High level conclusions

Fuzzers reach 66.43% code coverage.

Fuzzers reach 75.42% of cyclomatic complexity.

Fuzzers reach 68.49% of all functions.

Reachability and coverage overview

Functions statically reachable by fuzzers

200 / 292

Cyclomatic complexity statically reachable by fuzzers

2293 / 3040

Runtime code coverage of functions

194 / 292

The following table shows data about each function in the project. The functions included in this table correspond to all functions that exist in the executables of the fuzzers. As such, there may be functions that are from third-party libraries.

For further technical details on the meaning of columns in the below table, please see the Glossary .

Func name	Functions filename	Args	Function call depth	Reached by Fuzzers	Fuzzers runtime hit	Func lines hit %	I Count	BB Count	Cyclomatic complexity	Functions reached	Reached by functions	Accumulated cyclomatic complexity	Undiscovered complexity

Fuzzer: spng_write_fuzzer

Call tree

The calltree shows the control flow of the fuzzer. This is overlaid with coverage information to display how much of the potential code a fuzzer can reach is in fact covered at runtime. In the following there is a link to a detailed calltree visualisation as well as a bitmap showing a high-level view of the calltree. For further information about these topics please see the glossary for full calltree and calltree overview

Call tree overview bitmap:

The distribution of callsites in terms of coloring is

Color	Runtime hitcount	Callsite count	Percentage
red	0	299	56.6%
gold	[1:9]	0	0.0%
yellow	[10:29]	5	0.94%
greenyellow	[30:49]	4	0.75%
lawngreen	50+	220	41.6%
All colors	528	100

Fuzz blockers

The followings are the branches where fuzzer fails to bypass.

Unique non-covered Complexity	Unique Reachable Complexities	Unique Reachable Functions	All non-covered Complexity	All Reachable Complexity	Function Name	Function Callsite	Blocked Branch
952	952	5 : View List ['decode_err', 'read_ihdr', 'is_critical_chunk', 'read_non_idat_chunks', 'discard_chunk_bytes']	952	952	read_chunks	call site: 00011	/src/libspng/spng/spng.c:3108
468	468	2 : View List ['compressBound', 'compress2']	519	2535	write_chunks_before_idat	call site: 00292	/src/libspng/spng/spng.c:4069
39	671	8 : View List ['finish_chunk', 'strlen', 'spng__deflate_init', 'write_header', 'deflate', 'spng__free', 'spng__malloc', 'deflateBound']	47	922	write_chunks_before_idat	call site: 00429	/src/libspng/spng/spng.c:4333
14	14	2 : View List ['crc_word_big', 'byte_swap']	14	14	crc32_z	call site: 00018	/src/zlib/crc32.c:731
8	8	1 : View List ['write_s32']	8	251	write_chunks_before_idat	call site: 00446	/src/libspng/spng/spng.c:4454
7	14	2 : View List ['_tr_align', '_tr_stored_block']	7	38	deflate	call site: 00375	/src/zlib/deflate.c:1211
4	455	3 : View List ['encode_err', 'write_header', 'deflate']	4	584	finish_idat	call site: 00491	/src/libspng/spng/spng.c:4536
2	2	1 : View List ['encode_err']	2	2	write_data	call site: 00261	/src/libspng/spng/spng.c:863
0	79	1 : View List ['write_chunk']	0	164	write_chunks_before_idat	call site: 00450	/src/libspng/spng/spng.c:4464
0	21	1 : View List ['crc32']	558	630	deflate	call site: 00330	/src/zlib/deflate.c:1160
0	21	1 : View List ['deflateEnd']	0	21	deflateInit2_	call site: 00297	/src/zlib/deflate.c:499
0	21	1 : View List ['crc32']	0	21	read_buf	call site: 00338	/src/zlib/deflate.c:227

Runtime coverage analysis

Covered functions

105

Functions that are reachable but not covered

50

Reachable functions

152

Percentage of reachable functions covered

67.11%

NB: The sum of covered functions and functions that are reachable but not covered need not be equal to Reachable functions . This is because the reachability analysis is an approximation and thus at runtime some functions may be covered that are not included in the reachability analysis. This is a limitation of our static analysis capabilities.

