RCMD(3) | Library Functions Manual | RCMD(3) |
rcmd
, orcmd
,
rcmd_af
, orcmd_af
,
rresvport
, rresvport_af
,
iruserok
, ruserok
,
iruserok_sa
—
#include <unistd.h>
int
rcmd
(char
**ahost, int
inport, const char
*locuser, const char
*remuser, const char
*cmd, int
*fd2p);
int
orcmd
(char
**ahost, int
inport, const char
*locuser, const char
*remuser, const char
*cmd, int
*fd2p);
int
rcmd_af
(char
**ahost, int
inport, const char
*locuser, const char
*remuser, const char
*cmd, int *fd2p,
int af);
int
orcmd_af
(char
**ahost, int
inport, const char
*locuser, const char
*remuser, const char
*cmd, int *fd2p,
int af);
int
rresvport
(int
*port);
int
rresvport_af
(int
*port, int
family);
int
iruserok
(uint32_t
raddr, int
superuser, const char
*ruser, const char
*luser);
int
ruserok
(const
char *rhost, int
superuser, const char
*ruser, const char
*luser);
int
iruserok_sa
(const
void *raddr, int
rlen, int
superuser, const char
*ruser, const char
*luser);
rcmd
() function is available for use by anyone to
run commands on a remote system. It acts like the
orcmd
() command, with the exception that it makes a
call out to the 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 “shell/tcp” port. The
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 rcmd
() and
orcmd
() can only handle IPv4 address in the first
argument, rcmd_af
() and
orcmd_af
() can handle other cases as well. The
rresvport
() function returns a descriptor to a socket
with an address in the privileged port space. The
rresvport_af
() function is similar to
rresvport
(), but you can explicitly specify the
address family to use. Calling rresvport_af
() with
AF_INET
has the same effect as
rresvport
(). The iruserok
()
and ruserok
() functions are used by servers to
authenticate clients requesting service with rcmd
().
All six functions are present in the same file and are used by the
rshd(8) server (among others).
iruserok_sa
() is an address family independent variant
of iruserok
().
The rcmd
() function looks up the host
*ahost using
gethostbyname(3),
returning -1 if the host does not exist. Otherwise
*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 inport.
If the connection succeeds, a socket in the Internet domain of
type SOCK_STREAM
is returned to the caller, and
given to the remote command as stdin and
stdout. If 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 *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 UNIX
signal numbers, to be forwarded to the process group of the command. If
fd2p is 0, then the stderr (unit 2
of the remote command) will be made the same as the 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.
rcmd_af
() and
orcmd_af
() take address family in the last argument.
If the last argument is PF_UNSPEC
, interpretation of
*ahost will obey the underlying address resolution
like DNS.
The protocol is described in detail in rshd(8).
The rresvport
() and
rresvport_af
() functions are used to obtain a socket
with a privileged address bound to it. This socket is suitable for use by
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.
The iruserok
() and
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
NOT the super-user, it checks the
/etc/hosts.equiv file. If that lookup is not done,
or is unsuccessful, the .rhosts in the local user's
home directory is checked to see if the request for service is allowed.
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
“hosts.equiv” file, or the host and
remote user name are found in the
“.rhosts” file; otherwise
iruserok
() and ruserok
()
return -1. If the local domain (as obtained from
gethostname(3)) is the
same as the remote domain, only the machine name need be specified.
If the IP address of the remote host is known,
iruserok
() should be used in preference to
ruserok
(), as it does not require trusting the DNS
server for the remote host's domain.
While iruserok
() can handle IPv4 addresses
only, iruserok_sa
() and
ruserok
() can handle other address families as well,
like IPv6. The first argument of iruserok_sa
() is
typed as void * to avoid dependency between
<unistd.h>
and
<sys/socket.h>
.
rcmd
() function returns a valid socket descriptor on
success. It returns -1 on error and prints a diagnostic message on the
standard error.
The rresvport
() and
rresvport_af
() function return a valid, bound socket
descriptor on success. They return -1 on error with the global value
errno set according to the reason for failure. The
error code EAGAIN
is overloaded to mean ``All
network ports in use.''
orcmd
(), rresvport
(),
iruserok
() and ruserok
()
functions appeared in 4.2BSD, where the
orcmd
() function was called
rcmd
(). The (newer) rcmd
()
function appeared in NetBSD 1.3.
rcmd_af
() and rresvport_af
()
were defined in RFC2292.
March 30, 2005 | NetBSD 9.2 |