fix(logger): redact passwords and tokens from HTTP error log lines (#8013)

Resubmits #5820 by @echokos. The original PR's head fork could not
accept maintainer edits (organization-owned fork without cross-org
maintainer-edit access), so we've resubmitted the commits here with
original authorship preserved. Thanks to @echokos for the contribution.

---

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies; the
server is an Express app with structured HTTP logging via pino-http.
> - The middleware in `server/src/middleware/logger.ts` defines a
`customProps` hook that attaches request context (`req.body` /
`req.params` / `req.query`) to every 4xx/5xx log entry so operators can
diagnose failed requests.
> - That hook copies the body verbatim. Better Auth's `POST
/api/auth/sign-in/email` carries an `{ email, password }` body — on a
wrong-password attempt the request lands in the 4xx branch and the
plaintext password is written to `~/.paperclip/logs/server.log`.
> - Two existing issues raise this (#3072 plaintext-password leak, #4759
similar concerns) and neither has a fix.
> - Same exposure surface applies to sign-up, reset-password, API key
creation, and any endpoint that accepts a credential in the body and can
return 4xx.
> - This pull request introduces a small `redactSensitive` walker that
returns a shallow copy of the input with values for known
credential-shaped keys replaced with `[REDACTED]`, and applies it at
every body/params/query log site in `customProps`.
> - The benefit is that operators can keep diagnostic logging on without
their disk silently accumulating user passwords and bearer tokens.

## What Changed

- `server/src/middleware/redact-sensitive.ts` (new): depth-capped,
case-insensitive walker. Sensitive keys covered: `password`,
`currentPassword`, `newPassword`, `passwordConfirmation`,
`passwordConfirm`, `confirmPassword` (+ snake_case variants), `secret`,
`client_secret`, `access_token`, `refresh_token`, `id_token`,
`auth_token`, `session_token`, `api_key`, `authorization`,
`private_key`. Bare `token` deliberately not in the list — pagination
cursors and CSRF tokens are not credentials (per Greptile review).
- `server/src/middleware/logger.ts`: wraps the six log sites in
`customProps` (3 ctx-path + 3 fallback-path) with `redactSensitive`.
- `server/src/__tests__/redact-sensitive.test.ts` (new): covers
plaintext password, case-insensitive matching, multiple credential keys,
nested objects/arrays, bare `token` left untouched, primitives
untouched, cycle safety.
- Depth-cap returns `undefined` (field absent from log line) rather than
a sentinel string, per Greptile review.

## Verification

- `pnpm --filter @paperclipai/server test redact-sensitive` should run
the new test file green.
- Manual: tail `~/.paperclip/logs/server.log`, hit `POST
/api/auth/sign-in/email` with a deliberately wrong password, confirm the
logged `reqBody.password` reads `[REDACTED]` (not the plaintext) and the
surrounding fields still appear for diagnosis.

## Risks

Low. The walker only rewrites values at the log-emit boundary — the
actual `req.body` object handed to downstream handlers is unchanged
because `redactSensitive` returns a new object. Standard log fields
(email, route path, status code) remain visible. The sensitive-key list
is conservative enough that the only risk is over-redacting a
non-credential field that happens to share a name with a known
credential; the bare `token` carve-out in this revision addresses the
most obvious such case.

## Model Used

- Claude Opus 4.7 (`claude-opus-4-7`), Anthropic, extended thinking
mode, working through Claude Code CLI.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have searched GitHub for duplicate or related PRs and linked
them above
- [ ] I have run tests locally and they pass (no `node_modules` in my
disposable PR-prep checkout; CI vitest will exercise)
- [x] I have added or updated tests where applicable
- [ ] If this change affects the UI, I have included before/after
screenshots (N/A — server-only)
- [ ] I have updated relevant documentation to reflect my changes (no
doc surface affected)
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge

Closes #3072. Refs #4759.

---

## Original Context

`customProps` in the HTTP logger copies `req.body` / `req.params` /
`req.query` verbatim into 4xx/5xx log entries. Better Auth's
wrong-password flow therefore writes:

```
{"reqBody":{"email":"…","password":"founding6gomez6croaking"},"msg":"POST /api/auth/sign-in/email 401"}
```

…to disk. This PR rewrites credential-shaped values to `[REDACTED]` at
that boundary.

