media: publish to our own origin instead of mirroring a file host
All checks were successful
Deploy / build-deploy (push) Successful in 7m34s

A 167 MB screen recording uploaded to catbox.moe hit fetch-media.sh's 64 MB
MAX_BYTES, so curl refused it, the entry kept its third-party URL, and e2e
failed "/posts media origin" on a file we had on disk the whole time. Raising
the cap would have papered over it: the mirror step still depends on someone
else's server being up, fast, and still holding the file.

Invert it. tools/publish-media.sh uploads a recording to the media mount under
its content hash BEFORE the post exists and prints the URL to post, and
fetch-media.sh adopts an own-origin URL by rewriting it to /media/<hash> with no
request at all — no size cap, no third party in the build.

Also here, because publishing exposed them:

  * Rotation. Phones record 1920x1080 and attach a display matrix rather than
    rotating pixels, so an untouched file reports landscape while playing
    portrait and width/height reserve exactly the wrong box. publish-media.sh
    bakes rotation into the frames; fetch-media.sh swaps the dimensions on a
    quarter-turn matrix for anything mirrored straight from a phone.
  * Posters. pict-rs will not thumbnail AV1, so a self-hosted video usually
    arrives with no poster. publish-media.sh uploads <hash>.poster.webp beside
    the video and fetch-media.sh falls back to it — a real thumbnail still wins.
  * The workflow comment claiming a file on the mount is never downloaded again
    was wrong: the name is the hash of the bytes, so third-party media is
    re-fetched every build and only the write is skipped.

Transcoding to AV1 is what makes self-hosting cheap: that clip was 78 s of a
dark room at 17 Mbps, and denoise + AV1 gives the same picture in 15 MB. Note
<video> carries a single src with no fallback, so AV1 excludes Safari < 17;
--raw skips the transcode when that matters.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
This commit is contained in:
Jorijn van der Graaf 2026-08-08 01:16:17 +02:00
commit c1b0c29af6
4 changed files with 351 additions and 66 deletions

