fp6-vendor-blobs 1-r3: extract from the active slot, and stop pinning a hash on a signed image
Two field units got no fingerprint sensor from fingerprintd 0.2.3's manifest: its focal64 line pinned the sha256 of one Android build's trustlet (16.82.0, the dev phone's), and Fairphone re-signs that trustlet every release, so the pin matches exactly one of the six builds seen. A user on 16.100.0 had to edit the manifest by hand; another ended up with a file QTEE refuses. The extractor now tries the active slot's partitions first (androidboot.slot_suffix from the kernel command line): for a signed image only the running TZ's own slot is guaranteed to load. An mbn line may give '-' instead of a hash, which means structural verification only: ELF64 header, every segment present at the size its program header declares, page-aligned offsets, a sane total. The loader in TZ verifies the signature and the per-segment hashes itself and refuses a damaged or foreign image (one flipped byte -> ERROR_ELF_SIGNATURE_ERROR, measured), so the whole-image hash added fragility and no protection. A real sha256 is still honoured, and the sha256 of what was installed is logged either way. --refresh re-derives mbn dests even when a file exists, replacing it only with an image that verifies; consumers call it from post-install/post-upgrade so a fresh 'apk add' needs no reboot and a hand-placed or wrongly pinned trustlet is replaced on the next upgrade. Verified on the dev phone (busybox): malformed inputs are refused with a reason (missing, truncated or oversize segment; non-ELF, ELF32 or short mdt; a garbage offset), both slots reassemble to the known-good hash, a foreign file survives a plain run and is replaced by --refresh, a failed refresh keeps the old file, pins still work, and the real post-upgrade path re-derived the installed trustlet with the daemon restarting on it. Record: fp6 repo journal/blobs/ and journal/fingerprint/, 2026-09-11.
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2 changed files with 100 additions and 26 deletions
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@ -10,9 +10,15 @@
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# processed in sorted order; '#' comments and blank lines ignored:
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#
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# file <partition[,partition...]> <path-in-partition> <dest> <sha256>
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# mbn <partition[,partition...]> <dir-in-partition> <name> <dest> <sha256>
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# mbn <partition[,partition...]> <dir-in-partition> <name> <dest> <sha256|->
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# rebind <bus> <device>
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#
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# Partition lists are tried in the order written, except that on an A/B
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# device the ACTIVE slot's partitions (androidboot.slot_suffix in
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# /proc/cmdline) come first: the other slot may hold a different Android
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# build, and for a signed image only the active slot's copy is guaranteed to
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# match the TZ that is running.
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#
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# file: mount the first available listed partition READ-ONLY (ext4 also
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# gets -o noload - never a byte written to the stock partitions, not
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# even a journal replay), copy <path-in-partition> to <dest>, verify the
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@ -28,9 +34,19 @@
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# Reassembly is therefore not a concatenation: segments are page aligned
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# but not contiguous, gaps stay zero, and two segments may share an offset
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# (focal64 has two such pairs), so they are written in index order and the
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# later one wins. Same guarantees as file: the sha256 is of the reassembled
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# image, a mismatch tries the next partition, and an unverified image is
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# never installed.
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# later one wins. With a real sha256 the guarantees are file's: the hash is
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# of the reassembled image, a mismatch tries the next partition, an
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# unverified image is never installed. With '-' the image is verified
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# STRUCTURALLY instead - ELF64 header, every segment present at the size
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# its program header declares, page-aligned offsets, sane total - and not
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# against a pinned hash. That is the right mode for an OEM-signed trustlet:
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# the OEM re-signs it every Android release, so one whole-image hash matches
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# exactly one build (six builds, six hashes, one trustlet: fp6 repo
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# journal/fingerprint/ 2026-09-07..11, two field units failed on the pin),
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# while the loader in TZ verifies the signature and the per-segment hashes
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# itself and refuses a damaged or foreign image (one flipped byte ->
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# ERROR_ELF_SIGNATURE_ERROR, measured 2026-09-03). The sha256 of what was
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# installed is logged either way.
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# rebind: if this fragment's run extracted at least one file, unbind and
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# re-probe <device> on <bus> so the consuming driver picks the file up
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# in the same boot. Unconditional on purpose: a still-bound consumer may
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@ -48,6 +64,13 @@
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# --if-device: exit 0 quietly when no stock super partition is visible
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# (apk post-install scripts run inside build/CI chroots too; on images
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# built there the first-boot service does the real extraction).
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# --refresh: re-derive every mbn dest even if it exists, replacing it only
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# with an image that verifies (a failed refresh leaves the old file). For
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# the consumer's post-install/post-upgrade: a fresh 'apk add' gets its
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# trustlet without a reboot, and a trustlet that was hand-placed or pinned
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# to another build is replaced by the active slot's on the next upgrade.
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# file dests are still left alone: re-copying the acf would rebind the
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# sound card on every upgrade for nothing.
