NAME

     rexecd — remote execution server

SYNOPSIS

     rexecd

DESCRIPTION

     Rexecd is the server for the rexec(3) routine.  The server provides remote execution
     facilities with authentication based on user names and passwords.

     Rexecd listens for service requests at the port indicated in the ``exec'' service
     specification; see services(5).  When a service request is received the following protocol
     is initiated:

     1.   The server reads characters from the socket up to a NUL (‘\0’) byte.  The resultant
          string is interpreted as an ASCII number, base 10.

     2.   If the number received in step 1 is non-zero, it is interpreted as the port number of a
          secondary stream to be used for the stderr.  A second connection is then created to the
          specified port on the client's machine.

     3.   A NUL terminated user name of at most 16 characters is retrieved on the initial socket.

     4.   A NUL terminated, unencrypted password of at most 16 characters is retrieved on the
          initial socket.

     5.   A NUL terminated command to be passed to a shell is retrieved on the initial socket.
          The length of the command is limited by the upper bound on the size of the system's
          argument list.

     6.   Rexecd then validates the user as is done at login time and, if the authentication was
          successful, changes to the user's home directory, and establishes the user and group
          protections of the user.  If any of these steps fail the connection is aborted with a
          diagnostic message returned.

     7.   A NUL byte is returned on the initial socket and the command line is passed to the
          normal login shell of the user.  The shell inherits the network connections established
          by rexecd.

DIAGNOSTICS

     Except for the last one listed below, all diagnostic messages are returned on the initial
     socket, after which any network connections are closed.  An error is indicated by a leading
     byte with a value of 1 (0 is returned in step 7 above upon successful completion of all the
     steps prior to the command execution).

     username too long
             The name is longer than 16 characters.

     password too long
             The password is longer than 16 characters.

     command too long
             The command line passed exceeds the size of the argument list (as configured into
             the system).

     Login incorrect.
             No password file entry for the user name existed or the wrong password was supplied.

     No remote directory.
             The chdir command to the home directory failed.

     Try again.
             A fork by the server failed.

     <shellname>: ...
             The user's login shell could not be started.  This message is returned on the
             connection associated with the stderr, and is not preceded by a flag byte.

SEE ALSO

     rexec(3)

BUGS

     A facility to allow all data and password exchanges to be encrypted should be present.

HISTORY

     The rexecd command appeared in 4.2BSD.