View file

@ -32,6 +32,16 @@ MEDIA_DIR="${1:-media}"
POSTS="content/posts.json"
MAX_BYTES=$((64 * 1024 * 1024))
# Media we host ourselves, published by tools/publish-media.sh before the post
# that carries it exists. Such a URL is ALREADY the one the page should use, so
# there is nothing to fetch: the bytes are on the media mount, and downloading
# them back from our own web server would only mint a second copy under a second
# name. Skipping the download also skips MAX_BYTES, which is what a 167 MB
# recording on a third-party file host ran into — and it removes the last part of
# a build that could fail because someone else's server was slow, rate-limiting
# or gone.
OWN_ORIGIN="https://catcrafts.net/media/"
command -v jq >/dev/null 2>&1 || { echo "fetch-media: jq not found" >&2; exit 1; }
[ -f "$POSTS" ] || { echo "fetch-media: $POSTS not found — run fetch-posts.sh first" >&2; exit 1; }
@ -44,12 +54,56 @@ mkdir -p "$MEDIA_DIR"
HAVE_FFPROBE=0
command -v ffprobe >/dev/null 2>&1 && HAVE_FFPROBE=1
# Sets $w and $h for the file named in $1, or leaves both 0.
#
# One query per dimension. Asking for both at once and splitting the CSV looked
# simpler but was wrong: for some files ffprobe appends an empty field, so
# `width,height` came back as "854x480x" and splitting on `x` gave a height of
# "480x" — which the digit guard below then threw away, silently costing the
# dimensions of exactly the videos that had the extra field. `nk=1` prints the
# bare value, so there is nothing to split.
#
# ROTATION: a phone records 1920x1080 and attaches a display matrix rather than
# rotating the pixels, so the stream reads landscape while the video plays
# portrait. Believing the stream there reserves a landscape box for a portrait
# video — precisely the layout shift these attributes exist to prevent — so a
# quarter-turn swaps them. Files that went through publish-media.sh have the
# rotation baked into the pixels and report no matrix at all; this is for
# anything mirrored straight from a phone.
probe_dims() {
w=0; h=0
[ "$HAVE_FFPROBE" = 1 ] || return 0
pw=$(ffprobe -v error -select_streams v:0 -show_entries stream=width \
-of default=nw=1:nk=1 "$1" 2>/dev/null | head -n1 || true)
ph=$(ffprobe -v error -select_streams v:0 -show_entries stream=height \
-of default=nw=1:nk=1 "$1" 2>/dev/null | head -n1 || true)
rot=$(ffprobe -v error -select_streams v:0 \
-show_entries stream_side_data=rotation \
-of default=nw=1:nk=1 "$1" 2>/dev/null | head -n1 || true)
case "$pw" in ''|*[!0-9]*) pw=0 ;; esac
case "$ph" in ''|*[!0-9]*) ph=0 ;; esac
# ffprobe reports this as a signed number that some builds print with a
# fractional part ("-90.000000"), so compare on the integer portion.
case "${rot%%.*}" in
90|-90|270|-270) t=$pw; pw=$ph; ph=$t ;;
esac
# Both or neither: a lone dimension is worse than none, because the browser
# derives the missing one from it and gets the aspect wrong.
if [ "$pw" -gt 0 ] && [ "$ph" -gt 0 ]; then w=$pw; h=$ph; fi
if [ "$w" = 0 ]; then
echo "fetch-media: no dimensions for $1; layout will shift on load" >&2
fi
}
MAP="$(mktemp)"
trap 'rm -f "$MAP"' EXIT
POSTERMAP="$(mktemp)"
trap 'rm -f "$MAP" "$POSTERMAP"' EXIT
printf '[]' > "$MAP"
printf '[]' > "$POSTERMAP"
downloaded=0
reused=0
adopted=0
failed=0
# Every distinct media URL across all posts, so a file shared by two posts is
@ -62,64 +116,87 @@ failed=0
while IFS= read -r src; do
[ -n "$src" ] || continue
ext=$(printf '%s' "$src" | sed -E 's/.*\.([A-Za-z0-9]+)$/\1/' | tr 'A-Z' 'a-z')
case "$ext" in
mp4|webm|mov|webp|png|jpg|jpeg|gif|avif) ;;
*) echo "fetch-media: skipping unexpected extension: $src" >&2; continue ;;
# Ours already — adopt the file on the mount and do no network at all.
# A URL that is on our origin but names a file that is NOT on the mount is
# left alone rather than invented: that is a post published without its
# media, and keeping the original URL makes the e2e origin check fail
# loudly instead of shipping a 404 in a <video> tag.
case "$src" in
"$OWN_ORIGIN"*)
name=${src#"$OWN_ORIGIN"}
# Refuse anything that is not a bare filename. A path separator or a
# traversal segment arriving from a post URL must never reach a path we
# then read or publish.
case "$name" in
''|*/*|*..*)
echo "fetch-media: refusing suspicious own-origin URL: $src" >&2
failed=$((failed + 1)); continue ;;
esac
dest="$MEDIA_DIR/$name"
if [ ! -f "$dest" ]; then
echo "fetch-media: $name not on the media mount, keeping original URL: $src" >&2
failed=$((failed + 1)); continue
fi
adopted=$((adopted + 1))
;;
*)
ext=$(printf '%s' "$src" | sed -E 's/.*\.([A-Za-z0-9]+)$/\1/' | tr 'A-Z' 'a-z')
case "$ext" in
mp4|webm|mov|webp|png|jpg|jpeg|gif|avif) ;;
*) echo "fetch-media: skipping unexpected extension: $src" >&2; continue ;;
esac
tmp="$(mktemp)"
# --max-filesize refuses an oversized body before writing it; the explicit
# size check afterwards covers servers that do not send Content-Length.
if ! curl -fsSL --max-time 120 --max-filesize "$MAX_BYTES" \
