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\"     @(#)rcmd.3       8.1 (Berkeley) 6/4/93
\"
Dd March 30, 2005
Dt RCMD 3
Os
Sh NAME
Nm rcmd ,
Nm orcmd ,
Nm rcmd_af ,
Nm orcmd_af ,
Nm rresvport ,
Nm rresvport_af ,
Nm iruserok ,
Nm ruserok ,
Nm iruserok_sa
Nd routines for returning a stream to a remote command
Sh LIBRARY
Lb libc
Sh SYNOPSIS
In unistd.h
Ft int
Fn rcmd "char **ahost" "int inport" "const char *locuser" "const char *remuser" "const char *cmd" "int *fd2p"
Ft int
Fn orcmd "char **ahost" "int inport" "const char *locuser" "const char *remuser" "const char *cmd" "int *fd2p"
Ft int
Fn rcmd_af "char **ahost" "int inport" "const char *locuser" "const char *remuser" "const char *cmd" "int *fd2p" "int af"
Ft int
Fn orcmd_af "char **ahost" "int inport" "const char *locuser" "const char *remuser" "const char *cmd" "int *fd2p" "int af"
Ft int
Fn rresvport "int *port"
Ft int
Fn rresvport_af "int *port" "int family"
Ft int
Fn iruserok "uint32_t raddr" "int superuser" "const char *ruser" "const char *luser"
Ft int
Fn ruserok "const char *rhost" "int superuser" "const char *ruser" "const char *luser"
Ft int
Fn iruserok_sa "const void *raddr" "int rlen" "int superuser" "const char *ruser" "const char *luser"
Sh DESCRIPTION
The
Fn rcmd
function is available for use by anyone to run commands on a
remote system.  It acts like the
Fn orcmd
command, with the exception that it makes a call out to the
Xr rcmd 1
command, or any other user-specified command, to perform the
actual connection (thus not requiring
that the caller be running as the super-user), and is only
available for the
Dq shell/tcp
port.
The
Fn orcmd
function
is used by the super-user to execute a command on
a remote machine using an authentication scheme based
on reserved port numbers.
While
Fn rcmd
and
Fn orcmd
can only handle IPv4 address in the first argument,
Fn rcmd_af
and
Fn orcmd_af
can handle other cases as well.
The
Fn rresvport
function
returns a descriptor to a socket
with an address in the privileged port space.
The
Fn rresvport_af
function is similar to
Fn rresvport ,
but you can explicitly specify the address family to use.
Calling
Fn rresvport_af
with
Dv AF_INET
has the same effect as
Fn rresvport .
The
Fn iruserok
and
Fn ruserok
functions are used by servers
to authenticate clients requesting service with
Fn rcmd .
All six functions are present in the same file and are used
by the
Xr rshd 8
server (among others).
Fn iruserok_sa
is an address family independent variant of
Fn iruserok .
Pp
The
Fn rcmd
function
looks up the host
Fa *ahost
using
Xr gethostbyname 3 ,
returning \-1 if the host does not exist.
Otherwise
Fa *ahost
is set to the standard name of the host
and a connection is established to a server
residing at the well-known Internet port
Fa inport .
Pp
If the connection succeeds,
a socket in the Internet domain of type
Dv SOCK_STREAM
is returned to the caller, and given to the remote
command as
Em stdin
and
Em stdout .
If
Fa fd2p
is non-zero, then an auxiliary channel to a control
process will be set up, and a descriptor for it will be placed
in
Fa *fd2p .
The control process will return diagnostic
output from the command (unit 2) on this channel, and will also
accept bytes on this channel as being
Ux
signal numbers, to be
forwarded to the process group of the command.
If
Fa fd2p
is 0, then the
Em stderr
(unit 2 of the remote
command) will be made the same as the
Em stdout
and no
provision is made for sending arbitrary signals to the remote process,
although you may be able to get its attention by using out-of-band data.
Pp
Fn rcmd_af
and
Fn orcmd_af
take address family in the last argument.
If the last argument is
Dv PF_UNSPEC ,
interpretation of
Fa *ahost
will obey the underlying address resolution like DNS.
Pp
The protocol is described in detail in
Xr rshd 8 .
Pp
The
Fn rresvport
and
Fn rresvport_af
functions are used to obtain a socket with a privileged
address bound to it.  This socket is suitable for use
by
Fn rcmd
and several other functions.  Privileged Internet ports are those
in the range 0 to 1023.  Only the super-user
is allowed to bind an address of this sort to a socket.
Pp
The
Fn iruserok
and
Fn ruserok
functions take a remote host's IP address or name, respectively,
two user names and a flag indicating whether the local user's
name is that of the super-user.
Then, if the user is
Em NOT
the super-user, it checks the
Pa /etc/hosts.equiv
file.
If that lookup is not done, or is unsuccessful, the
Pa .rhosts
in the local user's home directory is checked to see if the request for
service is allowed.
Pp
If this file does not exist, is not a regular file, is owned by anyone
other than the user or the super-user, or is writable by anyone other
than the owner, the check automatically fails.
Zero is returned if the machine name is listed in the
Dq Pa hosts.equiv
file, or the host and remote user name are found in the
Dq Pa .rhosts
file; otherwise
Fn iruserok
and
Fn ruserok
return \-1.
If the local domain (as obtained from
Xr gethostname 3 )
is the same as the remote domain, only the machine name need be specified.
Pp
If the IP address of the remote host is known,
Fn iruserok
should be used in preference to
Fn ruserok ,
as it does not require trusting the DNS server for the remote host's domain.
Pp
While
Fn iruserok
can handle IPv4 addresses only,
Fn iruserok_sa
and
Fn ruserok
can handle other address families as well, like IPv6.
The first argument of
Fn iruserok_sa
is typed as
Fa "void *"
to avoid dependency between
In unistd.h
and
In sys/socket.h .
Sh ENVIRONMENT
Bl -tag -width RCMD_CMDxx -compact
It Ev RCMD_CMD
When using the
Fn rcmd
function, this variable is used as the program to run instead of
Xr rcmd 1 .
El
Sh RETURN VALUES
The
Fn rcmd
function
returns a valid socket descriptor on success.
It returns \-1 on error and prints a diagnostic message on the standard error.
Pp
The
Fn rresvport
and
Fn rresvport_af
function
return a valid, bound socket descriptor on success.
They return \-1 on error with the global value
Va errno
set according to the reason for failure.
The error code
Er EAGAIN
is overloaded to mean ``All network ports in use.''
Sh SEE ALSO
Xr rcmd 1 ,
Xr rlogin 1 ,
Xr rsh 1 ,
Xr intro 2 ,
Xr rexec 3 ,
Xr hosts.equiv 5 ,
Xr rhosts 5 ,
Xr rexecd 8 ,
Xr rlogind 8 ,
Xr rshd 8
Sh HISTORY
The
Fn orcmd ,
Fn rresvport ,
Fn iruserok
and
Fn ruserok
functions appeared in
Bx 4.2 ,
where the
Fn orcmd
function was called
Fn rcmd .
The (newer)
Fn rcmd
function appeared in
Nx 1.3 .
Fn rcmd_af
and
Fn rresvport_af
were defined in RFC2292.

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