fix: Switch anonymous user ID hash from md5 to shake #26198
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BREAKING CHANGE: since function for hashing is different, it will produce different results for the same (user, course_id)
common/djangoapps/student/models.py
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| @@ -200,12 +200,18 @@ def anonymous_id_for_user(user, course_id, save=True): | |||
| monitoring.increment('temp_anon_uid_v2.fetched_existing') | |||
| else: | |||
| # include the secret key as a salt, and to make the ids unique across different LMS installs. | |||
| hasher = hashlib.md5() | |||
| hasher = hashlib.shake_128() | |||
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No test changes?
Incidentally, I'd call this a fix in the nomenclature of Conventional Commits.
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Oh no, yep, there will be.
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hmmm, I can kinda see, but still think it doesn't really work. We are not fixing a bug, we are just moving to a better algorithm.
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Honestly, I'm not real thrilled by the options suggested in that spec. :-) This isn't a feature, and it's not exactly a bug fix, it's... an "improvement".
jinder1s
changed the title
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Can you include the reason for the breaking change? |
timmc-edx
changed the title
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Updated PR message after discussion -- we had thought to call it a breaking change to be conservative, even though that was an unlikely scenario, but now we consider it so unlikely as to not be worth flagging that way. |
Co-authored-by: Tim McCormack <tmccormack@edx.org>
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Your PR has finished running tests. There were no failures. |
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EdX Release Notice: This PR has been deployed to the staging environment in preparation for a release to production. |
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EdX Release Notice: This PR has been deployed to the production environment. |
Now that we always return an existing value from the DB rather than trusting that ID generation is deterministic and constant over time, we're free to change the generation algorithm.
Our long term goal is to switch to random IDs, but we need to first investigate the uses of save=False. In the meantime, this is a good opportunity to move away from MD5, which has a number of cryptographic weaknesses. None of the known vulnerabilities are considered exploitable in this location, given the limited ability to control the input to the hash, but we should generally be moving away from it everywhere for consistency.
This change should not be breaking even for save=False callers, since those calls are extremely rare (1 in 100,000) and should only occur after a save=True call, at which point they'll use the stored value. Even if this were not true, for a save=False/True pair of calls to result in a mismatch in output, the first of the calls would have to occur around the time of the deploy of this code.