{"id":35693,"date":"2019-10-31T22:05:48","date_gmt":"2019-10-31T19:05:48","guid":{"rendered":"https:\/\/prohoster.info\/blog\/uyazvimost-v-amd-sev-pozvolyayushhaya-opredelit-klyuchi-shifrovaniya\/"},"modified":"2019-10-31T22:05:48","modified_gmt":"2019-10-31T19:05:48","slug":"uyazvimost-v-amd-sev-pozvolyayushhaya-opredelit-klyuchi-shifrovaniya","status":"publish","type":"post","link":"https:\/\/prohoster.info\/en\/blog\/news\/uyazvimost-v-amd-sev-pozvolyayushhaya-opredelit-klyuchi-shifrovaniya","title":{"rendered":"Vulnerability in AMD SEV that allows encryption keys to be determined","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Developers from the Google Cloud team identified<\/a><\/noindex> a vulnerability (CVE-2019-9836) in the implementation of AMD SEV (Secure Encrypted Virtualization) technology, which allows compromising the data protected by this technology. AMD SEV provides hardware-level transparent encryption of virtual machine memory, where access to the decrypted data is available only to the current guest system, while other virtual machines and the hypervisor receive an encrypted set of data when trying to access this memory.<\/p>\n

The identified issue allows for the complete recovery of the contents of the closed PDH key processed at the level of a separate secure processor PSP (AMD Security Processor), which is not accessible to the main OS.
\nHaving the PDH key, an attacker can then recover the session key and the secret sequence set during the creation of the virtual machine, thus gaining access to the encrypted data. <\/p>\n

The vulnerability is caused by shortcomings in the implementation of elliptic curves (ECC) used for encryption, which allow conducting an attack<\/a><\/noindex> to recover the parameters of the curve. During the execution of the command to launch a secure virtual machine, the attacker can send curve parameters that do not comply with the parameters recommended by NIST, which will lead to the use of small-order point values in multiplication operations with the closed key data. <\/p>\n

The security of the ECDH protocol directly depends<\/a><\/noindex> from on the order<\/a><\/noindex> of the generated base point of the curve, the discrete logarithm of which is a very complex task. At one of the initialization steps of the AMD SEV environment, the calculations with the closed key use parameters obtained from the user. Essentially, an operation is performed to multiply two points, one of which corresponds to the closed key. If the second point corresponds to low-order prime numbers, the attacker can determine the parameters of the first point (the bits of the modulus used in the exponentiation operation) by brute-forcing through all possible values. To determine the closed key, the selected fragments of prime numbers can then be assembled together using the Chinese Remainder Theorem<\/a><\/noindex>.<\/p>\n

The issue affects AMD EPYC server platforms using SEV firmware up to version 0.17 build 11. AMD has already released<\/noindex> A firmware update has been released, which includes a block on the use of points that do not conform to the NIST curve. Previously generated certificates for PDH keys remain valid, allowing an attacker to carry out a migration attack from environments protected against the vulnerability to those exposed to the issue. The possibility of reverting the firmware version to an older vulnerable release is also mentioned, but this has not yet been confirmed.<\/p>\n

<\/a><\/noindex><\/p>\n

Source: opennet.ru<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

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