1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
|
/***************************************************************************************************
Zyan Disassembler Library (Zydis)
Original Author : Mappa
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
***************************************************************************************************/
/**
* @file
*
* This file implements fuzz target for encoder.
*/
#include "ZydisFuzzShared.h"
/* ============================================================================================== */
/* Fuzz target */
/* ============================================================================================== */
// TODO: This could check `EVEX`/`MVEX` stuff as well
void ZydisCompareRequestToInstruction(const ZydisEncoderRequest *request,
const ZydisDecodedInstruction *insn, const ZydisDecodedOperand* operands, const ZyanU8 *insn_bytes)
{
// Special case, `xchg rAX, rAX` is an alias for `NOP`
if ((request->mnemonic == ZYDIS_MNEMONIC_XCHG) &&
(request->operand_count == 2) &&
(request->operands[0].type == ZYDIS_OPERAND_TYPE_REGISTER) &&
(request->operands[1].type == ZYDIS_OPERAND_TYPE_REGISTER) &&
(request->operands[0].reg.value == request->operands[1].reg.value) &&
(insn->mnemonic == ZYDIS_MNEMONIC_NOP))
{
switch (request->operands[0].reg.value)
{
case ZYDIS_REGISTER_AX:
case ZYDIS_REGISTER_EAX:
case ZYDIS_REGISTER_RAX:
return;
default:
break;
}
}
// Handle possible KNC overlap
ZydisDecodedInstruction knc_insn;
ZydisDecodedOperand knc_operands[ZYDIS_MAX_OPERAND_COUNT];
if (request->mnemonic != insn->mnemonic)
{
ZydisDecoder decoder;
ZydisStackWidth stack_width = (ZydisStackWidth)(insn->stack_width >> 5);
if (!ZYAN_SUCCESS(ZydisDecoderInit(&decoder, insn->machine_mode, stack_width)))
{
fputs("Failed to initialize decoder\n", ZYAN_STDERR);
abort();
}
if (!ZYAN_SUCCESS(ZydisDecoderEnableMode(&decoder, ZYDIS_DECODER_MODE_KNC, ZYAN_TRUE)))
{
fputs("Failed to enable KNC mode\n", ZYAN_STDERR);
abort();
}
if (!ZYAN_SUCCESS(ZydisDecoderDecodeFull(&decoder, insn_bytes, insn->length, &knc_insn,
knc_operands)))
{
fputs("Failed to decode instruction\n", ZYAN_STDERR);
abort();
}
insn = &knc_insn;
operands = knc_operands;
}
ZyanBool prefixes_match = ((insn->attributes & request->prefixes) == request->prefixes);
if (!prefixes_match &&
(request->machine_mode != ZYDIS_MACHINE_MODE_LONG_64) &&
(request->prefixes & ZYDIS_ATTRIB_HAS_SEGMENT_DS))
{
// Encoder allows specifying DS override even when it might be interpreted as NOTRACK
ZyanU64 acceptable_prefixes = (request->prefixes & (~ZYDIS_ATTRIB_HAS_SEGMENT_DS)) |
ZYDIS_ATTRIB_HAS_NOTRACK;
prefixes_match = ((insn->attributes & acceptable_prefixes) == acceptable_prefixes);
}
if ((request->machine_mode != insn->machine_mode) ||
(request->mnemonic != insn->mnemonic) ||
(request->operand_count != insn->operand_count_visible) ||
!prefixes_match)
{
fputs("Basic instruction attributes mismatch\n", ZYAN_STDERR);
abort();
}
for (ZyanU8 i = 0; i < insn->operand_count_visible; ++i)
{
const ZydisEncoderOperand *op1 = &request->operands[i];
const ZydisDecodedOperand *op2 = &operands[i];
if (op1->type != op2->type)
{
