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chore(skills/mcp-oauth-remote-gateway): move to optional-skills + modernize
- Move skills/mcp/ -> optional-skills/mcp/ (niche remote-deployment workflow; bundled tier is for daily-driver skills) - Frontmatter: description 421 -> 57 chars, add platforms gating [linux, macos] (bash pipelines + gateway hosts), credit Ben Barclay first in author - Document the built-in flow's own escape hatches (paste-back prompt, ssh -N -L port-forward) as cheap first fallbacks before manual token surgery; scope the skill to no-TTY messaging-gateway contexts - Frame execution through the terminal / execute_code tools - Tests: tests/skills/test_mcp_oauth_remote_gateway_skill.py covers all four diagnostic branches, atomic --write persistence, 0600 perms, httpx UA on the wire, no-secrets-in-stdout, and frontmatter invariants (9 passing) - Regen auto-gen docs page + one-line catalog row + sidebar entry (scoped; unrelated generator drift reverted)
This commit is contained in:
teknium1
Teknium
parent
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commit
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7 changed files with 649 additions and 4 deletions
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@ -1,13 +1,14 @@
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---
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name: mcp-oauth-remote-gateway
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description: Connect an OAuth-gated remote MCP server (Better Stack, Linear, Cloudflare, Datadog, Stripe, etc.) to Hermes when Hermes runs as a REMOTE gateway (container, VPS, messaging bot) where the built-in browser OAuth flow cannot capture the localhost callback. Manually performs RFC 7591 Dynamic Client Registration + RFC 7636 PKCE + authorization_code exchange and writes tokens in the exact schema Hermes persistence expects.
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description: Manual OAuth for remote MCP servers on headless gateways.
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version: 1.0.0
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author: Hermes Agent
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author: Ben Barclay (benbarclay), Hermes Agent
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license: MIT
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platforms: [linux, macos]
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metadata:
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hermes:
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tags: [MCP, OAuth, PKCE, remote-deployment]
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related_skills: [native-mcp, mcporter]
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tags: [MCP, OAuth, PKCE, Remote-Deployment]
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related_skills: [native-mcp, mcporter, fastmcp]
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---
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# MCP OAuth on a Remote Hermes Gateway
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@ -57,6 +58,23 @@ Symptoms to recognize: `[xdg-open] <defunct>` processes under the hermes user, a
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empty or missing tokens directory (`$HERMES_HOME/mcp-tokens/`), and a reload that
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responds without any "Added/Reconnected: X" line in `change_detail`.
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## Cheap First Fallbacks: the Built-in Flow's Own Escape Hatches
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Before any manual token surgery, check whether the built-in flow's fallbacks
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already cover the deployment. When Hermes detects a remote session it prints two
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options alongside the authorize URL (`tools/mcp_oauth.py`):
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1. **Paste-back** — on an interactive TTY, a stdin reader races the HTTP
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listener. The user authorizes, the browser fails to connect to
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`127.0.0.1:<port>`, and they paste the full address-bar URL
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(`?code=...&state=...`) back at the prompt. Works for SSH'd-in CLI sessions.
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2. **SSH port-forward** — `ssh -N -L <port>:127.0.0.1:<port> <user>@<host>`
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makes the redirect reach the remote listener normally.
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Both require an interactive terminal to the Hermes host. The rest of this skill
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is for when there is NO interactive TTY — Hermes running purely as a messaging
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gateway/bot where `/reload-mcp` triggers the flow with nobody at a prompt.
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## Preferred Front Door: the Hermes Dashboard (try this BEFORE manual token surgery)
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A remote Hermes gateway often also runs the **dashboard** web UI as a SEPARATE
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@ -102,6 +120,11 @@ Do the OAuth dance manually, then write the resulting tokens into the exact file
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Hermes' `HermesTokenStorage` would have written, so on `/reload-mcp` Hermes finds
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cached tokens and skips the browser flow entirely.
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Run the shell commands below through the `terminal` tool on the gateway host and
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do the Python steps (PKCE generation, token exchange, file writes) via
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`execute_code` or a `terminal` python3 invocation — file writes must happen in
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the SAME code block as the token exchange (see pitfall 16).
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### 1. Confirm it's a remote gateway
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```bash
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231
tests/skills/test_mcp_oauth_remote_gateway_skill.py
Normal file
231
tests/skills/test_mcp_oauth_remote_gateway_skill.py
Normal file
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@ -0,0 +1,231 @@
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"""Tests for the mcp-oauth-remote-gateway optional skill.
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Covers the diagnose-oauth-mcp.py decision tree (TOKEN_OK / REFRESH_FIXED /
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SESSION_REVOKED / REFRESH_DEAD), the HERMES_HOME resolution fallback, the
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atomic --write persistence path, and SKILL.md frontmatter invariants.
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No live network calls — urllib is mocked throughout.
