Firebase Auth利用したServerSideでのログイン

使用してるもの

• Next 15
• Auth.js v5
• Firebase Auth

問題点

Auth.jsをFirebase Authの情報を元にログインさせたいが、ServerSideでemailとpasswordを検証する術がわからない。

解決

https://cloud.google.com/identity-platform/docs/use-rest-api?hl=ja#section-sign-in-email-password

// Request Body Payload
export type SignInRequestPayload = {
  email: string; // The email the user is signing in with.
  password: string; // The password for the account.
  returnSecureToken: boolean; // Should always be true.
};

// Response Payload
export type SignInResponsePayload = {
  idToken: string; // A Firebase Auth ID token for the authenticated user.
  email: string; // The email for the authenticated user.
  refreshToken: string; // A Firebase Auth refresh token for the authenticated user.
  expiresIn: string; // The number of seconds in which the ID token expires.
  localId: string; // The uid of the authenticated user.
  registered: boolean; // Whether the email is for an existing account.
};

export const signInWithRestAPI = async (payload: SignInRequestPayload): Promise<SignInResponsePayload> => {
  const data = await fetch(`https://identitytoolkit.googleapis.com/v1/accounts:signInWithPassword?key=${process.env.FIREBASE_API_KEY}`, {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify(payload),
  }).then((res) => res.json());

  if (data.error) {
    throw new Error(data.error.message);
  }

  return data as SignInResponsePayload;
}

これでできた