XML Security

1
XML Security

• September 13, 2006
• Robert Richards
• rrichards_at_php.net

2
Digital Signatures and Encryption

• Canonicalization
• A standard form of data
• Digital Signatures
• Provides proof of identity and authenticity which
  the sender cannot deny.
• Encryption
• Protection of data from being accessed by
  unauthorized parties.

3
Existing Tools/Technologies

• Secure Sockets Layer (SSL)
• Transport Layer Security (TLS)
• Pretty Good Privacy (PGP)
• GNU Privacy Guard (GnuPG)
• OpenPGP
• S/MIME
• x.509

4
XML Security Standards

• Canonical XML
• http//www.w3.org/TR/xml-c14n/
• Exclusive XML Canonicalization
• http//www.w3.org/TR/xml-exc-c14n/
• XML Signature
• http//www.w3.org/TR/xmldsig-core/
• XML Encryption
• http//www.w3.org/TR/xmlenc-core/
• XML Key Management
• http//www.w3.org/TR/xkms2/

5
Transmitting Data Over SSL/TLS
6
XML Security in PHP

• A library based on the xmlsec library is
  currently in the works
• http//www.aleksey.com/xmlsec/
• Provides granular control for working with XML
  Digital Signatures and XML Encryption
• PHP based libraries are available
• Model libraries for designing xmlsec wrapper
• Not officially mainitained and may not be
  backwards compatible with xmlsec based extension
• Requires PHP 5.1 (5.2 is recommended)
• Requires DOM, OpenSSL and Mcrypt
• http//www.cdatazone.org/files/xmlseclibs.phps
• http//www.cdatazone.org/files/soap-wsse.phps
• http//www.cdatazone.org/files/ws-amazon.phps
• http//www.cdatazone.org/infocard/infocard-lib.php
  s
• http//www.cdatazone.org/infocard/infocard.phps

7
Benefits of XML Security Standards

• XML is a structured format
• Allows for secure storage of documents
• Leverages existing technologies
• Provides granularity

8
XML Canonicalization

• A standard serialization of an XML document or
  XPath node set

ltdata a"1" b"2" c"3"/gt ltdata b"2" c"3"
a"1"/gt ltdata c"3" a"1" b"2"gtlt/datagt ltdata
c"3" a"1" b"2"gtlt/datagt ltdata
a"1" b"2" c"3"gtlt/datagt
9
Canonical XML (C14N)
http//www.w3.org/TR/2001/REC-xml-c14n-20010315 ht
tp//www.w3.org/TR/2001/REC-xml-c14n-20010315With
Comments

• XML declaration and DTD are removed
• The document is encoded in UTF-8
• Line breaks normalized to xA (linefeed) on
  input, before parsing
• Empty elements are converted to start-end tag
  pairs
• Whitespace outside of the document element and
  within start and end tags is normalized
• Attribute value delimiters are set to double
  quotes
• Superfluous namespace declarations are removed
  from each element
• Lexicographic order is imposed on the namespace
  declarations and attributes of each element

