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Issue metadata

Status: WontFix
Owner: ----
Closed: Dec 27
Cc:
Components:
EstimatedDays: ----
NextAction: ----
OS: ----
Pri: 3
Type: Bug



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About AES-CBC supports.

Reported by cao111...@gmail.com, Dec 27

Issue description

Chrome Version       : 71.0.3578.98 (Official Build) (64-bit)
URLs (if applicable) : https://jsbin.com/mehugobewi/1/edit?js,console
Other browsers tested:
  Add OK or FAIL, along with the version, after other browsers where you
have tested this issue:
     Safari: OK (Version 12.0.2 (14606.3.4))
    Firefox: FAIL (Version 64.0 (64-bit))
       Edge: [NOT TESTED]

What steps will reproduce the problem?
(1) Run URL, PoC code.
(2) Check output

What is the expected result?
Support for AES-CBC decrypt processing.

What happens instead?
Support for AES-CBC decrypt processing.

Please provide any additional information below. Attach a screenshot if
possible.

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The issue was raised by https://t.me/akaza_akarin

 
Labels: Needs-Triage-M71
Components: Blink>WebCrypto
Status: WontFix (was: Unconfirmed)
Marking as WontFix/WorkingAsIntended. It is intentional that WebCrypto does not support AES-CBC, as with Mozilla.
Actually the problem is a bit different than stated (still WontFix though).

Chromium and Firefox both do support AES-CBC for WebCrypto.

The issue here is that the ciphertext has an incorrect padding not conformant to PKCS#7. There should be an extra block in the ciphertext that is all padding.

It is of concern that Safari allows this rather than failing with an OperationError for the padding failure...
Cc: davidben@chromium.org
Can I improve error info?
Distinguishing certain cryptographic errors can be used maliciously to infer things about the key/plaintext - for instance padding oracle attacks.

In this case the client is already in possession of the key, so that isn't a primary concern.

However as a general policy we don't surface error details in WebCrypto's OperationError other than basic input validation, to avoid the risk of leaking useful information.

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