matrix-org/synapse

Upgrade to Bleach 1.5, to limit link schemes to an allowlist

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#2,860 opened on Feb 9, 2018

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A-Email-PushP4T-EnhancementZ-Help-Wantedgood first issue

Description

The 1.5 version of Bleach made the allowed protocols configurable: http://bleach.readthedocs.io/en/latest/clean.html#allowed-protocols-protocols

Once the dependency is updated, the safe_markup function in the mailer can be updated and these lines can be uncommented: https://github.com/matrix-org/synapse/blob/42b50483be2b022735f8ae2107314d51e92e8471/synapse/push/mailer.py#L76-L77

Contributor guide

Tech stack
python
Domain
backendsecurity
Issue type
security
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
under 1 hour
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Pythonpip
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
85
Research direction
First, upgrade the Bleach dependency in the project's requirements file (e.g., requirements.txt) to version 1.5. Then, modify the `safe markup` function in `synapse/push/mailer.py` to uncomment the lines (L76 L77) that configure allowed protocols, following Bleach's new API. Finally, ensure tests pass and consider adding a test for the new allowlist behavior.