fprintf(ZYAN_STDERR, "Mismatch for operand %u\n", i);
abort();
}
switch (op1->type)
{
case ZYDIS_OPERAND_TYPE_REGISTER:
if (op1->reg.value != op2->reg.value)
{
fprintf(ZYAN_STDERR, "Mismatch for register operand %u\n", i);
abort();
}
break;
case ZYDIS_OPERAND_TYPE_MEMORY:
if ((op1->mem.base != op2->mem.base) ||
(op1->mem.index != op2->mem.index) ||
(op1->mem.scale != op2->mem.scale && op2->mem.type != ZYDIS_MEMOP_TYPE_MIB) ||
(op1->mem.displacement != op2->mem.disp.value))
{
ZyanBool acceptable_mismatch = ZYAN_FALSE;
if (op1->mem.displacement != op2->mem.disp.value)
{
if ((op2->mem.disp.has_displacement) &&
(op1->mem.index == ZYDIS_REGISTER_NONE) &&
((op1->mem.base == ZYDIS_REGISTER_NONE) ||
(op1->mem.base == ZYDIS_REGISTER_EIP) ||
(op1->mem.base == ZYDIS_REGISTER_RIP)))
{
ZyanU64 addr;
ZydisCalcAbsoluteAddress(insn, op2, 0, &addr);
acceptable_mismatch = ((ZyanU64)op1->mem.displacement == addr);
}
if ((insn->machine_mode == ZYDIS_MACHINE_MODE_REAL_16) ||
(insn->machine_mode == ZYDIS_MACHINE_MODE_LEGACY_16) ||
(insn->machine_mode == ZYDIS_MACHINE_MODE_LONG_COMPAT_16) ||
(insn->stack_width == 16) ||
(insn->address_width == 16))
{
acceptable_mismatch = ((op1->mem.displacement & 0xFFFF) ==
(op2->mem.disp.value & 0xFFFF));
}
}
if (!acceptable_mismatch)
{
fprintf(ZYAN_STDERR, "Mismatch for memory operand %u\n", i);
abort();
}
}
break;
case ZYDIS_OPERAND_TYPE_POINTER:
if ((op1->ptr.segment != op2->ptr.segment) ||
(op1->ptr.offset != op2->ptr.offset))
{
fprintf(ZYAN_STDERR, "Mismatch for pointer operand %u\n", i);
abort();
}
break;
case ZYDIS_OPERAND_TYPE_IMMEDIATE:
if (op1->imm.u != op2->imm.value.u)
{
ZyanBool acceptable_mismatch = ZYAN_FALSE;
if ((insn->meta.category == ZYDIS_CATEGORY_DATAXFER) ||
(insn->meta.category == ZYDIS_CATEGORY_LOGICAL))
{
if (op2->size < 64)
{
ZyanU64 mask = (1ULL << op2->size) - 1;
acceptable_mismatch =
(op1->imm.u & mask) == (op2->imm.value.u & mask);
}
else
{
acceptable_mismatch = op1->imm.u == op2->imm.value.u;
}
}
if (!acceptable_mismatch)
{
fprintf(ZYAN_STDERR, "Mismatch for immediate operand %u\n", i);
abort();
}
}
break;
default:
fprintf(ZYAN_STDERR, "Invalid operand type for operand %u\n", i);
abort();
}
}
}
ZYAN_NO_SANITIZE("enum")
int ZydisFuzzTarget(ZydisStreamRead read_fn, void *stream_ctx)
{
ZydisEncoderRequest request;
if (read_fn(stream_ctx, (ZyanU8 *)&request, sizeof(request)) != sizeof(request))
{
ZYDIS_MAYBE_FPUTS("Not enough bytes to fuzz\n", ZYAN_STDERR);
return EXIT_SUCCESS;
}
// Sanitization greatly improves coverage, without it most inputs will fail at basic checks
// inside `ZydisEncoderCheckRequestSanity`
request.operand_count %= ZYDIS_ENCODER_MAX_OPERANDS + 1;
ZYDIS_SANITIZE_MASK32(request.allowed_encodings, ZydisEncodableEncoding,
ZYDIS_ENCODABLE_ENCODING_MAX_VALUE);
ZYDIS_SANITIZE_MASK64(request.prefixes, ZydisInstructionAttributes, ZYDIS_ENCODABLE_PREFIXES);
ZYDIS_SANITIZE_ENUM(request.machine_mode, ZydisMachineMode, ZYDIS_MACHINE_MODE_MAX_VALUE);
ZYDIS_SANITIZE_ENUM(request.mnemonic, ZydisMnemonic, ZYDIS_MNEMONIC_MAX_VALUE);
ZYDIS_SANITIZE_ENUM(request.branch_type, ZydisBranchType, ZYDIS_BRANCH_TYPE_MAX_VALUE);
ZYDIS_SANITIZE_ENUM(request.branch_width, ZydisBranchWidth, ZYDIS_BRANCH_WIDTH_MAX_VALUE);
