/*

 * Copyright (C) 2016 The Android Open Source Project

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *      https://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

#include <assert.h>

#include <limits.h> // for INT_MAX

#include <stdint.h>

#include <string.h>

#include "expat.h"

#include "siphash.h"

// Macros to convert preprocessor macros to string literals. See

// https://gcc.gnu.org/onlinedocs/gcc-3.4.3/cpp/Stringification.html

#define xstr(s) str(s)

#define str(s) #s

// The encoder type that we wish to fuzz should come from the compile-time

// definition `ENCODING_FOR_FUZZING`. This allows us to have a separate fuzzer

// binary for

#ifndef ENCODING_FOR_FUZZING

#  error "ENCODING_FOR_FUZZING was not provided to this fuzz target."

#endif

// 16-byte deterministic hash key.

static unsigned char hash_key[16] = "FUZZING IS FUN!";

static void XMLCALL

start(void *userData, const XML_Char *name, const XML_Char **atts) {

  (void)userData;

  (void)name;

  (void)atts;

}

static void XMLCALL

end(void *userData, const XML_Char *name) {

  (void)userData;

  (void)name;

}

static void XMLCALL

may_stop_character_handler(void *userData, const XML_Char *s, int len) {

  XML_Parser parser = (XML_Parser)userData;

  if (len > 1 && s[0] == 's') {

    XML_StopParser(parser, s[1] == 'r' ? XML_FALSE : XML_TRUE);

  }

}

static void

ParseOneInput(XML_Parser p, const uint8_t *data, size_t size) {

  // Set the hash salt using siphash to generate a deterministic hash.

  struct sipkey *key = sip_keyof(hash_key);

  XML_SetHashSalt(p, (unsigned long)siphash24(data, size, key));

  (void)sip24_valid;

  XML_SetUserData(p, p);

  XML_SetElementHandler(p, start, end);

  XML_SetCharacterDataHandler(p, may_stop_character_handler);

  assert(size <= INT_MAX);

  void *buf = XML_GetBuffer(p, (int)size);

  assert(buf);

  memcpy(buf, data, size);

  XML_ParseBuffer(p, (int)size, 0);

  buf = XML_GetBuffer(p, (int)size);

  if (buf == NULL) {

    return;

  }

  memcpy(buf, data, size);

  if (XML_ParseBuffer(p, (int)size, 1) == XML_STATUS_ERROR) {

    XML_ErrorString(XML_GetErrorCode(p));

  }

  XML_GetCurrentLineNumber(p);

  if (size % 2) {

    XML_ParserReset(p, NULL);

  }

}

int

LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {

  if (size == 0)

    return 0;

  XML_Parser parentParser = XML_ParserCreate(xstr(ENCODING_FOR_FUZZING));

  assert(parentParser);

  ParseOneInput(parentParser, data, size);

  // not freed yet, but used later and freed then

  XML_Parser namespaceParser = XML_ParserCreateNS(NULL, '!');

  assert(namespaceParser);

  ParseOneInput(namespaceParser, data, size);

  XML_ParserFree(namespaceParser);

  XML_Parser externalEntityParser

      = XML_ExternalEntityParserCreate(parentParser, "e1", NULL);

  if (externalEntityParser != NULL) {

    ParseOneInput(externalEntityParser, data, size);

    XML_ParserFree(externalEntityParser);

  }

  XML_Parser externalDtdParser

      = XML_ExternalEntityParserCreate(parentParser, NULL, NULL);

  if (externalDtdParser != NULL) {

    ParseOneInput(externalDtdParser, data, size);

    XML_ParserFree(externalDtdParser);

  }

  // finally frees this parser which served as parent

  XML_ParserFree(parentParser);

  return 0;

}