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dchain/go.mod
vsecoder f885264d23 feat(media): mandatory metadata scrubbing on /feed/publish + FFmpeg sidecar 
Every photo from a phone camera ships with an EXIF block that leaks:
GPS coordinates, camera model + serial, original timestamp, software
name, author/copyright fields, sometimes an embedded thumbnail that
survives cropping. For a social feed positioned as privacy-friendly
we can't trust the client alone to scrub — a compromised build,
a future plugin, or a hostile fork would simply skip the step and
leak authorship data.

So: server-side scrub is mandatory for every /feed/publish upload.

New package: media

  media/scrub.go
    - Scrubber type with Scrub(ctx, bytes, claimedMIME) → (clean, actualMIME)
    - ScrubImage handles JPEG/PNG/GIF/WebP in-process: decodes, optionally
      downscales to 1080px max-dim, re-encodes as JPEG Q=75. Stdlib
      jpeg.Encode emits ZERO metadata → scrub is complete by construction.
    - Sidecar client (HTTP): posts video/audio bytes to an external
      FFmpeg worker at DCHAIN_MEDIA_SIDECAR_URL
    - Magic-byte MIME detection: rejects uploads where declared MIME
      doesn't match actual bytes (prevents a PDF dressed as image/jpeg
      from bypassing the scrubber)
    - ErrSidecarUnavailable: explicit error when video arrives but no
      sidecar is wired; operator opts in to fallback via
      --allow-unscrubbed-video (default: reject)

  media/scrub_test.go
    - Crafted EXIF segment with "SECRETGPS-…Canon-EOS-R5" canary —
      verifies the string is gone after ScrubImage
    - Downscale test (2000×1000 → 1080×540, aspect preserved)
    - MIME-mismatch rejection
    - Magic-byte detector sanity table

FFmpeg sidecar — new docker/media-sidecar/

  Tiny Go HTTP service (~180 LOC, no non-stdlib deps) that shells out
  to ffmpeg with -map_metadata -1 + -map 0:v -map 0:a? to guarantee
  only video + audio streams survive (no subtitles, attached pictures,
  or data channels that could carry hidden info).

  Re-encode profile:
    video → H.264 CRF 28 preset=fast, Opus 64k, MP4 faststart
    audio → Opus 64k, Ogg container

  Dockerfile: two-stage build (Go → alpine+ffmpeg), ~90 MB image, non-
  root user, /healthz endpoint for compose probes.

  Node reaches it via DCHAIN_MEDIA_SIDECAR_URL. Without it, video uploads
  are rejected with 503 unless operator sets DCHAIN_ALLOW_UNSCRUBBED_VIDEO.

/feed/publish wiring

  - cfg.Scrubber is a required dependency
  - Before storing post body we call scrubber.Scrub(); attachment bytes
    + MIME are replaced with the cleaned version
  - content_hash is computed over the SCRUBBED bytes — so the on-chain
    CREATE_POST tx references exactly what readers will fetch
  - EstimatedFeeUT uses the scrubbed size, so author's fee reflects
    actual on-disk cost
  - Content-type mismatches → 400; sidecar unavailable for video → 503

Flags / env vars

  --feed-db / DCHAIN_FEED_DB            (existing)
  --feed-ttl-days / DCHAIN_FEED_TTL_DAYS (existing)
  --media-sidecar-url / DCHAIN_MEDIA_SIDECAR_URL   (NEW)
  --allow-unscrubbed-video / DCHAIN_ALLOW_UNSCRUBBED_VIDEO (NEW; default false)

Client responsibilities (for reference — client work lands in Phase C)

  Even with server-side scrub, the client should still compress aggressively
  BEFORE upload, because:
    - upload time is ~N× larger for unscrubbed media (mobile networks)
    - the server's 256 KiB MaxPostSize is a HARD cap — oversized uploads
      are rejected, not silently truncated
    - the on-chain fee is size-based, so users pay for every byte the
      client didn't bother to shrink

  Recommended client pipeline:
    images → expo-image-manipulator: resize max-dim 1080px, WebP or
             JPEG quality 50-60
    videos → react-native-compressor: H.264 CRF 28, 720p max, 64k audio
    audio  → expo-audio's default Opus 32k (already compressed)

  Documented in docs/media-sidecar.md (added later with Phase C PR).

