Public bug reported:
"BN_cmp() returns -1 if a < b, 0 if a == b and 1 if a > b." (
https://wiki.openssl.org/index.php/Manual:BN_cmp(3) )
The libcrypto.a shipped with Ubuntu makes a distinction between a
negative 0 ("-0") and a positive zero ("0"). This means that BN_cmp(-0,
0) returns -1 and BN_cmp(0, -0) returns 1. The latest versions of
OpenSSL (1.0.2m and 1.1.0g) both return 0 for both comparisons, which is
what you would expect.
lsb_release -rd:
Description: Ubuntu 16.04.3 LTS
Release: 16.04
Tested on both the 32 bit and 64 bit versions of this Ubuntu release.
Attached is a proof of concept.
The anomaly may also be caused by BN_dec2bn rather than BN_cmp.
The bug is unlikely to have direct security consequences, but may cause
unexpected behaviour in other applications that depend on this
widespread library.
Found with https://github.com/guidovranken/bignum-fuzzer
** Affects: openssl (Ubuntu)
Importance: Undecided
Status: New
** Attachment added: "proof of concept of the bug"
https://bugs.launchpad.net/bugs/1734447/+attachment/5014408/+files/osslcmp.c
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https://bugs.launchpad.net/bugs/1734447
Title:
BN_cmp regards negative and positive zero as different numbers
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