XML Security Library

LibXML2
LibXSLT
OpenSSL

Signing with X509 certificate.

sign3.c

/** 
 * XML Security Library example: Signing a file with a dynamicaly created template and an X509 certificate.
 * 
 * Signs a file using a dynamicaly created template, key from PEM file and
 * an X509 certificate. The signature has one reference with one enveloped 
 * transform to sign the whole document except the <dsig:Signature/> node 
 * itself. The key certificate is written in the <dsig:X509Data/> node.
 * 
 * This example was developed and tested with OpenSSL crypto library. The 
 * certificates management policies for another crypto library may break it.
 * 
 * Usage: 
 *      sign3 <xml-doc> <pem-key> 
 *
 * Example:
 *      ./sign3 sign3-doc.xml rsakey.pem rsacert.pem > sign3-res.xml
 *
 * The result signature could be validated using verify3 example:
 *      ./verify3 sign3-res.xml ca2cert.pem cacert.pem
 *
 * This is free software; see Copyright file in the source
 * distribution for preciese wording.
 * 
 * Copyright (C) 2002-2016 Aleksey Sanin <aleksey@aleksey.com>. All Rights Reserved.
 */
#include <stdlib.h>
#include <string.h>
#include <assert.h>

#include <libxml/tree.h>
#include <libxml/xmlmemory.h>
#include <libxml/parser.h>

#ifndef XMLSEC_NO_XSLT
#include <libxslt/xslt.h>
#include <libxslt/security.h>
#endif /* XMLSEC_NO_XSLT */

#include <xmlsec/xmlsec.h>
#include <xmlsec/xmltree.h>
#include <xmlsec/xmldsig.h>
#include <xmlsec/templates.h>
#include <xmlsec/crypto.h>

int sign_file(const char* xml_file, const char* key_file, const char* cert_file);

int 
main(int argc, char **argv) {
#ifndef XMLSEC_NO_XSLT
    xsltSecurityPrefsPtr xsltSecPrefs = NULL;
#endif /* XMLSEC_NO_XSLT */

    assert(argv);

    if(argc != 4) {
        fprintf(stderr, "Error: wrong number of arguments.\n");
        fprintf(stderr, "Usage: %s <xml-file> <key-file> <cert-file>\n", argv[0]);
        return(1);
    }

    /* Init libxml and libxslt libraries */
    xmlInitParser();
    LIBXML_TEST_VERSION
    xmlLoadExtDtdDefaultValue = XML_DETECT_IDS | XML_COMPLETE_ATTRS;
    xmlSubstituteEntitiesDefault(1);
#ifndef XMLSEC_NO_XSLT
    xmlIndentTreeOutput = 1; 
#endif /* XMLSEC_NO_XSLT */

    /* Init libxslt */
#ifndef XMLSEC_NO_XSLT
    /* disable everything */
    xsltSecPrefs = xsltNewSecurityPrefs(); 
    xsltSetSecurityPrefs(xsltSecPrefs,  XSLT_SECPREF_READ_FILE,        xsltSecurityForbid);
    xsltSetSecurityPrefs(xsltSecPrefs,  XSLT_SECPREF_WRITE_FILE,       xsltSecurityForbid);
    xsltSetSecurityPrefs(xsltSecPrefs,  XSLT_SECPREF_CREATE_DIRECTORY, xsltSecurityForbid);
    xsltSetSecurityPrefs(xsltSecPrefs,  XSLT_SECPREF_READ_NETWORK,     xsltSecurityForbid);
    xsltSetSecurityPrefs(xsltSecPrefs,  XSLT_SECPREF_WRITE_NETWORK,    xsltSecurityForbid);
    xsltSetDefaultSecurityPrefs(xsltSecPrefs); 
#endif /* XMLSEC_NO_XSLT */
                
    /* Init xmlsec library */
    if(xmlSecInit() < 0) {
        fprintf(stderr, "Error: xmlsec initialization failed.\n");
        return(-1);
    }