10
Canonical XML Example 1
lt?xml version"1.0" encoding"UTF-8"?gt lt?xml-style
sheet href"doc.xsl" type"text/xsl" ?gt lt!--
Comment --gt ltdocgt lte1 aattr'out'
battr'sorted' attr2'all' attr"I'm"
xmlnsb'http//www.ietf.org' xmlnsa"http//www.
w3.org" xmlns"http//example.org"/gt lte2
xmlns"" xmlnsa"http//www.w3.org"gt lte3
xmlns"" xmlnsa"http//www.w3.org"/gt
lt/e2gt lt/docgt
Canonical Form of Document (uncommented)
lt?xml-stylesheet href"doc.xsl" type"text/xsl"
?gt ltdocgt lte1 xmlns"http//example.org"
xmlnsa"http//www.w3.org" xmlnsb"http//www.ie
tf.org" attr"I'm" attr2"all" battr"sorted"
aattr"out"gtlt/e1gt lte2 xmlnsa"http//www.w3.o
rg"gt lte3gtlt/e3gt lt/e2gt lt/docgt
11
Canonical XML Example 1
lt?xml version"1.0" encoding"UTF-8"?gt lt?xml-style
sheet href"doc.xsl" type"text/xsl" ?gt lt!--
Comment --gt ltdocgt lte1 aattr'out'
battr'sorted' attr2'all' attr"I'm"
xmlnsb'http//www.ietf.org' xmlnsa"http//www.
w3.org" xmlns"http//example.org"/gt lte2
xmlns"" xmlnsa"http//www.w3.org"gt lte3
xmlns"" xmlnsa"http//www.w3.org"/gt
lt/e2gt lt/docgt
Canonical Form of Document (uncommented)
lt?xml-stylesheet href"doc.xsl" type"text/xsl"
?gt ltdocgt lte1 xmlns"http//example.org"
xmlnsa"http//www.w3.org" xmlnsb"http//www.ie
tf.org" attr"I'm" attr2"all" battr"sorted"
aattr"out"gtlt/e1gt lte2 xmlnsa"http//www.w3.o
rg"gt lte3gtlt/e3gt lt/e2gt lt/docgt
12
Canonical XML Example 1
lt?xml version"1.0" encoding"UTF-8"?gt lt?xml-style
sheet href"doc.xsl" type"text/xsl" ?gt lt!--
Comment --gt ltdocgt lte1 aattr'out'
battr'sorted' attr2'all' attr"I'm"
xmlnsb'http//www.ietf.org' xmlnsa"http//www.
w3.org" xmlns"http//example.org"/gt lte2
xmlns"" xmlnsa"http//www.w3.org"gt lte3
xmlns"" xmlnsa"http//www.w3.org"/gt
lt/e2gt lt/docgt
Canonical Form of Document (uncommented)
lt?xml-stylesheet href"doc.xsl" type"text/xsl"
?gt ltdocgt lte1 xmlns"http//example.org"
xmlnsa"http//www.w3.org" xmlnsb"http//www.ie
tf.org" attr"I'm" attr2"all" battr"sorted"
aattr"out"gtlt/e1gt lte2 xmlnsa"http//www.w3.o
rg"gt lte3gtlt/e3gt lt/e2gt lt/docgt
13
Canonical XML Example 1
lt?xml version"1.0" encoding"UTF-8"?gt lt?xml-style
sheet href"doc.xsl" type"text/xsl" ?gt lt!--
Comment --gt ltdocgt lte1 aattr'out'
battr'sorted' attr2'all' attr"I'm"
xmlnsb'http//www.ietf.org' xmlnsa"http//www.
w3.org" xmlns"http//example.org"/gt lte2
xmlns"" xmlnsa"http//www.w3.org"gt lte3
xmlns"" xmlnsa"http//www.w3.org"/gt
lt/e2gt lt/docgt
Canonical Form of Document (uncommented)
lt?xml-stylesheet href"doc.xsl" type"text/xsl"
?gt ltdocgt lte1 xmlns"http//example.org"
xmlnsa"http//www.w3.org" xmlnsb"http//www.ie
tf.org" attr"I'm" attr2"all" battr"sorted"
aattr"out"gtlt/e1gt lte2 xmlnsa"http//www.w3.o
rg"gt lte3gtlt/e3gt lt/e2gt lt/docgt
14
Canonical XML Example 2
lt?xml version"1.0" encoding"UTF-8"?gt ltdoc
xmlnsd"http//www.example.org/d"
xmlnsc"http//www.example.org/c"gt lte1
aattr"out" battr"sorted" attr2"all"
attr"I'm" xmlnsb"http//www.ietf.org"
xmlnsa"http//www.w3.org"
xmlns"http//example.org"/gt ltde2 xmlns""
xmlnsa"http//www.w3.org"gt lte3 xmlns""
xmlnsa"http//www.w3.org"/gt lt/de2gt lt/docgt
Canonical Form of Nodeset (uncommented) (//.
//_at_ //namespace)ancestor-or-selfde2
ltde2 xmlnsa"http//www.w3.org"
xmlnsc"http//www.example.org/c"
xmlnsd"http//www.example.org/d"gt
lte3gtlt/e3gt lt/de2gt
15
Canonical XML Example 2
lt?xml version"1.0" encoding"UTF-8"?gt ltdoc
xmlnsd"http//www.example.org/d"
xmlnsc"http//www.example.org/c"gt lte1
aattr"out" battr"sorted" attr2"all"
attr"I'm" xmlnsb"http//www.ietf.org"
xmlnsa"http//www.w3.org"
xmlns"http//example.org"/gt ltde2 xmlns""
xmlnsa"http//www.w3.org"gt lte3 xmlns""
xmlnsa"http//www.w3.org"/gt lt/de2gt lt/docgt
Canonical Form of Nodeset (uncommented) (//.
//_at_ //namespace)ancestor-or-selfde2
ltde2 xmlnsa"http//www.w3.org"
xmlnsc"http//www.example.org/c"
xmlnsd"http//www.example.org/d"gt
lte3gtlt/e3gt lt/de2gt
16
Canonical XML Example 2
lt?xml version"1.0" encoding"UTF-8"?gt ltdoc
xmlnsd"http//www.example.org/d"
xmlnsc"http//www.example.org/c"gt lte1
aattr"out" battr"sorted" attr2"all"
attr"I'm" xmlnsb"http//www.ietf.org"
xmlnsa"http//www.w3.org"
xmlns"http//example.org"/gt ltde2 xmlns""
xmlnsa"http//www.w3.org"gt lte3 xmlns""
xmlnsa"http//www.w3.org"/gt lt/de2gt lt/docgt
Canonical Form of Nodeset (uncommented) (//.
//_at_ //namespace)ancestor-or-selfde2
ltde2 xmlnsa"http//www.w3.org"
xmlnsc"http//www.example.org/c"
xmlnsd"http//www.example.org/d"gt
lte3gtlt/e3gt lt/de2gt
17
Problem with Re-Enveloping

