patch_analyzer.cpp

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#include "patch_analyzer.h"
//---
using namespace pesieve;
 
template <typename DELTA_T>
ULONGLONG pesieve::PatchAnalyzer::getJmpDestAddr(ULONGLONG currVA, int instrLen, DELTA_T lVal)
{
    int delta = instrLen + int(lVal);
    ULONGLONG addr = currVA + delta;
    return addr;
}
 
size_t pesieve::PatchAnalyzer::parseShortJmp(PatchList::Patch &patch, PBYTE patch_ptr, ULONGLONG patch_va)
{
    const size_t instr_size = 2;
    if (!peconv::validate_ptr(this->patchedCode, this->codeSize, patch_ptr, instr_size)) {
        return 0;
    }
    BYTE *lval = (BYTE*)((ULONGLONG)patch_ptr + 1);
    ULONGLONG addr = getJmpDestAddr<BYTE>(patch_va, instr_size, (*lval));
 
    patch.setHookTarget(addr);
    return instr_size;
}
 
size_t pesieve::PatchAnalyzer::parseJmp(PatchList::Patch &patch, PBYTE patch_ptr, ULONGLONG patch_va)
{
    const size_t instr_size = 5;
    if (!peconv::validate_ptr(this->patchedCode, this->codeSize, patch_ptr, instr_size)) {
        return 0;
    }
    DWORD *lval = (DWORD*)((ULONGLONG) patch_ptr + 1);
    ULONGLONG addr = getJmpDestAddr<DWORD>(patch_va, instr_size, (*lval));
 
    patch.setHookTarget(addr);
    return instr_size;
}
 
size_t pesieve::PatchAnalyzer::parseJmpViaAddr(PatchList::Patch &patch, PBYTE patch_ptr, ULONGLONG patch_va)
{
    const size_t instr_size = 6;
    ULONGLONG addr = NULL;
 
    DWORD *lval = (DWORD*)((ULONGLONG)patch_ptr + 2);
    if (!isModule64bit) { //32bit
        patch.setHookTarget(*lval, false);
    }
    else { //64bit
        ULONGLONG addr = getJmpDestAddr<DWORD>(patch_va, instr_size, (*lval));
        patch.setHookTarget(addr, false);
    }
    return instr_size;
}
 
size_t pesieve::PatchAnalyzer::parseMovJmp(PatchList::Patch &patch, PBYTE patch_ptr, bool is_long)
{
    size_t mov_instr_len = is_long ? 9 : 5;
    if (!peconv::validate_ptr(this->patchedCode, this->codeSize, patch_ptr, mov_instr_len + 2)) {
        return 0;
    }
 
    PBYTE jmp_ptr = patch_ptr + mov_instr_len; // next instruction
    if (is64Modifier(*patch_ptr)) {
        patch_ptr++;
        jmp_ptr++;
        mov_instr_len++; // add length of modifier
    }
    
    DWORD reg_id0 = patch_ptr[0] - 0xB8;
 
    // before call/jmp there can be also the modifier...
    if (is64Modifier(*jmp_ptr)) {
        jmp_ptr++;
        mov_instr_len++; // add length of modifier
    }
    if (!peconv::validate_ptr(this->patchedCode, this->codeSize, jmp_ptr, 2)) {
        return 0;
    }
    DWORD reg_id1 = 0;
    if (jmp_ptr[0] == 0xFF && jmp_ptr[1] >= 0xE0 && jmp_ptr[1] <= 0xEF ) { // jmp reg
        //jmp reg
        reg_id1 = jmp_ptr[1] - 0xE0;
    } else if (jmp_ptr[0] == 0xFF && jmp_ptr[1] >= 0xD0 && jmp_ptr[1] <= 0xDF ) { // call reg
        //jmp reg
        reg_id1 = jmp_ptr[1] - 0xD0;
    } else {
#ifdef _DEBUG
        std::cerr << "It is not MOV->JMP" << std::hex << (DWORD)jmp_ptr[0] << std::endl;
#endif
        return NULL;
    }
    //TODO: take into account also modifiers
    if (reg_id1 != reg_id0) {
#ifdef _DEBUG
        std::cerr << "MOV->JMP : reg mismatch" << std::endl;
#endif
        return NULL;
    }
    size_t patch_size = mov_instr_len;
    ULONGLONG addr = NULL;
    if (!is_long) { //32bit
        DWORD *lval = (DWORD*)((ULONGLONG) patch_ptr + 1);
        addr = *lval;
    } else { //64bit
        ULONGLONG *lval = (ULONGLONG*)((ULONGLONG) patch_ptr + 1);
        addr = *lval;
    }
    patch_size += 2; //add jump reg size
    patch.setHookTarget(addr);
#ifdef _DEBUG
    std::cout << "----> Target: " << std::hex << addr << std::endl;
#endif
    return patch_size;
}
 
