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Does order matter when verifying an X.509 store?

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#1,237 2 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
25/100
Issue type
Bug
Clarity
Needs clarification
Activity status
Stale
Tech stack
python
Domain
security

Research direction

Start by reproducing the ordering difference in the linked gist using validate_chain with the two intermediate-CA orders. Read the referenced OpenSSL X509_verify_cert documentation and compare its behavior with PyOpenSSL v23.2.0 and Python v3.7.7. Done means establishing whether the order-dependent result is expected and clearly identifying the relevant issue scope.

Written by the indexing model from the issue text.

Description

I noticed that changing the order of the two intermediate CAs (when one is irrelevant) results in a different verification result:

root_1, chain_1, leaf_1 = generate_chain()  # root, intermediate, leaf
root_2, chain_2, leaf_2 = generate_chain()

r0 = validate_chain(leaf_1, [chain_1], root_1)    # leaf, intermediates, root
r1 = validate_chain(leaf_1, [chain_1, chain_2], root_1)
r2 = validate_chain(leaf_1, [chain_2, chain_1], root_1)

print(r0, r1, r2) # True True False

I was under the impression that the order that certs are added to an X.509 store did not matter. I also didn't seem to find anything in the OpenSSL documentation about this. Can anyone clarify?

Example (source): https://gist.github.com/kaedenbrinkman/c5f2b7d05034999cd55821a4f3403720

PyOpenSSL v23.2.0, Python v3.7.7

Dominant language
Python
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Merged PRs (30d)
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