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use std::collections::BTreeMap;
use anyhow::Result;
use log::debug;
use crate::{
arch::Arch,
emu::{mmu::MMU, plat, Emulator},
loader::pe::PE,
VA,
};
use super::WindowsEmulator;
pub struct Win32Emulator {
pub inner: Emulator,
imports: BTreeMap<VA, String>,
}
impl Default for Win32Emulator {
fn default() -> Self {
Win32Emulator {
inner: Emulator::with_arch(Arch::X32),
imports: Default::default(),
}
}
}
impl WindowsEmulator for Win32Emulator {
fn load_pe(&mut self, pe: &PE) -> Result<()> {
debug!("emu: plat: win32: load pe");
self.inner.load_module(&pe.module)?;
let imports = plat::win::link_imports(&mut self.inner, pe)?;
self.imports.extend(imports);
Ok(())
}
fn mem(&mut self) -> &mut MMU {
&mut self.inner.mem
}
fn set_pc(&mut self, addr: VA) {
self.inner.reg.set_eip(addr as u32);
}
fn pc(&self) -> VA {
self.inner.reg.eip() as VA
}
fn set_sp(&mut self, addr: VA) {
self.inner.reg.set_esp(addr as u32);
}
fn sp(&self) -> VA {
self.inner.reg.esp() as VA
}
/// note: truncates `value` to u32.
///
/// Errors:
/// - WriteError::AddressNotMapped when stack is not mapped.
/// - WriteError::AccessViolation when stack is not writable.
fn push(&mut self, value: u64) -> Result<()> {
let old_sp = self.sp();
let new_sp = old_sp - 4;
// write to mem first, since it could fail.
self.mem().write_u32(new_sp, value as u32)?;
self.set_sp(new_sp);
Ok(())
}
/// note: returns u32 value.
///
/// Errors:
/// - ReadError::AddressNotMapped when stack is not mapped.
/// - ReadError::AccessViolation when stack is not readable.
fn pop(&mut self) -> Result<u64> {
let old_sp = self.sp();
let new_sp = old_sp + 4;
// write to mem first, since it could fail.
let value = self.mem().read_u32(old_sp)? as u64;
self.set_sp(new_sp);
Ok(value)
}
fn set_bp(&mut self, addr: VA) {
self.inner.reg.set_ebp(addr as u32);
}
fn bp(&self) -> VA {
self.inner.reg.esp() as VA
}
fn set_fsbase(&mut self, addr: VA) {
self.inner.set_fsbase(addr);
}
// TODO: sketching this out
fn resolve_address(&self, addr: VA) -> Option<String> {
self.imports.get(&addr).cloned()
}
}
impl Win32Emulator {
pub fn handle_api(&mut self) -> Result<()> {
use super::api::CallingConvention;
if let Some(symbol) = self.resolve_address(self.pc()) {
if let Some(api) = super::api::API.get(&symbol) {
let ra = self.pop()?;
self.set_pc(ra);
if let CallingConvention::Stdcall = api.calling_convention {
for _ in 0..api.arguments.len() {
let _ = self.pop()?;
}
}
Ok(())
} else {
// we dont know anything about the API
// its probably stdcall, but we dont know how many arguments.
// TODO
unimplemented!("unknown API");
}
} else {
// we don't know what API this is.
// TODO
unimplemented!("unresolved API");
}
}
}
#[cfg(test)]
mod tests {
use crate::{
emu::{plat::win::win32::*, *},
rsrc::*,
};
use anyhow::Result;
/// Errors:
/// - FetchError::InvalidInstruction for instructions that cannot be
/// decoded.
/// - FetchError::AddressNotMapped when the instruction address is not
/// mapped.
/// - FetchError::AccessViolation when the instruction address is not
/// executable.
/// - WriteError::AddressNotMapped when a memory address is not mapped.
/// - WriteError::AccessViolation when a memory address is not executable.
/// - ReadError::AddressNotMapped when a memory address is not mapped.
/// - ReadError::AccessViolation when a memory address is not readable.
///
/// TODO: this routine should not be part of the base emulator.
/// there are too many customizations to handle, like how to deal with
/// imports, styles of breakpoints, etc.
