baron-sso/devfront/src/lib/authConfig.ts

export interface DevFrontAuthRedirectUris {
  redirectUri: string;
  postLogoutRedirectUri: string;
  popupRedirectUri: string;
}

export const DEVFRONT_AUTH_CALLBACK_PATH = "/auth/callback";

export function resolveDevFrontPublicOrigin(
  configuredOrigin: string | undefined,
  browserOrigin: string,
) {
  const trimmed = configuredOrigin?.trim();
  if (!trimmed) {
    return browserOrigin;
  }

  try {
    return new URL(trimmed).origin;
  } catch {
    return browserOrigin;
  }
}

export function buildDevFrontAuthRedirectUris(
  publicOrigin: string,
): DevFrontAuthRedirectUris {
  return {
    redirectUri: `${publicOrigin}${DEVFRONT_AUTH_CALLBACK_PATH}`,
    postLogoutRedirectUri: publicOrigin,
    popupRedirectUri: `${publicOrigin}${DEVFRONT_AUTH_CALLBACK_PATH}`,
  };
}

export type BrowserPkceLoginCheck = {
  isSecureContext?: boolean;
  origin?: string;
  cryptoSubtleAvailable?: boolean;
};

const devTrustedPkceHosts = new Set([
  "localhost",
  "127.0.0.1",
  "::1",
  "host.docker.internal",
]);

function isPrivateIPv4(hostname: string) {
  const parts = hostname.split(".").map((part) => Number.parseInt(part, 10));
  if (
    parts.length !== 4 ||
    parts.some((part) => Number.isNaN(part) || part < 0 || part > 255)
  ) {
    return false;
  }

  const [first, second] = parts;
  return (
    first === 10 ||
    (first === 172 && second >= 16 && second <= 31) ||
    (first === 192 && second === 168)
  );
}

function isDevTrustedPkceOrigin(origin: string) {
  try {
    const hostname = new URL(origin).hostname;
    return devTrustedPkceHosts.has(hostname) || isPrivateIPv4(hostname);
  } catch {
    return false;
  }
}

export function canStartBrowserPkceLogin({
  isSecureContext = window.isSecureContext,
  origin = window.location.origin,
  cryptoSubtleAvailable = Boolean(window.crypto?.subtle),
}: BrowserPkceLoginCheck = {}) {
  if (!cryptoSubtleAvailable) {
    return false;
  }

  if (isSecureContext) {
    return true;
  }

  return isDevTrustedPkceOrigin(origin);
}