Function extractMappedIPv4

src/utils/hooks/ssrfGuard.ts:187–204

* Extract the embedded IPv4 address from an IPv4-mapped IPv6 address * (0:0:0:0:0:ffff:X:Y) in any valid representation — compressed, expanded, * hex groups, or trailing dotted-decimal. Returns null if the address is * not an IPv4-mapped IPv6 address.

(addr: string)

 * not an IPv4-mapped IPv6 address.
 */
function extractMappedIPv4(addr: string): string | null {
  const g = expandIPv6Groups(addr)
  if (!g) return null
  // IPv4-mapped: first 80 bits zero, next 16 bits ffff, last 32 bits = IPv4
  if (
    g[0] === 0 &&
    g[1] === 0 &&
    g[2] === 0 &&
    g[3] === 0 &&
    g[4] === 0 &&
    g[5] === 0xffff
  ) {
    const hi = g[6]!
    const lo = g[7]!
    return `${hi >> 8}.${hi & 0xff}.${lo >> 8}.${lo & 0xff}`
  }
  return null
}

/**
 * A dns.lookup-compatible function that resolves a hostname and rejects