email-domain-security
Rigorous, defensible email-spoofability verdict and SPF supply-chain risk analysis computed from published DNS alone. Deepens the record-level SPF/DMARC/DKIM/BIMI/MTA-STS/DNSSEC fetch recipes in the offensive-osint arsenal (§16.14) with the reasoning that section doesn't do: a priority-ordered composite verdict for whether an attacker can actually land header-From-spoofed mail in an inbox, and by which vector (exact-domain vs subdomain) — grounded in the single most-misunderstood distinction in email security: the envelope MAIL FROM that SPF authenticates vs the visible header From: that only DMARC governs. Explains precisely why SPF -all/~all alone is NOT spoof-proof without DMARC enforcement, and why SPF +all bypasses DMARC even under p=reject pct=100. Covers RFC 7208 §4.6.4's 10-DNS-lookup / 2-void-lookup PermError fail-open condition with a runnable stdlib-only lookup-counter script, plus the SPF-include-takeover supply-chain vector (an attacker re-registering a dead include inherits SPF-pass authority over the victim domain) with strict transient-vs-NXDOMAIN discrimination discipline so a temporary SERVFAIL is never mistaken for a takeover lead. Fully passive: DNS TXT reads only, no mail sent, no RCPT TO probe, no API keys. Use when auditing a domain's real spoofing resistance (not just its published records), explaining to a client why 'we have SPF -all' does not mean they're covered, investigating an SPF PermError or an unusually long include chain, evaluating a dead SPF include as a takeover lead, or writing a defensible spoofability finding for a deliverable.
git clone --depth 1 https://github.com/elementalsouls/Claude-OSINT /tmp/email-domain-security && cp -r /tmp/email-domain-security/skills/email-domain-security ~/.claude/skills/email-domain-securitySKILL.md
# Email Domain Security — Spoofability Verdict & SPF Supply-Chain Analysis
> Companion skills: **`offensive-osint` §16.14** (raw record-fetch recipes — dig/PowerShell one-liners for SPF/DMARC/DKIM/BIMI/MTA-STS/TLS-RPT/DNSSEC/CAA, the MX→IdP inference table, the DMARC reporting-vendor table). **`osint-methodology`** (confidence levels, output format, severity rubric this skill inherits). Fetch the records with §16.14 first; bring the raw TXT text here for the verdict. This skill does not re-list what a record *is* — it reasons about what a domain's *combination* of records actually lets an attacker do.
## 0. When to Use / When NOT
**Use this skill when:**
- Asked to audit spoof feasibility, produce an email-spoofability verdict, or explain "is domain X spoofable."
- You already have raw SPF/DMARC TXT text (via `offensive-osint` §16.14 or your own `dig`) and need the *verdict*, not just the record dump.
- Investigating an SPF PermError, a long or unusual include chain, or a dead `include:` target.
- Writing a client-facing finding that has to survive the pushback "we have SPF `-all`, why is this flagged?"
- Reasoning about DMARC subdomain policy inheritance, `pct=` partial enforcement, or duplicate-record handling.
**Do NOT use this skill when:**
- You haven't fetched the raw records yet. Run `offensive-osint` §16.14's dig/PowerShell recipes first, then bring the text here.
- You want to actually *send* a spoofed test message or run an SMTP `RCPT TO` liveness check. That is active engagement work requiring explicit authorization and is out of scope for this passive-DNS skill — see §14.
- You're auditing TLS/cert posture rather than email auth — that's `offensive-osint` §16.15 / TLS deep audit territory.
- You need AXFR / zone-transfer analysis. `dns_deep`-class modules run that check alongside the email-auth sweep, but it's a distinct DNS finding (open zone transfer, unrelated to spoofability) — see the note in §9.
---
## 1. Scope & Authorization Posture
Same posture as the companion skills: assets you own or have written authorization to assess. Everything in this skill is **passive** — reading published, public DNS TXT records that any resolver on the internet can already see — so it carries essentially zero detectability risk on its own.
