Amazon has fixed a cryptographic hole in its Elastic Compute Cloud (EC 2) and Simple Storage Service (S 3) services that could allow hackers to compromise customer accounts.
The signature-wrapping and cross-site scripting (XSS) attacks hijacked control interfaces used to manage cloud computing resources, which allowed attackers to create, modify. and delete machine images, and change administrative passwords and settings.
“Effectively, a successful attack on a cloud control interface grants the attacker a complete power over the victim's account, with all the stored data included,” researchers at Germany's Ruhr University wrote (PDF) in a paper.
"We had full access to all customer data, including data authentication, tokens, and even passwords in clear text," researcher Mario Heiderich said.
In one attack, researchers discovered weaknesses in control interfaces that opened them up to new and known XML signature-wrapping attacks.
They generated arbitrary SOAP messages, which were accepted by the control interface because application signature verification and XML interpretation were handled separately.
Full compromise required knowledge of a signed SOAP message, while a single arbitrary cloud control operation could be executed with knowledge of a public X.509 certificate.
"This attack was made possible by the simple fact the Amazon shop and the Amazon cloud control interfaces share the same login credentials, thus any XSS attack on the (necessarily complex) shop interface can be turned into an XSS attack on the cloud control interface," the researchers wrote.
Similar injection attacks also worked against the Eucalyptus cloud computer software.
Amazon confirmed the attacks and closed the security holes prior to disclosure, according to professor Jörg Schwenk, chair of network and data security at the university.
The vulnerabilities were detailed last week at the U.S.-based ACM Cloud Computing Security Workshop in Chicago, and first reported by H-Security.
"A major challenge for cloud providers is that of the data entrusted to them, only the client should be accessible," said Pan. who led the team which discovered the holes.
Researcher Juraj Somorovsky said security issues such as the ones detailed in cloud computing must be assessed as the technology become more popular.
"Critical infrastructure and services are making ever more use of cloud computing," he said. "It is therefore an urgent need to identify the security gaps in cloud computing."