Papa brought me a packed present! let's open it.
Download : http://pwnable.kr/bin/flag
This is reversing task. all you need is binary

Note: this solution is based on IDA pro.

We can see that flag is a 64-bit ELF binary.

But somehow, the analysis fails. We go through the hex and find a string:

As it is packed with UPX, we can just unpack the binary and open it again.

The main function is very simple; it just copies the flag with strcpy. Tracing the flag variable, we can find the content of it.

Easy using IDA, but I will soon update the post with an alternative solution using ollydbg, for a more technical approach.