22 rexecd: server for rexec

rexecd is the server for the rexec routine. The server provides remote execution facilities with authentication based on user names and passwords. It passes error messages and notices to the syslog facility ‘LOG_DAEMON’.

rexecd [option]…

rexecd listens for service requests at the port indicated in the ‘exec’ service specification. 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.

• Invoking
• Diagnostics