[HN Gopher] RSA/SHA1 signature type disabled by default in OpenSSH
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       RSA/SHA1 signature type disabled by default in OpenSSH
        
       Author : rodrigo975
       Score  : 48 points
       Date   : 2021-08-31 17:23 UTC (5 hours ago)
        
 (HTM) web link (undeadly.org)
 (TXT) w3m dump (undeadly.org)
        
       | kevinoid wrote:
       | I've been running with ssh-rsa disabled for a while (with a
       | config based on
       | https://infosec.mozilla.org/guidelines/openssh#modern-openss... )
       | and it's been pretty smooth. Support for better algorithms is
       | widespread, with a few exceptions (like bazaar.launchpad.net).
       | 
       | One gotcha: OpenWrt does not enable ECDSA by default[1] and only
       | recently enabled support for ed25519 by default.[2][3] It's
       | available in release candidates for 21.02, but not in current
       | stable releases. So if you're running a stable release you'll
       | need to either add `PubkeyAcceptedKeyTypes +ssh-rsa` to your
       | client ssh_config or use a custom build of OpenWrt with
       | DROPBEAR_ECC or DROPBEAR_ECC_FULL enabled.
       | 
       | [1]: https://bugs.openwrt.org/index.php?do=details&task_id=786
       | 
       | [2]:
       | https://git.openwrt.org/?p=openwrt/openwrt.git;a=commit;h=d0...
       | 
       | [3]:
       | https://bugs.openwrt.org/index.php?do=details&task_id=3216&s...
       | 
       | [4]: https://bugs.openwrt.org/index.php?do=details&task_id=3452
        
         | wahern wrote:
         | OpenSSH that ships with macOS doesn't support ECC keys loaded
         | via PKCS#11, only RSA keys. This is the case even on Big Sur
         | because though it ships OpenSSH 8.1p1 its linked against
         | LibreSSL 2.7.3, which lacks support for delegating non-RSA
         | signing operations. This is annoying if you're using an HSM or
         | secure enclave via PKCS#11; for example the T2, which only
         | supports ECDSA P-256.
         | 
         | There's nothing wrong with RSA keys. What's being disabled is
         | the use of SHA-1 for signature hashing. SHA-2 works just fine
         | and the same RSA keys continue working.
        
           | kevinoid wrote:
           | Agreed. I should have made my post clearer. OpenWrt does not
           | suppport SHA-2 signature hashing or any of the newer key
           | algorithms I mentioned, so you are stuck with RSA+SHA1.
        
       | hannob wrote:
       | Key point to avoid any confusion: This is about the RSA-SHA1
       | cipher combination. It does _not_ mean that RSA is deprecated.
       | 
       | If you use an RSA key for SSH (server or client) you can continue
       | using that.
       | 
       | This should not affect any modern-day SSH implementation, it will
       | only cut off compatibility with SSH implementations not updated
       | for a very long time.
        
         | hotdogs wrote:
         | To tag onto this, modern means OpenSSH 7.2 (released February
         | 2016) or newer. Currently running an enterprise-wide SSH
         | certificate service, and trying to push people along to update
         | their old VMs in preparation for this deprecation.
        
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       (page generated 2021-08-31 23:02 UTC)