Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add UnboundCompute/security-agent-skills --skill hunting-mutual-tls-and-service-identity-gapsgit clone --depth 1 https://github.com/UnboundCompute/security-agent-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/unboundcompute/security-agent-skills/hunting-mutual-tls-and-service-identity-gaps)<a href="https://agentmods.dev/skills/unboundcompute/security-agent-skills/hunting-mutual-tls-and-service-identity-gaps"><img src="https://agentmods.dev/badge/skills/unboundcompute/security-agent-skills/hunting-mutual-tls-and-service-identity-gaps/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/unboundcompute/security-agent-skills/hunting-mutual-tls-and-service-identity-gaps"><img src="https://agentmods.dev/badge/skills/unboundcompute/security-agent-skills/hunting-mutual-tls-and-service-identity-gaps.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00191 | $0.02076 |
| Opus 5.5 | $0.00076 | $0.00830 |
| Sonnet 5.5 | $0.00038 | $0.00415 |
| Haiku 4.5 | $0.00019 | $0.00208 |
Grade A, and why
hunting-mutual-tls-and-service-identity-gaps scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 141 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Hunting mutual TLS and service identity gaps: proving which service is on the other end
Service-to-service authentication with mutual TLS rests on a chain of checks, and skipping any one of them leaves the caller's identity unproven while the connection still looks encrypted and authenticated. The endpoint has to actually require a client certificate, not merely request one and proceed without it. It has to verify the certificate is valid and chains to a trusted authority. Crucially, it then has to check which identity the certificate names and that this identity is authorized for the call, verifying the chain proves the certificate is legitimate, not that it belongs to the right service. And the trust anchor matters: if the service accepts any certificate issued by a broad authority, then any peer that authority ever issued a certificate to can authenticate as any service. When identity is instead taken from a header or source IP, it is spoofable and the certificate is decorative. The hunt is for the missing link in that chain. You hunt this by presenting the wrong certificate, no certificate, and a valid-but-wrong-identity certificate and seeing what authenticates.
When to use
- Services authenticate each other with mutual TLS or client certificates to prove which service is calling.
- An endpoint may request a client certificate without requiring it, or verify the chain but not the identity.
- Service identity may be derived from a header or source IP rather than the verified certificate.
Scope check
Test service identity only on systems you own or are authorized to assess, on non-production endpoints. Presenting certificates and connecting attempts real authentication between services, so use non-production identities and never authenticate into a real service path. If you can't name the authorization, stop.
The loop
- Establish the intended peer identity first. Name, for each endpoint, exactly which service identities may call it and how that identity is proven: a client certificate naming the specific service, chaining to a narrowly scoped trust anchor. This is the false-positive killer: an endpoint that requires a client certificate, verifies its chain to a scoped anchor, checks the named identity against an allowlist, and authorizes on that verified identity is correct. Name the intended identity, then test each check.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 141 lines · 191 tokens per session scan A 9ecc0bd1b54c
hunting-mutual-tls-and-service-identity-gaps is a skill published in the GitHub repository UnboundCompute/security-agent-skills (5 stars, last pushed 1mo ago), licensed MIT. It adds 191 tokens to every session and 2,076 once invoked, about $0.0008 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-05.
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