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I've found it.</div>
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The server and client has no common mac algorithm. I tried to add 'hmac-sha1-96' to Erlang SSH:</div>
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<span>$ git diff<br>
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<div>diff --git a/lib/ssh/src/ssh_transport.erl b/lib/ssh/src/ssh_transport.erl<br>
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<div>index a85926354e..66d06c3360 100644<br>
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<div>--- a/lib/ssh/src/ssh_transport.erl<br>
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<div>+++ b/lib/ssh/src/ssh_transport.erl<br>
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<div>@@ -171,6 +171,7 @@ supported_algorithms(mac) -><br>
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<div> [{'hmac-sha2-256', [{macs,hmac}, {hashs,sha256}]},<br>
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<div> {'hmac-sha2-512', [{macs,hmac}, {hashs,sha512}]},<br>
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<div> {'hmac-sha1', [{macs,hmac}, {hashs,sha}]},<br>
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<div>+ {'hmac-sha1-96', [{macs,hmac}, {hashs,sha}]},<br>
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<div> {'AEAD_AES_128_GCM', [{ciphers,aes_128_gcm}]},<br>
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<div> {'AEAD_AES_256_GCM', [{ciphers,aes_256_gcm}]}<br>
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<div> ]<br>
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I can't test it because I have no ssh server at hand that has that old mac. But it works with erlang client to erlang server.</div>
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Could you patch your Erlang client, test and tell me it it works?</div>
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/Hans<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>Från:</b> József Bérces <jozsef.berces@ericsson.com><br>
<b>Skickat:</b> den 8 oktober 2019 14:36<br>
<b>Till:</b> Hans Nilsson R <hans.r.nilsson@ericsson.com>; Erlang Questions <erlang-questions@erlang.org><br>
<b>Ämne:</b> RE: ssh:connect "Key exchange failed"</font>
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<p class="x_MsoNormal">Hi Hans,</p>
<p class="x_MsoNormal"> </p>
<p class="x_MsoNormal">I tried it with several OTP releases up to 21. I have not tried OTP 22.</p>
<p class="x_MsoNormal"> </p>
<p class="x_MsoNormal">Here is what I received with telnet:</p>
<p class="x_MsoNormal"> </p>
<p class="x_MsoNormal">QþCb8é¢ê˜x|qâob‚gss-group1-sha1-toWM5Slw5Ew8Mqkay+al2g==,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1ssh-rsa,ssh-dss aes256-cbc,aes192-cbc,aes128-cbc aes256-cbc,aes192-cbc,aes128-cbchmac-sha1-96,hmac-md5-96hmac-sha1-96,hmac-md5-96
none,zlib none,zlib</p>
<p class="x_MsoNormal"> es,i-default</p>
<p class="x_MsoNormal"> es,i-defaultConnection closed by foreign host.</p>
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<p class="x_MsoNormal">And these are the default algorithms:</p>
<p class="x_MsoNormal"> </p>
<p class="x_MsoNormal">[{kex,['ecdh-sha2-nistp384','ecdh-sha2-nistp521',</p>
<p class="x_MsoNormal"> 'ecdh-sha2-nistp256','diffie-hellman-group-exchange-sha256',</p>
<p class="x_MsoNormal"> 'diffie-hellman-group16-sha512',</p>
<p class="x_MsoNormal"> 'diffie-hellman-group18-sha512',</p>
<p class="x_MsoNormal"> 'diffie-hellman-group14-sha256',</p>
<p class="x_MsoNormal"> 'diffie-hellman-group14-sha1',</p>
<p class="x_MsoNormal"> 'diffie-hellman-group-exchange-sha1']},</p>
<p class="x_MsoNormal">{public_key,['ecdsa-sha2-nistp384','ecdsa-sha2-nistp521',</p>
<p class="x_MsoNormal"> 'ecdsa-sha2-nistp256','ssh-rsa','rsa-sha2-256',</p>
<p class="x_MsoNormal"> 'rsa-sha2-512','ssh-dss']},</p>
<p class="x_MsoNormal">{cipher,[{client2server,['aes256-gcm@openssh.com',</p>
