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                             CERT-Renater

                 Note d'Information No. 2020/VULN661
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DATE                : 08/12/2020

HARDWARE PLATFORM(S): /

OPERATING SYSTEM(S): Systems running OpenSSL versions prior to 1.1.1i.

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https://www.openssl.org/news/secadv/20201208.txt
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OpenSSL Security Advisory [08 December 2020]
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EDIPARTYNAME NULL pointer de-reference (CVE-2020-1971)
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Severity: High

The X.509 GeneralName type is a generic type for representing different
types of names. One of those name types is known as EDIPartyName.
OpenSSL provides a function GENERAL_NAME_cmp which compares different
instances of a GENERAL_NAME to see if they are equal or not. This
function behaves incorrectly when both GENERAL_NAMEs contain an
EDIPARTYNAME. A NULL pointer dereference and a crash
may occur leading to a possible denial of service attack.

OpenSSL itself uses the GENERAL_NAME_cmp function for two purposes:
1) Comparing CRL distribution point names between an available CRL and a
   CRL distribution point embedded in an X509 certificate
2) When verifying that a timestamp response token signer matches the
   timestamp authority name (exposed via the API functions
   TS_RESP_verify_response and TS_RESP_verify_token)

If an attacker can control both items being compared then that attacker
could trigger a crash. For example if the attacker can trick a client or
server into checking a malicious certificate against a malicious CRL
then this may occur.
Note that some applications automatically download CRLs based on a URL
embedded in a certificate. This checking happens prior to the signatures
on the certificate and CRL being verified. OpenSSL's s_server, s_client
and verify tools have support for the "-crl_download" option which
implements automatic CRL downloading and this attack has been
demonstrated to work against those tools.

Note that an unrelated bug means that affected versions of OpenSSL
cannot parse or construct correct encodings of EDIPARTYNAME. However it
is possible to construct a malformed EDIPARTYNAME that OpenSSL's parser
will accept and hence trigger this attack.

All OpenSSL 1.1.1 and 1.0.2 versions are affected by this issue. Other
OpenSSL releases are out of support and have not been checked.

OpenSSL 1.1.1 users should upgrade to 1.1.1i.

OpenSSL 1.0.2 is out of support and no longer receiving public updates.
Premium support customers of OpenSSL 1.0.2 should upgrade to 1.0.2x.
Other users should upgrade to OpenSSL 1.1.1i.

This issue was reported to OpenSSL on 9th November 2020 by David
Benjamin (Google). Initial analysis was performed by David Benjamin with
additional analysis by Matt Caswell (OpenSSL). The fix was developed by
Matt Caswell.

Note
====

OpenSSL 1.0.2 is out of support and no longer receiving public updates.
Extended support is available for premium support customers:
https://www.openssl.org/support/contracts.html

OpenSSL 1.1.0 is out of support and no longer receiving updates of any
kind.
The impact of this issue on OpenSSL 1.1.0 has not been analysed.

Users of these versions should upgrade to OpenSSL 1.1.1.


References
==========

URL for this Security Advisory:
https://www.openssl.org/news/secadv/20201208.txt

Note: the online version of the advisory may be updated with additional
details over time.

For details of OpenSSL severity classifications please see:
https://www.openssl.org/policies/secpolicy.html


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+ CERT-RENATER       |    tel : 01-53-94-20-44          +
+ 23/25 Rue Daviel   |    fax : 01-53-94-20-41          +
+ 75013 Paris        |    email:cert@support.renater.fr +
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