Fuzz introspector
For issues and ideas: https://github.com/ossf/fuzz-introspector/issues
Project coverage

Table of contents

Project overview: filesystem_spec
High level conclusions
Reachability and coverage overview
Fuzzers overview
Project functions overview
Fuzzer details
Fuzzer: fuzz_http
Call tree
Fuzz blockers
Runtime coverage analysis
Files reached
Analyses and suggestions
Optimal target analysis
Remaining optimal interesting functions
All functions overview
Fuzz engine guidance
/src/fuzz_http.py
Dictionary
Fuzzer function priority
Runtime coverage analysis
Complex functions with low coverage
Files and Directories in report
Files in report
Directories in report
Metadata section
Report generation date: 2025-07-11

Project overview: filesystem_spec

High level conclusions

Reachability and coverage overview

Functions statically reachable by fuzzers
0.0%
0 / 2648
Cyclomatic complexity statically reachable by fuzzers
0.0%
0 / 9145
Runtime code coverage of functions
11.0%
285 / 2648

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.

Fuzzers overview

Fuzzer Fuzzer filename Functions Reached Functions unreached Fuzzer depth Files reached Basic blocks reached Cyclomatic complexity Details
fuzz_http /src/fuzz_http.py 10 4582 1 2 0 27 fuzz_http.py

Project functions overview

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 details

Fuzzer: fuzz_http

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

Full calltree

Call tree overview bitmap:

The distribution of callsites in terms of coloring is
Color Runtime hitcount Callsite count Percentage
red 0 3 23.0%
gold [1:9] 0 0.0%
yellow [10:29] 0 0.0%
greenyellow [30:49] 0 0.0%
lawngreen 50+ 10 76.9%
All colors 13 100

Fuzz blockers

The following nodes represent call sites where fuzz blockers occur.

Amount of callsites blocked Calltree index Parent function Callsite Largest blocked function
2 9 ...fuzz_http.TestOneInput call site: 00009 h.open
1 7 ...fuzz_http.TestOneInput call site: 00007 tmp_path.unlink

Runtime coverage analysis

Covered functions
411
Functions that are reachable but not covered
10
Reachable functions
10
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_http 9

Analyses and suggestions

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
fsspec.spec.AbstractFileSystem.get fsspec.spec 7 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 13 0 3 4 5 390 2 1289 1289
aiohttp.client.ClientSession._ws_connect aiohttp.client 23 ['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'] 10 0 6 18 10 329 1 1131 1062
fsspec.asyn.AsyncFileSystem._get fsspec.asyn 7 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 9 0 4 3 4 175 0 588 240
fsspec.implementations.reference.ReferenceFileSystem.get fsspec.implementations.reference 5 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 11 0 2 3 4 168 0 575 208
aiohttp.web_protocol.RequestHandler.connection_made aiohttp.web_protocol 2 ['N/A', 'N/A'] 6 0 3 2 4 75 0 260 193
aiohttp.web.main aiohttp.web 1 ['N/A'] 5 0 12 4 5 70 1 223 181
aiohttp.http_parser.HttpParser.feed_data aiohttp.http_parser 7 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 4 0 4 19 11 61 0 216 160

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

Functions statically reachable by fuzzers
13.0%
349 / 2648
Cyclomatic complexity statically reachable by fuzzers
15.0%
1414 / 9145

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

Fuzz engine guidance

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_http.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_http.TestOneInput']

