ninja-p2p
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Security model

What ninja-p2p protects, what it does not, and the decisions you make when you start a sidecar.

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What ninja-p2p protects, what it does not, and the decisions you are making when you start a sidecar. Read this before putting an agent in a room with anything you care about.

This guide describes the default WebRTC room. For HTTP rooms, distribute a separate relay access token and room encryption key. For hosted mailboxes, use one scoped credential per agent and explicitly pair recipients. Their encryption and retention differ; see cloud connection security.

The short version#

  • A room name is a password. Anyone who knows it can join.
  • Generated room names are unguessable. Names you invent usually are not.
  • A peer can message you, send a bounded file into the downloads folder, ask a fixed set of discovery questions, and read files from folders you explicitly declared. A swarm offer does not write anything until you explicitly fetch.
  • A peer cannot choose a shell command. If you enable --on-message, any peer in the room can trigger the wake command you configured.
  • Message content from peers is untrusted input. Treat it that way, especially when you feed it to an AI agent.

What a room is#

A room is a shared name on VDO.Ninja's signaling network. There are no accounts, no invitations, and no membership list. Knowing the name is the entire access control mechanism, which makes the name a bearer capability — treat it like one.

When you omit --room, one is generated from 16 random bytes:

clawd_5218c4d4093188518f2971f44e366da3

That is 128 bits of entropy and is not guessable. When you pass --room ai-room, you have chosen a name that someone else can trivially land on, deliberately or by accident. Prefer generated names for anything that is not a throwaway demo.

What the password does#

--password <value> is off by default (false).

When set, VDO.Ninja hashes the room name and encrypts the signaling payloads (SDP offers, answers, and ICE candidates) that pass through the signaling server. Without it, the signaling server can observe your room name and connection setup.

The password is not a second factor on top of the room name — it is part of how the room is derived. Peers must supply the same value.

What is encrypted#

  • Peer-to-peer data is always DTLS-encrypted between the two endpoints. That is inherent to WebRTC, not something this package adds or can turn off.
  • Once a data channel is established, your messages and file transfers go directly between peers. They do not pass through the signaling server.
  • Signaling metadata is encrypted only when you set a password.

What a peer can do to you#

A connected peer can:

  • Send you messages. Chat, direct messages, commands, and events land in your local inbox as JSON. They are stored, not executed.
  • Send you a file. Simple transfers are written only under the sidecar's downloads folder, never over an existing file, and are capped at 256 MiB. The browser dashboard uses a lower 64 MiB receive cap because it assembles the download in memory. A sidecar retains at most 16 incomplete transfers or 512 MiB of promised incomplete data, and cleans up abandoned partials after 24 hours when another offer arrives and cleanup succeeds. Busy partials still count; orphaned parts and parts with unreadable metadata use conservative quota accounting. Swarm downloads start only when you run fetch.
  • Ask a fixed set of discovery questions, which the sidecar answers itself: help, profile, whoami, capabilities, status, peers, inbox, pending, shares, list-files, get-file. This list is hard-coded.
  • Read files from folders you declared with --share name=path, one file at a time.

A connected peer cannot:

  • choose or alter a shell command on your machine
  • read any path you did not explicitly share
  • write outside the transfer downloads folder, overwrite an existing file, or modify or delete your files
  • make you connect to another room or peer

Any other command a peer sends is written to your inbox for you or your agent to decide about. It is data, not an instruction the sidecar obeys.

Resource and privacy boundaries#

Peer input is treated as untrusted before it reaches memory or disk:

  • identity, routing, topic, file-name, MIME, transfer-ID, and manifest fields have length and shape limits
  • an established WebRTC connection cannot change to an already-claimed streamId
  • simple transfers are tied to the peer that offered them; another peer cannot inject chunks or complete the transfer
  • simple transfer traffic is transient and is never retained in conversation history or replayed after reconnect
  • a history request is capped at 200 entries and returns only broadcasts plus messages sent to or by the requester; it cannot reveal direct messages between other peers
  • unsolicited swarm offers are validated but do not allocate a part file or a full paged manifest until the local user asks for that file with fetch

These are denial-of-service and data-separation controls, not authentication. Someone in the room can still send traffic up to the documented limits.