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"""
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from __future__ import annotations
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import importlib.util
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import io
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import json
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import re
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import sys
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import urllib.error
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from pathlib import Path
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from unittest.mock import patch
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import pytest
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SKILL_DIR = (
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Path(__file__).resolve().parents[2]
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/ "optional-skills"
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/ "mcp"
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/ "mcp-oauth-remote-gateway"
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)
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SCRIPT_PATH = SKILL_DIR / "scripts" / "diagnose-oauth-mcp.py"
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SKILL_MD = SKILL_DIR / "SKILL.md"
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def load_module():
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spec = importlib.util.spec_from_file_location("diagnose_oauth_mcp", SCRIPT_PATH)
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module = importlib.util.module_from_spec(spec)
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assert spec.loader is not None
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sys.modules[spec.name] = module
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spec.loader.exec_module(module)
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return module
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class FakeResponse:
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def __init__(self, status=200, body=b"{}", headers=None):
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self.status = status
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self._body = body
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self.headers = headers or {}
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def read(self):
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return self._body
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def _write_token_files(tokens_dir: Path, server="stripe", resource="https://mcp.example.com",
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refresh_token="rt-1"):
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tokens_dir.mkdir(parents=True, exist_ok=True)
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tok = {
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"access_token": "at-stored",
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"token_type": "Bearer",
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"expires_in": 3600,
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"refresh_token": refresh_token,
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"scope": "read",
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"resource": resource,
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"expires_at": 0,
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}
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if refresh_token is None:
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del tok["refresh_token"]
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(tokens_dir / f"{server}.json").write_text(json.dumps(tok))
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(tokens_dir / f"{server}.client.json").write_text(
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json.dumps({"client_id": "cid-1", "token_endpoint_auth_method": "none"})
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)
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return tok
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def _run_main(mod, tokens_dir, argv, responses):
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"""Run mod.main() with urlopen mocked; returns captured stdout.
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``responses`` is a list consumed in call order; each item is either a
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FakeResponse or an Exception to raise.
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"""
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calls = []
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def fake_urlopen(req, timeout=None):
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calls.append(req)
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item = responses.pop(0)
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if isinstance(item, Exception):
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raise item
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return item
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with patch.object(mod.os, "environ", dict(mod.os.environ, HERMES_HOME=str(tokens_dir.parent))), \
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patch.object(mod.urllib.request, "urlopen", side_effect=fake_urlopen), \
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patch.object(sys, "argv", ["diagnose-oauth-mcp.py", *argv]):
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# Force the env-var fallback path (ignore any importable hermes_constants).
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with patch.object(mod, "_hermes_home", lambda: str(tokens_dir.parent)):
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buf = io.StringIO()
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from contextlib import redirect_stdout
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with redirect_stdout(buf):
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mod.main()
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return buf.getvalue(), calls
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def _init_ok_body():
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return json.dumps({"jsonrpc": "2.0", "id": 1,
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"result": {"serverInfo": {"name": "x"}, "capabilities": {}}}).encode()
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def _init_revoked_error(code=401):
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body = json.dumps({"error": {"code": -32002, "message": "Session expired. Please re-authenticate."}}).encode()
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return urllib.error.HTTPError("https://mcp.example.com", code, "Unauthorized",
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{"WWW-Authenticate": 'Bearer error="invalid_token"'},
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io.BytesIO(body))
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def test_token_ok_branch(tmp_path):
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mod = load_module()
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tokens_dir = tmp_path / "mcp-tokens"
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_write_token_files(tokens_dir)
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out, calls = _run_main(mod, tokens_dir, ["stripe"], [FakeResponse(200, _init_ok_body())])
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assert "BRANCH=TOKEN_OK" in out
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assert len(calls) == 1 # never touched the token endpoint
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def test_refresh_dead_no_refresh_token(tmp_path):
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mod = load_module()
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tokens_dir = tmp_path / "mcp-tokens"
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_write_token_files(tokens_dir, refresh_token=None)
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out, _ = _run_main(mod, tokens_dir, ["stripe"], [_init_revoked_error()])
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assert "BRANCH=REFRESH_DEAD" in out
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def test_refresh_dead_invalid_grant(tmp_path):
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mod = load_module()
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tokens_dir = tmp_path / "mcp-tokens"
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_write_token_files(tokens_dir)
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grant_err = urllib.error.HTTPError(
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"https://as.example.com/token", 400, "Bad Request", {},
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io.BytesIO(json.dumps({"error": "invalid_grant"}).encode()))
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out, _ = _run_main(
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mod, tokens_dir,
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["stripe", "--token-endpoint", "https://as.example.com/token"],
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[_init_revoked_error(), grant_err],
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)
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assert "BRANCH=REFRESH_DEAD" in out
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assert "invalid_grant" in out
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def test_refresh_fixed_branch_without_write_does_not_persist(tmp_path):
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mod = load_module()
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tokens_dir = tmp_path / "mcp-tokens"
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_write_token_files(tokens_dir)
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refreshed = json.dumps({"access_token": "at-new", "token_type": "Bearer",
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"expires_in": 7200, "scope": "read"}).encode()
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out, _ = _run_main(
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mod, tokens_dir,
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["stripe", "--token-endpoint", "https://as.example.com/token"],
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[_init_revoked_error(), FakeResponse(200, refreshed), FakeResponse(200, _init_ok_body())],
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)
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assert "BRANCH=REFRESH_FIXED" in out