Runtime coverage analysis

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
aiohttp.client_middleware_digest_auth.DigestAuthMiddleware._encode.KD 38 0 0.0% []
fsspec.spec.AbstractFileSystem.walk 39 0 0.0% []
fsspec.spec.AbstractFileSystem.glob 39 0 0.0% []
fsspec.spec.AbstractFileSystem.tree.format_bytes 43 0 0.0% []
fsspec.spec.AbstractBufferedFile.__init__ 32 2 6.25% ['fuzz_http']
fsspec.caching.MMapCache._fetch 34 0 0.0% []
fsspec.caching.BytesCache._fetch 51 0 0.0% []
fsspec.caching.BackgroundBlockCache._fetch 35 0 0.0% []
typing_extensions.ParamSpec 1787 513 28.70% ['fuzz_http']
ranges.append 31 7 22.58% ['fuzz_http']
out.raise_for_status 72 30 41.66% ['fuzz_http']
collections.abc.MutableMapping.values 234 76 32.47% ['fuzz_http']
fsspec.utils.infer_storage_options 33 0 0.0% []
fsspec.utils._translate 56 0 0.0% []
fsspec.asyn.AsyncFileSystem._walk 37 0 0.0% []
fsspec.asyn.AsyncFileSystem._glob 39 0 0.0% []
fsspec.implementations.local.LocalFileSystem.info 34 0 0.0% []
fsspec.implementations.local.make_path_posix 36 0 0.0% []
fsspec.implementations.http.HTTPFileSystem._ls_real 32 0 0.0% []
fsspec.implementations.http.HTTPFileSystem._glob 37 0 0.0% []
fsspec.core.get_fs_token_paths 37 0 0.0% []
aiohttp.multipart.parse_content_disposition.unescape 53 0 0.0% []
aiohttp.multipart.BodyPartReader._read_chunk_from_stream 32 0 0.0% []
aiohttp.client.ClientSession._request._connect_and_send_request 117 38 32.47% ['fuzz_http']
aiohttp.client.ClientSession._ws_connect 75 4 5.333% ['fuzz_http']
aiohttp.client_proto.ResponseHandler.connection_lost 38 0 0.0% []
aiohttp.client_proto.ResponseHandler.data_received 39 0 0.0% []
name.startswith 67 13 19.40% ['fuzz_http']
d.lstrip 67 8 11.94% ['fuzz_http']
fo.__enter__ 38 16 42.10% ['fuzz_http']
aiohttp.client_reqrep.ClientRequest.send 40 0 0.0% []
transport.writelines 153 47 30.71% ['fuzz_http']
url.endswith 204 60 29.41% ['fuzz_http']
aiohttp._websocket.writer.WebSocketWriter.send_frame 40 0 0.0% []
aiohttp._cookie_helpers.parse_set_cookie_headers 44 0 0.0% []
aiohttp.connector.BaseConnector._close 37 18 48.64% ['fuzz_http']
aiohttp.connector.BaseConnector.connect 33 13 39.39% ['fuzz_http']
aiohttp.connector.TCPConnector._resolve_host 41 0 0.0% []
aiohttp.connector.TCPConnector._start_tls_connection 40 0 0.0% []
aiohttp.connector.TCPConnector._create_direct_connection 39 7 17.94% ['fuzz_http']
aiohttp.connector.TCPConnector._create_proxy_connection 58 3 5.172% ['fuzz_http']
aiohttp.http_parser.HeadersParser.parse_headers 48 0 0.0% []
aiohttp.http_parser.HttpParser.feed_data.get_content_length 62 0 0.0% []
aiohttp.http_parser.HttpPayloadParser.feed_data 88 3 3.409% ['fuzz_http']
urllib3.fields.RequestField.make_multipart 93 20 21.50% ['fuzz_http']
aiohttp.cookiejar.CookieJar.update_cookies 46 2 4.347% ['fuzz_http']
aiohttp.cookiejar.CookieJar.filter_cookies 53 9 16.98% ['fuzz_http']
aiohttp.cookiejar.CookieJar._parse_date 50 6 12.0% ['fuzz_http']
aiohttp._websocket.helpers.ws_ext_parse 31 0 0.0% []
aiohttp.client_ws.ClientWebSocketResponse.close 40 0 0.0% []
aiohttp.client_ws.ClientWebSocketResponse.receive 56 0 0.0% []
frozenlist.FrozenList 58 31 53.44% ['fuzz_http']
request.config.getoption 108 49 45.37% ['fuzz_http']
it.__anext__ 49 11 22.44% ['fuzz_http']
methods.append 55 19 34.54% ['fuzz_http']
response.url.origin 658 142 21.58% ['fuzz_http']
aiohttp.http_writer.StreamWriter.write_eof 50 0 0.0% []
aiohttp.worker.GunicornWebWorker._run 37 0 0.0% []
requests.utils.super_len 32 0 0.0% []
requests.sessions.SessionRedirectMixin.resolve_redirects 50 0 0.0% []
requests.sessions.Session.send 36 0 0.0% []
requests.models.RequestEncodingMixin._encode_files 38 0 0.0% []
requests.models.PreparedRequest.prepare_url 39 0 0.0% []
requests.models.PreparedRequest.prepare_body 38 0 0.0% []
requests.auth.HTTPDigestAuth.build_digest_header.sha512_utf8 44 0 0.0% []
requests.adapters.HTTPAdapter.send 45 0 0.0% []
urllib3.util.ssl_.create_urllib3_context.load_verify_locations 181 82 45.30% ['fuzz_http']
urllib3.util.retry.Retry.from_int 175 61 34.85% ['fuzz_http']
urllib3.poolmanager.PoolManager.clear 244 87 35.65% ['fuzz_http']
urllib3.contrib.socks.SOCKSProxyManager 83 9 10.84% ['fuzz_http']
urllib3.filepost.encode_multipart_formdata 37 13 35.13% ['fuzz_http']
l.replace 119 13 10.92% ['fuzz_http']
gen.__anext__ 39 13 33.33% ['fuzz_http']
i.match 214 16 7.476% ['fuzz_http']

