Vulnerabilities > CVE-2022-31156 - Improper Verification of Cryptographic Signature vulnerability in Gradle
Summary
Gradle is a build tool. Dependency verification is a security feature in Gradle Build Tool that was introduced to allow validation of external dependencies either through their checksum or cryptographic signatures. In versions 6.2 through 7.4.2, there are some cases in which Gradle may skip that verification and accept a dependency that would otherwise fail the build as an untrusted external artifact. This can occur in two ways. When signature verification is disabled but the verification metadata contains entries for dependencies that only have a `gpg` element but no `checksum` element. When signature verification is enabled, the verification metadata contains entries for dependencies with a `gpg` element but there is no signature file on the remote repository. In both cases, the verification will accept the dependency, skipping signature verification and not complaining that the dependency has no checksum entry. For builds that are vulnerable, there are two risks. Gradle could download a malicious binary from a repository outside your organization due to name squatting. For those still using HTTP only and not HTTPS for downloading dependencies, the build could download a malicious library instead of the expected one. Gradle 7.5 patches this issue by making sure to run checksum verification if signature verification cannot be completed, whatever the reason. Two workarounds are available: Remove all `gpg` elements from dependency verification metadata if you disable signature validation and/or avoid adding `gpg` entries for dependencies that do not have signature files.
Vulnerable Configurations
Common Weakness Enumeration (CWE)
Common Attack Pattern Enumeration and Classification (CAPEC)
- Padding Oracle Crypto Attack An attacker is able to efficiently decrypt data without knowing the decryption key if a target system leaks data on whether or not a padding error happened while decrypting the ciphertext. A target system that leaks this type of information becomes the padding oracle and an attacker is able to make use of that oracle to efficiently decrypt data without knowing the decryption key by issuing on average 128*b calls to the padding oracle (where b is the number of bytes in the ciphertext block). In addition to performing decryption, an attacker is also able to produce valid ciphertexts (i.e., perform encryption) by using the padding oracle, all without knowing the encryption key. Any cryptosystem can be vulnerable to padding oracle attacks if the encrypted messages are not authenticated to ensure their validity prior to decryption, and then the information about padding error is leaked to the attacker. This attack technique may be used, for instance, to break CAPTCHA systems or decrypt/modify state information stored in client side objects (e.g., hidden fields or cookies). This attack technique is a side-channel attack on the cryptosystem that uses a data leak from an improperly implemented decryption routine to completely subvert the cryptosystem. The one bit of information that tells the attacker whether a padding error during decryption has occurred, in whatever form it comes, is sufficient for the attacker to break the cryptosystem. That bit of information can come in a form of an explicit error message about a padding error, a returned blank page, or even the server taking longer to respond (a timing attack). This attack can be launched cross domain where an attacker is able to use cross-domain information leaks to get the bits of information from the padding oracle from a target system / service with which the victim is communicating. To do so an attacker sends a request containing ciphertext to the target system. Due to the browser's same origin policy, the attacker is not able to see the response directly, but can use cross-domain information leak techniques to still get the information needed (i.e., information on whether or not a padding error has occurred). For instance, this can be done using "img" tag plus the onerror()/onload() events. The attacker's JavaScript can make web browsers to load an image on the target site, and know if the image is loaded or not. This is 1-bit information needed for the padding oracle attack to work: if the image is loaded, then it is valid padding, otherwise it is not.