Transcript XML Encryption and Authentication

XML Security
September 13, 2006
Robert Richards
[email protected]
Digital Signatures and Encryption

Canonicalization
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Digital Signatures
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A standard form of data
Provides proof of identity and authenticity which
the sender cannot deny.
Encryption
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Protection of data from being accessed by
unauthorized parties.
Existing Tools/Technologies

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Secure Sockets Layer (SSL)
Transport Layer Security (TLS)
Pretty Good Privacy (PGP)
GNU Privacy Guard (GnuPG)
OpenPGP
S/MIME
x.509
XML Security Standards

Canonical XML
http://www.w3.org/TR/xml-c14n/
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Exclusive XML Canonicalization
http://www.w3.org/TR/xml-exc-c14n/
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XML Signature
http://www.w3.org/TR/xmldsig-core/
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XML Encryption
http://www.w3.org/TR/xmlenc-core/
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XML Key Management
http://www.w3.org/TR/xkms2/
Transmitting Data Over SSL/TLS
XML Security in PHP
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A library based on the xmlsec library is currently in the
works
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http://www.aleksey.com/xmlsec/
Provides granular control for working with XML Digital
Signatures and XML Encryption
PHP based libraries are available
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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.phps
http://www.cdatazone.org/infocard/infocard.phps
Benefits of XML Security Standards

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XML is a structured format
Allows for secure storage of documents
Leverages existing technologies
Provides granularity
XML Canonicalization
A standard serialization of an XML document or
XPath node set
<data a="1" b="2" c="3"/>
<data b="2" c="3" a="1"/>
<data c="3" a="1" b="2"></data>
<data c="3" a="1"
b="2"></data>
<data a="1" b="2" c="3"></data>
Canonical XML (C14N)
http://www.w3.org/TR/2001/REC-xml-c14n-20010315
http://www.w3.org/TR/2001/REC-xml-c14n-20010315#WithComments
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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
Canonical XML Example #1
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet href="doc.xsl" type="text/xsl" ?>
<!-- Comment -->
<doc>
<e1 a:attr='out' b:attr='sorted' attr2='all' attr="I'm"
xmlns:b='http://www.ietf.org' xmlns:a="http://www.w3.org"
xmlns="http://example.org"/>
<e2 xmlns="" xmlns:a="http://www.w3.org">
<e3 xmlns="" xmlns:a="http://www.w3.org"/>
</e2>
</doc>
Canonical Form of Document (uncommented)
<?xml-stylesheet href="doc.xsl" type="text/xsl" ?>
<doc>
<e1 xmlns="http://example.org" xmlns:a="http://www.w3.org"
xmlns:b="http://www.ietf.org" attr="I'm" attr2="all" b:attr="sorted" a:attr="out"></e1>
<e2 xmlns:a="http://www.w3.org">
<e3></e3>
</e2>
</doc>
