feat(run): seccomp loopback egress guard (Linux)#232
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Cross-platform run-audit channel: firma-core RunAuditEvent/RunAuditMessage, sidecar out-of-band ingest listener, and CLI wiring that binds the control socket when firma run provisions one. Also migrate two Windows-only allow(unsafe_code)/expect_used lints to expect(...) with reasons.
Add the seccomp connect-notify egress guard and wire it into the bwrap runtime: in-sandbox installer/runner (__egress-guarded-run), host-side supervisor, routing env overrides, and the bwrap entrypoint. Add loopback and raw TCP e2e coverage with a local TCP proxy and audit snapshots.
This was referenced Jul 6, 2026
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Add deterministic coverage for gaps in the seccomp loopback guard: - classify/is_loopback edges: IPv4-mapped non-loopback allowed, unspecified addresses allowed, DNS port allowed, empty allow-list blocks all loopback, external IP on unsanctioned port allowed. - parse_sockaddr boundaries: exact AF_INET/AF_INET6 length cutoffs, empty buffer, big-endian port, IPv4-mapped-loopback parses as V6 and blocks. - classify_notification: IPv6 loopback block, AF_UNIX allow, sanctioned DNS port allow. - BPF arch/nr jump routing. - SCM_RIGHTS fd transfer roundtrip and the no-fd error path. - start() binds the control socket and Drop tears it down.
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What
Linux
bwrapseccompuser-notifyfilter that traps the agent'sconnect(2)and blocks direct connections to any loopback address (127.0.0.0/8,::1, IPv4-mapped) except the proxy bridge and DNS stub ports, returningEACCES. Catches direct sockets that bypassHTTP_PROXY.Each block is reported to the Sidecar over the audit channel (PR #231) and recorded as a signed
DENY/network.loopback/loopback blockedevent, visible infirma monitor. Deny path is race-free; allow path usesSECCOMP_USER_NOTIF_FLAG_CONTINUE. Fails open with a warning if user-notify is unavailable — the private netns already isolates the agent, so the guard is defense-in-depth plus a direct-socket audit trail.Stack
Based on #231 (audit channel). Part of the fir-383 split replacing #216.