# Spec decisions log This file tracks implementation arbitrations *on top* of the frozen spec (`Projects/Mimic — Spec.md` in the RT-SecondBrain vault). Format: one entry per decision, newest first. --- ## 2026-05-21 — Team kickoff decisions ### D-001 — SOC collaboration hypothesis **Context.** Devils-advocate flagged the sociological assumption that SOC analysts will cote in the live cockpit. **Decision.** Hypothesis accepted as-is. No paper PoC. Risk owned by lead RT. ### D-002 — Mimic deployment location **Context.** Spec §6 NF-network did not pin where Mimic is physically deployed. **Decision.** Mimic runs on RT infrastructure. SOC client connects through the existing RT reverse proxy (Caddy, out of Mimic scope). Mimic → Mythic / Home C2 through outbound VPN. RT R&D (TTP library, stealthy variants) never sits on client premises. ### D-003 — Authentication strategy **Context.** Spec mentions OIDC Keycloak but lab onboarding cost is high. **Decision.** v1 ships **local auth** (username/password, bcrypt, Flask server-side sessions). v2 adds Keycloak OIDC. The RBAC model is **group-based from day one**, so OIDC will map claims to existing groups without touching application code. SOC sessions remain a distinct mechanism (`soc_session.token_opaque` bcrypt hash, clear token out-of-band). ### D-004 — C2 credential storage (T2) **Context.** Engagement.config_json (encrypted JSON column) vs dedicated table. **Decision.** Dedicated table `c2_credential (id, engagement_id, c2_type, config_json_fernet, version, created_at, retired_at)`. Active row per engagement = `retired_at IS NULL`, highest version. Rotation = insert + retire previous. Fernet key in env, never in DB. ### D-005 — Cleanup template variable sources (T3) **Context.** Jinja `{{outputs.X}}` source ambiguity. **Decision.** Two accessors: - `{{outputs.text}}` → `run_step.output_text` (stdout/UTF-8 text). - `{{outputs.blob("")}}` → reads from `output_blob_ref`, hard cap **10 MB** (consistent with F8 evidence limit), UTF-8 decoding with latin-1 fallback, silent refusal + log entry if the blob is non-decodable. `regex_extract` always operates on the resulting string. ### D-006 — SOC session token storage (T4) **Context.** `soc_session.token_opaque` storage form. **Decision.** bcrypt hash. Clear token generated server-side at session creation, returned **once** in the API response, delivered out-of-band to the SOC analyst. Never re-displayable. ### D-007 — Reverse proxy scope **Context.** Mimic exposure to internet for SOC client access. **Decision.** Reverse proxy (Caddy + TLS + IP allowlist) handled by existing RT infrastructure. Mimic ships an HTTP listener on localhost only; the deployment playbook wires it behind the existing proxy. ### D-008 — Group-based RBAC vs spec F11 fixed roles **Context.** Spec F11 declares 3 fixed roles (`rt_operator`, `rt_lead`, `soc_analyst`) with an explicit permission matrix. Sprint 0 plan (B0.6, D-003) introduces `group` / `permission` / `group_permission` / `user_group` tables to prepare OIDC v2 claim-to-group mapping without code change. **Decision.** Group-based model accepted as an implementation *layout*, **not** a scope extension: - The 3 spec roles MUST exist as the 3 seeded groups at bootstrap (`rt_operator`, `rt_lead`, `soc_analyst`). - The F11 permission matrix is the canonical source: groups receive exactly the permissions of their matching role; no custom permissions UI v1. - Custom groups, group editing UI, or per-engagement group overrides = OUT of v1. - Any drift between seeded group permissions and the F11 matrix is a spec violation, not a configuration choice. ### D-010 — Ansible for the deployment playbook **Context.** Spec §7 names `Docker` only on the deploy line, but D-007 references a "deployment playbook" wiring Mimic behind the existing reverse proxy. The RT team uses Ansible for infrastructure automation across projects. **Decision.** Deployment artifacts are Docker images (built in repo) plus an Ansible playbook (lives outside the application repo, in the RT infra repo). Mimic itself ships only the Dockerfile and a sample compose for dev; production roll-out is Ansible-driven. The README stack line is updated accordingly. ### D-009 — `ttp_version` table forbidden (H32 reaffirmed) **Context.** Sprint 0 plan (B0.2) lists `ttp_version` among the initial tables. Spec hypothesis **H32** explicitly excludes this: *"Snapshot de rejouabilité = `run.snapshot_json` uniquement (pas de table `ttp_version` séparée — simplification MVP)"*. **Decision.** Drop `ttp_version` from the initial migration. The `ttp.version` column (informational, §8) is kept. Replayability lives **solely** on `run.snapshot_json`. Re-introducing `ttp_version` requires explicit spec amendment through the team-lead. ### D-011 — `regex_extract` Jinja2 filter semantics (resolves Q-001) **Context.** D-005 introduced `regex_extract` on Jinja templates without fixing its match-mode, no-match behaviour, group selection, or engine flavour. Backend B0.5 (templating sandbox) is starting and needs a frozen signature. **Decision.** - **Engine** — `google-re2` (D-005 reaffirmed). Linear-time, no backrefs, OPSEC-safe (no ReDoS). - **Match mode** — first match only. - **No-match** — raise `TemplateError("regex_extract: no match for //")`. No silent fallback. Drifting cleanup templates must fail loudly at step run time, not on next mission. - **Group selection** — defaults to capture group 1; positional fallback to the full match when the pattern has no groups; named groups via `name=""`. - **Signature** — `regex_extract(text, pattern, *, group=1, name=None)`. - **Rationale** — ATR/Caldera compatibility is not an objective (D-005). Fail- fast > silent string corruption when a cleanup template touches a host with unexpected output shape. ### D-012 — `output_blob_ref` storage layout (resolves Q-002) **Context.** §8 declares `run_step.output_blob_ref` without specifying pool, quota, format, or path. H20 says "local disk v1" only. Sprint 0 needs the layout locked because B0.5 already references `{{ outputs.blob(...) }}`. **Decision.** - **Two separate pools** — - `MIMIC_BLOB_ROOT` (default `/var/lib/mimic/blobs/`) — binary outputs from `C2Connector` polling. **Content-addressed** layout: `//.gz` where `aa`/`bb` are the first two byte-pairs of the sha256 hex digest. gzip systematically; raw stored bytes never on disk. - `MIMIC_EVIDENCE_ROOT` (default `/var/lib/mimic/evidence/`) — user-uploaded evidence files (F8). Flat layout `/.`, no compression. - **Cap per blob** — 10 MB (consistent with F8 and D-005). - **Quota** — no in-app global quota v1. OS-level monitoring via Prometheus node_exporter. F12 archival pipeline will own retention/purge post-sprint-0. - **Filesystem permissions** — `0750`, owner the `mimic` system user. - **Rationale** — CAS deduplicates repeated C2 outputs (same `whoami`, same `Get-Process` snapshot) for free. Evidence stays flat because uploads are one-shot and tied to an engagement scope that we want to archive whole. Two pools mean we can wire independent quotas / retention policies in v2 without migration. #### Resolved open questions - Q-001 → D-011. - Q-002 → D-012.