Canonical XML Example #1
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet href="doc.xsl" type="text/xsl" ?>
<!-- Comment -->
<doc>
<e1 a:attr='out' b:attr='sorted' attr2='all' attr="I'm"
xmlns:b='http://www.ietf.org' xmlns:a="http://www.w3.org"
xmlns="http://example.org"/>
<e2 xmlns="" xmlns:a="http://www.w3.org">
<e3 xmlns="" xmlns:a="http://www.w3.org"/>
</e2>
</doc>
Canonical Form of Document (uncommented)
<?xml-stylesheet href="doc.xsl" type="text/xsl" ?>
<doc>
<e1 xmlns="http://example.org" xmlns:a="http://www.w3.org"
xmlns:b="http://www.ietf.org" attr="I'm" attr2="all" b:attr="sorted" a:attr="out"></e1>
<e2 xmlns:a="http://www.w3.org">
<e3></e3>
</e2>
</doc>
Canonical XML Example #1
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet href="doc.xsl" type="text/xsl" ?>
<!-- Comment -->
<doc>
<e1 a:attr='out' b:attr='sorted' attr2='all' attr="I'm"
xmlns:b='http://www.ietf.org' xmlns:a="http://www.w3.org"
xmlns="http://example.org"/>
<e2 xmlns="" xmlns:a="http://www.w3.org">
<e3 xmlns="" xmlns:a="http://www.w3.org"/>
</e2>
</doc>
Canonical Form of Document (uncommented)
<?xml-stylesheet href="doc.xsl" type="text/xsl" ?>
<doc>
<e1 xmlns="http://example.org" xmlns:a="http://www.w3.org"
xmlns:b="http://www.ietf.org" attr="I'm" attr2="all" b:attr="sorted" a:attr="out"></e1>
<e2 xmlns:a="http://www.w3.org">
<e3></e3>
</e2>
</doc>
Canonical XML Example #1
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet href="doc.xsl" type="text/xsl" ?>
<!-- Comment -->
<doc>
<e1 a:attr='out' b:attr='sorted' attr2='all' attr="I'm"
xmlns:b='http://www.ietf.org' xmlns:a="http://www.w3.org"
xmlns="http://example.org"/>
<e2 xmlns="" xmlns:a="http://www.w3.org">
<e3 xmlns="" xmlns:a="http://www.w3.org"/>
</e2>
</doc>
Canonical Form of Document (uncommented)
<?xml-stylesheet href="doc.xsl" type="text/xsl" ?>
<doc>
<e1 xmlns="http://example.org" xmlns:a="http://www.w3.org"
xmlns:b="http://www.ietf.org" attr="I'm" attr2="all" b:attr="sorted" a:attr="out"></e1>
<e2 xmlns:a="http://www.w3.org">
<e3></e3>
</e2>
</doc>
Canonical XML Example #2
<?xml version="1.0" encoding="UTF-8"?>
<doc xmlns:d="http://www.example.org/d"
xmlns:c="http://www.example.org/c">
<e1 a:attr="out" b:attr="sorted" attr2="all" attr="I'm"
xmlns:b="http://www.ietf.org" xmlns:a="http://www.w3.org"
xmlns="http://example.org"/>
<d:e2 xmlns="" xmlns:a="http://www.w3.org">
<e3 xmlns="" xmlns:a="http://www.w3.org"/>
</d:e2>
</doc>
Canonical Form of Nodeset (uncommented)
(//. | //@* | //namespace::*)[ancestor-or-self::d:e2]
<d:e2 xmlns:a="http://www.w3.org" xmlns:c="http://www.example.org/c"
xmlns:d="http://www.example.org/d">
<e3></e3>
</d:e2>
Canonical XML Example #2
<?xml version="1.0" encoding="UTF-8"?>
<doc xmlns:d="http://www.example.org/d"
xmlns:c="http://www.example.org/c">
<e1 a:attr="out" b:attr="sorted" attr2="all" attr="I'm"
xmlns:b="http://www.ietf.org" xmlns:a="http://www.w3.org"
xmlns="http://example.org"/>
<d:e2 xmlns="" xmlns:a="http://www.w3.org">
<e3 xmlns="" xmlns:a="http://www.w3.org"/>
</d:e2>
</doc>
Canonical Form of Nodeset (uncommented)
(//. | //@* | //namespace::*)[ancestor-or-self::d:e2]
