Add ADR-029/030, implementation tasks, and spec updates for admin socket removal

Security review #005 identified critical vulnerabilities in the Unix domain
socket admin API (C1 symlink race, C2 no auth, C3 info leak, W1-W7, S1-S6).
ADR-028 (already accepted) replaces the socket with an authenticated HTTP
admin API on the health check port. This commit adds the remaining spec work:

- ADR-029: Config file TOCTOU mitigation (mtime check on reload)
- ADR-030: Store cli_allow_wildcard_bind in ConfigReloadHandle for consistent
  reload validation
- Implementation tasks for the admin HTTP migration (fix/admin-http-api),
  TOCTOU fix (fix/config-reload-toctou), and wildcard flag fix
  (fix/wildcard-flag-reload)
- Updated review #005 status to resolved with per-finding disposition
- Resolved OQ-16: POST for state-changing admin endpoints, GET for read-only
- Updated all architecture docs to reference new ADRs, use admin_key_path
  instead of admin_socket_path, and reflect POST method for /admin/reload
This commit is contained in:
2026-06-15 05:19:42 +00:00
parent 9096ec5873
commit 161049a17d
21 changed files with 1210 additions and 119 deletions

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---
id: fix/admin-http-api
name: Replace Unix domain socket admin API with authenticated HTTP admin API (ADR-028)
status: open
depends_on: []
scope: broad
risk: high
impact: component
level: implementation
review_findings: [C1, C2, C3, W1, W3, W4, S1, S2, S3, S4, S5, S6]
adr: [028]
---
## Description
Replace the Unix domain socket admin API (`src/admin/socket.rs`) with
authenticated HTTP endpoints on the existing health check listener. This
eliminates the entire class of filesystem-based vulnerabilities identified in
security review #005 (C1 symlink race, C2 no authentication, C3 info leak, W1
no concurrency limit, W3 path validation, W4 is_socket_active side effect, and
S1S6 suggestions).
ADR-028 defines the replacement design. The health check listener on
`127.0.0.1:9900` already runs an axum router. Admin endpoints are added behind
Bearer token authentication middleware.
### Changes Required
**Remove:**
- `src/admin/socket.rs` — entire file (826 lines of Unix socket code)
- `src/admin/mod.rs` — current re-exports (`AdminSocket`, `AdminSocketError`,
`start_admin_socket`)
**Add:**
- `src/admin/auth.rs` — Bearer token middleware:
- `AdminAuthConfig` struct holding `Option<String>` for the SHA-256 hash of
the admin key (or `None` to disable admin endpoints)
- `admin_auth_middleware` axum middleware that validates `Authorization:
Bearer <token>` against the stored hash using `subtle::ConstantTimeEq`
- Returns 404 when admin is disabled (empty `admin_key_path`), 401 on
missing/wrong token, passes through on valid token
- `load_admin_key(path: &str) -> Result<Option<[u8; 32]>, AdminKeyError>`
function that reads the key file, hashes it with SHA-256, and returns
the hash. Returns `None` if path is empty (disabled). Logs a warning
and returns `None` if the file doesn't exist or is unreadable (admin
endpoints disabled, process continues starting).
- `src/admin/handler.rs` — HTTP handlers:
- `reload_handler(State<...>) -> Json<ReloadResponse>` — **POST** `/admin/reload`.
Triggers `ConfigReloadHandle::reload()`, returns `{"status": "ok"}` or
`{"status": "error", "message": "reload failed"}`. Generic error
messages only; details logged server-side.
- `status_handler(State<...>) -> Json<StatusResponse>` — **GET**
`/admin/status`. Returns
`{"status": "ok", "uptime_secs": N, "sites": N}`
- `rotate_key_handler(State<...>) -> Json<RotateKeyResponse>` — **POST**
`/admin/rotate-key`. Generates new 256-bit random key, returns plaintext
in response, replaces stored hash in memory. Returns
`{"status": "ok", "key": "<hex>"}`.
**Modify:**
- `src/admin/mod.rs` — re-export `AdminAuthConfig`, `AdminKeyError`,
`admin_auth_middleware`, `load_admin_key`, and the handler functions
- `src/health.rs` — expand `health_router()` to `admin_router()` that nests
admin routes under `/admin` with auth middleware. Merge into the health
check listener. The full router becomes:
```
/health → health_handler (GET, no auth)
/admin/* → auth middleware → admin handlers (POST for state-changing, GET for read-only)
```
The `start_health_check_listener` function signature changes to accept
`Option<Arc<AdminAuthConfig>>` and `Arc<ConfigReloadHandle>` and
`Arc<ArcSwap<[u8; 32]>>` for key rotation. If `AdminAuthConfig` is `None`,
`/admin/*` routes return 404.
