RSA-1024 Private Key Extraction Made Possible

A collaboration of security researchers have discovered a vulnerability in the Libgcrypt module of GnuGP that could allow a threat actor to recover the private key.

Threat ID:: CC-1514
Category:: Exploit
Threat Severity:: Medium
Threat Vector:
Published:: 11 July 2017 12:00 AM

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Summary

A collaboration of security researchers have discovered a vulnerability in the Libgcrypt module of GnuGP that could allow a threat actor to recover the private key.

Threat details

This type of attack is likely to be used by APT groups as part of the exfiltration phase of an attack where the goal is to collect data such as an organisation's intellectual property.

GnuGP is a widely used free implementation of the OpenPGP standard and is used to encrypt and sign data and communications securely. Libgcrypt is a module that is found inside the GnuGP package providing the encryption functionality.

Researchers investigating the operation of Libgcrypt found that it implemented a method known as sliding windows to perform certain mathematical computations required as part of the encryption process. The issue arises as the technique is known to be vulnerable to an attack known as a side-channel attack.

Side-channel attacks are a type of attack where data can leak from the operation and be accessed from another data source which can be obtained without brute forcing or through a direct weakness in the algorithm being attacked.

These alternate data sources can vary but examples include timing of certain operations, power consumptions at different stages, leaking of electromagnetic signals among others. In this instance, it has been found that a flush+reload cache-timing attack allows an actor to monitor the target's cache and record certain access patterns allowing data to be leaked. This can be used against Libgcrypt to aid in retrieving the private key.

Updated packages have now been released for all major distributions and can be obtained from the relevant package managers.

Remediation steps

Type	Step
	Ensure libgcrypt20 is updated at the earliest opportunity where in use. Where data is highly sensitive, stronger encryptions should be considered. Ensure a multi-layered approach is taken with regards to security solutions such as host and network based intrusion detection mechanisms put in place to detect an attack against systems as well as indicators that may indicate an exfiltration attempt from a system within the network.

Type

Step

Ensure libgcrypt20 is updated at the earliest opportunity where in use.
Where data is highly sensitive, stronger encryptions should be considered.
Ensure a multi-layered approach is taken with regards to security solutions such as host and network based intrusion detection mechanisms put in place to detect an attack against systems as well as indicators that may indicate an exfiltration attempt from a system within the network.

Last edited: 17 February 2020 11:38 am