GoldenByte#

Files#

We have one file GoldenByte: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=5365347daaf3af6f6681afe94cbab95355b3ad8c, for GNU/Linux 3.2.0, not stripped

Running the file gives us

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--- 'Golden Byte' Lottery ---
2
Ready to test your luck? Enter your lottery ticket number: > 123
3

4
Checking ticket number 123...
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Sorry, your ticket didn't win. Better luck next time!

Getting the flag#

Looking at the gdb assembly and some debugging

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   0x0000000000001289 <+133>:   movzx  eax,WORD PTR [rbp-0x4]
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   0x000000000000128d <+137>:   cmp    ax,0xfde9
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   0x0000000000001291 <+141>:   jne    0x12a9 <main+165>
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   0x0000000000001293 <+143>:   movzx  eax,WORD PTR [rbp-0x2]
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   0x0000000000001297 <+147>:   cmp    ax,0xbee0

We can see that its comparing our input to a specific value so all we need is to input that value

So our value needs to be 0xbee0fde9 which is 3202416105

We submit that to the server and get our flag

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--- 'Golden Byte' Lottery ---
2
Ready to test your luck? Enter your lottery ticket number: > 3202416105
3

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Checking ticket number -1092551191...
5
grodno{D4dy4_m4TV31_Pr019r4l_kV4rT1RY_V_K421n0_V3D_n3_2N4L_PWN}