Files and Directories in report

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
[] []
requests.auth [] []
requests.sessions [] []
fsspec.implementations.dask [] []
dask [] []
concurrent [] []
async_timeout [] []
random [] []
aiohttp.http_writer [] []
fsspec.implementations.github [] []
socket [] []
aiohttp.client [] []
aiohttp.tcp_helpers [] []
requests.hooks [] []
aiohttp.multipart [] []
aiosignal [] []
asyncio [] []
io [] []
fsspec.implementations.cached [] []
math [] []
requests.cookies [] []
pathlib [] []
aiohttp.client_exceptions [] []
aiohttp.connector [] []
fsspec.exceptions [] []
weakref [] []
aiohttp.compression_utils [] []
aiohttp.cookiejar [] []
textwrap [] []
aiohttp.base_protocol [] []
requests.certs [] []
binascii [] []
distributed [] []
aiohttp.web_request [] []
mask [] []
aiohttp.pytest_plugin [] []
fsspec.archive [] []
stat [] []
fsspec.implementations.http_sync [] []
panel [] []
calendar [] []
posixpath [] []
charset_normalizer [] []
fsspec.implementations.memory [] []
aiohttp.web_response [] []
fsspec.implementations.dirfs [] []
fsspec.implementations.jupyter [] []
aiohttp.payload [] []
contextlib [] []
gzip [] []
ssl [] []
enum [] []
aiohttp.http_exceptions [] []
idna [] []
fsspec.config [] []
aiohttp.client_proto [] []
aiohttp.abc [] []
aiohttp.web_routedef [] []
configparser [] []
abc [] []
threading [] []
aiohttp._cookie_helpers [] []
os [] []
aiohttp._websocket.reader_c [] []
collections [] []
fsspec.implementations.cache_metadata [] []
time [] []
requests_kerberos [] []
atheris [] []
isal [] []
fsspec.json [] []
aiohttp.web_server [] []
aiohttp.client_ws [] []
requests.models [] []
fsspec.asyn [] []
struct [] []
fsspec.implementations.local [] []
fuse [] []
pyarrow [] []
tempfile [] []
numpy [] []
fsspec.registry [] []
fsspec.implementations [] []
requests.api [] []
yarl [] []
aiohttp [] []
pickle [] []
aiohttp.streams [] []
importlib [] []
aiohttp.web_runner [] []
aiohttp.web_urldispatcher [] []
pytest [] []
aiohttp.test_utils [] []
argparse [] []
fsspec.implementations.data [] []
mimetypes [] []
fsspec.parquet [] []
fsspec.implementations.ftp [] []
fsspec.implementations.libarchive [] []
fsspec._version [] []
dummy_threading [] []
secrets [] []
requests [] []
fsspec.compression [] []
aiohttp.hdrs [] []
ipaddress [] []
warnings [] []
types [] []
aiohttp._websocket [] []
fsspec.implementations.sftp [] []
shutil [] []
aiohttp.log [] []
brotlicffi [] []
fsspec.callbacks [] []
aiohappyeyeballs [] []
aiohttp.web_exceptions [] []
fsspec.implementations.zip [] []
requests.adapters [] []
fsspec.implementations.gist [] []
requests.exceptions [] []
uuid [] []
re [] []
paramiko [] []
fsspec.utils [] []
