| Description: | The BN_mod_sqrt() function, which computes a modular square root,
contains a bug that can cause it to loop forever for non-prime moduli.
Internally this function is used when parsing certificates that
contain elliptic curve public keys in compressed form or explicit
elliptic curve parameters with a base point encoded in compressed
form. It is possible to trigger the infinite loop by crafting a
certificate that has invalid explicit curve parameters. Since
certificate parsing happens prior to verification of the certificate
signature, any process that parses an externally supplied certificate
may thus be subject to a denial of service attack. The infinite loop
can also be reached when parsing crafted private keys as they can
contain explicit elliptic curve parameters. Thus vulnerable situations
include: - TLS clients consuming server certificates - TLS servers
consuming client certificates - Hosting providers taking certificates
or private keys from customers - Certificate authorities parsing
certification requests from subscribers - Anything else which parses
ASN.1 elliptic curve parameters Also any other applications that use
the BN_mod_sqrt() where the attacker can control the parameter values
are vulnerable to this DoS issue. In the OpenSSL 1.0.2 version the
public key is not parsed during initial parsing of the certificate
which makes it slightly harder to trigger the infinite loop. However
any operation which requires the public key from the certificate will
trigger the infinite loop. In particular the attacker can use a self-
signed certificate to trigger the loop during verification of the
certificate signature. This issue affects OpenSSL versions 1.0.2,
1.1.1 and 3.0. It was addressed in the releases of 1.1.1n and 3.0.2 on
the 15th March 2022. Fixed in OpenSSL 3.0.2 (Affected 3.0.0,3.0.1).
Fixed in OpenSSL 1.1.1n (Affected 1.1.1-1.1.1m). Fixed in OpenSSL
1.0.2zd (Affected 1.0.2-1.0.2zc).
|