• ltde2 xmlnsd"http//www.example.org/d"gtcontentlt/
  de2gt
• lt!-- Document wrapped within ns0e1 element --gt
• ltns0e1 xmlnsns0"www.example.org/ns0"gt
• ltde2 xmlnsd"http//www.example.org/d"gtconten
  tlt/de2gt
• lt/ns0e1gt
• lt!-- Canonical Form --gt
• ltde2 xmlnsd"http//www.example.org/d"
• xmlnsns0"www.example.org/ns0"gtcontentlt
  /de2gt
• lt!-- Document wrapped within ns1e1 element --gt
• ltns1e1 xmlnsns0"www.example.org/ns1"gt
• ltde2 xmlnsd"http//www.example.org/d"gtconten
  tlt/de2gt
• lt/ns1e1gt
• lt!-- Canonical Form --gt
• ltde2 xmlnsd"http//www.example.org/d"
• xmlnsns1"www.example.org/ns1"gtcontentlt
  /de2gt

18
Exclusive XML Canonicalization
http//www.w3.org/2001/10/xml-exc-c14n http//www
.w3.org/2001/10/xml-exc-c14nWithComments

• Follows the same rules as Canonical XML, except
• Attributes in the xml namespace are not imported
  into orphan nodes
• Namespaces not specially told to be added are
  only added on the starting element for which they
  are visible and not currently in scope within the
  output.

19
Re-Enveloping using Exclusive

• ltde2 xmlnsd"http//www.example.org/d"gtcontentlt/
  de2gt
• lt!-- Document wrapped within ns0e1 element --gt
• ltns0e1 xmlnsns0"www.example.org/ns0"gt
• ltde2 xmlnsd"http//www.example.org/d"gtconten
  tlt/de2gt
• lt/ns0e1gt
• lt!-- Canonical Form --gt
• ltde2 xmlnsd"http//www.example.org/d"gtcontentlt/
  de2gt
• lt!-- Document wrapped within ns1e1 element --gt
• ltns1e1 xmlnsns0"www.example.org/ns1"gt
• ltde2 xmlnsd"http//www.example.org/d"gtconten
  tlt/de2gt
• lt/ns1e1gt
• lt!-- Canonical Form --gt
• ltde2 xmlnsd"http//www.example.org/d"gtcontentlt/
  de2gt

20
Exclusive Canonical XML Example
lt?xml version"1.0" encoding"UTF-8"?gt ltdoc
xmlnsd"http//www.example.org/d"
xmlnsc"http//www.example.org/c"gt lte1
aattr"out" battr"sorted" attr2"all"
attr"I'm" xmlnsb"http//www.ietf.org"
xmlnsa"http//www.w3.org"
xmlns"http//example.org"/gt ltde2 xmlns""
xmlnsa"http//www.w3.org"gt lte3 xmlns""
xmlnsa"http//www.w3.org"/gt lt/de2gt lt/docgt
Exclusive Canonical Form of Nodeset
(uncommented) (//. //_at_ //namespace)ancest
or-or-selfde2
ltde2 xmlnsd"http//www.example.org/d"gt
lte3gtlt/e3gt lt/de2gt
21
XML Digital Signature (XMLDSIG)

• Insure that a message has not been altered or
  tampered with. (integrity)
• Protection against attacks that alter a message
  but maintain integrity. (message authentication)
• Provide a means for message auditing so that
  messages may not be repudiated. (signer
  authenticity)

22
XML Signature Structure
xmlns"http//www.w3.org/2000/09/xmldsig"

• ltSignaturegt
• ltSignedInfogt
• ltCanonicalizationMethod/gt
• ltSignatureMethod/gt
• (ltReference URI? gt
• (ltTransformsgt)?
• ltDigestMethodgt
• ltDigestValuegt
• lt/Referencegt)
• lt/SignedInfogt
• ltSignatureValuegt
• (ltKeyInfogt)?
• (ltObject Id?gt)
• lt/Signaturegt

