✅Puzzle 2

CODESIZE, SUB

Puzzle

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# Puzzle 2 #
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00      34      CALLVALUE
01      38      CODESIZE
02      03      SUB
03      56      JUMP
04      FD      REVERT
05      FD      REVERT
06      5B      JUMPDEST
07      00      STOP
08      FD      REVERT
09      FD      REVERT

? Enter the value to send: (0) 

Solution

CALLVALUE pushes msg.value onto the stack. CODESIZE pushes the size of this opcode sequence (which is 10) onto the stack. SUB pops two elements from the stack, subtracts them, and pushes the result back to the stack. At this moment the stack contains only one element 10-msg.value. JUMP will jump to 10-msg.value.

The objective is to jump to address 0x06, so we want 10-msg.value = 0x06, therefore the correct input is 4.