But the *verdict* this skill produces is the input to a decision someone downstream might act on (an authorized phishing-simulation send, a client remediation ticket, a bug bounty report). Flag the boundary explicitly: a passive verdict of "spoofable" is a strong, defensible claim about DNS-published policy — it is not itself proof that a spoofed message was delivered. See §14.
---
## 2. Confidence Levels
Inherits `osint-methodology` §2's three-tier scale, mapped onto email-auth assertions specifically:
| Level | Meaning here |
|---|---|
| **TENTATIVE** | A mechanism in the SPF chain could not be resolved (timeout / SERVFAIL / no nameservers) — the verdict for *that mechanism* is inconclusive. See §8's transient-vs-dead discipline; never silently upgrade this to FIRM. |
| **FIRM** | Record(s) present, parsed under RFC 7208 (SPF) / RFC 7489 (DMARC) grammar, verdict computed purely from directly observed TXT text. This is the ceiling for everything this skill produces on its own. |
| **CONFIRMED** | The verdict was cross-checked against actual mail-flow behavior (an authorized send-and-verify test). Outside this skill's passive scope — only ever assigned after an active test someone else ran. |
**Default posture:** everything this skill outputs is at most FIRM. Never claim CONFIRMED spoofability from DNS reading alone, no matter how conclusive the record combination looks.
---
## 3. Output Format
Same finding schema as the companion skills, with the fields this domain actually populates in practice:
```
Finding:
module: email_spoof # or dns_deep / email-domain-security, depending on your pipeline
asset_key: domain:<target>
category: DNS_MISCONFIG # the real implementation groups ALL email-auth findings under
# this one category — these are DNS record misconfigurations,
# not mail-server misconfigurations. Don't invent a separate
# EMAIL_SECURITY category unless your own schema needs one.
severity: <high|medium|low|info> # see §7 / §8 for exact per-condition mapping
confidence: <tentative|firm|confirmed> # see §2 — almost always FIRM
title: "Email spoofable — <vector>" # or the specific SPF supply-chain title
description: <cite the exact reasons — see the "reasons" convention below>
evidence:
spf: <raw SPF TXT, or "(none)">
dmarc: <raw DMARC TXT, or "(none)">
vector: <e.g. "header-From spoof (exact domain, SPF +all bypasses DMARC)">
effective_subdomain_policy: <sp= value or the inherited p= value>
reasons: [<ordered list of full-sentence reasons — see below>]
dedup_key: "emailspoof:<target>" # or "spfsupply:<target>:<kind>", "spfmulti:<target>",
# "dmarcmulti:<target>" — stable across re-scans so the
# same finding doesn't duplicate on the next audit
remediation: <the specific DMARC/SPF ratchet needed to close the exact vector found>
```
**The `reasons` convention:** the verdict logic (§7) doesn't just return a label — it builds an ordered list of full, client-report-ready sentences explaining *why* the domain is spoofable by that vector. Quote them directly in a deliverable rather than re-writing the explanation from scratch; they're already written in the right register (e.g. *"SPF terminates in `+all` (or bare `all`), returning an SPF pass for any sender IP. An attacker aligns the envelope sender to the target domain, so DMARC passes on the SPF leg and the spoofed message is delivered even if DMAOperational arsenal for external red-team and bug-bounty reconnaissance. Concrete wordlists (28 Swagger paths, 13 GraphQL paths, 35 high-risk ports, 6 missing-header findings, 15 always-on HTTP checks, 5 SAML paths, cloud bucket permutations, JS guess-paths, vendor product fingerprints