23
XML Signature Types of Signatures

• Enveloping Signature
• Data lives within the XML Signature structure
• Good for signing data being packaged within an
  XML payload
• Enveloped Signature
• Data lives outside of and contains the XML
  Signature structure
• Good for signing portions or all of an XML
  document
• Detached Signature
• Data lives outside and DOES NOT contain the XML
  Signature structure
• Data may reside at a remote location addressable
  by URI

24
Enveloping Signature

• lt?xml version"1.0"?gt
• ltSignature xmlns"http//www.w3.org/2000/09/xmldsi
  g"gt
• ltSignedInfogt
• ltCanonicalizationMethod
• Algorithm"http//www.w3.org/TR/
  2001/REC-xml-c14n-20010315"/gt
• ltSignatureMethod
• Algorithm"http//www.w3.org/2000
  /09/xmldsighmac-sha1"/gt
• ltReference URI"myobj"gt
• ltDigestMethod Algorithm"http//www.w3.org/2
  000/09/xmldsigsha1"/gt
• ltDigestValuegtC2g9BLcGyGPCVKuF2byR1Ym6pElt/D
  igestValuegt
• lt/Referencegt
• lt/SignedInfogt
• ltSignatureValuegtR/XEOHDvR/jbmmpiuH4ZcRqC6clt/S
  ignatureValuegt
• ltObject Id"myobj"gtHello World!lt/Objectgt
• lt/Signaturegt

25
Enveloped Signature

• lt?xml version"1.0"?gt
• ltEnvelopegt
• ltDatagtcontentlt/Datagt
• ltSignature xmlns"http//www.w3.org/2000/09/xmldsi
  g"gt
• ltSignedInfogt
• ltCanonicalizationMethod Algorithm"http//www.
  w3.org/2001/10/xml-exc-c14n"/gt
• ltSignatureMethod Algorithm"http//www.w3.org/
  2000/09/xmldsighmac-sha1"/gt
• ltReferencegt
• ltTransformsgt
• ltTransform
• Algorithm"http//www.w3.org/2000/09
  /xmldsigenveloped-signature"/gt
• lt/Transformsgt
• ltDigestMethod Algorithm"http//www.w3.org/2
  000/09/xmldsigsha1"/gt
• ltDigestValuegtMMMkB0ZPp82XrUvJMFqDIEuXy0olt/D
  igestValuegt
• lt/Referencegt
• lt/SignedInfogt
• ltSignatureValuegtmVPvfcVSXi9elKLIcSCAzD4Jbklt/Si
  gnatureValuegt
• lt/Signaturegtlt/Envelopegt

26
Detached Signature

• lt?xml version"1.0"?gt
• ltSignature xmlns"http//www.w3.org/2000/09/xmldsi
  g"gt
• ltSignedInfogt
• ltCanonicalizationMethod
• Algorithm"http//www.w3.org/
  2001/10/xml-exc-c14n"/gt
• ltSignatureMethod
• Algorithm"http//www.w3.org/
  2000/09/xmldsighmac-sha1"/gt
• ltReference URI"http//www.ctindustries.net/te
  xt.txt"gt
• ltDigestMethod Algorithm"http//www.w3.org/2
  000/09/xmldsigsha1"/gt
• ltDigestValuegtoLZZOWcLwsAQ9NXWoLPk5FkPuSslt/D
  igestValuegt
• lt/Referencegt
• lt/SignedInfogt
• ltSignatureValuegtO9ykpFMXmkddzJ3CySrpzHBUW/Qlt/Sign
  atureValuegt
• lt/Signaturegt

27
XML Signature Generation

1. Apply any transforms to the data
2. Calculate the digest value
3. Create the Reference Element
4. Repeat steps 1 3 for each piece of data to be
   included
5. Create SignedInfo element with SignatureMethod,
   CanonicalizationMethod and Reference elements
6. Canonicalize the SignedInfo element
7. Calculate the SignatureValue over the
   canonicalized SignedInfo based the
   SignatureMethod
8. Assemble the Signature element

28
SOAP Request

• ltSOAP-ENVEnvelope
• xmlnsSOAP-ENV"http//schemas.xmlsoap.org/s
  oap/envelope/"
• xmlnsns1"http//www.csapi.org/schema/parla
  yx/terminal_location/v2_0/local"
• xmlnsxsd"http//www.w3.org/2001/XMLSchema"
  
