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Author SHA1 Message Date
Thomas Kosiewski b776a14b46 fix(coderd): harden OAuth2 provider security (#22194) 
## Summary

Harden the OAuth2 provider with multiple security fixes addressing
`coder/security#121` (CSRF session takeover) and converge on OAuth 2.1
compliance.

### Security Fixes

| Fix | Description | Commits |
|-----|-------------|---------|
| **CSRF on `/oauth2/authorize`** | Enforce CSRF protection on the
authorize endpoint POST (consent form submission) | `ba7d646`, `b94a64e`
|
| **Clickjacking: `frame-ancestors` CSP** | Prevent consent page from
being iframed (`Content-Security-Policy: frame-ancestors 'none'` +
`X-Frame-Options: DENY`) | `597aeb2` |
| **Exact redirect URI matching** | Changed from prefix matching to full
string exact matching per OAuth 2.1 §4.1.2.1 | `73d64b1`, `93897f1` |
| **Store & verify `redirect_uri`** | Store redirect_uri with auth code
in DB, verify at token exchange matches exactly (RFC 6749 §4.1.3) |
`50569b9`, `d7ca315` |
| **Mandatory PKCE** | Require `code_challenge` at authorization (for
`response_type=code`) + unconditional `code_verifier` verification at
token exchange | `d7ca315`, `1cda1a9` |
| **Reject implicit grant** | `response_type=token` now returns
`unsupported_response_type` error page (OAuth 2.1 removes implicit flow)
| `d7ca315`, `91b8863` |

### Changes by File

**`coderd/httpmw/csrf.go`** — Extended the CSRF `ExemptFunc` to enforce
CSRF on `/oauth2/authorize` in addition to `/api` routes. The consent
form POST is now CSRF-protected to prevent cross-site authorization code
theft.

**`site/site.go`** — Added `Content-Security-Policy: frame-ancestors
'none'` and `X-Frame-Options: DENY` headers to `RenderOAuthAllowPage`
(consent page only — does not affect the SPA/global CSP used by AI
tasks).

**`coderd/httpapi/queryparams.go`** — Changed `RedirectURL` from prefix
matching (`strings.HasPrefix(v.Path, base.Path)`) to full URI exact
matching (`v.String() != base.String()`), comparing scheme, host, path,
and query.

**`coderd/oauth2provider/authorize.go`** — Added PKCE enforcement:
`code_challenge` is required when `response_type=code` (via a
conditional check, not `RequiredNotEmpty`, so `response_type=token` can
reach the explicit rejection path). `ShowAuthorizePage` (GET) validates
`response_type` before rendering and returns a 400 error page for
unsupported types. `ProcessAuthorize` (POST) stores the `redirect_uri`
with the auth code when explicitly provided.

**`coderd/oauth2provider/tokens.go`** — PKCE verification is now
unconditional (not gated on `code_challenge` being present in DB). If
the stored code has a `redirect_uri`, the token endpoint verifies it
matches exactly — mismatch returns `errBadCode` → `invalid_grant`.
Missing `code_verifier` returns `invalid_grant`.

**`codersdk/oauth2.go`** — `OAuth2ProviderResponseTypeToken` constant
and `Valid()` acceptance are **kept** so the authorize handler can parse
`response_type=token` and return the proper `unsupported_response_type`
error rather than failing at parameter validation.

**`coderd/database/migrations/000421_*`** — Added `redirect_uri text`
column to `oauth2_provider_app_codes`.

### Design Decisions

**`state` parameter remains optional** — The plan initially required
`state` via `RequiredNotEmpty`, but this was reverted in `376a753` to
avoid breaking existing clients. The `state` is still hashed and stored
when provided (via `state_hash` column), securing clients that opt in.

**`response_type=token` kept in `Valid()`** — Removing it from `Valid()`
would cause the parameter parser to reject the request before the
authorize handler can return the proper `unsupported_response_type`
error. The constant is kept for correct error handling flow.

**CSP scoped to consent page only** — `frame-ancestors 'none'` is set
only on the OAuth consent page renderer, not globally. The SPA/global
CSP was previously changed to allow framing for AI tasks
([#18102](https://github.com/coder/coder/pull/18102)); this change does
not regress that.

