Skip to main content

ssh fingerprint authenticity prompt

The authenticity of host can't be established

I faced a weird problem today:

  • A Jenkins post-build job is configured to deploy via scp to a target server
  • Jenkins runs as "integration" user
  • As "integration"  user, I already made sure the server is in "known_hosts", by manually SSH connected to it (when SSH-ing to it, I'm not prompted about the target server's identity anymore)
  • The Jenkins job is still prompted about the target server's identity
What was really weird:
  • From the Jenkins job, the target server's fingerprint is RSA based and is d9:fa:90:e6:2b:d2:f7:92:8b:28:3f:94:1e:bf:1b:fa.
  • From an SSH session, the target server's fingerprint is ECDSA based and is 0d:2a:c3:3b:8f:f1:e9:bc:1f:5d:68:d3:84:6d:71:a8.

This is because

  • The Jenkins SSH plugin I use is not up to date and still use weak and old fashioned algorithms: the negiciation stops at a weak one, DSA.
  • The SSH client (in SSH session) negociation ends up a stronger algorithm, ECDSA.

This is proven by these commands.

To force RSA algorithm:
ssh -o HostKeyAlgorithms=ssh-rsa-cert-v01@openssh.com,\
                         ssh-dss-cert-v01@openssh.com,\
                         ssh-rsa-cert-v00@openssh.com,\
                         ssh-dss-cert-v00@openssh.com,\
                         ssh-rsa,ssh-dss  integration@target-host.rktmb.org

The prompt is:

The authenticity of host 'target-host.rktmb.org (192.168.15.12)' can't be established.
RSA key fingerprint is d9:fa:90:e6:2b:d2:f7:92:8b:28:3f:94:1e:bf:1b:fa.

To let the negociation go on and end up with ECDSA:

ssh integration@target-host.rktmb.org

The prompt is:

The authenticity of host 'target-host.rktmb.org (192.168.15.12)' can't be established.
ECDSA key fingerprint is 0d:2a:c3:3b:8f:f1:e9:bc:1f:5d:68:d3:84:6d:71:a8.



So, in order to add the target host to the "known_hosts", I had to use the command forcing RSA to be used:

ssh -o HostKeyAlgorithms=ssh-rsa-cert-v01@openssh.com,\
                         ssh-dss-cert-v01@openssh.com,\
                         ssh-rsa-cert-v00@openssh.com,\
                         ssh-dss-cert-v00@openssh.com,\
                         ssh-rsa,ssh-dss  integration@target-host.rktmb.org

And then issue the "yes" confirmation.

This way the Jenkins job can smoothly SSH-connect to the target host in order to deploy.

Thanks to http://askubuntu.com/a/217066 and https://blog.cloudflare.com/ecdsa-the-digital-signature-algorithm-of-a-better-internet/

Popular posts from this blog

npm run build base-href

Using NPM to specify base-href When building an Angular application, people usually use "ng" and pass arguments to that invocation. Typically, when wanting to hard code "base-href" in "index.html", one will issue: ng build --base-href='https://ngx.rktmb.org/foo' I used to build my angular apps through Bamboo or Jenkins and they have a "npm" plugin. I got the habit to build the application with "npm run build" before deploying it. But the development team once asked me to set the "--base-href='https://ngx.rktmb.org/foo'" parameter. npm run build --base-href='https://ngx.rktmb.org/foo did not set the base href in indext.html After looking for a while, I found https://github.com/angular/angular-cli/issues/13560 where it says: You need to use −− to pass arguments to npm scripts. This did the job! The command to issue is then: npm run build -- --base-href='https://ngx.rktmb.org/foo...

wget maven ntlm proxy

How to make wget, curl and Maven download behind an NTLM Proxy Working on CentOS, behind an NTLM proxy: yum can deal without problem with a NTLM Proxy wget, curl and Maven cannot The solution is to use " cntlm ". " cntlm " is a NTLM client for proxies requiring NTLM authentication. How it works Install "cntlm" Configure "cntlm"  by giving it your credentials by giving it the NTLM Proxy Start "cntlm" deamon (it listens to "127.0.0.1:3128") Configure wget, curl and Maven to use "cntlm" instead of using directly the NTLM Proxy Note: You will have then a kind of 2 stages Proxy : cntlm + the NTLM proxy Configure CNTLM After installing cntlm, the configuration file is in "cntlm.conf". You must have your domain (in the Windows meaning), proxy login and  proxy password. Mine are respectively: rktmb.org, mihamina, 1234abcd (yes, just for the example) You must have you NTLM Proxy Hostnama or IP ...

Undefined global vim

Defining vim as global outside of Neovim When developing plugins for Neovim, particularly in Lua, developers often encounter the "Undefined global vim" warning. This warning can be a nuisance and disrupt the development workflow. However, there is a straightforward solution to this problem by configuring the Lua Language Server Protocol (LSP) to recognize 'vim' as a global variable. Getting "Undefined global vim" warning when developing Neovim plugin While developing Neovim plugins using Lua, the Lua language server might not recognize the 'vim' namespace by default. This leads to warnings about 'vim' being an undefined global variable. These warnings are not just annoying but can also clutter the development environment with unnecessary alerts, potentially hiding other important warnings or errors. Defining vim as global in Lua LSP configuration to get rid of the warning To resolve the "Undefined global vi...