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 static void XMLCALL 52 may_stop_character_handler(void *userData, const XML_Char *s, int len) { 53 XML_Parser parser = (XML_Parser)userData; 54 if (len > 1 && s[0] == 's') { 55 XML_StopParser(parser, s[1] == 'r' ? XML_FALSE : XML_TRUE); 56 } 57 } 58 59 static void 60 ParseOneInput(XML_Parser p, const uint8_t *data, size_t size) { 61 // Set the hash salt using siphash to generate a deterministic hash. 62 struct sipkey *key = sip_keyof(hash_key); 63 XML_SetHashSalt(p, (unsigned long)siphash24(data, size, key)); 64 (void)sip24_valid; 65 66 XML_SetUserData(p, p); 67 XML_SetElementHandler(p, start, end); 68 XML_SetCharacterDataHandler(p, may_stop_character_handler); 69 void *buf = XML_GetBuffer(p, size); 70 assert(buf); 71 memcpy(buf, data, size); 72 XML_ParseBuffer(p, size, 0); 73 buf = XML_GetBuffer(p, size); 74 if (buf == NULL) { 75 return; 76 } 77 memcpy(buf, data, size); 78 if (XML_ParseBuffer(p, size, 1) == XML_STATUS_ERROR) { 79 XML_ErrorString(XML_GetErrorCode(p)); 80 } 81 XML_GetCurrentLineNumber(p); 82 if (size % 2) { 83 XML_ParserReset(p, NULL); 84 } 85 } 86 87 int 88 LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) { 89 if (size == 0) 90 return 0; 91 92 XML_Parser parentParser = XML_ParserCreate(xstr(ENCODING_FOR_FUZZING)); 93 assert(parentParser); 94 ParseOneInput(parentParser, data, size); 95 // not freed yet, but used later and freed then 96 97 XML_Parser namespaceParser = XML_ParserCreateNS(NULL, '!'); 98 assert(namespaceParser); 99 ParseOneInput(namespaceParser, data, size); 100 XML_ParserFree(namespaceParser); 101 102 XML_Parser externalEntityParser 103 = XML_ExternalEntityParserCreate(parentParser, "e1", NULL); 104 assert(externalEntityParser); 105 ParseOneInput(externalEntityParser, data, size); 106 XML_ParserFree(externalEntityParser); 107 108 XML_Parser externalDtdParser 109 = XML_ExternalEntityParserCreate(parentParser, NULL, NULL); 110 assert(externalDtdParser); 111 ParseOneInput(externalDtdParser, data, size); 112 XML_ParserFree(externalDtdParser); 113 114 // finally frees this parser which served as parent 115 XML_ParserFree(parentParser); 116 return 0; 117 } 118