Add support for forwarding activities

alembic/versions/93e36ff5c691_allow_activity_forwarding.py

@@ -0,0 +1,65 @@
+"""Allow activity forwarding
+
+Revision ID: 93e36ff5c691
+Revises: ba131b14c3a1
+Create Date: 2022-07-06 09:03:57.656539
+
+"""
+import sqlalchemy as sa
+from sqlalchemy.schema import CreateTable
+
+from alembic import op
+from app.database import engine
+from app.models import OutgoingActivity
+
+# revision identifiers, used by Alembic.
+revision = '93e36ff5c691'
+down_revision = 'ba131b14c3a1'
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.create_index(op.f('ix_inbox_activity_object_ap_id'), 'inbox', ['activity_object_ap_id'], unique=False)
+    op.create_index(op.f('ix_inbox_ap_type'), 'inbox', ['ap_type'], unique=False)
+    op.create_index(op.f('ix_outbox_activity_object_ap_id'), 'outbox', ['activity_object_ap_id'], unique=False)
+    op.create_index(op.f('ix_outbox_ap_type'), 'outbox', ['ap_type'], unique=False)
+    # ### end Alembic commands ###
+    # XXX: cannot remove alter to make a column nullable, we have to drop/recreate it
+    create_statement = CreateTable(OutgoingActivity.__table__).compile(engine)
+    op.execute("DROP TABLE IF EXISTS outgoing_activity;")
+    op.execute(f"{create_statement};")
+    # Instead of this:
+    # op.add_column('outgoing_activity', sa.Column('inbox_object_id', sa.Integer(), nullable=True))
+    # op.alter_column('outgoing_activity', 'outbox_object_id',
+    #           existing_type=sa.INTEGER(),
+    #           nullable=True)
+    # op.create_foreign_key(None, 'outgoing_activity', 'inbox', ['inbox_object_id'], ['id'])
+    # op.create_foreign_key(None, 'outgoing_activity', 'outbox', ['outbox_object_id'], ['id'])
+
+
+def downgrade() -> None:
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_table("outgoing_activity")
+    op.create_table('outgoing_activity',
+    sa.Column('id', sa.Integer(), nullable=False),
+    sa.Column('created_at', sa.DateTime(timezone=True), nullable=False),
+    sa.Column('recipient', sa.String(), nullable=False),
+    sa.Column('outbox_object_id', sa.Integer(), nullable=False),
+    sa.Column('tries', sa.Integer(), nullable=False),
+    sa.Column('next_try', sa.DateTime(timezone=True), nullable=True),
+    sa.Column('last_try', sa.DateTime(timezone=True), nullable=True),
+    sa.Column('last_status_code', sa.Integer(), nullable=True),
+    sa.Column('last_response', sa.String(), nullable=True),
+    sa.Column('is_sent', sa.Boolean(), nullable=False),
+    sa.Column('is_errored', sa.Boolean(), nullable=False),
+    sa.Column('error', sa.String(), nullable=True),
+    sa.ForeignKeyConstraint(['outbox_object_id'], ['outbox.id'], ),
+    sa.PrimaryKeyConstraint('id')
+    )
+    op.drop_index(op.f('ix_outbox_ap_type'), table_name='outbox')
+    op.drop_index(op.f('ix_outbox_activity_object_ap_id'), table_name='outbox')
+    op.drop_index(op.f('ix_inbox_ap_type'), table_name='inbox')
+    op.drop_index(op.f('ix_inbox_activity_object_ap_id'), table_name='inbox')
+    # ### end Alembic commands ###

app/ap_object.py

@@ -155,6 +155,10 @@ class Object:
     def in_reply_to(self) -> str | None:
         return self.ap_object.get("inReplyTo")
 
+    @property
+    def has_ld_signature(self) -> bool:
+        return bool(self.ap_object.get("signature"))
+
 
 def _to_camel(string: str) -> str:
     cased = "".join(word.capitalize() for word in string.split("_"))

