High level conclusions

Fuzzer fuzz_url is blocked:

The runtime code coverage of fuzz_url covers 19.23% 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_api is blocked:

The runtime code coverage of fuzz_api covers 12.5% 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_decoders is blocked:

The runtime code coverage of fuzz_decoders covers 28.57% 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

16 / 417

Cyclomatic complexity statically reachable by fuzzers

66 / 1363

Runtime code coverage of functions

80 / 417

Warning: The number of runtime covered functions are larger than the number of reachable functions. This means that Fuzz Introspector found there are more functions covered at runtime than what is considered reachable based on the static analysis. This is a limitation in the analysis as anything covered at runtime is by definition reachable by the fuzzers.
This is likely due to a limitation in the static analysis. In this case, the count of functions covered at runtime is the true value, which means this is what should be considered "achieved" by the fuzzer.

Use the project functions table below to query all functions that were not covered at runtime.

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: fuzz_decoders

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	14	42.4%
gold	[1:9]	0	0.0%
yellow	[10:29]	0	0.0%
greenyellow	[30:49]	0	0.0%
lawngreen	50+	19	57.5%
All colors	33	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
7	25	httpx._decoders.TextChunker.decode	call site: 00025	httpx._decoders.TextDecoder.__init__
2	5	...fuzz_decoders.TestOneInput	call site: 00005	.len
2	8	httpx._decoders.ByteChunker.decode	call site: 00008	fdp.ConsumeIntInRange
2	22	...fuzz_decoders.TestOneInput	call site: 00022	.len
1	0	EP	call site: 00000	atheris.FuzzedDataProvider

Runtime coverage analysis

Covered functions

109

Functions that are reachable but not covered

15

Reachable functions

21

Percentage of reachable functions covered

28.57%

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_decoders	12
httpx._decoders	8

Fuzzer: fuzz_api

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	5	62.5%
gold	[1:9]	0	0.0%
yellow	[10:29]	0	0.0%
greenyellow	[30:49]	0	0.0%
lawngreen	50+	3	37.5%
All colors	8	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
4	3	...fuzz_api.ServerThread.__init__	call site: 00003	threading.Thread.start
1	0	EP	call site: 00000	...fuzz_api.ServerThread.__init__

Runtime coverage analysis

Covered functions

109

Functions that are reachable but not covered

7

Reachable functions

8

Percentage of reachable functions covered

12.5%

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.

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_api	7

Fuzzer: fuzz_url

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	47	55.2%
gold	[1:9]	0	0.0%
yellow	[10:29]	0	0.0%
greenyellow	[30:49]	0	0.0%
lawngreen	50+	38	44.7%
All colors	85	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
16	34	httpx._urlparse.urlparse	call site: 00034	kwargs.get
7	26	httpx._urlparse.quote	call site: 00026	httpx._urlparse.quote
5	10	httpx._urlparse.urlparse	call site: 00010	urllib.parse.urljoin.find
3	17	httpx._urlparse.urlparse	call site: 00017	re.finditer
3	65	httpx._urlparse.encode_host	call site: 00065	httpx._urlparse.quote
3	74	httpx._urlparse.validate_path	call site: 00074	httpx._urlparse.normalize_path
3	78	httpx._urlparse.normalize_path	call site: 00078	httpx._urlparse.quote
2	55	httpx._urlparse.urlparse	call site: 00055	kwargs.get
1	23	httpx._urlparse.percent_encoded	call site: 00023	httpx._urlparse.PERCENT
1	53	httpx._urlparse.urlparse	call site: 00053	AUTHORITY_REGEX.match
1	61	httpx._urlparse.urlparse	call site: 00061	IPv4_STYLE_HOSTNAME.match
1	63	httpx._urlparse.encode_host	call site: 00063	IPv6_STYLE_HOSTNAME.match

Runtime coverage analysis

Covered functions

108

Functions that are reachable but not covered

42

Reachable functions

52

Percentage of reachable functions covered

19.23%

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_url	3
httpx._urlparse	48

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
httpx._client.AsyncClient.send	httpx._client	5	['N/A', 'N/A', 'N/A', 'N/A', 'N/A']	7	0	4	2	4	237	9	772	598
httpx._main.main	httpx._main	17	['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']	6	0	7	3	4	136	0	446	182
httpx._auth.DigestAuth.auth_flow	httpx._auth	2	['N/A', 'N/A']	3	0	2	4	5	43	0	139	80
httpx._main.trace	httpx._main	3	['N/A', 'N/A', 'N/A']	4	0	10	8	6	26	0	85	67
httpx._transports.asgi.ASGITransport.handle_async_request	httpx._transports.asgi	2	['N/A', 'N/A']	8	0	2	3	4	95	0	302	37
httpx._client.Client.send	httpx._client	5	['N/A', 'N/A', 'N/A', 'N/A', 'N/A']	7	0	4	2	4	228	9	742	36

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

Functions statically reachable by fuzzers

147 / 417

Cyclomatic complexity statically reachable by fuzzers

528 / 1363

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/fuzz_decoders.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=['httpx._decoders.TextChunker.decode', '...fuzz_decoders.TestOneInput', 'httpx._decoders.ByteChunker.decode']

/src/fuzz_api.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=['...fuzz_api.ServerThread.__init__']

/src/fuzz_url.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=['httpx._urlparse.urlparse', 'httpx._urlparse.quote', 'httpx._urlparse.encode_host', 'httpx._urlparse.validate_path', 'httpx._urlparse.normalize_path', 'httpx._urlparse.percent_encoded']

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

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
	[]	[]
sniffio	[]	[]
httpx._decoders	['fuzz_decoders']	[]
io	[]	[]
	[]	[]
httpx._utils	[]	[]
datetime	[]	[]
mimetypes	[]	[]
inspect	[]	[]
httpx._transports.mock	[]	[]
click	[]	[]
httpx._status_codes	[]	[]
zstandard	[]	[]
httpx._client	[]	[]
logging	[]	[]
json	[]	[]
urllib	[]	[]
typing	[]	[]
pathlib	[]	[]
httpx._exceptions	[]	[]
httpx._transports.base	[]	[]
httpx._urlparse	['fuzz_url']	[]
threading	[]	[]
httpx._transports	[]	[]
trio	[]	[]
httpx._api	[]	[]
collections	[]	[]
httpx._models	[]	[]
httpx._auth	[]	[]
idna	[]	[]
asyncio	[]	[]
...fuzz_api	['fuzz_api']	[]
ssl	[]	[]
httpx._transports.asgi	[]	[]
certifi	[]	[]
re	[]	[]
base64	[]	[]
os	[]	[]
httpx._transports.default	[]	[]
ipaddress	[]	[]
brotlicffi	[]	[]
httpx._transports.wsgi	[]	[]
...fuzz_decoders	['fuzz_decoders']	[]
warnings	[]	[]
httpx	[]	[]
brotli	[]	[]
codecs	[]	[]
itertools	[]	[]
zlib	[]	[]
httpx._config	[]	[]
hashlib	[]	[]
sys	[]	[]
httpx._multipart	[]	[]
...fuzz_url	['fuzz_url']	[]
httpx._content	[]	[]
httpx._types	[]	[]
httpx._main	[]	[]
socket	[]	[]
httpcore	[]	[]
http	[]	[]
netrc	[]	[]
atheris	[]	[]
httpx._urls	[]	[]
httpx.__version__	[]	[]
time	[]	[]

Directories in report

Directory