size_t pesieve::PatchAnalyzer::parsePushRet(PatchList::Patch &patch, PBYTE patch_ptr)
{
    size_t instr_size = 5;
    if (!peconv::validate_ptr(this->patchedCode, this->codeSize, patch_ptr, instr_size + 1)) {
        return 0;
    }
    PBYTE ret_ptr = patch_ptr + instr_size; // next instruction
    if (ret_ptr[0] != 0xC3) {
        return NULL; // this is not push->ret
    }
    instr_size++;
    DWORD *lval = (DWORD*)((ULONGLONG) patch_ptr + 1);
    patch.setHookTarget(*lval);
    return instr_size;
}
 
bool pesieve::PatchAnalyzer::is64Modifier(BYTE op)
{
    if (!isModule64bit) return false;
    if (op >= 0x40 && op <= 0x4F) { // modifier
        return true;
    }
    return false;
}
 
bool pesieve::PatchAnalyzer::isLongModifier(BYTE op)
{
    if (!isModule64bit) return false;
    if (op >= 0x48 && op <= 0x4F) { // modifier
        return true;
    }
    return false;
}
 
size_t pesieve::PatchAnalyzer::_analyze(PatchList::Patch &patch, PBYTE patch_ptr, ULONGLONG patch_va)
{
    BYTE op = patch_ptr[0];
    if (op == OP_JMP || op == OP_CALL_DWORD) {
        return parseJmp(patch, patch_ptr, patch_va);
    }
    if (op == OP_SHORTJMP) {
        return parseShortJmp(patch, patch_ptr, patch_va);
    }
    if (op == OP_PUSH_DWORD) {
        return parsePushRet(patch, patch_ptr);
    }
    if (op == OP_JMP_VIA_ADDR_B1 && patch_ptr[1] == OP_JMP_VIA_ADDR_B2) {
        return parseJmpViaAddr(patch, patch_ptr, patch_va);
    }
 
    bool is_long = false;
    if (is64Modifier(op)) { // mov modifier
        if (isLongModifier(op)) {
            is_long = true;
        }
        op = patch_ptr[1];
    }
 
    if (op >= 0xB8 && op <= 0xBF) { // is mov
        return parseMovJmp(patch, patch_ptr, is_long);
    }
    return 0;
}
 
size_t pesieve::PatchAnalyzer::_analyzeRelocated(PatchList::Patch &patch, BYTE* patch_ptr)
{
    if (this->relocs.find(patch.startRva) == this->relocs.end()) {
        return 0;
    }
    // This patch is a relocated field
    const size_t fieldSize = (this->moduleData.is64bit()) ? sizeof(ULONGLONG) : sizeof(DWORD);
    if (!peconv::validate_ptr(this->patchedCode, this->codeSize, patch_ptr, fieldSize)) {
        return 0;
    }
    ULONGLONG field = (this->moduleData.is64bit()) ? *((ULONGLONG*)patch_ptr) : *((DWORD*)patch_ptr);
    patch.setHookTarget(field, true, pesieve::HOOK_ADDR_REPLACEMENT);
    return fieldSize;
}
 
size_t pesieve::PatchAnalyzer::analyze(PatchList::Patch &patch)
{
    const ULONGLONG patch_va = moduleData.rvaToVa(patch.startRva);
    const size_t patch_offset = patch.startRva - sectionRVA;
    BYTE* patch_ptr = this->patchedCode + patch_offset;
 
    size_t size = _analyzeRelocated(patch, patch_ptr);
    if (size) {
        return size;
    }
    const size_t kMinSize = 3;
    if (!peconv::validate_ptr(this->patchedCode, this->codeSize, patch_ptr, kMinSize)) {
        return 0;
    }
    size = _analyze(patch, patch_ptr, patch_va);
    if (size == 0 && patch_offset > 0) {
        //it may happen that the address of an existing JMP/CALL was replaced
        //try to parse a byte before the patch...
        size = _analyze(patch, patch_ptr -1, patch_va - 1);
        if (size > 0) {
            // substract the added position:
            size--;
        }
    }
    return size;
}