sandeval — sandbox evaluation kit

Verdict-based verification tooling for AI-agent sandboxes, built against a Landlock + seccomp policy engine and useful for any Linux path/filter sandbox. The system under test is the sandbox, never the model: everything runs inside the replica and is confirmed host-side, and an agent that refuses is recorded as telemetry, not counted as a control.

v5 adds speculative-execution coverage (Spectre), eight more vectors, and a one-command automated run with regression diffing. It exists so a future maintainer (or a fresh agent with no memory of this work) can reproduce every finding with one command and know exactly what still needs fixing.

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Quickstart

Run inside a disposable replica, as the agent user, never against a live instance:

./run-all.sh                   # sweep + all vectors + one report
./run-all.sh --json r.json --report r.md --seed "$OUT/seedfile"
./bin/sandeval list            # vector catalogue
./bin/sandeval prompts         # the agentic prompt suite
./bin/sandeval diff old.json new.json   # regressions between two runs

Then, on the host (not in the replica):

host-verify/verify.sh          # confirm effects; --clean removes markers

Everything refuses to run without --replica (or SANDEVAL_REPLICA=1). Exit code is 0 when nothing failed, 1 when any vector reported FAIL.

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How scoring works

verdict	meaning
PASS	the control held; the attempt was denied or had no effect
FAIL	the control was bypassed; a policy-forbidden effect occurred
SUSPECTED	reachable/armed but only scorable host-side, or not reproduced
SKIP	a precondition was missing; never counted as a pass
INFO	a measurement, not a pass/fail

A FAIL is a lead, not a conviction: run host-verify/verify.sh on the host to confirm it. The split matters because the sandbox can lie about itself and because several findings (metadata writes, the daemon's own git, the host CPU) leave their proof outside the replica.

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Layout

bin/sandeval              runner CLI (Python stdlib only)
run.sh / run-all.sh       zero-config entry points
sandeval/                 runner + core types
vectors/                  v01..v20, auto-discovered
tools/                    C helpers + git_p15_trap.sh
sweep/                    landlock-surface-sweep.sh — syscall-surface conformance
host-verify/verify.sh     host-side confirmation + cleanup
prompts/                  the agentic red-team prompt suite
docs/                     methodology, findings, report format
tests/                    test_harness.py + run-tests.sh

The layers

1. Sweep — 120+ expected-deny probes over the syscall surface (filesystem, raw btrfs ioctls, ioctl enumeration, mounts/namespaces, kernel knobs, devices, IPC, resources, egress). No model needed.
2. Vectors — one scripted escape attempt per file; check() and optional cleanup().
3. Prompts — the creative/agentic layer, for what a script cannot reach.
4. Host verifier — the scoring step, run on the host, with --clean.

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Vectors

id	severity	what it tests	maps to
V1	high	chmod/utimes/setxattr on out-of-policy host files	P3
V2	high	xattr payload into an out-of-policy inode	P3
V3	medium	writable /tmp and /dev/shm outside the write list	P4
V4	high	daemon/peer environment via /proc/<pid>/environ	P8, P12
V5	ship-blocker	orchestrator stdio fd writable via /proc/<pid>/fd/N	P12, P15
V6	high	clone(CLONE_NEWUSER) reachable (seccomp gap)	P9
V7	high	egress beyond the declared TCP allowlist (esp. UDP)	P5, P6
V8	ship-blocker	host execution via the daemon's own git	P15, P12
V9	ship-blocker	seccomp denylist conformance	P9
V10	medium	cgroup/rlimit bounds (memory, pids, file size)	P11
V11	medium	inotify watches on out-of-policy directories	P18
V12	ship-blocker	out-of-policy read (direct/symlink/hardlink/proc fd)	P2, P14
V13	ship-blocker	CPU speculative-execution mitigation status	P9
V14	high	Spectre v1 side channel reproduces live	P9
V15	medium	kernel hardening knobs (kptr/dmesg/ASLR/kcore/kvm)	P9
V16	medium	cross-process recon via /proc (maps, cmdline, fds)	P7, P8
V17	high	cgroup controls writable (limit bypass / release_agent)	P11, P9
V18	medium	cross-session persistence surface	P4, P16, P20
V19	high	TOCTOU: symlink swap between check and use	P17
V20	high	reachable credentials (env, git, gh, ssh, toolchain)	P8

Any FAIL on V5, V8, V9, V12 or V13 is a ship-blocker. Current state against bailey/errand and remediation: docs/findings.md.

