Reverse Engineering for Beginners

(avery) #1

CHAPTER 78. DONGLES CHAPTER 78. DONGLES


seg030:00C7 68 D7 00 push 0D7h ; '+'
seg030:00CA EB 0B jmp short loc_35A37
seg030:00CC
seg030:00CC loc_35A2C: ; CODE XREF: sent_pro+84j
seg030:00CC 68 C3 00 push 0C3h
seg030:00CF 0E push cs
seg030:00D0 E8 61 FF call near ptr out_port
seg030:00D3 59 pop cx
seg030:00D4 68 C7 00 push 0C7h
seg030:00D7
seg030:00D7 loc_35A37: ; CODE XREF: sent_pro+89j
seg030:00D7 0E push cs
seg030:00D8 E8 59 FF call near ptr out_port
seg030:00DB 59 pop cx
seg030:00DC 68 D3 00 push 0D3h
seg030:00DF 0E push cs
seg030:00E0 E8 51 FF call near ptr out_port
seg030:00E3 59 pop cx
seg030:00E4 8B 46 FE mov ax, [bp+var_2]
seg030:00E7 D1 E0 shl ax, 1
seg030:00E9 89 46 FE mov [bp+var_2], ax
seg030:00EC 4E dec si
seg030:00ED 75 C3 jnz short loc_35A12
seg030:00EF
seg030:00EF loc_35A4F: ; CODE XREF: sent_pro+6Cj
seg030:00EF C4 5E 06 les bx, [bp+arg_0]
seg030:00F2 FF 46 06 inc word ptr [bp+arg_0]
seg030:00F5 26 8A 07 mov al, es:[bx]
seg030:00F8 98 cbw
seg030:00F9 89 46 FE mov [bp+var_2], ax
seg030:00FC 0B C0 or ax, ax
seg030:00FE 75 AF jnz short loc_35A0F
seg030:0100 68 FF 00 push 0FFh
seg030:0103 0E push cs
seg030:0104 E8 2D FF call near ptr out_port
seg030:0107 59 pop cx
seg030:0108 8B 16 82 E7 mov dx, _in_port_1 ; 0x37A
seg030:010C EC in al, dx
seg030:010D 8A C8 mov cl, al
seg030:010F 80 E1 5F and cl, 5Fh
seg030:0112 8A C1 mov al, cl
seg030:0114 EE out dx, al
seg030:0115 EC in al, dx
seg030:0116 8A C8 mov cl, al
seg030:0118 F6 C1 20 test cl, 20h
seg030:011B 74 08 jz short loc_35A85
seg030:011D 8A 5E FD mov bl, [bp+var_3]
seg030:0120 80 E3 DF and bl, 0DFh
seg030:0123 EB 03 jmp short loc_35A88
seg030:0125
seg030:0125 loc_35A85: ; CODE XREF: sent_pro+DAj
seg030:0125 8A 5E FD mov bl, [bp+var_3]
seg030:0128
seg030:0128 loc_35A88: ; CODE XREF: sent_pro+E2j
seg030:0128 F6 C1 80 test cl, 80h
seg030:012B 74 03 jz short loc_35A90
seg030:012D 80 E3 7F and bl, 7Fh
seg030:0130
seg030:0130 loc_35A90: ; CODE XREF: sent_pro+EAj
seg030:0130 8B 16 82 E7 mov dx, _in_port_1 ; 0x37A
seg030:0134 8A C3 mov al, bl
seg030:0136 EE out dx, al
seg030:0137 8B C7 mov ax, di
seg030:0139 5F pop di
seg030:013A 5E pop si
seg030:013B C9 leave
seg030:013C CB retf
seg030:013C sent_pro endp


This is again a Sentinel Pro “hashing” dongle as in the previous example. It is noticeably because text strings are passed

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