centos 6
race weakness #25

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:

lrzsz-0.12.20/src/lrz.c

Context:

The highlighted line of code below is the trigger point of this particular Centos 6 race weakness.

 	}
	if (zi->modtime) {
#ifdef HAVE_STRUCT_UTIMBUF
		struct utimbuf timep;
		timep.actime = time(NULL);
		timep.modtime = zi->modtime;
		utime(Pathname, &timep);
#else
		time_t timep[2];
		timep[0] = time(NULL);
		timep[1] = zi->modtime;
		utime(Pathname, timep);
#endif
	}
#ifdef S_ISREG
	if (S_ISREG(zi->mode)) {
#else
	if ((zi->mode&S_IFMT) == S_IFREG) {
#endif
		/* we must not make this program executable if running 
		 * under rsh, because the user might have uploaded an
		 * unrestricted shell.
		 */
		if (under_rsh)
			chmod(Pathname, (00666 & zi->mode));
		else
			chmod(Pathname, (07777 & zi->mode));
	}
	return OK;
}

/*
 * Ack a ZFIN packet, let byegones be byegones
 */
static void
ackbibi(void)
{
	int n;

	vfile("ackbibi:");
	Readnum = 1;
	stohdr(0L);
	for (n=3; --n>=0; ) {
		purgeline(0);
		zshhdr(ZFIN, Txhdr);
		switch (READLINE_PF(100)) {
		case 'O':
			READLINE_PF(1);	/* Discard 2nd 'O' */
			vfile("ackbibi complete");
			return; 

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