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<br clear="all"><div class="SECT1">
<h1 class="SECT1"><a name="XMLSEC-CUSTOM-KEYS-MANAGER">Writing a custom keys manager.</a></h1>
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<h2 class="SECT2"><a name="XMLSEC-EXAMPLE-DECRYPT3">decrypt3.c</a></h2>
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<a name="AEN814"></a><pre class="PROGRAMLISTING">/**
* XML Security Library example: Decrypting an encrypted file using a custom keys manager.
*
* Decrypts encrypted XML file using a custom files based keys manager.
* We assume that key's name in <dsig:KeyName/> element is just
* key's file name in the current folder.
*
* Usage:
* ./decrypt3 <xml-enc>
*
* Example:
* ./decrypt3 encrypt1-res.xml
* ./decrypt3 encrypt2-res.xml
*
* This is free software; see Copyright file in the source
* distribution for preciese wording.
*
* Copyright (C) 2002-2003 Aleksey Sanin <aleksey@aleksey.com>
*/
#include <stdlib.h>
#include <string.h>
#include <ctype.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/xmlenc.h>
#include <xmlsec/crypto.h>
xmlSecKeyStoreId files_keys_store_get_klass(void);
xmlSecKeysMngrPtr create_files_keys_mngr(void);
int decrypt_file(xmlSecKeysMngrPtr mngr, const char* enc_file);
int
main(int argc, char **argv) {
xmlSecKeysMngrPtr mngr;
#ifndef XMLSEC_NO_XSLT
xsltSecurityPrefsPtr xsltSecPrefs = NULL;
#endif /* XMLSEC_NO_XSLT */
assert(argv);
if(argc != 2) {
fprintf(stderr, "Error: wrong number of arguments.\n");
fprintf(stderr, "Usage: %s <enc-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(BAD_CAST XMLSEC_CRYPTO) < 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);
}
/* create keys manager and load keys */
mngr = create_files_keys_mngr();
if(mngr == NULL) {
return(-1);
}
if(decrypt_file(mngr, argv[1]) < 0) {
xmlSecKeysMngrDestroy(mngr);
return(-1);
}
/* destroy keys manager */
xmlSecKeysMngrDestroy(mngr);
/* 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);
}
/**
* decrypt_file:
* @mngr: the pointer to keys manager.
* @enc_file: the encrypted XML file name.
*
* Decrypts the XML file #enc_file using DES key from #key_file and
* prints results to stdout.
*
* Returns 0 on success or a negative value if an error occurs.
*/
int
decrypt_file(xmlSecKeysMngrPtr mngr, const char* enc_file) {
xmlDocPtr doc = NULL;
xmlNodePtr node = NULL;
xmlSecEncCtxPtr encCtx = NULL;
int res = -1;
assert(mngr);
assert(enc_file);
/* load template */
doc = xmlParseFile(enc_file);
if ((doc == NULL) || (xmlDocGetRootElement(doc) == NULL)){
fprintf(stderr, "Error: unable to parse file \"%s\"\n", enc_file);
goto done;
}
/* find start node */
node = xmlSecFindNode(xmlDocGetRootElement(doc), xmlSecNodeEncryptedData, xmlSecEncNs);
if(node == NULL) {
fprintf(stderr, "Error: start node not found in \"%s\"\n", enc_file);
goto done;
}
/* create encryption context */
encCtx = xmlSecEncCtxCreate(mngr);
if(encCtx == NULL) {
fprintf(stderr,"Error: failed to create encryption context\n");
goto done;
}
/* decrypt the data */
if((xmlSecEncCtxDecrypt(encCtx, node) < 0) || (encCtx->result == NULL)) {
fprintf(stderr,"Error: decryption failed\n");
goto done;
}
/* print decrypted data to stdout */
if(encCtx->resultReplaced != 0) {
fprintf(stdout, "Decrypted XML data:\n");
xmlDocDump(stdout, doc);
} else {
fprintf(stdout, "Decrypted binary data (%d bytes):\n", xmlSecBufferGetSize(encCtx->result));
if(xmlSecBufferGetData(encCtx->result) != NULL) {
fwrite(xmlSecBufferGetData(encCtx->result),
1,
xmlSecBufferGetSize(encCtx->result),
stdout);
}
}
fprintf(stdout, "\n");
/* success */
res = 0;
done:
/* cleanup */
if(encCtx != NULL) {
xmlSecEncCtxDestroy(encCtx);
}
if(doc != NULL) {
xmlFreeDoc(doc);
}
return(res);
}
/**
* create_files_keys_mngr:
*
* Creates a files based keys manager: we assume that key name is
* the key file name,
*
* Returns pointer to newly created keys manager or NULL if an error occurs.