<d:e2 xmlns:a="http://www.w3.org" xmlns:c="http://www.example.org/c"
xmlns:d="http://www.example.org/d">
<e3></e3>
</d:e2>
Canonical XML Example #2
<?xml version="1.0" encoding="UTF-8"?>
<doc xmlns:d="http://www.example.org/d"
xmlns:c="http://www.example.org/c">
<e1 a:attr="out" b:attr="sorted" attr2="all" attr="I'm"
xmlns:b="http://www.ietf.org" xmlns:a="http://www.w3.org"
xmlns="http://example.org"/>
<d:e2 xmlns="" xmlns:a="http://www.w3.org">
<e3 xmlns="" xmlns:a="http://www.w3.org"/>
</d:e2>
</doc>
Canonical Form of Nodeset (uncommented)
(//. | //@* | //namespace::*)[ancestor-or-self::d:e2]
<d:e2 xmlns:a="http://www.w3.org" xmlns:c="http://www.example.org/c"
xmlns:d="http://www.example.org/d">
<e3></e3>
</d:e2>
Problem with Re-Enveloping
<d:e2 xmlns:d="http://www.example.org/d">content</d:e2>
<!-- Document wrapped within ns0:e1 element -->
<ns0:e1 xmlns:ns0="www.example.org/ns0">
<d:e2 xmlns:d="http://www.example.org/d">content</d:e2>
</ns0:e1>
<!-- Canonical Form -->
<d:e2 xmlns:d="http://www.example.org/d"
xmlns:ns0="www.example.org/ns0">content</d:e2>
<!-- Document wrapped within ns1:e1 element -->
<ns1:e1 xmlns:ns0="www.example.org/ns1">
<d:e2 xmlns:d="http://www.example.org/d">content</d:e2>
</ns1:e1>
<!-- Canonical Form -->
<d:e2 xmlns:d="http://www.example.org/d"
xmlns:ns1="www.example.org/ns1">content</d:e2>
Exclusive XML Canonicalization
http://www.w3.org/2001/10/xml-exc-c14n#
http://www.w3.org/2001/10/xml-exc-c14n#WithComments
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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.
Re-Enveloping using Exclusive
<d:e2 xmlns:d="http://www.example.org/d">content</d:e2>
<!-- Document wrapped within ns0:e1 element -->
<ns0:e1 xmlns:ns0="www.example.org/ns0">
<d:e2 xmlns:d="http://www.example.org/d">content</d:e2>
</ns0:e1>
<!-- Canonical Form -->
<d:e2 xmlns:d="http://www.example.org/d">content</d:e2>
<!-- Document wrapped within ns1:e1 element -->
<ns1:e1 xmlns:ns0="www.example.org/ns1">
<d:e2 xmlns:d="http://www.example.org/d">content</d:e2>
</ns1:e1>
<!-- Canonical Form -->
<d:e2 xmlns:d="http://www.example.org/d">content</d:e2>
Exclusive Canonical XML
Example
<?xml version="1.0" encoding="UTF-8"?>
<doc xmlns:d="http://www.example.org/d"
xmlns:c="http://www.example.org/c">
<e1 a:attr="out" b:attr="sorted" attr2="all" attr="I'm"
xmlns:b="http://www.ietf.org" xmlns:a="http://www.w3.org"
xmlns="http://example.org"/>
<d:e2 xmlns="" xmlns:a="http://www.w3.org">
<e3 xmlns="" xmlns:a="http://www.w3.org"/>
</d:e2>
</doc>
Exclusive Canonical Form of Nodeset (uncommented)
(//. | //@* | //namespace::*)[ancestor-or-self::d:e2]
<d:e2 xmlns:d="http://www.example.org/d">
<e3></e3>
</d:e2>
XML Digital Signature (XMLDSIG)
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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)
XML Signature Structure
xmlns="http://www.w3.org/2000/09/xmldsig#"
<Signature>
<SignedInfo>
<CanonicalizationMethod/>
<SignatureMethod/>
(<Reference URI? >
(<Transforms>)?
<DigestMethod>
<DigestValue>
</Reference>)+
</SignedInfo>
<SignatureValue>
(<KeyInfo>)?
