Ctf Writeup

ctf-writeup

Convert a CTF engagement notebook into a published Jekyll post. The notebook is a command log (what was run); the writeup adds the reasoning log (why) — which lives only in the operator's head and must be drawn out by interview. The operator answers questions; this pipeline does everything else and never invents facts.

Scripts live beside this file: scripts/nbdump.py, scripts/linkcheck.sh, templates/post.md. Reference them by absolute path from the skill directory.

Golden rules (non-negotiable)

1. No fact from memory. Two classes of fact:
   • Internal (commands, outputs, creds, flags): transcribed from the notebook. Do not annotate with (cell N) markers — they rot. Provenance is implicit.
   • External (MITRE IDs, CVEs, error semantics, exam rules, tool URLs): fetch and cite the source URL, or omit. Never recall from memory.
2. Verify or omit — including links. HTTP-check every URL. Harvest the operator's own links verbatim (see Step 1); any link you add must resolve or be left ToolName — source not identified. A fabricated repo URL is the #1 silent failure.
3. Only tag techniques whose official definition matches. Pull the ATT&CK page, read the definition, tag only if it fits. Add a "not tagged, and why" note for rejected ones. (Pilots: T1505.003 Web Shell ≠ one-shot reverse WAR; T1110.003 Password Spraying needs many accounts, not one.)
4. Impersonal voice. No first person (I/we/my) and no reader-addressing "you". "The share was writable, so a payload was dropped" — not "I dropped a payload". Applies to narrative, 🧠 reflections, and lessons alike. Reflections stay honest and specific but read as abstract observations.
5. Unsourceable claim → mark it, never assert. Use > ⚠️ UNVERIFIED:.
6. Verbatim or prose — never a reconstructed transcript. Every fenced console/code block must be copied from a notebook cell (code source, cell output, or a markdown cell holding a pasted transcript). Do not synthesize a block, or re-port a block from one stage into another to fill a gap — the ports, users, and outputs will be wrong. If a step is evidenced only by a screenshot you cannot read as text, describe it in prose ("the screenshot shows …") and cite no console block. (Pilot: a foothold catcher on :8888 was back-filled with the analyst-stage nc -lvn 8889 block — wrong port, wrong stage.) A box's target IP may differ across cells — HTB reassigns it on respawn/reset (a solve spanning >1 box lifetime, or a reset of a stuck box). Keep each IP verbatim; never normalize a later IP to an earlier one, and never read the change as an inconsistency or a fabrication signal. (Pilot: paperwork — recon/foothold on …81, root SSH on …95 after a day-2 respawn; both real.)
7. Redaction is truncation, not substitution. When partially redacting a secret, the visible characters MUST be a verbatim substring of the real value — a real prefix (optionally plus the real last-N chars) with the elided middle as …. Never invent, guess, or "vibe" replacement characters, and use the … (U+2026) ellipsis so the ground-check can find it. (Pilot: opsmcp_secret_key_4f5a…b2c3 — the b2c3 was fabricated; the real key ends 0f1a.)
8. "Used" means evidenced by a notebook cell. A tool, link, or command counts as "used during the engagement" only if it appears in a notebook cell (command or output) or the operator named it in the interview. site/links.md, utils/, READMEs, and other room-template scaffolding are generic bookmarks shipped with every box — never assert them as used. (Pilot: pspy/linpeas/msfvenom from site/links.md were listed as "used" on a box whose chain touched none of them.)
9. Ground the interview or the operator confabulates. Every question quotes the real notebook evidence, states the fact and asks only the interpretation, stays non-leading (no single cause to nod at), and treats "I don't recall" as a valid answer → ⚠️ observed-only. A thin one-line prompt makes the operator invent answers without noticing. (See Step 2.)
10. Guardrails: never read ~/ctf/vpn/ (cleartext VPN creds). OSCP+ prep is private tuning context — never surface it in any published content.

Pipeline

Step 0 — Inputs

Confirm the notebook path (~/ctf/htb/<group>/<box>/engagement.ipynb) and the box name. Note the room dir alongside it (has site/links.md, artifacts/, payloads/).

Open the interview ledger for this box: <site-root>/.interviews/<box>.md (copy templates/interview.md). It is the single source of truth for the interview — gitignored, ephemeral, one file per box so several boxes can be interviewed at once (see Parallel crawl below). Fill its frontmatter (box, event, notebook, status: interviewing).

