blob: 35222d2ad78b331a9cf9c1c586822fbb8d80e22b (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
|
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Transforms and transforms chain.</title>
<meta name="GENERATOR" content="Modular DocBook HTML Stylesheet Version 1.79">
<link rel="HOME" title="XML Security Library Reference Manual" href="index.html">
<link rel="UP" title="XML Security Library Tutorial" href="xmlsec-notes.html">
<link rel="PREVIOUS" title="Verifing document signed with X509 certificates." href="xmlsec-notes-verify-x509.html">
<link rel="NEXT" title="Using context objects." href="xmlsec-notes-contexts.html">
<style type="text/css">.synopsis, .classsynopsis {
background: #eeeeee;
border: solid 1px #aaaaaa;
padding: 0.5em;
}
.programlisting {
background: #eeeeff;
border: solid 1px #aaaaff;
padding: 0.5em;
}
.variablelist {
padding: 4px;
margin-left: 3em;
}
.navigation {
background: #ffeeee;
border: solid 1px #ffaaaa;
margin-top: 0.5em;
margin-bottom: 0.5em;
}
.navigation a {
color: #770000;
}
.navigation a:visited {
color: #550000;
}
.navigation .title {
font-size: 200%;
}</style>
<style type="text/css">
table.CALSTABLE > tbody > tr:nth-child(1) > td:nth-child(1) {
width: 20em;
}
.synopsis, .classsynopsis {
background: #eeeeee;
border: solid 1px #aaaaaa;
}
.programlisting {
background: #eeeeee;
border: solid 1px #000000;
}
.navigation {
background: #eeeeee;
border: solid 1px #000000;
}
.navigation a {
color: initial;
}
.navigation a:visited {
color: initial;
}
</style>
</head>
<body><table width="100%" valign="top"><tr valign="top">
<td valign="top" align="left" width="210">
<img src="../images/logo.gif" alt="XML Security Library" border="0"><p></p>
<ul>
<li><a href="../index.html">Home</a></li>
<li><a href="../download.html">Download</a></li>
<li><a href="../news.html">News</a></li>
<li><a href="../documentation.html">Documentation</a></li>
<ul>
<li><a href="../faq.html">FAQ</a></li>
<li><a href="../api/xmlsec-notes.html">Tutorial</a></li>
<li><a href="../api/xmlsec-reference.html">API reference</a></li>
<li><a href="../api/xmlsec-examples.html">Examples</a></li>
</ul>
<li><a href="../xmldsig.html">XML Digital Signature</a></li>
<ul><li><a href="http://www.aleksey.com/xmlsec/xmldsig-verifier.html">Online Verifier</a></li></ul>
<li><a href="../xmlenc.html">XML Encryption</a></li>
<li><a href="../c14n.html">XML Canonicalization</a></li>
<li><a href="../bugs.html">Reporting Bugs</a></li>
<li><a href="http://www.aleksey.com/pipermail/xmlsec">Mailing list</a></li>
<li><a href="../related.html">Related</a></li>
<li><a href="../authors.html">Authors</a></li>
</ul>
<table width="100%">
<tr>
<td width="15"></td>
<td><a href="http://xmlsoft.org/"><img src="../images/libxml2-logo.png" alt="LibXML2" border="0"></a></td>
</tr>
<tr>
<td width="15"></td>
<td><a href="http://xmlsoft.org/XSLT"><img src="../images/libxslt-logo.png" alt="LibXSLT" border="0"></a></td>
</tr>
<tr>
<td width="15"></td>
<td><a href="http://www.openssl.org/"><img src="../images/openssl-logo.png" alt="OpenSSL" border="0"></a></td>
</tr>
<!--Links - start--><!--Links - end-->
</table>
</td>
<td valign="top"><table width="100%" valign="top"><tr><td valign="top" align="left" id="xmlsecContent">
<table width="100%" class="navigation" summary="Navigation header" cellpadding="2" cellspacing="2"><tr valign="middle">
<td><a accesskey="p" href="xmlsec-notes-verify-x509.html"><img src="left.png" width="16" height="16" border="0" alt="Prev"></a></td>
<td><a accesskey="u" href="xmlsec-notes.html"><img src="up.png" width="16" height="16" border="0" alt="Up"></a></td>
<td><a accesskey="h" href="index.html"><img src="home.png" width="16" height="16" border="0" alt="Home"></a></td>
<th width="100%" align="center">XML Security Library Reference Manual</th>
<td><a accesskey="n" href="xmlsec-notes-contexts.html"><img src="right.png" width="16" height="16" border="0" alt="Next"></a></td>
</tr></table>
<div class="CHAPTER">
<h1>
<a name="XMLSEC-NOTES-TRANSFORMS"></a>Transforms and transforms chain.</h1>
<p>XML Digital Signature and XML Encryption standards are
very flexible and provide an XML developer many different ways to
sign or encrypt any part (or even parts) of an XML document.