Tests
  - go test ./... green across 6 packages (blockchain consensus identity
    media relay vm)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2026-04-18 19:15:14 +03:00

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module go-blockchain
go 1.25.0
require (
github.com/dgraph-io/badger/v4 v4.2.0
github.com/libp2p/go-libp2p v0.32.2
github.com/libp2p/go-libp2p-kad-dht v0.25.2
github.com/libp2p/go-libp2p-pubsub v0.10.0
github.com/multiformats/go-multiaddr v0.12.3
github.com/tetratelabs/wazero v1.7.3
golang.org/x/crypto v0.49.0
)
require (
golang.org/x/image v0.39.0
golang.org/x/telemetry v0.0.0-20260311193753-579e4da9a98c // indirect
)
require (
github.com/benbjohnson/clock v1.3.5 // indirect
github.com/beorn7/perks v1.0.1 // indirect
github.com/cespare/xxhash/v2 v2.2.0 // indirect
github.com/containerd/cgroups v1.1.0 // indirect
github.com/coreos/go-systemd/v22 v22.5.0 // indirect
github.com/davidlazar/go-crypto v0.0.0-20200604182044-b73af7476f6c // indirect
github.com/decred/dcrd/dcrec/secp256k1/v4 v4.2.0 // indirect
github.com/dgraph-io/ristretto v0.1.1 // indirect
github.com/docker/go-units v0.5.0 // indirect
github.com/dustin/go-humanize v1.0.0 // indirect
github.com/elastic/gosigar v0.14.2 // indirect
github.com/flynn/noise v1.0.0 // indirect
github.com/francoispqt/gojay v1.2.13 // indirect
github.com/go-logr/logr v1.2.4 // indirect
github.com/go-logr/stdr v1.2.2 // indirect
github.com/go-task/slim-sprig v0.0.0-20230315185526-52ccab3ef572 // indirect
github.com/godbus/dbus/v5 v5.1.0 // indirect
github.com/gogo/protobuf v1.3.2 // indirect
github.com/golang/glog v1.0.0 // indirect
github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da // indirect
github.com/golang/protobuf v1.5.3 // indirect
github.com/golang/snappy v0.0.3 // indirect
github.com/google/flatbuffers v1.12.1 // indirect
github.com/google/gopacket v1.1.19 // indirect
github.com/google/pprof v0.0.0-20231023181126-ff6d637d2a7b // indirect
github.com/google/uuid v1.3.0 // indirect
github.com/gorilla/websocket v1.5.0
github.com/hashicorp/errwrap v1.1.0 // indirect
github.com/hashicorp/go-multierror v1.1.1 // indirect
github.com/hashicorp/golang-lru v0.5.4 // indirect
github.com/hashicorp/golang-lru/v2 v2.0.5 // indirect
github.com/huin/goupnp v1.3.0 // indirect
github.com/ipfs/boxo v0.10.0 // indirect
github.com/ipfs/go-cid v0.4.1 // indirect
github.com/ipfs/go-datastore v0.6.0 // indirect
github.com/ipfs/go-log v1.0.5 // indirect
github.com/ipfs/go-log/v2 v2.5.1 // indirect
github.com/ipld/go-ipld-prime v0.20.0 // indirect
github.com/jackpal/go-nat-pmp v1.0.2 // indirect
github.com/jbenet/go-temp-err-catcher v0.1.0 // indirect
github.com/jbenet/goprocess v0.1.4 // indirect
github.com/klauspost/compress v1.17.2 // indirect
github.com/klauspost/cpuid/v2 v2.2.6 // indirect
github.com/koron/go-ssdp v0.0.4 // indirect
github.com/libp2p/go-buffer-pool v0.1.0 // indirect
github.com/libp2p/go-cidranger v1.1.0 // indirect
github.com/libp2p/go-flow-metrics v0.1.0 // indirect
github.com/libp2p/go-libp2p-asn-util v0.3.0 // indirect
github.com/libp2p/go-libp2p-kbucket v0.6.3 // indirect
