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
start(void * userData,const XML_Char * name,const XML_Char ** atts)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
end(void * userData,const XML_Char * name)46 end(void *userData, const XML_Char *name) {
47 (void)userData;
48 (void)name;
49 }
50
51 static void XMLCALL
may_stop_character_handler(void * userData,const XML_Char * s,int len)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
ParseOneInput(XML_Parser p,const uint8_t * data,size_t size)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
LLVMFuzzerTestOneInput(const uint8_t * data,size_t size)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