didericis
f7fb691626
First piece of PRD 0007: the per-agent SSH egress gate that will let pipelock stop seeing SSH traffic. This commit only lands the backend-agnostic surface — the SSHGate ABC, SSHGatePlan, the listen-port assignment (BASE_LISTEN_PORT + index), and the entrypoint-script renderer. Backend wiring lands in follow-up commits.
125 lines
4.7 KiB
Python
125 lines
4.7 KiB
Python
"""Per-agent SSH egress gate (PRD 0007).
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A second per-agent sidecar that does plain TCP forwarding from a set
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of static listen ports to the SSH hosts declared in `bottle.ssh`.
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The agent's ssh client points each `Host` block at the gate
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container + a per-entry listen port; pipelock stops seeing SSH
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traffic entirely.
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This module defines the abstract gate (`SSHGate`) and the plan
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dataclass (`SSHGatePlan`) consumed by its `start`. The sidecar's
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start/stop lifecycle is backend-specific and lives on concrete
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subclasses (see `claude_bottle/backend/docker/ssh_gate.py`)."""
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from __future__ import annotations
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from abc import ABC, abstractmethod
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from dataclasses import dataclass
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from pathlib import Path
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from .manifest import Bottle
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# First listen port on the gate; entry i listens on BASE_LISTEN_PORT + i.
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# Picked high enough to avoid colliding with anything an alpine image
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# might pre-bind. The port space is per-gate (gate is per-agent) so
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# collisions across bottles aren't possible.
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BASE_LISTEN_PORT = 30000
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@dataclass(frozen=True)
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class SSHGateUpstream:
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"""One forwarder rule on the gate: listen locally on `listen_port`,
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forward each connection to `upstream_host:upstream_port`. The
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`bottle_host_alias` is the `Host` value from the manifest entry,
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kept for diagnostics + so the ssh provisioner can correlate
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upstreams with their alias."""
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listen_port: int
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upstream_host: str
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upstream_port: str
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bottle_host_alias: str
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@dataclass(frozen=True)
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class SSHGatePlan:
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"""Output of SSHGate.prepare; consumed by .start when the sidecar
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needs to be brought up.
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`upstreams` + `slug` + `entrypoint_script` are filled in at
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prepare time (host-side, side-effect-free on docker). The network
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fields are populated by the backend's launch step via
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`dataclasses.replace` once those networks exist. Empty defaults
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are sentinels meaning "not yet set"; `.start` validates that
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they are populated."""
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slug: str
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entrypoint_script: Path
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upstreams: tuple[SSHGateUpstream, ...]
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internal_network: str = ""
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egress_network: str = ""
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def ssh_gate_upstreams_for_bottle(bottle: Bottle) -> tuple[SSHGateUpstream, ...]:
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"""Deterministic assignment of listen ports to bottle.ssh entries:
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BASE_LISTEN_PORT + index. Order matches `bottle.ssh` so a manifest
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re-order yields a different port mapping (intentional — the
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provisioner reads the same tuple)."""
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return tuple(
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SSHGateUpstream(
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listen_port=BASE_LISTEN_PORT + i,
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upstream_host=e.Hostname,
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upstream_port=e.Port,
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bottle_host_alias=e.Host,
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)
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for i, e in enumerate(bottle.ssh)
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)
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def ssh_gate_render_entrypoint(upstreams: tuple[SSHGateUpstream, ...]) -> str:
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"""Render the gate's entrypoint script: one `socat TCP-LISTEN`
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per upstream, all backgrounded, then `wait`. Posix sh, no bash-isms
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(alpine's sh is busybox ash). If any one socat dies, the others
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keep running until the container is removed — matches the v1
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no-restart policy from the PRD."""
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lines = ["#!/bin/sh", "set -eu"]
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for u in upstreams:
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lines.append(
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f"socat TCP-LISTEN:{u.listen_port},reuseaddr,fork "
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f"TCP:{u.upstream_host}:{u.upstream_port} &"
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)
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lines.append("wait")
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return "\n".join(lines) + "\n"
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class SSHGate(ABC):
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"""The per-agent SSH egress gate. Encapsulates the host-side
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prepare step (upstream allocation + entrypoint render); the
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sidecar's start/stop lifecycle is backend-specific and lives on
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concrete subclasses."""
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def prepare(self, bottle: Bottle, slug: str, stage_dir: Path) -> SSHGatePlan:
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"""Compute the upstream table from `bottle.ssh` and write the
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entrypoint script (mode 600) under `stage_dir`. Pure host-side,
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no docker subprocess.
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Returned plan is incomplete: the launch step must fill
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`internal_network` / `egress_network` via `dataclasses.replace`
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before passing the plan to `.start`."""
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upstreams = ssh_gate_upstreams_for_bottle(bottle)
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script = stage_dir / "ssh_gate_entrypoint.sh"
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script.write_text(ssh_gate_render_entrypoint(upstreams))
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script.chmod(0o600)
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return SSHGatePlan(slug=slug, entrypoint_script=script, upstreams=upstreams)
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@abstractmethod
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def start(self, plan: SSHGatePlan) -> str:
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"""Bring up the gate sidecar according to `plan`. Returns the
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target string identifying the running instance — the same
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value to pass to `.stop`. Backend-specific."""
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@abstractmethod
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def stop(self, target: str) -> None:
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"""Tear down the gate sidecar identified by `target` (the
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value `.start` returned). Idempotent: a missing target is
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success. Backend-specific."""
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