OpenSSL Security Advisory

[Mark J Cox]

They should be releasing their paper very soon (today).

Regards, Mark

On Wed, Sep 9, 2020 at 1:45 PM Dmitry Belyavsky <beldmit at gmail.com> wrote:
>
> Is the description of the attack publicly available?
>
> On Wed, Sep 9, 2020 at 3:39 PM OpenSSL <openssl at openssl.org> wrote:
>>
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA512
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>> OpenSSL Security Advisory [09 September 2020]
>> =============================================
>>
>> Raccoon Attack (CVE-2020-1968)
>> ==============================
>>
>> Severity: Low
>>
>> The Raccoon attack exploits a flaw in the TLS specification which can lead to
>> an attacker being able to compute the pre-master secret in connections which
>> have used a Diffie-Hellman (DH) based ciphersuite. In such a case this would
>> result in the attacker being able to eavesdrop on all encrypted communications
>> sent over that TLS connection. The attack can only be exploited if an
>> implementation re-uses a DH secret across multiple TLS connections. Note that
>> this issue only impacts DH ciphersuites and not ECDH ciphersuites.
>>
>> OpenSSL 1.1.1 is not vulnerable to this issue: it never reuses a DH secret and
>> does not implement any "static" DH ciphersuites.
>>
>> OpenSSL 1.0.2f and above will only reuse a DH secret if a "static" DH
>> ciphersuite is used. These static "DH" ciphersuites are ones that start with the
>> text "DH-" (for example "DH-RSA-AES256-SHA"). The standard IANA names for these
>> ciphersuites all start with "TLS_DH_" but excludes those that start with
>> "TLS_DH_anon_".
>>
>> OpenSSL 1.0.2e and below would reuse the DH secret across multiple TLS
>> connections in server processes unless the SSL_OP_SINGLE_DH_USE option was
>> explicitly configured. Therefore all ciphersuites that use DH in servers
>> (including ephemeral DH) are vulnerable in these versions. In OpenSSL 1.0.2f
>> SSL_OP_SINGLE_DH_USE was made the default and it could not be turned off as a
>> response to CVE-2016-0701.
>>
>> Since the vulnerability lies in the TLS specification, fixing the affected
>> ciphersuites is not viable. For this reason 1.0.2w moves the affected
>> ciphersuites into the "weak-ssl-ciphers" list. Support for the
>> "weak-ssl-ciphers" is not compiled in by default. This is unlikely to cause
>> interoperability problems in most cases since use of these ciphersuites is rare.
>> Support for the "weak-ssl-ciphers" can be added back by configuring OpenSSL at
>> compile time with the "enable-weak-ssl-ciphers" option. This is not recommended.
>>
>> 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 1.0.2w.  If
>> upgrading is not viable then users of OpenSSL 1.0.2v or below should ensure
>> that affected ciphersuites are disabled through runtime configuration. Also
>> note that the affected ciphersuites are only available on the server side if a
>> DH certificate has been configured. These certificates are very rarely used and
>> for this reason this issue has been classified as LOW severity.
>>
>> This issue was found by Robert Merget, Marcus Brinkmann, Nimrod Aviram and Juraj
>> Somorovsky and reported to OpenSSL on 28th May 2020 under embargo in order to
>> allow co-ordinated disclosure with other implementations.
>>
>> 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/20200909.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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>
>
>
> --
> SY, Dmitry Belyavsky