Adding -fuzz_testing command line option, which disables the file data CRC16 check used by the -validate command. To fuzz testing using zzuf on Linux:

zzuf -d -c -s 1000000:2000000 ./basisu -validate -fuzz_testing kodim23.basis

basisu_tool.cpp

@@ -54,7 +54,7 @@ static void print_usage()
 		"Important: By default, the compressor assumes the input is in the sRGB colorspace (like photos/albedo textures).\n"
 		"If the input is NOT sRGB (like a normal map), be sure to specify -linear for less artifacts.\n"
 		"\n"
-		"Filenames prefixed with a @ symbol are read as filename listing files.\n"
+		"Filenames prefixed with a @ symbol are read as filename listing files, specifying which filenames to actually process.\n"
 		"\n"
 		"Options:\n"
 		" -file filename.png: Input image filename, multiple images are OK, use -file X for each input filename (prefixing input filenames with -file is optional)\n"
@@ -74,6 +74,7 @@ static void print_usage()
 		"  (2d=arbitrary 2D images, 2darray=2D array, 3D=volume texture slices, video=video frames, cubemap=array of faces. For 2darray/3d/cubemaps/video, each source image's dimensions and # of mipmap levels must be the same.)\n"
 		" -framerate X: Set framerate in header to X/frames sec\n"
 		" -individual: Process input images individually and output multiple .basis files (not as a texture array)\n"
+		" -fuzz_testing: Use with -validate: Disables CRC16 validation of file contents before transcoding\n"
 		"\n"
 		"More options:\n"
 		" -max_endpoints X: Manually set the max number of color endpoint clusters from 1-16128, use instead of -q\n"
@@ -207,7 +208,8 @@ public:
 		m_multifile_first(0),
 		m_multifile_num(0),
 		m_individual(false),
-		m_no_ktx(false)
+		m_no_ktx(false),
+		m_fuzz_testing(false)
 	{
 	}
 
@@ -443,6 +445,8 @@ public:
 			}
 			else if (strcasecmp(pArg, "-individual") == 0)
 				m_individual = true;
+			else if (strcasecmp(pArg, "-fuzz_testing") == 0)
+				m_fuzz_testing = true;
 			else if (strcasecmp(pArg, "-csv_file") == 0)
 			{
 				REMAINING_ARGS_CHECK(1);
@@ -531,6 +535,7 @@ public:
 
 	bool m_individual;
 	bool m_no_ktx;
+	bool m_fuzz_testing;
 };
 
 static bool expand_multifile(command_line_params &opts)
@@ -790,22 +795,27 @@ static bool unpack_and_validate_mode(command_line_params &opts, bool validate_fl
 
 		basist::basisu_transcoder dec(&sel_codebook);
 
-		// Validate the file - note this isn't necessary for transcoding
-		if (!dec.validate_file_checksums(&basis_data[0], (uint32_t)basis_data.size(), true))
+		if (!opts.m_fuzz_testing)
 		{
-			error_printf("File version is unsupported, or file fail CRC checks!\n");
-			return false;
+			// Skip the full validation, which CRC16's the entire file.
+
+			// Validate the file - note this isn't necessary for transcoding
+			if (!dec.validate_file_checksums(&basis_data[0], (uint32_t)basis_data.size(), true))
+			{
+				error_printf("File version is unsupported, or file fail CRC checks!\n");
+				return false;
+			}
 		}
 
 		printf("File version and CRC checks succeeded\n");
-				
+		
 		basist::basisu_file_info fileinfo;
 		if (!dec.get_file_info(&basis_data[0], (uint32_t)basis_data.size(), fileinfo))
 		{
 			error_printf("Failed retrieving Basis file information!\n");
 			return false;
 		}
-
+		
 		assert(fileinfo.m_total_images == fileinfo.m_image_mipmap_levels.size());
 		assert(fileinfo.m_total_images == dec.get_total_images(&basis_data[0], (uint32_t)basis_data.size()));
 

transcoder/basisu_transcoder.cpp

@@ -3336,13 +3336,19 @@ namespace basist
 			BASISU_DEVEL_ERROR("basisu_lowlevel_transcoder::decode_palettes: fail 2a\n");		
 			return false;
 		}
-
+				
 		if (!sym_codec.read_huffman_table(inten_delta_model))
 		{
 			BASISU_DEVEL_ERROR("basisu_lowlevel_transcoder::decode_palettes: fail 2b\n");		
 			return false;
 		}
 
+		if (!color5_delta_model0.is_valid() || !color5_delta_model1.is_valid() || !color5_delta_model2.is_valid() || !inten_delta_model.is_valid())
+		{
+			BASISU_DEVEL_ERROR("basisu_lowlevel_transcoder::decode_palettes: fail 2b\n");		
+			return false;
+		}
+
 		const bool endpoints_are_grayscale = sym_codec.get_bits(1) != 0;
 		
 		m_endpoints.resize(num_endpoints);
@@ -3408,6 +3414,11 @@ namespace basist
 					BASISU_DEVEL_ERROR("basisu_lowlevel_transcoder::decode_palettes: fail 6\n");		
 					return false;
 				}
+				if (!mod_model.is_valid())
+				{
+					BASISU_DEVEL_ERROR("basisu_lowlevel_transcoder::decode_palettes: fail 6a\n");		
+					return false;
+				}
 			}
 						