- `src/main.rs` — remove admin socket initialization entirely (lines 102-127).
Add admin key loading step after config parsing:
```rust
let admin_auth = if !static_config.admin_key_path.is_empty() {
match admin::load_admin_key(&static_config.admin_key_path) {
Ok(Some(hash)) => Some(Arc::new(AdminAuthConfig { admin_key_hash: hash })),
Ok(None) => None, // disabled
Err(e) => {
warn!("admin key load failed, disabling admin endpoints: {}", e);
None
}
}
} else {
None
};
```
Pass `admin_auth`, `reload_handle`, and `start_time` to
`start_health_check_listener`.
- `src/config/static_config.rs` — replace `admin_socket_path` field with
`admin_key_path`:
```rust
#[serde(default = "default_admin_key_path")]
pub admin_key_path: String,
```
Default: `"/etc/reverse-proxy/admin-key"`. Empty string disables admin
endpoints.
- `src/config/dynamic_config.rs` — `ConfigReloadHandle` gains
`cli_allow_wildcard_bind: bool` field (see task `fix/wildcard-flag-reload`).
No other changes needed — `reload()` method stays the same.
- `src/config/validation.rs` — add validation that `admin_key_path` is empty
or an absolute path (no `..` traversal, no relative paths). This is a new
validation rule.
- `Cargo.toml` — add `subtle` and `sha2` dependencies (already in overview.md)
**Tests:**
- Replace all `src/admin/socket.rs` tests with HTTP-based tests using
`reqwest` (already a dev dependency). Test:
- POST `/admin/reload` with valid Bearer token returns `{"status": "ok"}`
- POST `/admin/reload` with wrong token returns 401
- POST `/admin/reload` with no token returns 401
- POST `/admin/reload` when admin disabled returns 404
- GET `/admin/status` with valid token returns uptime and site count
- POST `/admin/rotate-key` with valid token returns new key and updates stored
hash
- POST `/admin/rotate-key` subsequent requests use the new key (old key returns
401)
- GET `/health` always returns 200 regardless of auth state
**Deployment:**
- `deploy/docker-compose.yml` — remove `/run/reverse-proxy` socket volume,
add `/etc/reverse-proxy/admin-key:/etc/reverse-proxy/admin-key:ro` volume
- `deploy/reverse-proxy.service` — remove any socket directory setup
- `deploy/README.md` — replace `socat` commands with `curl` examples
## Acceptance Criteria
- [ ] `src/admin/socket.rs` is deleted entirely
- [ ] `src/admin/auth.rs` implements Bearer token auth with constant-time
comparison and SHA-256 hashing
- [ ] `src/admin/handler.rs` implements `/admin/reload` (POST),
`/admin/status` (GET), `/admin/rotate-key` (POST)
- [ ] `src/health.rs` serves both `/health` (no auth) and `/admin/*`
(auth required) on port 9900
- [ ] `src/config/static_config.rs` uses `admin_key_path` (not
`admin_socket_path`)
- [ ] `src/main.rs` loads admin key at startup, passes auth config to
health check listener
- [ ] Admin disabled (`admin_key_path` empty or file missing) → `/admin/*`
returns 404
- [ ] Wrong/missing Bearer token → 401
- [ ] Error responses are generic (no filesystem paths, no config details)
- [ ] Full error details logged server-side only
- [ ] Key rotation works in-memory (new key replaces stored hash, old key
rejected)
- [ ] Key rotation does not persist across restarts (documented behavior)
- [ ] SIGHUP reload continues to work unchanged
- [ ] All existing tests pass (minus deleted socket tests)
- [ ] New HTTP-based admin tests pass
- [ ] `cargo clippy` passes with no warnings
- [ ] Deployment files updated (docker-compose, systemd, README)
## References
- docs/architecture/decisions/028-admin-http-api.md — ADR-028
- docs/architecture/decisions/014-unix-socket-reload.md — superseded ADR
- docs/architecture/decisions/027-admin-socket-resource-limits.md — deprecated
- docs/architecture/operations.md — admin HTTP endpoint, key management
- docs/architecture/config.md — admin_key_path, StaticConfig
- docs/architecture/overview.md — crate dependencies, architecture diagram
- docs/reviews/005-admin-socket-security-review.md — C1, C2, C3, W1, W3, W4
- src/admin/socket.rs — code to remove
- src/health.rs — code to extend
- src/main.rs — admin socket init to remove/replace
- src/config/static_config.rs — field rename
## Notes
> This is the primary implementation task for the admin socket → HTTP API
> migration. It directly implements ADR-028 and resolves findings C1, C2, C3,
> W1, W3, W4, S1S6 from security review #005.