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# No --write → stored file untouched
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on_disk = json.loads((tokens_dir / "stripe.json").read_text())
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assert on_disk["access_token"] == "at-stored"
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# Secret values are never printed
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assert "at-new" not in out
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assert "at-stored" not in out
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assert "rt-1" not in out
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def test_refresh_fixed_write_persists_atomically(tmp_path):
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mod = load_module()
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tokens_dir = tmp_path / "mcp-tokens"
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_write_token_files(tokens_dir)
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refreshed = json.dumps({"access_token": "at-new", "token_type": "Bearer",
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"expires_in": 7200, "scope": "read write",
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"refresh_token": "rt-rotated"}).encode()
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out, _ = _run_main(
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mod, tokens_dir,
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["stripe", "--token-endpoint", "https://as.example.com/token", "--write"],
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[_init_revoked_error(), FakeResponse(200, refreshed), FakeResponse(200, _init_ok_body())],
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)
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assert "BRANCH=REFRESH_FIXED" in out
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on_disk = json.loads((tokens_dir / "stripe.json").read_text())
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assert on_disk["access_token"] == "at-new"
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assert on_disk["refresh_token"] == "rt-rotated"
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assert on_disk["scope"] == "read write"
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assert on_disk["expires_at"] > 0
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assert not (tokens_dir / "stripe.json.tmp").exists() # atomic replace, no leftover
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mode = (tokens_dir / "stripe.json").stat().st_mode & 0o777
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assert mode == 0o600
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def test_session_revoked_branch(tmp_path):
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mod = load_module()
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tokens_dir = tmp_path / "mcp-tokens"
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_write_token_files(tokens_dir)
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refreshed = json.dumps({"access_token": "at-new", "token_type": "Bearer",
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"expires_in": 7200}).encode()
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out, _ = _run_main(
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mod, tokens_dir,
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["stripe", "--token-endpoint", "https://as.example.com/token"],
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[_init_revoked_error(), FakeResponse(200, refreshed), _init_revoked_error()],
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)
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assert "BRANCH=SESSION_REVOKED" in out
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# New token failed too — file must not have been mutated
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on_disk = json.loads((tokens_dir / "stripe.json").read_text())
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assert on_disk["access_token"] == "at-stored"
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def test_hermes_home_env_fallback(tmp_path, monkeypatch):
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mod = load_module()
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monkeypatch.setenv("HERMES_HOME", str(tmp_path / "custom-home"))
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# Block the hermes_constants import so the env fallback is exercised
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with patch.dict(sys.modules, {"hermes_constants": None}):
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home = mod._hermes_home()
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assert home == str(tmp_path / "custom-home")
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def test_requests_send_httpx_user_agent(tmp_path):
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"""Cloudflare 403s bare urllib UAs — every request must carry the httpx UA."""
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mod = load_module()
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tokens_dir = tmp_path / "mcp-tokens"
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_write_token_files(tokens_dir)
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_, calls = _run_main(mod, tokens_dir, ["stripe"], [FakeResponse(200, _init_ok_body())])
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for req in calls:
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assert req.get_header("User-agent") == mod.UA
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def test_skill_md_frontmatter_invariants():
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yaml = pytest.importorskip("yaml")
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content = SKILL_MD.read_text()
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assert content.startswith("---\n")
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fm = yaml.safe_load(re.search(r"^---\n(.*?)\n---", content, re.DOTALL).group(1))
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assert len(fm["description"]) <= 60
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assert fm["description"].endswith(".")
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assert "platforms" in fm and len(fm["platforms"]) >= 1
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assert fm["author"].split(",")[0].strip() != "Hermes Agent" # human credited first
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@ -119,6 +119,7 @@ hermes skills uninstall <skill-name>
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| Skill | Description |
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|-------|-------------|
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| [**fastmcp**](/docs/user-guide/skills/optional/mcp/mcp-fastmcp) | Build, test, inspect, install, and deploy MCP servers with FastMCP in Python. Use when creating a new MCP server, wrapping an API or database as MCP tools, exposing resources or prompts, or preparing a FastMCP server for Claude Code, Cur... |
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| [**mcp-oauth-remote-gateway**](/docs/user-guide/skills/optional/mcp/mcp-mcp-oauth-remote-gateway) | Manual OAuth for remote MCP servers on headless gateways. |
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| [**mcporter**](/docs/user-guide/skills/optional/mcp/mcp-mcporter) | Use the mcporter CLI to list, configure, auth, and call MCP servers/tools directly (HTTP or stdio), including ad-hoc servers, config edits, and CLI/type generation. |
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## migration
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@ -0,0 +1,389 @@
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---
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title: "Mcp Oauth Remote Gateway — Manual OAuth for remote MCP servers on headless gateways"
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sidebar_label: "Mcp Oauth Remote Gateway"
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description: "Manual OAuth for remote MCP servers on headless gateways"
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---
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{/* This page is auto-generated from the skill's SKILL.md by website/scripts/generate-skill-docs.py. Edit the source SKILL.md, not this page. */}
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# Mcp Oauth Remote Gateway
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Manual OAuth for remote MCP servers on headless gateways.
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## Skill metadata
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| | |
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|---|---|
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| Source | Optional — install with `hermes skills install official/mcp/mcp-oauth-remote-gateway` |
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| Path | `optional-skills/mcp/mcp-oauth-remote-gateway` |
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| Version | `1.0.0` |
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| Author | Ben Barclay (benbarclay), Hermes Agent |
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| License | MIT |
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| Platforms | linux, macos |
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| Tags | `MCP`, `OAuth`, `PKCE`, `Remote-Deployment` |
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| Related skills | `native-mcp`, [`mcporter`](/docs/user-guide/skills/optional/mcp/mcp-mcporter), [`fastmcp`](/docs/user-guide/skills/optional/mcp/mcp-fastmcp) |
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## Reference: full SKILL.md
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:::info
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The following is the complete skill definition that Hermes loads when this skill is triggered. This is what the agent sees as instructions when the skill is active.
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:::
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# MCP OAuth on a Remote Hermes Gateway
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## Overview
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Hermes' built-in MCP OAuth client runs a one-shot HTTP listener on `127.0.0.1:<port>`
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inside the Hermes process and registers that loopback address as the OAuth
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`redirect_uri`. That works perfectly for a local CLI on the user's own machine.
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It breaks completely when Hermes runs as a remote gateway (container, VPS,
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messaging bot), because the user's browser resolves `127.0.0.1` to the user's own
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laptop, not the remote container — so the authorization code never reaches Hermes.
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This skill does the OAuth dance by hand and writes the resulting tokens into the
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exact files Hermes' token storage expects, so a subsequent `/reload-mcp` finds
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cached tokens and skips the browser flow entirely.
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## When to Use
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Use this skill when **all** of the following are true:
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1. The user wants to add a remote HTTP MCP server that requires OAuth (not a static Bearer token).
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2. Hermes is running as a **remote gateway** (container, VPS, Docker, managed service) — NOT a local CLI on the user's laptop.
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3. The server supports OAuth 2.1 with PKCE and RFC 7591 Dynamic Client Registration (most modern MCP servers do — Better Stack, Linear, Cloudflare, Datadog, etc.). If it doesn't support DCR (GitHub is the notable exception), this skill does not apply — use a pre-registered OAuth App or a Personal Access Token instead.
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Do NOT use this for:
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- **Local CLI Hermes** — just set `auth: oauth` in `mcp_servers.<name>` and `/reload-mcp`. The built-in flow opens a browser and captures the callback on localhost. Works perfectly.
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- **Servers that accept a static Bearer token (API key)** — always prefer `headers.Authorization: "Bearer <token>"` when the user is willing. Simpler, no refresh dance.
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- **GitHub Copilot MCP** (`api.githubcopilot.com/mcp/`) — GitHub does not expose DCR. Use a PAT or a pre-registered OAuth App (see pitfall 12).
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## Why the Built-in OAuth Flow Fails on a Remote Gateway
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Hermes' native MCP OAuth client (`tools/mcp_oauth.py`):
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1. Picks a free local port `P`.
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2. Registers a dynamic OAuth client with the AS, sending `redirect_uri = http://127.0.0.1:P/callback`.
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3. Starts an HTTP server on `127.0.0.1:P` **inside the Hermes process**.
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4. Prints the authorize URL and waits for the code at its local endpoint.
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When Hermes runs remotely, the `127.0.0.1` in the `redirect_uri` is the remote
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container's loopback, not the user's. After authorizing, the user's browser 302s
|
||||
to `http://127.0.0.1:P/callback?code=...`, which resolves to the user's own
|
||||
laptop and fails to connect. The callback never reaches the Hermes process, the
|
||||
flow times out, and `/reload-mcp` returns "No MCP tools available" with no detail.
|
||||
|
||||
Symptoms to recognize: `[xdg-open] <defunct>` processes under the hermes user, an
|
||||
empty or missing tokens directory (`$HERMES_HOME/mcp-tokens/`), and a reload that
|
||||
responds without any "Added/Reconnected: X" line in `change_detail`.
|
||||
|
||||
## Cheap First Fallbacks: the Built-in Flow's Own Escape Hatches
|
||||
|
||||
Before any manual token surgery, check whether the built-in flow's fallbacks
|
||||
already cover the deployment. When Hermes detects a remote session it prints two
|
||||
options alongside the authorize URL (`tools/mcp_oauth.py`):
|
||||
|
||||
1. **Paste-back** — on an interactive TTY, a stdin reader races the HTTP
|
||||
listener. The user authorizes, the browser fails to connect to
|
||||
`127.0.0.1:<port>`, and they paste the full address-bar URL
|
||||
(`?code=...&state=...`) back at the prompt. Works for SSH'd-in CLI sessions.
|
||||
2. **SSH port-forward** — `ssh -N -L <port>:127.0.0.1:<port> <user>@<host>`
|
||||
makes the redirect reach the remote listener normally.
|
||||
|
||||
Both require an interactive terminal to the Hermes host. The rest of this skill
|
||||
is for when there is NO interactive TTY — Hermes running purely as a messaging
|
||||
gateway/bot where `/reload-mcp` triggers the flow with nobody at a prompt.
|
||||
|
||||
## Preferred Front Door: the Hermes Dashboard (try this BEFORE manual token surgery)
|
||||
|
||||
A remote Hermes gateway often also runs the **dashboard** web UI as a SEPARATE
|
||||
process (e.g. `hermes dashboard --host 0.0.0.0 --port <port>`; check with
|
||||
`ps aux | grep 'hermes dashboard'`). It exposes a connector/MCP console —
|
||||
endpoints like `/api/mcp/servers`, `/api/mcp/status`, and `/connectors` (all
|
||||
login-gated; a cookieless curl returning 401/302 confirms they exist).
|
||||
|
||||
**Why the dashboard solves the core problem:** when the user drives OAuth from
|
||||
the dashboard *in their own browser*, the redirect lands in a context the
|
||||
dashboard can capture — sidestepping the `127.0.0.1`-callback failure that breaks
|
||||
the CLI/manual flow. So the correct escalation order for "add or re-auth an OAuth
|
||||
MCP server on a remote gateway" is:
|
||||
|
||||
1. **Dashboard, in the user's browser** — the intended front door. Add servers, run OAuth, reload, all authenticated as the user. No copy-paste-callback dance, no hand-writing token files.
|
||||
2. **Manual token surgery (the rest of this skill)** — the FALLBACK for when there's no browser session to the dashboard (pure-chat/headless context).
|
||||
|
||||
**Finding the dashboard's PUBLIC URL.** The dashboard binds internally to
|
||||
`0.0.0.0:<port>`, but the user needs the externally-reachable URL. Most deploy
|
||||
platforms inject it into the environment — grep for it rather than making the
|
||||
user hunt:
|
||||
|
||||
```bash
|
||||
env | grep -iE "HERMES_DASHBOARD_PUBLIC_URL|RAILWAY_PUBLIC_DOMAIN|RAILWAY_STATIC_URL|RAILWAY_SERVICE_.*_URL|PUBLIC_URL|BASE_URL|DOMAIN" \
|
||||
| sed -E 's/(TOKEN|SECRET|KEY|PASSWORD)=.*/\1=***REDACTED***/I'
|
||||
```
|
||||
|
||||
`HERMES_DASHBOARD_PUBLIC_URL` is authoritative when present. On Railway also check
|
||||
`RAILWAY_PUBLIC_DOMAIN` / `RAILWAY_STATIC_URL` (the `*.up.railway.app` host) and
|
||||
`RAILWAY_SERVICE_*_URL` vars, which sometimes carry a friendlier custom domain.
|
||||
Hand the user the full `https://` URL and point them at the Connectors/MCP
|
||||
section. ALWAYS pipe through the `sed` redaction above — these env greps sit next
|
||||
to `*_TOKEN`/`*_SECRET` vars.
|
||||
|
||||
**What the dashboard does NOT fix (still host-side / shell):** stdio servers that
|
||||
need shell auth state (a CLI `login` command whose credentials may not persist
|
||||
across restarts) and anything reading credentials from `$HERMES_HOME/.env`. Those
|
||||
are out of the dashboard's scope regardless.
|
||||
|
||||
## The Workaround
|
||||
|
||||
Do the OAuth dance manually, then write the resulting tokens into the exact files
|
||||
Hermes' `HermesTokenStorage` would have written, so on `/reload-mcp` Hermes finds
|
||||
cached tokens and skips the browser flow entirely.
|
||||
|
||||
Run the shell commands below through the `terminal` tool on the gateway host and
|
||||
do the Python steps (PKCE generation, token exchange, file writes) via
|
||||
`execute_code` or a `terminal` python3 invocation — file writes must happen in
|
||||
the SAME code block as the token exchange (see pitfall 16).
|
||||
|
||||
### 1. Confirm it's a remote gateway
|
||||
|
||||
```bash
|
||||
env | grep -iE "HERMES|RAILWAY|CONTAINER"
|
||||
echo "$DISPLAY $WAYLAND_DISPLAY $SSH_CLIENT"
|
||||
```
|
||||
|
||||
No display + a remote indicator = remote gateway. `tools/mcp_oauth.py::_can_open_browser()`
|
||||
uses these same env vars, so if Hermes' own auto-detect says "headless", the
|
||||
built-in flow won't work.
|
||||
|
||||
### 2. Find HERMES_HOME and the config path
|
||||
|
||||
```bash
|
||||
HERMES_HOME=$(python3 -c 'from hermes_constants import get_hermes_home; print(get_hermes_home())')
|
||||
echo "config: $HERMES_HOME/config.yaml"
|
||||
echo "tokens: $HERMES_HOME/mcp-tokens/"
|
||||
```
|
||||
|
||||
### 3. Discover OAuth metadata from the MCP server
|
||||
|
||||
MCP servers advertise their OAuth setup via RFC 9728 (OAuth 2.0 Protected
|
||||
Resource Metadata). The `WWW-Authenticate` header on a 401 tells you where to look:
|
||||
|
||||
```bash
|
||||
curl -sI https://mcp.example.com | grep -i www-authenticate
|
||||
# → Bearer realm="mcp", resource_metadata="https://mcp.example.com/.well-known/oauth-protected-resource"
|
||||
```
|
||||
|
||||
**Not every server returns `WWW-Authenticate`.** Some return a bare
|
||||
`{"errors":["Unauthorized"]}` 401 with no auth-discovery hint. When that happens,
|
||||
probe well-known paths directly:
|
||||
|
||||
```bash
|
||||
for p in \
|
||||
/.well-known/oauth-protected-resource \
|
||||
/.well-known/oauth-authorization-server \
|
||||
/.well-known/openid-configuration ; do
|
||||
echo "=== $p ==="
|
||||
curl -s -A "python-httpx/0.27" "https://mcp.example.com$p" | head -c 400; echo
|
||||
done
|
||||
```
|
||||
|
||||
Fetch the resource metadata to get `authorization_servers`, then fetch the AS's
|
||||
`/.well-known/oauth-authorization-server` to get `authorization_endpoint`,
|
||||
`token_endpoint`, and `registration_endpoint`.
|
||||
|
||||
Pitfall: many servers sit behind Cloudflare and 403 bare `urllib` user agents.
|
||||
Always set `User-Agent: python-httpx/0.27` (or similar) on requests in this flow.
|
||||
|
||||
### 4. Dynamic Client Registration (RFC 7591)
|
||||
|
||||
POST to the `registration_endpoint` with:
|
||||
|
||||
```json
|
||||
{
|
||||
"client_name": "Hermes Agent (manual OAuth)",
|
||||
"redirect_uris": ["http://127.0.0.1:8765/callback"],
|
||||
"grant_types": ["authorization_code", "refresh_token"],
|
||||
"response_types": ["code"],
|
||||
"token_endpoint_auth_method": "none",
|
||||
"scope": "<scopes_from_resource_metadata>"
|
||||
}
|
||||
```
|
||||
|
||||
Omit `scope` entirely if the AS's `scopes_supported` is empty — see step 5
|
||||
pitfall. Use port `8765` (or any port — nothing will listen).