(<Object Id?>)*
</Signature>
XML Signature: Types of Signatures
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Enveloping Signature
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Enveloped Signature
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Data lives within the XML Signature structure
Good for signing data being packaged within an XML payload
Data lives outside of and contains the XML Signature structure
Good for signing portions or all of an XML document
Detached Signature
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Data lives outside and DOES NOT contain the XML Signature
structure
Data may reside at a remote location addressable by URI
Enveloping Signature
<?xml version="1.0"?>
<Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
<SignedInfo>
<CanonicalizationMethod
Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315"/>
<SignatureMethod
Algorithm="http://www.w3.org/2000/09/xmldsig#hmac-sha1"/>
<Reference URI="#myobj">
<DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/>
<DigestValue>C2g9BLcGyGPCVKuF2byR1Ym+6pE=</DigestValue>
</Reference>
</SignedInfo>
<SignatureValue>+R/XEOHDvR/jbmmpiuH4ZcRqC6c=</SignatureValue>
<Object Id="myobj">Hello World!</Object>
</Signature>
Enveloped Signature
<?xml version="1.0"?>
<Envelope>
<Data>content</Data>
<Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
<SignedInfo>
<CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
<SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#hmac-sha1"/>
<Reference>
<Transforms>
<Transform
Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature"/>
</Transforms>
<DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/>
<DigestValue>MMMkB0ZPp82XrUvJMFqDIEuXy0o=</DigestValue>
</Reference>
</SignedInfo>
<SignatureValue>mVPvfcVSXi9elKL+IcSCAzD4Jbk=</SignatureValue>
</Signature></Envelope>
Detached Signature
<?xml version="1.0"?>
<Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
<SignedInfo>
<CanonicalizationMethod
Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
<SignatureMethod
Algorithm="http://www.w3.org/2000/09/xmldsig#hmac-sha1"/>
<Reference URI="http://www.ctindustries.net/text.txt">
<DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/>
<DigestValue>oLZZOWcLwsAQ9NXWoLPk5FkPuSs=</DigestValue>
</Reference>
</SignedInfo>
<SignatureValue>O9ykpFMXmkddzJ3CySrpzHBUW/Q=</SignatureValue>
</Signature>
XML Signature Generation
1.
2.
3.
4.
5.
6.
7.
8.
Apply any transforms to the data
Calculate the digest value
Create the Reference Element
Repeat steps 1 – 3 for each piece of data to be included
Create SignedInfo element with SignatureMethod,
CanonicalizationMethod and Reference elements
Canonicalize the SignedInfo element
Calculate the SignatureValue over the canonicalized
SignedInfo based the SignatureMethod
Assemble the Signature element
SOAP Request
<SOAP-ENV:Envelope
xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:ns1="http://www.csapi.org/schema/parlayx/terminal_location/v2_0/local"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<SOAP-ENV:Body>
<ns1:getLocation>
<address>tel:1234567890</address>
<requestedAccuracy xsi:type="xsd:int">xx</requestedAccuracy>
<acceptableAccuracy
xsi:type="xsd:int">yy</acceptableAccuracy>
</ns1:getLocation>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>
SOAP Request: WS-Security (Signature)
<soapenv:Envelope ...>
<soapenv:Header>
<wsse:Security xmlns:wsse="http://docs.oasis-open.org/. . ." soapenv:mustunderstand="1">
