Update Bubblewrap tests to schema 0.9

[Elliot (theelliotm)]

📖 Description

Updates the Bubblewrap test suite to schema 0.9.0-alpha, keeping 0.7/0.8 coverage for legacy compatibility and retiring the 0.6 cases.

Why 0.9 fixes #1273. Below 0.9 a Bubblewrap container receives no environment at all (--clearenv with nothing put back), so RHEL's bash falls back to a fabricated PATH that omits /usr/sbin — and the proxy test's iptables invocation fails to resolve. Schema 0.9 introduces the backend default environment block, which supplies a PATH that includes the system sbin directories. Thanks to this + the proxy rework below, the test now passes.

Proxy rework. run_bwrap_network_proxy_test.sh now starts a second unix-test-proxy as the real loopback endpoint, alongside the existing control listener. The legacy builtinTestServer cases stay on 0.7/0.8, where they still belong.

Config moves: five 0.6 configs rebased to 0.7 (legacy proxy shape, no slirp4netns needed), the rest to 0.9. Also fixes a silent false-pass in bubblewrap_network_firewall_cidr.json.

Added coverage: https://github.com/microsoft/mxc/actions/runs/36192718659/job/108266579735

• e2e_bubblewrap_characterization.rs: a policy grant is not adopted as the working directory; a relative process.cwd is anchored to the sandbox root from 0.9 (asserting cwd and HOME agree); a missing command fails promptly rather than hanging.
• linux-bubblewrap.test.ts: two 0.9 proxy tests (routing through runtimeConfig.networkProxy, and egress confined to the proxy endpoint). The existing proxy block was migrated 0.6 → 0.7 and relabeled as the legacy shape.

🔗 References

Resolves #1273

🔍 Validation

CI test shows all green for bubblewrap:

Run from the Windows checkout:

• cargo fmt -p wxc_e2e_tests -- --check — clean
• npx tsc --noEmit (sdk/node/tests/integration) — clean for linux-bubblewrap.test.ts; the remaining errors are pre-existing in wslc-state-aware.test.ts, which this PR does not touch
• All 309 versioned tests/configs/*.json validated against schemas/stable with AJV, honoring config-validation-exemptions.json — 0 problems
• bash -n on both changed shell scripts — clean

✅ Checklist

• Signed the Contributor License Agreement
• Linked to an issue
• Updated documentation (if applicable)
• Updated Copilot instructions (if build, architecture, or conventions changed)
• If this PR changes Cargo.lock, the dependency-feed-check check passes (see docs/pull-requests.md)

📋 Issue Type

• Bug fix
• Feature
• Task

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[Copilot]

Copilot review overview

🟡 Changes recommended

The missing-command regression test lacks a host-side timeout and can hang the entire test job.

Get a fresh assessment by requesting another Copilot review.

Review effort: Balanced
Findings: 1

Open (1)

• Add a host-side timeout to prevent the hang test from hanging · New

What changed in this PR

Updates Bubblewrap tests for schema 0.9 while preserving legacy 0.7/0.8 coverage.

Changes:

• Migrates applicable Bubblewrap configurations to schema 0.9.
• Reworks proxy tests around runtimeConfig.networkProxy.
• Adds characterization tests and updates backend documentation.

File	Description
tests/​scripts/​run_bwrap_network_test.sh	Updates legacy firewall test labels to 0.7.
tests/​scripts/​run_bwrap_network_proxy_test.sh	Adds a real loopback proxy endpoint for 0.9 tests.
tests/​configs/​linux_process_default.json	Moves default process test to 0.9.
tests/​configs/​linux_process_abstract.json	Moves abstract process test to 0.9.
tests/​configs/​bubblewrap_network_proxy_namespace.json	Adopts the 0.9 proxy-only policy.
tests/​configs/​bubblewrap_network_proxy_egress_denied.json	Tests 0.9 proxy egress confinement.
tests/​configs/​bubblewrap_network_proxy_connect.json	Migrates CONNECT coverage to the 0.9 proxy form.
tests/​configs/​bubblewrap_network_proxy_builtin.json	Rebases legacy proxy coverage to 0.7.
tests/​configs/​bubblewrap_network_proxy_blocklist.json	Rebases legacy blocklist coverage to 0.7.
tests/​configs/​bubblewrap_network_proxy_allowlist.json	Rebases legacy allowlist coverage to 0.7.
tests/​configs/​bubblewrap_network_firewall.json	Rebases legacy firewall coverage to 0.7.
tests/​configs/​bubblewrap_network_firewall_cidr.json	Ensures iptables resolution and detects false passes.
tests/​configs/​bubblewrap_network_block.json	Rebases legacy network-block coverage to 0.7.
tests/​configs/​bubblewrap_filesystem.json	Moves filesystem coverage to 0.9.
tests/​configs/​bubblewrap_basic.json	Moves basic Bubblewrap coverage to 0.9.
src/​testing/​wxc_e2e_tests/​tests/​e2e_bubblewrap_characterization.rs	Adds working-directory and missing-command characterization.
sdk/​node/​tests/​integration/​linux-bubblewrap.test.ts	Adds Node integration coverage for 0.9 proxy behavior.
docs/​schema.md	Documents Bubblewrap’s default working-directory behavior.
docs/​bwrap-support/​bubblewrap-backend.md	Documents 0.9 proxy configuration and legacy behavior.

