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| 2005-04-14 | 2005-04-26 | ||
| no summary (64.122.232.104) | Verifying the Host Key (martin) | ||
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| ==== Using Pageant for Authentication ==== | ==== Using Pageant for Authentication ==== | ||
| Read [[&pageanthelp|Putty documentation]]. It mostly applies to WinSCP. | Read [[&pageanthelp|Putty documentation]]. It mostly applies to WinSCP. | ||
| + | |||
| + | ===== Verifying the Host Key ===== | ||
| + | If you are using WinSCP to connect to a server for the first time, you will probably see a message looking something like this: | ||
| + | |||
| + | The server's host key was not found it the cache. You have no guarantee that the | ||
| + | server is the computer you think it is. The server's key fingerprint is: | ||
| + | ssh-rsa 1024 94:3c:9e:2b:23:df:bd:53:b4:ad:f1:5f:4e:2f:9d:ba | ||
| + | |||
| + | This is a feature of the SSH protocol. It is designed to protect you against a network attack known as spoofing: secretly redirecting your connection to a different computer, so that you send your password to the wrong machine. Using this technique, an attacker would be able to learn the password that guards your login account, and could then log in as if they were you and use the account for their own purposes. | ||
| + | |||
| + | To prevent this attack, each server has a unique identifying code, called a host key. These keys are created in a way that prevents one server from forging another server's key. So if you connect to a server and it sends you a different host key from the one you were expecting, WinSCP can warn you that the server may have been switched and that a spoofing attack might be in progress. | ||
| + | |||
| + | WinSCP records the host key for each server you connect to, in the [[config|configuration storage]]. Every time you connect to a server, it checks that the host key presented by the server is the same host key as it was the last time you connected. If it is not, you will see a warning, and you will have the chance to abandon your connection before you type any private information (such as a password) into it. | ||
| + | |||
| + | However, when you connect to a server you have not connected to before, WinSCP has no way of telling whether the host key is the right one or not. So it gives the warning shown above, and asks you whether you want to trust this host key or not. | ||
| + | |||
| + | Whether or not to trust the host key is your choice. If you are connecting within a company network, you might feel that all the network users are on the same side and spoofing attacks are unlikely, so you might choose to trust the key without checking it. If you are connecting across a hostile network (such as the Internet), you should check with your system administrator, perhaps by telephone or in person. (Some modern servers have more than one host key. If the system administrator sends you more than one fingerprint, you should make sure the one WinSCP shows you is on the list, but it doesn't matter which one it is.) ((&puttydoccite)) | ||
| ===== Encryption in SSH ===== | ===== Encryption in SSH ===== | ||