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FabledCurator/backend/app/utils/html_sanitize.py
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feat(posts): faithful (semantic) HTML rendering of post bodies
Phase 1 of milestone #64. The body is captured (Phase 0) but was shown as
plain text. Now:
- html_sanitize.py: widen the allowlist to a faithful-but-safe set — headings,
  inline images, lists, blockquote, hr, code/pre, figure, links (div/span stay
  stripped; their text is preserved). Benefits the existing ProvenancePanel too.
- post_feed_service.get_post: add sanitized `description_html` to the DETAIL
  response (the feed list stays lightweight plain text by design).
- PostCard.vue: render description_html via v-html once expanded (fetched with
  detail); collapsed + no-detail fallback stay plain text. Styled close to the
  source (headings, images max-width, accent links, lists, quotes, code).

Tests: sanitizer (headings/img/lists survive, img javascript: src dropped);
get_post returns sanitized description_html.

Refs FC #830.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-14 13:02:21 -04:00

53 lines
1.9 KiB
Python

"""Backend HTML sanitization for scraped Post.description.
Provenance descriptions come from gallery-dl (untrusted third-party HTML).
We render them via v-html in the UI sub-slice, so they MUST be sanitized
server-side to a tight allowlist. nh3 (Rust/ammonia bindings) is used;
bleach is deprecated upstream and intentionally not used.
"""
import nh3
# A faithful-but-safe set: enough to reproduce the SEMANTIC look of a scraped
# post body (headings, lists, quotes, code, inline images, links, line breaks +
# inline emphasis) without layout-injection wrappers. `div`/`span` are
# deliberately NOT allowed — their text is preserved by nh3 and they only carry
# source-site layout/styling we don't want to import (a test pins this).
ALLOWED_TAGS = {
"p", "a", "br", "em", "strong", "b", "i", "u", "s",
"ul", "ol", "li", "blockquote",
"h1", "h2", "h3", "h4", "h5", "h6", "hr",
"pre", "code", "img", "figure", "figcaption",
}
ALLOWED_ATTRIBUTES = {
"a": {"href", "title", "target"},
"img": {"src", "alt", "title", "width", "height"},
}
# http/https for hotlinked source images today; relative URLs (e.g. a local
# `/api/...` src once inline images are captured) pass through nh3 untouched.
ALLOWED_URL_SCHEMES = {"http", "https"}
def sanitize_post_html(raw: str | None) -> str | None:
"""Return sanitized HTML, or None for null/empty/whitespace input.
- keeps only ALLOWED_TAGS / ALLOWED_ATTRIBUTES
- only http/https hrefs survive (javascript: etc. dropped)
- <script> content removed entirely
- all <a> get rel="noopener noreferrer" (nh3 default link_rel)
- never raises
"""
if raw is None:
return None
stripped = raw.strip()
if not stripped:
return None
return nh3.clean(
stripped,
tags=ALLOWED_TAGS,
attributes=ALLOWED_ATTRIBUTES,
url_schemes=ALLOWED_URL_SCHEMES,
link_rel="noopener noreferrer",
clean_content_tags={"script", "style"},
)