feat: support OIDC login.

backend/internal/handler/auth_oidc_oauth_test.go

@@ -0,0 +1,106 @@
+package handler
+
+import (
+	"context"
+	"crypto/rand"
+	"crypto/rsa"
+	"encoding/base64"
+	"encoding/json"
+	"math/big"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"github.com/Wei-Shaw/sub2api/internal/config"
+	"github.com/golang-jwt/jwt/v5"
+	"github.com/stretchr/testify/require"
+)
+
+func TestOIDCSyntheticEmailStableAndDistinct(t *testing.T) {
+	k1 := oidcIdentityKey("https://issuer.example.com", "subject-a")
+	k2 := oidcIdentityKey("https://issuer.example.com", "subject-b")
+
+	e1 := oidcSyntheticEmailFromIdentityKey(k1)
+	e1Again := oidcSyntheticEmailFromIdentityKey(k1)
+	e2 := oidcSyntheticEmailFromIdentityKey(k2)
+
+	require.Equal(t, e1, e1Again)
+	require.NotEqual(t, e1, e2)
+	require.Contains(t, e1, "@oidc-connect.invalid")
+}
+
+func TestBuildOIDCAuthorizeURLIncludesNonceAndPKCE(t *testing.T) {
+	cfg := config.OIDCConnectConfig{
+		AuthorizeURL: "https://issuer.example.com/auth",
+		ClientID:     "cid",
+		Scopes:       "openid email profile",
+		UsePKCE:      true,
+	}
+
+	u, err := buildOIDCAuthorizeURL(cfg, "state123", "nonce123", "challenge123", "https://app.example.com/callback")
+	require.NoError(t, err)
+	require.Contains(t, u, "nonce=nonce123")
+	require.Contains(t, u, "code_challenge=challenge123")
+	require.Contains(t, u, "code_challenge_method=S256")
+	require.Contains(t, u, "scope=openid+email+profile")
+}
+
+func TestOIDCParseAndValidateIDToken(t *testing.T) {
+	priv, err := rsa.GenerateKey(rand.Reader, 2048)
+	require.NoError(t, err)
+
+	kid := "kid-1"
+	jwks := oidcJWKSet{Keys: []oidcJWK{buildRSAJWK(kid, &priv.PublicKey)}}
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		require.NoError(t, json.NewEncoder(w).Encode(jwks))
+	}))
+	defer srv.Close()
+
+	now := time.Now()
+	claims := oidcIDTokenClaims{
+		Nonce: "nonce-ok",
+		Azp:   "client-1",
+		RegisteredClaims: jwt.RegisteredClaims{
+			Issuer:    "https://issuer.example.com",
+			Subject:   "subject-1",
+			Audience:  jwt.ClaimStrings{"client-1", "another-aud"},
+			IssuedAt:  jwt.NewNumericDate(now),
+			NotBefore: jwt.NewNumericDate(now.Add(-30 * time.Second)),
+			ExpiresAt: jwt.NewNumericDate(now.Add(5 * time.Minute)),
+		},
+	}
+	tok := jwt.NewWithClaims(jwt.SigningMethodRS256, claims)
+	tok.Header["kid"] = kid
+	signed, err := tok.SignedString(priv)
+	require.NoError(t, err)
+
+	cfg := config.OIDCConnectConfig{
+		ClientID:           "client-1",
+		IssuerURL:          "https://issuer.example.com",
+		JWKSURL:            srv.URL,
+		AllowedSigningAlgs: "RS256",
+		ClockSkewSeconds:   120,
+	}
+
+	parsed, err := oidcParseAndValidateIDToken(context.Background(), cfg, signed, "nonce-ok")
+	require.NoError(t, err)
+	require.Equal(t, "subject-1", parsed.Subject)
+	require.Equal(t, "https://issuer.example.com", parsed.Issuer)
+
+	_, err = oidcParseAndValidateIDToken(context.Background(), cfg, signed, "bad-nonce")
+	require.Error(t, err)
+}
+
+func buildRSAJWK(kid string, pub *rsa.PublicKey) oidcJWK {
+	n := base64.RawURLEncoding.EncodeToString(pub.N.Bytes())
+	e := base64.RawURLEncoding.EncodeToString(big.NewInt(int64(pub.E)).Bytes())
+	return oidcJWK{
+		Kty: "RSA",
+		Kid: kid,
+		Use: "sig",
+		Alg: "RS256",
+		N:   n,
+		E:   e,
+	}
+}