<wsse:BinarySecurityToken . . .>MIIE3zCCBEigAwIBAg . . .</wsse:BinarySecurityToken>
<ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
<ds:SignedInfo>
<ds:SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1"/>
<ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
<ds:Reference URI="#9b6c55bc-558f-e61a-e99a-ee2084f22000">. . .</ds:Reference>
<ds:Reference URI="#c359df59-9262-d587-18af-add2c0dc1ddb">. . .</ds:Reference>
</ds:SignedInfo>
<ds:SignatureValue>Yd1TGIjOb3q4UcQkUBuM3Q6Zs3G...</ds:SignatureValue>
<ds:KeyInfo>. . .</ds:KeyInfo>
</ds:Signature>
<wsu:Timestamp xmlns:wsu="http:// ." wsu:Id="9b6c55bc-558f-e61a-e99a-ee2084f22000">
</wsse:Security>
</soapenv:Header>
<soapenv:Body xmlns:wsu="http://. . ." wsu:Id="c359df59-9262-d587-18af-add2c0dc1ddb">
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');
$doc->loadXML($request);
/* WS-Security Specific code here */
return parent::__doRequest($wsseRequest, $location, $saction, $version);
}
}
SOAP Request: WS-Security Generation
$objWSSE = new WSSESoap($doc->loadXML($request));
/* add Timestamp with default expiration timestamp */
$objWSSE->addTimestamp();
/* $objWSSE->addUserToken('username', 'password', TRUE); */
/* create new XMLSec Key using RSA SHA-1 and type is private key */
$objKey = new XMLSecurityKey(XMLSecurityKey::RSA_SHA1, array('type'=>'private'));
/* load private key from file - last arg is bool if key in file (TRUE) or is string (FALSE) */
$objKey->loadKey(PRIVATE_KEY, TRUE);
/* Sign the message - also signs appropraite WS-Security items */
$objWSSE->signSoapDoc($objKey);
/* Add certificate (BinarySecurityToken) to the message and attach pointer to Signature */
$token = $objWSSE->addBinaryToken(file_get_contents(CERT_FILE));
$objWSSE->attachTokentoSig($token);
$wsseRequest = $objWSSE->saveXML();
SOAP Request: signSoapDoc()
$objDSig = new XMLSecurityDSig();
$objDSig->setCanonicalMethod(XMLSecurityDSig::EXC_C14N);
$arNodes = array();
/* $this->secNode refers to wsse:Security node within tree */
foreach ($this->secNode->childNodes AS $node) {
if ($node->nodeType == XML_ELEMENT_NODE)
$arNodes[] = $node;
}
foreach ($this->envelope->childNodes AS $node) {
if ($node->namespaceURI == $this->soapNS && $node->localName == 'Body') {
$arNodes[] = $node;
break;
}
}
$arOptions = array('prefix'=>WSSESoap::WSUPFX, 'prefix_ns'=>WSSESoap::WSUNS);
$objDSig->addReferenceList($arNodes, XMLSecurityDSig::SHA1, NULL, $arOptions);
$objDSig->sign($objKey);
$objDSig->appendSignature($this->secNode, TRUE);
XML Signature Validation
1.
2.
3.
4.
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:
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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
XML Encryption (XMLENC)
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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.
XML Encryption Structure
xmlns:enc="http://www.w3.org/2001/04/xmlenc#"
<enc:EncryptedData Id? Type? MimeType?>
<enc:EncryptionMethod Algorithm />?
<dsig:KeyInfo>?
<enc:CipherData>
<enc:CipherValue>?
<enc:CipherReference URI?>?
</enc:CipherData>
<enc:EncryptionProperties>?
</enc:EncryptedData>
XML Encryption: Encrypting
1.
2.
3.
4.
Select the algorithm (and parameters) to use in
encrypting the item.
Obtain the key and create ds:KeyInfo if necessary
Encrypt the data and prepend any appropriate
initialization vector (IV).
Build CipherData element
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5.
