Allow users to specify a command to use as remote command instead of

using rcmd directly.  This has been in my tree for a long time, but we
may need to sync with OpenBSD before MFC.

Obtained from: openbsd
PR: 15830

MFC after: 2 months

1 files changed, 130 insertions, 0 deletions

diff --git a/lib/libc/net/rcmdsh.c b/lib/libc/net/rcmdsh.c
new file mode 100644
index 0000000..6ead7d1
--- /dev/null
+++ b/lib/libc/net/rcmdsh.c
@@ -0,0 +1,130 @@
+/*	$OpenBSD: rcmdsh.c,v 1.5 1998/04/25 16:23:58 millert Exp $	*/ 
+
+/*
+ * This is an rcmd() replacement originally by 
+ * Chris Siebenmann <cks@utcc.utoronto.ca>.
+ *
+ * $FreeBSD$
+ */
+
+#if defined(LIBC_SCCS) && !defined(lint)
+static char *rcsid = "$FreeBSD$"
+#endif /* LIBC_SCCS and not lint */
+
+#include      <sys/types.h>
+#include      <sys/socket.h>
+#include      <sys/wait.h>
+#include      <signal.h>
+#include      <errno.h>
+#include      <netdb.h>
+#include      <stdio.h>
+#include      <string.h>
+#include      <pwd.h>
+#include      <paths.h>
+#include      <unistd.h>
+
+#ifndef _PATH_RSH
+#define _PATH_RSH "/usr/bin/rsh"
+#endif
+
+/*
+ * This is a replacement rcmd() function that uses the rsh(1)
+ * program in place of a direct rcmd(3) function call so as to
+ * avoid having to be root.  Note that rport is ignored.
+ */
+/* ARGSUSED */
+int
+rcmdsh(ahost, rport, locuser, remuser, cmd, rshprog)
+	char **ahost;
+	int rport;
+	const char *locuser, *remuser, *cmd;
+	char *rshprog;
+{
+	struct hostent *hp;
+	int cpid, sp[2];
+	char *p;
+	struct passwd *pw;
+
+	/* What rsh/shell to use. */
+	if (rshprog == NULL)
+		rshprog = _PATH_RSH;
+
+	/* locuser must exist on this host. */
+	if ((pw = getpwnam(locuser)) == NULL) {
+		(void) fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser);
+		return(-1);
+	}
+
+	/* Validate remote hostname. */
+	if (strcmp(*ahost, "localhost") != 0) {
+		if ((hp = gethostbyname(*ahost)) == NULL) {
+			herror(*ahost);
+			return(-1);
+		}
+		*ahost = hp->h_name;
+	}
+
+	/* Get a socketpair we'll use for stdin and stdout. */
+	if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) < 0) {
+		perror("rcmdsh: socketpair");
+		return(-1);
+	}
+
+	cpid = fork();
+	if (cpid < 0) {
+		perror("rcmdsh: fork failed");
+		return(-1);
+	} else if (cpid == 0) {
+		/*
+		 * Child.  We use sp[1] to be stdin/stdout, and close sp[0].
+		 */
+		(void) close(sp[0]);
+		if (dup2(sp[1], 0) < 0 || dup2(0, 1) < 0) {
+			perror("rcmdsh: dup2 failed");
+			_exit(255);
+		}
+		/* Fork again to lose parent. */
+		cpid = fork();
+		if (cpid < 0) {
+			perror("rcmdsh: fork to lose parent failed");
+			_exit(255);
+		}
+		if (cpid > 0)
+			_exit(0);
+
+		/* In grandchild here.  Become local user for rshprog. */
+		if (setuid(pw->pw_uid)) {
+			(void) fprintf(stderr, "rcmdsh: setuid(%u): %s\n",
+				       pw->pw_uid, strerror(errno));
+			_exit(255);
+		}
+
+		/*
+		 * If remote host is "localhost" and local and remote user
+		 * are the same, avoid running remote shell for efficiency.
+		 */
+		if (!strcmp(*ahost, "localhost") && !strcmp(locuser, remuser)) {
+			if (pw->pw_shell[0] == '\0')
+				rshprog = _PATH_BSHELL;
+			else
+				rshprog = pw->pw_shell;
+			p = strrchr(rshprog, '/');
+			execlp(rshprog, p ? p+1 : rshprog, "-c", cmd,
+			       (char *) NULL);
+		} else {
+			p = strrchr(rshprog, '/');
+			execlp(rshprog, p ? p+1 : rshprog, *ahost, "-l",
+			       remuser, cmd, (char *) NULL);
+		}
+		(void) fprintf(stderr, "rcmdsh: execlp %s failed: %s\n",
+			       rshprog, strerror(errno));
+		_exit(255);
+	} else {
+		/* Parent. close sp[1], return sp[0]. */
+		(void) close(sp[1]);
+		/* Reap child. */
+		(void) wait(NULL);
+		return(sp[0]);
+	}
+	/* NOTREACHED */
+}