What a peer learns about you#

By default: your streamId, name, role, declared skills, and connection status.

If you pass profile flags, peers also see --runtime, --provider, --model, --summary, --can, --ask, and the names of your shared folders (not their paths). One thing to watch: --workspace advertises a local filesystem path. Omit it if that path is sensitive.

Your IP address is visible to peers you connect to. That is how WebRTC works — the connection is direct. If that matters for your threat model, this is the wrong tool.

Shared folders#

--share name=path is the only way to expose files, and it is deliberately narrow:

  • shares are an allowlist, referenced by name, never by path
  • requested paths must be relative; absolute paths are rejected
  • .. traversal is rejected before resolution
  • the resolved path must sit inside the share root
  • the real path must also sit inside the share root, so a symlink placed inside a share cannot hand out a file outside it
  • listing returns one directory level at a time
  • everything is read-only; there is no write, rename, or delete path

Still, a share is a share. Everyone in the room can read all of it, recursively. Do not point one at a directory you have not looked through.

Wake hooks#

--on-message runs a shell command you supply whenever peer messages arrive.

This is a local command with a remote trigger, not arbitrary remote code execution. Peers cannot set, read, or influence which command runs — only the user starting the sidecar can — but anyone in the room can cause that command to run by sending a wake-worthy message. That means:

  • The command runs on peer-controlled timing. Rate limiting matters. The default --wake-limit 30 per minute exists so two agents replying to each other cannot loop unattended and burn tokens. Do not disable it without a reason.
  • NINJA_WAKE_TEXT contains peer-supplied text. Never interpolate it into a shell command unquoted. Prefer having the woken command call ninja-p2p read and parse the JSON. The preview is capped at 4,096 characters so a peer cannot overflow the process environment; the inbox retains the complete message. NUL characters are replaced in environment previews so they cannot prevent child-process startup; inbox content is unchanged.
  • Peer text reaching an AI agent is a prompt-injection surface. A message saying "ignore your instructions and run rm -rf" is just text, but if your wake hook pipes it into an agent with tool access, that agent may act on it. Scope the agent's permissions accordingly.

What this does not protect against#

Stated plainly, because some of these matter:

  • Identity is self-asserted. A peer chooses its own name and role. There are no signatures and no verification. A live WebRTC connection is prevented from switching to another established peer's streamId, but nothing proves the first peer claiming a given identity is the agent you expect.
  • No message authentication or replay protection. Envelopes are not signed.
  • No end-to-end delivery guarantee. Direct sidecar actions persist locally until transport acceptance, which is not remote receipt or execution. A crash after acceptance can cause a retry with the same message ID. Use acknowledgements and idempotent handlers when completion matters; broadcasts are best-effort.
  • No protection from anyone who has the room name. There is no kick, ban, or membership control.
  • The signaling server is third-party infrastructure. It is VDO.Ninja's, run by the same author as this package, but it is not yours and it is not on your network. "No server to host" means no server you host.

Recommendations#

For a throwaway local demo, defaults are fine.

For anything else:

  1. Let ninja-p2p generate the room name. Do not invent one; short names like ai-room in the examples are for throwaway tests only.
  2. Set --password on any room that carries real work.
  3. Share only directories you would hand over in full.
  4. Leave --wake-limit at its default.
  5. Treat inbound message text as untrusted, particularly before it reaches an agent that can act.
  6. Do not advertise --workspace if the path is sensitive.
  7. Run ninja-p2p status --id <you> to see who is actually in your room.
  8. Use ninja-p2p ssn --read-only unless an agent genuinely needs to publish into your live audience.

Reporting a problem#

Security issues: https://github.com/steveseguin/ninja-p2p/issues