unauthenticated path traversal in Metacat 2.x

Summary

Metacat is data repository software that helps researchers preserve, share, and discover data. Versions 2.x through 2.19.1 and all 1.x versions contain an unauthenticated path traversal in the `archiveEntryName` parameter of the `action=read` endpoint that is part of the original 1.x Metacat API. `ArchiveHandler.readArchiveEntry()` concatenates the user-supplied parameter into a filesystem path without validation, and the surrounding `hasReadPermission()` check is commented out. An unauthenticated remote attacker can read any file accessible to the Tomcat process by sending a single GET request. Proof-of-concept exploits have been demonstrated and verified against this vulnerability, and it should be considered easily exploitable for any Metacat deployment < 3.0.0 by any user with access to the 1.x API. Through this vulnerability, production 2.x deployments are exposed to credential theft, client certificate and private key exfiltration enabling member node impersonation within the federation, embargoed research data disclosure, and broad system reconnaissance. Given Metacat's deployment footprint across the DataONE network of repositories and federally funded research programs, the population of exposed 2.x instances is non-trivial. The vulnerability was eliminated in Metacat version 3.0.0 and after by eliminating the entire Metacat 1.x API that exposed this vulnerability. The vulnerability was remediated in April 2024 with the release of Metacat 3.0.0, which removed the legacy Metacat API including ArchiveHandler.java. The commit message and issue reference architectural cleanup, not a security fix, and no advisory or CVE was issued. The 2.x branch was not and will not be backported, as is standard practice in Metacat, which only supports the most current release. 2.19.1 remains vulnerable with identical code and is beyond its supported lifetime. As a workaround, disable or restrict 1.x API servlets. Because the vulnerable 1.x API is no longer used or necessary in most Metacat deployments, restricting access to the old API endpoints can reduce or eliminate exposure for 2.19.x deployments. After removing those features, restart Tomcat or whichever software is hosting the servlets.