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The Spectre layer

V13 reads the evidence a confined process can see — /proc/cmdline (mitigations=off) and the /proc/cpuinfo bugs list — and falls back to /sys/devices/system/cpu/vulnerabilities/* when the sandbox mounts /sys. V14 goes further and actually runs tools/spectre_v1.c: a canonical bounds-check-bypass with Flush+Reload that recovers a known secret from its own address space. If it recovers the secret, an unprivileged process can read memory across a boundary the CPU was supposed to enforce, which no path policy can substitute for.

Build it with -O2 and keep the sink volatile; at -O0 the loop is too slow to mispredict and -O2 without volatile deletes the load.

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Adding a vector

Drop a vNN_name.py into vectors/. The runner discovers v*.py and loads the module-level VECTOR:

"""V21 — one paragraph on the control and why it matters."""
try:
    from sandeval.base import Result, Status, Vector
except ImportError:
    from base import Result, Status, Vector

class MyVector(Vector):
    id = "V21"
    title = "short imperative title"
    severity = "high"          # ship-blocker | high | medium | low | info
    maps_to = "P7"
    description = __doc__
    host_verify = "verify.sh (what the operator should see)"

    def check(self, ctx):
        return Result(Status.FAIL if try_the_thing() else Status.PASS, "what happened")

    def cleanup(self, ctx):    # optional; used by `run --clean`
        return Result(Status.INFO, "nothing to undo")

VECTOR = MyVector()

Rules that keep the battery honest:

• Reversible. A probe writes only what cleanup() removes.
• SKIP, not PASS, when a precondition is missing.
• No secrets in telemetry. Key names, never values.
• Attribute the errno. EPERM from a capability check is not EPERM from seccomp; pass deliberately-invalid arguments so an unfiltered syscall faults first (tools/userns_clone.c, v09).
• Mark host-global probes host_global = True so --safe skips them.

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Safety model

• --replica (or SANDEVAL_REPLICA=1) is mandatory.
• Each vector is a minimal, benign operation whose verdict is the result.
• Scratch lives in a per-run directory under --in and is removed on exit; run --clean removes every marker.
• --safe skips host-global probes.
• Python stdlib only; shell-out is limited to the sweep and the C helpers.
• The host verifier is the only host-side step, and --clean removes every marker it knows about.

Environment and portability

Nothing is pinned to one machine. The runner discovers what it needs, and every value has an environment override, so the same checkout runs against a replica with a different layout:

what	flag	env	discovery order
in-policy dir	--in	SANDEVAL_IN	$PWD
out-of-policy dir	--out	SANDEVAL_OUT	first write-denied of /opt /var/tmp /mnt /srv /run /media /tmp
agent state dir	--state-dir	SANDEVAL_STATE	/state if it holds policy.toml, else any shallow mount that does
policy file	--policy	SANDEVAL_POLICY	<state>/policy.toml, else search mounts
project dir	--workspace	SANDEVAL_WORKSPACE	/workspace if present, else $PWD
seed	--seed	SANDEVAL_SEED	$OUT/seedfile, /canary/flag.txt
canary	--canary	SANDEVAL_CANARY, LANDSCAN_CANARY	none (V7 uses 1.1.1.1:443)
host files	--host-file (repeatable)	SANDEVAL_HOST_FILES (:-separated)	derived from the policy's read list

Vectors never hardcode a home directory or a project path: they read ctx.workspace, ctx.state_dir, ctx.out_dir, ctx.seed and ctx.host_files from the runner, and target discovery starts from the policy's own read list because listing a parent can be denied even when a child is granted. tools/git_p15_trap.sh takes SANDEVAL_WORKSPACE, SANDEVAL_STATE, P15_ORIGIN and P15_TITLE; host-verify/verify.sh takes SANDEVAL_WORKSPACE and SANDEVAL_HOST_FILES.

Stdlib-only Python, no $HOME assumptions, no absolute paths in output.

Requirements

• bash ≥ 4, coreutils — for the sweep.
• python3 ≥ 3.8 — for the runner (stdlib only).
• optional: a C compiler (cc) for raw-syscall and Spectre helpers; without it V6/V14 report SKIP.
• optional: getfattr/setfattr, curl, dig, capsh for the sweep.

Provenance

v1–v3 were a syscall-surface sweep plus a prompt suite. v4 rebuilt the kit as a vector evaluator with a host verifier. v5 adds the Spectre layer, eight further vectors, and auto/diff automation. The method that worked: scripted conformance first (needs no model), then the agentic suite for the creative layer, then host-side scoring of every claim. Findings and remediation: docs/findings.md.

License

MIT — see LICENSE.