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MANIFEST_DIR=/usr/share/fp6-vendor-blobs/manifest.d
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SUPER=/dev/disk/by-partlabel/super
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@ -55,6 +78,10 @@ MNT=
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MNT_PART=
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CREATED=
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TRIED_MAPPING=
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IF_DEVICE=
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REFRESH=
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# "a" or "b" on an A/B device (androidboot.slot_suffix=_a), else empty
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ACTIVE_SLOT=$(tr ' ' '\n' </proc/cmdline 2>/dev/null | sed -n 's/^androidboot\.slot_suffix=_\([ab]\)$/\1/p' | head -n1)
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log() { echo "fp6-vendor-blobs: $*"; }
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@ -114,10 +141,26 @@ mount_part() {
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MNT_PART=$1
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}
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# The listed partitions, space separated, the active slot's first.
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order_parts() { # <partition,...>
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first= rest=
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for p in $(echo "$1" | tr ',' ' '); do
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if [ -n "$ACTIVE_SLOT" ] && [ "${p%_$ACTIVE_SLOT}" != "$p" ]; then
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first="$first $p"
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else
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rest="$rest $p"
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fi
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done
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echo "$first $rest"
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}
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# Little-endian scalars out of an ELF header. aarch64 is little endian and so
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# is the image, so od's host order is the right one.
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u64() { od -An -tu8 -j "$2" -N 8 "$1" | tr -d ' '; }
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u16() { od -An -tu2 -j "$2" -N 2 "$1" | tr -d ' '; }
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u8() { od -An -tu1 -j "$2" -N 1 "$1" | tr -d ' '; }
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hex4() { od -An -tx1 -N 4 "$1" | tr -d ' \n'; }
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fsize() { stat -c %s "$1"; }
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# Reassemble <dir>/<name>.mdt + .b0N into a flat image at <out>. Mirrors
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# utilities/ta-analysis/reassemble.py in the fp6 bring-up repo, which is where
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@ -130,9 +173,18 @@ reassemble() { # <dir> <name> <out>
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mdir=$1 mname=$2 mout=$3
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mdt="$mdir/$mname.mdt"
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[ -f "$mdt" ] || return 1
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# Structure first, before anything is written: an ELF64 header whose
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# program header table fits in the .mdt, and for every segment with
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# contents a .b0N file of exactly the declared size at a page-aligned
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# offset. This is the whole verification when the manifest pins no hash;
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# the loader's own signature check does the rest.
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[ "$(hex4 "$mdt")" = 7f454c46 ] || { log "$mname.mdt: not an ELF image"; return 1; }
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[ "$(u8 "$mdt" 4)" = 2 ] || { log "$mname.mdt: not ELF64"; return 1; }
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phoff=$(u64 "$mdt" 32) phentsize=$(u16 "$mdt" 54) phnum=$(u16 "$mdt" 56)
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[ -n "$phoff" ] && [ -n "$phentsize" ] && [ -n "$phnum" ] || return 1
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[ "$phnum" -gt 0 ] 2>/dev/null || return 1
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[ "$phentsize" -eq 56 ] 2>/dev/null || { log "$mname.mdt: phentsize $phentsize"; return 1; }
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[ "$phnum" -gt 0 ] 2>/dev/null && [ "$phnum" -le 64 ] || { log "$mname.mdt: phnum $phnum"; return 1; }
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[ "$(fsize "$mdt")" -ge $((phoff + phnum * phentsize)) ] || { log "$mname.mdt: shorter than its program header table"; return 1; }
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# The image is as long as the furthest segment reaches; everything no
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# segment covers stays zero.
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@ -142,11 +194,21 @@ reassemble() { # <dir> <name> <out>
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pfsz=$(u64 "$mdt" $((o + 32)))
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if [ "$pfsz" -gt 0 ]; then
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poff=$(u64 "$mdt" $((o + 8)))
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seg=$(printf '%s/%s.b%02d' "$mdir" "$mname" "$i")
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[ -f "$seg" ] || { log "$mname: segment $i missing"; return 1; }
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[ "$(fsize "$seg")" -eq "$pfsz" ] || { log "$mname: segment $i is $(fsize "$seg") bytes, header says $pfsz"; return 1; }
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# dd seeks in whole blocks, which is only correct because
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# every p_offset in these images is page aligned. Refuse
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# rather than silently misplace a segment if that changes.
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[ $((poff % 4096)) -eq 0 ] || { log "$mname: segment $i offset $poff is not page aligned"; return 1; }
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[ $((poff + pfsz)) -gt "$total" ] && total=$((poff + pfsz))
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fi
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i=$((i + 1))
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done
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[ "$total" -gt 0 ] || return 1
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[ "$total" -gt 0 ] || { log "$mname: no segment has contents"; return 1; }
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# an order of magnitude above any TA; a garbage p_offset would otherwise
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# make a sparse multi-GiB file that then gets hashed
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[ "$total" -le $((64 * 1024 * 1024)) ] || { log "$mname: image would be $total bytes"; return 1; }
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: > "$mout" || return 1
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truncate -s "$total" "$mout" || return 1
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@ -157,14 +219,6 @@ reassemble() { # <dir> <name> <out>
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if [ "$pfsz" -gt 0 ]; then
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poff=$(u64 "$mdt" $((o + 8)))
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seg=$(printf '%s/%s.b%02d' "$mdir" "$mname" "$i")
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[ -f "$seg" ] || { log "$mname: segment $i missing"; return 1; }
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# dd seeks in whole blocks, which is only correct because
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# every p_offset in these images is page aligned. Refuse
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# rather than silently misplace a segment if that changes.