### Out of Scope (follow-up PRs)

- Bearer tokens in query strings (needs internal caller audit)
- Scope enforcement on OAuth2 tokens
- Rate limiting on dynamic client registration


---

<details>
<summary>📋 Implementation Plan</summary>

# Plan: Harden OAuth2 Provider — Security Fixes + OAuth 2.1 Compliance

## Context & Why

Security issue `coder/security#121` reports a critical session takeover
via CSRF on the OAuth2 provider. This plan covers all remaining security
fixes from that issue **plus** convergence on OAuth 2.1 requirements.
The goal is a single PR that closes all actionable gaps.

## Current State (already committed on branch `csrf-sjx1`)

| Fix | Status | Commits |
|-----|--------|---------|
| Fix 1: CSRF on `/oauth2/authorize` | ✅ Done | `ba7d646`, `b94a64e` |
| CSRF token in consent form HTML | ✅ Done | `b94a64e` |
| `state_hash` column + storage | ✅ Done (hash stored, but state still
optional) | `9167d83`, `b94a64e` |
| Tests for CSRF + state hash | ✅ Done | `e4119b5` |

## Remaining Work

### ~~Fix 2 — Require `state` parameter~~ (DROPPED)

> **Decision:** Do not enforce `state` as required. The `state`
parameter is still hashed and stored when provided (via
`hashOAuth2State` / `state_hash` column from prior commits), but clients
are not forced to supply it. This avoids breaking existing integrations
that omit state.

**Rollback:** Remove `"state"` from the `RequiredNotEmpty` call in
`coderd/oauth2provider/authorize.go:42`:

```go
// BEFORE (current on branch)
p.RequiredNotEmpty("response_type", "client_id", "state", "code_challenge")

// AFTER
p.RequiredNotEmpty("response_type", "client_id", "code_challenge")
```

No test changes needed — tests already pass `state` voluntarily.

### Fix 4 — Exact redirect URI matching

Currently `coderd/httpapi/queryparams.go:233` uses prefix matching:

```go
// CURRENT — prefix match
if v.Host != base.Host || !strings.HasPrefix(v.Path, base.Path) {
```

OAuth 2.1 requires **exact string matching**. Change to:

```go
// AFTER — exact match (OAuth 2.1 §4.1.2.1)
if v.Host != base.Host || v.Path != base.Path {
```

**File: `coderd/httpapi/queryparams.go` — `RedirectURL` method**

Also update the error message from "must be a subset of" to "must
exactly match".

**Additionally**, store `redirect_uri` with the auth code and verify at
the token endpoint (RFC 6749 §4.1.3):

1. **New migration** (same migration file or a new `000421`): Add
`redirect_uri text` column to `oauth2_provider_app_codes`
2. **Update INSERT query** in `coderd/database/queries/oauth2.sql` to
include `redirect_uri`
3. **`coderd/oauth2provider/authorize.go`**: Store
`params.redirectURL.String()` when inserting the code
4. **`coderd/oauth2provider/tokens.go`**: After retrieving the code from
DB, verify that `redirect_uri` from the token request matches the stored
value exactly. Currently `tokens.go:103` calls `p.RedirectURL(vals,
callbackURL, "redirect_uri")` for prefix validation only — it must
compare against the stored redirect_uri from the code, not just the
app's callback URL.

<details>
<summary>Why both exact match AND store+verify?</summary>

Exact matching at the authorize endpoint prevents open redirectors
(attacker can't use a sub-path).
Storing and verifying at the token endpoint prevents code injection — an
attacker who steals a code can't exchange it with a different
redirect_uri than was originally authorized. This is required by RFC
6749 §4.1.3 and OAuth 2.1.
</details>

### Fix 7 — `frame-ancestors` CSP on consent page

The consent page can be iframed by a workspace app (same-site), which is
the attack vector. Add a `Content-Security-Policy` header to prevent
framing.

**File: `site/site.go` — `RenderOAuthAllowPage` function (~line 731)**

Before writing the response, add:

```go
func RenderOAuthAllowPage(rw http.ResponseWriter, r *http.Request, data RenderOAuthAllowData) {
    rw.Header().Set("Content-Type", "text/html; charset=utf-8")
    // Prevent the consent page from being framed to mitigate
    // clickjacking attacks (coder/security#121).
    rw.Header().Set("Content-Security-Policy", "frame-ancestors 'none'")
    rw.Header().Set("X-Frame-Options", "DENY")
    ...
```

Both headers for defense-in-depth (CSP for modern browsers,
X-Frame-Options for legacy).