    /* Check loaded library version */
    if(xmlSecCheckVersion() != 1) {
        fprintf(stderr, "Error: loaded xmlsec library version is not compatible.\n");
        return(-1);
    }

    /* Load default crypto engine if we are supporting dynamic
     * loading for xmlsec-crypto libraries. Use the crypto library
     * name ("openssl", "nss", etc.) to load corresponding 
     * xmlsec-crypto library.
     */
#ifdef XMLSEC_CRYPTO_DYNAMIC_LOADING
    if(xmlSecCryptoDLLoadLibrary(NULL) < 0) {
        fprintf(stderr, "Error: unable to load default xmlsec-crypto library. Make sure\n"
                        "that you have it installed and check shared libraries path\n"
                        "(LD_LIBRARY_PATH) envornment variable.\n");
        return(-1);     
    }
#endif /* XMLSEC_CRYPTO_DYNAMIC_LOADING */

    /* Init crypto library */
    if(xmlSecCryptoAppInit(NULL) < 0) {
        fprintf(stderr, "Error: crypto initialization failed.\n");
        return(-1);
    }

    /* Init xmlsec-crypto library */
    if(xmlSecCryptoInit() < 0) {
        fprintf(stderr, "Error: xmlsec-crypto initialization failed.\n");
        return(-1);
    }

    if(sign_file(argv[1], argv[2], argv[3]) < 0) {
        return(-1);
    }    
    
    /* Shutdown xmlsec-crypto library */
    xmlSecCryptoShutdown();
    
    /* Shutdown crypto library */
    xmlSecCryptoAppShutdown();
    
    /* Shutdown xmlsec library */
    xmlSecShutdown();

    /* Shutdown libxslt/libxml */
#ifndef XMLSEC_NO_XSLT
    xsltFreeSecurityPrefs(xsltSecPrefs);
    xsltCleanupGlobals();            
#endif /* XMLSEC_NO_XSLT */
    xmlCleanupParser();
    
    return(0);
}

/** 
 * sign_file:
 * @xml_file:           the XML file name.
 * @key_file:           the PEM private key file name.
 * @cert_file:          the x509 certificate PEM file.
 *
 * Signs the @xml_file using private key from @key_file and dynamicaly
 * created enveloped signature template. The certificate from @cert_file
 * is placed in the <dsig:X509Data/> node.
 *
 * Returns 0 on success or a negative value if an error occurs.
 */
int 
sign_file(const char* xml_file, const char* key_file, const char* cert_file) {
    xmlDocPtr doc = NULL;
    xmlNodePtr signNode = NULL;
    xmlNodePtr refNode = NULL;
    xmlNodePtr keyInfoNode = NULL;
    xmlNodePtr x509DataNode = NULL;
    xmlSecDSigCtxPtr dsigCtx = NULL;
    int res = -1;
    
    assert(xml_file);
    assert(key_file);
    assert(cert_file);

    /* load doc file */
    doc = xmlParseFile(xml_file);
    if ((doc == NULL) || (xmlDocGetRootElement(doc) == NULL)){
        fprintf(stderr, "Error: unable to parse file \"%s\"\n", xml_file);
        goto done;      
    }
    
    /* create signature template for RSA-SHA1 enveloped signature */
    signNode = xmlSecTmplSignatureCreate(doc, xmlSecTransformExclC14NId,
                                         xmlSecTransformRsaSha1Id, NULL);
    if(signNode == NULL) {
        fprintf(stderr, "Error: failed to create signature template\n");
        goto done;              
    }

    /* add <dsig:Signature/> node to the doc */
    xmlAddChild(xmlDocGetRootElement(doc), signNode);
    
    /* add reference */
    refNode = xmlSecTmplSignatureAddReference(signNode, xmlSecTransformSha1Id,
                                        NULL, NULL, NULL);
    if(refNode == NULL) {
        fprintf(stderr, "Error: failed to add reference to signature template\n");
        goto done;              
    }

