alpine 3.7
race weakness #1


Weakness Breakdown


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:



The highlighted line of code below is the trigger point of this particular Alpine 3.7 race weakness.

 					while (fgets(buf, sizeof(buf), fi) != NULL)
						fputs(buf, stdout);
				} else {
					fprintf(stderr, "no crontab for %s\n", pas->pw_name);
					/* no error code */
		case EDIT:
				FILE *fi;
				int fd;
				int n;
				char tmp[] = TMPDIR "/crontab.XXXXXX";
				char buf[RW_BUFFER];

				 * Create temp file with perm 0600 and O_EXCL flag, ensuring that this call creates the file
				 * Read from fi for "$ CDir/$ USER", write to fd for temp file
				 * EditFile changes user if necessary, and runs editor on temp file
				 * Then we delete the temp file, keeping its fd as repFd
				if ((fd = mkstemp(tmp)) >= 0) {
					chown(tmp, getuid(), getgid());
					if ((fi = fopen(pas->pw_name, "r"))) {
						while ((n = fread(buf, 1, sizeof(buf), fi)) > 0)
							write(fd, buf, n);
					EditFile(caller, tmp);
					lseek(fd, 0L, 0);
					repFd = fd;
				} else {
					printlogf(0, "unable to create %s: %s", tmp, strerror(errno));

			option = REPLACE;
			/* fall through */
		case REPLACE:
				char buf[RW_BUFFER];
				char path[SMALL_BUFFER];
				int fd;
				int n;

				 * Read from repFd, write to fd for "$ CDir/$" 

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