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xpath.c
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1 /*
2  * Copyright 2004-2021 the Pacemaker project contributors
3  *
4  * The version control history for this file may have further details.
5  *
6  * This source code is licensed under the GNU Lesser General Public License
7  * version 2.1 or later (LGPLv2.1+) WITHOUT ANY WARRANTY.
8  */
9 
10 #include <crm_internal.h>
11 #include <stdio.h>
12 #include <string.h>
13 #include <crm/msg_xml.h>
15 #include "crmcommon_private.h"
16 
17 /*
18  * From xpath2.c
19  *
20  * All the elements returned by an XPath query are pointers to
21  * elements from the tree *except* namespace nodes where the XPath
22  * semantic is different from the implementation in libxml2 tree.
23  * As a result when a returned node set is freed when
24  * xmlXPathFreeObject() is called, that routine must check the
25  * element type. But node from the returned set may have been removed
26  * by xmlNodeSetContent() resulting in access to freed data.
27  *
28  * This can be exercised by running
29  * valgrind xpath2 test3.xml '//discarded' discarded
30  *
31  * There is 2 ways around it:
32  * - make a copy of the pointers to the nodes from the result set
33  * then call xmlXPathFreeObject() and then modify the nodes
34  * or
35  * - remove the references from the node set, if they are not
36  namespace nodes, before calling xmlXPathFreeObject().
37  */
38 void
39 freeXpathObject(xmlXPathObjectPtr xpathObj)
40 {
41  int lpc, max = numXpathResults(xpathObj);
42 
43  if (xpathObj == NULL) {
44  return;
45  }
46 
47  for (lpc = 0; lpc < max; lpc++) {
48  if (xpathObj->nodesetval->nodeTab[lpc] && xpathObj->nodesetval->nodeTab[lpc]->type != XML_NAMESPACE_DECL) {
49  xpathObj->nodesetval->nodeTab[lpc] = NULL;
50  }
51  }
52 
53  /* _Now_ it's safe to free it */
54  xmlXPathFreeObject(xpathObj);
55 }
56 
57 xmlNode *
58 getXpathResult(xmlXPathObjectPtr xpathObj, int index)
59 {
60  xmlNode *match = NULL;
61  int max = numXpathResults(xpathObj);
62 
63  CRM_CHECK(index >= 0, return NULL);
64  CRM_CHECK(xpathObj != NULL, return NULL);
65 
66  if (index >= max) {
67  crm_err("Requested index %d of only %d items", index, max);
68  return NULL;
69 
70  } else if(xpathObj->nodesetval->nodeTab[index] == NULL) {
71  /* Previously requested */
72  return NULL;
73  }
74 
75  match = xpathObj->nodesetval->nodeTab[index];
76  CRM_CHECK(match != NULL, return NULL);
77 
78  if (xpathObj->nodesetval->nodeTab[index]->type != XML_NAMESPACE_DECL) {
79  /* See the comment for freeXpathObject() */
80  xpathObj->nodesetval->nodeTab[index] = NULL;
81  }
82 
83  if (match->type == XML_DOCUMENT_NODE) {
84  /* Will happen if section = '/' */
85  match = match->children;
86 
87  } else if (match->type != XML_ELEMENT_NODE
88  && match->parent && match->parent->type == XML_ELEMENT_NODE) {
89  /* Return the parent instead */
90  match = match->parent;
91 
92  } else if (match->type != XML_ELEMENT_NODE) {
93  /* We only support searching nodes */
94  crm_err("We only support %d not %d", XML_ELEMENT_NODE, match->type);
95  match = NULL;
96  }
97  return match;
98 }
99 
100 void
101 dedupXpathResults(xmlXPathObjectPtr xpathObj)
102 {
103  int lpc, max = numXpathResults(xpathObj);
104 
105  if (xpathObj == NULL) {
106  return;
107  }
108 
109  for (lpc = 0; lpc < max; lpc++) {
110  xmlNode *xml = NULL;
111  gboolean dedup = FALSE;
112 