    /* add enveloped transform */
    if(xmlSecTmplReferenceAddTransform(refNode, xmlSecTransformEnvelopedId) == NULL) {
        fprintf(stderr, "Error: failed to add enveloped transform to reference\n");
        goto done;              
    }
    
    /* add <dsig:KeyInfo/> and <dsig:X509Data/> */
    keyInfoNode = xmlSecTmplSignatureEnsureKeyInfo(signNode, NULL);
    if(keyInfoNode == NULL) {
        fprintf(stderr, "Error: failed to add key info\n");
        goto done;              
    }
    
    x509DataNode = xmlSecTmplKeyInfoAddX509Data(keyInfoNode);
    if(x509DataNode == NULL) {
        fprintf(stderr, "Error: failed to add X509Data node\n");
        goto done;              
    }

    if(xmlSecTmplX509DataAddSubjectName(x509DataNode) == NULL) {
        fprintf(stderr, "Error: failed to add X509SubjectName node\n");
        goto done;
    }

    if(xmlSecTmplX509DataAddCertificate(x509DataNode) == NULL) {
        fprintf(stderr, "Error: failed to add X509Certificate node\n");
        goto done;
    }

    /* create signature context, we don't need keys manager in this example */
    dsigCtx = xmlSecDSigCtxCreate(NULL);
    if(dsigCtx == NULL) {
        fprintf(stderr,"Error: failed to create signature context\n");
        goto done;
    }

    /* load private key, assuming that there is not password */
    dsigCtx->signKey = xmlSecCryptoAppKeyLoad(key_file, xmlSecKeyDataFormatPem, NULL, NULL, NULL);
    if(dsigCtx->signKey == NULL) {
        fprintf(stderr,"Error: failed to load private pem key from \"%s\"\n", key_file);
        goto done;
    }
    
    /* load certificate and add to the key */
    if(xmlSecCryptoAppKeyCertLoad(dsigCtx->signKey, cert_file, xmlSecKeyDataFormatPem) < 0) {
        fprintf(stderr,"Error: failed to load pem certificate \"%s\"\n", cert_file);
        goto done;
    }

    /* set key name to the file name, this is just an example! */
    if(xmlSecKeySetName(dsigCtx->signKey, key_file) < 0) {
        fprintf(stderr,"Error: failed to set key name for key from \"%s\"\n", key_file);
        goto done;
    }

    /* sign the template */
    if(xmlSecDSigCtxSign(dsigCtx, signNode) < 0) {
        fprintf(stderr,"Error: signature failed\n");
        goto done;
    }
        
    /* print signed document to stdout */
    xmlDocDump(stdout, doc);
    
    /* success */
    res = 0;

done:    
    /* cleanup */
    if(dsigCtx != NULL) {
        xmlSecDSigCtxDestroy(dsigCtx);
    }
    
    if(doc != NULL) {
        xmlFreeDoc(doc); 
    }
    return(res);
}

sign3-doc.xml

<?xml version="1.0" encoding="UTF-8"?>
<!-- 
XML Security Library example: Original XML doc file for sign3 example. 
-->
<Envelope xmlns="urn:envelope">
  <Data>
	Hello, World!
  </Data>
</Envelope>

sign3-res.xml

<?xml version="1.0" encoding="UTF-8"?>
<!-- 
XML Security Library example: Original XML doc file for sign3 example. 
-->
<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>GnYgZdzPeXd/gPTJmQ506qmxWkd3VK1Y23kh5Qpq8y4LMNY+LJJeCWK5wpo/vufR
nIH/KUqvIvtk9nb2IjF5Uw==</SignatureValue>
<KeyInfo>
<X509Data>
<X509Certificate>MIIDpzCCA1GgAwIBAgIJAK+ii7kzrdqvMA0GCSqGSIb3DQEBBQUAMIGcMQswCQYD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</X509Certificate>
</X509Data>
</KeyInfo>
</Signature></Envelope>