[ASA-201804-2] openssl: multiple issues

[Santiago Torres-Arias]

Arch Linux Security Advisory ASA-201804-2
=========================================

Severity: Medium
Date    : 2018-04-01
CVE-ID  : CVE-2017-3738 CVE-2018-0739
Package : openssl
Type    : multiple issues
Remote  : Yes
Link    : https://security.archlinux.org/AVG-540

Summary
=======

The package openssl before version 1.1.0.h-1 is vulnerable to multiple
issues including denial of service and private key recovery.

Resolution
==========

Upgrade to 1.1.0.h-1.

# pacman -Syu "openssl>=1.1.0.h-1"

The problems have been fixed upstream in version 1.1.0.h.

Workaround
==========

None.

Description
===========

- CVE-2017-3738 (private key recovery)

There is an overflow bug in the AVX2 Montgomery multiplication
procedure used in exponentiation with 1024-bit moduli. No EC algorithms
are affected. Analysis suggests that attacks against RSA and DSA as a
result of this defect would be very difficult to perform and are not
believed likely. Attacks against DH1024 are considered just feasible,
because most of the work necessary to deduce information about a
private key may be performed offline. The amount of resources required
for such an attack would be significant. However, for an attack on TLS
to be meaningful, the server would have to share the DH1024 private key
among multiple clients, which is no longer an option since
CVE-2016-0701.

- CVE-2018-0739 (denial of service)

A stack-exhaustion issue has been found in OpenSSL <= 1.1.0h, where
constructed ASN.1 types with a recursive definition (such as can be
found in PKCS7) could eventually exceed the stack given malicious input
with excessive recursion. This could result in a Denial Of Service
attack. There are no such structures used within SSL/TLS that come from
untrusted sources so this is considered safe.

Impact
======

A remote attacker might be able to recover a private key (in very
unlikely cases), or cause a denial of service by providing a crafted
ASN.1 type to a vulnerable application.

References
==========

https://www.openssl.org/news/vulnerabilities.html#2017-3738
https://www.openssl.org/news/secadv/20171207.txt
https://github.com/openssl/openssl/commit/5630661aecbea5fe3c4740f5fea744a1f07a6253
https://www.openssl.org/news/secadv/20180327.txt
https://github.com/openssl/openssl/commit/2ac4c6f7b2b2af20c0e2b0ba05367e454cd11b33
https://security.archlinux.org/CVE-2017-3738
https://security.archlinux.org/CVE-2018-0739
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