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Add a warning about expensive pattern constraints #837

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Jun 17, 2021
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Add a warning about expensive pattern constraints #837

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9 changes: 9 additions & 0 deletions docs/source/1.0/spec/core/constraint-traits.rst
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Expand Up @@ -406,6 +406,14 @@ conditionals, directives, recursion, lookahead, look-behind, back-references,
and look-around in order to ensure maximum compatibility across programming
languages.

.. warning::

Pattern values should be chosen with care, as regex evaluation can be
expensive. Regular expressions SHOULD be tested against a range of
potentially malformed inputs to ensure that the execution of the regular
expression match does not lead to a potential denial of service. See
`OWASP Regular expression Denial of Service`_ for more information.

.. important::

The ``pattern`` trait does not implicitly add a leading ``^`` or trailing
Expand Down Expand Up @@ -674,3 +682,4 @@ minimum will be ``7``, and the maximum ``12``.

.. _ECMA 262 regular expression dialect: https://www.ecma-international.org/ecma-262/8.0/index.html#sec-patterns
.. _CommonMark: https://spec.commonmark.org/
.. _OWASP Regular expression Denial of Service: https://owasp.org/www-community/attacks/Regular_expression_Denial_of_Service_-_ReDoS