<p class="x_MsoNormal"> 'aes256-ctr','aes192-ctr','aes128-gcm@openssh.com',</p>
<p class="x_MsoNormal"> 'aes128-ctr','aes128-cbc','3des-cbc']},</p>
<p class="x_MsoNormal"> {server2client,['aes256-gcm@openssh.com','aes256-ctr',</p>
<p class="x_MsoNormal"> 'aes192-ctr','aes128-gcm@openssh.com','aes128-ctr',</p>
<p class="x_MsoNormal"> 'aes128-cbc','3des-cbc']}]},</p>
<p class="x_MsoNormal">{mac,[{client2server,['hmac-sha2-256','hmac-sha2-512',</p>
<p class="x_MsoNormal"> 'hmac-sha1']},</p>
<p class="x_MsoNormal"> {server2client,['hmac-sha2-256','hmac-sha2-512',</p>
<p class="x_MsoNormal"> 'hmac-sha1']}]},</p>
<p class="x_MsoNormal">{compression,[{client2server,[none,'zlib@openssh.com',zlib]},</p>
<p class="x_MsoNormal"> {server2client,[none,'zlib@openssh.com',zlib]}]}]</p>
<p class="x_MsoNormal"> </p>
<p class="x_MsoNormal">5> ssh_transport:supported_algorithms(mac).</p>
<p class="x_MsoNormal">[{client2server,['hmac-sha2-256','hmac-sha2-512',</p>
<p class="x_MsoNormal"> 'hmac-sha1','AEAD_AES_128_GCM','AEAD_AES_256_GCM']},</p>
<p class="x_MsoNormal">{server2client,['hmac-sha2-256','hmac-sha2-512','hmac-sha1',</p>
<p class="x_MsoNormal"> 'AEAD_AES_128_GCM','AEAD_AES_256_GCM']}]</p>
<p class="x_MsoNormal"> </p>
<p class="x_MsoNormal">Thanks,</p>
<p class="x_MsoNormal">Jozsef</p>
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<p class="x_MsoNormal"><b>From:</b> Hans Nilsson R <hans.r.nilsson@ericsson.com> <br>
<b>Sent:</b> Tuesday, 8 October, 2019 10:47<br>
<b>To:</b> József Bérces <jozsef.berces@ericsson.com>; Erlang Questions <erlang-questions@erlang.org><br>
<b>Subject:</b> Sv: ssh:connect "Key exchange failed"</p>
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<p class="x_MsoNormal"><span style="font-size:10.0pt; font-family:"Courier New"; color:black">The "Key exchange failed" error indicates that there is no agreement in the first phase where different algorithms are negotiated.</span></p>
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<p class="x_MsoNormal"><span style="font-size:10.0pt; font-family:"Courier New"; color:black">A common cause is that there are no common cipher algorithm available. For example the AES-256 CBC is not available in Erlang SSH.</span></p>
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<p class="x_MsoNormal"><span style="font-size:10.0pt; font-family:"Courier New"; color:black">Which otp version do you use?</span></p>
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<p class="x_MsoNormal"><span style="font-size:10.0pt; font-family:"Courier New"; color:black">What does the function ssh:default_algorithms() return?</span></p>
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<p class="x_MsoNormal"><span style="font-size:10.0pt; font-family:"Courier New"; color:black">What algorithms does the server provide? (Check by telnet the server, type "SSH-2.0-xxx" and look at the funny characters that is returned. Or post them here)</span></p>
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<p class="x_MsoNormal"><span style="font-size:10.0pt; font-family:"Courier New"; color:black">/Hans
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<p class="x_MsoNormal"><b><span style="color:black">Från:</span></b><span style="color:black"> erlang-questions-bounces@erlang.org <erlang-questions-bounces@erlang.org> för József Bérces <jozsef.berces@ericsson.com><br>
<b>Skickat:</b> den 8 oktober 2019 09:23<br>
<b>Till:</b> Erlang Questions <erlang-questions@erlang.org><br>
<b>Ämne:</b> [erlang-questions] ssh:connect "Key exchange failed"</span> </p>
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<p class="x_xmsonormal">Hi,</p>
<p class="x_xmsonormal"> </p>
<p class="x_xmsonormal">I need to connect to an ssh server but ssh:connect always returns "Key exchange failed". I can connect with KiTTY, and checking the KiTTY logs I suspect that the problem is the 1024-bit RSA key.
