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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 "ftee.h"
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#define MAXBUF 512
static unsigned char buf[MAXBUF];
static FILE *out_fp = NULL;
static int out_cnt = 0;
static int out_max = 500 * 1024;
static void log_close(void) {
if (out_fp) {
fclose(out_fp);
out_fp = NULL;
}
}
static void log_rotate(const char *fname) {
struct stat s;
int index = strlen(fname);
char *name1 = malloc(index + 2 + 1);
char *name2 = malloc(index + 2 + 1);
if (!name1 || !name2)
errExit("malloc");
strcpy(name1, fname);
strcpy(name2, fname);
fflush(0);
// delete filename.5
sprintf(name1 + index, ".5");
if (stat(name1, &s) == 0) {
int rv = unlink(name1);
if (rv == -1)
perror("unlink");
}
// move files 1 to 4 down one position
sprintf(name2 + index, ".4");
if (stat(name2, &s) == 0) {
int rv = rename(name2, name1);
if (rv == -1)
perror("rename");
}
sprintf(name1 + index, ".3");
if (stat(name1, &s) == 0) {
int rv = rename(name1, name2);
if (rv == -1)
perror("rename");
}
sprintf(name2 + index, ".2");
if (stat(name2, &s) == 0) {
/* coverity[toctou] */
int rv = rename(name2, name1);
if (rv == -1)
perror("rename");
}
sprintf(name1 + index, ".1");
if (stat(name1, &s) == 0) {
int rv = rename(name1, name2);
if (rv == -1)
perror("rename");
}
// move the first file
if (out_fp)
fclose(out_fp);
out_fp = NULL;
if (stat(fname, &s) == 0) {
int rv = rename(fname, name1);
if (rv == -1)
perror("rename");
}
free(name1);
free(name2);
}
static void log_write(const unsigned char *str, int len, const char *fname) {
assert(fname);
if (out_fp == NULL) {
out_fp = fopen(fname, "w");
if (!out_fp) {
fprintf(stderr, "Error: cannot open log file %s\n", fname);
exit(1);
}
out_cnt = 0;
}
// rotate files
out_cnt += len;
if (out_cnt >= out_max) {
log_rotate(fname);
// reopen the first file
if (out_fp)
fclose(out_fp);
out_fp = fopen(fname, "w");
if (!out_fp) {
fprintf(stderr, "Error: cannot open log file %s\n", fname);
exit(1);
}
out_cnt = len;
}
int rv = fwrite(str, len, 1, out_fp);
(void) rv;
fflush(0);
}
// return 1 if the file is a directory
static int is_dir(const char *fname) {
assert(fname);
if (*fname == '\0')
return 0;
// if fname doesn't end in '/', add one
int rv;
struct stat s;
if (fname[strlen(fname) - 1] == '/')
rv = stat(fname, &s);
else {
char *tmp;
if (asprintf(&tmp, "%s/", fname) == -1) {
fprintf(stderr, "Error: cannot allocate memory, %s:%d\n", __FILE__, __LINE__);
exit(1);
}
rv = stat(tmp, &s);
free(tmp);
}
if (rv == -1)
return 0;
if (S_ISDIR(s.st_mode))
return 1;
return 0;
}
// return 1 if the file is a link
static int is_link(const char *fname) {
assert(fname);
if (*fname == '\0')
return 0;
struct stat s;
if (lstat(fname, &s) == 0) {
if (S_ISLNK(s.st_mode))
return 1;
}
return 0;
}
static const char *const usage_str =
"Usage: ftee filename\n";
static void usage(void) {
puts(usage_str);
}
int main(int argc, char **argv) {
if (argc < 2) {
fprintf(stderr, "Error: please provide a filename to store the program output\n");
usage();
exit(1);
}
if (strcmp(argv[1], "--help") == 0) {
usage();
return 0;
}
char *fname = argv[1];
// do not accept directories, links, and files with ".."
if (strstr(fname, "..") || is_link(fname) || is_dir(fname))
goto errexit;
struct stat s;
if (stat(fname, &s) == 0) {
// check permissions
if (s.st_uid != getuid() || s.st_gid != getgid())
goto errexit;
// check hard links
if (s.st_nlink != 1)
goto errexit;
}
// check if we can append to this file
/* coverity[toctou] */
FILE *fp = fopen(fname, "a");
if (!fp)
goto errexit;
fclose(fp);
// preserve the last log file
log_rotate(fname);
setvbuf (stdout, NULL, _IONBF, 0);
while(1) {
int n = read(0, buf, sizeof(buf));
if (n < 0 && errno == EINTR)
continue;
if (n <= 0)
break;
int rv = fwrite(buf, n, 1, stdout);
(void) rv;
log_write(buf, n, fname);
}
log_close();
return 0;
errexit:
fprintf(stderr, "Error ftee: invalid output file.\n");
return 1;
}
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