### OAuth 2.1 — Mandatory PKCE

Currently PKCE is checked only when `code_challenge` was provided during
authorization (`tokens.go:258`):

```go
// CURRENT — conditional check
if dbCode.CodeChallenge.Valid && dbCode.CodeChallenge.String != "" {
    // verify PKCE
}
```

OAuth 2.1 requires PKCE for ALL authorization code flows. Change to:

**File: `coderd/oauth2provider/authorize.go`** — Add `"code_challenge"`
to required params:

```go
p.RequiredNotEmpty("response_type", "client_id", "code_challenge")
```

**File: `coderd/oauth2provider/tokens.go:257-265`** — Make PKCE
verification unconditional:

```go
// AFTER — PKCE always required (OAuth 2.1)
if req.CodeVerifier == "" {
    return codersdk.OAuth2TokenResponse{}, errInvalidPKCE
}
if !dbCode.CodeChallenge.Valid || dbCode.CodeChallenge.String == "" {
    // Code was issued without a challenge — should not happen
    // with the authorize endpoint enforcement, but defend in
    // depth.
    return codersdk.OAuth2TokenResponse{}, errInvalidPKCE
}
if !VerifyPKCE(dbCode.CodeChallenge.String, req.CodeVerifier) {
    return codersdk.OAuth2TokenResponse{}, errInvalidPKCE
}
```

**File: `codersdk/oauth2.go`** — Remove
`OAuth2ProviderResponseTypeToken` from the enum or reject it explicitly
in the authorize handler. Currently it's defined at line 216 but the
handler ignores `response_type` and always issues a code. We should
either:
- (a) Remove the `"token"` variant from the enum and reject it with
`unsupported_response_type`, OR
- (b) Add an explicit check in `ProcessAuthorize` that rejects
`response_type=token`

Option (b) is simpler and more backwards-compatible:

```go
// In ProcessAuthorize, after extracting params:
if params.responseType != codersdk.OAuth2ProviderResponseTypeCode {
    httpapi.WriteOAuth2Error(ctx, rw, http.StatusBadRequest,
        codersdk.OAuth2ErrorCodeUnsupportedResponseType,
        "Only response_type=code is supported")
    return
}
```

### OAuth 2.1 — Bearer tokens in query strings

`coderd/httpmw/apikey.go:743` accepts `access_token` from URL query
parameters. OAuth 2.1 prohibits this. However, this may be used
internally (e.g., workspace apps, DERP). Need to audit callers before
removing.

**Approach:** This is a larger change with potential breakage. Mark as a
**separate follow-up issue** rather than including in this PR. Document
the finding.

### OAuth 2.1 — Removed flows

✅ **Already compliant.** `tokens.go` only supports `authorization_code`
and `refresh_token` grant types. The implicit grant
(`response_type=token`) will be explicitly rejected per the PKCE section
above.

### OAuth 2.1 — Refresh token rotation

✅ **Already compliant.** `tokens.go:442` deletes the old API key when a
refresh token is used.

## Migration Plan

All DB changes can go in a single new migration (or extend 000420 if the
branch is rebased before merge). Columns to add:
- `redirect_uri text` on `oauth2_provider_app_codes`

The `state_hash` column is already added by migration 000420.

## Implementation Order

1. **Fix 7** — CSP headers on consent page (isolated, no deps)
2. ~~**Fix 2** — Require `state` parameter~~ (DROPPED — state stays
optional)
3. **Fix 4** — Exact redirect URI matching + store/verify redirect_uri
4. **PKCE mandatory** — Require `code_challenge` + reject
`response_type=token`
5. **Rollback** — Remove `"state"` from `RequiredNotEmpty` in
`authorize.go`
6. **Tests** — Update/add tests for all changes
7. **`make gen`** after DB changes

## Out of Scope (separate PRs)

- Bearer tokens in query strings (needs internal caller audit)
- Scope enforcement on OAuth2 tokens
- Rate limiting / quota on dynamic client registration

</details>

---
_Generated with [`mux`](https://github.com/coder/mux) • Model:
`anthropic:claude-opus-4-6` • Thinking: `xhigh`_
 2026-02-23 12:18:44 +01:00
Spike Curtis bddb808b25 chore: arrange imports in a standard way (#21452) 
Fixes all our Go file imports to match the preferred spec that we've _mostly_ been using. For example:

```
import (
	"context"
	"time"

	"github.com/prometheus/client_golang/prometheus"
	"golang.org/x/xerrors"
	"gopkg.in/natefinch/lumberjack.v2"

	"cdr.dev/slog/v3"
	"github.com/coder/coder/v2/codersdk/agentsdk"
	"github.com/coder/serpent"
)
```

3 groups: standard library, 3rd partly libs, Coder libs.