---

## Cross-references and status (maintainer)

Closes #5820
Closes #3095
Closes #4760
Closes #4886

---------

Co-authored-by: Aurora <aurora@majorimpact.com>
Co-authored-by: Paperclip <noreply@paperclip.ing>

server/src/__tests__/redact-sensitive.test.ts

@@ -0,0 +1,92 @@
+import { describe, expect, it } from "vitest";
+import { redactSensitive } from "../middleware/redact-sensitive.js";
+
+describe("redactSensitive", () => {
+  it("redacts a plaintext password field on a sign-in body", () => {
+    const body = { email: "user@example.com", password: "founding6gomez6croaking" };
+
+    const out = redactSensitive(body) as Record<string, unknown>;
+
+    expect(out.email).toBe("user@example.com");
+    expect(out.password).toBe("[REDACTED]");
+    expect((body as Record<string, unknown>).password).toBe("founding6gomez6croaking");
+  });
+
+  it("redacts password key regardless of casing", () => {
+    expect((redactSensitive({ Password: "x" }) as Record<string, unknown>).Password).toBe("[REDACTED]");
+    expect((redactSensitive({ PASSWORD: "x" }) as Record<string, unknown>).PASSWORD).toBe("[REDACTED]");
+  });
+
+  it("redacts known credential-shaped keys", () => {
+    const out = redactSensitive({
+      currentPassword: "a",
+      newPassword: "b",
+      access_token: "c",
+      refresh_token: "d",
+      api_key: "e",
+      authorization: "Bearer f",
+    }) as Record<string, string>;
+
+    for (const value of Object.values(out)) {
+      expect(value).toBe("[REDACTED]");
+    }
+  });
+
+  it("does not redact a bare `token` field — pagination cursors and CSRF tokens are not credentials", () => {
+    const out = redactSensitive({ token: "next-page-cursor", limit: 20 }) as Record<string, unknown>;
+
+    expect(out.token).toBe("next-page-cursor");
+    expect(out.limit).toBe(20);
+  });
+
+  it("recurses into nested objects and arrays", () => {
+    const out = redactSensitive({
+      user: { email: "user@example.com", password: "secret-pass" },
+      tokens: [{ access_token: "t1" }, { access_token: "t2" }],
+    }) as Record<string, unknown>;
+
+    expect((out.user as Record<string, unknown>).email).toBe("user@example.com");
+    expect((out.user as Record<string, unknown>).password).toBe("[REDACTED]");
+    const tokens = out.tokens as Array<Record<string, unknown>>;
+    expect(tokens[0].access_token).toBe("[REDACTED]");
+    expect(tokens[1].access_token).toBe("[REDACTED]");
+  });
+
+  it("leaves primitives and non-sensitive keys untouched", () => {
+    const body = { email: "a@b.c", name: "Alice", count: 7, active: true, missing: null };
+
+    expect(redactSensitive(body)).toEqual(body);
+  });
+
+  it("returns primitives unchanged", () => {
+    expect(redactSensitive("hello")).toBe("hello");
+    expect(redactSensitive(42)).toBe(42);
+    expect(redactSensitive(null)).toBe(null);
+    expect(redactSensitive(undefined)).toBe(undefined);
+  });
+
+  it("caps recursion depth so cycles do not pin the logger", () => {
+    const cycle: Record<string, unknown> = { name: "root" };
+    cycle.self = cycle;
+
+    expect(() => redactSensitive(cycle)).not.toThrow();
+  });
+
+  it("omits deeply-nested arrays at the depth cap instead of leaking null entries to JSON", () => {
+    // Build an object whose array field is reached at MAX_DEPTH. Recursing
+    // into the array elements would exceed the cap; without the array-level
+    // guard, `value.map` would produce `[undefined, ...]` which JSON.stringify
+    // renders as `[null, ...]`. Object properties at the same cap are
+    // already absent from the JSON output (JSON.stringify skips undefined
+    // values on objects), so this test pins the array path to the same
+    // contract: silently absent, not visible as nulls.
+    let payload: Record<string, unknown> = { values: [1, 2, 3] };
+    for (let i = 0; i < 5; i++) payload = { nested: payload };
+
+    const out = redactSensitive(payload);
+
+    const json = JSON.stringify(out);
+    expect(json).not.toContain("null");
+    expect(json).not.toContain("[1,2,3]");
+  });
+});