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<p class="x_xmsonormal"> </p>
<p class="x_xmsonormal">Could you please check the KiTTY log below what is not supported by the Erlang SSH client?
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<p class="x_xmsonormal"> </p>
<p class="x_xmsonormal">Is there any way to add the missing support to the Erlang SSH client so that I could connect to this server?</p>
<p class="x_xmsonormal"> </p>
<p class="x_xmsonormal">Thanks,</p>
<p class="x_xmsonormal">Jozsef</p>
<p class="x_xmsonormal"> </p>
<p class="x_xmsonormal">2019-10-07 14:37:58 Starting 42264 from XXXXX@XXXXXX</p>
<p class="x_xmsonormal">2019-10-07 14:38:07 Connecting to 10.XXX.XXX.XXX port 22</p>
<p class="x_xmsonormal">2019-10-07 14:38:07 We claim version: SSH-2.0-PuTTY_KiTTY</p>
<p class="x_xmsonormal">2019-10-07 14:38:07 Server version: SSH-2.0-Sun_SSH_1.1.5</p>
<p class="x_xmsonormal">2019-10-07 14:38:07 Using SSH protocol version 2</p>
<p class="x_xmsonormal">2019-10-07 14:38:08 Doing Diffie-Hellman group exchange</p>
<p class="x_xmsonormal">2019-10-07 14:38:08 Doing Diffie-Hellman key exchange with hash SHA-1</p>
<p class="x_xmsonormal">2019-10-07 14:38:08 Server also has ssh-dss host key, but we don't know it</p>
<p class="x_xmsonormal">2019-10-07 14:38:08 Host key fingerprint is:</p>
<p class="x_xmsonormal">2019-10-07 14:38:08 ssh-rsa 1024 XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX</p>
<p class="x_xmsonormal">2019-10-07 14:38:16 Initialised AES-256 CBC client->server encryption</p>
<p class="x_xmsonormal">2019-10-07 14:38:16 Initialised HMAC-SHA1-96 client->server MAC algorithm</p>
<p class="x_xmsonormal">2019-10-07 14:38:16 Initialised AES-256 CBC server->client encryption</p>
<p class="x_xmsonormal">2019-10-07 14:38:16 Initialised HMAC-SHA1-96 server->client MAC algorithm</p>
<p class="x_xmsonormal">2019-10-07 14:38:22 Using SSPI from SECUR32.DLL</p>
<p class="x_xmsonormal">2019-10-07 14:38:22 Attempting GSSAPI authentication</p>
<p class="x_xmsonormal">2019-10-07 14:38:22 GSSAPI authentication initialisation failed</p>
<p class="x_xmsonormal">2019-10-07 14:38:22 The target was not recognized.</p>
<p class="x_xmsonormal">2019-10-07 14:38:22 Attempting keyboard-interactive authentication</p>
<p class="x_xmsonormal">2019-10-07 14:38:30 Access granted</p>
<p class="x_xmsonormal">2019-10-07 14:38:30 Opening session as main channel</p>
<p class="x_xmsonormal">2019-10-07 14:38:30 Opened main channel</p>
<p class="x_xmsonormal">2019-10-07 14:38:30 Allocated pty (ospeed 38400bps, ispeed 38400bps)</p>
<p class="x_xmsonormal">2019-10-07 14:38:31 Started a shell/command</p>
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