crypto algorithms
KexAlgorithms sntrup761x25519-sha512,sntrup761x25519-sha512@openssh.com,mlkem768x25519-sha256,curve25519-sha256,curve25519-sha256@libssh.org,diffie-hellman-group-exchange-sha256
- Ciphers aes256-gcm@openssh.com,aes256-ctr,chacha20-poly1305@openssh.com,aes192-ctr,aes128-gcm@openssh.com,aes128-ctr
+ Ciphers aes256-gcm@openssh.com,aes128-gcm@openssh.com,chacha20-poly1305@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr
MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,umac-128@openssh.com
# Always visualise server host keys (helps to identify key based MITM attacks)
diff --git a/config/ssh/sshd_config b/config/ssh/sshd_config
index 7b687457c..25e5b1838 100644
--- a/config/ssh/sshd_config
+++ b/config/ssh/sshd_config
@@ -21,7 +21,7 @@ MaxStartups 5
# Only allow safe crypto algorithms
KexAlgorithms sntrup761x25519-sha512,sntrup761x25519-sha512@openssh.com,mlkem768x25519-sha256,curve25519-sha256,curve25519-sha256@libssh.org,diffie-hellman-group-exchange-sha256
-Ciphers aes256-gcm@openssh.com,aes256-ctr,chacha20-poly1305@openssh.com,aes192-ctr,aes128-gcm@openssh.com,aes128-ctr
+Ciphers aes256-gcm@openssh.com,aes128-gcm@openssh.com,chacha20-poly1305@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr
MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,umac-128@openssh.com
# Only allow cryptographically safe SSH host keys (adjust paths if needed)
--
2.51.0
next reply other threads:[~2025-09-28 21:05 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-28 21:05 Peter Müller [this message]
2025-09-28 21:06 ` [PATCH 2/3] OpenSSH: Amend upstream default cipher changes Peter Müller
2025-09-28 21:06 ` [PATCH 3/3] ssh_config: Fix indentation mangled by Vim Peter Müller
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