feat(api): add passkey enrollment persistence layer

Phase 6 WebAuthn bind, enrollment-only slice (spec section 14). Adds the data
layer an already-authenticated principal needs to bind and manage passkeys:

- migration 0007: webauthn_credentials (one bound passkey per row, public
  attestation material only) and webauthn_challenges (server-stashed ceremony
  state between begin and finish, single-use via consumed_at). Both rows are
  bound to a known user_id; there is no usernameless login lookup, since the
  assertion/login path is a deferred slice.
- PasskeyCredential type and five Repo methods (create/consume challenge,
  create/list/delete credential) with the PG semantics the handlers rely on:
  supersede-prior-live on begin, expiry-before-consume single-use on finish,
  credential_id UNIQUE -> ErrConflict, owner-scoped delete -> ErrNotFound.
- ErrPasskeyChallengeInvalid sentinel for a missing/expired/consumed ceremony.

internal/api/errors.go

@@ -36,6 +36,12 @@ var (
 	// can answer 429 (back off / request a new code) rather than inviting another
 	// guess against a code that will never accept one.
 	ErrOTPLocked = errors.New("email code locked: too many attempts")
+	// ErrPasskeyChallengeInvalid means a passkey enrollment ceremony cannot be
+	// finished: there is no live (unconsumed, unexpired) challenge for the caller and
+	// purpose (Phase 6 WebAuthn bind). Like ErrOTPInvalid it is a client error — the
+	// finish endpoint exists; the ceremony state is gone (never begun, already
+	// consumed, or expired) — so handlers map it to 400, not 404.
+	ErrPasskeyChallengeInvalid = errors.New("passkey challenge invalid or expired")
 )
 
 // apiError is a handler-level error carrying an HTTP status and a stable,

internal/api/pgrepo.go

@@ -721,3 +721,149 @@ func (p *PGRepo) SetSetting(ctx context.Context, key string, value []byte) error
 		key, string(value))
 	return err
 }
+
+// ---- player passkey enrollment (spec §14 WebAuthn / Phase 6 bind, migration 0007) ----
+
+// CreatePasskeyChallenge supersedes any prior live challenge for (user, purpose) and
+// inserts the fresh one, in one transaction (mirrors CreateEmailOTP). The supersede
+// DELETE means a re-begin invalidates the earlier ceremony, so only the most recent
+// challenge can ever finish — at most one outstanding challenge per (user, purpose).
+// The opaque SessionData is held server-side so the client cannot forge the challenge
+// it must answer at finish.
+func (p *PGRepo) CreatePasskeyChallenge(ctx context.Context, id, userID, purpose string, sessionData []byte, expiresAt time.Time) error {
+	tx, err := p.db.BeginTx(ctx, nil)
+	if err != nil {
+		return err
+	}
+	defer tx.Rollback() //nolint:errcheck // no-op after commit
+
+	if _, err := tx.ExecContext(ctx,
+		`DELETE FROM webauthn_challenges WHERE user_id = $1 AND purpose = $2 AND consumed_at IS NULL`,
+		userID, purpose); err != nil {
+		return fmt.Errorf("supersede prior passkey challenge: %w", err)
+	}
+	if _, err := tx.ExecContext(ctx,
+		`INSERT INTO webauthn_challenges (id, user_id, purpose, session_data, expires_at)
+		 VALUES ($1, $2, $3, $4, $5)`,
+		id, userID, purpose, sessionData, expiresAt); err != nil {
+		return fmt.Errorf("insert passkey challenge: %w", err)
+	}
+	return tx.Commit()
+}
+
+// ConsumePasskeyChallengeByUser redeems the newest live (unconsumed, unexpired at now)
+// challenge for (user, purpose) in one transaction (mirrors VerifyEmailOTP). The row is
+// taken FOR UPDATE so a concurrent finish cannot double-spend it; expiry is checked
+// before consuming so a stale challenge is never accepted. On success consumed_at is
+// stamped (single-use) and the stashed SessionData is returned. No live row →
+// ErrPasskeyChallengeInvalid.
+func (p *PGRepo) ConsumePasskeyChallengeByUser(ctx context.Context, userID, purpose string, now time.Time) ([]byte, error) {
+	tx, err := p.db.BeginTx(ctx, nil)
+	if err != nil {
+		return nil, err
+	}
+	defer tx.Rollback() //nolint:errcheck // no-op after commit
+
+	var (
+		id          string
+		sessionData []byte
+		expiresAt   time.Time
+	)
+	switch err := tx.QueryRowContext(ctx,
+		`SELECT id, session_data, expires_at FROM webauthn_challenges
+		 WHERE user_id = $1 AND purpose = $2 AND consumed_at IS NULL
+		 ORDER BY created_at DESC LIMIT 1 FOR UPDATE`,
+		userID, purpose).Scan(&id, &sessionData, &expiresAt); {
+	case errors.Is(err, sql.ErrNoRows):
+		return nil, ErrPasskeyChallengeInvalid
+	case err != nil:
+		return nil, err
+	}
+
+	if !expiresAt.After(now) {
+		return nil, ErrPasskeyChallengeInvalid
+	}
+	if _, err := tx.ExecContext(ctx,
+		`UPDATE webauthn_challenges SET consumed_at = $2 WHERE id = $1`, id, now); err != nil {
+		return nil, fmt.Errorf("consume passkey challenge: %w", err)
+	}
+	if err := tx.Commit(); err != nil {
+		return nil, err
+	}
+	return sessionData, nil
+}
+
+// CreatePasskeyCredential stores a freshly verified passkey (enrollment). Only public
+// attestation material is written; a credential_id already bound to ANY account is left
+// untouched (ON CONFLICT DO NOTHING) and reported as ErrConflict via a zero RowsAffected,
+// so an authenticator is never silently rebound. Empty aaguid/name land as SQL NULL.
+func (p *PGRepo) CreatePasskeyCredential(ctx context.Context, c PasskeyCredential) error {
+	res, err := p.db.ExecContext(ctx,
+		`INSERT INTO webauthn_credentials (id, user_id, credential_id, public_key, sign_count, aaguid, name, created_at)
+		 VALUES ($1, $2, $3, $4, $5, NULLIF($6, ''), NULLIF($7, ''), $8)
+		 ON CONFLICT (credential_id) DO NOTHING`,
+		c.ID, c.UserID, c.CredentialID, c.PublicKey, int64(c.SignCount), c.AAGUID, c.Name, c.CreatedAt)
+	if err != nil {
+		return err
+	}
+	n, err := res.RowsAffected()
+	if err != nil {
+		return err
+	}
+	if n == 0 {
+		return ErrConflict
+	}
+	return nil
+}
+
+// PasskeyCredentialsForUser lists the passkeys a user has bound, newest first, for the
+// credential-management view. Nullable aaguid/name collapse to "" via COALESCE; the
+// nullable last_used_at maps to a *time.Time (nil until an assertion is verified).
+func (p *PGRepo) PasskeyCredentialsForUser(ctx context.Context, userID string) ([]PasskeyCredential, error) {
+	const q = `SELECT id, user_id, credential_id, public_key, sign_count,
+		COALESCE(aaguid, ''), COALESCE(name, ''), created_at, last_used_at
+		FROM webauthn_credentials WHERE user_id = $1 ORDER BY created_at DESC`
+	rows, err := p.db.QueryContext(ctx, q, userID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []PasskeyCredential
+	for rows.Next() {
+		var (
+			c         PasskeyCredential
+			signCount int64
+			lastUsed  sql.NullTime
+		)
+		if err := rows.Scan(&c.ID, &c.UserID, &c.CredentialID, &c.PublicKey, &signCount,
+			&c.AAGUID, &c.Name, &c.CreatedAt, &lastUsed); err != nil {
+			return nil, err
+		}
+		c.SignCount = uint32(signCount)
+		if lastUsed.Valid {
+			t := lastUsed.Time
+			c.LastUsedAt = &t
+		}
+		out = append(out, c)
+	}
+	return out, rows.Err()
+}
+
+// DeletePasskeyCredential removes the passkey row id, scoped to userID so a caller can
+// only unbind their OWN credential. No matching (user, id) row → ErrNotFound via a zero
+// RowsAffected, so a stale or cross-user id cannot silently no-op as success.
+func (p *PGRepo) DeletePasskeyCredential(ctx context.Context, userID, id string) error {
+	res, err := p.db.ExecContext(ctx,
+		`DELETE FROM webauthn_credentials WHERE id = $1 AND user_id = $2`, id, userID)
+	if err != nil {
+		return err
+	}
+	n, err := res.RowsAffected()
+	if err != nil {
+		return err
+	}
+	if n == 0 {
+		return ErrNotFound
+	}
+	return nil
+}