• xmlnsxsi"http//www.w3.org/2001/XMLSchema-
  instance"gt
• ltSOAP-ENVBodygt
• ltns1getLocationgt
• ltaddressgttel1234567890lt/addressgt
• ltrequestedAccuracy xsitype"xsdint"gtxxlt/
  requestedAccuracygt
• ltacceptableAccuracy xsitype"xsdint"gtyylt
  /acceptableAccuracygt
• lt/ns1getLocationgt
• lt/SOAP-ENVBodygt
• lt/SOAP-ENVEnvelopegt

29
SOAP Request WS-Security (Signature)

• ltsoapenvEnvelope ...gt
• ltsoapenvHeadergt
• ltwsseSecurity xmlnswsse"http//docs.oasis
  -open.org/. . ." soapenvmustunderstand"1"gt
• ltwsseBinarySecurityToken . .
  .gtMIIE3zCCBEigAwIBAg . . .lt/wsseBinarySecurityTok
  engt
• ltdsSignature xmlnsds"http//www.w3.org
  /2000/09/xmldsig"gt
• ltdsSignedInfogt
• ltdsSignatureMethod
  Algorithm"http//www.w3.org/2000/09/xmldsigrsa-s
  ha1"/gt
• ltdsCanonicalizationMethod
  Algorithm"http//www.w3.org/2001/10/xml-exc-c14n
  "/gt
• ltdsReference URI"9b6c55bc-558f-e
  61a-e99a-ee2084f22000"gt. . .lt/dsReferencegt
• ltdsReference URI"c359df59-9262-d
  587-18af-add2c0dc1ddb"gt. . .lt/dsReferencegt
• lt/dsSignedInfogt
• ltdsSignatureValuegtYd1TGIjOb3q4UcQkUBu
  M3Q6Zs3G...lt/dsSignatureValuegt
• ltdsKeyInfogt. . .lt/dsKeyInfogt
• lt/dsSignaturegt
• ltwsuTimestamp xmlnswsu"http// ."
  wsuId"9b6c55bc-558f-e61a-e99a-ee2084f22000"gt
• lt/wsseSecuritygt
• lt/soapenvHeadergt
• ltsoapenvBody xmlnswsu"http//. . ."
  wsuId"c359df59-9262-d587-18af-add2c0dc1ddb"gt

30
SOAP Request WS-Security Generation

• require('soap-wsse.php')
• define('PRIVATE_KEY', 'private_key.pem')
• define('CERT_FILE', 'cert.pem')
• class mySoap extends SoapClient
• public function __doRequest(request,
  location, saction, version)
• doc new DOMDocument('1.0')
• doc-gtloadXML(request)
• / WS-Security Specific code here /
• return parent__doRequest(wsseRequest,
  location, saction, version)

31
SOAP Request WS-Security Generation

• objWSSE new WSSESoap(doc-gtloadXML(request))
  
• / add Timestamp with default expiration
  timestamp /
• objWSSE-gtaddTimestamp()
• / objWSSE-gtaddUserToken('username',
  'password', TRUE) /
• / create new XMLSec Key using RSA SHA-1 and
  type is private key /
• objKey new XMLSecurityKey(XMLSecurityKeyRSA_
  SHA1, array('type'gt'private'))
• / load private key from file - last arg is bool
  if key in file (TRUE) or is string (FALSE) /
• objKey-gtloadKey(PRIVATE_KEY, TRUE)
• / Sign the message - also signs appropraite
  WS-Security items /
• objWSSE-gtsignSoapDoc(objKey)
• / Add certificate (BinarySecurityToken) to the
  message and attach pointer to Signature /
• token objWSSE-gtaddBinaryToken(file_get_conten
  ts(CERT_FILE))
• objWSSE-gtattachTokentoSig(token)

32
SOAP Request signSoapDoc()

• objDSig new XMLSecurityDSig()
• objDSig-gtsetCanonicalMethod(XMLSecurityDSigEXC_
  C14N)
• arNodes array()
• / this-gtsecNode refers to wsseSecurity node
  within tree /
• foreach (this-gtsecNode-gtchildNodes AS node)
• if (node-gtnodeType XML_ELEMENT_NODE)
• arNodes node
• foreach (this-gtenvelope-gtchildNodes AS node)
• if (node-gtnamespaceURI this-gtsoapNS
  node-gtlocalName 'Body')
• arNodes node
• break
• arOptions array('prefix'gtWSSESoapWSUPFX,
  'prefix_ns'gtWSSESoapWSUNS)
• objDSig-gtaddReferenceList(arNodes,
  XMLSecurityDSigSHA1, NULL, arOptions)

33
XML Signature Validation

• Obtain the verification keying information
• Apply the CanonicalizationMethod to the
  SignedInfo element
• Verify the SignatureValue using the canonical
  form of the SignatureMethod
• For each Reference element within SignedInfo
• Obtain the data to be digested
• Digest the data using the DigestMethod within its
  Referece element
• Compare the computed value to that of the
  un-encoded value from the DigestValue element

34
XML Encryption (XMLENC)

• Encrypted data is maintained.
• All information needed to decrypt a document is
  contained within the document.
• Session can be secured on the document level and
  shared between multiple parties.
• Sensitive data is easily interchanged between
  applications.