[] []
aiohttp.client_middlewares [] []
resource [] []
fsspec.generic [] []
fastparquet [] []
aiohttp.http_parser [] []
ClientSession [] []
aiohttp.web_fileresponse [] []
aiohttp._websocket.reader_py [] []
certifi [] []
fsspec.spec [] []
aiohttp.typedefs [] []
fsspec.implementations.git [] []
aiohttp.client_reqrep [] []
aiohttp.resolver [] []
_http_parser [] []
urllib3 [] []
platform [] []
chardet [] []
aiohttp.tracing [] []
tarfile [] []
requests._internal_utils [] []
fsspec [] []
mmap [] []
fsspec.dircache [] []
copy [] []
requests.packages [] []
aiohttp._websocket.reader [] []
ctypes [] []
libarchive [] []
aiohttp.helpers [] []
fsspec.implementations.tar [] []
aiohttp.http [] []
functools [] []
aiohttp._websocket.writer [] []
email [] []
aiohttp.web_ws [] []
aiodns [] []
fsspec.implementations.arrow [] []
aiohttp._websocket.models [] []
typing_extensions [] []
netrc [] []
aiohttp.client_middleware_digest_auth [] []
requests.__version__ [] []
gunicorn [] []
fsspec.implementations.webhdfs [] []
http [] []
heapq [] []
smbclient [] []
fsspec.conftest [] []
fsspec.caching [] []
ftplib [] []
fsspec.transaction [] []
typing [] []
zstandard [] []
traceback [] []
fsspec.implementations.reference [] []
jinja2 [] []
fsspec.implementations.http [] []
zipfile [] []
datetime [] []
fsspec.gui [] []
ujson [] []
aiohttp.web_log [] []
aiohttp.formdata [] []
uvloop [] []
fsspec.core [] []
aiohttp.web [] []
pygit2 [] []
html [] []
gc [] []
base64 [] []
ast [] []
fsspec.implementations.asyn_wrapper [] []
itertools [] []
aiohttp.http_websocket [] []
snappy [] []
sys [] []
subprocess [] []
fsspec.implementations.dbfs [] []
frozenlist [] []
...fuzz_http ['fuzz_http'] []
codecs [] []
logging [] []
aiohttp.web_middlewares [] []
pandas [] []
inspect [] []
glob [] []
json [] []
keyword [] []
cryptography [] []
aiohttp.web_app [] []
fsspec.implementations.cache_mapper [] []
requests.utils [] []
requests.status_codes [] []
winreg [] []
multidict [] []
hashlib [] []
attr [] []
aiohttp.worker [] []
aiohttp.web_protocol [] []
aiohttp._websocket.helpers [] []
simplejson [] []
signal [] []
operator [] []
js [] []
fsspec.implementations.smb [] []
aiohttp.payload_streamer [] []
requests.structures [] []
urllib [] []
brotli [] []
requests.compat [] []
unittest [] []
fsspec.mapping [] []
fsspec.fuse [] []
requests.help [] []

Directories in report

Directory

Metadata section

This sections shows the raw data that is used to produce this report. This is mainly used for further processing and developer debugging.

Fuzzer Calltree file Program data file Coverage file
fuzz_http fuzzerLogFile-fuzz_http.data fuzzerLogFile-fuzz_http.data.yaml all_cov.json