1  /*
       2   * Copyright (C) 2016 The Android Open Source Project
       3   *
       4   * Licensed under the Apache License, Version 2.0 (the "License");
       5   * you may not use this file except in compliance with the License.
       6   * You may obtain a copy of the License at
       7   *
       8   *      http://www.apache.org/licenses/LICENSE-2.0
       9   *
      10   * Unless required by applicable law or agreed to in writing, software
      11   * distributed under the License is distributed on an "AS IS" BASIS,
      12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      13   * See the License for the specific language governing permissions and
      14   * limitations under the License.
      15   */
      16  
      17  #include <assert.h>
      18  #include <stdint.h>
      19  #include <string.h>
      20  
      21  #include "expat.h"
      22  #include "siphash.h"
      23  
      24  // Macros to convert preprocessor macros to string literals. See
      25  // https://gcc.gnu.org/onlinedocs/gcc-3.4.3/cpp/Stringification.html
      26  #define xstr(s) str(s)
      27  #define str(s) #s
      28  
      29  // The encoder type that we wish to fuzz should come from the compile-time
      30  // definition `ENCODING_FOR_FUZZING`. This allows us to have a separate fuzzer
      31  // binary for
      32  #ifndef ENCODING_FOR_FUZZING
      33  #  error "ENCODING_FOR_FUZZING was not provided to this fuzz target."
      34  #endif
      35  
      36  // 16-byte deterministic hash key.
      37  static unsigned char hash_key[16] = "FUZZING IS FUN!";
      38  
      39  static void XMLCALL
      40  start(void *userData, const XML_Char *name, const XML_Char **atts) {
      41    (void)userData;
      42    (void)name;
      43    (void)atts;
      44  }
      45  static void XMLCALL
      46  end(void *userData, const XML_Char *name) {
      47    (void)userData;
      48    (void)name;
      49  }
      50  
      51  int
      52  LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
      53    if (size == 0)
      54      return 0;
      55  
      56    XML_Parser p = XML_ParserCreate(xstr(ENCODING_FOR_FUZZING));
      57    assert(p);
      58    XML_SetElementHandler(p, start, end);
      59  
      60    // Set the hash salt using siphash to generate a deterministic hash.
      61    struct sipkey *key = sip_keyof(hash_key);
      62    XML_SetHashSalt(p, (unsigned long)siphash24(data, size, key));
      63  
      64    void *buf = XML_GetBuffer(p, size);
      65    assert(buf);
      66  
      67    memcpy(buf, data, size);
      68    XML_ParseBuffer(p, size, size == 0);
      69    XML_ParserFree(p);
      70    return 0;
      71  }