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/*
* Copyright (C) 2014-2019 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/types.h>
#include <sys/stat.h>
#include <unistd.h>
void check_output(int argc, char **argv) {
EUID_ASSERT();
int i;
int outindex = 0;
int enable_stderr = 0;
for (i = 1; i < argc; i++) {
if (strncmp(argv[i], "--", 2) != 0) {
return;
}
if (strcmp(argv[i], "--") == 0) {
return;
}
if (strncmp(argv[i], "--output=", 9) == 0) {
outindex = i;
break;
}
if (strncmp(argv[i], "--output-stderr=", 16) == 0) {
outindex = i;
enable_stderr = 1;
break;
}
}
if (!outindex)
return;
// check filename
drop_privs(0);
char *outfile = argv[outindex];
outfile += (enable_stderr)? 16:9;
invalid_filename(outfile, 0); // no globbing
// do not accept directories, links, and files with ".."
if (strstr(outfile, "..") || is_link(outfile) || is_dir(outfile)) {
fprintf(stderr, "Error: invalid output file. Links, directories and files with \"..\" are not allowed.\n");
exit(1);
}
struct stat s;
if (stat(outfile, &s) == 0) {
// check permissions
if (s.st_uid != getuid() || s.st_gid != getgid()) {
fprintf(stderr, "Error: the output file needs to be owned by the current user.\n");
exit(1);
}
// check hard links
if (s.st_nlink != 1) {
fprintf(stderr, "Error: no hard links allowed.\n");
exit(1);
}
}
int pipefd[2];
if (pipe(pipefd) == -1) {
errExit("pipe");
}
pid_t pid = fork();
if (pid == -1) {
errExit("fork");
} else if (pid == 0) {
/* child */
if (dup2(pipefd[0], STDIN_FILENO) == -1) {
errExit("dup2");
}
close(pipefd[1]);
if (pipefd[0] != STDIN_FILENO) {
close(pipefd[0]);
}
char *args[3];
args[0] = LIBDIR "/firejail/ftee";
args[1] = outfile;
args[2] = NULL;
execv(args[0], args);
perror("execvp");
exit(1);
}
/* parent */
if (dup2(pipefd[1], STDOUT_FILENO) == -1) {
errExit("dup2");
}
if (enable_stderr && dup2(STDOUT_FILENO, STDERR_FILENO) == -1) {
errExit("dup2");
}
close(pipefd[0]);
if (pipefd[1] != STDOUT_FILENO) {
close(pipefd[1]);
}
char **args = calloc(argc + 1, sizeof(char *));
if (!args) {
errExit("calloc");
}
bool found_separator = false;
/* copy argv into args, but drop --output(-stderr) arguments */
int j;
for (i = 0, j = 0; i < argc; i++) {
if (!found_separator && i > 0) {
if (strncmp(argv[i], "--output=", 9) == 0) {
continue;
}
if (strncmp(argv[i], "--output-stderr=", 16) == 0) {
continue;
}
if (strncmp(argv[i], "--", 2) != 0 || strcmp(argv[i], "--") == 0) {
found_separator = true;
}
}
args[j++] = argv[i];
}
execvp(args[0], args);
perror("execvp");
exit(1);
}
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