High level conclusions

Fuzzer fuzz_raw_format_filecontents is blocked:

The runtime code coverage of fuzz_raw_format_filecontents covers 4.214% of its statically reachable code. This means there is some place that blocks the fuzzer to continue exploring more code at run time.

Fuzzer fuzz_lib2to3_parse is blocked:

The runtime code coverage of fuzz_lib2to3_parse covers 0.0% of its statically reachable code. This means there is some place that blocks the fuzzer to continue exploring more code at run time.

Fuzzer fuzz_format_filecontents is blocked:

The runtime code coverage of fuzz_format_filecontents covers 4.942% of its statically reachable code. This means there is some place that blocks the fuzzer to continue exploring more code at run time.

Reachability and coverage overview

Functions statically reachable by fuzzers

103 / 373

Cyclomatic complexity statically reachable by fuzzers

461 / 1528

Runtime code coverage of functions

34 / 373

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	Runtime reached by Fuzzers	Combined 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: fuzz_format_filecontents

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	536	98.3%
gold	[1:9]	0	0.0%
yellow	[10:29]	0	0.0%
greenyellow	[30:49]	0	0.0%
lawngreen	50+	9	1.65%
All colors	545	100

Fuzz blockers

The following nodes represent call sites where fuzz blockers occur.

Amount of callsites blocked	Calltree index	Parent function	Callsite	Largest blocked function
462	82	black.parsing.lib2to3_parse	call site: 00082	black.check_stability_and_equivalence
64	0	EP	call site: 00000	black.format_file_contents
10	67	black.parsing.lib2to3_parse	call site: 00067	black.mode.supports_feature

Runtime coverage analysis

Covered functions

71

Functions that are reachable but not covered

250

Reachable functions

263

Percentage of reachable functions covered

4.94%

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
/	1
...fuzz_format_filecontents	5
black	60
black.handle_ipynb_magics	32
black.ranges	38
black.parsing	33
black.mode	1
black.nodes	23
black.comments	39
black.linegen	29
black.lines	39
black.trans	12
black.strings	5
black.brackets	9
black.output	7

Fuzzer: fuzz_lib2to3_parse

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	4	100.%
gold	[1:9]	0	0.0%
yellow	[10:29]	0	0.0%
greenyellow	[30:49]	0	0.0%
lawngreen	50+	0	0.0%
All colors	4	100

Fuzz blockers

The following nodes represent call sites where fuzz blockers occur.

Amount of callsites blocked	Calltree index	Parent function	Callsite	Largest blocked function
3	0	EP	call site: 00000	atheris.FuzzedDataProvider

Runtime coverage analysis

Covered functions

71

Functions that are reachable but not covered

4

Reachable functions

4

Percentage of reachable functions covered

0.0%

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.

Warning: The number of covered functions are larger than the number of reachable functions. This means that there are more functions covered at runtime than are extracted using static analysis. This is likely a result of the static analysis component failing to extract the right call graph or the coverage runtime being compiled with sanitizers in code that the static analysis has not analysed. This can happen if lto/gold is not used in all places that coverage instrumentation is used.

Function name	source code lines	source lines hit	percentage hit

Files reached

filename	functions hit
/	1
...fuzz_lib2to3_parse	3

Fuzzer: fuzz_raw_format_filecontents

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	535	98.3%
gold	[1:9]	0	0.0%
yellow	[10:29]	0	0.0%
greenyellow	[30:49]	0	0.0%
lawngreen	50+	9	1.65%
All colors	544	100

Fuzz blockers

The following nodes represent call sites where fuzz blockers occur.

Amount of callsites blocked	Calltree index	Parent function	Callsite	Largest blocked function
461	82	black.parsing.lib2to3_parse	call site: 00082	black.check_stability_and_equivalence
64	0	EP	call site: 00000	black.format_file_contents
10	67	black.parsing.lib2to3_parse	call site: 00067	black.mode.supports_feature

Runtime coverage analysis

Covered functions

71

Functions that are reachable but not covered

250

Reachable functions

261

Percentage of reachable functions covered

4.21%

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
/	1
...fuzz_raw_format_filecontents	4
black	60
black.handle_ipynb_magics	32
black.ranges	38
black.parsing	33
black.mode	1
black.nodes	23
black.comments	39
black.linegen	29
black.lines	39
black.trans	12
black.strings	5
black.brackets	9
black.output	7

