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IBM AIX: Regular users can ssh into AIX but sftp fails

How To


A regular user can ssh into AIX but a sftp request fails for the same user.


How to resolve the problem where incoming sftp requests to AIX by regular users fail with connection closed after entering the  user's password.


AIX version 6.1, 7.1 and 7.2 running IBM OpenSSH


The most common reason for this problem is incorrect permission on the /etc/ssh/sshd_config file.
The /etc/ssh/sshd_config file is configured by default with the following line for sftp service:
Subsystem       sftp    /usr/sbin/sftp-server

OpenSSH on AIX is configured to use sftp-server by default and it requires the permission to be 644 on sshd_config.

The default permission on /etc/ssh/sshd_config is 644 and owned by root system.
Check the permission on sshd_config.
# ls -l /etc/ssh/sshd_config

If the permission on the sshd_config file is not 644 change it to 644. (rw-r--r--).
# chmod 644 /etc/ssh/sshd_config

If your environment requires that permission on sshd_config to be 640 due to security concerns you can use internal-sftp instead of sftp-server. They are virtually the same functionally. SFTP will work with permission 640 on sshd_config if configured to use internal-sftp.

To use internal-sftp change the sftp-server line in sshd_config to the following:
Subsystem       sftp   internal-sftp

Stop and restart sshd afterwards.
# stopsrc -s sshd
# startsrc -s sshd

Additional Information


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Document Information

Modified date:
21 November 2019