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'\" te .\" Copyright (c) 1983, Regents of the University of California. All rights reserved. The Berkeley software License Agreement specifies the terms and conditions for redistribution. .\" Portions Copyright (c) 2004, 2021, Oracle and/or its affiliates. .TH rcmd 3C "3 Nov 2021" "Oracle Solaris 11.4" "Standard C Library Functions" .SH NAME rcmd, rcmd_af, rresvport, rresvport_af, ruserok \- routines for returning a stream to a remote command .SH SYNOPSIS .LP .nf #include <netdb.h> #include <unistd.h> \fBint\fR \fBrcmd\fR(\fBchar **\fR\fIahost\fR, \fBunsigned short\fR \fIinport\fR, \fBconst char *\fR\fIluser\fR, \fBconst char *\fR\fIruser\fR, \fBconst char *\fR\fIcmd\fR, \fBint *\fR\fIfd2p\fR); .fi .LP .nf \fBint\fR \fBrcmd_af\fR(\fBchar **\fR\fIahost\fR, \fBunsigned short\fR \fIinport\fR, \fBconst char *\fR\fIluser\fR, \fBconst char *\fR\fIruser\fR, \fBconst char *\fR\fIcmd\fR, \fBint *\fR\fIfd2p\fR, \fBint\fR \fIaf\fR); .fi .LP .nf \fBint\fR \fBrresvport\fR(\fBint *\fR\fIport\fR); .fi .LP .nf \fBint\fR \fBrresvport_af\fR(\fBint *\fR\fIport\fR, \fBint\fR \fIaf\fR); .fi .LP .nf \fBint\fR \fBruserok\fR(\fBconst char *\fR\fIrhost\fR, \fBint\fR \fIsuser\fR, \fBconst char *\fR\fIruser\fR, \fBconst char *\fR\fIluser\fR); .fi .SH DESCRIPTION .sp .LP The \fBrcmd()\fR and \fBrcmd_af()\fR functions execute a command on a remote machine with an authentication scheme based on privileged port numbers. The {\fBPRIV_NET_PRIVADDR\fR} privilege is required to use these functions so they can bind a socket to a privileged port number. An \fBAF_INET\fR socket is returned with \fBrcmd()\fR. The \fBrcmd_af()\fR function supports \fBAF_INET\fR, \fBAF_INET6\fR, or \fBAF_UNSPEC\fR for the address family. An application can choose which type of socket is returned by passing \fBAF_INET\fR or \fBAF_INET6\fR as the address family. The use of \fBAF_UNSPEC\fR means that the caller will accept any address family. Choosing \fBAF_UNSPEC\fR provides a socket that best suits the connectivity to the remote host. .sp .LP The \fBrcmd()\fR and \fBrcmd_af()\fR functions look up the host \fI*ahost\fR using \fBgetaddrinfo\fR(3C) and return \fB\(mi1\fR if the host does not exist. Otherwise, *\fIahost\fR is set to the standard name of the host and a connection is established to a server residing at the Internet port \fIinport\fR. .sp .LP If the connection succeeds, a socket in the Internet domain of type \fBSOCK_STREAM\fR is returned to the caller. The socket is given to the remote command as standard input (file descriptor 0) and standard output (file descriptor 1). If \fIfd2p\fR is non-zero, an auxiliary channel to a control process is set up and a descriptor for it is placed in \fI*fd2p\fR. The control process returns diagnostic output file (descriptor 2) from the command on the auxiliary channel. The control process also accepts bytes on this channel as signal numbers to be forwarded to the process group of the command. If \fIfd2p\fR is 0, the standard error (file descriptor 2) of the remote command is made the same as its standard output. No provision is made for sending arbitrary signals to the remote process, other than possibly sending out-of-band data. .sp .LP The protocol is described in detail in \fBin.rshd\fR(8). .sp .LP The \fBrresvport()\fR and \fBrresvport_af()\fR functions are used to obtain a socket bound to a privileged port number. Privileged Internet ports are those in the range 1 to 1023. The {\fBPRIV_NET_PRIVADDR\fR} privilege is required to bind a socket to a privileged port number. The application must pass in \fIport\fR, which must be in the range 