You can check what's available on your version using: In 2020, this is still pretty lame, but keep reading! Cisco has been adding newer ciphers and removing some deprecated ciphers in newer IOS versions. LhjQ1mlYp3qf0Jt7eoaWNPRV/i0VUaRfxNBefiNBI5pS8ybj3bhfWpZe8QOOMAHRahAPPI9PasOBuMHR Zs+P3WKgP8rh2z7ObTT917pp1VXw4pUkeqCCtMEmkiICO0TzU1dXyuoEPNGeES8wxYOSdaMA0DGE元4pĬcb6hb1RQbHjSjQZfDOXaZ0UwXtVJ07v7PR7fOhFHem58w2P+qmCwnEYFZrZhizR1y1SUDxs6Z7vZV98ĬyoTo98dWG4WDGiHM1loLq3SA3OMfceq5g2waPVBNmpZlzXitCTern1bZ15zdLvhxY1589A/TaSZuMeP NFsKga4tvvikXqKuwe3tfWKzNfO4LY1mZE9FXecoNW0Kb8p4U/pO/w69oEbHmmH7BfgWSHCCVZlgBhcfĭtJa+oVnqHrMwVza+ViTMQLghvt63zewvTN2I235K6W+GhgUm圆p+Q62Rsrfrc+4K5ECVKNf7fzmlg6X MwhL0Qow4OGrd52EkRNRxAc2TYpBr5p0ICdaxeHd7etzgXjkwcZpQ1e2kqvV9XU94LBO1R93AgYYLCsT IbO8KM7kSVdwy7anUhmgiX5jGmpecTFoP+txdA+KuEszAL5x8aeNZsPAykqBU6JClIz3fnMKjgoIqFlZ Ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAACAQC5KQxmPn8tyfK+9fq6NC75whEQD02POopz9SE/SKeP IOS Keys in SECSH format(ssh-rsa, base64 encoded): SSH-KEYS Minimum expected Diffie Hellman key size : 2048 bits !set minimum bit size for client connection Ip ssh rsa keypair-name SSH-KEYS !associate keys to SSH !Note that generating 4096 bit keys can take up to 3 minutes. You should also perform the following to harden SSHĬrypto key generate rsa modulus 4096 label SSH-KEYS No ip ssh server algorithm mac hmac-sha1-96 Ip ssh server algorithm encryption aes256-ctr aes128-ctr These are "Cipher Block Chain" algorithms and will cause a failure during a penetration test.įrom global configuration mode enter the following: We want to disable v1 and remove the cbc and 3Des ciphers. The "version 1.99" means that it supports SSH v1 and v2. GfxKBtvGd30Y2jzYYMmTQGP9u1VrKdQRKAU13/c+iOiQPi3Q4w= M+/Xke7IRMvxg2OEk333uHlKD+Ww6w8D2eMOzY7/R6edHA4UtKXwohJN1OZKS1ltL4tDSZSIeLO3juOL Ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAAAgQCjsPhP/zpPgra0d3wzzt8fDZnKL4sUtCh0DVmV0fH6 IOS Keys in SECSH format(ssh-rsa, base64 encoded): TP-self-signed-1676064512 Minimum expected Diffie Hellman key size : 1024 bits Hostkey Algorithms:x509v3-ssh-rsa,ssh-rsaĮncryption Algorithms: aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes192-cbccĪuthentication timeout: 120 secs Authentication retries: 3 Version 15.2(4)E8 - Mainstream deployment (MD) from 1įirst, let's look at the default SSH setupĪuthentication methods:publickey,keyboard-interactive,passwordĪuthentication Publickey Algorithms:x509v3-ssh-rsa,ssh-rsa Ssh -G OpenSSH site has a page dedicated to legacy ciphersĪll of the commands shown are from a 2960x running: You can use the "-G" switch and SSH will show you the ciphers that SSH is offering: Ssh -oKexAlgorithms=+diffie-hellman-group1-sha1 10.20.1.7 If you will only log into this device once or twice you can use the following without modifying the SSH config file: I had to add HostKeyAlgorithms=+ssh-dss to connect. On a really old switch, I ran into a host key exchange algorithm that I had never even heard of "ssh-dss". KexAlgorithms +diffie-hellman-group1-sha1 Open the SSH config file - gedit ~/.ssh/configĢ. Their offer: diffie-hellman-group1-sha1ġ. Ssh to negotiate with 10.20.1.7 port 22: no matching key exchange method found. You may run into situations on MAC/Linux where the weak ciphers are used and OpenSSH won't connect. MAC/Linux users will be using OpenSSh which also supports SSH V2. You should set Putty to default to SSH V2: Most Windows users connect with Putty which supports SSH v2. Network device manufacturers (all of them I think) enabling SSH v1 by default really bothers me. I plan to do another blog on IOS-XE and Nexus in the future. Microsoft has set July 2020 to remove TLS 1.0/1.1 from IE, Edge Legacy, and Edge Chromium. Firefox had actually done it in May 2020 but so many US Government sites quit working (during the Covid19 Hysteria) that they rolled back. For the security of your network and to pass a penetration test you need to disable the weak ciphers, disable SSH v1 and disable TLS version 1.0 and 1.1.įirefox, Chrome and Microsoft all have committed to dropping support for TLS1.1. For backward compatibility, most companies still ship deprecated, weak SSH, and SSL ciphers.
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