app/boxes.py

@@ -417,6 +417,23 @@ async def _compute_recipients(
     return recipients
 
 
+async def _get_followers_recipients(db_session: AsyncSession) -> set[str]:
+    """Returns all the recipients from the local follower collection."""
+    followers = (
+        (
+            await db_session.scalars(
+                select(models.Follower).options(joinedload(models.Follower.actor))
+            )
+        )
+        .unique()
+        .all()
+    )
+    return {
+        follower.actor.shared_inbox_url or follower.actor.inbox_url
+        for follower in followers
+    }
+
+
 async def get_inbox_object_by_ap_id(
     db_session: AsyncSession, ap_id: str
 ) -> models.InboxObject | None:
@@ -455,6 +472,7 @@ async def get_anybox_object_by_ap_id(
 async def _handle_delete_activity(
     db_session: AsyncSession,
     from_actor: models.Actor,
+    delete_activity: models.InboxObject,
     ap_object_to_delete: models.InboxObject,
 ) -> None:
     if from_actor.ap_id != ap_object_to_delete.actor.ap_id:
@@ -464,6 +482,23 @@ async def _handle_delete_activity(
         )
         return
 
+    # If it's a local replies, it was forwarded, so we also need to forward
+    # the Delete activity if possible
+    if (
+        delete_activity.has_ld_signature
+        and ap_object_to_delete.in_reply_to
+        and ap_object_to_delete.in_reply_to.startswith(BASE_URL)
+    ):
+        logger.info("Forwarding Delete activity as it's a local reply")
+        recipients = await _get_followers_recipients(db_session)
+        for rcp in recipients:
+            await new_outgoing_activity(
+                db_session,
+                rcp,
+                outbox_object_id=None,
+                inbox_object_id=delete_activity.id,
+            )
+
     # TODO(ts): do we need to delete related activities? should we keep
     # bookmarked objects with a deleted flag?
     logger.info(f"Deleting {ap_object_to_delete.ap_type}/{ap_object_to_delete.ap_id}")
@@ -680,6 +715,19 @@ async def _handle_create_activity(
             .values(replies_count=models.OutboxObject.replies_count + 1)
         )
 
+        # This object is a reply of a local object, we may need to forward it
+        # to our followers (we can only forward JSON-LD signed activities)
+        if create_activity.has_ld_signature:
+            logger.info("Forwarding Create activity as it's a local reply")
+            recipients = await _get_followers_recipients(db_session)
+            for rcp in recipients:
+                await new_outgoing_activity(
+                    db_session,
+                    rcp,
+                    outbox_object_id=None,
+                    inbox_object_id=create_activity.id,
+                )
+
     for tag in tags:
         if tag.get("name") == LOCAL_ACTOR.handle or tag.get("href") == LOCAL_ACTOR.url:
             notif = models.Notification(
@@ -773,7 +821,12 @@ async def save_to_inbox(
         await _handle_update_activity(db_session, actor, inbox_object)
     elif activity_ro.ap_type == "Delete":
         if relates_to_inbox_object:
-            await _handle_delete_activity(db_session, actor, relates_to_inbox_object)
+            await _handle_delete_activity(
+                db_session,
+                actor,
+                inbox_object,
+                relates_to_inbox_object,
+            )
         else:
             # TODO(ts): handle delete actor
             logger.info(

app/httpsig.py

@@ -113,6 +113,7 @@ async def _get_public_key(db_session: AsyncSession, key_id: str) -> Key:
 class HTTPSigInfo:
     has_valid_signature: bool
     signed_by_ap_actor_id: str | None = None
+    is_ap_actor_gone: bool = False
 
 
 async def httpsig_checker(
@@ -139,7 +140,7 @@ async def httpsig_checker(
         k = await _get_public_key(db_session, hsig["keyId"])
     except ap.ObjectIsGoneError:
         logger.info("Actor is gone")
-        return HTTPSigInfo(has_valid_signature=False)
+        return HTTPSigInfo(has_valid_signature=False, is_ap_actor_gone=True)
     except Exception:
         logger.exception(f'Failed to fetch HTTP sig key {hsig["keyId"]}')
         return HTTPSigInfo(has_valid_signature=False)
@@ -162,6 +163,13 @@ async def enforce_httpsig(
         logger.warning(f"Invalid HTTP sig {httpsig_info=}")
         body = await request.body()
         logger.info(f"{body=}")
+
+        # Special case for Mastoodon instance that keep resending Delete
+        # activities for actor we don't know about if we raise a 401
+        if httpsig_info.is_ap_actor_gone:
+            logger.info("Let's make Mastodon happy, returning a 204")
+            raise fastapi.HTTPException(status_code=204)
+
         raise fastapi.HTTPException(status_code=401, detail="Invalid HTTP sig")
 
