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
)
)
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_CMD
)
function, this variable is used as the program to run instead of
rcmd(1).
)
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.''
),
rresvport(
),
iruserok(
)
and
ruserok(
)
functions appeared in
4.2BSD,
where the
orcmd(
)
function was called
rcmd(
).
The (newer)
rcmd(
)
function appeared in
NetBSD1.3.
rcmd_af(
)
and
rresvport_af(
)
were defined in RFC2292.