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/* $OpenBSD: rcmdsh.c,v 1.20 2019/06/28 13:32:42 deraadt Exp $ */
/*
* Copyright (c) 2001, MagniComp
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the distribution.
* 3. Neither the name of the MagniComp nor the names of its contributors may
* be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR
* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
* USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* This is an rcmd() replacement originally by
* Chris Siebenmann <cks@utcc.utoronto.ca>.
*/
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <signal.h>
#include <errno.h>
#include <limits.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <pwd.h>
#include <paths.h>
#include <unistd.h>
/*
* This is a replacement rcmd() function that uses the ssh(1)
* program in place of a direct rcmd(3) function call so as to
* avoid having to be root. Note that rport is ignored.
*/
int
rcmdsh(char **ahost, int rport, const char *locuser, const char *remuser,
const char *cmd, char *rshprog)
{
static char hbuf[HOST_NAME_MAX+1];
struct addrinfo hint, *res;
int sp[2];
pid_t cpid;
char *p, pwbuf[_PW_BUF_LEN];
struct passwd pwstore, *pw = NULL;
/* What rsh/shell to use. */
if (rshprog == NULL)
rshprog = _PATH_RSH;
/* locuser must exist on this host. */
getpwnam_r(locuser, &pwstore, pwbuf, sizeof(pwbuf), &pw);
if (pw == NULL) {
(void) fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser);
return(-1);
}
/* Validate remote hostname. */
if (strcmp(*ahost, "localhost") != 0) {
memset(&hint, 0, sizeof(hint));
hint.ai_family = PF_UNSPEC;
hint.ai_flags = AI_CANONNAME;
if (getaddrinfo(*ahost, NULL, &hint, &res) == 0) {
if (res->ai_canonname) {
strlcpy(hbuf, res->ai_canonname, sizeof(hbuf));
*ahost = hbuf;
}
freeaddrinfo(res);
}
}
/* Get a socketpair we'll use for stdin and stdout. */
if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) == -1) {
perror("rcmdsh: socketpair");
return(-1);
}
cpid = fork();
if (cpid == -1) {
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) == -1 || dup2(0, 1) == -1) {
perror("rcmdsh: dup2 failed");
_exit(255);
}
/* Fork again to lose parent. */
cpid = fork();
if (cpid == -1) {
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)) {
char *argv[4];
if (pw->pw_shell[0] == '\0')
rshprog = _PATH_BSHELL;
else
rshprog = pw->pw_shell;
p = strrchr(rshprog, '/');
argv[0] = p ? p + 1 : rshprog;
argv[1] = "-c";
argv[2] = (char *)cmd;
argv[3] = NULL;
execvp(rshprog, argv);
} else if ((p = strchr(rshprog, ' ')) == NULL) {
/* simple case */
char *argv[6];
p = strrchr(rshprog, '/');
argv[0] = p ? p + 1 : rshprog;
argv[1] = "-l";
argv[2] = (char *)remuser;
argv[3] = *ahost;
argv[4] = (char *)cmd;
argv[5] = NULL;
execvp(rshprog, argv);
} else {
/* must pull args out of rshprog and dyn alloc argv */
char **argv, **ap;
int n;
for (n = 7; (p = strchr(++p, ' ')) != NULL; n++)
continue;
rshprog = strdup(rshprog);
ap = argv = calloc(sizeof(char *), n);
if (rshprog == NULL || argv == NULL) {
perror("rcmdsh");
_exit(255);
}
while ((p = strsep(&rshprog, " ")) != NULL) {
if (*p == '\0')
continue;
*ap++ = p;
}
if (ap != argv) /* all spaces?!? */
rshprog = argv[0];
if ((p = strrchr(argv[0], '/')) != NULL)
argv[0] = p + 1;
*ap++ = "-l";
*ap++ = (char *)remuser;
*ap++ = *ahost;
*ap++ = (char *)cmd;
*ap++ = NULL;
execvp(rshprog, argv);
}
(void) fprintf(stderr, "rcmdsh: execvp %s failed: %s\n",
rshprog, strerror(errno));
_exit(255);
} else {
/* Parent. close sp[1], return sp[0]. */
(void) close(sp[1]);
/* Reap child. */
while (waitpid(cpid, NULL, 0) == -1 && errno == EINTR)
;
return(sp[0]);
}
/* NOTREACHED */
}
DEF_WEAK(rcmdsh);
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