Summary Two vulnerabilities have been found in Rekor types for archive files JARs and APKs, where Rekor would crash due to out of memory conditions caused by reading archive metadata files into memory without checking their sizes first causing a Denial of Service of Rekor.
These vulnerabilities were found through fuzzing with OSS-Fuzz.
Vulnerability 1: OOM due to large files in META-INF directory of JAR files. Summary Verification of a JAR file submitted to Rekor can cause an out of memory crash if files within the META-INF directory of the JAR are sufficiently large.
Details As part of verifying a JAR file, Rekor uses the relic library to check that the JAR is signed, the signature verifies, and that the hashes in the signed manifest are all valid. This library function reads files within META-INF/ into memory without checking their sizes, resulting in an OOM if the uncompressed file is sufficiently large. Rekor is also not performing any such checks prior to passing the JAR to this library function.
Patches Users should update to the latest version of Rekor, 1.1.1.
Workaround There are no workarounds, users should update.
Vulnerability 2: OOM due to large .SIGN and .PKGINFO files in APK files. Summary Parsing of an APK file submitted to Rekor can cause an out of memory crash if the .SIGN or .PKGINFO files within the APK are sufficiently large.
Details When parsing an APK file, Rekor allocates byte slices to read both the .SIGN and .PKGINFO files into memory in order to verify the signature and hashes in the APK. These byte slices are allocated based on the size included in the tar header for each file, with no checks performed on that size. If the size in the header is sufficiently large, either because the uncompressed file is large or the size in the header has been artificially set to a large value, Rekor will crash due to an out of memory panic.
Patches Users should update to the latest version of Rekor, 1.1.1.
Workaround There are no workarounds, users should update.
Summary
/api/v1/index/retrieve supports retrieving a public key via a user-provided URL, allowing attackers to trigger SSRF to arbitrary internal services.
Since the SSRF only can trigger GET requests, the request cannot mutate state. The response from the GET request is not returned to the caller so data exfiltration is not possible. A malicious actor could attempt to probe an internal network through Blind SSRF.
Impact
SSRF to cloud metadata (169.254.169.254) SSRF to internal Kubernetes APIs SSRF to any service accessible from Fulcio's network
Patches
Upgrade to v1.5.0. Note that this is a breaking change to the search API and fully disables lookups by URL. If you require this feature, please reach out and we can discuss alternatives.
Workarounds
Disable the search endpoint with --enableretrieveapi=false.
Summary
Rekor’s cose v0.0.1 entry implementation can panic on attacker-controlled input when canonicalizing a proposed entry with an empty spec.message. validate() returns nil (success) when message is empty, leaving sign1Msg uninitialized, and Canonicalize() later dereferences v.sign1Msg.Payload.
Impact
A malformed proposed entry of the cose/v0.0.1 type can cause a panic on a thread within the Rekor process. The thread is recovered so the client receives a 500 error message and service still continues, so the availability impact of this is minimal.
Patches
Upgrade to v1.5.0
Workarounds
None
Impact A malformed proposed entry of the intoto/v0.0.2 type can cause a panic on a thread within the Rekor process. The thread is recovered so the client receives a 500 error message and service still continues, so the availability impact of this is minimal.
Patches This is fixed in v1.2.0 of Rekor.
Workarounds No
References Discovered by OSS-Fuzz