kc3-lang/libxml2/fuzz/valid.c

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• Hash : c6c6d8af
  Author :
  Date : 2024-12-11T16:24:23
  

  fuzz: Mutate fuzz data chunks separately
  
  Implement a custom mutator that takes a list of fixed-size chunks which
  are mutated with a given probability. This makes sure that values like
  parser options or failure position are mutated regularly even as the
  fuzz data grows large. Values can also be adjusted temporarily to make
  the fuzzer focus on failure injection, for example.
  
  Thanks to David Kilzer for the idea.
  

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• fuzz/valid.c

• /*
   * valid.c: a libFuzzer target to test DTD validation.
   *
   * See Copyright for the status of this software.
   */
  
  #include <libxml/catalog.h>
  #include <libxml/parser.h>
  #include <libxml/tree.h>
  #include <libxml/xmlerror.h>
  #include "fuzz.h"
  
  int
  LLVMFuzzerInitialize(int *argc ATTRIBUTE_UNUSED,
                       char ***argv ATTRIBUTE_UNUSED) {
      xmlFuzzMemSetup();
      xmlInitParser();
  #ifdef LIBXML_CATALOG_ENABLED
      xmlInitializeCatalog();
      xmlCatalogSetDefaults(XML_CATA_ALLOW_NONE);
  #endif
  
      return 0;
  }
  
  int
  LLVMFuzzerTestOneInput(const char *data, size_t size) {
      xmlParserCtxtPtr ctxt;
      xmlDocPtr doc;
      const char *docBuffer, *docUrl;
      size_t failurePos, docSize;
      int opts;
  
      xmlFuzzDataInit(data, size);
      opts = (int) xmlFuzzReadInt(4);
      opts |= XML_PARSE_DTDVALID;
      failurePos = xmlFuzzReadInt(4) % (size + 100);
  
      xmlFuzzReadEntities();
      docBuffer = xmlFuzzMainEntity(&docSize);
      docUrl = xmlFuzzMainUrl();
      if (docBuffer == NULL)
          goto exit;
  
      /* Pull parser */
  
      xmlFuzzInjectFailure(failurePos);
      ctxt = xmlNewParserCtxt();
      if (ctxt != NULL) {
          xmlCtxtSetErrorHandler(ctxt, xmlFuzzSErrorFunc, NULL);
          xmlCtxtSetResourceLoader(ctxt, xmlFuzzResourceLoader, NULL);
          doc = xmlCtxtReadMemory(ctxt, docBuffer, docSize, docUrl, NULL, opts);
          xmlFuzzCheckFailureReport("xmlCtxtReadMemory",
                                    ctxt->errNo == XML_ERR_NO_MEMORY,
                                    ctxt->errNo == XML_IO_EIO);
          xmlFreeDoc(doc);
          xmlFreeParserCtxt(ctxt);
      }
  
      /* Post validation */
  
      xmlFuzzInjectFailure(failurePos);
      ctxt = xmlNewParserCtxt();
      if (ctxt != NULL) {
          xmlCtxtSetErrorHandler(ctxt, xmlFuzzSErrorFunc, NULL);
          xmlCtxtSetResourceLoader(ctxt, xmlFuzzResourceLoader, NULL);
          doc = xmlCtxtReadMemory(ctxt, docBuffer, docSize, docUrl, NULL,
                                  opts & ~XML_PARSE_DTDVALID);
          xmlFuzzCheckFailureReport("xmlCtxtReadMemory",
                  doc == NULL && ctxt->errNo == XML_ERR_NO_MEMORY,
                  doc == NULL && ctxt->errNo == XML_IO_EIO);
          if (doc != NULL) {
              int valid = xmlCtxtValidateDocument(ctxt, doc);
  
              xmlFuzzCheckFailureReport("xmlCtxtValidateDocument",
                      !valid && ctxt->errNo == XML_ERR_NO_MEMORY,
                      !valid && ctxt->errNo == XML_IO_EIO);
          }
          xmlFreeDoc(doc);
          xmlFreeParserCtxt(ctxt);
      }
  
      /* Push parser */
  
  #ifdef LIBXML_PUSH_ENABLED
      {
          static const size_t maxChunkSize = 128;
          size_t consumed, chunkSize;
  
          xmlFuzzInjectFailure(failurePos);
          /*
           * FIXME: xmlCreatePushParserCtxt can still report OOM errors
           * to stderr.
           */
          xmlSetGenericErrorFunc(NULL, xmlFuzzErrorFunc);
          ctxt = xmlCreatePushParserCtxt(NULL, NULL, NULL, 0, docUrl);
          xmlSetGenericErrorFunc(NULL, NULL);
          if (ctxt != NULL) {
              xmlCtxtSetErrorHandler(ctxt, xmlFuzzSErrorFunc, NULL);
              xmlCtxtSetResourceLoader(ctxt, xmlFuzzResourceLoader, NULL);
              xmlCtxtUseOptions(ctxt, opts);
  
              for (consumed = 0; consumed < docSize; consumed += chunkSize) {
                  chunkSize = docSize - consumed;
                  if (chunkSize > maxChunkSize)
                      chunkSize = maxChunkSize;
                  xmlParseChunk(ctxt, docBuffer + consumed, chunkSize, 0);
              }
  
              xmlParseChunk(ctxt, NULL, 0, 1);
              xmlFuzzCheckFailureReport("xmlParseChunk",
                                        ctxt->errNo == XML_ERR_NO_MEMORY,
                                        ctxt->errNo == XML_IO_EIO);
              xmlFreeDoc(ctxt->myDoc);
              xmlFreeParserCtxt(ctxt);
          }
      }
  #endif
  
  exit:
      xmlFuzzInjectFailure(0);
      xmlFuzzDataCleanup();
      xmlResetLastError();
      return(0);
  }
  
  size_t
  LLVMFuzzerCustomMutator(char *data, size_t size, size_t maxSize,
                          unsigned seed) {
      static const xmlFuzzChunkDesc chunks[] = {
          { 4, XML_FUZZ_PROB_ONE / 10 }, /* opts */
          { 4, XML_FUZZ_PROB_ONE / 10 }, /* failurePos */
          { 0, 0 }
      };
  
      return xmlFuzzMutateChunks(chunks, data, size, maxSize, seed,
                                 LLVMFuzzerMutate);
  }
  
  

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