for Citrix/F5/Pulse/Fortinet/Cisco/PaloAlto/VMware/Exchange, cloud-native service fingerprints, container/K8s exposure paths, CI/CD platform paths, documentation/wiki leak paths, WHOIS/RDAP, DNS record catalog, Wayback CDX recipes), 80-pattern secret-regex catalog (incl. modern AI API keys: Anthropic/OpenAI/HuggingFace/Cloudflare/DigitalOcean/npm/PyPI/Docker Hub/Atlassian/DataDog/Sentry/ngrok; plus a provider-expansion tier: Postman PMAK/GitLab/Square/Shopify/Mailchimp/PagerDuty/Asana/Databricks/Grafana/Terraform Cloud/Fastly/Algolia/Segment/Airtable/GCP+Google OAuth/Azure AD/Facebook OAuth/RubyGems/JFrog/Okta/Slack app-level/Dropbox/Doppler/HashiCorp Vault/Firebase Cloud Messaging), 80+ dork corpus across 9 categories, GitHub code-search dorks, copy-paste curl/httpie probes for every check, post-discovery enumeration workflows (AWS/GitHub/Slack/JWT/PMAK/Anthropic/OpenAI), endpoint interest scoring rubric (0–100), mobile app ownership confidence + APK static-analysis pipeline (acquisition, apktool/aapt2/jadx/androguard decompile, manifest exported-component/deep-link/misconfig extraction, Firebase config, network-security-config, embedded-secret scan), identity-fabric endpoints (Entra/Okta/ADFS/Google/SAML/M365 Teams+SharePoint+OneDrive+OAuth + user-enum), GraphQL field-suggestion enumeration when introspection disabled, 9 read-only secret validators (Postman/AWS/GitHub/Slack/Anthropic/OpenAI/npm/Atlassian/DataDog), Postman workspace search (verified endpoint), Stack Exchange sweep, public SaaS dorks, email security analysis (SPF/DMARC/DKIM/BIMI/MTA-STS/DNSSEC), origin-discovery / CDN bypass techniques, TLS deep audit (sslyze/testssl.sh/JA3/JA4), reverse-DNS sweep + IPv6 enum, vulnerability prioritization data sources (NVD/EPSS/CISA KEV/ExploitDB/Metasploit), 27 attack-path hint templates, 80+ severity-matrix examples, LinkedIn employee enumeration, job posting tech-stack analysis, Slack/Discord workspace discovery, package registry leak hunting (npm/PyPI/Docker Hub/Quay/GHCR), sat imagery for physical recon, tooling quick-install one-liners, sector-specific recon notes (healthcare/finance/ICS-SCADA/IoT/government), runnable stdlib-only secret_scan.py helper, plus the existing tool references for username/email/phone/people/social/breach/infrastructure/crypto/media/geospatial/AI/archiving/automation. Use when you need concrete probe paths, regexes, payloads, scoring rules, curl one-liners, and tool URLs for an authorized external recon engagement.
Comprehensive OSINT methodology for external red-team operations and authorized attack-surface assessments. Covers the 6-stage recon pipeline (seed → asset expansion → enrichment → exposure analysis → convergence → operator-armed active validation) with connector-resilience and stage-vs-gating discipline, asset-graph discipline, severity rubric, confidence upgrade workflows, time budgeting, identity-fabric mapping, breach×identity correlation with per-person identity dossiers, detectability tagging, detection-aware probing, WAF/CDN bypass, vulnerability prioritization, phishing infrastructure planning, bug bounty submission, and client deliverable templates. Use when planning or executing reconnaissance against authorized targets, mapping an organization's external attack surface, investigating a person/entity, or producing client deliverables.
Build, validate, and run the claude-osint skills repo — check SKILL.md frontmatter, run the secret_scan.py and h1_reference.py helpers, run sync-skill-content.sh, run the smoke test. Use when asked to run, build, test, validate, or smoke-test claude-osint or its OSINT skills/scripts.
