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feat(captain): MCP controller aceita Bearer token além de HMAC

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Hermes Agent (cliente MCP) usa `--auth header` que envia
`Authorization: Bearer <token>` — padrão MCP. Antes o Captain MCP server
só aceitava HMAC-SHA256 (X-Hub-Signature-256), incompatível com o que
Hermes manda nativamente.

Agora aceita qualquer um dos 2 modos:
- Bearer token (recomendado, padrão MCP) — Hermes envia automaticamente
- HMAC-SHA256 do body — pra clientes que preferem assinar payload

Ambos validados com ActiveSupport::SecurityUtils.secure_compare contra
o mesmo CAPTAIN_MCP_SECRET. Sem secret = validação desabilitada (PoC/dev).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Rodribm10 2026-05-01 15:42:57 -03:00
parent 23911ea878
commit 713bb16012
1 changed files with 24 additions and 7 deletions
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31
app/controllers/webhooks/captain/mcp_controller.rb
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@ -8,9 +8,13 @@
# Conexão pelo Hermes:
# hermes mcp add captain-tools --url http://CAPTAIN_HOST/webhooks/captain/mcp
#
# Auth: HMAC-SHA256 do body via header `X-Hub-Signature-256`, secret
# compartilhado via env var `CAPTAIN_MCP_SECRET` (igual ao padrão de
# `hermes_callback`). Quando vazio, validação é desabilitada (PoC/dev).
# Auth: aceita 2 modos (qualquer um basta):
# - Bearer token (padrão MCP, recomendado): `Authorization: Bearer <CAPTAIN_MCP_SECRET>`
# É o que `hermes mcp add --auth header` usa nativamente.
# - HMAC-SHA256 do body: `X-Hub-Signature-256: sha256=<hex>`
# Para clientes que preferem assinar o body inteiro.
# Secret compartilhado via env var `CAPTAIN_MCP_SECRET`. Quando vazio,
# validação é desabilitada (PoC/dev).
#
# Multi-tenant: o cliente MCP pode mandar contexto (conversation_id,
# inbox_id, account_id) num campo de extensão chamado `_captain_context`
@ -50,13 +54,26 @@ class Webhooks::Captain::McpController < ApplicationController
secret = ENV.fetch('CAPTAIN_MCP_SECRET', nil)
return true if secret.blank?
return true if bearer_token_matches?(secret)
return true if hmac_signature_matches?(secret)
head :unauthorized
end
def bearer_token_matches?(secret)
auth_header = request.headers['Authorization'].to_s
return false unless auth_header.start_with?('Bearer ')
token = auth_header.delete_prefix('Bearer ').strip
ActiveSupport::SecurityUtils.secure_compare(token, secret)
end
def hmac_signature_matches?(secret)
signature = request.headers['X-Hub-Signature-256'].to_s
return head :unauthorized if signature.blank?
return false if signature.blank?
expected = "sha256=#{OpenSSL::HMAC.hexdigest('SHA256', secret, request.raw_post)}"
return head :unauthorized unless ActiveSupport::SecurityUtils.secure_compare(signature, expected)
true
ActiveSupport::SecurityUtils.secure_compare(signature, expected)
end
# Cliente MCP pode mandar contexto multi-tenant em params._captain_context.