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130 lines
2.3 KiB
Markdown
130 lines
2.3 KiB
Markdown
`Taken from my notebook, verbatim`
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### Page 5
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```
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LAGOS
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45a0: 0b41 -> 3041 "ret"
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WE CAN add #4130, sp
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~ MOVE THE STACK ~
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0: input [0x1bf]=
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1: ret -> 4444 (sp+0x60)
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2: Move stack to 2400+1c0
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3: Ret -> arbitrary address (i.e. 2400+1c2)
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4: Execute arbitrary code
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```
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### Page 1
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```
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Lagos Alphanumerics Only
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`0x200 B -> #2400`
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Password valid range: 8-16 c
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Valid chars:
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[0-9] [A-Z] [a-z]
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30-39 41-5a 61-7a
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We have enough chars
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to overwrite current
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function
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1b5 bytes before hitting
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current instruction
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3041 = ret
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45a0 = 0b41
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at index 1b5
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Control of return addr
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-> we can ret to string buffer
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bypassing sanitizer!
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ret to 2400+1bb
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25b5
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run code from there!
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ret at index 0x11
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... we need a JMP to get there.
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... all our jumps are positive
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```
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### Page 2
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```
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D p
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4470 looks like a good place
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D 0
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for code, or 4430
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5a37: jge $-14a ?
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Arithmetic instructions
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Form addresses with sub?
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25 b6 bb25
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^lsb
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55-30 7a-30(ish)
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547a + 3030 =
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5630 - 307a = 25bb!
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V 0 0 z
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We can load from our string:
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pop r4 = 3441
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"4 A "
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-> can be any reg from
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0-9: 3r41
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add.b = 7x5y
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3451 = pop & add to r4
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3441 3451
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pop r4 add r4
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```
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### Page 3
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```
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Instructions in range
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30: jn
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34: jge
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38: jl
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3c: jmp
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4#: mov
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5#: add
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6#: addc
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7#: subc
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Feasible addressing modes
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10 @Rn Register indirect
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11 @Rn+ RI w/ post-inc
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Subtract the stack from pc?
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3071 subc @sp+, pc
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"Large relative jump"
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Alignment in 2400 buffer
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is not same as in PC
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```
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### Page 4
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```
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What is an alphanumeric character?
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[0-9] [A-Z] [a-z]
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30-39 41-5a 61-7a
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Buffers: 43ed: stack buffer
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2400: load buffer
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43ed + 0x57: 4444
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45a0: last byte copied (1b3 bytes)
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&[43ed + 1b3] = 0x30, '0'
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43ed + 1c0 = payload
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Correction: sp at 43ec before
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we gain exec
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ret will tak sp to 43ee
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... we need to create a fake stack
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somewhere over in the controllable
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zone
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The loop only continues if the
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FOLLOWING BYTE is valid.
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```
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