 			for (uint32_t i = 0; i < num_selectors; i++)
@@ -3445,6 +3456,11 @@ namespace basist
 					BASISU_DEVEL_ERROR("basisu_lowlevel_transcoder::decode_palettes: fail 7\n");		
 					return false;
 				}
+				if (!uses_global_cb_bitflags_model.is_valid())
+				{
+					BASISU_DEVEL_ERROR("basisu_lowlevel_transcoder::decode_palettes: fail 7a\n");		
+					return false;
+				}
 
 				basist::huffman_decoding_table global_mod_indices_model;
 				if (mod_bits)
@@ -3454,6 +3470,11 @@ namespace basist
 						BASISU_DEVEL_ERROR("basisu_lowlevel_transcoder::decode_palettes: fail 8\n");		
 						return false;
 					}
+					if (!global_mod_indices_model.is_valid())
+					{
+						BASISU_DEVEL_ERROR("basisu_lowlevel_transcoder::decode_palettes: fail 8a\n");		
+						return false;
+					}
 				}
 
 				uint32_t cur_uses_global_cb_bitflags = 0;
@@ -3519,7 +3540,16 @@ namespace basist
 				else
 				{
 					if (!sym_codec.read_huffman_table(delta_selector_pal_model))
+					{
+						BASISU_DEVEL_ERROR("basisu_lowlevel_transcoder::decode_palettes: fail 10\n");		
 						return false;
+					}
+
+					if ((num_selectors > 1) && (!delta_selector_pal_model.is_valid()))
+					{
+						BASISU_DEVEL_ERROR("basisu_lowlevel_transcoder::decode_palettes: fail 10a\n");		
+						return false;
+					}
 
 					uint8_t prev_bytes[4] = { 0, 0, 0, 0 };
 					
@@ -3574,10 +3604,22 @@ namespace basist
 			BASISU_DEVEL_ERROR("basisu_lowlevel_transcoder::decode_tables: fail 1\n");		
 			return false;
 		}
+		
+		if (m_endpoint_pred_model.get_code_sizes().size() == 0)
+		{
+			BASISU_DEVEL_ERROR("basisu_lowlevel_transcoder::decode_tables: fail 1a\n");		
+			return false;
+		}
 
 		if (!sym_codec.read_huffman_table(m_delta_endpoint_model))
 		{
-			BASISU_DEVEL_ERROR("basisu_lowlevel_transcoder::decode_tables: fail 1\n");		
+			BASISU_DEVEL_ERROR("basisu_lowlevel_transcoder::decode_tables: fail 2\n");		
+			return false;
+		}
+
+		if (m_delta_endpoint_model.get_code_sizes().size() == 0)
+		{
+			BASISU_DEVEL_ERROR("basisu_lowlevel_transcoder::decode_tables: fail 2a\n");		
 			return false;
 		}
 
@@ -3587,12 +3629,24 @@ namespace basist
 			return false;
 		}
 
+		if (m_selector_model.get_code_sizes().size() == 0)
+		{
+			BASISU_DEVEL_ERROR("basisu_lowlevel_transcoder::decode_tables: fail 3a\n");		
+			return false;
+		}
+
 		if (!sym_codec.read_huffman_table(m_selector_history_buf_rle_model))
 		{
 			BASISU_DEVEL_ERROR("basisu_lowlevel_transcoder::decode_tables: fail 4\n");		
 			return false;
 		}
 
+		if (m_selector_history_buf_rle_model.get_code_sizes().size() == 0)
+		{
+			BASISU_DEVEL_ERROR("basisu_lowlevel_transcoder::decode_tables: fail 4a\n");		
+			return false;
+		}
+
 		m_selector_history_buf_size = sym_codec.get_bits(13);
 				
 		sym_codec.stop();
@@ -3791,6 +3845,16 @@ namespace basist
 					assert(m_selector_history_buf_size > 0);
 
 					int history_buf_index = selector_sym - (int)m_selectors.size();
+
+					if (history_buf_index >= (int)selector_history_buf.size())
+					{
+						// The file is corrupted or we've got a bug.
+							//console::error("rdo_etc1_lowlevel_decoder::transcode_slice: selector RLE value is too large!");
+						if (pPVRTC_work_mem)
+							free(pPVRTC_work_mem);
+						return false;
+					}
+
 					selector_index = selector_history_buf[history_buf_index];
 
 					if (history_buf_index != 0)
@@ -4310,6 +4374,12 @@ namespace basist
 			slice_info.m_unpacked_slice_crc16 = pSlice_descs[i].m_slice_data_crc16;
 			slice_info.m_alpha_flag = (pSlice_descs[i].m_flags & cSliceDescFlagsIsAlphaData) != 0;
 
+			if (pSlice_descs[i].m_image_index >= pHeader->m_total_images)
+			{
+				BASISU_DEVEL_ERROR("basisu_transcoder::get_file_info: slice desc's image index is invalid\n");
+				return false;
+			}
+
 			file_info.m_image_mipmap_levels[pSlice_descs[i].m_image_index] = basisu::maximum<uint32_t>(file_info.m_image_mipmap_levels[pSlice_descs[i].m_image_index], pSlice_descs[i].m_level_index + 1);
 		}
 

transcoder/basisu_transcoder_internal.h

@@ -162,6 +162,8 @@ namespace basist
 
 		const basisu::uint8_vec &get_code_sizes() const { return m_code_sizes; }
 
+		bool is_valid() const { return m_code_sizes.size() > 0; }
+
 	private:
 		basisu::uint8_vec m_code_sizes;
 		basisu::int_vec m_lookup;