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/*
* userbindmount: bindmount as a user (using user-namespaces).
* Copyright (C) 2016 Renzo Davoli, University of Bologna
*
* userbindmount is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; If not, see <http://www.gnu.org/licenses/>.
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <getopt.h>
#include <errno.h>
#include <libgen.h>
#include <sys/mount.h>
#include "userbindmount.h"
char *progname;
int sysadmin_flag = 0;
int verbose_flag = 0;
int newnamespace_flag = 0;
#define errExit(msg) do {\
perror(msg); \
exit(EXIT_FAILURE); \
} while(0);
void usage_n_exit(void) {
fprintf(stderr,
"Usage: %s OPTIONS [source target [source target [...]]] [-- [cmd [args]]] \n"
"OPTIONS:\n"
"\t-n | --newns : create a new namespace\n"
"\t-s | --sysadm : set cap_sys_admin ambient capability\n"
"\t-v | --verbose : verbose mode\n"
"\t-h | --help : print this short help message\n"
"a new user_namespace is created if -- arg is present\n"
"it runs $SHELL if cmd omitted\n"
"the contents of the mounted file is read from stdin if source is '-'\n\n",
progname);
exit(EXIT_SUCCESS);
}
void userbindmount_mount(const char *source, const char *target) {
int retval;
if (*source == 0 || strcmp(source, "-") == 0)
retval = userbindmount_fd(0, target, 0600);
else {
int len = strlen(source);
if (source[0] == '"' && len > 1 && source[len - 1] == '"') {
char string[len];
snprintf(string, len, "%*.*s", len - 2, len - 2, source + 1);
retval = userbindmount_string(string, target, 0600);
} else
retval = mount(source, target, "", MS_BIND, NULL);
}
if (retval < 0)
errExit("mount");
}
static int there_is_dash_dash(char *argv[]) {
for (; *argv != NULL; argv++) {
if (strcmp(argv[0], "--") == 0)
return 1;
}
return 0;
}
int main(int argc, char *argv[]) {
static char *short_options = "+shvn";
static struct option long_options[] = {
{"help", no_argument, 0, 'h'},
{"newns", no_argument, 0, 'n'},
{"sysadm", no_argument, 0, 's'},
{"verbose", no_argument, 0, 'v'},
{0, 0, 0, 0}};
progname = basename(argv[0]);
while (1) {
int c;
if ((c = getopt_long(argc, argv, short_options, long_options, NULL)) == -1)
break;
switch (c) {
case 's': sysadmin_flag = 1; break;
case 'v': verbose_flag = 1; break;
case 'n': newnamespace_flag = 1; break;
case '?':
case 'h':
default: usage_n_exit();
}
}
if (strcmp(argv[optind - 1], "--") == 0)
optind--;
argc -= optind;
argv += optind;
if (there_is_dash_dash(argv))
newnamespace_flag = 1;
if (newnamespace_flag) {
if (verbose_flag)
fprintf(stderr, "creating a user_namespace\n");
if (userbindmount_unshare() < 0)
errExit("unshare");
}
if (sysadmin_flag) {
if (verbose_flag)
fprintf(stderr, "setting sysadm ambient capability\n");
if (userbindmount_set_cap_sysadm() < 0)
errExit("set_cap_sysadm");
}
while (argc >= 2 && strcmp(argv[0],"--") != 0) {
if (verbose_flag)
fprintf(stderr, "mounting %s on %s\n", argv[0], argv[1]);
userbindmount_mount(argv[0], argv[1]);
argc -= 2;
argv += 2;
}
if (newnamespace_flag || argc > 0) {
char **cmdargv;
char *argvsh[]={getenv("SHELL"),NULL};
if (argc > 0 && strcmp(argv[0],"--") == 0) {
argc--;
argv++;
}
cmdargv = (argc == 0) ? argvsh : argv;
if (cmdargv[0] == NULL)
errExit("$SHELL env variable not set\n");
if (verbose_flag)
fprintf(stderr, "starting %s\n", cmdargv[0]);
execvp(cmdargv[0], cmdargv);
}
}
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