SSH Remote Code Execution

SSH Zero-Day | Made by ClumsyLulz & Taylor Christian Newsome

Summary

This repository contains a C program that accepts input parameters and generates a packet to be sent to a server over the SSH protocol. The program allocates a buffer to hold the data, writes it to a file, and constructs a command-line string to initiate an SSH connection to a specified host and port using the system function.

Identified Issues

Several security and stability issues exist in the current implementation:

1. Buffer Overflow: Only 28 bytes are allocated with malloc, but 29 bytes are written, which can cause memory corruption or segmentation faults.
2. Incorrect Return Address Calculation: The return address is computed using the packet length rather than the buffer size, resulting in an invalid value.
3. Format String Issue: The printf statement for the return address contains an incorrect format string, leading to undefined behavior.
4. Unchecked I/O Operations: The return values of open and write are not verified, risking data loss or incomplete writes.
5. Memory Leaks: Allocated memory for buffer and ssh pointers is never freed.
6. Unsafe Command Execution: Using system to execute the SSH command allows arbitrary commands to run with elevated privileges, posing a serious security risk.

Recommendations

To improve the program's security and reliability, the following changes are recommended:

• Allocate at least 29 bytes for the buffer to prevent overflow.
• Use the buffer size, not the packet length, when calculating the return address.
• Correct the format string in the printf statement for the return address.
• Check and handle return values for open and write calls.
• Free all dynamically allocated memory for buffer and ssh pointers.
• Replace system with a safer alternative like execvp to avoid executing arbitrary commands.

Implementing these fixes will enhance the program’s stability and reduce potential security vulnerabilities.

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root@vmi2865841:~/tools/SSH-Remote-Code-Execution# cat /etc/issue
Debian GNU/Linux 12 \n \l

root@vmi2865841:~/tools/SSH-Remote-Code-Execution# docker run -it --rm \
>   -v /root/tools/SSH-Remote-Code-Execution:/poc \
>   i386/debian:wheezy bash
root@29bcb37807cf:/# cat /etc/issue
Debian GNU/Linux 7 \n \l

root@29bcb37807cf:/# cat /etc/shadow
root:*:17955:0:99999:7:::
daemon:*:17955:0:99999:7:::
bin:*:17955:0:99999:7:::
sys:*:17955:0:99999:7:::
sync:*:17955:0:99999:7:::
games:*:17955:0:99999:7:::
man:*:17955:0:99999:7:::
lp:*:17955:0:99999:7:::
mail:*:17955:0:99999:7:::
news:*:17955:0:99999:7:::
uucp:*:17955:0:99999:7:::
proxy:*:17955:0:99999:7:::
www-data:*:17955:0:99999:7:::
backup:*:17955:0:99999:7:::
list:*:17955:0:99999:7:::
irc:*:17955:0:99999:7:::
gnats:*:17955:0:99999:7:::
nobody:*:17955:0:99999:7:::
libuuid:!:17955:0:99999:7:::
root@29bcb37807cf:/# cat /etc/passwd
root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/bin/sh
bin:x:2:2:bin:/bin:/bin/sh
sys:x:3:3:sys:/dev:/bin/sh
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/bin/sh
man:x:6:12:man:/var/cache/man:/bin/sh
lp:x:7:7:lp:/var/spool/lpd:/bin/sh
mail:x:8:8:mail:/var/mail:/bin/sh
news:x:9:9:news:/var/spool/news:/bin/sh
uucp:x:10:10:uucp:/var/spool/uucp:/bin/sh
proxy:x:13:13:proxy:/bin:/bin/sh
www-data:x:33:33:www-data:/var/www:/bin/sh
backup:x:34:34:backup:/var/backups:/bin/sh
list:x:38:38:Mailing List Manager:/var/list:/bin/sh
irc:x:39:39:ircd:/var/run/ircd:/bin/sh
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/bin/sh
nobody:x:65534:65534:nobody:/nonexistent:/bin/sh
libuuid:x:100:101::/var/lib/libuuid:/bin/sh
root@29bcb37807cf:/# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0@if11: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1500 qdisc noqueue state UP
    link/ether 1e:13:2e:66:6f:69 brd ff:ff:ff:ff:ff:ff
    inet 172.17.0.2/16 brd 172.17.255.255 scope global eth0
       valid_lft forever preferred_lft forever
root@29bcb37807cf:/# cd /bin/
root@29bcb37807cf:/bin# ls
bash   chmod  dash  df     dnsdomainname  egrep  findmnt  gzexe     ip     ls     mknod   mount       nisdomainname  ping6  readlink  run-parts  sh.distrib  stty  tailf     touch   uname       which         zcmp    zfgrep  zless
cat    chown  date  dir    domainname     false  grep     gzip      ln     lsblk  mktemp  mountpoint  pidof          pwd    rm        sed        sleep       su    tar       true    uncompress  ypdomainname  zdiff   zforce  zmore
chgrp  cp     dd    dmesg  echo           fgrep  gunzip   hostname  login  mkdir  more    mv          ping           rbash  rmdir     sh         ss          sync  tempfile  umount  vdir        zcat          zegrep  zgrep   znew
root@29bcb37807cf:/bin# df -h
Filesystem      Size  Used Avail Use% Mounted on
overlay         1.4T  977G  346G  74% /
tmpfs            64M     0   64M   0% /dev
shm              64M     0   64M   0% /dev/shm
/dev/sda1       1.4T  977G  346G  74% /poc
/dev/sda1       1.4T  977G  346G  74% /etc/resolv.conf
/dev/sda1       1.4T  977G  346G  74% /etc/hostname
/dev/sda1       1.4T  977G  346G  74% /etc/hosts
tmpfs            48G     0   48G   0% /proc/acpi
tmpfs            64M     0   64M   0% /proc/interrupts
tmpfs            64M     0   64M   0% /proc/kcore
tmpfs            64M     0   64M   0% /proc/keys
tmpfs            64M     0   64M   0% /proc/timer_list
tmpfs            48G     0   48G   0% /sys/firmware
root@29bcb37807cf:/bin# cat /proc/keys
root@29bcb37807cf:/bin# cat /etc/resolv.conf
# Generated by Docker Engine.
# This file can be edited; Docker Engine will not make further changes once it
# has been modified.

nameserver 1.1.1.1
nameserver 8.8.8.8
nameserver 213.136.95.10
nameserver 213.136.95.11
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