pharext\Archive::readSignature PHP Method

    private function readSignature()
    {
        fseek($this->fd, -8, SEEK_END);
        $sig = $this->readFormat("Vflags/Z4magic", $this->fd, 8);
        $end = ftell($this->fd);
        if ($sig["magic"] !== "GBMB") {
            throw new Exception("Invalid signature magic value '{$sig["magic"]}");
        }
        switch ($sig["flags"]) {
            case self::SIG_OPENSSL:
                fseek($this->fd, -12, SEEK_END);
                if ($hash = $this->readSingleFormat("V", $this->fd, 4)) {
                    $offset = 4 + $hash;
                    fseek($this->fd, -$offset, SEEK_CUR);
                    $hash = $this->readVerified($this->fd, $hash);
                    fseek($this->fd, 0, SEEK_SET);
                    $valid = openssl_verify($this->readVerified($this->fd, $end - $offset - 8), $hash, @file_get_contents($this->file . ".pubkey")) === 1;
                }
                break;
            case self::SIG_MD5:
            case self::SIG_SHA1:
            case self::SIG_SHA256:
            case self::SIG_SHA512:
                $offset = 8 + self::$siglen[$sig["flags"]];
                fseek($this->fd, -$offset, SEEK_END);
                $hash = $this->readVerified($this->fd, self::$siglen[$sig["flags"]]);
                $algo = hash_init(self::$sigalg[$sig["flags"]]);
                fseek($this->fd, 0, SEEK_SET);
                hash_update_stream($algo, $this->fd, $end - $offset);
                $valid = hash_final($algo, true) === $hash;
                break;
            default:
                throw new Exception("Invalid signature type '{$sig["flags"]}");
        }
        return $sig + compact("hash", "valid");
    }