Recover the executable memory to it's original state

injector/src/game_p.asm

@@ -1,5 +1,50 @@
 BITS 64
 
+; Macro definitions
+
+; read dst, pSrc, size
+%macro read 3
+
+    mov %1, [%2]
+    add %2, %3
+
+%endmacro
+
+; copy pDst, pSrc, temp, tempSize
+%macro copy 4
+
+    mov %3, [%2]
+    mov [%1], %3
+    add %1, %4
+    add %2, %4
+
+%endmacro
+
+; unprotect addr, size, fn
+%macro unprotect 3
+
+    mov rcx, %1
+    mov rdx, %2
+    mov r8, 40h  ; PAGE_EXECUTE_READWRITE
+    lea r9, [rel oldProtect]
+
+    call %3
+
+%endmacro
+
+; reprotect addr, size, fn
+%macro reprotect 3
+
+    mov rcx, %1
+    mov rdx, %2
+    lea r9, [rel oldProtect]
+    mov r8d, [r9]
+
+    call %3
+
+%endmacro
+
+
 main: ; Replacement entry point
     push rsi
     push rdi
@@ -16,6 +61,14 @@ main: ; Replacement entry point
     mov rdi, rax   ; *GetProcAddress
 
 
+    mov rcx, rsi          ; kernel32.dll
+    lea rdx, [rel s_VirtualProtect]
+    call rdi              ; rax = *VirtualProtect
+    
+    mov rcx, rax
+    call RecoverExecutable
+
+
     mov rcx, rsi          ; kernel32.dll
     lea rdx, [rel s_LoadLibraryW]
     call rdi              ; rax = *LoadLibraryW
@@ -63,10 +116,65 @@ main: ; Replacement entry point
     ret
 
 
+RecoverExecutable:  ; expects *VirtualProtect in rcx
+    push rbx
+    push r12
+    push r13
+    push r14
+    sub rsp, 8
+
+    mov r13, rcx
+
+    ; Find the recovery data structure
+    lea rbx, [rel dllPath]
+
+.search:
+    read ax, rbx, 2
+    test ax, ax
+    jnz .search
+
+    ; Recover entry point bytes (6 + 8 = 14 total)
+    read r12, rbx, 8  ; Address
+    mov r14, r12
+
+    unprotect r14, 14, r13
+    copy r12, rbx, rax, 8
+    copy r12, rbx, eax, 4
+    copy r12, rbx, ax,  2
+    reprotect r14, 14, r13
+
+    ; Recover import descriptor bytes (20 total)
+    read r12, rbx, 8
+    mov r14, r12
+
+    unprotect r14, 20, r13
+    copy r12, rbx, rax, 8
+    copy r12, rbx, rax, 8
+    copy r12, rbx, eax, 4
+    reprotect r14, 20, r13
+
+    ; Recover import data directory entry size bytes (4 total)
+    read r12, rbx, 8
+    mov r14, r12
+
+    unprotect r14, 4, r13
+    copy r12, rbx, eax, 4
+    reprotect r14, 4, r13
+
+    add rsp, 8
+    pop r14
+    pop r13
+    pop r12
+    pop rbx
+    ret
+
+
 %include "gpa.asm"
 
+oldProtect: dd 0
 
 ; Strings
+s_VirtualProtect:    db "VirtualProtect", 0
 s_LoadLibraryW:      db "LoadLibraryW", 0
 s_GetModuleHandleA:  db "GetModuleHandleA", 0
 s_GetCommandLineW:   db "GetCommandLineW", 0