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
XML Encryption Example
<payment>
<order_number>1001</order_number>
<customer>Joe Smith</customer>
<creditcard>
<number>4111 1111 1111 1111</number>
<expiration_month>01</expiration_month>
<expiration_year>2007</expiration_year>
<ccv2>123</ccv2>
</creditcard>
</payment>
XML Encryption Example
Element / Shared Secret Key
<?xml version="1.0"?>
<payment>
<order_number>1001</order_number>
<customer>Joe Smith</customer>
<EncryptedData xmlns="http://www.w3.org/2001/04/xmlenc#"
Type="http://www.w3.org/2001/04/xmlenc#Element">
<EncryptionMethod
Algorithm="http://www.w3.org/2001/04/xmlenc#tripledes-cbc"/>
<CipherData>
<CipherValue>C5X1I65RCX…</CipherValue>
</CipherData>
</EncryptedData>
</payment>
XML Encryption Example: Code
require('xmlseclibs.php');
/* Using a shared secret key for encryption */
$key = 'secret';
$doc = new DOMDocument();
$xpath = new DOMXPath($doc ->load('payment.xml'));
$creditcard = $xpath->query("//creditcard")->item(0);
$enc = new XMLSecEnc();
$enc->setNode($creditcard);
$enc->type = XMLSecEnc::Element;
/* Use the libraries to encrypt the credit card element within the document */
$objKey = new XMLSecurityKey(XMLSecurityKey::TRIPLEDES_CBC);
$objKey->loadKey($key);
$encNode = $enc->encryptNode($objKey);
print $encNode->ownerDocument->saveXML();
XML Encryption Example
Element Content / Shared Secret Key
<?xml version="1.0"?>
<payment>
<order_number>1001</order_number>
<customer>Joe Smith</customer>
<creditcard><EncryptedData
xmlns="http://www.w3.org/2001/04/xmlenc#"
Type="http://www.w3.org/2001/04/xmlenc#Content">
<EncryptionMethod
Algorithm="http://www.w3.org/2001/04/xmlenc#tripledes-cbc"/>
<CipherData>
<CipherValue>C5X1I65RCX…</CipherValue>
</CipherData>
</EncryptedData></creditcard>
</payment>
XML Encryption Example
Arbitrary Data with Shared Secret Key
<?xml version='1.0'?>
<EncryptedData xmlns='http://www.w3.org/2001/04/xmlenc#'
xmlns:ds='http://www.w3.org/2000/09/xmldsig#'
MimeType='text/xml'>
<CipherData>
<CipherValue>...C5X1I65RCX...</CipherValue>
</CipherData>
</EncryptedData>
XML Encryption: Decrypting
1.
2.
3.
Determine encryption algorithm and parameters.
Obtain the decryption key information.
Obtain the data to decrypt.


4.
5.
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.
XML Encryption: Decrypting Example (Infocard)
<EncryptedData xmlns="http://www.w3.org/2001/04/xmlenc#"
Type="http://www.w3.org/2001/04/xmlenc#Element">
<EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#aes256-cbc"/>
<KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#">
<e:EncryptedKey xmlns:e="http://www.w3.org/2001/04/xmlenc#">
<e:EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p">
<DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/>
</e:EncryptionMethod>
<KeyInfo>
<o:SecurityTokenReference xmlns:o="…/oasis-200401-wss-wssecurity-secext-1.0.xsd">
. . .</o:SecurityTokenReference>
</KeyInfo>
<e:CipherData>
<e:CipherValue>kXja26CSDKssMeqJcsJttLg…</e:CipherValue>
</e:CipherData>
</e:EncryptedKey>
</KeyInfo>
<CipherData><CipherValue>eIreM+S35Q+=…</CipherValue></CipherData>
</EncryptedData>
XML Encryption: Code (Infocard)
require('xmlseclibs.php');
define('PRIVATE_KEY', 'site_sslprivate.key');
define('SAML_ASSERT_NS', 'urn:oasis:names:tc:SAML:1.0:assertion');
$encdom = new DOMDocument();
$encdom->loadXML($xmlToken);
$objenc = new XMLSecEnc();
$encData = $objenc->locateEncryptedData($encdom);
if (! $encData) {
throw new Exception("Cannot locate Encrypted Data");
}
$objenc->setNode($encData);
$objenc->type = $encData->getAttribute("Type");
XML Encryption: Code (Infocard)
$key = NULL;
$objKey = $objenc->locateKey();
if ($objKey)
if ($objKeyInfo = $objenc->locateKeyInfo($objKey))
if ($objKeyInfo->isEncrypted) {
$objencKey = $objKeyInfo->encryptedCtx;
