CVE-2022-26850

### Impact `org.apache.nifi.authentication.single.user.writer.StandardLoginCredentialsWriter` contains a local information disclosure vulnerability due to writing credentials (username and password) to a file that is readable by all other users on unix-like systems. On unix-like systems, the system's temporary directory is shared between all users on that system. As such, files written to that directory without setting the correct file permissions can allow other users on that system to view the contents of the files written to those temporary files. ### Source An insecure temporary file is created here: - https://github.com/apache/nifi/blob/6a1c7c72d5b91b9ce5d5cb5b86e3155d21e2c19b/nifi-commons/nifi-single-user-utils/src/main/java/org/apache/nifi/authentication/single/user/writer/StandardLoginCredentialsWriter.java#L75 The username and password credentials are written to this file here: - https://github.com/apache/nifi/blob/6a1c7c72d5b91b9ce5d5cb5b86e3155d21e2c19b/nifi-commons/nifi-single-user-utils/src/main/java/org/apache/nifi/authentication/single/user/writer/StandardLoginCredentialsWriter.java#L85-L95 ### Patches The vulnerability has been patched in version `1.16`. ### Prerequisites This vulnerability impacts Unix-like systems, and very old versions of Mac OSX and Windows as they all share the system temporary directory between all users. ### Workarounds Setting the `java.io.tmpdir` system environment variable to a directory that is exclusively owned by the executing user will fix this vulnerability for all operating systems. ### References - https://issues.apache.org/jira/browse/NIFI-9785 - https://github.com/apache/nifi/commit/859d5fe - https://github.com/apache/nifi/pull/5856 - https://nifi.apache.org/security.html#CVE-2022-26850 - https://twitter.com/JLLeitschuh/status/1511736635645435904?s=20&t=I3w3zF6Y2DUvWYsEFqERjg

When creating or updating credentials for single-user access, Apache NiFi wrote a copy of the Login Identity Providers configuration to the operating system temporary directory. On most platforms, the operating system temporary directory has global read permissions. NiFi immediately moved the temporary file to the final configuration directory, which significantly limited the window of opportunity for access. NiFi 1.16.0 includes updates to replace the Login Identity Providers configuration without writing a file to the operating system temporary directory.