113  if (xpathObj->nodesetval->nodeTab[lpc] == NULL) {
114  continue;
115  }
116 
117  xml = xpathObj->nodesetval->nodeTab[lpc]->parent;
118 
119  for (; xml; xml = xml->parent) {
120  int lpc2 = 0;
121 
122  for (lpc2 = 0; lpc2 < max; lpc2++) {
123  if (xpathObj->nodesetval->nodeTab[lpc2] == xml) {
124  xpathObj->nodesetval->nodeTab[lpc] = NULL;
125  dedup = TRUE;
126  break;
127  }
128  }
129 
130  if (dedup) {
131  break;
132  }
133  }
134  }
135 }
136 
137 /* the caller needs to check if the result contains a xmlDocPtr or xmlNodePtr */
138 xmlXPathObjectPtr
139 xpath_search(xmlNode * xml_top, const char *path)
140 {
141  xmlDocPtr doc = NULL;
142  xmlXPathObjectPtr xpathObj = NULL;
143  xmlXPathContextPtr xpathCtx = NULL;
144  const xmlChar *xpathExpr = (pcmkXmlStr) path;
145 
146  CRM_CHECK(path != NULL, return NULL);
147  CRM_CHECK(xml_top != NULL, return NULL);
148  CRM_CHECK(strlen(path) > 0, return NULL);
149 
150  doc = getDocPtr(xml_top);
151 
152  xpathCtx = xmlXPathNewContext(doc);
153  CRM_ASSERT(xpathCtx != NULL);
154 
155  xpathObj = xmlXPathEvalExpression(xpathExpr, xpathCtx);
156  xmlXPathFreeContext(xpathCtx);
157  return xpathObj;
158 }
159 
172 void
173 crm_foreach_xpath_result(xmlNode *xml, const char *xpath,
174  void (*helper)(xmlNode*, void*), void *user_data)
175 {
176  xmlXPathObjectPtr xpathObj = xpath_search(xml, xpath);
177  int nresults = numXpathResults(xpathObj);
178  int i;
179 
180  for (i = 0; i < nresults; i++) {
181  xmlNode *result = getXpathResult(xpathObj, i);
182 
183  CRM_LOG_ASSERT(result != NULL);
184  if (result) {
185  (*helper)(result, user_data);
186  }
187  }
188  freeXpathObject(xpathObj);
189 }
190 
191 xmlNode *
192 get_xpath_object_relative(const char *xpath, xmlNode * xml_obj, int error_level)
193 {
194  xmlNode *result = NULL;
195  char *xpath_full = NULL;
196  char *xpath_prefix = NULL;
197 
198  if (xml_obj == NULL || xpath == NULL) {
199  return NULL;
200  }
201 
202  xpath_prefix = (char *)xmlGetNodePath(xml_obj);
203 
204  xpath_full = crm_strdup_printf("%s%s", xpath_prefix, xpath);
205 
206  result = get_xpath_object(xpath_full, xml_obj, error_level);
207 
208  free(xpath_prefix);
209  free(xpath_full);
210  return result;
211 }
212 
213 xmlNode *
214 get_xpath_object(const char *xpath, xmlNode * xml_obj, int error_level)
215 {
216  int max;
217  xmlNode *result = NULL;
218  xmlXPathObjectPtr xpathObj = NULL;
219  char *nodePath = NULL;
220  char *matchNodePath = NULL;
221 
222  if (xpath == NULL) {
223  return xml_obj; /* or return NULL? */
224  }
225 
226  xpathObj = xpath_search(xml_obj, xpath);
227  nodePath = (char *)xmlGetNodePath(xml_obj);
228  max = numXpathResults(xpathObj);
229 
230  if (max < 1) {
231  if (error_level < LOG_NEVER) {
232  do_crm_log(error_level, "No match for %s in %s",
233  xpath, crm_str(nodePath));
234  crm_log_xml_explicit(xml_obj, "Unexpected Input");
235  }
236 
237  } else if (max > 1) {
238  if (error_level < LOG_NEVER) {
239  int lpc = 0;
240 
241  do_crm_log(error_level, "Too many matches for %s in %s",
242  xpath, crm_str(nodePath));
243 
244  for (lpc = 0; lpc < max; lpc++) {
245  xmlNode *match = getXpathResult(xpathObj, lpc);
246 
247  CRM_LOG_ASSERT(match != NULL);
248  if (match != NULL) {
249  matchNodePath = (char *) xmlGetNodePath(match);
250  do_crm_log(error_level, "%s[%d] = %s",
251  xpath, lpc, crm_str(matchNodePath));
252  free(matchNodePath);
253  }
254  }
