CVE-2024-33599: nscd: Stack-based buffer overflow in netgroup cache

A stack-based buffer overflow in nscd was reported and assigned CVE-2024-33599.

Reference: https://sourceware.org/bugzilla/showbug.cgi?id=31677

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nscd/netgroupcache.c (addinnetgrX):

497 struct indataset 498 { 499 struct datahead head; 500 innetgroupresponseheader resp; 501 } dataset 502 = (struct indataset ) mempoolalloc (db, 503 sizeof (dataset) + req->keylen, 504 1);

mempoolalloc fails and returns NULL.

This is possible if posixfallocate fails and the retry fails.

505 struct indataset datasetmem; 506 bool cacheable = true; 507 if (glibcunlikely (dataset == NULL)) 508 { 509 cacheable = false; 510 dataset = &datasetmem;

This structure has no room for req->keylen material.

511 } 512 513 dataheadinitpos (&dataset->head, sizeof (dataset) + req->keylen, 514 sizeof (innetgroupresponseheader), 515 he == NULL ? 0 : dh->nreloads + 1, result->head.ttl); 516 / Set the notfound status and timeout based on the result from 517 getnetgrent. / 518 dataset->head.notfound = result->head.notfound; 519 dataset->head.timeout = timeout; 520 521 dataset->resp.version = NSCDVERSION; 522 dataset->resp.found = result->resp.found; 523 / Until we find a matching entry the result is 0. / 524 dataset->resp.result = 0; 525 526 char keycopy = memcpy ((char ) (dataset + 1), group, req->keylen);

This copies up to req->keylen material to a structure that has no storage space for it.

This was detected by static code analysis.

It will only happen in the case the database runs out of memory/storage while expanding the netgroup cache.

The group entries overwrite other data on the stack after datasetmem.

The workaround is not to cache the netgroup if this is impacting the use of the application.