internal/api/repo.go

@@ -89,6 +89,26 @@ type StaffUser struct {
 	EmailVerified bool
 }
 
+// PasskeyCredential is one bound passkey (Phase 6 WebAuthn enrollment). It carries
+// only public, non-secret attestation material: a WebAuthn public key is meant to
+// be public (unlike a session token), so it is safe at rest. CredentialID is the
+// authenticator's globally-unique handle (base64url) and PublicKey the COSE key
+// (base64); SignCount is the uint32 signature counter captured at registration.
+// LastUsedAt is nil until an assertion is verified — the login/step-up path that
+// would stamp it is out of scope for this enrollment-only slice (deferred), so it
+// stays nil through the flow this type backs.
+type PasskeyCredential struct {
+	ID           string
+	UserID       string
+	CredentialID string
+	PublicKey    string
+	SignCount    uint32
+	AAGUID       string
+	Name         string
+	CreatedAt    time.Time
+	LastUsedAt   *time.Time
+}
+
 // SessionedUser is the projection resolved from a live session cookie: the
 // identity SessionAuth needs to build a Principal. It omits the password hash —
 // the session has already authenticated the caller — but carries the pending
@@ -196,6 +216,39 @@ type Repo interface {
 	// proven email is returned. now is the API clock so expiry is testable.
 	VerifyEmailOTP(ctx context.Context, userID, purpose, codeHash string, now time.Time) (email string, err error)
 
+	// ---- player passkey enrollment (spec §14 WebAuthn / Phase 6 bind) ----
+
+	// CreatePasskeyChallenge persists the server-side state of a credential-creation
+	// ceremony for (userID, purpose): the opaque go-webauthn SessionData blob and its
+	// expiry. Only the server holds it, so the client cannot forge the challenge it
+	// must answer at finish. It supersedes any prior live (unconsumed) challenge for
+	// the same (userID, purpose) so a re-begin invalidates the earlier ceremony —
+	// at most one outstanding challenge per (user, purpose). expiresAt is the API
+	// clock + TTL so expiry is driven by one authoritative clock.
+	CreatePasskeyChallenge(ctx context.Context, id, userID, purpose string, sessionData []byte, expiresAt time.Time) error
+	// ConsumePasskeyChallengeByUser redeems the newest live (unconsumed, unexpired at
+	// now) challenge for (userID, purpose), atomically: it stamps consumed_at and
+	// returns the stashed SessionData so finish can validate the attestation against
+	// it. No live challenge → ErrPasskeyChallengeInvalid. Single-use: a second finish
+	// for the same ceremony finds nothing live and fails. now is the API clock so
+	// expiry is testable. Bound to user_id — enrollment always has a principal, so
+	// there is no usernameless consume-by-hash variant (login is a deferred slice).
+	ConsumePasskeyChallengeByUser(ctx context.Context, userID, purpose string, now time.Time) (sessionData []byte, err error)
+	// CreatePasskeyCredential stores a freshly verified passkey for a user (Phase 6
+	// enrollment). It writes only public attestation material (credential_id,
+	// public_key, sign_count, aaguid) plus the caller's nickname. A credential_id
+	// already bound to ANY account → ErrConflict (the UNIQUE guard); the handler maps
+	// that to 409 rather than silently rebinding an authenticator.
+	CreatePasskeyCredential(ctx context.Context, c PasskeyCredential) error
+	// PasskeyCredentialsForUser lists the passkeys a user has bound, newest first, for
+	// the credential-management view. It returns only display fields (never a secret —
+	// a passkey carries none); LastUsedAt is nil where no assertion has been verified.
+	PasskeyCredentialsForUser(ctx context.Context, userID string) ([]PasskeyCredential, error)
+	// DeletePasskeyCredential removes the passkey row id, scoped to userID so a caller
+	// can only unbind their OWN credential. No matching (user, id) row → ErrNotFound,
+	// so a stale or cross-user id cannot silently no-op as success.
+	DeletePasskeyCredential(ctx context.Context, userID, id string) error
+
 	// ---- player game-login: username-collision reclaim (spec §B3) ----
 
