Ip ssh server algorithm encryption aes256-ctr With the following config only aes256-ctr with hmac-sha1 is allowed on the router: In security-audits, all CBC-ciphers are often a problem.īy default there are many algorithms supported:Įncryption Algorithms:aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc If the IOS-device is running at least 15.5(2), then it's possible to disable unwanted algorithms. This won't really increase the security of the setup, but it gives less log-entries from bots that try to login to SSH with commonly used username/password-combinations. In some setups, where SSH has to be reachable over the internet, I also change the SSH-port to something non-standard. The last step is to restrict the vty-lines to only use SSH, so that Telnet is not allowed any more: And if your IOS is to old, this command will also not be available.ĭepending on your needs you could enable the logging of SSH-login-events: You should change to a more powerful terminal like SecureCRT or use only a size of 2048 Bit which is still very secure. If you are using Putty in the actual version (0.63 at the time of writing), this is more then Putty can handle. For my setups (with MacOS and Linux clients) I configure a bitlength of 4096 Bit. By default this is done with 768 Bit, which is not state-of-the-art any more. When the SSH-session is established, the session-keys are computed with the Diffie-Hellmann key exchange protocol. The RSA-Keypair is assigned to the SSH-config: And it typically doesn't hurt to have better crypto then the others.Ĭrypto key generate rsa label SSH-KEY modulus 4096 But by far not that slow that it's unusable. Thats more then recommended on sites like and makes the session-setup a little slower. The default-keylength ist typically too small, it's time to move to a stronger crypto. In this command we use a dedicated label "SSH-KEY" which we later assign to the SSH-config. It always starts with the generation of a public/private keypair that will be only used for the SSH-process. The client-side part of this document can also be used for checking the settings on a Linux-system. This document shows how to set up SSH on IOS and ASA for advanced session-security and how to configure an Apple Mac with OS X to only negotiate secure crypto. But many of them propose settings that are not adequate any more. In the Quick Connect prompt, enter the Hostname and Username settings for your server, and click Connect.There are countless recommendations for the configuration of SSH on Cisco devices available. Log on to the server by using Quick Connect. If the right passphrase is entered, the server ought to authorize the log-on because (1) it knows that the public-key is allowed access by being listed in the ~/.ssh/authorized_keys file, and (2) that the client SecureCRT program knew the private key. This time when logging on to the server, instead of prompting for the UNIX password, SecureCRT will prompt for the passphrase used to encrypt the private key of the key-pair. Test to see that key-pair authentication is working. Test logging on to the server from the client bash-4.2$ echo (then click on Edit ⟶ Paste) >authorized_keys ![]() Perform the following typed-in commands into the Window: Once the initial login is complete, the next step is to copy the public-key, from the clipboard, into a file call ~/.ssh/authorized_keys.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |