diff --git a/skills/mcp/mcp-oauth-remote-gateway/SKILL.md b/optional-skills/mcp/mcp-oauth-remote-gateway/SKILL.md similarity index 93% rename from skills/mcp/mcp-oauth-remote-gateway/SKILL.md rename to optional-skills/mcp/mcp-oauth-remote-gateway/SKILL.md index 11fc14b964bd..a2e43865ed51 100644 --- a/skills/mcp/mcp-oauth-remote-gateway/SKILL.md +++ b/optional-skills/mcp/mcp-oauth-remote-gateway/SKILL.md @@ -1,13 +1,14 @@ --- name: mcp-oauth-remote-gateway -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. +description: Manual OAuth for remote MCP servers on headless gateways. version: 1.0.0 -author: Hermes Agent +author: Ben Barclay (benbarclay), Hermes Agent license: MIT +platforms: [linux, macos] metadata: hermes: - tags: [MCP, OAuth, PKCE, remote-deployment] - related_skills: [native-mcp, mcporter] + tags: [MCP, OAuth, PKCE, Remote-Deployment] + related_skills: [native-mcp, mcporter, fastmcp] --- # MCP OAuth on a Remote Hermes Gateway @@ -57,6 +58,23 @@ Symptoms to recognize: `[xdg-open] ` processes under the hermes user, a 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:`, 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 :127.0.0.1: @` + 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 @@ -102,6 +120,11 @@ Do the OAuth dance manually, then write the resulting tokens into the exact file 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 diff --git a/skills/mcp/mcp-oauth-remote-gateway/references/stripe-mcp-oauth-revocation.md b/optional-skills/mcp/mcp-oauth-remote-gateway/references/stripe-mcp-oauth-revocation.md similarity index 100% rename from skills/mcp/mcp-oauth-remote-gateway/references/stripe-mcp-oauth-revocation.md rename to optional-skills/mcp/mcp-oauth-remote-gateway/references/stripe-mcp-oauth-revocation.md diff --git a/skills/mcp/mcp-oauth-remote-gateway/scripts/diagnose-oauth-mcp.py b/optional-skills/mcp/mcp-oauth-remote-gateway/scripts/diagnose-oauth-mcp.py similarity index 100% rename from skills/mcp/mcp-oauth-remote-gateway/scripts/diagnose-oauth-mcp.py rename to optional-skills/mcp/mcp-oauth-remote-gateway/scripts/diagnose-oauth-mcp.py diff --git a/tests/skills/test_mcp_oauth_remote_gateway_skill.py b/tests/skills/test_mcp_oauth_remote_gateway_skill.py new file mode 100644 index 000000000000..8292b12b394f --- /dev/null +++ b/tests/skills/test_mcp_oauth_remote_gateway_skill.py @@ -0,0 +1,231 @@ +"""Tests for the mcp-oauth-remote-gateway optional skill. + +Covers the diagnose-oauth-mcp.py decision tree (TOKEN_OK / REFRESH_FIXED / +SESSION_REVOKED / REFRESH_DEAD), the HERMES_HOME resolution fallback, the +atomic --write persistence path, and SKILL.md frontmatter invariants. +No live network calls — urllib is mocked throughout. +""" +from __future__ import annotations + +import importlib.util +import io +import json +import re +import sys +import urllib.error +from pathlib import Path +from unittest.mock import patch + +import pytest + +SKILL_DIR = ( + Path(__file__).resolve().parents[2] + / "optional-skills" + / "mcp" + / "mcp-oauth-remote-gateway" +) +SCRIPT_PATH = SKILL_DIR / "scripts" / "diagnose-oauth-mcp.py" +SKILL_MD = SKILL_DIR / "SKILL.md" + + +def load_module(): + spec = importlib.util.spec_from_file_location("diagnose_oauth_mcp", SCRIPT_PATH) + module = importlib.util.module_from_spec(spec) + assert spec.loader is not None + sys.modules[spec.name] = module + spec.loader.exec_module(module) + return module + + +class FakeResponse: + def __init__(self, status=200, body=b"{}", headers=None): + self.status = status + self._body = body + self.headers = headers or {} + + def read(self): + return self._body + + +def _write_token_files(tokens_dir: Path, server="stripe", resource="https://mcp.example.com", + refresh_token="rt-1"): + tokens_dir.mkdir(parents=True, exist_ok=True) + tok = { + "access_token": "at-stored", + "token_type": "Bearer", + "expires_in": 3600, + "refresh_token": refresh_token, + "scope": "read", + "resource": resource, + "expires_at": 0, + } + if refresh_token is None: + del tok["refresh_token"] + (tokens_dir / f"{server}.json").write_text(json.dumps(tok)) + (tokens_dir / f"{server}.client.json").write_text( + json.dumps({"client_id": "cid-1", "token_endpoint_auth_method": "none"}) + ) + return tok + + +def _run_main(mod, tokens_dir, argv, responses): + """Run mod.main() with urlopen mocked; returns captured stdout. + + ``responses`` is a list consumed in call order; each item is either a + FakeResponse or an Exception to raise. + """ + calls = [] + + def fake_urlopen(req, timeout=None): + calls.append(req) + item = responses.pop(0) + if isinstance(item, Exception): + raise item + return item + + with patch.object(mod.os, "environ", dict(mod.os.environ, HERMES_HOME=str(tokens_dir.parent))), \ + patch.object(mod.urllib.request, "urlopen", side_effect=fake_urlopen), \ + patch.object(sys, "argv", ["diagnose-oauth-mcp.py", *argv]): + # Force the env-var fallback path (ignore any importable hermes_constants). + with patch.object(mod, "_hermes_home", lambda: str(tokens_dir.parent)): + buf = io.StringIO() + from contextlib import redirect_stdout + with redirect_stdout(buf): + mod.main() + return buf.getvalue(), calls + + +def _init_ok_body(): + return json.dumps({"jsonrpc": "2.0", "id": 1, + "result": {"serverInfo": {"name": "x"}, "capabilities": {}}}).encode() + + +def _init_revoked_error(code=401): + body = json.dumps({"error": {"code": -32002, "message": "Session expired. Please re-authenticate."}}).encode() + return urllib.error.HTTPError("https://mcp.example.com", code, "Unauthorized", + {"WWW-Authenticate": 'Bearer error="invalid_token"'}, + io.BytesIO(body)) + + +def test_token_ok_branch(tmp_path): + mod = load_module() + tokens_dir = tmp_path / "mcp-tokens" + _write_token_files(tokens_dir) + out, calls = _run_main(mod, tokens_dir, ["stripe"], [FakeResponse(200, _init_ok_body())]) + assert "BRANCH=TOKEN_OK" in out + assert len(calls) == 1 # never touched the token endpoint + + +def test_refresh_dead_no_refresh_token(tmp_path): + mod = load_module() + tokens_dir = tmp_path / "mcp-tokens" + _write_token_files(tokens_dir, refresh_token=None) + out, _ = _run_main(mod, tokens_dir, ["stripe"], [_init_revoked_error()]) + assert "BRANCH=REFRESH_DEAD" in out + + +def test_refresh_dead_invalid_grant(tmp_path): + mod = load_module() + tokens_dir = tmp_path / "mcp-tokens" + _write_token_files(tokens_dir) + grant_err = urllib.error.HTTPError( + "https://as.example.com/token", 400, "Bad Request", {}, + io.BytesIO(json.dumps({"error": "invalid_grant"}).encode())) + out, _ = _run_main( + mod, tokens_dir, + ["stripe", "--token-endpoint", "https://as.example.com/token"], + [_init_revoked_error(), grant_err], + ) + assert "BRANCH=REFRESH_DEAD" in out + assert "invalid_grant" in out + + +def test_refresh_fixed_branch_without_write_does_not_persist(tmp_path): + mod = load_module() + tokens_dir = tmp_path / "mcp-tokens" + _write_token_files(tokens_dir) + refreshed = json.dumps({"access_token": "at-new", "token_type": "Bearer", + "expires_in": 7200, "scope": "read"}).encode() + out, _ = _run_main( + mod, tokens_dir, + ["stripe", "--token-endpoint", "https://as.example.com/token"], + [_init_revoked_error(), FakeResponse(200, refreshed), FakeResponse(200, _init_ok_body())], + ) + assert "BRANCH=REFRESH_FIXED" in out + # No --write → stored file untouched + on_disk = json.loads((tokens_dir / "stripe.json").read_text()) + assert on_disk["access_token"] == "at-stored" + # Secret values are never printed + assert "at-new" not in out + assert "at-stored" not in out + assert "rt-1" not in out + + +def test_refresh_fixed_write_persists_atomically(tmp_path): + mod = load_module() + tokens_dir = tmp_path / "mcp-tokens" + _write_token_files(tokens_dir) + refreshed = json.dumps({"access_token": "at-new", "token_type": "Bearer", + "expires_in": 7200, "scope": "read write", + "refresh_token": "rt-rotated"}).encode() + out, _ = _run_main( + mod, tokens_dir, + ["stripe", "--token-endpoint", "https://as.example.com/token", "--write"], + [_init_revoked_error(), FakeResponse(200, refreshed), FakeResponse(200, _init_ok_body())], + ) + assert "BRANCH=REFRESH_FIXED" in out + on_disk = json.loads((tokens_dir / "stripe.json").read_text()) + assert on_disk["access_token"] == "at-new" + assert on_disk["refresh_token"] == "rt-rotated" + assert on_disk["scope"] == "read write" + assert on_disk["expires_at"] > 0 + assert not (tokens_dir / "stripe.json.tmp").exists() # atomic replace, no leftover + mode = (tokens_dir / "stripe.json").stat().st_mode & 0o777 + assert mode == 0o600 + + +def test_session_revoked_branch(tmp_path): + mod = load_module() + tokens_dir = tmp_path / "mcp-tokens" + _write_token_files(tokens_dir) + refreshed = json.dumps({"access_token": "at-new", "token_type": "Bearer", + "expires_in": 7200}).encode() + out, _ = _run_main( + mod, tokens_dir, + ["stripe", "--token-endpoint", "https://as.example.com/token"], + [_init_revoked_error(), FakeResponse(200, refreshed), _init_revoked_error()], + ) + assert "BRANCH=SESSION_REVOKED" in out + # New token failed too — file must not have been mutated + on_disk = json.loads((tokens_dir / "stripe.json").read_text()) + assert on_disk["access_token"] == "at-stored" + + +def test_hermes_home_env_fallback(tmp_path, monkeypatch): + mod = load_module() + monkeypatch.setenv("HERMES_HOME", str(tmp_path / "custom-home")) + # Block the hermes_constants import so the env fallback is exercised + with patch.dict(sys.modules, {"hermes_constants": None}): + home = mod._hermes_home() + assert home == str(tmp_path / "custom-home") + + +def test_requests_send_httpx_user_agent(tmp_path): + """Cloudflare 403s bare urllib UAs — every request must carry the httpx UA.""" + mod = load_module() + tokens_dir = tmp_path / "mcp-tokens" + _write_token_files(tokens_dir) + _, calls = _run_main(mod, tokens_dir, ["stripe"], [FakeResponse(200, _init_ok_body())]) + for req in calls: + assert req.get_header("User-agent") == mod.UA + + +def test_skill_md_frontmatter_invariants(): + yaml = pytest.importorskip("yaml") + content = SKILL_MD.read_text() + assert content.startswith("---\n") + fm = yaml.safe_load(re.search(r"^---\n(.*?)\n---", content, re.DOTALL).group(1)) + assert len(fm["description"]) <= 60 + assert fm["description"].endswith(".") + assert "platforms" in fm and len(fm["platforms"]) >= 1 + assert fm["author"].split(",")[0].strip() != "Hermes Agent" # human credited first diff --git a/website/docs/reference/optional-skills-catalog.md b/website/docs/reference/optional-skills-catalog.md index fea4afb46311..94416573dc23 100644 --- a/website/docs/reference/optional-skills-catalog.md +++ b/website/docs/reference/optional-skills-catalog.md @@ -119,6 +119,7 @@ hermes skills uninstall | Skill | Description | |-------|-------------| | [**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... | +| [**mcp-oauth-remote-gateway**](/docs/user-guide/skills/optional/mcp/mcp-mcp-oauth-remote-gateway) | Manual OAuth for remote MCP servers on headless gateways. | | [**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. | ## migration diff --git a/website/docs/user-guide/skills/optional/mcp/mcp-mcp-oauth-remote-gateway.md b/website/docs/user-guide/skills/optional/mcp/mcp-mcp-oauth-remote-gateway.md new file mode 100644 index 000000000000..e2157f4b84e7 --- /dev/null +++ b/website/docs/user-guide/skills/optional/mcp/mcp-mcp-oauth-remote-gateway.md @@ -0,0 +1,389 @@ +--- +title: "Mcp Oauth Remote Gateway — Manual OAuth for remote MCP servers on headless gateways" +sidebar_label: "Mcp Oauth Remote Gateway" +description: "Manual OAuth for remote MCP servers on headless gateways" +--- + +{/* 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. */} + +# Mcp Oauth Remote Gateway + +Manual OAuth for remote MCP servers on headless gateways. + +## Skill metadata + +| | | +|---|---| +| Source | Optional — install with `hermes skills install official/mcp/mcp-oauth-remote-gateway` | +| Path | `optional-skills/mcp/mcp-oauth-remote-gateway` | +| Version | `1.0.0` | +| Author | Ben Barclay (benbarclay), Hermes Agent | +| License | MIT | +| Platforms | linux, macos | +| Tags | `MCP`, `OAuth`, `PKCE`, `Remote-Deployment` | +| Related skills | `native-mcp`, [`mcporter`](/docs/user-guide/skills/optional/mcp/mcp-mcporter), [`fastmcp`](/docs/user-guide/skills/optional/mcp/mcp-fastmcp) | + +## Reference: full SKILL.md + +:::info +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. +::: + +# MCP OAuth on a Remote Hermes Gateway + +## Overview + +Hermes' built-in MCP OAuth client runs a one-shot HTTP listener on `127.0.0.1:` +inside the Hermes process and registers that loopback address as the OAuth +`redirect_uri`. That works perfectly for a local CLI on the user's own machine. +It breaks completely when Hermes runs as a remote gateway (container, VPS, +messaging bot), because the user's browser resolves `127.0.0.1` to the user's own +laptop, not the remote container — so the authorization code never reaches Hermes. + +This skill does the OAuth dance by hand and writes the resulting tokens into the +exact files Hermes' token storage expects, so a subsequent `/reload-mcp` finds +cached tokens and skips the browser flow entirely. + +## When to Use + +Use this skill when **all** of the following are true: + +1. The user wants to add a remote HTTP MCP server that requires OAuth (not a static Bearer token). +2. Hermes is running as a **remote gateway** (container, VPS, Docker, managed service) — NOT a local CLI on the user's laptop. +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. + +Do NOT use this for: +- **Local CLI Hermes** — just set `auth: oauth` in `mcp_servers.` and `/reload-mcp`. The built-in flow opens a browser and captures the callback on localhost. Works perfectly. +- **Servers that accept a static Bearer token (API key)** — always prefer `headers.Authorization: "Bearer "` when the user is willing. Simpler, no refresh dance. +- **GitHub Copilot MCP** (`api.githubcopilot.com/mcp/`) — GitHub does not expose DCR. Use a PAT or a pre-registered OAuth App (see pitfall 12). + +## Why the Built-in OAuth Flow Fails on a Remote Gateway + +Hermes' native MCP OAuth client (`tools/mcp_oauth.py`): + +1. Picks a free local port `P`. +2. Registers a dynamic OAuth client with the AS, sending `redirect_uri = http://127.0.0.1:P/callback`. +3. Starts an HTTP server on `127.0.0.1:P` **inside the Hermes process**. +4. Prints the authorize URL and waits for the code at its local endpoint. + +When Hermes runs remotely, the `127.0.0.1` in the `redirect_uri` is the remote +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] ` 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:`, 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 :127.0.0.1: @` + 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 `; 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:`, 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": "" +} +``` + +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=` (RFC 8707 — +many servers require this to bind the token to the specific MCP resource). Include +`scope=` 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/.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: + + +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=` + - `redirect_uri=` + - `client_id=` + - `code_verifier=` + - `resource=` (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`): + +**`.json`** — the `OAuthToken` pydantic model: +```json +{ + "access_token": "...", + "token_type": "Bearer", + "expires_in": 7200, + "refresh_token": "...", + "scope": "read write" +} +``` + +**`.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: + : + 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 +# 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__*` +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 `.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/.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 `.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 `.json` is frequently not "MCP-only" — `Authorization: Bearer ` 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. diff --git a/website/sidebars.ts b/website/sidebars.ts index 1843a924eb76..d92309fbd637 100644 --- a/website/sidebars.ts +++ b/website/sidebars.ts @@ -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', ], },