Using Putty to SSH ignoring all warnings in Perl

Question

I'm writing a Perl script to SSH into remote linux and maci machines from a windows. For that I'm running plink (putty link) command using qx. The problem is that when I try to run the plink command it gives a prompt

The server's host key is not cached in the registry. You have no guarantee that the server is the computer you think it is. ...... If you do not trust this host, press Return to abandon the connection. Store key in cache? (y/n)

I have to automate the process of running a command remotely. So, I somehow want to bypass this warning.

I could think of two ways of doing this but don't know how to accomplish these

Somehow bypass this warning from putty itself through some command line options or other commands
Some Perl way of passing input to plink when prompted

Can anyone suggest how to do this either in one of above ways or some other solutions.

Do you connect to arbitrary hosts? If not, you can just say "yes" manually once and it will be saved. — melpomene, Jul 01 '19 at 05:29
Yes, the hosts are machines on a network and they are arbitrary not one or two — him, Jul 01 '19 at 05:31
Can you use a non-plink solution, e.g. [Net::SSH2](https://metacpan.org/pod/Net::SSH2) or [Net::SSH::Perl](https://metacpan.org/pod/Net::SSH::Perl)? — melpomene, Jul 01 '19 at 05:36
The problem is I neither do I have these modules in my system nor I can install them. Also, when I use `ssh` (instead of `plink`) it also prompts for a password — him, Jul 01 '19 at 05:38
I'm using Perl from some network location and don't have permissions to install modules there — him, Jul 01 '19 at 05:40
I'd expect `Expect` to help with this ... (in case the hack you found ever fails you) — zdim, Jul 01 '19 at 06:14
See also [VBA Excel code using echo y with PLink](https://stackoverflow.com/q/32335508/850848). — Martin Prikryl, Jul 01 '19 at 06:36
"_if we can use Expect on window_" -- good point. These days [we can](https://stackoverflow.com/a/47940226/4653379) (with Cygwin though) — zdim, Jul 01 '19 at 07:10

score 1 · Answer 1 · answered Jul 01 '19 at 05:59

1

I solved it using pipes to pass Y to plink when prompted - echo Y | plink -ssh <user>@<host> -pw <password> <command>.

For more details refer to this answer. Also note the answer by @clay where he says

For internal servers, the blind echo y | ... trick is probably adequate (and super simple). However, for external servers accessed over the internet, it is much more secure to accept the server host key once rather than blindly accepting every time.

This was the case with me - I was using plink to ssh to internal servers.

answered Jul 01 '19 at 05:59

him

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So please do not post duplicate answers. Close your question as a duplicate. – Martin Prikryl Jul 01 '19 at 06:35
Well this is a workaround I found for my problem. But as I said there might be more Perl(ish) way of doing this thing which I don't know. Using `Expect` is one such way as suggested by @zdim - but I thought it was not compatible with windows. – him Jul 01 '19 at 07:42
Well, the more Perlish way is to use a native Perl implementation of SSH, not Plink. – Martin Prikryl Jul 01 '19 at 07:53

Using Putty to SSH ignoring all warnings in Perl

1 Answers1