|
||||
`token_endpoint_auth_method: none` marks this as a public PKCE client. Save the
|
||||
returned `client_id`.
|
||||
|
||||
### 5. Build the authorize URL with PKCE
|
||||
|
||||
Generate:
|
||||
- `code_verifier`: `secrets.token_urlsafe(64)[:128]`
|
||||
- `code_challenge`: `base64url(sha256(code_verifier))` (no padding)
|
||||
- `state`: `secrets.token_urlsafe(24)`
|
||||
|
||||
Query params: `response_type=code`, `client_id`, `redirect_uri`, `code_challenge`,
|
||||
`code_challenge_method=S256`, `state`, plus `resource=<mcp_server_url>` (RFC 8707 —
|
||||
many servers require this to bind the token to the specific MCP resource). Include
|
||||
`scope=<space-separated>` ONLY if the AS metadata's `scopes_supported` is a
|
||||
non-empty array AND/OR the resource metadata declares specific scopes. If
|
||||
`scopes_supported: []`, omit the `scope` parameter — the server grants its full
|
||||
default set on its own. Fabricating scope strings against an empty
|
||||
`scopes_supported` can cause `invalid_scope` errors on some ASes.
|
||||
|
||||
**Stash `code_verifier` and `state` to disk** (e.g. `/tmp/.mcp-oauth-work/<server>.json`,
|
||||
0600 perms). You need them for step 7, possibly across multiple chat turns.
|
||||
|
||||
### 6. Give the user the authorize URL
|
||||
|
||||
```
|
||||
Open this URL in your browser:
|
||||
<authorize_url>
|
||||
|
||||
After approving, your browser will try to load http://127.0.0.1:8765/callback
|
||||
and fail to connect — THAT'S EXPECTED. Just copy the entire URL from the
|
||||
address bar (it will contain ?code=...&state=...) and paste it back here.
|
||||
```
|
||||
|
||||
### 7. Exchange the code for tokens
|
||||
|
||||
When the user pastes the callback URL:
|
||||
|
||||
1. Parse `code` and `state` from the query string.
|
||||
2. **Verify `state` matches the stashed value** (CSRF check — do not skip).
|
||||
3. POST `application/x-www-form-urlencoded` to the `token_endpoint`:
|
||||
- `grant_type=authorization_code`
|
||||
- `code=<from callback>`
|
||||
- `redirect_uri=<same as step 4>`
|
||||
- `client_id=<from step 4>`
|
||||
- `code_verifier=<stashed>`
|
||||
- `resource=<mcp_server_url>` (if the AS required it in step 5, include here too)
|
||||
4. Response contains `access_token`, `refresh_token`, `token_type`, `expires_in`, `scope`.
|
||||
|
||||
### 8. Write tokens in Hermes' exact schema
|
||||
|
||||
`tools/mcp_oauth.py::HermesTokenStorage` expects two files under
|
||||
`$HERMES_HOME/mcp-tokens/` (create dir with `0o700`, files with `0o600`):
|
||||
|
||||
**`<server_name>.json`** — the `OAuthToken` pydantic model:
|
||||
```json
|
||||
{
|
||||
"access_token": "...",
|
||||
"token_type": "Bearer",
|
||||
"expires_in": 7200,
|
||||
"refresh_token": "...",
|
||||
"scope": "read write"
|
||||
}
|
||||
```
|
||||
|
||||
**`<server_name>.client.json`** — the `OAuthClientInformationFull` model:
|
||||
```json
|
||||
{
|
||||
"client_id": "...",
|
||||
"redirect_uris": ["http://127.0.0.1:8765/callback"],
|
||||
"grant_types": ["authorization_code", "refresh_token"],
|
||||
"response_types": ["code"],
|
||||
"token_endpoint_auth_method": "none",
|
||||
"scope": "read write",
|
||||
"client_name": "..."
|
||||
}
|
||||
```
|
||||
|
||||
Write each file via `json.dumps(..., indent=2)`. Sanitize the filename with
|
||||
`re.sub(r'[^\w\-]', '_', server_name)[:128]` — this matches `_safe_filename()` in
|
||||
Hermes' token storage.
|
||||
|
||||
### 9. Add the server to config.yaml
|
||||
|
||||
```yaml
|
||||
mcp_servers:
|
||||
<name>:
|
||||
url: "https://mcp.example.com"
|
||||
auth: oauth
|
||||
timeout: 180
|
||||
connect_timeout: 60
|
||||
```
|
||||
|
||||
### 10. Smoke-test the token BEFORE asking the user to reload
|
||||
|
||||
Manually POST an MCP `initialize` request to confirm the token works end-to-end —
|
||||
this catches scope misconfigurations, wrong `resource` values, and CF blocks
|
||||
before the user is confused by another "No MCP tools available" reload:
|
||||
|
||||
```python
|
||||
body = json.dumps({
|
||||
"jsonrpc": "2.0", "id": 1, "method": "initialize",
|
||||
"params": {
|
||||
"protocolVersion": "2025-06-18",
|
||||
"capabilities": {},
|
||||
"clientInfo": {"name": "hermes-debug", "version": "1.0"},
|
||||
},
|
||||
}).encode()
|
||||
# POST to the MCP URL with:
|
||||
# Authorization: Bearer <access_token>
|
||||
# Accept: application/json, text/event-stream
|
||||
# Content-Type: application/json
|
||||
# MCP-Protocol-Version: 2025-06-18
|
||||
# User-Agent: python-httpx/0.27
|
||||
```
|
||||
|
||||
Expect HTTP 200 with `Content-Type: text/event-stream` and a JSON-RPC result
|
||||
containing `serverInfo` and `capabilities`. **Do not use `urllib` with its default
|
||||
UA** — Cloudflare will 403 you even though Hermes (which uses httpx) will succeed.
