Amazon has fixed a cryptographic hole in its EC2 and S3 services that could allow hackers to hijack 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 in a paper (pdf).
"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 vulnerabilities in control interfaces that were vulnerable to new and known XML signature wrapping attacks.
They had 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.
Researchers also discovered that since the Amazon shop and EC2 and S3 shared the same log-in credentials, XSS attacks launched against the complex and therefore more vulnerable shop also worked against EC2 and S3.
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 at the US-based ACM Cloud Computing Security Workshop 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 Professor 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 service 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".
The university cited “industry estimates’ that European cloud services will more than double from 68 billion euros last year to 148 billion in 2014.