>
> W2 (config TOCTOU) and W5 (wildcard flag) are independent fixes tracked in
> separate tasks.
>
> The `subtle` and `sha2` crates are already listed in the architecture spec
> (overview.md crate dependencies). Add them to `Cargo.toml` with appropriate
> versions.
## Summary
> To be filled on completion

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---
id: fix/agents-md-project-structure
name: Update AGENTS.md project structure and common modifications after admin refactor
status: open
depends_on: [fix/admin-http-api]
scope: narrow
risk: low
impact: docs
level: documentation
review_findings: []
adr: [028]
---
## Description
After the admin socket → HTTP API migration, `AGENTS.md` needs updates to
reflect the new project structure, config format, and operational procedures.
### Changes Required
**Project Structure section** — Update to reflect new admin module layout:
```
src/
├── admin/
│ ├── auth.rs # Bearer token auth middleware (subtle, SHA-256)
│ ├── handler.rs # HTTP handlers for /admin/reload, /status, /rotate-key
│ └── mod.rs # Re-exports
```
Remove:
```
│ ├── socket.rs # REMOVED — was Unix domain socket admin API
```
**Key Architecture Concepts section** — Update the admin socket description:
- Replace "Unix domain socket (`admin_socket_path`)" with "Authenticated HTTP
admin API (`admin_key_path`) on health check port"
- Note that admin endpoints require Bearer token auth
- Note that `admin_key_path` empty string = disabled (returns 404)
**Config Format section** — Update:
- Replace `admin_socket_path` references with `admin_key_path`
- Note that `admin_key_path` default is `/etc/reverse-proxy/admin-key`
- Add key file format info (plaintext, one line, read once at startup)
**Common Modifications section** — Replace:
```bash
# Before (Unix socket)
echo "reload" | socat - UNIX-CONNECT:/run/reverse-proxy/admin.sock
# After (HTTP with Bearer token)
curl -H "Authorization: Bearer $ADMIN_KEY" http://127.0.0.1:9900/admin/reload
curl -H "Authorization: Bearer $ADMIN_KEY" http://127.0.0.1:9900/admin/status
```
**Build & Run section** — No changes needed (build commands unchanged).
**Testing section** — Note that admin tests now use HTTP (reqwest) instead of
Unix socket (tokio::net::UnixStream).
## Acceptance Criteria
- [ ] Project structure shows `auth.rs` and `handler.rs`, not `socket.rs`
- [ ] Key architecture concepts mention `admin_key_path` and Bearer token auth
- [ ] Config format section mentions `admin_key_path`
- [ ] Common modifications section uses `curl` examples, not `socat`
- [ ] No references to `admin_socket_path` remain in AGENTS.md
## References
- AGENTS.md — current project structure and common modifications
- docs/architecture/decisions/028-admin-http-api.md — ADR-028
## Notes
> Depends on `fix/admin-http-api` being complete so the new file names are
> accurate.
## Summary
> To be filled on completion

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---
id: fix/config-reload-toctou
name: Add mtime check to config reload to detect mid-write file changes (ADR-029)
status: open
depends_on: []
scope: narrow
risk: low
impact: component
level: implementation
review_findings: [W2]
adr: [029]
---
## Description
Both the SIGHUP reload path (`src/shutdown.rs:handle_sighup_reload`) and the
admin HTTP reload path (`src/admin/socket.rs:handle_reload`, soon
`src/admin/handler.rs`) read the config file from disk with
`tokio::fs::read_to_string()`, then parse and apply it. If another process is
writing to the config file at the same time, the proxy could read a partially
written config.
ADR-029 specifies a simple mitigation: compare file modification timestamps
before and after reading. If mtime changed, reject the reload and return a
"please retry" message.
### Changes Required
**Shared reload function** — Extract the common file-read-and-validate logic
from `src/shutdown.rs:handle_sighup_reload()` and
`src/admin/socket.rs:handle_reload()` into a shared function (e.g.,
`src/config/dynamic_config.rs` or a new `src/config/reload.rs`):
```rust
pub async fn read_and_validate_config(
config_path: &str,
cli_allow_wildcard_bind: bool,
) -> Result<(StaticConfig, DynamicConfig), ReloadError> {
let metadata_before = tokio::fs::metadata(config_path).await
.map_err(ReloadError::Io)?;
let config_content = tokio::fs::read_to_string(config_path).await
.map_err(ReloadError::Io)?;
let metadata_after = tokio::fs::metadata(config_path).await
.map_err(ReloadError::Io)?;
if metadata_before.modified().ok() != metadata_after.modified().ok() {
return Err(ReloadError::FileChangedDuringRead);
}
let full_config = FullConfig::parse(&config_content)?;
let (new_static, new_dynamic) = full_config.into_static_and_dynamic();
validate(&new_static, &new_dynamic, cli_allow_wildcard_bind)?;
Ok((new_static, new_dynamic))
}
```
**`src/shutdown.rs`** — Replace inline file read + parse + validate with a
call to `read_and_validate_config()`. On `ReloadError::FileChangedDuringRead`,
log a warning: "config file changed during read, please retry SIGHUP".