ZYDIS_SANITIZE_ENUM(request.address_size_hint, ZydisAddressSizeHint,
ZYDIS_ADDRESS_SIZE_HINT_MAX_VALUE);
ZYDIS_SANITIZE_ENUM(request.operand_size_hint, ZydisOperandSizeHint,
ZYDIS_OPERAND_SIZE_HINT_MAX_VALUE);
ZYDIS_SANITIZE_ENUM(request.evex.broadcast, ZydisBroadcastMode, ZYDIS_BROADCAST_MODE_MAX_VALUE);
ZYDIS_SANITIZE_ENUM(request.evex.rounding, ZydisRoundingMode, ZYDIS_ROUNDING_MODE_MAX_VALUE);
ZYDIS_SANITIZE_ENUM(request.mvex.broadcast, ZydisBroadcastMode, ZYDIS_BROADCAST_MODE_MAX_VALUE);
ZYDIS_SANITIZE_ENUM(request.mvex.conversion, ZydisConversionMode,
ZYDIS_CONVERSION_MODE_MAX_VALUE);
ZYDIS_SANITIZE_ENUM(request.mvex.rounding, ZydisRoundingMode, ZYDIS_ROUNDING_MODE_MAX_VALUE);
ZYDIS_SANITIZE_ENUM(request.mvex.swizzle, ZydisSwizzleMode, ZYDIS_SWIZZLE_MODE_MAX_VALUE);
for (ZyanU8 i = 0; i < request.operand_count; ++i)
{
ZydisEncoderOperand *op = &request.operands[i];
op->type = (ZydisOperandType)(ZYDIS_OPERAND_TYPE_REGISTER +
((ZyanUSize)op->type % ZYDIS_OPERAND_TYPE_MAX_VALUE));
switch (op->type)
{
case ZYDIS_OPERAND_TYPE_REGISTER:
ZYDIS_SANITIZE_ENUM(op->reg.value, ZydisRegister, ZYDIS_REGISTER_MAX_VALUE);
break;
case ZYDIS_OPERAND_TYPE_MEMORY:
ZYDIS_SANITIZE_ENUM(op->mem.base, ZydisRegister, ZYDIS_REGISTER_MAX_VALUE);
ZYDIS_SANITIZE_ENUM(op->mem.index, ZydisRegister, ZYDIS_REGISTER_MAX_VALUE);
break;
case ZYDIS_OPERAND_TYPE_POINTER:
case ZYDIS_OPERAND_TYPE_IMMEDIATE:
break;
default:
ZYAN_UNREACHABLE;
}
}
ZyanU8 encoded_instruction[ZYDIS_MAX_INSTRUCTION_LENGTH];
ZyanUSize encoded_length = sizeof(encoded_instruction);
ZyanStatus status = ZydisEncoderEncodeInstruction(&request, encoded_instruction,
&encoded_length);
if (!ZYAN_SUCCESS(status))
{
return EXIT_SUCCESS;
}
ZydisStackWidth stack_width;
switch (request.machine_mode)
{
case ZYDIS_MACHINE_MODE_LONG_64:
stack_width = ZYDIS_STACK_WIDTH_64;
break;
case ZYDIS_MACHINE_MODE_LONG_COMPAT_32:
case ZYDIS_MACHINE_MODE_LEGACY_32:
stack_width = ZYDIS_STACK_WIDTH_32;
break;
case ZYDIS_MACHINE_MODE_LONG_COMPAT_16:
case ZYDIS_MACHINE_MODE_LEGACY_16:
case ZYDIS_MACHINE_MODE_REAL_16:
stack_width = ZYDIS_STACK_WIDTH_16;
break;
default:
ZYAN_UNREACHABLE;
}
ZydisDecoder decoder;
if (!ZYAN_SUCCESS(ZydisDecoderInit(&decoder, request.machine_mode, stack_width)))
{
fputs("Failed to initialize decoder\n", ZYAN_STDERR);
abort();
}
if (request.mnemonic == ZYDIS_MNEMONIC_UD0 && request.operand_count == 0)
{
status = ZydisDecoderEnableMode(&decoder, ZYDIS_DECODER_MODE_UD0_COMPAT, ZYAN_TRUE);
if (!ZYAN_SUCCESS(status))
{
fputs("Failed to enable UD0_COMPAT mode\n", ZYAN_STDERR);
abort();
}
}
ZydisDecodedInstruction insn1;
ZydisDecodedOperand operands1[ZYDIS_MAX_OPERAND_COUNT];
status = ZydisDecoderDecodeFull(&decoder, encoded_instruction, encoded_length, &insn1,
operands1);
if (!ZYAN_SUCCESS(status))
{
fputs("Failed to decode instruction\n", ZYAN_STDERR);
abort();
}
ZydisCompareRequestToInstruction(&request, &insn1, operands1, encoded_instruction);
ZydisReEncodeInstruction(&decoder, &insn1, operands1, insn1.operand_count,
encoded_instruction);
return EXIT_SUCCESS;
}
/* ============================================================================================== */
|
