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dataflow pass

A trivial LLVM pass that instruct tainted memory access with DFSan.

Requirement:

  • LLVM 8.0.1
  • clang
  • compiler-rt (dataflow sanitizer)
  • lit (for running test suite)

Build:

mkdir build
cd build
cmake ..
make

Simple example

As for target source example/target.c

1	#include <string.h>
2	#include "runtime.h"
3	#define MAXSIZE 256
4	int main()
5	{
6	    char src[MAXSIZE] = {1};
7	    char dst[MAXSIZE] = {0};
8	    df_init(src, MAXSIZE);
9	    memcpy(dst, src, MAXSIZE/2);
10	    char temp;
11	    temp = dst[0];
12	    temp = dst[MAXSIZE/2 - 1];
13	    temp = dst[MAXSIZE/2];
14	    df_stat();
15	    return 0;
16	}
  1. 使用Clang编译target.c并插桩，在每一条Load（读内存）和Store（写内存）指令后分别插入对函数__loadcheck和__storecheck的调用。target.c中手动调用dfsan_create_label为src创建源标签，这样在后续每次读写内存后，DFSan会维护标签的传递情况，因此通过dfsan_has_label函数可以得知当前操作的目标指针指向的内容是否被src污染（注意memcpy被处理为先Store后Load，而memset为Store）。
cd example
clang -g -fsanitize=dataflow -std=c11 -Xclang -load -Xclang ../build/dataflow/libLoadStorePass.so -c target.c -o target.o
  1. 使用Clang编译runtime.c为库，提供插桩时插入函数调用的实现
clang -g -fsanitize=dataflow runtime.c -c -o runtime.o
  1. 链接到一起得到target
clang -fsanitize=dataflow target.o runtime.o -o target

Sample output of runtime checking:

DF_RUNTIME: N/A:0: clean store 4 byte(s)
DF_RUNTIME: target.c:6: clean store 256 byte(s)
DF_RUNTIME: target.c:6: clean store 1 byte(s)
DF_RUNTIME: target.c:7: clean store 256 byte(s)
DF_RUNTIME: label initialized
DF_RUNTIME: target.c:9: tainted store 128 byte(s)
DF_RUNTIME: target.c:9: tainted load 128 byte(s)
DF_RUNTIME: target.c:11: tainted load 1 byte(s)
DF_RUNTIME: target.c:11: tainted store 1 byte(s)
DF_RUNTIME: target.c:12: tainted load 1 byte(s)
DF_RUNTIME: target.c:12: tainted store 1 byte(s)
DF_RUNTIME: target.c:13: clean load 1 byte(s)
DF_RUNTIME: target.c:13: clean store 1 byte(s)
DF_RUNTIME: total 4 load, 3 tainted, 1 clean
DF_RUNTIME: total 4 store, 3 tainted, 1 clean