35
XML Encryption Structure
xmlnsenc"http//www.w3.org/2001/04/xmlenc"

• ltencEncryptedData Id? Type? MimeType?gt
• ltencEncryptionMethod Algorithm /gt?
• ltdsigKeyInfogt?
• ltencCipherDatagt
• ltencCipherValuegt?
• ltencCipherReference URI?gt?
• lt/encCipherDatagt
• ltencEncryptionPropertiesgt?
• lt/encEncryptedDatagt

36
XML Encryption Encrypting

• Select the algorithm (and parameters) to use in
  encrypting the item.
• Obtain the key and create dsKeyInfo if necessary
• Encrypt the data and prepend any appropriate
  initialization vector (IV).
• Build CipherData element
• If to be stored within CipherValue element, then
  encrypted data is base64 encoded.
• If encrypted data is external, then create
  CipherReference with URI and any transforms.
• Build EncryptedData or EncryptedKey structure

37
XML Encryption Example
ltpaymentgt ltorder_numbergt1001lt/order_numbergt
ltcustomergtJoe Smithlt/customergt ltcreditcardgt
ltnumbergt4111 1111 1111 1111lt/numbergt
ltexpiration_monthgt01lt/expiration_monthgt
ltexpiration_yeargt2007lt/expiration_yeargt
ltccv2gt123lt/ccv2gt lt/creditcardgt lt/paymentgt
38
XML Encryption ExampleElement / Shared Secret Key
lt?xml version"1.0"?gt ltpaymentgt
ltorder_numbergt1001lt/order_numbergt
ltcustomergtJoe Smithlt/customergt ltEncryptedData
xmlns"http//www.w3.org/2001/04/xmlenc"
Type"http//www.w3.org/2001/04/xmlenc
Element"gt ltEncryptionMethod
Algorithm"http//www.w3.org/2001/04/xmlenctri
pledes-cbc"/gt ltCipherDatagt
ltCipherValuegtC5X1I65RCXlt/CipherValuegt
lt/CipherDatagt lt/EncryptedDatagt lt/paymentgt
39
XML Encryption Example Code

• require('xmlseclibs.php')
• / Using a shared secret key for encryption /
• key 'secret'
• doc new DOMDocument()
• xpath new DOMXPath(doc -gtload('payment.xml'))
  
• creditcard xpath-gtquery("//creditcard")-gtitem(
  0)
• enc new XMLSecEnc()
• enc-gtsetNode(creditcard)
• enc-gttype XMLSecEncElement
• / Use the libraries to encrypt the credit card
  element within the document /
• objKey new XMLSecurityKey(XMLSecurityKeyTRIPL
  EDES_CBC)
• objKey-gtloadKey(key)
• encNode enc-gtencryptNode(objKey)
• print encNode-gtownerDocument-gtsaveXML()

40
XML Encryption ExampleElement Content / Shared
Secret Key
lt?xml version"1.0"?gt ltpaymentgt
ltorder_numbergt1001lt/order_numbergt
ltcustomergtJoe Smithlt/customergt
ltcreditcardgtltEncryptedData
xmlns"http//www.w3.org/2001/04/xmlenc"
Type"http//www.w3.org
/2001/04/xmlencContent"gt
ltEncryptionMethod
Algorithm"http//www.w3.org/2001/04/xmlenctriple
des-cbc"/gt ltCipherDatagt
ltCipherValuegtC5X1I65RCXlt/CipherValuegt
lt/CipherDatagt lt/EncryptedDatagtlt/creditcardgt lt/p
aymentgt
41
XML Encryption ExampleArbitrary Data with Shared
Secret Key
lt?xml version'1.0'?gt ltEncryptedData
xmlns'http//www.w3.org/2001/04/xmlenc'
xmlnsds'http//www.w3.org/2000/09/xmldsig
' MimeType'text/xml'gt
ltCipherDatagt ltCipherValuegt...C5X1I65RCX...lt/Ci
pherValuegt lt/CipherDatagt lt/EncryptedDatagt
42
XML Encryption Decrypting

• Determine encryption algorithm and parameters.
• Obtain the decryption key information.
• Obtain the data to decrypt.
• If CipherData has a CipherValue child then
  base-64 decode its contents.
• If CipherData has a CipherReference child,
  retrieve the data and apply any Transforms.
• Depending upon algorithm and parameters, strip
  any IV from the data to use for decryption.
• Decrypt the cipher data with the encryption
  algorithm, parameters, and keying material.

