remote execution server
The rexecd command is the server for the
The server provides remote execution facilities
with authentication based on user names and encrypted passwords.
All diagnostic messages are returned on the connection
associated with the stderr,
after which any network connections are closed.
An error is indicated by a leading byte with a value of 1;
the value 0 is returned in step 7 below 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).
No password file entry for the user name existed.
The wrong password was supplied.
No remote directory.
The chdir command to the home directory failed.
A fork by the server failed.
The user's login shell could not be started.
rexecd is invoked automatically as needed by
and then executes the following protocol:
The server reads characters from the socket up
to a null (\0) byte.
The resultant string is interpreted as an
number, base 10.
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.
A null terminated user name of at most 16 characters
is retrieved on the initial socket.
A null terminated, encrypted, password of at most
16 characters is retrieved on the initial socket.
A null 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.
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.
A null byte is returned on the connection associated
with the stderr and the command line is passed to the
normal login shell of the user.
The shell inherits the network connections established by
Login incorrect as opposed to
is a security breach which allows people to probe a system for users
with null passwords.
A facility to allow all data exchanges
to be encrypted should be present.
© 2004 The SCO Group, Inc. All rights reserved.
UnixWare 7 Release 7.1.4 - 25 April 2004