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[ $((poff % 4096)) -eq 0 ] || {
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log "$mname: segment $i offset $poff is not page aligned"
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return 1
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}
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dd if="$seg" of="$mout" bs=4096 seek=$((poff / 4096)) \
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conv=notrunc 2>/dev/null || return 1
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fi
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@ -173,9 +227,9 @@ reassemble() { # <dir> <name> <out>
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return 0
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}
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extract_mbn() { # <partition,...> <dir-in-partition> <name> <dest> <sha256>
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extract_mbn() { # <partition,...> <dir-in-partition> <name> <dest> <sha256|->
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parts=$1 rdir=$2 rname=$3 dest=$4 want=$5
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for part in $(echo "$parts" | tr ',' ' '); do
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for part in $(order_parts "$parts"); do
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mount_part "$part" || { log "$part: not mountable, trying next"; continue; }
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[ -f "$MNT/$rdir/$rname.mdt" ] || { log "$part: no $rdir/$rname.mdt, trying next"; continue; }
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tmp="$dest.fp6-extract.$$"
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@ -186,21 +240,26 @@ extract_mbn() { # <partition,...> <dir-in-partition> <name> <dest> <sha256>
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continue
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fi
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got=$(sha256sum "$tmp" | awk '{print $1}')
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if [ "$got" != "$want" ]; then
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if [ "$want" != - ] && [ "$got" != "$want" ]; then
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rm -f "$tmp"
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log "$part:$rdir/$rname sha256 $got != expected, trying next"
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continue
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fi
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chmod 644 "$tmp" && mv "$tmp" "$dest" || { rm -f "$tmp"; fail "installing $dest failed"; }
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log "reassembled $part:$rdir/$rname.{mdt,b0N} -> $dest"
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log "reassembled $part:$rdir/$rname.{mdt,b0N} -> $dest (sha256 $got)"
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return 0
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done
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fail "no listed partition ($parts) yields $rname with sha256 $want - $dest NOT installed"
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kept=
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[ -e "$dest" ] && kept=" (the existing file is left in place)"
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if [ "$want" = - ]; then
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fail "no listed partition ($parts) yields a well-formed $rname - $dest NOT installed$kept"
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fi
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fail "no listed partition ($parts) yields $rname with sha256 $want - $dest NOT installed$kept"
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}
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extract() { # <partition,...> <path-in-partition> <dest> <sha256>
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parts=$1 src=$2 dest=$3 want=$4
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for part in $(echo "$parts" | tr ',' ' '); do
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for part in $(order_parts "$parts"); do
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mount_part "$part" || { log "$part: not mountable, trying next"; continue; }
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[ -f "$MNT/$src" ] || { log "$part: no $src, trying next"; continue; }
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tmp="$dest.fp6-extract.$$"
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@ -239,7 +298,14 @@ rebind_all() { # <bus/device ...>
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done
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}
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if [ "${1:-}" = --if-device ] && [ ! -b "$SUPER" ]; then
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for arg in "$@"; do
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case "$arg" in
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--if-device) IF_DEVICE=1 ;;
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--refresh) REFRESH=1 ;;
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*) fail "unknown option '$arg'" ;;
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esac
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done
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if [ -n "$IF_DEVICE" ] && [ ! -b "$SUPER" ]; then
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log "no stock super partition visible (build chroot?), nothing to do"
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exit 0
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fi
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@ -253,11 +319,12 @@ for f in "$MANIFEST_DIR"/*.manifest; do
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while read -r kind a b c d e; do
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case "$kind" in
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file) [ -e "$c" ] || missing=1 ;;
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mbn) [ -e "$d" ] || missing=1 ;;
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mbn) [ -e "$d" ] && [ -z "$REFRESH" ] || missing=1 ;;
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esac
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done < "$f"
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done
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[ -z "$missing" ] && exit 0
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[ -n "$ACTIVE_SLOT" ] && log "active slot $ACTIVE_SLOT"
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for f in "$MANIFEST_DIR"/*.manifest; do
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[ -e "$f" ] || continue
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@ -274,7 +341,7 @@ for f in "$MANIFEST_DIR"/*.manifest; do
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;;
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mbn)
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[ -n "$e" ] || fail "$f: malformed mbn line"
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[ -e "$d" ] && continue
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[ -e "$d" ] && [ -z "$REFRESH" ] && continue
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extract_mbn "$a" "$b" "$c" "$d" "$e" </dev/null
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extracted=1
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;;
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