glove/docs/threat-model.md

Glove threat model

Security objective

Glove limits the authority of an untrusted agent process to explicitly selected files, environment variables, network destinations, and MCP tools. It also records policy decisions and, for managed Linux sessions, produces authenticated resource-enforcement receipts.

Glove is a containment boundary, not a prompt-injection detector or a complete host security boundary.

Trust boundaries

Component	Trust assumption
Agent process and model output	Untrusted
Agent-supplied JSON-RPC and terminal input	Untrusted
Glove control, policy, and sandbox code	Trusted
Local policy, launch templates, and approval records	Trusted operator input
Project files, repository configuration, and agent instructions	Untrusted; never machine-setup authority
MCP upstream servers	Trusted host processes; not sandboxed by Glove
Sage controller	Authenticated peer, but not authority for raw paths, exposure administration, or host mutation
Operating-system kernel and platform sandbox	Trusted and patched
Other processes under the same host user	Outside the strong integrity boundary

Enforced properties

Area	Enforcement
Filesystem	Deny-default sandbox; explicit read/write grants; descriptor-based path resolution; link, ownership, identity, and overlap checks
Network	Linux private network namespace with no external route; offline agents cannot create Internet sockets, while online agents reach only an authenticated audited host proxy through a private-loopback listener and inherited Unix descriptor channel; exact macOS egress rules
Process surface	Linux PID/user/IPC/UTS namespaces; macOS deny-default SBPL
Environment	Minimal environment plus named grants
Tool access	Qualified allow-list and configured argument rules before upstream dispatch
Protocol	Bounded JSON-RPC frames, strict decoding, initialization checks, and timeouts
Resources	Linux cgroup CPU/memory/PID limits, watchdog wall time, filesystem quotas, and aggregate terminal-output accounting
Audit	Agent-inaccessible JSONL destination; HMAC-chained managed-session terminal receipts
Remote plans	Identifier-only canonical plan matched against owner-local policy and dual digests; exact untagged container name@sha256 identity; isolated Ed25519-only SSH artifacts; receive-inclusive monotonic TTLs; a configured remote backend remains construction-only and grants no launch authority
Daemon lifecycle	Fixed local user-service name, protected config and executable paths, shell-free service-manager invocation, and authenticated readiness checks
Recovery	Append-only state, exact replay, process identity beyond PID, and fail-closed reconciliation

Security-relevant append, policy, setup, and receipt failures terminate or reject the operation rather than silently reducing enforcement.

Residual risks

Risk	Consequence	Required mitigation
Allowed-tool abuse or prompt injection	An agent can perform malicious operations that remain within an allowed tool's semantics.	Narrow tool and argument policy; upstream semantic authorization.
Unsandboxed upstream compromise	A vulnerable MCP server can act with its host-user authority.	Run upstreams in separate sandboxes or move them behind a hardened service boundary.
Same-user host tampering	A peer process can rewrite the general JSONL log or unkeyed session state and may read shared local secrets.	Isolate the service identity; use asymmetric signing or protected key storage; authenticate general logs.
Linux kernel escape	A kernel vulnerability can cross namespace or seccomp boundaries.	Patch hosts and add an outer VM/container boundary where required.
Hostile active content	Documents, archives, installers, and malware can exploit a process that parses or executes them.	Use the hostile-content analysis profile for offline data inspection; require a disposable VM-grade boundary for active-content execution.
macOS resource exhaustion	The Sage six-limit resource contract is not implemented on macOS.	Add enforceable CPU, memory, PID, wall-time, disk, and output controls with receipts.
Host egress broker compromise	A defect in the host relay or authenticated proxy could mishandle an approved connection.	Keep the relay target fixed to the per-run proxy, use exact host/port grants, cap concurrent relays, and retain proxy audit evidence.
Retained-change apply disabled	The local atomic/recovery primitive is not a production authorization boundary by itself.	Keep capability 0 until the independent Ed25519 helper/verifier, local RPC/audit path, startup sweep, host-space policy, and Sage-to-parent isolation are configured and tested.
Bundle expansion absent	A verified bundle file is not yet converted into harness-native prompt context.	Add bounded, format-aware extraction and receipt-bound launch inputs.
Refinement evidence scope	Glove does not currently own harness token accounting or a session-indexed durable tool/security/egress event stream suitable for fixture assertions.	V1 omits token and audited-event assertions. Never accept model-reported counts or event identifiers; add them only after those observations have a Glove-owned exact-session source.
Remote backend is non-operational	Validated SSH artifacts and executor health can be mistaken for an enforceable remote sandbox.	Keep lifecycle, adapter, resource, and receipt capabilities absent; require executor self-measurement and independent enforcement verification before enabling launch.
Dependency or compiler compromise	Build-time code or toolchain compromise can alter enforcement.	Pin dependencies by immutable digest, verify releases, and use reproducible builds.
Protocol parser defects	Malformed input may expose untested parser behavior.	Add fuzz targets and a maintained adversarial corpus.

Assumptions

The security claims require:

• the operator controls policy, runtime templates, protected directories, and the Glove executable;
• the host kernel and platform sandbox behave as documented;
• no agent-visible path contains control secrets, journals, or audit output;
• machine setup and project enrollment are performed by the local operator, outside any remote request or project-provided configuration;
• allowed tools and upstream servers are appropriate for the deployment;
• Linux cgroup v2, namespace, mount, seccomp, and quota prerequisites are available when managed-session capabilities are advertised;
• callers use capability discovery and do not infer support from source code, platform, generated SSH artifacts, executor health, or a non-null runtime object alone.

Deployment review

Before enabling an agent, record:

1. Which host paths and environment variables are visible?
2. Which MCP tools and argument forms are allowed?
3. Which upstream processes run outside the sandbox?
4. Is network access denied or restricted to exact destinations?
5. Are audit and control files inaccessible to the agent and other principals?
6. Are all advertised resource controls enforced on the selected backend?
7. Are live host writes absent, and is any future change apply independently authorized?
8. Is the host patched and, where needed, enclosed by a stronger VM boundary?

Remote Sage launch should remain gated whenever any mandatory capability or approval class is unavailable.