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Nicky LeachandClaude Opus 5.5
ff4ba7d319
## Thinking Path > - Paperclip is the open source app people use to manage AI agents for work > - The Rust Runner (`paperclip-runnerd`) starts provider sidecars and proxies from qualified launch artifacts: a Node runtime and the scripts it runs > - Since #12699, Runner copies each artifact into a sealed memfd and checks its SHA-256 on every verification. This defends against a path swap or an in-place rewrite between the check and the exec > - On a hosted agent computer (4 vCPU), the copy and digest of the 127 MB Node takes about 0.26–0.30 s warm and about 1.2 s right after a wake. This is on the path from `session.open` to the sidecar spawn, and again on every warm `run.attach`. Each Runner also holds about 125 MiB of shmem for the copy > - On that computer, the artifacts live on the Runner ROM: a read-only erofs image that the deploy pins by digest. The threat that the memfd defends against does not exist there. On local hosts the artifacts are writable, so the memfd must stay > - This pull request adds an explicit, path-scoped, default-off `--trusted-launch-root <dir>`. Runner runs an artifact in place only when its open descriptor proves that it is on an immutable mount under that root. Everything else keeps the sealed, hashed snapshot > - The benefit is a shorter `session.open` and `run.attach` on agent computers, and about 125 MiB less shmem per Runner, with no change where the flag is absent ## Linked Issues or Issue Description **What existing behavior does this improve?** Launch-artifact verification in `paperclip-runnerd` (`qualified_launch.rs`). Its callers are the ACPX `verified_transport` (every `session_config`, including the park rebind) and the OpenCode and Cursor Cloud proxy launches. **Subsystem affected** Rust Runner (`packages/paperclip-runner/runner/crates/runner-core`). **Current behavior** Every verification opens the artifact, copies all bytes into a sealed memfd, and hashes them. Node is 127 MB. The cost is described in the Thinking Path. **Proposed behavior** When the host passes `--trusted-launch-root /opt/paperclip/runner` and the root passes its checks, Runner holds each admitted artifact open in place and executes it through `/proc/self/fd/N`. It does not copy or re-hash it. Without the flag, nothing changes. **Reason and benefit** See the Thinking Path. Refs #12699 (introduced the sealed memfd). Refs #20423 (overlap, see below). ## What Changed - `qualified_launch.rs`: new `TrustedLaunchRoot` and `set_trusted_launch_root` (process-global, set once at startup, like `--task-memory-cgroup`). - **Root checks at startup.** The path must be absolute, already canonical (no symlink or `..`), a directory, and on a read-only, exec-permitted erofs or squashfs mount. If a check fails, runnerd logs a warning and keeps today's behavior. - **Per-artifact checks, on the open descriptor.** After today's checks (regular file, not a symlink, not group- or world-writable, open-time identity), the descriptor must be a regular file on the root's device. Its kernel path (`readlink /proc/self/fd/N`) must lie under the root by path components, so `/opt/paperclip/runner2` does not match. Its mount must pass `fstatvfs` (`ST_RDONLY` set, `ST_NOEXEC` clear) and `fstatfs` (erofs or squashfs magic). If any check fails, Runner logs the reason and uses the sealed snapshot. - **Admitted artifacts** become `VerifiedProcessArtifact::in_place_on_trusted_root` (crate-private). The held file goes through the existing `inherited_artifact` path, so the exec is `/proc/self/fd/N` and `PAPERCLIP_VERIFIED_RUNTIME_EXECUTABLE` still names a descriptor that nested launches can reopen. - New `verify_assigned_executable_launch_artifact` never uses the root. `stdio_mcp.rs` now calls it, so host-assigned stdio MCP binaries always keep the sealed snapshot. - `paperclip-runnerd.rs`: parse `--trusted-launch-root <dir>`. Older runnerd builds ignore unknown flags, so a host can pass it before every Runner understands it. - The trusted path is Linux-only. On macOS and Windows, `TrustedLaunchRoot::open` always refuses. - `tests/runner-e2e/SECURITY.md`: documents how the Kimi and Pi provider-death fixtures behave under a trusted root. ### Decision: the trusted path drops the digest The trusted path does not hash the artifact, not even once per process: - The ROM image is pinned by digest at deploy time. - On the agent computer, the Launcher computes the expected `--acpx-sidecar-command-sha256` and `--acpx-sidecar-script-sha256` from the same ROM files immediately before it starts Runner. A re-hash of an immutable file can only repeat that result. - One hash per process would not help `session.open`, because each task starts a new Runner process. - The mount check is the guard: erofs and squashfs have no write path, so the bytes cannot change while the descriptor is open. ### Fixtures that assert the sealed memfd - Untrusted-mode assertions are unchanged. The fixtures do not pass the flag. - Kimi (`kimi-provider-fault.py` `checked_parent_descriptor`): with a trusted root, the parent descriptor is the ROM's Node file (one link). The existing linked-descriptor branch handles it: same inode as `/proc/<pid>/exe`, and the complete bytes hashed against `nodeSha256`. That branch never accepts the file as a memfd. The existing test `test_linked_descriptor_keeps_regular_single_link_checks_without_memfd_claim` covers