 	// ReclaimUsername records a Mojang-priority username reclaim, atomically (spec

internal/store/migrations/0007_webauthn_credentials.sql

@@ -0,0 +1,58 @@
+-- Phase 6 passkey/WebAuthn bind (spec §14 WebAuthn, §B2 onboarding "link + email-OTP
+-- + passkey"). This is the ENROLLMENT data layer only: an already-authenticated
+-- principal binds a passkey to their account (the credential-creation ceremony),
+-- and manages the credentials they have bound. Email-OTP remains the fallback
+-- factor (migration 0004), so a player with no passkey is never locked out.
+--
+-- Scope boundary (deliberate): this slice covers ENROLLMENT only. Assertion
+-- verification for LOGIN — proving a passkey to mint/elevate a session from an
+-- unauthenticated state — is out of scope here and deferred. The spec keeps the two
+-- passkey surfaces distinct (§14: admin.* rides "Tunnel+Access，WebAuthn/posture",
+-- panel.* is "app 登录"; §B2 lists passkey among the player onboarding factors), so
+-- where the panel.* passkey relying-party boundary ultimately lands (felis-api vs.
+-- the Access edge) is a later decision, not settled by this migration. Accordingly
+-- this migration models only the authenticated enrollment ceremony: every challenge
+-- is bound to a known user_id, and there is no usernameless (pre-session) login
+-- lookup column. Adding a login path later would also need the felis_session
+-- honoring model in session.go extended.
+
+-- webauthn_credentials stores one bound passkey per row. The public key and the
+-- signature counter are attestation outputs captured at registration; only public,
+-- non-secret material is held (a WebAuthn public key is meant to be public, unlike
+-- the RCON password or a session token). credential_id is the authenticator's
+-- globally-unique handle, base64url-encoded; UNIQUE guards the (astronomically
+-- unlikely) cross-account collision and is the key a future login path would match.
+CREATE TABLE webauthn_credentials (
+  id            text PRIMARY KEY,                      -- opaque row id (crypto-random hex)
+  user_id       text NOT NULL REFERENCES users(id),
+  credential_id text NOT NULL UNIQUE,                  -- base64url(raw credential id)
+  public_key    text NOT NULL,                         -- base64(COSE public key bytes)
+  sign_count    bigint NOT NULL DEFAULT 0,             -- uint32 widened (overflows int4)
+  aaguid        text,                                  -- authenticator model id, for display only
+  name          text,                                  -- caller-supplied nickname ("My phone")
+  created_at    timestamptz NOT NULL DEFAULT now(),
+  last_used_at  timestamptz                            -- NULL until an assertion is verified (deferred login path)
+);
+
+-- The credential-management views list a user's bound passkeys, so index that lookup.
+CREATE INDEX webauthn_credentials_user_id_idx ON webauthn_credentials (user_id);
+
+-- webauthn_challenges holds the server-side ceremony state between begin and finish.
+-- The full go-webauthn SessionData blob (challenge, allowed credentials, expiry) is
+-- stashed here and reloaded at finish, so the client never echoes — and so cannot
+-- forge — the challenge it must answer (the same principle as email_otps.code_hash).
+-- Every row is bound to a known user_id (NOT NULL): enrollment always rides on an
+-- authenticated principal, so there is no usernameless consume-by-hash path. consumed_at
+-- enforces single-use; a fresh begin supersedes the prior live row for (user, purpose).
+CREATE TABLE webauthn_challenges (
+  id           text PRIMARY KEY,                       -- opaque row id (crypto-random hex)
+  user_id      text NOT NULL REFERENCES users(id),
+  purpose      text NOT NULL,                          -- 'passkey_register'
+  session_data bytea NOT NULL,                         -- opaque go-webauthn SessionData
+  expires_at   timestamptz NOT NULL,                   -- short TTL set by the API clock
+  consumed_at  timestamptz,                            -- non-NULL once redeemed (single-use)
+  created_at   timestamptz NOT NULL DEFAULT now()
+);
+
+-- The finish path consumes the newest live row for a (user, purpose), so index it.
+CREATE INDEX webauthn_challenges_user_purpose_idx ON webauthn_challenges (user_id, purpose);