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[Copilot]

Copilot review overview

🟡 Changes recommended

The new Rust test does not compile due to a missing import, and the deadline helper can still block indefinitely.

Get a fresh assessment by requesting another Copilot review.

Review effort: Balanced
Findings: 1 · 1 · 2

Open (4)

• Missing import causes Rust E2E test compilation failure · New
• Unbounded output joins can hang past the termination deadline · New
• Correct networkProxy schema version support and migration details · New
• Document versioned HOME environment behavior accurately · New

Resolved since last review (1)

• Add a host-side timeout to prevent the hang test from hanging

[Copilot]

Copilot review overview

🟡 Changes recommended

Cleanup can signal reused PIDs, and the Node proxy tests do not gate on the complete host capability probe.

Get a fresh assessment by requesting another Copilot review.

Review effort: Balanced
Findings: 1

Open (1)

• Clear reaped PIDs to make cleanup idempotent · New

Resolved since last review (4)

• Missing import causes Rust E2E test compilation failure
• Unbounded output joins can hang past the termination deadline
• Document versioned HOME environment behavior accurately
• Correct networkProxy schema version support and migration details

Previously missed (1)

In code that hasn't changed since last review

Use complete proxy network capability check before skipping tests

sdk/​node/​tests/​integration/​linux-bubblewrap.test.ts:215

This checks only that a slirp4netns path exists, but proxy-only startup also requires an executable slirp plus usable unshare, nsenter, iptables, and ip6tables. A host missing any of those passes this gate and fails both tests as an environmental error. Use the existing fail-closed getPlatformSupport().bubblewrapNetwork.proxyEnforcement capability result, which probes the complete dependency set, to decide whether to skip.

[Copilot]

Copilot review overview

🔵 Needs a closer look

The Bubblewrap documentation incorrectly applies the loopback-only restriction to legacy hostname and routable proxy URLs.

Review effort: Balanced
Findings: None

Resolved since last review (1)

• Clear reaped PIDs to make cleanup idempotent

Previously missed (1)

In code that hasn't changed since last review

Overstated loopback requirement for legacy proxy URLs

docs/​bwrap-support/​bubblewrap-backend.md:678

This loopback requirement is only true for runtimeConfig.networkProxy. Legacy network.proxy.url still accepts hostname/routable endpoints and pins them into the sandbox (the retained schema-0.8 hostname case in tests/scripts/run_bwrap_network_proxy_test.sh:400-475 exercises exactly that). As written, this now incorrectly tells 0.6–0.8 users that every external proxy must listen on loopback; scope the restriction to the directional field and preserve the legacy URL behavior.

[Copilot]

Copilot review overview

🔵 Needs a closer look

The new schema documentation incorrectly presents default HOME behavior as unconditional despite explicit environment overrides.

Review effort: Balanced
Findings: None

Previously missed (1)

In code that hasn't changed since last review

Clarify HOME behavior with explicit process.env and cwd

docs/​schema.md:285

This overstates the HOME behavior. In 0.9, an explicit process.env with inheritDefaultEnv: false is used verbatim, so cwd does not necessarily become HOME; similarly, callers may explicitly set HOME even when cwd is absent. Describe this as the backend default rather than an unconditional result.

[Jeff Whiteside (jsidewhite)]