fix(gateway): validate image downloads before caching (cross-platform)#7125
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Slack may return an HTML sign-in/redirect page instead of actual media bytes (e.g. expired token, restricted file access). This adds two layers of defense: 1. Content-Type check in slack.py rejects text/html responses early 2. Magic-byte validation in base.py's cache_image_from_bytes() rejects non-image data regardless of source platform Also adds ValueError guards in wecom.py and email.py so the new validation doesn't crash those adapters. Closes #6829
This was referenced Apr 10, 2026
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Summary
Slack may return HTML sign-in/redirect pages instead of actual media bytes. This adds two layers of defense:
text/htmlresponses earlycache_image_from_bytes()rejects non-image data regardless of source platform (protects Slack, WeCom, Email, and future adapters)Also adds ValueError guards in wecom.py and email.py so the new validation doesn't crash those adapters.
Changes
gateway/platforms/base.py:_looks_like_image()+ validation incache_image_from_bytes()gateway/platforms/slack.py: Content-Type check before cachinggateway/platforms/email.py: ValueError guardgateway/platforms/wecom.py: ValueError guard (2 call sites)tests/gateway/test_media_download_retry.py: 6 new tests + existing tests updatedTest results
30 passed
Salvaged from #6971 (@Tranquil-Flow). Closes #6829.