255  crm_log_xml_explicit(xml_obj, "Bad Input");
256  }
257 
258  } else {
259  result = getXpathResult(xpathObj, 0);
260  }
261 
262  freeXpathObject(xpathObj);
263  free(nodePath);
264 
265  return result;
266 }
267 
268 int
269 pcmk__element_xpath(const char *prefix, xmlNode *xml, char *buffer,
270  int offset, size_t buffer_size)
271 {
272  const char *id = ID(xml);
273 
274  if(offset == 0 && prefix == NULL && xml->parent) {
275  offset = pcmk__element_xpath(NULL, xml->parent, buffer, offset,
276  buffer_size);
277  }
278 
279  if(id) {
280  offset += snprintf(buffer + offset, buffer_size - offset,
281  "/%s[@id='%s']", (const char *) xml->name, id);
282  } else if(xml->name) {
283  offset += snprintf(buffer + offset, buffer_size - offset,
284  "/%s", (const char *) xml->name);
285  }
286 
287  return offset;
288 }
289 
290 char *
291 xml_get_path(xmlNode *xml)
292 {
293  int offset = 0;
294  char buffer[PCMK__BUFFER_SIZE];
295 
296  if (pcmk__element_xpath(NULL, xml, buffer, offset, sizeof(buffer)) > 0) {
297  return strdup(buffer);
298  }
299  return NULL;
300 }
301 
302 char *
303 pcmk__xpath_node_id(const char *xpath, const char *node)
304 {
305  char *retval = NULL;
306  char *patt = NULL;
307  char *start = NULL;
308  char *end = NULL;
309 
310  if (node == NULL || xpath == NULL) {
311  return retval;
312  }
313 
314  patt = crm_strdup_printf("/%s[@id=", node);
315  start = strstr(xpath, patt);
316 
317  if (!start) {
318  free(patt);
319  return retval;
320  }
321 
322  start += strlen(patt);
323  start++;
324 
325  end = strstr(start, "\'");
326  CRM_ASSERT(end);
327  retval = strndup(start, end-start);
328 
329  free(patt);
330  return retval;
331 }
#define CRM_CHECK(expr, failure_action)
Definition: logging.h:218
xmlNode * get_xpath_object_relative(const char *xpath, xmlNode *xml_obj, int error_level)
Definition: xpath.c:192
G_GNUC_INTERNAL int pcmk__element_xpath(const char *prefix, xmlNode *xml, char *buffer, int offset, size_t buffer_size)
Definition: xpath.c:269
#define CRM_LOG_ASSERT(expr)
Definition: logging.h:202
void dedupXpathResults(xmlXPathObjectPtr xpathObj)
Definition: xpath.c:101
char * pcmk__xpath_node_id(const char *xpath, const char *node)
Definition: xpath.c:303
#define LOG_NEVER
Definition: logging.h:46
xmlNode * get_xpath_object(const char *xpath, xmlNode *xml_obj, int error_level)
Definition: xpath.c:214
char * strndup(const char *str, size_t len)
xmlDoc * getDocPtr(xmlNode *node)
Definition: xml.c:658
#define do_crm_log(level, fmt, args...)
Log a message.
Definition: logging.h:159
#define crm_log_xml_explicit(xml, text)
Definition: logging.h:366
char * crm_strdup_printf(char const *format,...) G_GNUC_PRINTF(1
const xmlChar * pcmkXmlStr
Definition: xml.h:51
#define PCMK__BUFFER_SIZE
#define crm_err(fmt, args...)
Definition: logging.h:350
#define CRM_ASSERT(expr)
Definition: results.h:42
xmlXPathObjectPtr xpath_search(xmlNode *xml_top, const char *path)
Definition: xpath.c:139
xmlNode * getXpathResult(xmlXPathObjectPtr xpathObj, int index)
Definition: xpath.c:58
char * xml_get_path(xmlNode *xml)
Definition: xpath.c:291
#define crm_str(x)
Definition: logging.h:376
void crm_foreach_xpath_result(xmlNode *xml, const char *xpath, void(*helper)(xmlNode *, void *), void *user_data)
Run a supplied function for each result of an xpath search.
Definition: xpath.c:173
#define ID(x)
Definition: msg_xml.h:456
void freeXpathObject(xmlXPathObjectPtr xpathObj)
Definition: xpath.c:39