Organization-grade cloud and supply-chain attack-surface discovery: S3/GCS/Azure Blob bucket discovery via observed-name mining (CNAME/cert-SAN/Wayback) and bounded two-class permutation (6 prefixes x 15 suffixes on trusted tokens, bounded target-bound expansion on subdomain stems), existence (HEAD/GET) vs public-listing confirmation, object-key triage into 9 value tiers (database dumps, credentials, IaC state, kubeconfig, VCS dirs, config, archives, PII, logs), dangling-CNAME bucket-takeover detection, and the ownership-gated severity model that stops an unattributable public bucket from becoming a false CRITICAL; the fully offline AWS-account-ID recovery from a leaked AKIA/ASIA/AROA access key (base32 decode, runnable stdlib Python, canonical test vector, AWS-documentation-example-ID screening); dependency-confusion confirmation for npm/PyPI (internal-signal classifier -- private-registry binding vs org-namespace match -- paired with a read-only public-registry 404 check and the npm scope-claimability nuance the public search API misses); and passive cloud-native/container/Kubernetes/CI control-plane fingerprinting (Lambda URLs, API Gateway, Cloud Run, App Service, kubelet/etcd/K8s API/dashboard, Jenkins/GitLab/Argo CD) as an org-attribution and exposure surface. Passive/discovery only -- no exploitation, no credential submission, no active control-plane confirmation (a stage-6 validate_cloud active tier is described but out of scope). Use when enumerating a target's cloud storage footprint, recovering an AWS account ID from a leaked key, confirming a supply-chain dependency-confusion vector, or fingerprinting cloud-native/K8s/CI infrastructure for an authorized external recon engagement.
Turns one-shot external recon into a continuous monitoring program. Covers the scheduled re-scan-and-diff loop (baseline snapshot -> interval sleep -> re-scan -> asset/finding delta -> threshold-gated webhook alert), the scan-to-scan diff engine (new/removed/changed assets by a tracked-attribute table, new/resolved findings by a stable cross-scan fingerprint), adversary CTI / chatter monitoring across six public feeds (ransomwatch, ransomware.live, HackerNews Algolia search, Reddit security-subreddit RSS, GitHub Gist code-search, public Telegram channel scraping) with a source-kind-aware severity engine (leak-site/forum/telegram/paste tiers, CRITICAL through INFO), literal/glob/regex watchlist pattern matching, full-corpus capture with retroactive rescan on new watchlist entries, infrastructure-tracking-over-time discipline (certificate-transparency, passive-DNS, port/service, and typosquat re-enumeration cadence, and what a genuine 'perimeter drift' event looks like in the diff output), a five-state finding-lifecycle state machine (open/triaged/risk_accepted/resolved/false_positive) with per-severity SLA and fingerprint-based cross-scan dedup and auto-resolve/reopen rules, the alert-fatigue trap where a lifecycle-unaware rule re-fires on an already-accepted finding, a durable retry/backoff alert-outbox pattern ('queued is not delivered'), and copy-paste bash-cron plus PowerShell-Scheduled-Task recipes for a re-scan+diff loop with the Slack-compatible webhook payload shape. Passive OSINT and analysis only -- no new active-intrusion technique. Use when setting up ongoing monitoring for a retainer or MSSP engagement, tuning alert thresholds to avoid fatigue, triaging a finding's lifecycle status, investigating adversary chatter about a brand, building a 'what changed on the perimeter since last week' report, or deciding whether a persisting finding should re-alert.
FAIR-aligned exposure quantification: turns a pile of recon findings into a defensible 0-100 + A-F org risk score (Likelihood x Impact, three ownership-aware factors: exposure/threat/impact), an ownership + proof demotion cap so unproven or weakly-owned findings can't inflate the number, a $-denominated FAIR loss-magnitude estimate (IBM/Ponemon per-record cost bands, cross-source record dedup, threat-factor annualization), attack-path amplification (curated red-team chain catalog + generic graph-walk engine, with a kill-chain vs shared-fate honesty gate), and a board-ready one-pager deliverable (hero $ + letter grade + top-3 findings + top attack path + the ask). Extends osint-methodology's severity rubric and client deliverable templates with quantification. Passive analysis only -- operates on findings already collected, no target traffic, no API keys. Use when asked to score risk, quantify exposure, estimate breach cost, build a board report, translate technical findings to dollars, or explain why a grade or dollar figure came out the way it did.