     return httpsig_info

app/ldsig.py

@@ -6,6 +6,7 @@ from datetime import datetime
 import pyld  # type: ignore
 from Crypto.Hash import SHA256
 from Crypto.Signature import PKCS1_v1_5
+from loguru import logger
 from pyld import jsonld  # type: ignore
 
 from app import activitypub as ap
@@ -59,7 +60,8 @@ async def verify_signature(
     doc: ap.RawObject,
 ) -> bool:
     if "signature" not in doc:
-        raise ValueError("No embedded signature")
+        logger.warning("The object does contain a signature")
+        return False
 
     key_id = doc["signature"]["creator"]
     key = await _get_public_key(db_session, key_id)

app/models.py

@@ -321,9 +321,14 @@ class OutgoingActivity(Base):
     created_at = Column(DateTime(timezone=True), nullable=False, default=now)
 
     recipient = Column(String, nullable=False)
-    outbox_object_id = Column(Integer, ForeignKey("outbox.id"), nullable=False)
+
+    outbox_object_id = Column(Integer, ForeignKey("outbox.id"), nullable=True)
     outbox_object = relationship(OutboxObject, uselist=False)
 
+    # Can also reference an inbox object if it needds to be forwarded
+    inbox_object_id = Column(Integer, ForeignKey("inbox.id"), nullable=True)
+    inbox_object = relationship(InboxObject, uselist=False)
+
     tries = Column(Integer, nullable=False, default=0)
     next_try = Column(DateTime(timezone=True), nullable=True, default=now)
 
@@ -335,6 +340,15 @@ class OutgoingActivity(Base):
     is_errored = Column(Boolean, nullable=False, default=False)
     error = Column(String, nullable=True)
 
+    @property
+    def anybox_object(self) -> OutboxObject | InboxObject:
+        if self.outbox_object_id:
+            return self.outbox_object  # type: ignore
+        elif self.inbox_object_id:
+            return self.inbox_object  # type: ignore
+        else:
+            raise ValueError("Should never happen")
+
 
 class TaggedOutboxObject(Base):
     __tablename__ = "tagged_outbox_object"

app/outgoing_activities.py

@@ -9,6 +9,7 @@ from loguru import logger
 from sqlalchemy import func
 from sqlalchemy import select
 from sqlalchemy.orm import Session
+from sqlalchemy.orm import joinedload
 
 from app import activitypub as ap
 from app import config
@@ -29,11 +30,18 @@ k.load(KEY_PATH.read_text())
 async def new_outgoing_activity(
     db_session: AsyncSession,
     recipient: str,
-    outbox_object_id: int,
+    outbox_object_id: int | None,
+    inbox_object_id: int | None = None,
 ) -> models.OutgoingActivity:
+    if outbox_object_id is None and inbox_object_id is None:
+        raise ValueError("Must reference at least one inbox/outbox activity")
+    elif outbox_object_id and inbox_object_id:
+        raise ValueError("Cannot reference both inbox/outbox activities")
+
     outgoing_activity = models.OutgoingActivity(
         recipient=recipient,
         outbox_object_id=outbox_object_id,
+        inbox_object_id=inbox_object_id,
     )
 
     db_session.add(outgoing_activity)
@@ -93,17 +101,26 @@ def process_next_outgoing_activity(db: Session) -> bool:
         select(models.OutgoingActivity)
         .where(*where)
         .limit(1)
+        .options(
+            joinedload(models.OutgoingActivity.inbox_object),
+            joinedload(models.OutgoingActivity.outbox_object),
+        )
         .order_by(models.OutgoingActivity.next_try)
     ).scalar_one()
 
     next_activity.tries = next_activity.tries + 1
     next_activity.last_try = now()
 
-    payload = ap.wrap_object_if_needed(next_activity.outbox_object.ap_object)
+    payload = ap.wrap_object_if_needed(next_activity.anybox_object.ap_object)
 
     # Use LD sig if the activity may need to be forwarded by recipients
-    if payload["type"] in ["Create", "Delete"]:
-        ldsig.generate_signature(payload, k)
+    if next_activity.anybox_object.is_from_outbox and payload["type"] in [
+        "Create",
+        "Delete",
+    ]:
+        # But only if the object is public (to help with deniability/privacy)
+        if next_activity.outbox_object.visibility == ap.VisibilityEnum.PUBLIC:
+            ldsig.generate_signature(payload, k)
 
     logger.info(f"{payload=}")
     try: