unPad16 - remove padding
| 44 | |
| 45 | // unPad16 - remove padding |
| 46 | int unPad16(BYTE *padded, int len) { |
| 47 | int oldLen = len; |
| 48 | if (oldLen % 16 != 0) { |
| 49 | return -1; |
| 50 | } |
| 51 | // The last byte is always a padding byte |
| 52 | BYTE padByte = padded[oldLen - 1]; |
| 53 | // The padding byte's value is the padding length |
| 54 | int padLen = (int)(padByte); |
| 55 | // Padding must be at least 1 byte |
| 56 | if (padLen <= 0) { |
| 57 | return -1; |
| 58 | } |
| 59 | // Larger paddings make no sense |
| 60 | if (padLen > 16) { |
| 61 | return -1; |
| 62 | } |
| 63 | // All padding bytes must be identical |
| 64 | for (int i = oldLen - padLen; i < oldLen; i++) { |
| 65 | if (padded[i] != padByte) { |
| 66 | return -1; |
| 67 | } |
| 68 | } |
| 69 | int newLen = oldLen - padLen; |
| 70 | // Padding an empty string makes no sense |
| 71 | if (newLen == 0) { |
| 72 | return -1; |
| 73 | } |
| 74 | return newLen; |
| 75 | } |