The key for such great flexibility is the "transforms" model.
Transform is defined as a method of pre-processing binary or XML data
before calculating digest or signature. XML Security Library extends
this definition and names "transform" any operation performed on
the data: reading data from an URI, xml parsing, xml transformation,
calculation digest, encrypting or decrypting. Each XML Security Library
transform provides at least one of the following callbacks:
</p>
<p></p>
<ul>
<li><p> <a href="xmlsec-transforms.html#XMLSECTRANSFORMPUSHBINMETHOD">push binary data</a>;
</p></li>
<li><p> <a href="xmlsec-transforms.html#XMLSECTRANSFORMPUSHXMLMETHOD">push xml data</a>;
</p></li>
<li><p> <a href="xmlsec-transforms.html#XMLSECTRANSFORMPOPBINMETHOD">pop binary data</a>;
</p></li>
<li><p> <a href="xmlsec-transforms.html#XMLSECTRANSFORMPOPXMLMETHOD">pop xml data</a>.
</p></li>
</ul>
<p>One additional <a href="xmlsec-transforms.html#XMLSECTRANSFORMEXECUTEMETHOD">execute</a>
callback was added to simplify the development and reduce code size.
This callback is used by default
implementations of the four external callbacks from the list above.
For example, most of the crypto transforms could be implemented by
just implementing one "execute" callback and using default push/pop
binary data callbacks. However, in some cases using push/pop callbacks
directly is more efficient.
</p>
<div class="FIGURE">
<a name="AEN610"></a><p><b>Figure 1. The XML Security Library transform.</b></p>
<p><img src="images/transform.png" align="CENTER"></p>
</div>
<p>XML Security Library constructs transforms chain according to the
signature/encryption template or signed/encrypted document.
If necessary, XML Security Library inserts XML parser or defaul
canonicalization to ensure that the output data type (binary or XML)
of previous transform matches the input of the next transform.
</p>
<p>The data are processed by pushing through or poping from the chain
depending on the transforms in the chain. For example, then binary
data chunk is pushed through a binary-to-binary transform, it
processes this chunk and pushes the result to the next transform
in the chain.
</p>
<div class="FIGURE">
<a name="AEN615"></a><p><b>Figure 2. Transforms chain created for <a href="http://www.w3.org/TR/xmldsig-core/#sec-Reference" target="_top"></a><a href="http://www.w3.org/TR/xmldsig-core/#sec-Reference" target="_top"></a><a href="http://www.w3.org/TR/xmldsig-core/#sec-Reference" target="_top"></a><a href="http://www.w3.org/TR/xmldsig-core/#sec-Reference" target="_top"></a><a href="http://www.w3.org/TR/xmldsig-core/#sec-Reference" target="_top"></a><a href="http://www.w3.org/TR/xmldsig-core/#sec-Reference" target="_top"></a><a href="http://www.w3.org/TR/xmldsig-core/#sec-Reference" target="_top"><dsig:Reference/></a> element processing.</b></p>
<p><img src="images/transforms-chain.png" align="CENTER"></p>
</div>
<p> </p>
<div class="EXAMPLE">
<a name="AEN626"></a><p><b>Example 1. Walking through transforms chain.</b></p>
<pre class="PROGRAMLISTING">TODO
</pre>
</div>
</div>
<table class="navigation" width="100%" summary="Navigation footer" cellpadding="2" cellspacing="2"><tr valign="middle">
<td align="left"><a accesskey="p" href="xmlsec-notes-verify-x509.html"><b><<< Verifing document signed with X509 certificates.</b></a></td>
<td align="right"><a accesskey="n" href="xmlsec-notes-contexts.html"><b>Using context objects. >>></b></a></td>
</tr></table>
</td></tr></table></td>
</tr></table></body>
</html>
|
