Resultados 1 a 2 de 2
  1. #1
    WHT-BR Top Member
    Data de Ingresso
    Dec 2010
    Posts
    14,981

    [EN] Heartbleed: 80,000 certificates revoked

    As of this morning (Tuesday 15th April), more than 80,000 certificates have been revoked since the public announcement of the vulnerability on 7th April.

    500,000+ certificates used on web servers supporting TLS heartbeat should be urgently replaced and revoked.



    Based on list prices, the cost of replacing all of the potentially-compromised certificates with completely new certificates is more than $100 million, but, helpfully, most (but not all) certificate authorities are allowing their customers to reissue and revoke certificates for free. Nonetheless, plenty of the affected websites (e.g. Etsy, Yahoo, GitHub, Steam) appear to have bought new certificates instead of going through the reissuance process, as the new expiry dates are significantly later than the expiry dates in the previous certificates. Perhaps in the haste of resolving the problem, this seemed the easiest approach, making Heartbleed a bonanza for certificate authorities.

    While some companies quickly recognised the need to issue new certificates in response to the Heartbleed bug, the number of revocations has not kept up. This is a mistake, as there is little point issuing a new certificate if an attacker is still able to impersonate a website with the old one.

    Yahoo was one of the first companies to deploy new SSL certificates after the Heartbleed bug became public knowledge, but the certificate that was previously used by mlogin.yahoo.com has not yet been revoked — it has not been placed on a CRL, and the certificate's OCSP responder says the certificate is "good".

    Yahoo is not the only company to have issued a new certificate without ensuring that the previously vulnerable certificate has been revoked. Other sites which fall into this category include banking websites (such as entry7.credit-suisse.ch), the United States Senate large file transfer system at lfts.senate.gov, and GeoTrust's SSL Toolbox at https://ssltools.geotrust.com/checker/ (GeoTrust is a brand owned by Symantec, the largest certificate authority).

    Thousands of certificates could still be misused after being revoked

    Critically, some of the certificates affected by the Heartbleed bug will remain usable even if revoked: Nearly 4% of the certificates do not specify a URL for an OCSP responder, which means that they can only be revoked via a CRL. This makes the certificates effectively irrevocable in some browsers — for example, the latest version of Mozilla Firefox no longer uses CRLs at all (previously it would fall back to checking a CRL if an OCSP request failed, but only for Extended Validation certificates).

    Worse still, a small number of the certificates that could have been compromised through exploitation of the Heartbleed bug fail to specify either an OCSP or a CRL address. These certificates are therefore completely irrevocable in all browsers and could be impersonated until their natural expiry dates if an attacker has already compromised the private keys.

    For example, Telecom Italia (a sub-CA of Verizon Business) is still using an irrevocable certificate on www.cloudpeople.it, which supported the TLS heartbeat extension prior to the disclosure of the Heartbleed bug. The 3-year certificate was issued by I.T. Telecom Global CA at the end of 2011 and will remain valid until the end of 2014 because it does permit either form of revocation.

    CRLs will balloon as a result of the surge of revocations

    To obtain the certificate revocation lists (CRLs) used by each publicly trusted certificate authority, a web browser would need to download more than 100MB of data. These CRLs will grow by about 35% if all of the certificates affected by the Heartbleed bug were revoked. Downloading this much data is clearly impractical for many mobile devices, and several CRLs either time-out or take more than a minute to download, even from a desktop machine with a fast internet connection. This goes against the CA/Browser Forum's Baseline Requirements, which expect CAs to provide response times of less than 10 seconds.

    The largest CRL (11MB) is operated by the US Department of the Treasury, and despite containing more than 200,000 revocation entries, it is only used by one publicly accessible certificate. Nonetheless, any browser wishing to perform a CRL check for that one site will have to download the whole list. Governments also feature amongst the worst-performing CRLs: For example, the Taiwanese government offers a CRL at http://hcaocsp.nat.gov.tw/repository...L/complete.crl, which would not respond when tested earlier today, and the Brazilian government offers several CRLs from its site at repositorio.icpbrasil.gov.br, but each took 2-3 minutes to download, despite being of relatively modest sizes.

    http://news.netcraft.com/archives/20...e-is-nigh.html
    Última edição por 5ms; 15-04-2014 às 21:11.

  2. #2
    WHT-BR Top Member
    Data de Ingresso
    Dec 2010
    Posts
    14,981

    If you don't revoke your certificate, you may still be vulnerable to impersonation

    If your private key has been stolen, just reissuing the certificate is not enough to mitigate the risks posed by the Heartbleed bug. Websites which were affected by the bug could still be vulnerable to impersonation attacks in the future if they fail to revoke their certificates, even if they have upgraded to the latest version of OpenSSL and replaced their SSL certificates.

    If a remote attacker successfully retrieved private keys from a server while it was still vulnerable to the Heartbleed bug, then he would be able to impersonate the server by creating his own valid SSL certificate. The crucial issue is that an attacker can still do this after the affected website has upgraded to the latest version of OpenSSL, and it does not matter whether the real website has since deployed a new SSL certificate with different keys: Unless the previous certificate is revoked, the site will still be vulnerable to man-in-the-middle attacks.

    Despite the importance of revoking certificates which could have been stolen using the Heartbleed bug, many website administrators and certificate authorities have yet to do this.

    ...

    Certificate authorities must revoke certificates within 24 hours if there is evidence of a key compromise. A private key is said to be compromised if its value has been disclosed, or if there exists a practical technique by which an unauthorised person may discover its value. Arguably, all certificates on sites vulnerable to the Heartbleed bug should be revoked by now, as such a technique was successfully carried out by the researchers behind heartbleed.com.
    Even if you revoke your certificate, you may still be vulnerable to impersonation

    However, even if all of the affected certificates were to be revoked, contemporary web browser software handles certificate revocation poorly. The most frequent users of a site — often its administrators — can continue using a revoked certificate for weeks or months without the browser notifying them that anything is amiss. In this situation, an attacker can perform a man-in-the-middle (MITM) attack by presenting the certificate to unsuspecting users whose browsers will behave as if they were connecting to the legitimate site. For example, some browsers only perform OCSP revocation checks for Extended Validation certificates, while others ignore certificate revocation lists completely.
    http://news.netcraft.com/archives/20...to-arrive.html

Permissões de Postagem

  • Você não pode iniciar novos tópicos
  • Você não pode enviar respostas
  • Você não pode enviar anexos
  • Você não pode editar suas mensagens
  •