This PR makes the change across the codebase. The PR in the stack above modifies our formatting to maintain this state of affairs, and is a separate PR so it's possible to review that one in detail.
 2026-01-08 15:24:11 +04:00
Spike Curtis 49b34a716a fix: fix slog to always use array of Fields (#21426) 
Upgrades to slog v3 which includes a small, but backward incompatible API change to the acceptible call arguments when logging. This change allows us to verify via compile time type checking that arguments are correct and won't cause a panic, as was possible in slog v1, which this replaces (v2 was tagged but never used in coder/coder).

It also updates dependencies that also use slog and were updated.

I've left the `aibridge` dependency as a commit SHA, under the assumption that the team there (cc @pawbana @dannykopping ) will tag and update the dependency soon and on their own schedule.

Other dependencies, I pushed new tags.
 2026-01-08 10:29:41 +04:00
Zach 4d1003eace fix: remove initial global HTTP client usage (#20128) 
This PR makes the initial steps at removing usage of the global Go HTTP
client, which was seen to have impacts on test flakiness in
https://github.com/coder/internal/issues/1020. The first commit removes
uses from tests, with the exception of one test that is tightly coupled
to the default client. The second commit makes easy/low-risk removals
from application code. This should have some impact to reduce test flakiness.
 2025-10-02 11:43:13 -06:00
Danny Kopping 615585d5d1 feat: add aibridgedserver pkg (#19902) 2025-09-25 13:32:16 +02:00
Spike Curtis 192c81e8f9 chore: refactor codersdk to use SessionTokenProvider (#19565) 
Refactors `codersdk.Client`'s use of session tokens to use a `SessionTokenProvider`, which abstracts the obtaining and storing of the session token.

The main motiviation is to unify Agent authentication an an upstack PR, which can use cloud instance identity via token exchange, rather than a fixed session token.

However, the abstraction could also allow functionality like obtaining the session token from other external sources like the OS credential manager, or an external secret/key management system like Vault.
 2025-08-29 10:41:32 +02:00
Hugo Dutka 79cd80e5ca feat: add MCP tools for ChatGPT (#19102) 
Addresses https://github.com/coder/internal/issues/772.

Adds the toolset query parameter to the `/api/experimental/mcp/http` endpoint, which, when set to "chatgpt", exposes new `fetch` and `search` tools compatible with ChatGPT, as described in the
[ChatGPT docs](https://platform.openai.com/docs/mcp). These tools are
exposed in isolation because in my usage I found that ChatGPT refuses to
connect to Coder if it sees additional MCP tools.

<img width="1248" height="908" alt="Screenshot 2025-07-30 at 16 36 56"
src="https://github.com/user-attachments/assets/ca31e57b-d18b-4998-9554-7a96a141527a"
/>
 2025-08-04 14:11:22 +02:00
Thomas Kosiewski d1595781e1 fix: fix nil pointer dereference in ReportTask (#19045) 
This pull request addresses a bug related to a nil pointer dereference
in the task reporting functionality.

### Bug Fixes and Error Handling:

* Updated `RegisterTools` in `mcp.go` to skip registering the
`ReportTask` tool in the remote MCP context when a task reporter is not
configured, preventing potential nil pointer dereference panics.
* Added a check in `toolsdk.go` to ensure task reporting dependencies
are available before invoking the reporter, returning an appropriate
error if not.

### Test Coverage:

* Added `TestReportTaskNilPointerDeref` in `toolsdk_test.go` to verify
that the system does not panic when task reporting dependencies are
missing and instead returns a clear error message.
* Added `TestReportTaskWithReporter` in `toolsdk_test.go` to validate
correct behavior when a task reporter is configured, ensuring the
handler processes the request as expected.

Signed-off-by: Thomas Kosiewski <tk@coder.com>
 2025-07-28 11:23:29 +02:00
Thomas Kosiewski 494dccc510 feat: implement MCP HTTP server endpoint with authentication (#18670) 
# Add MCP HTTP server with streamable transport support

- Add MCP HTTP server with streamable transport support
- Integrate with existing toolsdk for Coder workspace operations
- Add comprehensive E2E tests with OAuth2 bearer token support
- Register MCP endpoint at /api/experimental/mcp/http with authentication
- Support RFC 6750 Bearer token authentication for MCP clients

Change-Id: Ib9024569ae452729908797c42155006aa04330af
Signed-off-by: Thomas Kosiewski <tk@coder.com>
 2025-07-03 19:27:41 +02:00