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
black.main	black	29	['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A']	9	0	34	22	12	403	3	1412	485
black.trans.StringTransformer.__call__	black.trans	4	['N/A', 'N/A', 'N/A', 'N/A']	6	0	2	3	4	147	0	532	341
black.linegen.LineGenerator.visit_power	black.linegen	2	['N/A', 'N/A']	5	0	3	2	4	82	0	326	162
black.linegen._maybe_split_omitting_optional_parens	black.linegen	5	['N/A', 'N/A', 'N/A', 'N/A', 'N/A']	7	0	4	6	5	88	3	354	132
black.read_pyproject_toml	black	3	['N/A', 'N/A', 'N/A']	4	0	4	8	6	53	0	174	80
black.trans.BaseStringSplitter.do_match	black.trans	2	['N/A', 'N/A']	4	0	0	2	4	45	0	165	62
black.linegen.LineGenerator.visit_STRING	black.linegen	2	['N/A', 'N/A']	5	0	2	13	8	85	1	324	56
black.linegen.normalize_invisible_parens	black.linegen	4	['N/A', 'N/A', 'N/A', 'N/A']	3	0	11	17	10	67	3	252	43

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

Functions statically reachable by fuzzers

257 / 373

Cyclomatic complexity statically reachable by fuzzers

1126 / 1528

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	Runtime reached by Fuzzers	Combined 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/fuzz_format_filecontents.py

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=['black.parsing.lib2to3_parse']

/src/fuzz_lib2to3_parse.py

Dictionary

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

/src/fuzz_raw_format_filecontents.py

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=['black.parsing.lib2to3_parse']

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
black.main	77	0	0.0%	[]
black.get_sources	45	0	0.0%	[]
black.format_file_in_place	36	0	0.0%	[]
black.get_features_used	51	0	0.0%	['fuzz_raw_format_filecontents', 'fuzz_format_filecontents']
black.files.gen_python_files	32	0	0.0%	[]
re.match	1212	369	30.44%	['fuzz_raw_format_filecontents', 'fuzz_format_filecontents']
sources.update	1640	2	0.121%	['fuzz_raw_format_filecontents', 'fuzz_format_filecontents', 'fuzz_lib2to3_parse']
black.comments.convert_one_fmt_off_pair	51	0	0.0%	['fuzz_raw_format_filecontents', 'fuzz_format_filecontents']
black.comments._generate_ignored_nodes_from_fmt_skip	39	0	0.0%	['fuzz_raw_format_filecontents', 'fuzz_format_filecontents']
black.linegen.LineGenerator.visit_STRING	43	0	0.0%	[]
black.linegen._first_right_hand_split	53	0	0.0%	[]
black.linegen.normalize_invisible_parens	37	0	0.0%	[]
black.linegen.generate_trailers_to_omit	37	0	0.0%	[]
black.lines.EmptyLineTracker._maybe_empty_lines	45	0	0.0%	['fuzz_raw_format_filecontents', 'fuzz_format_filecontents']
black.lines.EmptyLineTracker._maybe_empty_lines_for_class_or_def	40	0	0.0%	['fuzz_raw_format_filecontents', 'fuzz_format_filecontents']
black.lines.is_line_short_enough	46	0	0.0%	['fuzz_raw_format_filecontents', 'fuzz_format_filecontents']
black.lines.can_omit_invisible_parens	37	0	0.0%	[]
blib2to3.pytree.Node.splitlines	482	156	32.36%	['fuzz_raw_format_filecontents', 'fuzz_format_filecontents']
black.nodes.whitespace	143	0	0.0%	['fuzz_raw_format_filecontents', 'fuzz_format_filecontents']
platformdirs.user_cache_dir	94	4	4.255%	['fuzz_raw_format_filecontents', 'fuzz_format_filecontents', 'fuzz_lib2to3_parse']
c.leaves	92	29	31.52%	['fuzz_format_filecontents']
pattern.search	56	25	44.64%	['fuzz_raw_format_filecontents', 'fuzz_format_filecontents', 'fuzz_lib2to3_parse']
match.groups	170	31	18.23%	['fuzz_raw_format_filecontents', 'fuzz_format_filecontents', 'fuzz_lib2to3_parse']
black.strings.normalize_string_quotes	42	0	0.0%	[]
black.strings.normalize_fstring_quotes	36	0	0.0%	[]
black.trans.StringMerger._merge_one_string_group.make_naked	55	0	0.0%	[]
black.trans.StringMerger._validate_msg	41	2	4.878%	['fuzz_raw_format_filecontents', 'fuzz_format_filecontents', 'fuzz_lib2to3_parse']
black.trans.StringParenStripper.do_match	34	0	0.0%	[]
black.trans.BaseStringSplitter._get_max_string_length	39	0	0.0%	[]
black.trans.iter_fexpr_spans	32	0	0.0%	[]
black.trans.StringSplitter.do_transform.more_splits_should_be_made	60	0	0.0%	[]
black.trans.StringParenWrapper.do_transform	74	12	16.21%	['fuzz_raw_format_filecontents', 'fuzz_format_filecontents', 'fuzz_lib2to3_parse']
black.brackets.BracketTracker.mark	31	0	0.0%	[]
i.strip	211	52	24.64%	['fuzz_raw_format_filecontents', 'fuzz_format_filecontents', 'fuzz_lib2to3_parse']

