Deprecated SSH algorithms in ePMP series and PTP550 stations

[aka (Andrii)]

To improve ePMP security Cambium Networks is planning to deprecate legacy SSH algorithms usage for ePMP and PTP550 product lines in the upcoming software releases.

The following key exchange, host-key, message authentication code, and encryption algorithms are deprecated starting with firmware version 4.7.0 and 5.2.0 but still enabled:

• ssh-rsa – key algorithm to remove
• diffie-hellman-group14-sha1 – kex algorithm to remove
• hmac-sha1 – mac algorithm to remove

Starting with firmware version 4.8.0 and 5.3.0 deprecated algorithm support will be turned off by default.

Outdated SSH clients might lack the support of modern algorithms and be unable to establish an SSH connection to ePMP devices with disabled support of deprecated algorithms.

Ubuntu 12.04 with default OpenSSH client and MikroTik RouterOS 6.48.3 will be unable to establish an SSH connection to an ePMP radio.

To provide network administrators options for a smooth migration and to minimize service outages there will be an option to enable deprecated algorithms support.

Via GUI
System → General → Deprecated SSH Algorithms.

Via CLI

ePMP3000>config set cambiumSSHServerDeprecatedAlgorithms 1

(1 – enabled, 0 – disabled)

Via SNMP:

cambiumSSHServerDeprecatedAlgorithms    OBJECT-TYPE
        SYNTAX     Integer32 (0|1)
        MAX-ACCESS read-write
        STATUS     current
        DESCRIPTION
                "Cambium SSH Server: support deprecated algorithms
                    0 - Disable
                    1 - Enable
                Device Allocation: AP, SM"

Via CnMaestro template:

{
    "device_props": {
        "cambiumSSHServerDeprecatedAlgorithms": "1"
    }
}

In SW 4.7.0 and 5.2.0 old algorithms support option is enabled by default. In next releases it will bedisabled by default.

Here is the full list of algorithms present in 4.6.1:

Algorithm	Notes
key exchange algorithms
curve25519-sha256	available since OpenSSH 7.4, Dropbear SSH 2018.76
curve25519-sha256@libssh.org	available since OpenSSH 6.5, Dropbear SSH 2013.62
diffie-hellman-group14-sha256	available since OpenSSH 7.3, Dropbear SSH 2016.73
diffie-hellman-group14-sha1	using weak hashing algorithm, available since OpenSSH 3.9, Dropbear SSH 0.53
kexguess2@matt.ucc.asn.au	available since Dropbear SSH 2013.57
host-key algorithms
ssh-rsa (2048-bit)	using weak hashing algorithm, available since OpenSSH 2.5.0, Dropbear SSH 0.28, a future deprecation notice has been issued in OpenSSH 8.2: https://www.openssh.com/txt/release-8.2
encryption algorithms (ciphers)
aes128-ctr	available since OpenSSH 3.7, Dropbear SSH 0.52
aes256-ctr	available since OpenSSH 3.7, Dropbear SSH 0.52
message authentication code (MAC) algorithms
hmac-sha1	using encrypt-and-MAC mode, using weak hashing algorithm, available since OpenSSH 2.1.0, Dropbear SSH 0.28
hmac-sha2-256	using encrypt-and-MAC mode, available since OpenSSH 5.9, Dropbear SSH 2013.56

The list of algorithms in 4.7.0 with old algorithms support disabled:

Algorithm	Notes
key exchange algorithms
curve25519-sha256	available since OpenSSH 7.4, Dropbear SSH 2018.76
curve25519-sha256@libssh.org	available since OpenSSH 6.5, Dropbear SSH 2013.62
diffie-hellman-group14-sha256	available since OpenSSH 7.3, Dropbear SSH 2016.73
kexguess2@matt.ucc.asn.au	available since Dropbear SSH 2013.57
host-key algorithms
ssh-ed25519	available since OpenSSH 6.5
rsa-sha2-256 (2048-bit)	available since OpenSSH 7.2
encryption algorithms (ciphers)
aes128-ctr	available since OpenSSH 3.7, Dropbear SSH 0.52
aes256-ctr	available since OpenSSH 3.7, Dropbear SSH 0.52
message authentication code (MAC) algorithms
hmac-sha2-256	using encrypt-and-MAC mode, available since OpenSSH 5.9, Dropbear SSH 2013.56

[Majk]

Thank you, but still waiting for 4.7 release…

[aka (Andrii)]

You are welcome, @Majk!
This note means 4.7 beta is very close! New features and improvements take time.