Hub: accounts, IMVU linking by tagline, proxy sign-in, presence, console

People sign up on the website and link IMVU accounts by putting a code in the account's tagline, which the
hub reads from IMVU's public API (the most recent proof wins; link caps per person). IMVU's age verification
or Access Pass make an account adult. T5DE's proxy signs in with a device code and keeps a WebSocket open,
reporting the IMVU account in use and the community products it wears; /online shows those who opted in.
Moderators get a console: who's online, people, link caps, bans, roles, and the audit log. Tests run the
website and API against an embedded Postgres and a fake IMVU API.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

internal/token/token.go

@@ -0,0 +1,117 @@
+// Package token issues and checks the hub's access tokens: JWTs signed with Ed25519 ("EdDSA"), short-lived. The
+// public keys are published (JWKS), so catalogs can check tokens without asking the hub.
+package token
+
+import (
+	"crypto/ed25519"
+	"crypto/rand"
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+)
+
+// Claims are what a token says.
+type Claims struct {
+	Issuer   string `json:"iss"`
+	Subject  string `json:"sub"` // "person:<id>" for the hub's own API
+	Audience string `json:"aud"`
+	IssuedAt int64  `json:"iat"`
+	Expires  int64  `json:"exp"`
+	Scope    string `json:"scope,omitempty"`
+}
+
+// Keys signs and checks tokens.
+type Keys struct {
+	id      string
+	private ed25519.PrivateKey
+	issuer  string
+}
+
+// LoadOrCreate reads the signing key from path, making one if there's none.
+func LoadOrCreate(path, issuer string) (*Keys, error) {
+	seed, err := os.ReadFile(path)
+	if errors.Is(err, os.ErrNotExist) {
+		seed = make([]byte, ed25519.SeedSize)
+		if _, err := rand.Read(seed); err != nil {
+			return nil, err
+		}
+		if err := os.MkdirAll(filepath.Dir(path), 0o700); err != nil {
+			return nil, err
+		}
+		if err := os.WriteFile(path, seed, 0o600); err != nil {
+			return nil, err
+		}
+	} else if err != nil {
+		return nil, err
+	}
+	if len(seed) != ed25519.SeedSize {
+		return nil, fmt.Errorf("%s: not an Ed25519 seed", path)
+	}
+	key := ed25519.NewKeyFromSeed(seed)
+	pub := key.Public().(ed25519.PublicKey)
+	return &Keys{id: b64(pub[:8]), private: key, issuer: issuer}, nil
+}
+
+func b64(b []byte) string { return base64.RawURLEncoding.EncodeToString(b) }
+
+// Issue signs a token for subject and audience, valid for ttl.
+func (k *Keys) Issue(subject, audience, scope string, ttl time.Duration) (string, error) {
+	now := time.Now()
+	header, _ := json.Marshal(map[string]string{"alg": "EdDSA", "typ": "JWT", "kid": k.id})
+	claims, _ := json.Marshal(Claims{Issuer: k.issuer, Subject: subject, Audience: audience, IssuedAt: now.Unix(),
+		Expires: now.Add(ttl).Unix(), Scope: scope})
+	signing := b64(header) + "." + b64(claims)
+	return signing + "." + b64(ed25519.Sign(k.private, []byte(signing))), nil
+}
+
+// ErrInvalid means a token is malformed, forged, for someone else, or expired.
+var ErrInvalid = errors.New("invalid token")
+
+// Check verifies a token for audience and returns its claims.
+func (k *Keys) Check(token, audience string) (*Claims, error) {
+	parts := strings.Split(token, ".")
+	if len(parts) != 3 {
+		return nil, ErrInvalid
+	}
+	headerJSON, err1 := base64.RawURLEncoding.DecodeString(parts[0])
+	claimsJSON, err2 := base64.RawURLEncoding.DecodeString(parts[1])
+	sig, err3 := base64.RawURLEncoding.DecodeString(parts[2])
+	if err1 != nil || err2 != nil || err3 != nil {
+		return nil, ErrInvalid
+	}
+	var header struct{ Alg, Kid string }
+	if json.Unmarshal(headerJSON, &header) != nil || header.Alg != "EdDSA" || header.Kid != k.id {
+		return nil, ErrInvalid
+	}
+	if !ed25519.Verify(k.private.Public().(ed25519.PublicKey), []byte(parts[0]+"."+parts[1]), sig) {
+		return nil, ErrInvalid
+	}
+	var c Claims
+	if json.Unmarshal(claimsJSON, &c) != nil || c.Issuer != k.issuer || c.Audience != audience || time.Now().Unix() >= c.Expires {
+		return nil, ErrInvalid
+	}
+	return &c, nil
+}
+
+// JWKS is the public key set, as JSON (RFC 8037 OKP keys).
+func (k *Keys) JWKS() []byte {
+	pub := k.private.Public().(ed25519.PublicKey)
+	b, _ := json.Marshal(map[string]any{"keys": []map[string]string{{
+		"kty": "OKP", "crv": "Ed25519", "alg": "EdDSA", "use": "sig", "kid": k.id, "x": b64(pub),
+	}}})
+	return b
+}
+
+// Random is a random URL-safe string of n bytes' entropy, for session and refresh tokens.
+func Random(n int) string {
+	b := make([]byte, n)
+	if _, err := rand.Read(b); err != nil {
+		panic(err)
+	}
+	return b64(b)
+}