MikroTik

Posted: **Wed Jul 13, 2022 2:55 am**

Hello. Perhaps somebody would find this useful some day. I googled around and did not find any ready solution, so here it is - a script to decode base64 back into original string. (I needed it to decode some data I "/fetch" from remote host)

If you know how to make it better (ie. get rid of that ugly "int2chr", please post your solution.

:global int2chr do={
    :local symbolsHex {"\00";"\01";"\02";"\03";"\04";"\05";"\06";"\07";"\08";"\09";"\0A";"\0B";"\0C";"\0D";"\0E";"\0F";"\10";"\11";"\12";"\13";"\14";"\15";"\16";"\17";"\18";"\19";"\1A";"\1B";"\1C";"\1D";"\1E";"\1F";"\20";"\21";"\22";"\23";"\24";"\25";"\26";"\27";"\28";"\29";"\2A";"\2B";"\2C";"\2D";"\2E";"\2F";"\30";"\31";"\32";"\33";"\34";"\35";"\36";"\37";"\38";"\39";"\3A";"\3B";"\3C";"\3D";"\3E";"\3F";"\40";"\41";"\42";"\43";"\44";"\45";"\46";"\47";"\48";"\49";"\4A";"\4B";"\4C";"\4D";"\4E";"\4F";"\50";"\51";"\52";"\53";"\54";"\55";"\56";"\57";"\58";"\59";"\5A";"\5B";"\5C";"\5D";"\5E";"\5F";"\60";"\61";"\62";"\63";"\64";"\65";"\66";"\67";"\68";"\69";"\6A";"\6B";"\6C";"\6D";"\6E";"\6F";"\70";"\71";"\72";"\73";"\74";"\75";"\76";"\77";"\78";"\79";"\7A";"\7B";"\7C";"\7D";"\7E";"\7F";"\80";"\81";"\82";"\83";"\84";"\85";"\86";"\87";"\88";"\89";"\8A";"\8B";"\8C";"\8D";"\8E";"\8F";"\90";"\91";"\92";"\93";"\94";"\95";"\96";"\97";"\98";"\99";"\9A";"\9B";"\9C";"\9D";"\9E";"\9F";"\A0";"\A1";"\A2";"\A3";"\A4";"\A5";"\A6";"\A7";"\A8";"\A9";"\AA";"\AB";"\AC";"\AD";"\AE";"\AF";"\B0";"\B1";"\B2";"\B3";"\B4";"\B5";"\B6";"\B7";"\B8";"\B9";"\BA";"\BB";"\BC";"\BD";"\BE";"\BF";"\C0";"\C1";"\C2";"\C3";"\C4";"\C5";"\C6";"\C7";"\C8";"\C9";"\CA";"\CB";"\CC";"\CD";"\CE";"\CF";"\D0";"\D1";"\D2";"\D3";"\D4";"\D5";"\D6";"\D7";"\D8";"\D9";"\DA";"\DB";"\DC";"\DD";"\DE";"\DF";"\E0";"\E1";"\E2";"\E3";"\E4";"\E5";"\E6";"\E7";"\E8";"\E9";"\EA";"\EB";"\EC";"\ED";"\EE";"\EF";"\F0";"\F1";"\F2";"\F3";"\F4";"\F5";"\F6";"\F7";"\F8";"\F9";"\FA";"\FB";"\FC";"\FD";"\FE";"\FF"};
    :return ($symbolsHex->[:tonum $1])
}

:global base64decode do={
    :global int2chr
    :local encoded $1;
    :local decoded ""
    :local b64 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"

    for pos from=0 to=([len $encoded]-1) step=4 do={
        :local part [:pick $encoded $pos ($pos+4)]

        :local n 0
        :local idx 0

        for step from=0 to=4 step=1 do={
            :local c [:pick $part $step ($step+1)]
            :set idx [:find $b64 $c 0]
            :set $n ($n + ($idx << (18-$step*6)))
        }

        for shift from=16 to=0 step=-8 do={
            :local asciicode (($n >> $shift) & 255)
            :set $decoded ($decoded . [$int2chr $asciicode])
        }
    }

    :return $decoded
}

{
    :local data2 "dGhpcyBpcyBzYW1wbGUgdGV4dCwgZW5jb2RlZCBpbnRvIGJhc2U2NCBmb3IgZnVuIGFuZCBwcm9maXQh"
    :put "encoded: $data2"

    :local decoded [$base64decode $data2]
    :put "decoded: $decoded"
}

MikroTik

Base64 decoding script

Base64 decoding script