Um estudante de PHD de Singapura, Wang Jing, identificou a falha, chamada de “Covert Redirect”, que consegue usar domínios reais de sites para verificação de páginas de login falsas, enganando os internautas.
Os cibercriminosos podem criar links maliciosos para abrir janelas pop-up do Facebook pedindo que o tal aplicativo seja autorizado. Caso seja realizada esta sincronização, os dados pessoais dos usuários serão passados para os hackers.
Wang afirma que já entrou em contato com o Facebook, porém recebeu uma resposta de que “entende os riscos de estar associado ao OAuth 2.0″ e que corrigir a falha “é algo que não pode ser feito por enquanto”.
O Google afirmou que o problema está sendo rastreado, o LinkedIn publicou nota em que garante que já tomou medidas para evitar que a falha seja explorada, e a Microsoft negou que houvesse vulnerabilidade em suas páginas, apenas nas de terceiros.
A recomendação do descobridor da falha para os internautas é que evitem fazer o login com dados de confirmação de Facebook, Google ou qualquer outro serviço sem terem total certeza de que estão em um ambiente seguro.
Especialistas: erro é difícil de corrigir
O site CNET ouviu dois especialistas em segurança virtual sobre o assunto. Segundo Jeremiah Grossman, fundador e CEO interino da WhiteHat Security, afirma que a falha “não é fácil de corrigir”. Segundo Chris Wysopal, diretor da Veracode, a falha pode enganar muita gente.
“A confiança que os usuários dão ao Facebook e outros serviços que usam OAuth pode tornar mais fácil para os hackers enganarem as pessoas para que elas acabem dando suas informações pessoais a ele”, afirma Wsyopal.
Following in the steps of the OpenSSL vulnerability Heartbleed, A serious Covert Redirect vulnerability related to OAuth 2.0 and OpenID has been found. Almost all major providers of OAuth 2.0 and OpenID are affected, such as Facebook, Google, Yahoo, LinkedIn, Microsoft, Paypal, GitHub, QQ, Taobao, Weibo, VK, Mail.Ru, Sohu, etc.
Wang Jing, a Ph.D. student at the Nanyang Technological University in Singapore, discovered that the serious vulnerability “Covert Redirect” flaw can masquerade as a log-in popup based on an affected site’s domain. Covert Redirect is based on a well-known exploit parameter.
For example, someone clicking on a malicious phishing link will get a popup window in Facebook, asking them to authorize the app. Instead of using a fake domain name that’s similar to trick users, the Covert Redirect flaw uses the real site address for authentication.
If a user chooses to authorize the log in, personal data (depending on what is being asked for) will be released to the attacker instead of to the legitimate website. This can range from email addresses, birth dates, contact lists, and possibly even control of the account.
Regardless of whether the victim chooses to authorize the app, he or she will then get redirected to a website of the attacker’s choice, which could potentially further compromise the victim.
Wang says he has already contacted Facebook and has reported the flaw, but was told that the company “understood the risks associated with OAuth 2.0,” and that “short of forcing every single application on the platform to use a whitelist,” fixing this bug was “something that can’t be accomplished in the short term.”
Facebook isn’t the only site affected. Wang says he has reported this to Google, LinkedIn, and Microsoft, which gave him various responses on how they would handle the matter.
Google (which uses OpenID) told him that the problem was being tracked, while LinkedIn said that the company has published a blog on the matter. Microsoft, on the other hand, said an investigation had been done and that the vulnerability existed on the domain of a third party and not on its own sites.
“Patching this vulnerability is easier said than done. If all the third-party applications strictly adhere to using a whitelist, then there would be no room for attacks,” said Wang.
“However, in the real world, a large number of third-party applications do not do this due to various reasons. This makes the systems based on OAuth 2.0 or OpenID highly vulnerable,” he added.
LinkedIn engineer Shikha Sehgal wrote a blog post about the creation of a whitelist for the site more than a month before Wang published his findings.
“In order to make the LinkedIn platform even more secure, and so we can comply with the security specifications of OAuth 2, we are asking those of you who use OAuth 2 to register your application’s redirect URLs with us by April 11, 2014,” she said.
Sehgal did not explicitly say that the measure was in response to a flaw in OAuth 2, but the social network did confirm to CNET that the vulnerability that Wang detailed is the same one that inspired the blog post.
PayPal also has addressed the flaw.
“When PayPal implemented OAuth2.0/OpenID, we engineered additional security measures to protect our merchants and customers. These measures protect PayPal customers from this specific OAuth2.0/OpenID vulnerability,” James Barrese, PayPal’s CTO, said in a blog post on Friday. PayPal declined to add details about those measures.