E16 · Draft vector
3 minRun the vector block.
Done when: vetor E.2.1: confere and saída: 0.
Lesson 6 · 18 min
Identifying who arrives: Web Bot Auth and signed agents (IETF draft)
Anyone can write a User-Agent. Web Bot Auth is the IETF proposal for a bot to sign each request with a key published at its own URL. It is still a draft (-00, September 2026). In this lesson you check a signature against the draft's test vector and see on a local server what it proves and what it doesn't.
Start the lesson
In this lesson you will
- 1HTTP Message Signatures (RFC 9421) and what the draft adds
- 2The draft's test vector, redone byte by byte
- 3Covered components, expiry and replay
- 4Identity is not authorization: the policy is still yours
Goal: check a Web Bot Auth signature against the draft's test vector and verify signed requests on a local server, knowing what the signature does not prove.
01From the agent that signs to the site's policy
draft-ietf-webbotauth-httpsig-protocol-00 (September 1, 2026). Click each step.
Click each block in the diagram to see what it does.
IETF group draft (Cloudflare and Google), expires March 5, 2027. Not an RFC.
02The draft's vector, redone
Appendix E.2.1: Ed25519 with the RFC 9421 public test key (B.1.4). Only node:crypto, no packages.
Terminal · vector
cd ~/projetos/formacao-webmcp-seguranca-v72/kit node scripts/wba.mjs vetor; echo "saída: $?"
Example from the repository
== node v24.13.0 · draft-ietf-webbotauth-httpsig-protocol-00 (01/09/2026) keyid calculado: poqkLGiymh_W0uP6PZFw-dvez3QJT5SolqXBCW38r0U · confere assinatura: RdNFx5Bj6au3YgAMQL/RzmUl… · confere vetor E.2.1: confere saída: 0
Ed25519 is deterministic: same key and same base give the same signature. If your implementation reproduces the vector, it builds the signature base the way the draft does. The test key never goes to production (appendix C.12 of the draft).
03Agent signs, origin checks: seven cases
A new key on every run. The origin already has the agent's directory, as the draft allows (§4.4); nothing leaves your machine.
Terminal · demo
cd ~/projetos/formacao-webmcp-seguranca-v72/kit node scripts/wba.mjs demo; echo "saída: $?"
Example from the repository
== node v24.13.0 · draft-ietf-webbotauth-httpsig-protocol-00 (01/09/2026) · origem http://127.0.0.1:36913 1 · sem assinatura → anônimo: sem assinatura (a política do site decide) 2 · assinado, válido → identificado: https://agente.exemplo (chave gw6T0rIc…) 3 · mesma assinatura em outro caminho → recusado: assinatura não confere 4 · assinatura vencida → recusado: assinatura vencida 5 · chave que a origem não conhece → recusado: chave desconhecida para https://agente.exemplo 6 · replay dentro da validade → identificado: https://agente.exemplo (chave gw6T0rIc…) 7 · assinatura mínima (só @authority) usada em /admin → identificado: https://agente.exemplo (chave gw6T0rIc…) 7/7 casos como esperado · replay dentro da validade: aceito saída: 0
Cases 6 and 7 are the draft's warning (§5.2): within the validity window, anyone who saw the request can repeat it; and a signature that covers only @authority is valid for any path on the site. That is why: short validity, with @method + @path covered, and the origin can require those components.
04Where this already shows up
1. Cloudflare
Since July 1, 2026, agents signed with Web Bot Auth count as Verified, with a new field: Direct (a single operator) or Intermediary (a service that many users drive).
2. Intermediary
With Intermediary, you can trust the operator and not each user who drives the agent. Cloudflare calls this transitive trust.
3. Your site
Anonymous still exists: signing is the bot's choice. Write your policy for the three cases: anonymous, signed and known, signed and unknown.
4. Together with robots
robots.txt says for what purpose each bot may come; the signature says who it is. robots in depth is covered in the inemaSEO Track.
05Practice
Check and decide.
E17 · Seven cases
10 minRun the demo block and explain, in one sentence each, why cases 6 and 7 were accepted.
Done when: 7/7 casos como esperado · replay dentro da validade: aceito.
E18 · Your site's policy
15 minCreate politica-bots.md with three lines, one per case, starting with anônimo:, assinado e conhecido: and assinado e desconhecido:, each with what the site does (allow, limit, block, on which pages). The prefixes stay in Portuguese because the check command looks for them.
Done when: grep -c -E "^(anônimo|assinado e conhecido|assinado e desconhecido):" politica-bots.md → 3.
06Lesson quiz
Question 1 of 4
What does a valid Web Bot Auth signature prove?skill
Correct
The draft (§4.1) is explicit: it says who holds the key, not whether it is benign or authorized. And within the validity window there can be a replay.Not this one
The draft (§4.1) is explicit: it says who holds the key, not whether it is benign or authorized. And within the validity window there can be a replay.Review: From the agent that signs to the site's policyQuestion 2 of 4
Why was the minimal signature (only @authority) accepted on /admin in case 7?
Correct
§5.2: covering only @authority, the signature is valid for any method, path and body on that origin until it expires. Cover @method and @path.Not this one
§5.2: covering only @authority, the signature is valid for any method, path and body on that origin until it expires. Cover @method and @path.Review: The draft's vector, redoneQuestion 3 of 4
What is the status of Web Bot Auth on October 19, 2026?
Correct
draft-ietf-webbotauth-httpsig-protocol-00, published September 1, 2026, expires March 5, 2027. Stable base: RFC 9421 (HTTP Message Signatures).Not this one
draft-ietf-webbotauth-httpsig-protocol-00, published September 1, 2026, expires March 5, 2027. Stable base: RFC 9421 (HTTP Message Signatures).Review: From the agent that signs to the site's policyQuestion 4 of 4
On Cloudflare, what changes when the agent is Intermediary?
Correct
Direct: one operator. Intermediary: a service that many users control (transitive trust). Your site's policy can treat the two differently.Not this one
Direct: one operator. Intermediary: a service that many users control (transitive trust). Your site's policy can treat the two differently.Review: Where this already shows upQuiz complete
You got {a} of {n} right. Get them all right and the lesson is marked as complete.Choose an answer. The explanation appears after you try.
07In three sentences
SignatureProves who holds the URL's key, not intent or permission.
CoverageShort validity, @method and @path covered; replay exists.
PolicyAnonymous, known, and unknown: three rules of yours.