Function name	source code lines	source lines hit	percentage hit

Files reached

filename	functions hit
/src/libspng/tests/spng_write_fuzzer.c	2
/src/libspng/spng/spng.c	86
/src/zlib/crc32.c	5
/src/zlib/inflate.c	10
/src/zlib/adler32.c	2
/src/zlib/inftrees.c	1
/src/zlib/inffast.c	1
/src/zlib/compress.c	2
/src/zlib/deflate.c	17
/src/zlib/trees.c	20

Fuzzer: spng_read_fuzzer

Call tree

The calltree shows the control flow of the fuzzer. This is overlaid with coverage information to display how much of the potential code a fuzzer can reach is in fact covered at runtime. In the following there is a link to a detailed calltree visualisation as well as a bitmap showing a high-level view of the calltree. For further information about these topics please see the glossary for full calltree and calltree overview

Call tree overview bitmap:

The distribution of callsites in terms of coloring is

Color	Runtime hitcount	Callsite count	Percentage
red	0	32	7.39%
gold	[1:9]	4	0.92%
yellow	[10:29]	11	2.54%
greenyellow	[30:49]	4	0.92%
lawngreen	50+	382	88.2%
All colors	433	100

Fuzz blockers

The followings are the branches where fuzzer fails to bypass.

Unique non-covered Complexity	Unique Reachable Complexities	Unique Reachable Functions	All non-covered Complexity	All Reachable Complexity	Function Name	Function Callsite	Blocked Branch
14	14	2 : View List ['crc_word_big', 'byte_swap']	14	14	crc32_z	call site: 00023	/src/zlib/crc32.c:731
2	2	1 : View List ['memcmp']	2	2	trns_row	call site: 00397	/src/libspng/spng/spng.c:1822
0	474	6 : View List ['adler32', 'fixedtables', 'crc32', 'inflate_fast', 'updatewindow', 'inflate_table']	0	474	inflate	call site: 00163	/src/zlib/inflate.c:817
0	36	2 : View List ['crc32', 'adler32']	0	36	inflate	call site: 00172	/src/zlib/inflate.c:1255
0	4	2 : View List ['spng__iter_init', 'get_sample']	0	4	trns_row	call site: 00400	/src/libspng/spng/spng.c:1843
0	2	1 : View List ['get_sample']	0	2	unpack_scanline	call site: 00389	/src/libspng/spng/spng.c:2011
0	0	None	0	474	inflate	call site: 00151	/src/zlib/inflate.c:623
0	0	None	0	474	inflate	call site: 00151	/src/zlib/inflate.c:629
0	0	None	0	474	inflate	call site: 00153	/src/zlib/inflate.c:638
0	0	None	0	474	inflate	call site: 00153	/src/zlib/inflate.c:656
0	0	None	0	474	inflate	call site: 00169	/src/zlib/inflate.c:1189
0	0	None	0	474	inflate	call site: 00171	/src/zlib/inflate.c:1193

Runtime coverage analysis

Covered functions

124

Functions that are reachable but not covered

17

Reachable functions

136

Percentage of reachable functions covered

87.5%

NB: The sum of covered functions and functions that are reachable but not covered need not be equal to Reachable functions . This is because the reachability analysis is an approximation and thus at runtime some functions may be covered that are not included in the reachability analysis. This is a limitation of our static analysis capabilities.

Function name	source code lines	source lines hit	percentage hit

Files reached

filename	functions hit
/src/libspng/tests/spng_read_fuzzer.c	2
/src/libspng/spng/spng.c	99
/src/zlib/crc32.c	5
/src/zlib/inflate.c	10
/src/zlib/adler32.c	2
/src/zlib/inftrees.c	1
/src/zlib/inffast.c	1
/src/zlib/deflate.c	2

Fuzzer: spng_read_fuzzer_structure_aware

Call tree

The calltree shows the control flow of the fuzzer. This is overlaid with coverage information to display how much of the potential code a fuzzer can reach is in fact covered at runtime. In the following there is a link to a detailed calltree visualisation as well as a bitmap showing a high-level view of the calltree. For further information about these topics please see the glossary for full calltree and calltree overview

Call tree overview bitmap:

The distribution of callsites in terms of coloring is

Color	Runtime hitcount	Callsite count	Percentage
red	0	32	7.39%
gold	[1:9]	4	0.92%
yellow	[10:29]	14	3.23%
greenyellow	[30:49]	1	0.23%
lawngreen	50+	382	88.2%
All colors	433	100

Fuzz blockers

The followings are the branches where fuzzer fails to bypass.