$objKeyInfo->loadKey(PRIVATE_KEY, TRUE);
$key = $objencKey->decryptKey($objKeyInfo);
}
if (empty($objKey) || empty($key))
throw new Exception("Error loading key to handle Decryption");
$objKey->loadKey($key);
$token = NULL;
if ($decrypt = $objenc->decryptNode($objKey, FALSE)) {
$token = new DOMDocument();
$token->loadXML($decrypt);
}
XML Encryption: Code (Infocard)
<saml:Assertion ... AssertionID="uuid:17818733-c534-42d9-a6f6-4bb1c32d0de7">
<!-- SAML related information -->
<Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
<SignedInfo>
<CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
<SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1"/>
<Reference URI="#uuid:17818733-c534-42d9-a6f6-4bb1c32d0de7">
<Transforms> . . . </Transforms>
<DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/>
<DigestValue>eHLrK4QSEkrDhHXZYHgGJMkPAU4=</DigestValue>
</Reference>
</SignedInfo>
<SignatureValue>0uDR9pr/TusV...</SignatureValue>
<KeyInfo><KeyValue>
<RSAKeyValue>
<Modulus>8llAGAvlPuG...</Modulus>
<Exponent>AQAB</Exponent>
</RSAKeyValue>
</KeyValue></KeyInfo>
</Signature>
XML Encryption: Code (Infocard)
/* Validate the SAML token */
$objXMLSecDSig = new XMLSecurityDSig();
$objXMLSecDSig->idKeys[] = 'AssertionID';
$objDSig = $objXMLSecDSig->locateSignature($token);
/* Canonicalize the signed info */
$objXMLSecDSig->canonicalizeSignedInfo();
$retVal = NULL;
if ($objDSig) { $retVal = $objXMLSecDSig->validateReference(); }
if (! $retVal) { throw new Exception("SAML Validation Failed"); }
$objKey = $objXMLSecDSig->locateKey();
/* Additional Key handling here */
if (empty($objKey)) throw new Exception("Error loading key to handle Signature");
if (! $objXMLSecDSig->verify($objKey))
throw new Exception("Unable to validate Signature");
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
Questions?
XML Encryption in WS-Security
<env:Envelope
xmlns:env="http://www.w3.org/2001/12/soap-envelope"
xmlns:xenc="http://www.w3.org/2001/04/xmlenc#">
<env:Header>
<wsse:Security
xmlns:wsse="http://schemas.xmlsoap.org/ws/2002/04/secext">
<xenc:ReferenceList>
<xenc:DataReference URI="#encryptedID"/>
</xenc:ReferenceList>
</wsse:Security>
</env:Header>
<env:Body>
<xenc:EncryptedData Id="encryptedID">
<xenc:CipherData>
<xenc:CipherValue>...</xenc:CipherValue>
</xenc:CipherData>
</xenc:EncryptedData>
</env:Body>
</env:Envelope>
XML Signature using Digital Certificate
<Envelope xmlns="urn:envelope">
<Data>
Hello, World!
</Data>
<Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
<SignedInfo>
<CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
<SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1"/>
<Reference>
<Transforms>
<Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature"/>
</Transforms>
<DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/>
<DigestValue>HjY8ilZAIEM2tBbPn5mYO1ieIX4=</DigestValue>
</Reference>
</SignedInfo>
<SignatureValue>SIaj/6KY3C . . .</SignatureValue>
<KeyInfo>
<X509Data>
<X509Certificate>MIIE3zCCBEjAUB9 . . .</X509Certificate>
</X509Data>
</KeyInfo>
</Signature></Envelope>
XML Encryption w/ Digital Certificate
<EncryptedData xmlns="http://www.w3.org/2001/04/xmlenc#"
Type="http://www.w3.org/2001/04/xmlenc#Element">
<EncryptionMethod
Algorithm="http://www.w3.org/2001/04/xmlenc#tripledes-cbc"/>
<KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#">
<EncryptedKey xmlns="http://www.w3.org/2001/04/xmlenc#">
<EncryptionMethod
Algorithm="http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p"/>
<KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#">
<KeyName>rsakey.pem</KeyName>
</KeyInfo>
<CipherData>
<CipherValue>IPiEu9Nv+EsGyvV . . .</CipherValue>
</CipherData>
</EncryptedKey>
</KeyInfo>
<CipherData>
<CipherValue>xrfPSA+BEI+8 . . .</CipherValue>
</CipherData>
</EncryptedData>