/// so, provide documentation/examples of `step` routines and remove this.
fn step(emu: &mut Win32Emulator) -> Result<()> {
let insn = emu.inner.fetch()?;
emu.inner.execute(&insn)?;
// example: https://github.com/williballenthin/viv-utils/blob/master/viv_utils/emulator_drivers.py
Ok(())
}
#[test]
fn nop() -> Result<()> {
//init_logging();
let pe = crate::loader::pe::PE::from_bytes(&get_buf(Rsrc::NOP))?;
let mut emu: Win32Emulator = Default::default();
emu.load_pe(&pe)?;
let opt = pe.header.optional_header.unwrap();
let ep = opt.windows_fields.image_base + opt.standard_fields.address_of_entry_point;
emu.set_pc(ep);
emu.mem().mmap(0x5000, 0x2000, Permissions::RW)?;
emu.set_sp(0x6000);
emu.set_bp(0x6000);
emu.mem().mmap(0x7000, 0x1000, Permissions::RW)?;
emu.set_fsbase(0x7000);
// .text:00401081 push 18h
// .text:00401083 push offset stru_406160
// .text:00401088 call __SEH_prolog
assert_eq!(emu.pc(), 0x401081);
step(&mut emu)?; // push
step(&mut emu)?; // push
step(&mut emu)?; // call
// .text:004027A0 __SEH_prolog proc near
// .text:004027A0 push offset __except_handler3
// .text:004027A5 mov eax, large fs:0
// .text:004027AB push eax
// .text:004027AC mov eax, [esp+8+arg_4]
// .text:004027B0 mov [esp+8+arg_4], ebp
// .text:004027B4 lea ebp, [esp+8+arg_4]
// .text:004027B8 sub esp, eax
assert_eq!(emu.pc(), 0x4027A0);
step(&mut emu)?; // push
step(&mut emu)?; // mov
step(&mut emu)?; // push
step(&mut emu)?; // mov
step(&mut emu)?; // mov
step(&mut emu)?; // lea
step(&mut emu)?; // sub
while emu.pc() != 0x4027DA {
step(&mut emu)?;
}
// .text:004027DA retn
step(&mut emu)?; // retn
assert_eq!(emu.pc(), 0x40108D);
// .text:0040108D mov edi, 94h ; '”'
// .text:00401092 mov eax, edi
// .text:00401094 call __alloca_probe
step(&mut emu)?; // mov
step(&mut emu)?; // mov
step(&mut emu)?; // call
assert_eq!(emu.pc(), 0x402900);
// .text:00402900 cmp eax, 1000h
// .text:00402905 jnb short probesetup
step(&mut emu)?; // cmp
step(&mut emu)?; // jnb
assert_eq!(emu.pc(), 0x402907);
// .text:00402907 neg eax
// .text:00402909 add eax, esp
// .text:0040290B add eax, 4
// .text:0040290E test [eax], eax
// .text:00402910 xchg eax, esp
// .text:00402911 mov eax, [eax]
// .text:00402913 push eax
// .text:00402914 retn
step(&mut emu)?; // neg
step(&mut emu)?; // add
step(&mut emu)?; // add
step(&mut emu)?; // test
step(&mut emu)?; // xchg
step(&mut emu)?; // mov
step(&mut emu)?; // push
step(&mut emu)?; // ret
assert_eq!(emu.pc(), 0x401099);
// .text:00401099 mov [ebp+ms_exc.old_esp], esp
// .text:0040109C mov esi, esp
// .text:0040109E mov [esi], edi
// .text:004010A0 push esi ; lpVersionInformation
step(&mut emu)?; // mov
step(&mut emu)?; // mov
step(&mut emu)?; // mov
step(&mut emu)?; // push
// handling imports:
//
// next is call to import GetVersionExA.
// .text:004010A1 call ds:GetVersionExA
assert_eq!(emu.pc(), 0x4010A1);
step(&mut emu)?; // call ds:[0x406008]
// we've mapped the IAT entry to point to the OFT.
//
// FT OFT
// 0x406008 -> 0x406e88 (hint: 0x01DF, name: GetVersionExA)
assert_eq!(emu.pc(), 0x406e88);
// but this isn't a code segment,
// so if we try to execute it, it will fail with a FetchError
let e = step(&mut emu).unwrap_err(); // GetVersionExA impl
// demonstrate how to recover the called imported API.
if let Some(FetchError::AccessViolation { va, .. }) = e.downcast_ref::<FetchError>() {
assert_eq!(emu.resolve_address(*va).unwrap(), "kernel32.dll!GetVersionExA");
}
emu.handle_api()?;
assert_eq!(emu.pc(), 0x4010A7);
Ok(())
}
}