Organization-grade identity-fabric mapping: tenant/federation fingerprinting and the pre-auth user-ENUMERATION oracle methodology — enumeration and fingerprint only, never credential submission. Covers domain-to-tenant resolution (Microsoft getuserrealm.srf Managed/Federated namespace check, Entra OIDC metadata tenant-GUID extraction, Autodiscover v2), keyless Microsoft tenant-federation mapping (GetFederationInformation SOAP -> sibling-domain discovery, discover-only ROE, FEDERATED_WITH provenance edge held out of attack-path pivoting), Okta org-slug derivation + OIDC fingerprint + governed custom-domain enumeration, ADFS passive/active fingerprint + version inference, Google Workspace MX-correlated detection, generic OIDC (Auth0/Keycloak/Ping Identity/OneLogin/Duo) discovery, SAML metadata (5 paths), Azure AD Seamless-SSO Negotiate-challenge detection, Microsoft Defender for Identity (MDI) sensor-API presence check, the user-enumeration oracle methodology for Microsoft GetCredentialType (IfExistsResult semantics: exists / doesn't-exist / exists-in-federated-tenant / throttled) and Okta /api/v1/authn (errorCode differential), Medium-detectability discipline with a hard 20-candidate-per-tenant cap and admin/role interest-based ranking, and name x confirmed-email-pattern login-candidate synthesis that FAILS CLOSED with zero output when no org pattern is confirmed. Grounded directly in a production ASM implementation's sso_idp.py, tenant_recon.py, and core/email_patterns.py modules. Deepens — does not duplicate — offensive-osint skill's Identity Fabric endpoint reference with the tenant-federation MAP, the oracle WORKFLOW, and the candidate-SYNTHESIS methodology that reference lacks. Use when fingerprinting an organization's identity provider, mapping its tenant/federation boundary, running an authorized pre-auth user-enumeration pass, or synthesizing login candidates from harvested names to feed that oracle — never for password spray, credential submission, or auth bypass.
Org-grade attack-surface mapping: given a company's legal identity, discover its ENTIRE owned internet footprint — corporate family -> owned domains -> owned netblocks/ASN -> live assets — with attribution discipline, not just DNS breadth. The org-first attribution pyramid (legal entity -> LEI/registration -> corporate family -> owned domains -> owned netblocks/ASN -> live assets). Corporate-identity resolution via the GLEIF LEI API (legal name -> LEI, exact-LEI direct-children expansion, downward-only depth-capped BFS, NEVER a name re-resolution), SEC-EDGAR full-text search + Exhibit-21 subsidiary entity names, OpenCorporates entity corroboration, Wikidata SPARQL corporate graph (P856/P355/P749/P1830). Domain attribution via reverse-WHOIS (WhoisXML preview-then-purchase quota guard, SecurityTrails associated-domains — both paid), crt.sh O= certificate-transparency organization pivot (keyless), infrastructure correlation (shared NS/MX/SaaS-TXT, netblock membership, reverse-DNS PTR), and the independent-evidence combiner (1-prod(1-w_i), rule of three, OwnerTier NONE/WEAK/MODERATE/STRONG/CONFIRMED) — discover-only `related:` candidates are NEVER auto-scanned. Netblock/ASN attribution via org-first RIR queries (ARIN Whois-RWS org-handle search, RIPE DB organisation + inverse-org search) that recover 'dark netblocks' with no DNS link to the seed, ASN discovery (RIPEstat + BGPView union), the HYPERSCALER-SCOPE GUARD (never attribute a whole AWS/GCP/Azure/Cloudflare announced range to a tenant — keep only the seed-containing block, tag shared_hosting_cdn), and org-identity-seeded internet-scan-index queries (Shodan/Censys/ZoomEye/FOFA/BinaryEdge org: filters + an always-on keyless crt.sh fallback). Promote-to-scan triage ranks forgotten discover-only netblocks by remote-access exposure (gateway-vendor/KEV/control-plane/datastore port scoring) into an operator queue. Attribution confidence rubric + anti-patterns (namesake grafting via GLEIF name re-resolution, single-signal ownership, hyperscaler over-attribution, privacy-WHOIS pivot poisoning, RIR org-name collisions). Passive/keyless-first OSINT only — every paid-key dependency is enrichment on top of a keyless core, never a hard requirement. Use when mapping an organization's full corporate-family internet footprint, resolving a legal entity to its LEI/subsidiaries, discovering domains/netblocks/ASNs an org owns beyond its one seed domain, auditing M&A/shadow-IT sprawl, or scoping an engagement that starts from a company NAME rather than a domain.