Incorretc result for message endingwith 0.

[jbadura]

Server returns 'All good!' when message ends with byte 0.

cbc.zig, from line 73:

// Check padding
// Return length of message if ok, otherwise 0.
const pad_length: u8 = dst[i - 1];

if (pad_length == 0) {
    return 0;
}

if (pad_length > block_length) {
    return 0;
}
var j: usize = 0;
while (j < pad_length) : (j += 1) {
    if (dst[i - j - 1] != pad_length) {
        return 0;
    }
}
return i - pad_length;

I think you should add:

if (pad_length == 0) {
    return 0;
}