/*************************************************************************************************** Zyan Disassembler Library (Zydis) Original Author : Joel Hoener * 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 decoder, formatter and various utility functions. */ #include "ZydisFuzzShared.h" /* ============================================================================================== */ /* Enums and types */ /* ============================================================================================== */ /** * Main fuzzer control block data structure. */ typedef struct ZydisFuzzControlBlock_ { ZydisMachineMode machine_mode; ZydisStackWidth stack_width; ZyanBool decoder_mode[ZYDIS_DECODER_MODE_MAX_VALUE + 1]; ZydisFormatterStyle formatter_style; ZyanU64 u64; // u64 used for all kind of non-overlapping purposes ZyanUPointer formatter_properties[ZYDIS_FORMATTER_PROP_MAX_VALUE + 1]; char string[16]; ZyanU16 formatter_max_len; } ZydisFuzzControlBlock; /* ============================================================================================== */ /* Fuzz target */ /* ============================================================================================== */ // We disable enum sanitization here because we actually want Zydis to be tested with // possibly invalid enum values in mind, thus need to be able to create them here. ZYAN_NO_SANITIZE("enum") int ZydisFuzzTarget(ZydisStreamRead read_fn, void* stream_ctx) { ZydisFuzzControlBlock control_block; if (read_fn( stream_ctx, (ZyanU8*)&control_block, sizeof(control_block)) != sizeof(control_block)) { ZYDIS_MAYBE_FPUTS("Not enough bytes to fuzz\n", ZYAN_STDERR); return EXIT_SUCCESS; } control_block.string[ZYAN_ARRAY_LENGTH(control_block.string) - 1] = 0; ZydisDecoder decoder; if (!ZYAN_SUCCESS(ZydisDecoderInit(&decoder, control_block.machine_mode, control_block.stack_width))) { ZYDIS_MAYBE_FPUTS("Failed to initialize decoder\n", ZYAN_STDERR); return EXIT_FAILURE; } for (int mode = 0; mode <= ZYDIS_DECODER_MODE_MAX_VALUE; ++mode) { if (!ZYAN_SUCCESS(ZydisDecoderEnableMode(&decoder, (ZydisDecoderMode)mode, control_block.decoder_mode[mode] ? 1 : 0))) { ZYDIS_MAYBE_FPUTS("Failed to adjust decoder-mode\n", ZYAN_STDERR); return EXIT_FAILURE; } } ZydisFormatter formatter; if (!ZYAN_SUCCESS(ZydisFormatterInit(&formatter, control_block.formatter_style))) { ZYDIS_MAYBE_FPUTS("Failed to initialize formatter\n", ZYAN_STDERR); return EXIT_FAILURE; } for (int prop = 0; prop <= ZYDIS_FORMATTER_PROP_MAX_VALUE; ++prop) { switch (prop) { case ZYDIS_FORMATTER_PROP_DEC_PREFIX: case ZYDIS_FORMATTER_PROP_DEC_SUFFIX: case ZYDIS_FORMATTER_PROP_HEX_PREFIX: case ZYDIS_FORMATTER_PROP_HEX_SUFFIX: control_block.formatter_properties[prop] = control_block.formatter_properties[prop] ? (ZyanUPointer)&control_block.string : 0; break; default: break; } if (!ZYAN_SUCCESS(ZydisFormatterSetProperty(&formatter, (ZydisFormatterProperty)prop, control_block.formatter_properties[prop]))) { ZYDIS_MAYBE_FPUTS("Failed to set formatter-attribute\n", ZYAN_STDERR); return EXIT_FAILURE; } } ZyanU8 buffer[32]; ZyanUSize input_len = read_fn(stream_ctx, buffer, sizeof(buffer)); ZydisDecodedInstruction instruction; ZydisDecodedOperand operands[ZYDIS_MAX_OPERAND_COUNT]; // Fuzz decoder. ZyanStatus status = ZydisDecoderDecodeFull(&decoder, buffer, input_len, &instruction, operands); if (!ZYAN_SUCCESS(status)) { return EXIT_FAILURE; } ZydisValidateEnumRanges(&instruction, operands, instruction.operand_count); // Fuzz formatter. char format_buffer[256]; // Allow the control block to artificially restrict the buffer size. ZyanUSize output_len = ZYAN_MIN(sizeof(format_buffer), control_block.formatter_max_len); ZydisFormatterFormatInstruction(&formatter, &instruction, operands, instruction.operand_count_visible, format_buffer, output_len, control_block.u64, ZYAN_NULL); // Fuzz tokenizer. const ZydisFormatterToken* token; status = ZydisFormatterTokenizeInstruction(&formatter, &instruction, operands, instruction.operand_count_visible, format_buffer, output_len, control_block.u64, &token, ZYAN_NULL); // Walk tokens. while (ZYAN_SUCCESS(status)) { ZydisTokenType type; ZyanConstCharPointer value; if (!ZYAN_SUCCESS(status = ZydisFormatterTokenGetValue(token, &type, &value))) { ZYDIS_MAYBE_FPUTS("Failed to get token value\n", ZYAN_STDERR); break; } status = ZydisFormatterTokenNext(&token); } if (instruction.operand_count_visible > 0) { // Fuzz single operand formatting. We reuse rt-address for operand selection. // It's casted to u8 because modulo is way cheaper on that. ZyanU8 op_idx = (ZyanU8)control_block.u64 % instruction.operand_count_visible; const ZydisDecodedOperand* op = &operands[op_idx]; ZydisFormatterFormatOperand(&formatter, &instruction, op, format_buffer, output_len, control_block.u64, ZYAN_NULL); // Fuzz single operand tokenization. ZydisFormatterTokenizeOperand(&formatter, &instruction, op, format_buffer, output_len, control_block.u64, &token, ZYAN_NULL); // Address translation helper. ZyanU64 abs_addr; ZydisCalcAbsoluteAddress(&instruction, op, control_block.u64, &abs_addr); } // Mnemonic helpers. ZydisMnemonicGetString((ZydisMnemonic)control_block.u64); ZydisMnemonicGetStringWrapped((ZydisMnemonic)control_block.u64); // Instruction segment helper. # ifndef ZYDIS_DISABLE_SEGMENT ZydisInstructionSegments segments; ZydisGetInstructionSegments(&instruction, &segments); # endif // Feature enable check helper. ZydisIsFeatureEnabled((ZydisFeature)control_block.u64); // Register helpers. ZydisRegisterEncode((ZydisRegisterClass)(control_block.u64 >> 8), (ZyanU8)control_block.u64); ZydisRegisterGetId((ZydisRegister)control_block.u64); ZydisRegisterGetClass((ZydisRegister)control_block.u64); ZydisRegisterGetWidth(control_block.machine_mode, (ZydisRegister)control_block.u64); ZydisRegisterGetLargestEnclosing(control_block.machine_mode, (ZydisRegister)control_block.u64); ZydisRegisterGetString((ZydisRegister)control_block.u64); ZydisRegisterGetStringWrapped((ZydisRegister)control_block.u64); ZydisRegisterClassGetWidth(control_block.machine_mode, (ZydisRegisterClass)control_block.u64); return EXIT_SUCCESS; } /* ============================================================================================== */