Testssl Inspector Expert

testssl Inspector Expert

Use this skill when reviewing findings produced by /testssl-inspector:scan. The connector wraps testssl.sh and emits v1 Findings against tls_endpoint resources; this skill translates those into remediation advice an engineer can act on and audit evidence a reviewer can sign off.

Reading the output

Findings live at ~/.cache/claude-grc/findings/testssl-inspector/<run_id>.json. Each document covers one TLS endpoint:

• resource.type = "tls_endpoint", resource.id = "<host>:<port>", resource.uri = "https://<host>:<port>/" for HTTPS or resource.uri = "starttls+<proto>://<host>:<port>/" for STARTTLS scans
• evaluations[] — one entry per (control_framework, control_id, testssl finding) tuple
• findings[] — narrative roll-up for CVEs and critical results (cap 50 per doc)
• metadata.target, metadata.effective_target, metadata.host, metadata.port, metadata.starttls — the original input, the port-expanded target actually scanned, the parsed host/port, and the STARTTLS protocol when applicable

What testssl IDs mean

Most fails fall into one of five families. The remediation pattern is the same within each family.

Family 1 — Weak protocol offered

IDs: SSLv2, SSLv3, TLS1, TLS1_1. SCF anchors: CRY-01 (Use of Cryptographic Controls), CRY-03 (Transmission of Sensitive Data), NET-09 (Session Authenticity). SCF crosswalk fans these out at scan time — typical resolved targets include NIST SC-08, SC-08(01), SC-08(02), SC-13, SC-23, SI-07(06); SOC 2 CC6.1, CC6.7; PCI 4.2, 4.2.1, 4.2.1.2, 8.3.2; ISO 27002 5.14, 8.24, 8.26.

Remediation:

• Terminate TLS at a load balancer or web server that supports a TLS 1.2+ minimum. AWS ALB: set the security policy to ELBSecurityPolicy-TLS-1-2-2017-01 or newer. NGINX: ssl_protocols TLSv1.2 TLSv1.3;. Apache: SSLProtocol -all +TLSv1.2 +TLSv1.3.
• PCI DSS 4.0.1 specifically prohibits SSL and "early TLS" (1.0/1.1) — these are audit-fail conditions, not advisories.

Family 2 — Weak ciphers in the offered list

IDs: cipher_negotiated, cipherlist_* (NULL, aNULL, EXPORT, LOW, 3DES_IDEA, OBSOLETED), RC4, std_* variants. SCF anchors: CRY-01.2 (Algorithm Selection), CRY-05 (Cryptographic Protection). Resolved targets typically include NIST SC-13, SC-28, SC-28(01); SOC 2 CC6.1, CC6.7; PCI 3.5, 3.5.1.2, 3.5.1.3, 8.3.2; ISO 27002 8.24.

Remediation:

• Pin an explicit cipher list. Modern baseline: TLS_AES_128_GCM_SHA256:TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384.
• Prefer forward-secrecy ciphers (ECDHE/DHE families). Anything without (EC)DHE should be disabled in 2026.

Family 3 — Certificate posture

IDs: cert_expirationStatus, cert_notAfter, cert_signatureAlgorithm, cert_keySize, cert_chain_of_trust, OCSP_*, CT, DNS_CAArecord. SCF anchor: CRY-08 (Public Key Infrastructure). Resolved targets include NIST SC-12 (Key Establishment & Management) and SC-17 (PKI Certificates); SOC 2 CC6.1.

Remediation depends on the specific failure:

• Expired / near-expiry: rotate via ACM (AWS), Let's Encrypt, or your CA portal. Set up rotation alerts at T-30, T-14, T-7 days.
• Weak signature (SHA-1, MD5): reissue with SHA-256+ signature.
• Weak key size (RSA <2048): reissue with RSA 2048+ or ECDSA P-256+.
• Broken chain: server is missing an intermediate. Re-deploy the cert bundle with the full chain (your CA's portal shows the bundle order).
• No CAA record: add a CAA DNS record naming your authorized issuer(s) — defense against unauthorized certificate issuance.

Family 4 — Known TLS CVEs

IDs: heartbleed, CCS, ticketbleed, ROBOT, secure_renego, secure_client_renego, CRIME_TLS, BREACH, POODLE_SSL, fallback_SCSV, SWEET32, FREAK, DROWN, LOGJAM, BEAST, LUCKY13, RC4, winshock. SCF anchors: VPM-01 (Vulnerability & Patch Management), VPM-06 (Vulnerability Scanning). Resolved targets include NIST SI-02, SI-03, RA-05; SOC 2 CC7.1 and CC3.x POFs; PCI 6.3, 6.3.1, 6.3.3, 11.3, 11.3.1; ISO 27002 8.8.

These are not configuration tuning — they're vulnerability remediation. Treat any non-OK finding here as an audit-tracked vuln with a remediation deadline. Most are addressed by:

• Patching OpenSSL / the TLS implementation on the server.
• Disabling vulnerable protocols/ciphers (e.g., POODLE → drop SSLv3; SWEET32 → drop 3DES/Blowfish; BEAST → use TLS 1.2+).
• For BREACH (HTTP-layer): disable HTTP compression for responses containing sensitive data, or add a per-request masking token.

Family 5 — HTTP transport headers

IDs: HSTS, HSTS_preload, HSTS_time, HPKP, cookie_secure, cookie_httponly, banner_*, security_headers. SCF anchors: CRY-03 (Transmission of Sensitive Data), WEB-03 (Web App Hardening), NET-09 (Session Authenticity). Resolved targets include NIST SC-08, SC-08(01), SC-07(17), SC-23; PCI 4.2, 6.4, 6.4.1.

Remediation:

• HSTS missing or short max-age: Strict-Transport-Security: max-age=31536000; includeSubDomains; preload and submit to the HSTS preload list (hstspreload.org) for the strongest posture.
• Cookies without Secure or HttpOnly: fix the application — set both flags on every session cookie.
• HPKP: deprecated; if testssl flags HPKP usage, plan to remove it (browsers no longer enforce).

Evidence packaging

For an audit, the auditor wants three things per finding:

1. The raw testssl JSON or its normalized v1 doc (already in ~/.cache/claude-grc/findings/testssl-inspector/<run_id>.json).
2. The scan timestamp (collected_at field).
3. A remediation narrative tying each failed evaluation to a specific control and a future check.

Workflow:

/testssl-inspector:scan --target=auth.example.com --target=api.example.com
# Inspect the resulting findings file. Attach it to the audit evidence packet
# alongside the remediation tickets opened for each fail.

/grc-engineer:gap-assessment SOC2,PCI-DSS --sources=testssl-inspector
# Aggregates testssl evaluations with your other connector outputs into a
# control-by-control posture view.

What you will not do

• Don't run testssl against endpoints you don't own or are not authorized to test. testssl makes hundreds of connections per target and looks like a scanner to defenders.
• Don't recommend ignoring a fail because "the application is internal." TLS 1.0/1.1 and weak ciphers are no less broken on intranets.
• Don't recommend disabling individual checks just because they're noisy. If a check produces too many false positives, raise an issue against this connector with the testssl id and reasoning so we can refine the mapping table.
• Don't claim a finding maps to a framework beyond the five listed in scan.md. If a user asks about SP 800-52 Rev. 2 specifically, point them at the relevant framework plugin instead.