|
||||
`scripts/diagnose-oauth-mcp.py` automates this smoke test.
|
||||
|
||||
### 11. Tell the user to run `/reload-mcp`
|
||||
|
||||
On reload, Hermes sees `auth: oauth`, calls `HermesTokenStorage.get_tokens()`,
|
||||
finds your cached tokens, skips the browser flow, and registers `mcp_<name>_*`
|
||||
tools. Refresh happens automatically before `expires_in` elapses.
|
||||
|
||||
## Pitfalls & Lessons Learned
|
||||
|
||||
1. **Do not assume "headless" means "OAuth impossible."** The built-in flow works fine for local CLI; the issue is strictly remote deployments where the user's browser and the Hermes process are on different machines. Check the execution environment before claiming OAuth isn't an option.
|
||||
|
||||
2. **Read the source, not just the skill docs.** `tools/mcp_oauth.py` and the MCP config reference in `website/docs/` are the authoritative references. Grep the tree before telling the user a feature "doesn't exist."
|
||||
|
||||
3. **Cloudflare UA filter.** Many MCP/OAuth providers front their infra with Cloudflare, which 403s `python-urllib/*` user agents on metadata endpoints even though those endpoints are public. Set `User-Agent: python-httpx/0.27` (or any browser-like string) on every request in this flow. Hermes itself uses httpx, so this is never a problem in the real connection path.
|
||||
|
||||
4. **Include `resource` in both authorize and token requests.** RFC 8707 resource indicators are not optional for most modern MCP servers — they bind the issued token to the specific MCP resource URL. Leaving it out sometimes still works but may yield a token that later fails at the MCP server with a scope/audience error.
|
||||
|
||||
5. **Trailing slash matters.** Some servers advertise the resource as `https://mcp.example.com/` with a trailing slash and reject tokens issued against the no-slash variant. Copy the `resource` value verbatim from the `.well-known/oauth-protected-resource` response.
|
||||
|
||||
6. **`/reload-mcp` is silent on failure.** If the reload shows "No MCP tools available" with no `change_detail` line, a server is in config but failed to connect and no error bubbled up. Tail the error log, smoke-test the token directly with a manual `initialize` POST, and — if everything looks good — ask for a full process restart.
|
||||
|
||||
7. **Circuit breaker can survive `/reload-mcp`.** `tools/mcp_tool.py` keeps a module-level error-count dict with a small threshold. Once tripped (e.g. after token expiry produces several consecutive failures), the tool handler can short-circuit before calling the server, so no successful call resets the counter. Symptom: reload says "Reconnected: X" but subsequent calls still fail with "server unreachable" in the same conversation. Recovery order: try `/reload-mcp` FIRST (cheap, no chat-process blip) — on current builds it can clear the counter; only escalate to a full gateway process restart if a live call STILL short-circuits after reload. Do not lead with "you must restart."
|
||||
|
||||
8. **Refresh on an expired access_token + a tripped breaker is a deadlock.** The auto-refresh logic runs inside the MCP call path, which the breaker short-circuits once tripped. Manually refreshing the token on disk does not help by itself — pair a manual token refresh with a full restart, not a `/reload-mcp`.
|
||||
|
||||
9. **`invalid_grant` on a manual refresh means the refresh token is DEAD — re-auth is the only fix, do not loop.** When the access_token has been expired long enough, the refresh_token can also be revoked/expired server-side. A `grant_type=refresh_token` POST then returns HTTP 400 `{"error":"invalid_grant",...}` (wording varies: "Grant not found", "Token expired", "refresh token is invalid"). There is NO recovery from the gateway side. Hand back to the user with two options: (a) re-run the full manual OAuth dance (steps 3–10), or (b) if the provider offers a static personal API key, switch to that — no refresh/expiry cycle, more durable for an unattended remote gateway. Detect early: before any create/update operation against an OAuth MCP, check `expires_at` vs `time.time()`; if already expired, attempt the refresh first and surface `invalid_grant` immediately rather than failing mid-task.
|
||||
|
||||
10. **A successful refresh that STILL yields a rejected token = server-side SESSION revocation; only a fresh authorization_code flow fixes it.** Distinct from pitfall 9. The stored token file can look healthy (`expires_at` well out, refresh_token present), yet a live `initialize` POST returns `401 invalid_token` with a JSON-RPC body like `{"error":{"code":-32002,"message":"Session expired. Please re-authenticate."}}`. The `grant_type=refresh_token` POST may **succeed** (HTTP 200, new access_token) — yet the brand-new token gets the SAME `-32002`. The provider revoked the underlying MCP *session* server-side; the OAuth refresh chain re-mints credentials but cannot re-establish a revoked session. Decision rule when an OAuth MCP reports "not connected": (1) smoke-test the stored access_token with a manual `initialize` POST; (2) if `401 invalid_token`, attempt a refresh and smoke-test the NEW token; (3a) new token works → write it + restart to clear the breaker; (3b) new token STILL gets `-32002`/"Session expired" → stop, this is session revocation, hand the user the authorize URL for a full re-auth. `scripts/diagnose-oauth-mcp.py` automates steps 1–2 and prints which branch you're in. For an unattended gateway whose session keeps getting revoked, prefer a static Personal API key. See `references/stripe-mcp-oauth-revocation.md` for a worked example of a provider that revokes weekly.