Step 1 — Reconstruct & harvest

python3 <skilldir>/scripts/nbdump.py <notebook> summary        # richness + Final-chain detection
python3 <skilldir>/scripts/nbdump.py <notebook> cells          # cells + truncated outputs
python3 <skilldir>/scripts/nbdump.py <notebook> urls           # embedded URLs (operator's sources)
python3 <skilldir>/scripts/nbdump.py <notebook> attachments <scratch>/img   # extract screenshots
cat <box>/site/links.md 2>/dev/null                            # generic room-template bookmarks — NOT proof of use
# Embedded exploit repos = real tools the operator cloned & used → citation sources:
find <box> -name .git -maxdepth 4 \( -type d -o -type f \) 2>/dev/null | \
  while read g; do d=$(dirname "$g"); echo "$d → $(git -C "$d" remote get-url origin 2>/dev/null)"; done

• If a ## Final chain (or Summary/TL;DR) cell exists, it is the operator's own clean replay — use it to separate the working path from exploration/dead-ends.
• Embedded notebook URLs (from nbdump.py … urls) are the operator's real sources — harvest verbatim, never regenerate. site/links.md is generic room scaffolding shipped with every box — it is NOT evidence any tool was used here. A tool/link is "used during the engagement" only if a notebook cell (command or output) shows it, or the operator names it in the interview (golden rule 8). Everything from site/, utils/, and READMEs is reference-bookmark material at most — label it as such, never assert it as used.
• Embedded git repos under payloads//artifacts/ are tools the operator actually cloned and ran — grep each for its origin URL and cite the public ones directly. This resolves tool provenance mechanically (public tool vs self-authored, credit/ attribution): it is NOT an interview question. The operator will not remember a source that isn't in the notebook, so never ask them where a tool came from — check the repo.
• Read extracted screenshots (Read tool) to know what each one shows before referencing it.
• Produce a draft attack-path reconstruction (working chain, numbered) and a list of dead-ends. Show it to the operator to confirm you separated them correctly.

Step 2 — Interview (the operator's lane)

The interview happens in the ledger file (<site-root>/.interviews/<box>.md), not in chat. Write the reconstructed chain, the structural rulings, and every Socratic question into that file; the operator answers inline under each **A:**, in any order, at their own pace. This decouples the interview from the chat stream so 5+ boxes can be worked in parallel without interleaving. Do not ask the questions conversationally and do not use AskUserQuestion for the interview — the file is the source of truth.

Write into the ledger, in this order:

• The reconstructed chain (working path, numbered) + dead-end candidates, so the operator can correct the working-path / dead-end split.
• The structural rulings (defaults in italics):
  • Dead-ends → keep as "what didn't work" with why / cut / one-line.
  • Big blobs & log-spam → elide with a marker / collapse in <details> / verbatim.
  • Credential material → partially redact (f29e9c01…be3b) / verbatim / fully redact.
  • Event placement → new seasonN-htb-YY event vs existing htb-machines (see Step 4).
  • Publish timing → publish now vs hold until a date. Room authors dislike writeups within 7 days of a box's release; the post date: is the solve date, not the release date, so this can't be computed — ask. Default published: true; if held, the operator gives the safe date → published: false + publish_after: YYYY-MM-DD.
• The Socratic questions, phase by phase, each [PENDING].

Then set the ledger status: interviewing, stop, and hand back — tell the orchestrator the ledger path and that it awaits answers. When resumed, re-read the ledger: a question with a non-empty **A:** is answered (flip it to [ANSWERED]); a blank one or "don't recall / didn't check" maps to ⚠️ observed-only; an A: of NEEDS CONTEXT means quote the exact notebook fragment in a follow-up sub-question and hand back again. Only proceed to Step 3 once no [PENDING] / NEEDS CONTEXT remains (or the operator says to proceed with what's there). If an answer contradicts the notebook, note the discrepancy in the ledger and resolve it before writing.

Grounding (critical — this prevents the operator from confabulating). A thin, one-line question forces the operator to reconstruct from nothing, and they will invent an answer without realizing it. Every question MUST:

• Quote the real evidence it's about — the exact command(s) and the decisive output line(s) from the notebook — so the operator reacts to artifacts, not a clue.
• State the fact, ask only the interpretation. The notebook already holds what was done; ask only the why / what it meant / what was learned. Never make the operator rebuild a fact that's on the page.
• Stay open and non-leading. Do NOT bake in a single plausible cause the operator can just agree with ("was it because LDAP was filtered?" invites a false yes). Ask "why this, here?" — and if you offer candidate explanations, offer several plus an explicit "…or something else, or you don't recall."
• Make "I don't recall / I didn't check" a first-class answer. It maps to ⚠️ observed-only (state what the output shows, omit the why) or omission — never a fabricated fill. Apply zero pressure to produce an answer.
• Cross-check the answer against the evidence. If the operator's answer conflicts with what the notebook shows, surface the discrepancy ("the output shows X, the answer implies Y — which is right?") before writing either version.

Ask only what the notebook doesn't already answer. Question bank (adapt per box):

• Tool/approach choice: why this tool here? what was the trigger? (e.g. "ADWS port open → try SOAPy"). Was a more common tool tried and dropped?
• The decisive observation: what in the output told you to pivot? (an error, a share comment, a banner, a writable ACL).
• Opportunistic vs planned: was this a reasoned deduction or a speculative bet? Write it the way it happened — do not dramatize a blind drop into cleverness.
• Dead-ends: why did each fail? assert the why only if verifiable (else observed-only).
• Privilege/loot decisions: why this escalation path over an alternative (e.g. memory dump vs DCSync)? what constraint forced it?
• One-line lesson: the sentence future-you should read first.

