I'm integrating Bitvise client into my winform app. I am using Bitvise SSH Client command line (stnlc.exe in the app's directory) to do so. My app needs to have multiple connections at the same time. It works well with some addresses, but some other it doesn't. This is the command that I'm using:
"C:\Program Files (x86)\Bitvise SSH Client\stnlc.exe" -profile="C:\Users\AutoOffer\AutoOffer\bin\Debug\data\sshprofile.bscp" -host=<myhost> -port=22 -user=<username> -pw=<password> -ka=y -proxyFwding=y -proxyListIntf=127.0.0.1 -proxyListPort=<port>
And this is the error I got:
Bitvise SSH Client 6.45 - stnlc - free for individual use only, see EULA
Copyright (C) 2000-2015 by Bitvise Limited.
Connecting to SSH2 server XX.XX.XX.XX:22.
Connection established.
Server version: SSH-2.0-dropbear_0.46
First key exchange started.
ERROR: The SSH2 session has terminated with error.
Reason: Error class: LocalSshDisconn, code: KeyExchangeFailed, message: FlowSshTransport: no mutually supported key exchange algorithm.
Local list: "ecdh-sha2-1.3.132.0.10,ecdh-sha2-nistp521,ecdh-sha2-nistp384,ecdh-sha2-nistp256,diffie-hellman-group14-sha1".
Remote list: "diffie-hellman-group1-sha1".
I tried to connect manually by the Bitvise app with GUI and it successfully connected!
I also updated my bitvise version to the latest (6.45).
Local list: "ecdh-sha2-1.3.132.0.10,ecdh-sha2-nistp521,ecdh-sha2-nistp384,ecdh-sha2-nistp256,diffie-hellman-group14-sha1".
Remote list: "diffie-hellman-group1-sha1".
So it looks like the remote side just supports diffie-hellman-group1-sha1, which is not supported on your side.
On Bitvise SSH Server Version History I read:
The 1024-bit fixed prime Diffie Hellman key exchange methods, diffie-hellman-group1-sha1 and gssapi-group1-sha1 with Kerberos 5, are now disabled by default, due to doubts about continuing security of Diffie Hellman with a 1024-bit fixed prime. Compatibility with most older clients should be retained via the diffie-hellman-group14-sha1 method, which uses a 2048-bit fixed prime. We recommend migrating older SSH clients to new versions supporting ECDH and ECDSA.
So it looks like you have to modify the settings and allow 1024-bit fixed prime Diffie Hellman key exchange methods. Otherwise you will not be able to connect. As explained it is of course better to change the ssh server settings.