Unique non-covered Complexity	Unique Reachable Complexities	Unique Reachable Functions	All non-covered Complexity	All Reachable Complexity	Function Name	Function Callsite	Blocked Branch
14	14	2 : View List ['crc_word_big', 'byte_swap']	14	14	crc32_z	call site: 00023	/src/zlib/crc32.c:731
2	2	1 : View List ['memcmp']	2	2	trns_row	call site: 00397	/src/libspng/spng/spng.c:1822
0	474	6 : View List ['adler32', 'fixedtables', 'crc32', 'inflate_fast', 'updatewindow', 'inflate_table']	0	474	inflate	call site: 00163	/src/zlib/inflate.c:817
0	36	2 : View List ['crc32', 'adler32']	0	36	inflate	call site: 00172	/src/zlib/inflate.c:1255
0	4	2 : View List ['spng__iter_init', 'get_sample']	0	4	trns_row	call site: 00400	/src/libspng/spng/spng.c:1843
0	2	1 : View List ['get_sample']	0	2	unpack_scanline	call site: 00389	/src/libspng/spng/spng.c:2011
0	0	None	0	474	inflate	call site: 00151	/src/zlib/inflate.c:623
0	0	None	0	474	inflate	call site: 00151	/src/zlib/inflate.c:629
0	0	None	0	474	inflate	call site: 00153	/src/zlib/inflate.c:638
0	0	None	0	474	inflate	call site: 00153	/src/zlib/inflate.c:656
0	0	None	0	474	inflate	call site: 00169	/src/zlib/inflate.c:1189
0	0	None	0	474	inflate	call site: 00171	/src/zlib/inflate.c:1193

Runtime coverage analysis

Covered functions

124

Functions that are reachable but not covered

17

Reachable functions

136

Percentage of reachable functions covered

87.5%

NB: The sum of covered functions and functions that are reachable but not covered need not be equal to Reachable functions . This is because the reachability analysis is an approximation and thus at runtime some functions may be covered that are not included in the reachability analysis. This is a limitation of our static analysis capabilities.

Function name	source code lines	source lines hit	percentage hit

Files reached

filename	functions hit
/src/libspng/tests/spng_read_fuzzer.c	2
/src/libspng/spng/spng.c	99
/src/zlib/crc32.c	5
/src/zlib/inflate.c	10
/src/zlib/adler32.c	2
/src/zlib/inftrees.c	1
/src/zlib/inffast.c	1
/src/zlib/deflate.c	2

Optimal target analysis

Remaining optimal interesting functions

The following table shows a list of functions that are optimal targets. Optimal targets are identified by finding the functions that in combination, yield a high code coverage.

Func name	Functions filename	Arg count	Args	Function depth	hitcount	instr count	bb count	cyclomatic complexity	Reachable functions	Incoming references	total cyclomatic complexity	Unreached complexity
LLVMFuzzerCustomCrossOver	/src/fuzzer-test-suite/libpng-1.2.56/png_mutator.h	7	['N/A', 'size_t', 'N/A', 'size_t', 'N/A', 'size_t', 'int']	12	0	188	27	20	90	0	989	206
deflate_slow	/src/zlib/deflate.c	2	['N/A', 'int']	5	0	1022	92	34	29	0	255	56

Implementing fuzzers that target the above functions will improve reachability such that it becomes:

Functions statically reachable by fuzzers

221 / 292

Cyclomatic complexity statically reachable by fuzzers

2551 / 3040

All functions overview

If you implement fuzzers for these functions, the status of all functions in the project will be:

Func name	Functions filename	Args	Function call depth	Reached by Fuzzers	Fuzzers runtime hit	Func lines hit %	I Count	BB Count	Cyclomatic complexity	Functions reached	Reached by functions	Accumulated cyclomatic complexity	Undiscovered complexity

This sections provides heuristics that can be used as input to a fuzz engine when running a given fuzz target. The current focus is on providing input that is usable by libFuzzer.

