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/*
* Copyright (C) 2014-2023 Firejail Authors
*
* This file is part of firejail project
*
* This program 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, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "firejail.h"
#include <sys/stat.h>
static char **paths = 0;
static unsigned int path_cnt = 0;
static unsigned int longest_path_elt = 0;
static char *elt = NULL; // moved from inside init_paths in order to get rid of scan-build warning
static void init_paths(void) {
const char *env_path = env_get("PATH");
char *p;
if (!env_path) {
env_path = "/usr/local/bin:/usr/bin:/bin:/usr/local/sbin:/usr/sbin:/sbin";
env_store_name_val("PATH", env_path, SETENV);
}
char *path = strdup(env_path);
if (!path)
errExit("strdup");
// size the paths array
for (p = path; *p; p++)
if (*p == ':')
path_cnt++;
path_cnt += 2; // one because we were counting fenceposts, one for the NULL at the end
paths = calloc(path_cnt, sizeof(char *));
if (!paths)
errExit("calloc");
memset(paths, 0, path_cnt * sizeof(char *)); // get rid of false positive error from GCC static analyzer
// lots of distros set /bin as a symlink to /usr/bin;
// we remove /bin form the path to speed up path-based operations such as blacklist
int bin_symlink = 0;
p = realpath("/bin", NULL);
if (p) {
if (strcmp(p, "/usr/bin") == 0)
bin_symlink = 1;
}
free(p);
// fill in 'paths' with pointers to elements of 'path'
unsigned int i = 0, j;
unsigned int len;
while ((elt = strsep(&path, ":")) != NULL) {
// skip any entry that is not absolute
if (elt[0] != '/')
goto skip;
// strip trailing slashes (this also prevents '/' from being a path entry).
len = strlen(elt);
while (len > 0 && elt[len-1] == '/')
elt[--len] = '\0';
if (len == 0)
goto skip;
//deal with /bin - /usr/bin symlink
if (bin_symlink > 0) {
if (strcmp(elt, "/bin") == 0 || strcmp(elt, "/usr/bin") == 0)
bin_symlink++;
if (bin_symlink == 3) {
bin_symlink = 0;
if (arg_debug)
printf("...skip path %s\n", elt);
goto skip;
}
}
// filter out duplicate entries
for (j = 0; j < i; j++)
if (strcmp(elt, paths[j]) == 0)
goto skip;
if (arg_debug)
printf("Add path entry %s\n", elt);
paths[i++] = elt;
if (len > longest_path_elt)
longest_path_elt = len;
skip:;
}
assert(paths[i] == NULL);
path_cnt = i;
if (arg_debug)
printf("Number of path entries: %d\n", path_cnt);
// path_cnt may be too big now, if entries were skipped above
path_cnt = i+1;
}
char **build_paths(void) {
if (!paths)
init_paths();
assert(paths);
return paths;
}
// Note: the NULL element at the end of 'paths' is included in this count.
unsigned int count_paths(void) {
if (!path_cnt)
init_paths();
assert(path_cnt);
return path_cnt;
}
// Return 1 if PROGRAM exists in $PATH and is runnable by the
// invoking user (not root).
// In other words, tests "will execvp(PROGRAM, ...) succeed?"
int program_in_path(const char *program) {
assert(program && *program);
assert(strchr(program, '/') == 0);
assert(strcmp(program, ".") != 0);
assert(strcmp(program, "..") != 0);
if (!paths)
init_paths();
assert(paths);
size_t proglen = strlen(program);
char *scratch = malloc(longest_path_elt + proglen + 2);
if (!scratch)
errExit("malloc");
int found = 0;
size_t dlen;
char **p;
for (p = paths; *p; p++) {
char *dir = *p;
dlen = strlen(dir);
// init_paths should ensure that this is true; as long
// as it is true, 'scratch' has enough space for "$p/$program".
assert(dlen <= longest_path_elt);
memcpy(scratch, dir, dlen);
scratch[dlen++] = '/';
// copy proglen+1 bytes to copy the nul terminator at
// the end of 'program'.
memcpy(scratch + dlen, program, proglen+1);
if (access(scratch, X_OK) == 0) {
// must also verify that this is a regular file
// ('x' permission means something different for directories).
// exec follows symlinks, so use stat, not lstat.
struct stat st;
if (stat_as_user(scratch, &st)) {
perror(scratch);
exit(1);
}
if (S_ISREG(st.st_mode)) {
found = 1;
break;
}
}
}
free(scratch);
return found;
}
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