sftp does not work if user's associated shell is a restricted shell (rksh)

Issue

• sftp connection closed when user's associated shell is a restricted shell (rksh)

  • Client side:

    luser@server1:$ sftp user1@server2
    Connecting to server2...
    Connection closed
    

• The following logs are recorded at the server side.

  server2 sshd[10569]: Connection from 10.254.218.180 port 58541
  server2 sshd[10569]: Found matching DSA key: 27:06:ac:8b:2d:1b:2d:ba:bc:59:d9:2d:1c:05:ec:db
  server2 sshd[10569]: Accepted publickey for user1 from 10.254.218.180 port 58541 ssh2
  server2 sshd[10569]: pam_unix(sshd:session): session opened for user user1 by (uid=0)
  server2 sshd[10574]: subsystem request for sftp
  server2 sshd[10574]: Connection closed by 10.254.218.180
  server2 sshd[10574]: Closing connection to 10.254.218.180
  server2 sshd[10569]: pam_unix(sshd:session): session closed for user user1