Goal:
Using command to get the password which is stored in a file somewhere on the server directory and has three properties:
1. Owned by user bandit7,
2. owned by group bandit6,
3. 33 bytes in size.
Login command: ssh bandit6@bandit.labs.overthewire.org -p 2220
Password: P4L4vucdmLnm8I7Vl7jG1ApGSfjYKqJU
My Solution:
As we know, when we use the 'find' command, we can specify files based on their size. Following this concept, we first use '-size 33c' as a parameter. While consulting the man page of 'find' command, I noticed the terms 'user' and 'group'. By adding 'user' and 'group' after the parameters, we can specify a particular user or group. Combining these three pieces of information, the command now looks like 'find -size 33c -user bandit7 -group bandit6'.
Next, the challenge is to determine "Where is the file?" According to the goal, the file exists somewhere on the server. Therefore, we scan the root directory, which includes all files on the system. With all the information we have, we entered 'find / -size 33c -user bandit7 -group bandit6'. However, there are many files, and most of them we cannot view due to lack of permission. By searching for "permission denied" errors, I discovered that we can use '2>/dev/null' to suppress errors for files we don't have permission to access. '2>/dev/null' helps exclude all errors by redirecting them to /dev/null. Therefore, using '2>/dev/null' causes all errors to disappear. By entering 'find / -size 33c -user bandit7 -group bandit6 2>/dev/null', we can easily obtain a path leading us to the key.
The Key
z7WtoNQU2XfjmMtWA8u5rN4vzqu4v99S
References
https://man7.org/linux/man-pages/man1/find.1.html
https://arzhost.com/blogs/linux-find-ignore-permission-denied/
https://stackoverflow.com/questions/762348/how-can-i-exclude-all-permission-denied-messages-from-find