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 20 #include "expat.h" 21 #include "siphash.h" 22 23 // Macros to convert preprocessor macros to string literals. See 24 // https://gcc.gnu.org/onlinedocs/gcc-3.4.3/cpp/Stringification.html 25 #define xstr(s) str(s) 26 #define str(s) #s 27 28 // The encoder type that we wish to fuzz should come from the compile-time 29 // definition `ENCODING_FOR_FUZZING`. This allows us to have a separate fuzzer 30 // binary for 31 #ifndef ENCODING_FOR_FUZZING 32 # error "ENCODING_FOR_FUZZING was not provided to this fuzz target." 33 #endif 34 35 // 16-byte deterministic hash key. 36 static unsigned char hash_key[16] = "FUZZING IS FUN!"; 37 38 static void XMLCALL 39 start(void *userData, const XML_Char *name, const XML_Char **atts) { 40 (void)userData; 41 (void)name; 42 (void)atts; 43 } 44 static void XMLCALL 45 end(void *userData, const XML_Char *name) { 46 (void)userData; 47 (void)name; 48 } 49 50 static void XMLCALL 51 may_stop_character_handler(void *userData, const XML_Char *s, int len) { 52 XML_Parser parser = (XML_Parser)userData; 53 if (len > 1 && s[0] == 's') { 54 XML_StopParser(parser, s[1] == 'r' ? XML_FALSE : XML_TRUE); 55 } 56 } 57 58 static void 59 ParseOneInput(XML_Parser p, const uint8_t *data, size_t size) { 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 (void)sip24_valid; 64 65 XML_SetUserData(p, p); 66 XML_SetElementHandler(p, start, end); 67 XML_SetCharacterDataHandler(p, may_stop_character_handler); 68 XML_Parse(p, (const XML_Char *)data, size, 0); 69 if (XML_Parse(p, (const XML_Char *)data, size, 1) == XML_STATUS_ERROR) { 70 XML_ErrorString(XML_GetErrorCode(p)); 71 } 72 XML_GetCurrentLineNumber(p); 73 if (size % 2) { 74 XML_ParserReset(p, NULL); 75 } 76 } 77 78 int 79 LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) { 80 XML_Parser parentParser = XML_ParserCreate(xstr(ENCODING_FOR_FUZZING)); 81 assert(parentParser); 82 ParseOneInput(parentParser, data, size); 83 // not freed yet, but used later and freed then 84 85 XML_Parser namespaceParser = XML_ParserCreateNS(NULL, '!'); 86 assert(namespaceParser); 87 ParseOneInput(namespaceParser, data, size); 88 XML_ParserFree(namespaceParser); 89 90 XML_Parser externalEntityParser 91 = XML_ExternalEntityParserCreate(parentParser, "e1", NULL); 92 assert(externalEntityParser); 93 ParseOneInput(externalEntityParser, data, size); 94 XML_ParserFree(externalEntityParser); 95 96 XML_Parser externalDtdParser 97 = XML_ExternalEntityParserCreate(parentParser, NULL, NULL); 98 assert(externalDtdParser); 99 ParseOneInput(externalDtdParser, data, size); 100 XML_ParserFree(externalDtdParser); 101 102 // finally frees this parser which served as parent 103 XML_ParserFree(parentParser); 104 return 0; 105 } 106