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TEZ-4699:Add Validation/Canonical checks to avoid path exploitation in CSVResult.java - #471
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abstractdog
commented
Mar 26, 2026
thanks @ramitg254 for this patch, can you please elaborate on how the patch solved this problem? before/after behaviour would be nice to see |
tez-yetus
commented
Mar 26, 2026
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sure @abstractdog before: after: similarly the other preventive check ensures the output directory should exist: before: after: in the similar fashion other preventive checks works before opening stream for file writes as well |
tez-yetus
commented
Mar 26, 2026
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tez-yetus
commented
Mar 27, 2026
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| // check if the parent directory is writable | ||
| if (!parent.canWrite()) { | ||
| throw new IOException("No write permission on directory: " + parent); | ||
| } | ||
| return target; |
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Should we check this separately? If the directory isn’t writable by the user, the write will fail anyway, right?
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this was added for more descriptive exception, but it can be dropped as AccessDeniedException will take care of it. done.
| if (record.length != headers.length) { | ||
| continue; //LOG error msg? | ||
| } | ||
| private static File validateOutputFile(String fileName) throws IOException { |
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nit class formatting: private method ideally goes below the public one
| continue; //LOG error msg? | ||
| } | ||
| private static File validateOutputFile(String fileName) throws IOException { | ||
| //null or empty string check |
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the corresponding code is too obvious, we don't need this comment
| File target = new File(fileName).getCanonicalFile(); | ||
| File parent = target.getParentFile(); | ||
| // check if the parent directory exists |
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the corresponding code is too obvious, we don't need this comment
| throw new IllegalArgumentException("fileName must not be null or empty"); | ||
| } | ||
| // resolve relative path |
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the corresponding code is too obvious, we don't need this comment
| Path targetPath = target.toPath(); | ||
| try (BufferedWriter bw = new BufferedWriter( | ||
| // atomically create new file if it doesn't exist, and if exists, throw an exception |
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this comment doesn't add more value then looking at the javadoc of Files.newOutputStream, we can remove it I think
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thanks @ramitg254, left minor comments
also, can you please add simple unit test cases for what you implemented in validateOutputFile?
1 more thing to check: I think a path like |
done added |
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ramitg254
commented
Mar 27, 2026
I think it will be fine as it will be resolved to valid path by getCanonicalFile() before checks are run on it |
| result.dumpToFile(out.toString()); | ||
| Assert.fail("Expected FileAlreadyExistsException when output file already exists"); | ||
| } catch (FileAlreadyExistsException e) { | ||
| // CREATE_NEW must fail if path already exists (atomic exclusive create) |
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add an extra assertion here for clarity on exception message
abstractdog
commented
Mar 27, 2026
yeah, it might be the case, but it should be validated with a unit test case also |
ramitg254
commented
Mar 27, 2026
done added |
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tez-yetus
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Mar 30, 2026
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| } | ||
| @Test | ||
| public void testDumpToFileNoWritePermissionRelativePath() throws Exception { |
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I think this unit test mixes 2 different scenarios, which should be thought of separately:
- whether the user is able to define relative paths with
.. - whether the user can write to a folder without permissions
2) is clear, and I'm not even insisting on having a test case on that, because it's testing permission handling instead of any of the actual logic you just implemented, right? no matter how you implement validateOutputFile, this is going to pass always, so it doesn't add much value
regarding 1), it's more of a decision whether we want the user to be able to move upwards in the directory structure from the current working dir: I guess it's fine to completely disable that, like we did in TEZ-4659
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done added like if with use paths like ../ moves upward from the pwd from which process was launched it should throw IO exception
tez-yetus
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Mar 30, 2026
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tez-yetus
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Mar 30, 2026
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…in CSVResult.java (apache#471) (Ramit Gupta reviewed by Laszlo Bodor)
…in CSVResult.java (#471) (Ramit Gupta reviewed by Laszlo Bodor)
validated using following command on cluster: