# Spec: Environment Variable Protection (Process-Level Env Scrubbing) Status: Draft Owner: PMG sandbox Related: `sandbox/util/dangerous.go` (`DANGEROUS_FILES`), `docs/sandbox.md` ## 1. Background Modern software supply chain worms increasingly steal credentials from the **process environment** rather than from files on disk. The SafeDep analysis of the Miasma / Mini Shai-Hulud toolkit () documents this directly: - The payload is **TypeScript executed via Bun**, with a build-time *"Env-scramble"* transform that rewrites `process.env.GITHUB_TOKEN` into `process.env[scramble("GITHUB_TOKEN")]`, hiding the variable **names** from static analysis. It skips only `NODE_ENV` and `TZ`. - A `Provider` abstraction harvests source-specific credentials from **AWS, Azure, GCP, Kubernetes, HashiCorp Vault, and password managers (1Password, Bitwarden)**, then a `Collector` + `Sender` chain exfiltrates them. - Persistence drops a **Python** hourly C2 agent (`GITHUB_MONITOR.py`). - Exfiltration rides **GitHub commit search / commits over `github.com:443`** — the same host PMG's npm profile already allowlists — so **network egress filtering cannot stop this exfil**. The only control that breaks the kill chain is *preventing the read* in the first place. When a developer runs `pmg npm install` (or `pip`, `uv`, etc.), any malicious install hook or transitive dependency inherits PMG's full environment, including `AWS_*`, `GITHUB_TOKEN`, `NPM_TOKEN`, `TWINE_PASSWORD`, and similar. PMG already blocks credential **files** by default (`DANGEROUS_FILES`); this spec extends the same default-deny philosophy to **environment variables**. ## 2. Goals and non-goals ### Goals - Scrub a default-deny list of sensitive environment variables from the child process environment before a package manager command is executed. - Make the deny list **configurable**, mirroring `DANGEROUS_FILES`: a built-in default that profiles can extend and selectively override. - Let each sandbox **profile re-allow ecosystem-specific variables** so package managers keep working without surprise friction (e.g. npm keeps `NPM_TOKEN`). - Work on **all platforms**, since it is plain environment filtering and does not depend on OS sandbox primitives (Seatbelt / Bubblewrap / Landlock). ### Non-goals (accepted risk for v1) - **We accept that a malicious payload run by a given ecosystem can steal that ecosystem's own publishing token.** A malicious JS package executed during `npm install` can still read `NPM_TOKEN` (the npm profile re-allows it), but **not** a PyPI token or an AWS key. Symmetrically, a malicious Python package cannot read `NPM_TOKEN` or `AWS_*`. This is a deliberate trade-off: the ecosystem's own auth token must be present for the package manager to function, and removing it would break legitimate publish/auth flows. - We do **not** attempt to defeat secrets read via other channels (process memory, `/proc`, files). Those are listed under Future Enhancements. - We do **not** introduce a full default-deny-all (allowlist-only) environment in v1. That is a future, higher-friction mode (see §9). ## 3. Design overview Two layers, exactly mirroring the `DANGEROUS_FILES` model: 1. **Built-in default deny list** — `DANGEROUS_ENV_VARS` in `sandbox/util`, a list of case-insensitive name glob patterns covering known credential variables plus broad catch-alls (`*_TOKEN`, `*_SECRET`, ...). The catch-alls are what defend against the *scrambled / novel variable name* technique: we match on the shape of secret-bearing names, not a fixed enumeration. 2. **Per-profile `environment:` section** — each sandbox policy may declare additional `deny` patterns and `allow` patterns. `allow` suppresses matching built-in or profile denies (allow always wins), letting each ecosystem re-permit the variables its package manager legitimately needs. Enforcement is a single chokepoint: after the sandbox policy is resolved in `executor.ApplySandbox`, the resolved environment policy is applied to `cmd.Env`, removing denied variables before the child process is spawned. `ApplySandbox` is already the shared entry point for both the guard and proxy flows and runs before the direct and PTY launch paths, so one integration point covers every package-manager child PMG spawns. ``` os.Environ() -> shim.FilterPMGFromEnv() (existing: strips PMG_SHIM_PATH, ~/.pmg/bin) -> mergeEnv(overrides) (existing) -> [cmd.Env set in runner] -> executor.ApplySandbox(): resolve policy cmd.Env = util.ScrubEnv(cmd.Env, allow, deny) <-- NEW apply OS sandbox -> exec child (direct / PTY / proxy) ``` ### Why enforcement is gated on sandbox being enabled To stay consistent with `DANGEROUS_FILES` (which only takes effect when the sandbox is enabled) and to honor "can be overridden by sandbox config," v1 enforces env scrubbing **only when the sandbox is enabled for the package manager**. If a profile is explicitly disabled for a PM, no scrubbing occurs — disabling the sandbox disables all of its protections, which is the existing, predictable contract. Making env scrubbing always-on regardless of sandbox state is called out as a future enhancement (§9) because it is independently valuable (it needs no OS sandbox support) but changes the current contract. ## 4. Configuration schema ### 4.1 Policy YAML (`sandbox/profiles/*.yml`) A new optional top-level `environment:` block on `SandboxPolicy`: ```yaml environment: # Extra variable-name patterns to scrub, in addition to the built-in # DANGEROUS_ENV_VARS default deny list. Case-insensitive globs. deny: - MY_CUSTOM_SECRET # Variable-name patterns to keep even if a built-in or profile deny would # otherwise scrub them. Allow always wins. Case-insensitive globs. allow: - NPM_TOKEN - NODE_AUTH_TOKEN - npm_config_* ``` Go types (in `sandbox/policy.go`): ```go type SandboxPolicy struct { // ... existing fields ... Environment EnvironmentPolicy `yaml:"environment" json:"environment"` } // EnvironmentPolicy controls which environment variables are scrubbed from // the child process. Deny extends the built-in DANGEROUS_ENV_VARS; Allow // suppresses matching denies (allow wins). Patterns are case-insensitive // name globs. type EnvironmentPolicy struct { Allow []string `yaml:"allow" json:"allow"` Deny []string `yaml:"deny" json:"deny"` } ``` Inheritance: `Environment.Allow` and `Environment.Deny` are unioned with the parent in `MergeWithParent` (same semantics as filesystem/network/process lists). No path expansion is needed in `ResolveProfile` (these are variable names, not paths), but the slices are deep-copied like the others. ### 4.2 `config.template.yml` Document the new section under the sandbox docs block, including the note about the accepted-risk trade-off and a pointer to this spec. No new top-level config key is required — env protection is part of the per-PM sandbox policy. ## 5. Built-in default deny list (`DANGEROUS_ENV_VARS`) Lives next to `DANGEROUS_FILES` in `sandbox/util/dangerous.go`. Case-insensitive name globs. Indicative starting set (to be finalized in implementation review): ```go var DANGEROUS_ENV_VARS = []string{ // Cloud providers "AWS_ACCESS_KEY_ID", "AWS_SECRET_ACCESS_KEY", "AWS_SESSION_TOKEN", "AWS_SECURITY_TOKEN", "AWS_*", "AZURE_*", "ARM_*", "GOOGLE_APPLICATION_CREDENTIALS", "GOOGLE_*", "GCP_*", "GCLOUD_*", // Package registry / publishing tokens "NPM_TOKEN", "NPM_AUTH_TOKEN", "NODE_AUTH_TOKEN", "TWINE_USERNAME", "TWINE_PASSWORD", "TWINE_*", "PYPI_*", "UV_PUBLISH_TOKEN", "FLIT_PASSWORD", "POETRY_PYPI_TOKEN_*", "POETRY_HTTP_BASIC_*", "GEM_HOST_API_KEY", "RUBYGEMS_*", "CARGO_REGISTRY_TOKEN", "CARGO_REGISTRIES_*", // VCS / CI "GITHUB_TOKEN", "GH_TOKEN", "GH_ENTERPRISE_TOKEN", "GITLAB_TOKEN", "CI_JOB_TOKEN", // Secrets managers "VAULT_TOKEN", "VAULT_*", // Misc high-value "DOCKER_PASSWORD", "DOCKER_AUTH_CONFIG", "SNYK_TOKEN", "CODECOV_TOKEN", "NPM_CONFIG__AUTH", "OPENAI_API_KEY", "ANTHROPIC_API_KEY", "HUGGING_FACE_HUB_TOKEN", // Broad catch-alls — defend against scrambled / novel secret names "*_TOKEN", "*_SECRET", "*_PASSWORD", "*_API_KEY", "*_APIKEY", "*_ACCESS_KEY", "*_PRIVATE_KEY", "*_CREDENTIALS", } ``` ### Protected essential variables (never scrubbed) A small hardcoded allowlist guards core process variables so a careless or broad profile `deny` cannot break execution. These are never scrubbed regardless of deny patterns: ``` PATH, HOME, USER, LOGNAME, SHELL, PWD, OLDPWD, TERM, TMPDIR, TEMP, TMP, LANG, LC_*, TZ, DISPLAY, HOSTNAME, NODE_ENV ``` (The broad catch-alls above do not match these names today; the protected set is a safety net against future or profile-supplied deny patterns.) ## 6. Per-profile allow lists (avoiding developer friction) Each restrictive profile gains an `environment.allow` block re-permitting only its ecosystem's legitimately required variables. This is the mechanism behind the accepted-risk trade-off in §2. - **`npm-restrictive.yml`** (npm, pnpm, yarn, bun, npx, pnpx): ```yaml environment: allow: - NPM_TOKEN - NPM_AUTH_TOKEN - NODE_AUTH_TOKEN - npm_config_* # npm lowercases config-derived vars - NPM_CONFIG_* - NODE_EXTRA_CA_CERTS ``` Result: a malicious JS install hook can read `NPM_TOKEN`, but `AWS_*`, `TWINE_*`/PyPI tokens, `GITHUB_TOKEN`, and `VAULT_*` remain scrubbed. - **`pypi-restrictive.yml`** (pip, uv, ...): ```yaml environment: allow: - TWINE_USERNAME - TWINE_PASSWORD - TWINE_REPOSITORY* - PIP_* - UV_* - POETRY_* ``` Result: a malicious Python package can read its PyPI publishing creds, but not `NPM_TOKEN` or `AWS_*`. - **`pnpm-restrictive.yml`**: same allow set as npm. - **`npx.yml`**: npm allow set (npx executes npm-ecosystem code). Each profile's allow list should be reviewed so it grants the **minimum** set of variables the package manager needs for auth, registry config, and TLS. ## 7. Matching semantics - Matching is on the variable **name** (the substring left of the first `=` in each `KEY=VALUE` entry). - Patterns are **case-insensitive** globs (reuse `sandbox/util` glob matching; Miasma-style scrambling targets conventionally uppercase names, but case-insensitivity removes a trivial bypass and matches lowercase `npm_config_*`). - An entry is **scrubbed** (removed entirely, not blanked) iff: `matches(effectiveDeny) AND NOT matches(allow) AND NOT isProtectedEssential`. - `effectiveDeny = DANGEROUS_ENV_VARS ∪ profile.environment.deny`. - `allow = profile.environment.allow`. Allow wins over deny. - Removal (vs. setting empty) is intentional: absence is the cleanest "not set" signal and avoids tools that treat empty-string specially. ### Proposed API (in `sandbox/util`) ```go type EnvScrubOptions struct { Allow []string // profile environment.allow (already merged) Deny []string // profile environment.deny (already merged) } type EnvScrubResult struct { Env []string // kept entries (KEY=VALUE) Removed []string // removed variable NAMES only (never values), for audit } // ScrubEnv removes sensitive variables from env per the built-in // DANGEROUS_ENV_VARS list extended by opts.Deny and suppressed by opts.Allow. func ScrubEnv(env []string, opts EnvScrubOptions) EnvScrubResult ``` This parallels `GetMandatoryDenyPatterns` and keeps all matching logic in `sandbox/util` where `DANGEROUS_FILES` already lives, so the linter and tests have a single source of truth. ## 8. Audit and observability - `ScrubEnv` returns the **names** of removed variables (never values). - `executor.ApplySandbox` logs the scrubbed count at info and the names at debug, and threads them into the existing sandbox `ExecutionResult` so they can be surfaced in the event log alongside other sandbox decisions. - Emitting "credential variable present and scrubbed during install" into the eventlog gives defenders a signal that a package run had access to (and was denied) sensitive variables — useful even when nothing malicious is observed. ## 9. Testing - `sandbox/util`: table-driven tests for `ScrubEnv` covering deny match, allow suppression, protected-essential preservation, case-insensitivity, glob catch-alls, and removal-vs-blank. Use `testify` `assert`/`require` per repo conventions. - `sandbox/policy_test.go`: `Environment` merge under inheritance (union of allow/deny, parent + child). - `executor`: env is scrubbed when sandbox enabled; untouched when the policy is disabled for the PM; PTY and direct paths both receive the scrubbed slice. - Profile fixtures: assert npm profile keeps `NPM_TOKEN` and drops `AWS_*` / `TWINE_PASSWORD`; pypi profile keeps `TWINE_*` and drops `NPM_TOKEN` / `AWS_*` (encodes the §2 accepted-risk contract as a regression test). ## 10. Rollout / compatibility - Backward compatible: profiles without an `environment:` block still get the built-in `DANGEROUS_ENV_VARS` default deny once sandbox is enabled. Existing configs need no change. - The built-in deny list is conservative for the package-manager context, but the broad catch-alls (`*_TOKEN`, etc.) may scrub a variable a niche build step relied on. Mitigation: the per-PM `environment.allow` escape hatch and clear audit logging of scrubbed names so the cause is obvious. - Document in `docs/sandbox.md`: the default deny list, the per-profile allow mechanism, and the accepted-risk trade-off. ## 11. Future enhancements Captured from the broader analysis; out of scope for v1 but natural follow-ups. 1. **Always-on (sandbox-independent) enforcement.** Scrub env even when the OS sandbox is unavailable or disabled, since env filtering needs no platform primitive. Highest-value extension; deferred only to avoid changing the current "sandbox off = no protection" contract without explicit opt-in. 2. **Default-deny-all (allowlist-only) env mode.** An opt-in strict tier (`environment.default_deny: true`) that starts from an empty environment and passes only an allowlist (`PATH`, `HOME`, `npm_config_*`, proxy/CA vars, ...), implemented via `--clearenv`/`--setenv` on Linux. Best suited to CI, where the environment is narrow and knowable. Strongest defense against novel variable names but higher friction. 3. **Linux `/proc` hardening.** The Miasma worm dumps GitHub Actions runner memory via `/proc` to obtain "secrets not exposed as env vars." Pair env scrubbing with PID-namespace isolation (already `unsharePID: true`) plus masking other processes' `environ`/`mem` (e.g. `hidepid`/minimal proc mount) so scrubbing cannot be sidestepped through `/proc`. 4. **Sandbox-detection hardening.** Miasma fingerprints analysis environments via known fake env vars; ensure PMG does not inject identifiable markers into the child environment that aid evasion. 5. **Audit-only mode.** A non-enforcing mode that logs which sensitive variables *would* be scrubbed, to size impact before turning enforcement on. 6. **Egress note (defense-in-depth only).** Network allow/deny is explicitly *not* a primary control for this threat because exfil rides allowlisted `github.com`; keep it as layered defense, not a substitute for scrubbing.