ASA-2019-00649 – OpenSSL: Overflow bug in the x86_64 Montgomery squaring procedure

Posted on by Allele Security Intelligence in Alerts

Allele Security Alert

ASA-2019-00649

Identifier(s)

ASA-2019-00649, CVE-2019-1551

Title

Overflow bug in the x86_64 Montgomery squaring procedure

Vendor(s)

The OpenSSL Project

Product(s)

OpenSSL

Affected version(s)

OpenSSL version 1.1.1
OpenSSL version 1.0.2

Fixed version(s)

OpenSSL version 1.1.1 with the following commit:

Fix an overflow bug in rsaz_512_sqr
https://github.com/openssl/openssl/commit/419102400a2811582a7a3d4a4e317d72e5ce0a8f

OpenSSL version 1.0.2 with the following commit:

Fix an overflow bug in rsaz_512_sqr
https://github.com/openssl/openssl/commit/f1c5eea8a817075d31e43f5876993c6710238c98

Proof of concept

Unknown

Description

There is an overflow bug in the x86_64 Montgomery squaring procedure used in exponentiation with 512-bit moduli. No EC algorithms are affected. Analysis suggests that attacks against 2-prime RSA1024, 3-prime RSA1536, and DSA1024 as a result of this defect would be very difficult to perform and are not believed likely. Attacks against DH512 are considered just feasible. However, for an attack the target would have to re-use the DH512 private key, which is not recommended anyway. Also applications directly using the low level API BN_mod_exp may be affected if they use BN_FLG_CONSTTIME.

Technical details

Unknown

Credits

Guido Vranken

Reference(s)

rsaz_512_sqr overflow bug on x86_64 (CVE-2019-1551)
https://mta.openssl.org/pipermail/openssl-announce/2019-December/000163.html

rsaz_512_sqr overflow bug on x86_64 (CVE-2019-1551)
https://www.openssl.org/news/secadv/20191206.txt

Fix an overflow bug in rsaz_512_sqr
https://github.com/openssl/openssl/commit/419102400a2811582a7a3d4a4e317d72e5ce0a8f

Fix an overflow bug in rsaz_512_sqr
https://github.com/openssl/openssl/commit/f1c5eea8a817075d31e43f5876993c6710238c98

Fix rsaz 512 overflow bug [1.1.1] #10575
https://github.com/openssl/openssl/pull/10575

Fix rsaz 512 overflow bug [1.0.2] #10576
https://github.com/openssl/openssl/pull/10576

CVE-2019-1551 in Ubuntu
https://people.canonical.com/~ubuntu-security/cve/CVE-2019-1551.html

CVE-2019-1551
https://security-tracker.debian.org/tracker/CVE-2019-1551

CVE-2019-1551
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-1551

CVE-2019-1551
https://nvd.nist.gov/vuln/detail/CVE-2019-1551

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Last modified: December 6, 2019

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