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
click	[]	[]
	[]	[]
pathspec	[]	[]
dataclasses	[]	[]
logging	[]	[]
black.handle_ipynb_magics	['fuzz_format_filecontents', 'fuzz_raw_format_filecontents']	[]
	[]	[]
black.ranges	['fuzz_format_filecontents', 'fuzz_raw_format_filecontents']	[]
black.brackets	['fuzz_format_filecontents', 'fuzz_raw_format_filecontents']	[]
multiprocessing	[]	[]
black.__main__	[]	[]
mypy_extensions	[]	[]
black.mode	['fuzz_format_filecontents', 'fuzz_raw_format_filecontents']	[]
black.report	[]	[]
warnings	[]	[]
platform	[]	[]
hashlib	[]	[]
...fuzz_lib2to3_parse	['fuzz_lib2to3_parse']	[]
tempfile	[]	[]
black.comments	['fuzz_format_filecontents', 'fuzz_raw_format_filecontents']	[]
io	[]	[]
sys	[]	[]
atheris	[]	[]
re	[]	[]
black.rusty	[]	[]
black.nodes	['fuzz_format_filecontents', 'fuzz_raw_format_filecontents']	[]
concurrent	[]	[]
black.concurrency	[]	[]
black.lines	['fuzz_format_filecontents', 'fuzz_raw_format_filecontents']	[]
black.parsing	['fuzz_format_filecontents', 'fuzz_raw_format_filecontents']	[]
tokenize_rt	[]	[]
uvloop	[]	[]
asyncio	[]	[]
operator	[]	[]
enum	[]	[]
datetime	[]	[]
black.numerics	[]	[]
black.resources	[]	[]
itertools	[]	[]
IPython	[]	[]
colorama	[]	[]
collections	[]	[]
_black_version	[]	[]
blib2to3	[]	[]
black	['fuzz_format_filecontents', 'fuzz_raw_format_filecontents']	[]
json	[]	[]
tokenize	[]	[]
black.schema	[]	[]
tomli	[]	[]
functools	[]	[]
packaging	[]	[]
black.strings	['fuzz_format_filecontents', 'fuzz_raw_format_filecontents']	[]
black._width_table	[]	[]
pathlib	[]	[]
...fuzz_raw_format_filecontents	['fuzz_raw_format_filecontents']	[]
black.output	['fuzz_format_filecontents', 'fuzz_raw_format_filecontents']	[]
black.debug	[]	[]
traceback	[]	[]
os	[]	[]
black.const	[]	[]
black.cache	[]	[]
typing	[]	[]
black.linegen	['fuzz_format_filecontents', 'fuzz_raw_format_filecontents']	[]
secrets	[]	[]
platformdirs	[]	[]
pickle	[]	[]
importlib	[]	[]
tomllib	[]	[]
difflib	[]	[]
ast	[]	[]
black.files	[]	[]
black.trans	['fuzz_format_filecontents', 'fuzz_raw_format_filecontents']	[]
...fuzz_format_filecontents	['fuzz_format_filecontents']	[]

Directories in report

Directory