43
XML Encryption Decrypting Example (Infocard)

• ltEncryptedData xmlns"http//www.w3.org/2001/04/xm
  lenc"
• Type"http//www.w3.org/200
  1/04/xmlencElement"gt
• ltEncryptionMethod Algorithm"http//www.w3.org/
  2001/04/xmlencaes256-cbc"/gt
• ltKeyInfo xmlns"http//www.w3.org/2000/09/xmlds
  ig"gt
• lteEncryptedKey xmlnse"http//www.w3.org/2
  001/04/xmlenc"gt
• lteEncryptionMethod Algorithm"http//www
  .w3.org/2001/04/xmlencrsa-oaep-mgf1p"gt
• ltDigestMethod Algorithm"http//www.w3
  .org/2000/09/xmldsigsha1"/gt
• lt/eEncryptionMethodgt
• ltKeyInfogt
• ltoSecurityTokenReference
  xmlnso"/oasis-200401-wss-wssecurity-secext-1.0.
  xsd"gt
• . . .lt/oSecurityTokenReferencegt
• lt/KeyInfogt
• lteCipherDatagt
• lteCipherValuegtkXja26CSDKssMeqJcsJttLg
  lt/eCipherValuegt
• lt/eCipherDatagt
• lt/eEncryptedKeygt
• lt/KeyInfogt

44
XML Encryption Code (Infocard)

• require('xmlseclibs.php')
• define('PRIVATE_KEY', 'site_sslprivate.key')
• define('SAML_ASSERT_NS', 'urnoasisnamestcSAML
  1.0assertion')
• encdom new DOMDocument()
• encdom-gtloadXML(xmlToken)
• objenc new XMLSecEnc()
• encData objenc-gtlocateEncryptedData(encdom)
• if (! encData)
• throw new Exception("Cannot locate Encrypted
  Data")
• objenc-gtsetNode(encData)
• objenc-gttype encData-gtgetAttribute("Type")

45
XML Encryption Code (Infocard)

• key NULL
• objKey objenc-gtlocateKey()
• if (objKey)
• if (objKeyInfo objenc-gtlocateKeyInfo(objKey)
  )
• if (objKeyInfo-gtisEncrypted)
• objencKey objKeyInfo-gtencryptedCtx
• objKeyInfo-gtloadKey(PRIVATE_KEY, TRUE)
• key objencKey-gtdecryptKey(objKeyInfo)
• if (empty(objKey) empty(key))
• throw new Exception("Error loading key to handle
  Decryption")
• objKey-gtloadKey(key)
• token NULL
• if (decrypt objenc-gtdecryptNode(objKey,
  FALSE))
• token new DOMDocument()
• token-gtloadXML(decrypt)

46
XML Encryption Code (Infocard)

• ltsamlAssertion ... AssertionID"uuid17818733-c53
  4-42d9-a6f6-4bb1c32d0de7"gt
• lt!-- SAML related information --gt
• ltSignature xmlns"http//www.w3.org/2000/09/xmld
  sig"gt
• ltSignedInfogt
• ltCanonicalizationMethod Algorithm"http//ww
  w.w3.org/2001/10/xml-exc-c14n"/gt
• ltSignatureMethod Algorithm"http//www.w3.or
  g/2000/09/xmldsigrsa-sha1"/gt
• ltReference URI"uuid17818733-c534-42d9-a6f
  6-4bb1c32d0de7"gt
• ltTransformsgt . . . lt/Transformsgt
• ltDigestMethod Algorithm"http//www.w3.org
  /2000/09/xmldsigsha1"/gt
• ltDigestValuegteHLrK4QSEkrDhHXZYHgGJMkPAU4lt
  /DigestValuegt
• lt/Referencegt
• lt/SignedInfogt
• ltSignatureValuegt0uDR9pr/TusV...lt/SignatureValu
  egt
• ltKeyInfogtltKeyValuegt
• ltRSAKeyValuegt
• ltModulusgt8llAGAvlPuG...lt/Modulusgt
• ltExponentgtAQABlt/Exponentgt
• lt/RSAKeyValuegt
• lt/KeyValuegtlt/KeyInfogt