**`src/admin/handler.rs`** (after admin-http-api task) — Same call. On
`ReloadError::FileChangedDuringRead`, return
`{"status": "error", "message": "config file changed during read, please retry"}`.
**Error type** — Define `ReloadError` enum with variants:
- `Io(std::io::Error)`
- `Parse(toml::de::Error)`
- `Validation(String)`
- `FileChangedDuringRead`
## Acceptance Criteria
- [ ] Both SIGHUP and admin HTTP reload paths use the same file-reading logic
- [ ] mtime is checked before and after reading the config file
- [ ] If mtime changed, reload is rejected with a clear error message
- [ ] Error message in admin HTTP response is generic ("config file changed
during read, please retry") — no filesystem paths leaked
- [ ] Full error details are logged server-side (path, mtime values)
- [ ] SIGHUP path logs the same error at warn level
- [ ] `cargo test` passes
- [ ] `cargo clippy` passes with no warnings
## References
- docs/architecture/decisions/029-config-reload-toctou.md — ADR-029
- docs/reviews/005-admin-socket-security-review.md — W2 finding
- src/shutdown.rs — handle_sighup_reload
- src/admin/socket.rs — handle_reload (to be replaced by admin/handler.rs)
## Notes
> This fix is independent of the admin socket → HTTP migration. It applies to
> both reload paths (SIGHUP and admin). The implementation should be done
> after or alongside the admin-http-api task since that task replaces
> socket.rs with handler.rs.
## Summary
> To be filled on completion

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---
id: fix/review-005-status-update
name: Update security review #005 status to reflect ADR-028 decision
status: open
depends_on: []
scope: narrow
risk: low
impact: docs
level: documentation
review_findings: [C1, C2, C3, W1, W3, W4, S1, S2, S3, S4, S5, S6]
adr: [028]
---
## Description
Security review #005 (`docs/reviews/005-admin-socket-security-review.md`) is
currently marked as `status: draft`. The review's architectural recommendation
to replace the Unix domain socket with an authenticated HTTP admin endpoint has
been accepted as ADR-028. The review findings should be annotated with their
resolution status.
### Changes Required
**`docs/reviews/005-admin-socket-security-review.md`**:
- Update frontmatter `status` from `draft` to the appropriate post-decision
status (e.g., `accepted` or `resolved`)
- Add a resolution section at the top of the document noting:
- C1, C2, C3, W1, W3, W4, S1S6: **Resolved by ADR-028** (replacing Unix
domain socket with authenticated HTTP admin API)
- W2 (config file TOCTOU): **Tracked separately** — ADR-029, task
`fix/config-reload-toctou`
- W5 (wildcard flag inconsistency): **Tracked separately** — ADR-030, task
`fix/wildcard-flag-reload`
- W6 (changed_fields in reload response): **Tracked** — will be implemented
as part of `fix/admin-http-api` (the new `/admin/reload` endpoint will
include changed_fields in its response per operations.md)
- W7 (health check port recon): **Accepted risk** — health check is
localhost-only, returns minimal information. The admin HTTP endpoint adds
authentication for `/admin/*` routes.
**`docs/reviews/006-attack-surface-review.md`**:
- Update Category 5 (Admin Socket) references from `src/admin/socket.rs` to
`src/admin/auth.rs` and `src/admin/handler.rs` (after admin-http-api task
is complete)
- Update entry 4.3 (admin reload config file) to reference the shared
`read_and_validate_config()` function with mtime check
- Remove or update entries that are eliminated by the socket removal (e.g.,
Category 4: Unix Domain Socket entries)
## Acceptance Criteria
- [ ] Review #005 frontmatter status updated
- [ ] Review #005 has a resolution section annotating each finding with its
disposition (resolved by ADR-028, tracked separately, accepted risk)
- [ ] Review #006 admin socket references updated (after admin-http-api task)
- [ ] No inline content removed — findings are annotated, not deleted
## References
- docs/reviews/005-admin-socket-security-review.md
- docs/reviews/006-attack-surface-review.md
- docs/architecture/decisions/028-admin-http-api.md
## Notes
> This task should be done after the `fix/admin-http-api` task is complete,
> since review #006 references need to point to the new file structure.
