Bug 1271165

Summary:	m2crypto: pbkdf2 function crashes when given 74 byte result as argument
Product:	[Other] Security Response	Reporter:	Adam Mariš <amaris>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED CURRENTRELEASE	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	abaron, aortega, apevec, ayoung, bkearney, cbillett, chrisw, dallan, gholms, gkotton, gmollett, jmatthew, jrusnack, jschluet, katello-bugs, kseifried, lhh, lpeer, markmc, mcepl, mitr, rbryant, rhos-maint, sclewis, tdecacqu, tomckay, tsanders, yeylon
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2015-11-30 19:11:29 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	1276630
Bug Blocks:	1271166

Description Adam Mariš 2015-10-13 10:03:05 UTC

A bug was found in pbkdf2 function of m2crypto package, such that when given a 74 byte result, a buffer overflow occurs leading to crash of the application.

For reproducer and backtrace, see product bug:

https://bugzilla.redhat.com/show_bug.cgi?id=1270318

Comment 1 Stefan Cornelius 2015-10-29 16:52:31 UTC

The root cause is a stack-based buffer overflow in the pkcs5_pbkdf2_hmac_sha1() function in SWIG/_evp.i 

It defines the following stack-based buffer:
 unsigned char key[EVP_MAX_KEY_LENGTH];   // usually 64byte

and later calls this function, which takes in "keylen" and fills "key". if "keylen" is larger than EVP_MAX_KEY_LENGTH, it overflows the stack-based buffer.

    PKCS5_PBKDF2_HMAC_SHA1(passbuf, passlen, saltbuf, saltlen, iter,
                           keylen, key);

A simple sanity check of keylen (both that it's not larger than EVP_MAX_KEY_LENGTH and not negative) before calling PKCS5_PBKDF2_HMAC_SHA1 should be enough to prevent this. This function should be protected by stack canaries, so code execution is mitigated, but there may be a minimal remaining risk that it's still possible.

Comment 2 Stefan Cornelius 2015-10-30 10:13:41 UTC

*** Bug 1270318 has been marked as a duplicate of this bug. ***

Comment 3 Stefan Cornelius 2015-10-30 10:35:11 UTC

Created m2crypto tracking bugs for this issue:

Affects: fedora-all [bug 1276630]

Comment 4 Miloslav Trmač 2015-11-02 20:28:11 UTC

https://gitlab.com/m2crypto/m2crypto/merge_requests/8

Comment 5 Fedora Update System 2015-11-19 09:59:47 UTC

m2crypto-0.22.5-2.fc23 has been pushed to the Fedora 23 stable repository. If problems still persist, please make note of it in this bug report.

Comment 6 Fedora Update System 2015-11-19 12:22:41 UTC

m2crypto-0.22.5-2.fc22 has been pushed to the Fedora 22 stable repository. If problems still persist, please make note of it in this bug report.

Comment 7 Fedora Update System 2015-11-20 23:24:17 UTC

m2crypto-0.22.5-2.fc21 has been pushed to the Fedora 21 stable repository. If problems still persist, please make note of it in this bug report.

Comment 8 Matěj Cepl 2015-11-30 19:11:29 UTC

This has been fixed, right?