-A 'catcrafts.net-buildfetch/1.0 (+https://catcrafts.net)' \
"$src" -o "$tmp" 2>/dev/null; then
echo "fetch-media: download failed, keeping original URL: $src" >&2
rm -f "$tmp"
failed=$((failed + 1))
continue
fi
if [ "$(wc -c < "$tmp")" -gt "$MAX_BYTES" ]; then
echo "fetch-media: oversized, keeping original URL: $src" >&2
rm -f "$tmp"
failed=$((failed + 1))
continue
fi
hash=$(sha256sum "$tmp" | cut -c1-16)
name="$hash.$ext"
dest="$MEDIA_DIR/$name"
if [ -f "$dest" ]; then
rm -f "$tmp"
reused=$((reused + 1))
else
mv "$tmp" "$dest"
chmod 0644 "$dest"
downloaded=$((downloaded + 1))
fi
;;
esac
tmp="$(mktemp)"
# --max-filesize refuses an oversized body before writing it; the explicit
# size check afterwards covers servers that do not send Content-Length.
if ! curl -fsSL --max-time 120 --max-filesize "$MAX_BYTES" \
-A 'catcrafts.net-buildfetch/1.0 (+https://catcrafts.net)' \
"$src" -o "$tmp" 2>/dev/null; then
echo "fetch-media: download failed, keeping original URL: $src" >&2
rm -f "$tmp"
failed=$((failed + 1))
continue
fi
if [ "$(wc -c < "$tmp")" -gt "$MAX_BYTES" ]; then
echo "fetch-media: oversized, keeping original URL: $src" >&2
rm -f "$tmp"
failed=$((failed + 1))
continue
fi
probe_dims "$dest"
hash=$(sha256sum "$tmp" | cut -c1-16)
name="$hash.$ext"
dest="$MEDIA_DIR/$name"
if [ -f "$dest" ]; then
rm -f "$tmp"
reused=$((reused + 1))
else
mv "$tmp" "$dest"
chmod 0644 "$dest"
downloaded=$((downloaded + 1))
fi
# One query per dimension. Asking for both at once and splitting the CSV
# looked simpler but was wrong: for some files ffprobe appends an empty
# field, so `width,height` came back as "854x480x" and splitting on `x` gave
# a height of "480x" — which the digit guard below then threw away, silently
# costing the dimensions of exactly the videos that had the extra field.
# `nk=1` prints the bare value, so there is nothing to split.
w=0; h=0
if [ "$HAVE_FFPROBE" = 1 ]; then
pw=$(ffprobe -v error -select_streams v:0 -show_entries stream=width \
-of default=nw=1:nk=1 "$dest" 2>/dev/null | head -n1 || true)
ph=$(ffprobe -v error -select_streams v:0 -show_entries stream=height \
-of default=nw=1:nk=1 "$dest" 2>/dev/null | head -n1 || true)
case "$pw" in ''|*[!0-9]*) pw=0 ;; esac
case "$ph" in ''|*[!0-9]*) ph=0 ;; esac
# Both or neither: a lone dimension is worse than none, because the
# browser derives the missing one from it and gets the aspect wrong.
if [ "$pw" -gt 0 ] && [ "$ph" -gt 0 ]; then w=$pw; h=$ph; fi
if [ "$w" = 0 ]; then
echo "fetch-media: no dimensions for $name; layout will shift on load" >&2
fi
fi
# A self-hosted video has no Lemmy thumbnail to mirror when the instance
# cannot decode it — AV1 is the common case, since pict-rs will not generate
# a still from one. publish-media.sh uploads a poster frame alongside the
# video under the video's own hash, so look for that sibling and offer it to
# the rewrite below. Without a poster a preload="metadata" video is a black
# box until someone presses play.
case "$name" in
*.mp4|*.webm|*.mov)
sibling="${name%.*}.poster.webp"
if [ -f "$MEDIA_DIR/$sibling" ]; then
jq --arg k "/media/$name" --arg v "/media/$sibling" \
'. + [{key: $k, value: $v}]' "$POSTERMAP" > "$POSTERMAP.new" \
&& mv "$POSTERMAP.new" "$POSTERMAP"
fi
;;
esac
jq --arg src "$src" --arg path "/media/$name" \
--argjson w "${w:-0}" --argjson h "${h:-0}" \
@ -129,14 +206,15 @@ done <<EOF
$(jq -r '[.[].media[]? | .src, (.poster // empty)] | map(select(. != "")) | unique[]' "$POSTS")
EOF
echo "fetch-media: $downloaded new, $reused already present, $failed failed"
echo "fetch-media: $downloaded new, $reused already present, $adopted self-hosted, $failed failed"
# Rewrite each media entry to the local path. An entry with no mapping (download
# failed) keeps its original src, so the page still shows something rather than
# silently dropping the post's whole point.
TMP_POSTS="$(mktemp)"
if jq --slurpfile map "$MAP" '
if jq --slurpfile map "$MAP" --slurpfile posters "$POSTERMAP" '
($map[0] | map({key: .src, value: .}) | from_entries) as $m
| ($posters[0] | from_entries) as $pm
| map(.media = ((.media // []) | map(
. as $item
| ($m[$item.src] // null) as $hit
@ -148,7 +226,14 @@ if jq --slurpfile map "$MAP" '
# poster'\''s size to the <video> element would set the wrong aspect ratio.
| if (.poster // "") == "" then .
else . + { poster: (($m[.poster].path) // .poster) }
end)))
end
# Last resort, and only for media we host: the sibling poster frame
# publish-media.sh uploaded next to the video. Runs after the rewrite
# above so it sees the LOCAL src, and only fills a poster that is still
# empty — a thumbnail the instance did provide always wins.
| if ((.poster // "") == "") and (($pm[.src] // "") != "")
then . + { poster: $pm[.src] }
else . end)))
' "$POSTS" > "$TMP_POSTS" 2>/dev/null; then
# Same reason as the chmod on each mirrored file: mktemp is 0600 and the
# mode survives to production, where other users must read this.