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/*
* This file is part of LibEuFin.
* Copyright (C) 2024 Taler Systems S.A.
* LibEuFin is free software; you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation; either version 3, or
* (at your option) any later version.
* LibEuFin is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General
* Public License for more details.
* You should have received a copy of the GNU Affero General Public
* License along with LibEuFin; see the file COPYING. If not, see
* <http://www.gnu.org/licenses/>
*/
package tech.libeufin.nexus
import org.w3c.dom.Document
import org.w3c.dom.Node
import org.w3c.dom.NodeList
import org.xml.sax.InputSource
import java.io.ByteArrayOutputStream
import java.io.InputStream
import java.security.PrivateKey
import java.security.PublicKey
import javax.xml.crypto.*
import javax.xml.crypto.dom.DOMURIReference
import javax.xml.crypto.dsig.*
import javax.xml.crypto.dsig.dom.DOMSignContext
import javax.xml.crypto.dsig.dom.DOMValidateContext
import javax.xml.crypto.dsig.spec.C14NMethodParameterSpec
import javax.xml.crypto.dsig.spec.TransformParameterSpec
import javax.xml.parsers.DocumentBuilderFactory
import javax.xml.transform.OutputKeys
import javax.xml.transform.TransformerFactory
import javax.xml.transform.dom.DOMSource
import javax.xml.transform.stream.StreamResult
import javax.xml.xpath.XPath
import javax.xml.xpath.XPathConstants
import javax.xml.xpath.XPathFactory
/**
* This URI dereferencer allows handling the resource reference used for
* XML signatures in EBICS.
*/
private class EbicsSigUriDereferencer : URIDereferencer {
override fun dereference(myRef: URIReference?, myCtx: XMLCryptoContext?): Data {
if (myRef !is DOMURIReference)
throw Exception("invalid type")
if (myRef.uri != "#xpointer(//*[@authenticate='true'])")
throw Exception("invalid EBICS XML signature URI: '${myRef.uri}'")
val xp: XPath = XPathFactory.newInstance().newXPath()
val nodeSet = xp.compile("//*[@authenticate='true']/descendant-or-self::node()").evaluate(
myRef.here.ownerDocument, XPathConstants.NODESET
)
if (nodeSet !is NodeList)
throw Exception("invalid type")
if (nodeSet.length <= 0) {
throw Exception("no nodes to sign")
}
val nodeList = ArrayList<Node>()
for (i in 0 until nodeSet.length) {
val node = nodeSet.item(i)
nodeList.add(node)
}
return NodeSetData { nodeList.iterator() }
}
}
/**
* Helpers for dealing with XML in EBICS.
*/
object XMLUtil {
fun convertDomToBytes(document: Document): ByteArray {
val w = ByteArrayOutputStream()
val transformer = TransformerFactory.newInstance().newTransformer()
transformer.setOutputProperty(OutputKeys.STANDALONE, "yes")
transformer.transform(DOMSource(document), StreamResult(w))
return w.toByteArray()
}
/** Parse [xml] into a XML DOM */
fun parseIntoDom(xml: InputStream): Document {
val factory = DocumentBuilderFactory.newInstance().apply {
isNamespaceAware = true
}
val builder = factory.newDocumentBuilder()
return xml.use {
builder.parse(InputSource(it))
}
}
/**
* Sign an EBICS document with the authentication and identity signature.
*/
fun signEbicsDocument(
doc: Document,
signingPriv: PrivateKey,
schema: String
) {
val authSigNode = XPathFactory.newInstance().newXPath()
.evaluate("/*[1]/urn:org:ebics:$schema:AuthSignature", doc, XPathConstants.NODE)
if (authSigNode !is Node)
throw java.lang.Exception("no AuthSignature")
val fac = XMLSignatureFactory.getInstance("DOM")
val c14n = fac.newTransform(CanonicalizationMethod.INCLUSIVE, null as TransformParameterSpec?)
val ref: Reference =
fac.newReference(
"#xpointer(//*[@authenticate='true'])",
fac.newDigestMethod(DigestMethod.SHA256, null),
listOf(c14n),
null,
null
)
val canon: CanonicalizationMethod =
fac.newCanonicalizationMethod(CanonicalizationMethod.INCLUSIVE, null as C14NMethodParameterSpec?)
val signatureMethod = fac.newSignatureMethod("http://www.w3.org/2001/04/xmldsig-more#rsa-sha256", null)
val si: SignedInfo = fac.newSignedInfo(canon, signatureMethod, listOf(ref))
val sig: XMLSignature = fac.newXMLSignature(si, null)
val dsc = DOMSignContext(signingPriv, authSigNode)
dsc.defaultNamespacePrefix = "ds"
dsc.uriDereferencer = EbicsSigUriDereferencer()
dsc.setProperty("javax.xml.crypto.dsig.cacheReference", true)
sig.sign(dsc)
val innerSig = authSigNode.firstChild
while (innerSig.hasChildNodes()) {
authSigNode.appendChild(innerSig.firstChild)
}
authSigNode.removeChild(innerSig)
}
fun verifyEbicsDocument(
doc: Document,
signingPub: PublicKey,
schema: String
): Boolean {
val doc2: Document = doc.cloneNode(true) as Document
val authSigNode = XPathFactory.newInstance().newXPath()
.evaluate("/*[1]/urn:org:ebics:$schema:AuthSignature", doc2, XPathConstants.NODE)
if (authSigNode !is Node)
throw java.lang.Exception("no AuthSignature")
val sigEl = doc2.createElementNS("http://www.w3.org/2000/09/xmldsig#", "ds:Signature")
authSigNode.parentNode.insertBefore(sigEl, authSigNode)
while (authSigNode.hasChildNodes()) {
sigEl.appendChild(authSigNode.firstChild)
}
authSigNode.parentNode.removeChild(authSigNode)
val fac = XMLSignatureFactory.getInstance("DOM")
val dvc = DOMValidateContext(signingPub, sigEl)
dvc.setProperty("javax.xml.crypto.dsig.cacheReference", true)
dvc.uriDereferencer = EbicsSigUriDereferencer()
val sig = fac.unmarshalXMLSignature(dvc)
// FIXME: check that parameters are okay!
val valResult = sig.validate(dvc)
sig.signedInfo.references[0].validate(dvc)
return valResult
}
}
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