47
XML Encryption Code (Infocard)

• / Validate the SAML token /
• objXMLSecDSig new XMLSecurityDSig()
• objXMLSecDSig-gtidKeys 'AssertionID'
• objDSig objXMLSecDSig-gtlocateSignature(token)
  
• / Canonicalize the signed info /
• objXMLSecDSig-gtcanonicalizeSignedInfo()
• retVal NULL
• if (objDSig) retVal objXMLSecDSig-gtvalidate
  Reference()
• if (! retVal) throw new Exception("SAML
  Validation Failed")
• objKey objXMLSecDSig-gtlocateKey()
• / Additional Key handling here /
• if (empty(objKey)) throw new Exception("Error
  loading key to handle Signature")
• if (! objXMLSecDSig-gtverify(objKey))

48
Signing and Encrypting

• Sign and then Encrypt
• Provides signature protection
• Allows for encryption algorithm to be changed
  without affecting signature
• Incurs additional overhead as you must decrypt
  before you can verify
• Encrypt and then Sign
• Immediately know if data has been tampered with
• Document can no longer be shared with other
  parties without revealing decryption key
• Sender identity is revealed

49
Questions?
50
XML Encryption in WS-Security

• ltenvEnvelope
• xmlnsenv"http//www.w3.org/2001/12/soap-en
  velope"
• xmlnsxenc"http//www.w3.org/2001/04/xmlenc
  "gt
• ltenvHeadergt
• ltwsseSecurity
• xmlnswsse"http//schemas.xmls
  oap.org/ws/2002/04/secext"gt
• ltxencReferenceListgt
• ltxencDataReference
  URI"encryptedID"/gt
• lt/xencReferenceListgt
• lt/wsseSecuritygt
• lt/envHeadergt
• ltenvBodygt
• ltxencEncryptedData Id"encryptedID"gt
• ltxencCipherDatagt
• ltxencCipherValuegt...lt/xencCipherValu
  egt
• lt/xencCipherDatagt
• lt/xencEncryptedDatagt
• lt/envBodygt
• lt/envEnvelopegt

51
XML Signature using Digital Certificate

• ltEnvelope xmlns"urnenvelope"gt
• ltDatagt
• Hello, World!
• lt/Datagt
• ltSignature xmlns"http//www.w3.org/2000/09/xmldsi
  g"gt
• ltSignedInfogt
• ltCanonicalizationMethod Algorithm"http//www.w3.o
  rg/2001/10/xml-exc-c14n"/gt
• ltSignatureMethod Algorithm"http//www.w3.org/2000
  /09/xmldsigrsa-sha1"/gt
• ltReferencegt
• ltTransformsgt
• ltTransform Algorithm"http//www.w3.org/2000/09/xm
  ldsigenveloped-signature"/gt
• lt/Transformsgt
• ltDigestMethod Algorithm"http//www.w3.org/2000/09
  /xmldsigsha1"/gt
• ltDigestValuegtHjY8ilZAIEM2tBbPn5mYO1ieIX4lt/DigestV
  aluegt
• lt/Referencegt
• lt/SignedInfogt
• ltSignatureValuegtSIaj/6KY3C . . .lt/SignatureValuegt
• ltKeyInfogt
• ltX509Datagt

52
XML Encryption w/ Digital Certificate

• ltEncryptedData xmlns"http//www.w3.org/2001/04/xm
  lenc"
• Type"http//www.w3.org
  /2001/04/xmlencElement"gt
• ltEncryptionMethod
• Algorithm"http//www.w3.org/2001/04/xml
  enctripledes-cbc"/gt
• ltKeyInfo xmlns"http//www.w3.org/2000/09/xmldsig
  "gt
• ltEncryptedKey xmlns"http//www.w3.org/2001/04/xm
  lenc"gt
• ltEncryptionMethod Algorithm"http//www.w3.org/
  2001/04/xmlencrsa-oaep-mgf1p"/gt
• ltKeyInfo xmlns"http//www.w3.org/2000/09/xmlds
  ig"gt
• ltKeyNamegtrsakey.pemlt/KeyNamegt
• lt/KeyInfogt
• ltCipherDatagt
• ltCipherValuegtIPiEu9NvEsGyvV . .
  .lt/CipherValuegt
• lt/CipherDatagt
• lt/EncryptedKeygt
• lt/KeyInfogt
• ltCipherDatagt
• ltCipherValuegtxrfPSABEI8 . . .lt/CipherValuegt
• lt/CipherDatagt
• lt/EncryptedDatagt