it. - Pi provider-death admission binds `/proc/self/fd/3|7` to the native distribution snapshot's Node. The TypeScript ACPX closure copies that file whether or not a trusted root is set, so the flag does not affect it. ### Overlap with #20423 #20423 (draft) moves the same copy and hash to Runner boot and reuses the result. Where this flag is set (Cloud agent computers), there is nothing left to precompute, so #20423 is mostly redundant there. #20423 still helps hosts without a trusted root (local and sandbox Runners). This PR does not change #20423. ## Verification All runs are on Linux (aarch64, Rust 1.97.1, in a container): - `cargo fmt --manifest-path runner/Cargo.toml --all -- --check` - `cargo check --manifest-path runner/Cargo.toml --locked --workspace` - `cargo test -p paperclip-runner-core --lib -- qualified_launch trusted_root commonjs`: 12 passed. The new tests are: - `an_artifact_under_an_immutable_trusted_root_runs_in_place_without_a_digest`: trusted-root hit, with no memfd, the same inode as the source, and no re-hash. - `an_artifact_outside_the_trusted_root_keeps_the_sealed_snapshot`: a path outside the root is sealed, and a wrong digest still fails. - `a_sibling_with_the_root_as_a_name_prefix_is_outside_the_root`: `rom2/` does not match `rom`. - `a_root_that_is_not_read_only_falls_back_to_the_sealed_snapshot`: the real probe refuses a writable root at startup. A per-artifact mount failure falls back, and a wrong digest still fails. - `the_real_mount_probe_rejects_a_writable_filesystem` - `symlink_and_parent_escapes_from_the_root_fall_back`: a directory symlink out of the root, a `..` path out of the root, and a final-component symlink (still refused). - `a_root_must_be_absolute_canonical_and_a_directory` - `without_a_trusted_root_launch_artifacts_are_sealed_and_hashed`: flag absent, behavior unchanged. - `host_assigned_executables_ignore_the_trusted_root` - `trusted_root_artifacts_execute_the_held_file_and_reopen_it_for_nested_launches`: Runner execs from the held file, and a child re-execs `$PAPERCLIP_VERIFIED_RUNTIME_EXECUTABLE`. Both report the source file as `/proc/self/exe`. - `cargo test -p paperclip-runner-core --test stdio_mcp --test process_supervisor`: 4 and 8 passed. - Ad hoc, not committed: a privileged container with a real loop-mounted squashfs. The real `fstatvfs`/`fstatfs` probe admitted a `ro` mount and refused a `ro,noexec` mount. The unit tests replace only that mount probe, because CI cannot mount filesystems. - Not verified: a run on an agent computer with the real erofs ROM, and the latency and memory savings there. The Cloud Launcher change that passes the flag is a separate follow-up. ## Risks - **This change needs review from a security owner before merge.** It removes the sealed copy and the per-launch digest for admitted artifacts. That relies on the host's assertion that the root is a digest-pinned immutable image, plus the descriptor checks above. - **Misconfiguration fails closed.** A wrong, writable, `noexec`, non-canonical or missing root only loses the speedup, and runnerd logs a warning. There is no global "trust everything" switch, and Runner never selects a root from the filesystem it finds. - **Residual trust.** On an admitted file, Runner no longer detects a ROM image that differs from what the launch profile expected. On the agent computer, the Launcher derives the expected digests from the same ROM. Another host that passes the flag must pin its image the same way. An attacker with root in the guest (who could write the backing block device or remount) is out of scope; such an attacker can already control runnerd. - **Allowlist.** Only erofs and squashfs are accepted, because they cannot be written through any mount. A read-only bind mount of a writable filesystem is refused. A ROM that changes to another filesystem type will silently fall back to the sealed path (slower, still safe). - No migration. Behavior is unchanged when the flag is absent. Older runnerd builds ignore the flag. ## Model Used - Claude Opus 5.5 (`claude-opus-5-5`), Anthropic, via Claude Code with tool use (shell, file edits, container builds). Extended reasoning was on. ## Checklist - [x] I have included a thinking path that traces from project context to this change - [x] I have specified the model used (with version and capability details) - [x] I have checked ROADMAP.md and confirmed this PR does not duplicate planned core work - [x] I have searched GitHub for duplicate or related PRs and linked them above - [x] I have either (a) linked existing issues with `Fixes: #` / `Closes #` / `Refs #` OR (b) described the issue in-PR following the relevant issue template - [x] I have not referenced internal/instance-local Paperclip issues or links (only public GitHub `#NNN` / `github.com/paperclipai/paperclip` URLs) - [x] My branch name describes the change (e.g. `docs/...`, `fix/...`) and contains no internal Paperclip ticket id or instance-derived details - [x] I have run tests locally and they pass - [x] I have added or updated tests where applicable - [x] I have updated relevant documentation to reflect my changes - [x] I have considered and documented any risks above - [ ] All Paperclip CI gates are green - [ ] Greptile is 5/5 with no open P2s, recommendations, or follow-ups - [x] I will address all Greptile and reviewer comments before requesting merge 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>