alpine 3.9
race weakness #27

5

Weakness Breakdown


Definition:

A race condition exists when parallel code accesses shared data without proper coordination. An attack that uses a race-condition weakness takes advantage of the unsafe data access to manipulate how one of the parallel sections of code reacts. Even though each process runs as intended, the outcome is unexpected. For example, consider a bank service that depends on an encryption key that it reads from a known location. An independent cryptography service is responsible for generating the key and placing it where the bank is expected to read it in a timely manner. If the bank and cryptography services do not coordinate with each other, then the bank may read a blank encryption key before cryptography writes the key to the location. This can effectively turn off all encryption for the bank without either service, or the administrator, knowing that something has gone wrong.

Warning code(s):

This accepts filename arguments; if an attacker can move those files, a race condition results..

File Name:

firejail/src/firejail-0.9.56-LTS-release/src/firejail/fs.c

Context:

The highlighted line of code below is the trigger point of this particular Alpine 3.9 race weakness.

 // todo: last_disable = SUCCESSFUL;
	}
	else if (op == MOUNT_RDWR) {
		if (arg_debug)
			printf("Mounting read-only %s\n", fname);
		fs_rdwr(fname);
// todo: last_disable = SUCCESSFUL;
	}
	else if (op == MOUNT_NOEXEC) {
		if (arg_debug)
			printf("Mounting noexec %s\n", fname);
		fs_noexec(fname);
// todo: last_disable = SUCCESSFUL;
	}
	else if (op == MOUNT_TMPFS) {
		if (S_ISDIR(s.st_mode)) {
			if (arg_debug)
				printf("Mounting tmpfs on %s\n", fname);
			// preserve owner and mode for the directory
			if (mount("tmpfs", fname, "tmpfs", MS_NOSUID | MS_NODEV | MS_STRICTATIME | MS_REC,  0) < 0)
				errExit("mounting tmpfs");
			/* coverity[toctou] */
			if (chown(fname, s.st_uid, s.st_gid) == -1)
				errExit("mounting tmpfs chown");
			if (chmod(fname, s.st_mode) == -1)
				errExit("mounting tmpfs chmod");
			last_disable = SUCCESSFUL;
			fs_logger2("tmpfs", fname);
		}
		else
			fwarning("%s is not a directory; cannot mount a tmpfs on top of it.\n", fname);
	}
	else
		assert(0);

	free(fname);
}

#ifdef TEST_NO_BLACKLIST_MATCHING
static int nbcheck_start = 0;
static size_t nbcheck_size = 0;
static int *nbcheck = NULL;
#endif

// Treat pattern as a shell glob pattern and blacklist matching files
static void globbing(OPERATION op, const char *pattern, const char *noblacklist[], size_t noblacklist_len) {
	assert(pattern);

#ifdef TEST_NO_BLACKLIST_MATCHING
	if (nbcheck_start == 0) { 

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