1 // Copyright 2018 Google Inc.
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14 //
15 ////////////////////////////////////////////////////////////////////////////////
16
17 #include <string.h>
18
19 #include "./fuzz_utils.h"
20 #include "src/webp/decode.h"
21
LLVMFuzzerTestOneInput(const uint8_t* const data, size_t size)22 int LLVMFuzzerTestOneInput(const uint8_t* const data, size_t size) {
23 int i;
24 WebPDecoderConfig config;
25 if (!WebPInitDecoderConfig(&config)) return 0;
26 if (WebPGetFeatures(data, size, &config.input) != VP8_STATUS_OK) return 0;
27 if ((size_t)config.input.width * config.input.height > kFuzzPxLimit) return 0;
28
29 // Using two independent criteria ensures that all combinations of options
30 // can reach each path at the decoding stage, with meaningful differences.
31
32 const uint8_t value = FuzzHash(data, size);
33 const float factor = value / 255.f; // 0-1
34
35 config.options.flip = value & 1;
36 config.options.bypass_filtering = value & 2;
37 config.options.no_fancy_upsampling = value & 4;
38 config.options.use_threads = value & 8;
39 if (size & 1) {
40 config.options.use_cropping = 1;
41 config.options.crop_width = (int)(config.input.width * (1 - factor));
42 config.options.crop_height = (int)(config.input.height * (1 - factor));
43 config.options.crop_left = config.input.width - config.options.crop_width;
44 config.options.crop_top = config.input.height - config.options.crop_height;
45 }
46 if (size & 2) {
47 int strength = (int)(factor * 100);
48 config.options.dithering_strength = strength;
49 config.options.alpha_dithering_strength = 100 - strength;
50 }
51 if (size & 4) {
52 config.options.use_scaling = 1;
53 config.options.scaled_width = (int)(config.input.width * factor * 2);
54 config.options.scaled_height = (int)(config.input.height * factor * 2);
55 }
56
57 #if defined(WEBP_REDUCE_CSP)
58 config.output.colorspace = (value & 1)
59 ? ((value & 2) ? MODE_RGBA : MODE_BGRA)
60 : ((value & 2) ? MODE_rgbA : MODE_bgrA);
61 #else
62 config.output.colorspace = (WEBP_CSP_MODE)(value % MODE_LAST);
63 #endif // WEBP_REDUCE_CSP
64
65 for (i = 0; i < 2; ++i) {
66 if (i == 1) {
67 // Use the bitstream data to generate extreme ranges for the options. An
68 // alternative approach would be to use a custom corpus containing webp
69 // files prepended with sizeof(config.options) zeroes to allow the fuzzer
70 // to modify these independently.
71 const int data_offset = 50;
72 if (size > data_offset + sizeof(config.options)) {
73 memcpy(&config.options, data + data_offset, sizeof(config.options));
74 } else {
75 break;
76 }
77 }
78 if (size % 3) {
79 // Decodes incrementally in chunks of increasing size.
80 WebPIDecoder* idec = WebPIDecode(NULL, 0, &config);
81 if (!idec) return 0;
82 VP8StatusCode status;
83 if (size & 8) {
84 size_t available_size = value + 1;
85 while (1) {
86 if (available_size > size) available_size = size;
87 status = WebPIUpdate(idec, data, available_size);
88 if (status != VP8_STATUS_SUSPENDED || available_size == size) break;
89 available_size *= 2;
90 }
91 } else {
92 // WebPIAppend expects new data and its size with each call.
93 // Implemented here by simply advancing the pointer into data.
94 const uint8_t* new_data = data;
95 size_t new_size = value + 1;
96 while (1) {
97 if (new_data + new_size > data + size) {
98 new_size = data + size - new_data;
99 }
100 status = WebPIAppend(idec, new_data, new_size);
101 if (status != VP8_STATUS_SUSPENDED || new_size == 0) break;
102 new_data += new_size;
103 new_size *= 2;
104 }
105 }
106 WebPIDelete(idec);
107 } else {
108 WebPDecode(data, size, &config);
109 }
110
111 WebPFreeDecBuffer(&config.output);
112 }
113 return 0;
114 }
115