Full Disclosure mailing list archives
temporary file creation vulnerability in Redis
From: Matthew Hall <mhall () mhcomputing net>
Date: Fri, 21 Feb 2014 17:33:27 -0800
See also: https://github.com/antirez/redis/issues/1560 . I have been trying to reach the Redis maintainers since 2013-09-13 regarding this report, but I could not find a good security contact for Redis, and the lead maintainer, Salvatore Sanfilippo <antirez () gmail com> is not replying to my private report to him about the issue and his opinion of it. I also contacted US-CERT for help and they could not reach anyone by 2014-01-24. Therefore I would like to encourage the Redis team to be more security-friendly and establish some contact procedures on their website. Given how many places this software is now being used these days, I think it is very critical to make these changes before someone finds something more serious than the one I could spot. I think I might have discovered a security vulnerability in Redis 2.6.16. This code is from the function int rdbSave(char *filename) in rdb.c: 630 int rdbSave(char *filename) { 631 dictIterator *di =3D NULL; 632 dictEntry *de; 633 char tmpfile[256]; 634 char magic[10]; 635 int j; 636 long long now =3D mstime(); 637 FILE *fp; 638 rio rdb; 639 uint64_t cksum; 640 641 snprintf(tmpfile,256,"temp-%d.rdb", (int) getpid()); 642 fp =3D fopen(tmpfile,"w"); 643 if (!fp) { 644 redisLog(REDIS_WARNING, "Failed opening .rdb for saving: %s", 645 strerror(errno)); 646 return REDIS_ERR; 647 } ... 692 /* Make sure data will not remain on the OS's output buffers */ 693 fflush(fp); 694 fsync(fileno(fp)); 695 fclose(fp); 696 697 /* Use RENAME to make sure the DB file is changed atomically only 698 * if the generate DB file is ok. */ 699 if (rename(tmpfile,filename) =3D=3D -1) { 700 redisLog(REDIS_WARNING,"Error moving temp DB file on the final destination: %s", strerror(errno)); 701 unlink(tmpfile); 702 return REDIS_ERR; 703 } In line 641, the function does not use a security temporary file creation routine such as mkstemp. This is vulnerable to a wide range of attacks which could result in overwriting (in line 693-695) and unlinking (in line 701) any file / hard link / symlink placed in temp-PID.rdb by an attacker. https://www.owasp.org/index.php/Improper_temp_file_opening https://www.owasp.org/index.php/Insecure_Temporary_File The code should be creating the temporary file using some kind of safe function like mkstemp, O_EXCL open, etc. instead of just using a PID value which does not have enough entropy and protection from race conditions. It should also be sure it has set the CWD of itself to a known-safe location that should have permissions which are only open to the redis daemon / redis user and not to other users or processes. Thanks, Matthew Hall _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/
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- temporary file creation vulnerability in Redis Matthew Hall (Feb 22)