Files
thomasxm-amber/pkg/fixed_loader_x64.go
T
2020-11-26 22:48:05 +03:00

113 lines
5.9 KiB
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package amber
// FixedLoaderX64 contains the 64 bit PE loader for non-relocatable PE files
const FixedLoaderX64 = `
start:
pop rsi ; Get the address of image to rsi
call get_ip ; Push the current EIP to stack
get_ip:
sub [rsp],rsi ; Subtract the address of pre mapped PE image and get the image_size to R11
mov rbp,rsp ; Copy current stack address to rbp
and rbp,-0x1000 ; Create a new shadow stack address
mov eax,dword [rsi+0x3C] ; Get the offset of "PE" to eax
mov rbx,qword [rax+rsi+0x30] ; Get the image base address to rbx
mov r12d,dword [rax+rsi+0x28] ; Get the address of entry point to r12
push rax ; Allocate 8 bytes for lpflOldProtect
mov r9,rsp ; lpflOldProtect
mov r8d,dword 0x40 ; PAGE_EXECUTE_READWRITE
mov rdx,qword [rsp+8] ; dwSize
mov rcx,rbx ; lpAddress
mov r10d,0x80886EF1 ; crc32( "kernel32.dll", "VirtualProtect" )
xchg rsp,rbp ; Swap shadow stack
call api_call ; VirtualProtect( image_base, image_size, PAGE_EXECUTE_READWRITE, lpflOldProtect)
xchg rsp,rbp ; Swap shadow stack
xor rax,rax ; Zero EAX
xor r14,r14 ; Zero R14
xor r15,r15 ; Zero R15
mov eax,dword [rsi+0x3C] ; Offset to IMAGE_NT_HEADER ("PE")
mov eax,dword [rax+rsi+0x90] ; Import table RVA
add rax,rsi ; Import table memory address (first image import descriptor)
push rax ; Save import descriptor to stack
get_modules:
cmp dword [rax],0 ; Check if the import names table RVA is NULL
jz complete ; If yes building process is done
mov ecx,dword [rax+0x0C] ; Get RVA of dll name to eax
add rcx,rsi ; Get the dll name address
call LoadLibraryA ; Load the library
mov r13,rax ; Move the dll handle to R13
mov rax,[rsp] ; Move the address of current _IMPORT_DESCRIPTOR to eax
call get_procs ; Resolve all windows API function addresses
add dword [rsp],0x14 ; Move to the next import descriptor
mov rax,[rsp] ; Set the new import descriptor address to RAX
jmp get_modules
get_procs:
mov r14d,dword [rax+0x10] ; Save the current import descriptor IAT RVA to R14D
add r14,rsi ; Get the IAT memory address
mov rax,[rax] ; Set the import names table RVA to RAX
add rax,rsi ; Get the current import descriptor's import names table address
mov r15,rax ; Save &INT to R15
resolve:
cmp dword [rax],0 ; Check if end of the import names table
jz all_resolved ; If yes resolving stage is done
mov rax,[rax] ; Get the RVA of function hint to eax
btr rax,0x3F ; Check if the high order bit is set
jnc name_resolve ; If high order bit is not set resolve with INT entry
shl rax,2 ; Discard the high bit by shifting
shr rax,2 ; Shift back the original value
call GetProcAddress ; Get API address with hint
jmp insert_iat ; Insert the address of API to IAT
name_resolve:
add rax,rsi ; Set the address of function hint
add rax,2 ; Move to function name
call GetProcAddress ; Get the function address to eax
insert_iat:
mov [r14],rax ; Insert the function address to IAT
add r14,8 ; Increase the IAT index
add r15,8 ; Increase the import names table index
mov rax,r15 ; Set the address of import names table address to RAX
jmp resolve ; Loop
all_resolved:
mov qword [r14],0 ; Insert a NULL qword
ret ; <-
LoadLibraryA:
xchg rbp,rsp ; Swap shadow stack
mov r10d,0xE2E6A091 ; hash( "kernel32.dll", "LoadLibraryA" )
call api_call ; LoadLibraryA(RCX)
xchg rbp,rsp ; Swap shadow stack
ret ; <-
GetProcAddress:
xchg rbp,rsp ; Swap shadow stack
mov rcx,r13 ; Move the module handle to RCX as first parameter
mov rdx,rax ; Move the address of function name string to RDX as second parameter
mov r10d,0xA18B0B38 ; hash( "kernel32.dll", "GetProcAddress" )
call api_call ; GetProcAddress(RCX,RDX)
xchg rbp,rsp ; Swap shadow stack
ret ; <-
complete:
pop rax ; Clean out the stack
pop rax ; ...
pop rcx ; Pop the image_size to RCX
push rbx ; Push the new base adress to stack
add [rsp],r12 ; Add the address of entry value to new base address
memcpy:
mov al,[rsi] ; Move 1 byte of PE image to AL register
mov byte [rbx],al ; Move 1 byte of PE image to image base
mov byte [rsi],0 ; Overwrite copied byte (for less memory footprint)
inc rsi ; Increase PE image index
inc rbx ; Increase image base index
loop memcpy ; Loop until zero
jmp PE_start ; Wipe artifacts from memory and start PE
%s
PE_start:
mov rcx,wipe ; Get the number of bytes until wipe label
lea rax,[rip] ; Get RIP to RAX
nop ; Padding
wipe:
mov byte [rax],0 ; Wipe 1 byte at a time
dec rax ; Decraise RAX
loop wipe ; Loop until RCX = 0
%s
ret ; Return to AOE
`