github.com/libp2p/go-libp2p-record v0.2.0 // indirect
github.com/libp2p/go-libp2p-routing-helpers v0.7.2 // indirect
github.com/libp2p/go-msgio v0.3.0 // indirect
github.com/libp2p/go-nat v0.2.0 // indirect
github.com/libp2p/go-netroute v0.2.1 // indirect
github.com/libp2p/go-reuseport v0.4.0 // indirect
github.com/libp2p/go-yamux/v4 v4.0.1 // indirect
github.com/libp2p/zeroconf/v2 v2.2.0 // indirect
github.com/marten-seemann/tcp v0.0.0-20210406111302-dfbc87cc63fd // indirect
github.com/mattn/go-isatty v0.0.20 // indirect
github.com/matttproud/golang_protobuf_extensions v1.0.4 // indirect
github.com/miekg/dns v1.1.56 // indirect
github.com/mikioh/tcpinfo v0.0.0-20190314235526-30a79bb1804b // indirect
github.com/mikioh/tcpopt v0.0.0-20190314235656-172688c1accc // indirect
github.com/minio/sha256-simd v1.0.1 // indirect
github.com/mr-tron/base58 v1.2.0 // indirect
github.com/multiformats/go-base32 v0.1.0 // indirect
github.com/multiformats/go-base36 v0.2.0 // indirect
github.com/multiformats/go-multiaddr-dns v0.3.1 // indirect
github.com/multiformats/go-multiaddr-fmt v0.1.0 // indirect
github.com/multiformats/go-multibase v0.2.0 // indirect
github.com/multiformats/go-multicodec v0.9.0 // indirect
github.com/multiformats/go-multihash v0.2.3 // indirect
github.com/multiformats/go-multistream v0.5.0 // indirect
github.com/multiformats/go-varint v0.0.7 // indirect
github.com/onsi/ginkgo/v2 v2.13.0 // indirect
github.com/opencontainers/runtime-spec v1.1.0 // indirect
github.com/opentracing/opentracing-go v1.2.0 // indirect
github.com/pbnjay/memory v0.0.0-20210728143218-7b4eea64cf58 // indirect
github.com/pkg/errors v0.9.1 // indirect
github.com/polydawn/refmt v0.89.0 // indirect
github.com/prometheus/client_golang v1.16.0 // indirect
github.com/prometheus/client_model v0.4.0 // indirect
github.com/prometheus/common v0.44.0 // indirect
github.com/prometheus/procfs v0.11.1 // indirect
github.com/quic-go/qpack v0.4.0 // indirect
github.com/quic-go/qtls-go1-20 v0.3.4 // indirect
github.com/quic-go/quic-go v0.39.4 // indirect
github.com/quic-go/webtransport-go v0.6.0 // indirect
github.com/raulk/go-watchdog v1.3.0 // indirect
github.com/spaolacci/murmur3 v1.1.0 // indirect
github.com/whyrusleeping/go-keyspace v0.0.0-20160322163242-5b898ac5add1 // indirect
go.opencensus.io v0.24.0 // indirect
go.opentelemetry.io/otel v1.16.0 // indirect
go.opentelemetry.io/otel/metric v1.16.0 // indirect
go.opentelemetry.io/otel/trace v1.16.0 // indirect
go.uber.org/dig v1.17.1 // indirect
go.uber.org/fx v1.20.1 // indirect
go.uber.org/mock v0.3.0 // indirect
go.uber.org/multierr v1.11.0 // indirect
go.uber.org/zap v1.26.0 // indirect
golang.org/x/exp v0.0.0-20231006140011-7918f672742d // indirect
golang.org/x/mod v0.34.0 // indirect
golang.org/x/net v0.52.0 // indirect
golang.org/x/sync v0.20.0 // indirect
golang.org/x/sys v0.42.0 // indirect
golang.org/x/text v0.36.0 // indirect
golang.org/x/tools v0.43.0 // indirect
gonum.org/v1/gonum v0.13.0 // indirect
google.golang.org/protobuf v1.31.0 // indirect
lukechampine.com/blake3 v1.2.1 // indirect
)
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