Connection to Azure SFTP doesnt work using JSCH

Brandl, Fabian 21

Hello everyone,

we are currently working with a cloud product that uses JSCH internally to connect to external sftp sources. Im investigating an connection reset exception that we are getting when trying to connect to azure sftp.

Using wireshark i determined that the problem occurs after jsch initializes the client: key exchange. Establishing the same connection with filezilla we dont have this issue.
comparing the packages from jsch and filezilla i didn't see an obivious issues, jsch has azure supported algorithms in the key exchange request at least it looks like it to me but im not an expert on the ssh protocol. Im gonna post both requests below if somebody could give me any pointers it would be greatly appreciated.

jsch request that leads to azure closing the connection:

filezilla request that works:

jsch log output:

INFO: Connecting to ***** port 22  
INFO: Connection established  
INFO: Remote version string: SSH-2.0-AzureSSH_1.0.0  
INFO: Local version string: SSH-2.0-JSCH-0.1.54  
INFO: CheckCiphers: aes256-ctr,aes192-ctr,aes128-ctr,aes256-cbc,aes192-cbc,aes128-cbc,3des-ctr,arcfour,arcfour128,arcfour256  
INFO: CheckKexes: diffie-hellman-group14-sha1,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521  
INFO: CheckSignatures: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521  
INFO: SSH_MSG_KEXINIT sent  
INFO: Disconnecting from **** port 22  
com.jcraft.jsch.JSchException: Session.connect: java.net.SocketException: Connection reset

Accepted answer

Sumarigo-MSFT 43,801 Reputation points Microsoft Employee

2022-01-30T10:28:10.563+00:00

@Brandl, Fabian Firstly, apologies for the delay in responding here and any inconvenience this issue may have caused.

I see you have posted the similar thread in SO forum, Please refer to the suggestions mentioned over-there and let me know if the issue still persist. I would like to work closer on this issue

Looking forward for your reply!

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1 person found this answer helpful.
Brandl, Fabian 21 Reputation points

2022-01-30T11:37:11.957+00:00

Hi,

I tried jameses suggestion modifying the jsch config but got the same result. (i modified my stackoverflow post in the past to reflect that). It would help to get logs from the sftp server side. But i didnt see a posibility to get the logs from azure.

Regards
Fabian

Sumarigo-MSFT 43,801 Reputation points Microsoft Employee

2022-02-03T06:53:18.177+00:00

@Brandl, Fabian Apologies for the delay response! This is a known issue and product team has informed that it will be fixed before GA. Azure SFTP - Approaching GA, please fill up the form here
(Get the latest updates on Azure products and features to meet your cloud investment needs. Subscribe to notifications to stay informed.)

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Brandl, Fabian 21 Reputation points

2022-02-03T08:12:00.133+00:00

@Sumarigo-MSFT Hi, thanks for the update! Out of curiosity could you share some technical insight whats causing the issue at the moment?

Ankit Khandelwal 1 Reputation point

2022-07-06T06:13:55.287+00:00

Hii @Sumarigo-MSFT ,
Is this issue has been fixed . If fixed can we have its release notes.
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5 additional answers

Juncheng Zhou 6 Reputation points

2022-04-15T01:55:42.703+00:00

Actually, SAP is using JSCH as sftp provider, and my customers cannot use it to connect to Azure SFTP. Any progress or update here?
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1 person found this answer helpful.
Brandl, Fabian 21 Reputation points

2022-04-19T06:30:16.963+00:00

Hi, im assuming you are using SAP CPI? I already proposed this fix to SAP and they modified their JSCH Version, sadly i couldn't get a concrete timeframe when we can expect the fix to be published.
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