|
||||
|
||||
11. **Client info file is NOT optional.** Hermes needs `<server>.client.json` to know the `client_id` for refresh grants. Skipping it means the first refresh fails and the user has to re-auth — writing both files is the whole point of this skill.
|
||||
|
||||
12. **Never hand-type the redirect URL for the user to open.** Generate the authorize URL programmatically with `urllib.parse.urlencode()`. Spaces in scopes and special chars in `state` break string-concatenated URLs.
|
||||
|
||||
13. **Security: the stash file contains the `code_verifier`.** Delete `/tmp/.mcp-oauth-work/<server>.json` immediately after successful token exchange. There's no reason to keep a proof-of-identity secret around once it's consumed.
|
||||
|
||||
14. **Write what the token endpoint actually returned.** The AS may grant a narrower (or wider) scope than requested. Write the `scope` from the token-exchange response to `<server>.json`, not what you asked for in step 5. When `scopes_supported: []`, the explicit scope list you send IS authoritative both ways: some servers grant exactly what you list (pass narrow scopes for least-privilege, or enumerate the full set if the user needs everything), and some won't echo the granted scope back at registration time — only the token-exchange response is authoritative.
|
||||
|
||||
15. **OAuth tokens often double as Bearer tokens against the provider's public REST API.** The access_token in `<server>.json` is frequently not "MCP-only" — `Authorization: Bearer <token>` against the provider's documented REST API succeeds whenever the corresponding resource scope was granted. This is the OAuth 2.0 spec, not a provider quirk. When the MCP server is read-only but you need a write operation, check whether the OAuth token can hit the provider's REST API directly before suggesting a separate API key.
|
||||
|
||||
16. **Secret redaction can mask tokens in tool output.** If secret redaction is enabled, tokens and long opaque strings render as `***` in tool-result output, so you cannot `print(response)` to keep the access_token visible across turns. Combined with single-use `code` values from authorization_code grants: if you print the token-exchange response, you may lose the token AND consume the code, forcing a restart with a fresh authorize URL. **Always write the access_token directly to its final destination file in the SAME code block that performs the token exchange.** If you must print for debugging, print only `len(access_token)`, `token_type`, `scope`, `expires_in` — never the secret.
|
||||
|
||||
17. **GitHub MCP (`api.githubcopilot.com/mcp/`) uses a pre-registered confidential OAuth App, not DCR + PKCE-public.** Its client info ships with a real `client_secret` and `token_endpoint_auth_method: client_secret_post`. The token-exchange POST to `https://github.com/login/oauth/access_token` must include `client_secret` as a form field alongside `client_id`, `code`, `code_verifier`, and `redirect_uri` (PKCE is still honored on top of the secret). The redirect URI is **fixed** in the OAuth App config — you cannot change it, so the manual listener-port trick doesn't apply; the user just lets the browser fail to connect on that port and pastes the address-bar URL back.
|
||||
|
||||
## What NOT to do
|
||||
|
||||
- **Don't use `mcp-remote` as a fallback.** It runs an npx subprocess whose OAuth callback server ALSO sits on the remote container's localhost — same problem. `mcp-remote` only helps when the MCP client doesn't speak remote HTTP at all (Hermes does natively).
|
||||
- **Don't push "paste your API token and I'll add headers"** if the user explicitly asked for OAuth. Offer the static-token shortcut only after explaining why the native OAuth flow fails in remote deployments. Respect the user's choice to do the extra legwork for rotation-free, scope-limited access.
|
||||
- **Don't claim Hermes doesn't support a feature without reading the source.** Grep the source tree before making capability claims.
|
||||
|
||||
## Quick Reference Files
|
||||
|
||||
- `scripts/diagnose-oauth-mcp.py` — re-runnable, read-only-by-default diagnostic. Given a server name, it smoke-tests the stored access_token, attempts a refresh, smoke-tests the new token, and prints exactly which recovery branch you're in (`TOKEN_OK` = breaker/restart, `REFRESH_FIXED` = persist+restart, `SESSION_REVOKED` = full re-auth, `REFRESH_DEAD` = full re-auth/API key). Pass `--write` to persist a working refreshed token atomically. Never prints secret values. **Run this FIRST when an OAuth MCP server reports "not connected"** — it encodes the pitfall 7/9/10 decision tree.
|
||||
- `references/stripe-mcp-oauth-revocation.md` — a worked example (Stripe) of a provider that revokes its OAuth session on a recurring basis, and the durable fix: switch to a static restricted API key.
|
||||
|
||||
## Related
|
||||
|
||||
- `native-mcp` — general guide to configuring MCP in Hermes. Authoritative config reference lives there.
|
||||
- `mcporter` — the external CLI bridge, for ad-hoc MCP calls outside of Hermes' config.
|
||||
|
|
@ -465,6 +465,7 @@ const sidebars: SidebarsConfig = {
|
|||
collapsed: true,
|
||||
items: [
|
||||
'user-guide/skills/optional/mcp/mcp-fastmcp',
|
||||
'user-guide/skills/optional/mcp/mcp-mcp-oauth-remote-gateway',
|
||||
'user-guide/skills/optional/mcp/mcp-mcporter',
|
||||
],
|
||||
},
|
||||
|
|
|
|||
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