512 to 1023. The system first tries to bind to that port number. If it fails, the system then tries to bind to another unused privileged port, if one is available. .sp .LP The \fBrresvport()\fR function returns a descriptor to a socket in the Internet domain of type \fBSOCK_STREAM\fR with an address in the \fBAF_INET\fR address family. The \fBrresvport_af()\fR function is the equivalent to \fBrresvport()\fR, except that you can choose \fBAF_INET\fR or \fBAF_INET6\fR as the socket address family to be returned by \fBrresvport_af()\fR. \fBAF_UNSPEC\fR does not apply to the \fBrresvport_af()\fR function. .sp .LP The \fBruserok()\fR function is a routine used by servers to authenticate clients that request a service with \fBrcmd()\fR. The \fBruserok()\fR function takes a remote host name returned by the \fBgethostbyaddr()\fR function with two user names and a flag to indicate whether the local user's name is that of the superuser. See \fBgethostbyname\fR(3C). The \fBruserok()\fR function then checks the files \fB/etc/hosts.equiv\fR and possibly \fB.rhosts\fR in the local user's home directory to see if the request for service is allowed. A \fB0\fR value is returned if the machine name is listed in the \fB/etc/hosts.equiv\fR file, or if the host and remote user name are found in the \fB.rhosts\fR file. Otherwise, the \fBruserok()\fR function returns \fB\(mi1\fR. If the superuser flag is \fB1\fR, the \fB/etc/hosts.equiv\fR is not checked. .SH RETURN VALUES .sp .LP The \fBrcmd()\fR and \fBrcmd_af()\fR functions return a valid socket descriptor upon success. The functions return \fB\(mi1\fR upon error and print a diagnostic message to standard error. .sp .LP The \fBrresvport()\fR and \fBrresvport_af()\fR functions return a valid, bound socket descriptor upon success. The functions return \fB\(mi1\fR upon error with the global value \fIerrno\fR set according to the reason for failure. .sp .LP The error code \fBEAGAIN\fR is overloaded to mean "All privileged network ports in use." .SH FILES .sp .ne 2 .mk .na \fB\fB/etc/hosts.equiv\fR\fR .ad .RS 20n .rt system trusted hosts and users .RE .sp .ne 2 .mk .na \fB\fB~/.rhosts\fR\fR .ad .RS 20n .rt user's trusted hosts and users .RE .SH USAGE .sp .LP The protocols underlying these functions use weak authentication and offer no protection against spoofing or snooping of traffic. The \fBin.rshd\fR(8) server is disabled by default on Oracle Solaris and most other modern operating systems. Use of the \fBsshd\fR(8) server is strongly recommended instead, and a programming interface to it is available via the \fBlibssh2\fR library. .sp .LP The range of privileged ports used by these functions does not take into account changes to the \fBsmallest-nonpriv-port\fR and \fBextra-priv-ports\fR properties by \fBipadm\fR(8). .SH ATTRIBUTES .sp .LP See \fBattributes\fR(7) for descriptions of the following attributes: .sp .TS tab( ) box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) . ATTRIBUTE TYPE ATTRIBUTE VALUE _ Interface Stability Committed _ MT-Level Unsafe .TE .sp .sp .LP This interface is Unsafe in multithreaded applications. Unsafe interfaces should be called only from the main thread. .SH SEE ALSO .sp .LP \fBrlogin\fR(1), \fBrsh\fR(1), \fBIntro\fR(2), \fBgetaddrinfo\fR(3C), \fBgethostbyname\fR(3C), \fBrexec\fR(3C), \fBattributes\fR(7), \fBprivileges\fR(7), \fBin.rexecd\fR(8), \fBin.rshd\fR(8) .SH HISTORY .sp .LP The \fBrcmd_af()\fR and \fBrresvport_af()\fR functions were added to Oracle Solaris in the Solaris 8 release. .sp .LP The \fBrcmd()\fR, \fBrresvport()\fR, and \fBruserok()\fR functions have been present since the initial release of Solaris.