Sun Microsystems Sun Workstation 100U System Manager's Manual page 242

RSlID( 8C)
MAINTENANCE COMr\.fA.NDS
RSHD (8C)
NAME
rshd - remote shell server
SYNOPSIS
/ ete/ln ..... hd host. port
DESCRIPTION
R8hd is the server ror the rcmd(3N) routine and, consequently, ror the r8h(IC) program. The
server provides remote execution racilities with authentication based on privileged port numbers.
R8hd is invoked by inetd(8C) each time a shell service is requested, and executes the following
protocol:
1)
The server checks the client's source port. If the port is not in the range 0-1023, the
server aborts the connection. The clients host address (in hex) and port number (in
decimal) are the argument passed
to
r8hd.
2) The server reads characters rrom the socket up
to
a null ('\0') byte. The resultant string
is interpreted as an ASCII number, base 10.
3) 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 .tderr. A second connection is then created
to
the
specified port on the client's machine. The source port or this second connection is also
in the range 0-1023.
4) The server checks the client's source address. If the address is associated with a host for
which no corresponding entry exists in the host name data base (see h08t8(S)), the server
aborts the connection.
S) A null terminated user name of at most 16 characters is retrieved on the initial socket.
This user name is interpreted as a user identity to use on the .erver's machine.
6) A null terminated user name or at most 16 characters is retrieved on the initial socket.
This user name is interpreted as the user identity on the eHent's machine.
7) A null terminated command
to
be passed to a shell is retrieved on the initial socket. The
length or the command is limited by the upper bound on the size or the system's argu-
ment list.
8) R8hd then validates the user according to the following steps. The remote user name is
looked up in the password file and a chdir is performed to the user's home directory. If
the lookup or fails, the connection is terminated. If the chdir fails, it does a chdir to /
(root). If the user iB not the super-user, (user id 0), the file
I
etcl h08t8.equiv is consulted
ror a list or hosts considered "equivalent". If the client's host name is present in this file,
the authentication is considered successful. If the lookup fails, or the user is the super-
user, then the file .rhosts in the home directory of the remote user is checked for the
machine name and identity or the user on the client's machine. If this lookup fails, the
connection is terminated.
9) A null byte is returned on the connection associated with the .tderr and the command
line is passed to the normal login shell or the user. The shell inherits the network connec-
tions established by r8hd.
DIAGNOSTICS
All diagnostic messages a.re returned on the connection associa.ted with the .tderr, arter which
any network connections are closed. An error is indicated by a leading byte with a value or 1 (0
is returned in step 9 above upon successrul completion
ot
all the steps prior to the command exe-
cution).
"loeu.er too long"
The name
ot
the user on the client's machine is longer than 16 characters.
Sun Releas, 1.1 Last change: 3 January 1984
87