doc: note that setAuthTag throws on invalid length

PR-URL: #17825
Refs: #17523
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/crypto.md

@@ -419,6 +419,9 @@ The `decipher.setAAD()` method must be called before [`decipher.update()`][].
 <!-- YAML
 added: v1.0.0
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/17825
+    description: This method now throws if the GCM tag length is invalid.
   - version: v7.2.0
     pr-url: https://github.com/nodejs/node/pull/9398
     description: This method now returns a reference to `decipher`.
@@ -430,7 +433,9 @@ When using an authenticated encryption mode (only `GCM` and `CCM` are currently
 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.
+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