## Summary
> To be filled on completion

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---
id: fix/wildcard-flag-reload
name: Store cli_allow_wildcard_bind in ConfigReloadHandle for consistent reload validation (ADR-030)
status: open
depends_on: []
scope: narrow
risk: low
impact: component
level: implementation
review_findings: [W5]
adr: [030]
---
## Description
When the proxy starts with `--allow-wildcard-bind` (or `allow_wildcard_bind =
true` in config), bind addresses using `0.0.0.0` are accepted. But on config
reload, `validate()` is called with `cli_allow_wildcard_bind: false` — a
hardcoded value in `ConfigReloadHandle::reload()`. This means a config that was
valid at startup will be rejected on reload because the flag that enabled
wildcard binding is not preserved.
ADR-030 specifies storing `cli_allow_wildcard_bind` in `ConfigReloadHandle` at
construction time and using the stored value during reload validation.
### Changes Required
**`src/config/dynamic_config.rs`** — `ConfigReloadHandle` struct:
- Add `cli_allow_wildcard_bind: bool` field
- Update `ConfigReloadHandle::new()` to accept and store the flag:
```rust
pub fn new(
config: Arc<ArcSwap<DynamicConfig>>,
static_config: StaticConfig,
cli_allow_wildcard_bind: bool,
) -> Self {
Self {
config,
static_config: ArcSwap::from_pointee(static_config),
reload_mutex: Mutex::new(()),
cli_allow_wildcard_bind,
}
}
```
- In `reload()`, pass `self.cli_allow_wildcard_bind` to `validate()` instead
of `false`:
```rust
validate(&new_static, &new_dynamic, self.cli_allow_wildcard_bind)?;
```
**`src/main.rs`** — Update `ConfigReloadHandle::new()` call to pass
`cli_allow_wildcard_bind` from the loaded config:
```rust
let reload_handle = Arc::new(ConfigReloadHandle::new(
config_arc.clone(),
loaded_config.static_config.clone(),
loaded_config.cli_allow_wildcard_bind, // or args.allow_wildcard_bind
));
```
The `cli_allow_wildcard_bind` value should be the OR of the config flag and
the CLI flag, matching the startup validation logic. Check `src/cli.rs` for
how the flag is currently handled.
**`src/admin/socket.rs`** (or `src/admin/handler.rs` after migration) — Same
change: pass the flag through to `ConfigReloadHandle::new()`.
**`src/config/validation.rs`** — No changes needed; `validate()` already
accepts `cli_allow_wildcard_bind: bool` and uses it correctly.
**Tests** — Update all `ConfigReloadHandle::new()` calls to include the new
parameter. Add a test that verifies:
1. A config with `0.0.0.0` bind address is accepted on reload when
`cli_allow_wildcard_bind: true`
2. A config with `0.0.0.0` bind address is rejected on reload when
`cli_allow_wildcard_bind: false`
## Acceptance Criteria
- [ ] `ConfigReloadHandle` has a `cli_allow_wildcard_bind: bool` field
- [ ] `ConfigReloadHandle::new()` accepts and stores `cli_allow_wildcard_bind`
- [ ] `reload()` passes `self.cli_allow_wildcard_bind` to `validate()`
(not hardcoded `false`)
- [ ] All `ConfigReloadHandle::new()` call sites pass the correct flag
- [ ] Config with `0.0.0.0` bind address is accepted on reload when flag is
true (test)
- [ ] Config with `0.0.0.0` bind address is rejected on reload when flag is
false (test)
- [ ] `cargo test` passes
- [ ] `cargo clippy` passes with no warnings
## References
- docs/architecture/decisions/030-wildcard-flag-consistency.md — ADR-030
- docs/reviews/005-admin-socket-security-review.md — W5 finding
- docs/architecture/config.md — validation rules, allow_wildcard_bind
- src/config/dynamic_config.rs — ConfigReloadHandle
- src/config/validation.rs — validate()
- src/cli.rs — CLI flag handling
## Notes
> This fix is independent of the admin socket → HTTP migration. It should be
> applied to `ConfigReloadHandle` regardless of which admin interface is used.
> The implementation is straightforward: add a field, pass it through.
>
> The flag value should be `allow_wildcard_bind || cli_allow_wildcard_bind`
> (OR logic) matching the startup behavior documented in config.md.
## Summary
> To be filled on completion