Never ask about sources beyond the notebook. "Any writeup/video/blog you leaned on?" or "where did this tool come from?" yields nothing — the operator only remembers what's in the notebook; anything else is already forgotten. Tool/repo provenance is resolved mechanically by grepping embedded git repos for their origin URL (Step 1), citing the public ones — not by asking. Ask only about reasoning that genuinely lived in the operator's head during the engagement.

The operator's answers become the prose of the 🧠 callouts. Do not embellish beyond what they said.

Step 3 — Verify & cite

For every external fact gathered in Steps 1–2:

• MITRE: fetch each candidate attack.mitre.org/techniques/<ID>/, confirm ID↔name, and tag only if the definition matches what happened. Prefer the most specific sub-technique (e.g. T1176.002 IDE Extensions, not the T1176 parent).
• CVEs / named techniques / error codes: WebSearch → WebFetch an authoritative source; cite the URL. (Pilot examples: BadSuccessor = CVE-2025-53779, Akamai; KDC_ERR_PADATA_TYPE_NOSUPP = KDC lacks Smart Card Logon EKU, Almond OffSec.)
• Links: operator's links pass through verbatim; each link you add is confirmed to resolve. Then run the whole-post check in Step 5. Build a small fact ledger (fact | internal/external | source) before writing, and drop or ⚠️-mark anything unsourced.

Step 4 — Assemble

Copy templates/post.md as the skeleton. Rendering rules:

• Event placement: a season box → new event dir ctf/events/seasonN-htb-YY/ with a toc.md (layout: default, parent: Challenges, has_children: true), matching the existing season8-htb-25 pattern; a standalone machine → ctf/events/htb-machines/. Post filename YYYY-MM-DD-<slug>.md. Front matter: grand_parent: Challenges, event: "htb-season-N" (or htb-machines).
• Images: copy extracted screenshots to assets/images/ctf/events/<event>/<box>/<descriptive-name>.png; reference with an absolute /assets/... path and descriptive alt text.
• Blobs elided, secrets partially redacted, dead-ends kept, impersonal voice, no cell annotations, no OSCP framing — per the golden rules.
• Further reading: "Used during the engagement" holds ONLY tools/links evidenced by a notebook cell or named by the operator in the interview (golden rule 8). Generic site/links.md bookmarks go under a clearly-labeled "standard toolkit bookmarks (shipped with the room template — not necessarily used here)" block, or are omitted — never asserted as used. "Reference material (added for study)" stays its own block. The Tools-used table follows the same rule: every row maps to a notebook cell.
• Keep the provenance footer.

Step 5 — Build & validate (local)

cd <site-root>
bundle exec jekyll build 2>&1 | grep -iE 'error|liquid|done in'    # must build clean
python3 -c "..."  # or curl: confirm the post + toc + images serve 200 if a server is up
bash <skilldir>/scripts/linkcheck.sh <post.md>                     # every link resolves
python3 <skilldir>/scripts/groundcheck.py <post.md> <notebook>    # every token traces to the notebook
# Leak sweep — none of these may appear in the built HTML:
grep -RniE '<full-nt-hash>|<cert-password>|<dpapi-masterkey>|doIF[A-Za-z0-9+/]{80}' _site/<post>.html || echo OK

Fix any 404 link (find the real URL or unlink). Confirm 403s are anti-bot via WebFetch. groundcheck.py is a read-only gate — it edits nothing, it fails the build and lists any redaction fragment, "used" tool, or flag that isn't in the notebook. A failure means a fabrication slipped through golden rules 6–8; fix the post, don't silence the check.

Step 6 — Hand back & publish

Present the rendered URLs for the operator to curate ("just the right amount of annoying"). Publish only on explicit confirmation — defer to the repo's publish skill (Playwright validation + conventional commit + push). Follow the global git rules: conventional commits, no external repo URLs/PR refs in the commit message.

On a successful publish, delete the interview ledger (<site-root>/.interviews/<box>.md) — it is scaffolding, and the published post is the durable record. (Before that, keep it: bump its status as you go — answered once the operator has replied, drafted after Step 4, published at the moment you remove it.)

Parallel crawl (5+ boxes at once)

The ledger is what makes this scale. To work a batch simultaneously, the orchestrator spawns one scribe per box; each runs Steps 0–2 (reconstruct → write its own .interviews/<box>.md → stop), then hands back. The orchestrator posts one consolidated pointer listing every ledger path awaiting answers. The operator opens them in an editor, batch-answers across all boxes in a single pass, and says which are done. The orchestrator resumes each scribe, which reads its ledger and continues to Steps 3–6 independently. One ledger per box means no cross-talk; each box publishes (and purges its ledger) on its own timeline.

Notes

• This runs well on Sonnet: the operator supplies the reasoning; the pipeline is mechanical + verification-heavy, not open-ended reasoning. The one step that may benefit from a stronger model is Step 4 prose assembly on long, multi-phase boxes — escalate the model for that step only if the flow reads flat.
• Notebook completeness varies wildly (some boxes are near-empty templates). If summary shows almost no code_with_output and an empty Engagement Notes, tell the operator there's not enough to write and skip.