*/
xmlSecKeysMngrPtr
create_files_keys_mngr(void) {
xmlSecKeyStorePtr keysStore;
xmlSecKeysMngrPtr mngr;
/* create files based keys store */
keysStore = xmlSecKeyStoreCreate(files_keys_store_get_klass());
if(keysStore == NULL) {
fprintf(stderr, "Error: failed to create keys store.\n");
return(NULL);
}
/* create keys manager */
mngr = xmlSecKeysMngrCreate();
if(mngr == NULL) {
fprintf(stderr, "Error: failed to create keys manager.\n");
xmlSecKeyStoreDestroy(keysStore);
return(NULL);
}
/* add store to keys manager, from now on keys manager destroys the store if needed */
if(xmlSecKeysMngrAdoptKeysStore(mngr, keysStore) < 0) {
fprintf(stderr, "Error: failed to add keys store to keys manager.\n");
xmlSecKeyStoreDestroy(keysStore);
xmlSecKeysMngrDestroy(mngr);
return(NULL);
}
/* initialize crypto library specific data in keys manager */
if(xmlSecCryptoKeysMngrInit(mngr) < 0) {
fprintf(stderr, "Error: failed to initialize crypto data in keys manager.\n");
xmlSecKeysMngrDestroy(mngr);
return(NULL);
}
/* set the get key callback */
mngr->getKey = xmlSecKeysMngrGetKey;
return(mngr);
}
/****************************************************************************
*
* Files Keys Store: we assume that key's name (content of the
* <dsig:KeyName/> element is a name of the file with a key (in the
* current folder).
* Attention: this probably not a good solution for high traffic systems.
*
***************************************************************************/
static xmlSecKeyPtr files_keys_store_find_key (xmlSecKeyStorePtr store,
const xmlChar* name,
xmlSecKeyInfoCtxPtr keyInfoCtx);
static xmlSecKeyStoreKlass files_keys_store_klass = {
sizeof(xmlSecKeyStoreKlass),
sizeof(xmlSecKeyStore),
BAD_CAST "files-based-keys-store", /* const xmlChar* name; */
NULL, /* xmlSecKeyStoreInitializeMethod initialize; */
NULL, /* xmlSecKeyStoreFinalizeMethod finalize; */
files_keys_store_find_key, /* xmlSecKeyStoreFindKeyMethod findKey; */
/* reserved for the future */
NULL, /* void* reserved0; */
NULL, /* void* reserved1; */
};
/**
* files_keys_store_get_klass:
*
* The files based keys store klass: we assume that key name is the
* key file name,
*
* Returns files based keys store klass.
*/
xmlSecKeyStoreId
files_keys_store_get_klass(void) {
return(&files_keys_store_klass);
}
/**
* files_keys_store_find_key:
* @store: the pointer to simple keys store.
* @name: the desired key name.
* @keyInfoCtx: the pointer to <dsig:KeyInfo/> node processing context.
*
* Lookups key in the @store. The caller is responsible for destroying
* returned key with #xmlSecKeyDestroy function.
*
* Returns pointer to key or NULL if key not found or an error occurs.
*/
static xmlSecKeyPtr
files_keys_store_find_key(xmlSecKeyStorePtr store, const xmlChar* name, xmlSecKeyInfoCtxPtr keyInfoCtx) {
xmlSecKeyPtr key;
const xmlChar* p;
assert(store);
assert(keyInfoCtx);
/* it's possible to do not have the key name or desired key type
* but we could do nothing in this case */
if((name == NULL) || (keyInfoCtx->keyReq.keyId == xmlSecKeyDataIdUnknown)){
return(NULL);
}
/* we don't want to open files in a folder other than "current";
* to prevent it limit the characters in the key name to alpha/digit,
* '.', '-' or '_'.
*/
for(p = name; (*p) != '\0'; ++p) {
if(!isalnum((*p)) && ((*p) != '.') && ((*p) != '-') && ((*p) != '_')) {
return(NULL);
}
}
if((keyInfoCtx->keyReq.keyId == xmlSecKeyDataDsaId) || (keyInfoCtx->keyReq.keyId == xmlSecKeyDataRsaId)) {
/* load key from a pem file, if key is not found then it's an error (is it?) */
key = xmlSecCryptoAppKeyLoad(name, xmlSecKeyDataFormatPem, NULL, NULL, NULL);
if(key == NULL) {
fprintf(stderr,"Error: failed to load public pem key from \"%s\"\n", name);
return(NULL);
}
} else {
/* otherwise it's a binary key, if key is not found then it's an error (is it?) */
key = xmlSecKeyReadBinaryFile(keyInfoCtx->keyReq.keyId, name);
if(key == NULL) {
fprintf(stderr,"Error: failed to load key from binary file \"%s\"\n", name);
return(NULL);
}
}
/* set key name */
if(xmlSecKeySetName(key, name) < 0) {
fprintf(stderr,"Error: failed to set key name for key from \"%s\"\n", name);
xmlSecKeyDestroy(key);
return(NULL);
}
return(key);
}
</pre>
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