doc: update notes about GCM decryption

Given that https://github.com/nodejs/node/pull/17825 and
https://github.com/nodejs/node/pull/20039 have landed on master, this
statement is no longer true.

PR-URL: https://github.com/nodejs/node/pull/21445
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
This commit is contained in:
Tobias Nießen 2018-06-21 17:59:49 +02:00 committed by Michaël Zasso
parent fd520e7b43
commit 193d6d1bda
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@ -441,16 +441,8 @@ supported), the `decipher.setAuthTag()` method is used to pass in the
received _authentication tag_. If no tag is provided, or if the cipher text
has been tampered with, [`decipher.final()`][] will throw, indicating that the
cipher text should be discarded due to failed authentication. If the tag length
is invalid according to [NIST SP 800-38D][], `decipher.setAuthTag()` will throw
an error.
Note that this Node.js version does not verify the length of GCM authentication
tags. Such a check *must* be implemented by applications and is crucial to the
authenticity of the encrypted data, otherwise, an attacker can use an
arbitrarily short authentication tag to increase the chances of successfully
passing authentication (up to 0.39%). It is highly recommended to associate one
of the values 16, 15, 14, 13, 12, 8 or 4 bytes with each key, and to only permit
authentication tags of that length, see [NIST SP 800-38D][].
is invalid according to [NIST SP 800-38D][] or does not match the value of the
`authTagLength` option, `decipher.setAuthTag()` will throw an error.
The `decipher.setAuthTag()` method must be called before
[`decipher.final()`][].