奇怪的东西

1.g++从stdin读入：cat - | g++ -xc++ - -o [filename]

2.memfd_create，可以在没有任何目录有写权限的情况下，在/proc/self/fd下创建文件（实际上内存中的）（没找出怎么创建文件夹）

https://www.secpulse.com/archives/70269.html

https://www.exploit-db.com/exploits/38473/

https://github.com/koraa/pipe_exec/blob/master/pexec.cc

https://stackoverflow.com/questions/17947800/how-to-compile-code-from-stdin

#include<bits/stdc++.h>
#include<unistd.h>
#include<sys/syscall.h>
#include<linux/memfd.h>
#include<sys/types.h>
using namespace std;
char line[233333];
void run(const string &d)
{
    //string cmd = d + " 2>&1";
    string cmd = d;
    FILE *fp;
    const char *sysCommand = cmd.data();
    if ((fp = popen(sysCommand, "r")) == NULL) {
        cout << "error" << endl;
        return;
    }
    while (fgets(line, sizeof(line)-1, fp) != NULL){
        cout << line ;
    }
    pclose(fp);
}
char buf1[]="#include<bits/stdc++.h>
using namespace std;
main(){puts("test");}";
int main()
{
    auto f1=syscall(SYS_memfd_create,"test.cpp",MFD_CLOEXEC);
    write(f1,buf1,strlen(buf1));
    auto f2=syscall(SYS_memfd_create,"test.out",MFD_CLOEXEC);
    //write(f2,buf2,sizeof(buf2)/sizeof(char));
    //string cmd = "ls -alF /proc/3/fd";
    //string cmd = "ls -alF /tmp/*/in 2>&1 ";
    //string cmd = "echo "#include<bits/stdc++.h>
using namespace std;
int main(){

int t=2;
return 0;
}" ";
    run("echo 2333 > /dev/shm 2>&1 ");
    run("ls -alF /dev/shm");
    int pd = getpid();
    string t1 = "/proc/" + to_string(pd) + "/fd/" + to_string(f1);
    string t2 = "/proc/" + to_string(pd) + "/fd/" + to_string(f2);
    string cmd = "cat " + t1 + " | g++ --verbose -pipe -xc++ - -o " + t2 ;
    cout << cmd;
    run(cmd);
    {
        int t;
        //scanf("%d", &t);
    }
    run(t2);
    return 0;
}