/src/libspng/tests/spng_write_fuzzer.c

Dictionary

Use this with the libFuzzer -dict=DICT.file flag

Fuzzer function priority

Use one of these functions as input to libfuzzer with flag: -focus_function name

-focus_function=['calculate_scanline_width', 'adler32', 'inflateEnd', 'deflate', 'spng__deflate_init', 'crc32_z', 'write_chunks_before_idat', 'spng_ctx_free']

/src/libspng/tests/spng_read_fuzzer.c

Dictionary

Use this with the libFuzzer -dict=DICT.file flag

Fuzzer function priority

Use one of these functions as input to libfuzzer with flag: -focus_function name

-focus_function=['adler32', 'crc32_z', 'inflate', 'trns_row', 'read_non_idat_chunks', 'LLVMFuzzerTestOneInput', 'spng_ctx_free']

/src/libspng/tests/spng_read_fuzzer.c

Dictionary

Use this with the libFuzzer -dict=DICT.file flag

Fuzzer function priority

Use one of these functions as input to libfuzzer with flag: -focus_function name

-focus_function=['adler32', 'crc32_z', 'inflate', 'trns_row', 'read_non_idat_chunks', 'LLVMFuzzerTestOneInput', 'spng_ctx_free']

This section shows analysis of runtime coverage data.

For futher technical details on how this section is generated, please see the Glossary .

Complex functions with low coverage

Func name	Function total lines	Lines covered at runtime	percentage covered	Reached by fuzzers
spng_set_option	78	27	34.61%	['spng_write_fuzzer', 'spng_read_fuzzer', 'spng_read_fuzzer_structure_aware']
write_chunks_before_idat	358	183	51.11%	['spng_write_fuzzer']
deflate	257	75	29.18%	['spng_write_fuzzer']

This section shows which files and directories are considered in this report. The main reason for showing this is fuzz introspector may include more code in the reasoning than is desired. This section helps identify if too many files/directories are included, e.g. third party code, which may be irrelevant for the threat model. In the event too much is included, fuzz introspector supports a configuration file that can exclude data from the report. See the following link for more information on how to create a config file: link

Files in report

Source file	Reached by	Covered by
	[]	[]
/src/zlib/crc32.c	['spng_write_fuzzer', 'spng_read_fuzzer', 'spng_read_fuzzer_structure_aware']	['spng_write_fuzzer', 'spng_read_fuzzer', 'spng_read_fuzzer_structure_aware']
/src/zlib/inffast.c	['spng_write_fuzzer', 'spng_read_fuzzer', 'spng_read_fuzzer_structure_aware']	['spng_read_fuzzer', 'spng_read_fuzzer_structure_aware']
/src/zlib/inftrees.c	['spng_write_fuzzer', 'spng_read_fuzzer', 'spng_read_fuzzer_structure_aware']	['spng_read_fuzzer', 'spng_read_fuzzer_structure_aware']
/src/libspng/tests/spng_write_fuzzer.c	['spng_write_fuzzer']	['spng_write_fuzzer']
/src/zlib/zutil.c	[]	[]
/src/zlib/adler32.c	['spng_write_fuzzer', 'spng_read_fuzzer', 'spng_read_fuzzer_structure_aware']	['spng_write_fuzzer', 'spng_read_fuzzer', 'spng_read_fuzzer_structure_aware']
/src/zlib/trees.c	['spng_write_fuzzer']	['spng_write_fuzzer']
/src/zlib/inflate.c	['spng_write_fuzzer', 'spng_read_fuzzer', 'spng_read_fuzzer_structure_aware']	['spng_write_fuzzer', 'spng_read_fuzzer', 'spng_read_fuzzer_structure_aware']
/src/zlib/compress.c	['spng_write_fuzzer']	[]
/src/libspng/tests/spng_read_fuzzer.c	['spng_read_fuzzer', 'spng_read_fuzzer_structure_aware']	['spng_read_fuzzer', 'spng_read_fuzzer_structure_aware']
/usr/local/bin/../include/c++/v1/stdexcept	[]	[]
/src/libspng/spng/spng.c	['spng_write_fuzzer', 'spng_read_fuzzer', 'spng_read_fuzzer_structure_aware']	['spng_write_fuzzer', 'spng_read_fuzzer', 'spng_read_fuzzer_structure_aware']
/src/zlib/uncompr.c	[]	[]
/src/zlib/deflate.c	['spng_write_fuzzer', 'spng_read_fuzzer', 'spng_read_fuzzer_structure_aware']	['spng_write_fuzzer']
/src/fuzzer-test-suite/libpng-1.2.56/png_mutator.h	[]	[]
/usr/local/bin/../include/c++/v1/__fwd/sstream.h	[]	[]

Directories in report

Directory
/src/zlib/
/usr/local/bin/../include/c++/v1/__fwd/
/usr/local/bin/../include/c++/v1/
/src/fuzzer-test-suite/libpng-1.2.56/
/src/libspng/spng/
/src/libspng/tests/