/**
 * 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 using "ID" attribute
 * of the node to be signed. 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:
 *      sign4 <xml-doc> <id-attribute-to-sign> <pem-key-file> <pem-cert-file>
 *
 * Example:
 *      ./sign4 sign4-doc.xml "data" rsakey.pem rsacert.pem > sign4-res.xml
 *
 * The result signature could be validated using verify3 example:
 *      ./verify3 sign4-res.xml ca2cert.pem cacert.pem
 *
 * This is free software; see the Copyright file in the source
 * distribution for precise wording.
 *
 * Copyright (C) 2002-2024 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* id_attr, 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 != 5) {
        fprintf(stderr, "Error: wrong number of arguments.\n");
        fprintf(stderr, "Usage: %s <xml-file> <id-attr> <key-file> <cert-file>\n", argv[0]);
        return(1);
    }

    /* Init libxml and libxslt libraries */
    xmlInitParser();
    LIBXML_TEST_VERSION

    /* 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 and/or LTDL_LIBRARY_PATH) environment variables.\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], argv[4]) < 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.
 * @id_attr:            the ID attribute of the node to sign.
 * @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* id_attr, 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;
    char uri[1024];
    const xmlChar* id_attributes[] = { BAD_CAST "id", BAD_CAST "ID", NULL };
    int res = -1;

    assert(xml_file);
    assert(id_attr);
    assert(key_file);
    assert(cert_file);

    /* load doc file */
    doc = xmlReadFile(xml_file, NULL, XML_PARSE_PEDANTIC | XML_PARSE_NONET | XML_PARSE_NOENT);
    if ((doc == NULL) || (xmlDocGetRootElement(doc) == NULL)){
        fprintf(stderr, "Error: unable to parse file \"%s\"\n", xml_file);
        goto done;
    }

    /* create signature template for RSA-SHA256 signature */
    signNode = xmlSecTmplSignatureCreate(doc, xmlSecTransformExclC14NId, xmlSecTransformRsaSha256Id, 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 */
    if (strlen(id_attr) + 2 > sizeof(uri)) {
        fprintf(stderr, "Error: id attribute is too long\n");
        goto done;
    }
    sprintf(uri, "#%s", id_attr);

    refNode = xmlSecTmplSignatureAddReference(signNode, xmlSecTransformSha256Id,
                                        NULL, BAD_CAST uri, NULL);
    if(refNode == NULL) {
        fprintf(stderr, "Error: failed to add reference to signature template\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;
    }

    /* add ID attributes to the doc context since we don't have DTDs */
    xmlSecAddIDs(doc, NULL, id_attributes);

    /* 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 = xmlSecCryptoAppKeyLoadEx(key_file, xmlSecKeyDataTypePrivate, 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, BAD_CAST 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);
}
