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"""
Deleting a file from a group (docs/MESHBAY_DESIGN.md §5.4).
The node decides, and on two grounds only: a key paired with it as operator, or
a live device of the account that uploaded the file — any of them, so a file
sent from a phone is deleted from the laptop. Being the group's owner on the hub
is neither. The request is answered with a challenge the client signs with its
key on the node; the node rebuilds what was signed itself.
"""
from meshbay_common import MNP_VERSION
from meshbay_common.adminop import OP_FILE_DELETE, admin_transcript
from ..errors import NODE, CliError
from .keys import b64, unb64
from .session import GroupSession
def may_delete(session: GroupSession, entry: dict, user_id: str) -> bool:
"""What the node will accept, known before asking: the operator, or the
file's uploader. The node checks again; this only avoids asking in vain."""
return session.role == "operator" or entry.get("uploader_id") == user_id
async def delete_file(session: GroupSession, file_id: str) -> None:
"""Delete one file. Raises `NodeRefusal` with the node's reason."""
reply = await session.ch.request({"type": "file_delete", "v": MNP_VERSION,
"file_id": file_id},
"admin_challenge", "file_delete_ack")
if reply["type"] == "file_delete_ack":
return
# What is signed is checked against what was asked, never taken from the
# node: a challenge for another operation, file, group or node is refused.
if (reply.get("op") != OP_FILE_DELETE or reply.get("subject") != file_id
or reply.get("group_id") != session.group_id
or reply.get("node_pk") != session.node_pk):
raise CliError(NODE, "The node asked to sign something other than this deletion; "
"nothing was signed.")
transcript = admin_transcript(op=OP_FILE_DELETE, node_pk_b64=session.node_pk,
group_id=session.group_id, subject=file_id,
nonce=unb64(reply["nonce"]), ts=int(reply["ts"]))
await session.ch.request({"type": "admin_response", "v": MNP_VERSION,
"op_id": reply["op_id"], "op": OP_FILE_DELETE,
"signature": b64(session.identity.sk_ed.sign(transcript))},
"file_delete_ack")
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