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

Table of contents

Project overview: python-pypdf
High level conclusions
Reachability and coverage overview
Fuzzers overview
Project functions overview
Fuzzer details
Fuzzer: fuzz_encryption
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_encryption.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: 2025-11-15

Project overview: python-pypdf

High level conclusions

Reachability and coverage overview

Functions statically reachable by fuzzers
22.0%
187 / 848
Cyclomatic complexity statically reachable by fuzzers
23.0%
717 / 3123
Runtime code coverage of functions
25.0%
216 / 848

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_encryption /src/fuzz_encryption.py 387 1171 14 15 413 1314 fuzz_encryption.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_encryption

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 1127 63.9%
gold [1:9] 0 0.0%
yellow [10:29] 0 0.0%
greenyellow [30:49] 0 0.0%
lawngreen 50+ 636 36.0%
All colors 1763 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
220 1295 pypdf._writer.PdfWriter.write_stream call site: 01295 pypdf._writer.PdfWriter.write
139 1110 pypdf._reader.PdfReader.get_object call site: 01110 pypdf._doc_common.PdfDocCommon._flatten
84 232 pypdf.generic._data_structures.DictionaryObject.read_from_stream call site: 00232 pypdf._reader.PdfReader.read
73 694 pypdf._reader.PdfReader.cache_indirect_object call site: 00694 pypdf._reader.PdfReader._rebuild_xref_table
62 1047 pypdf._encryption.Encryption._make_crypt_filter call site: 01047 pypdf._reader.PdfReader.read
56 391 pypdf.generic._data_structures.ArrayObject.read_from_stream call site: 00391 pypdf.generic._base.BooleanObject.read_from_stream
53 828 pypdf._crypt_providers._fallback.CryptRC4.encrypt call site: 00828 pypdf._encryption.AlgV4.verify_user_password
32 575 pypdf._reader.PdfReader.read_object_header call site: 00575 pypdf.generic._data_structures.read_object
24 627 pypdf._reader.PdfReader._read_standard_xref_table call site: 00627 pypdf._reader.PdfReader.read
21 978 pypdf.generic._base.IndirectObject.get_object call site: 00978 pypdf._utils.read_non_whitespace
20 521 pypdf._reader.PdfReader._read_standard_xref_table call site: 00521 pypdf._reader.PdfReader._rebuild_xref_table
17 676 pypdf._reader.PdfReader._read_xref call site: 00676 pypdf._reader.PdfReader._read_pdf15_xref_stream

Runtime coverage analysis

Covered functions
277
Functions that are reachable but not covered
280
Reachable functions
387
Percentage of reachable functions covered
27.65%
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_encryption 9
pypdf._writer 106
pypdf._reader 86
pypdf._utils 19
pypdf.generic._data_structures 83
pypdf.generic._base 36
pypdf.generic._utils 26
pypdf._doc_common 10
pypdf._encryption 88
pypdf._crypt_providers._fallback 7
pypdf._crypt_providers._cryptography 17
pypdf._crypt_providers._pycryptodome 7
pypdf._page 9
pypdf.filters 59

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
pypdf._writer.PdfWriter.update_page_form_field_values pypdf._writer 6 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 83 0 6 23 12 299 1 1047 264
pypdf._writer.PdfWriter.append pypdf._writer 6 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 81 0 3 4 5 297 0 1048 250
pypdf._page.VirtualListImages.__getitem__ pypdf._page 2 ['N/A', 'N/A'] 85 0 0 5 5 293 0 1028 240
pypdf.xmp.XmpInformation.dc_date pypdf.xmp 2 ['N/A', 'N/A'] 4 0 4 2 4 50 0 159 144
pypdf._text_extraction._layout_mode._fixed_width_page.text_show_operations pypdf._text_extraction._layout_mode._fixed_width_page 4 ['N/A', 'N/A', 'N/A', 'N/A'] 5 0 10 6 5 49 0 163 115
pypdf._page.PageObject.extract_text pypdf._page 9 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 84 0 2 13 8 292 0 1019 83
pypdf._page.PageObject._merge_page pypdf._page 6 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 84 0 12 9 7 267 5 929 77
pypdf._doc_common.PdfDocCommon.get_form_text_fields pypdf._doc_common 2 ['N/A', 'N/A'] 8 0 1 3 4 37 0 125 76
pypdf.generic._data_structures.ContentStream._parse_content_stream pypdf.generic._data_structures 2 ['N/A', 'N/A'] 80 0 5 4 5 132 1 484 67
pypdf._writer.PdfWriter.remove_text pypdf._writer 2 ['N/A', 'N/A'] 85 0 3 4 5 256 0 897 54

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

Functions statically reachable by fuzzers
40.0%
341 / 848
Cyclomatic complexity statically reachable by fuzzers
46.0%
1421 / 3123

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_encryption.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=['pypdf._writer.PdfWriter.write_stream', 'pypdf._reader.PdfReader.get_object', 'pypdf.generic._data_structures.DictionaryObject.read_from_stream', 'pypdf._reader.PdfReader.cache_indirect_object', 'pypdf._encryption.Encryption._make_crypt_filter', 'pypdf.generic._data_structures.ArrayObject.read_from_stream', 'pypdf._crypt_providers._fallback.CryptRC4.encrypt', 'pypdf._reader.PdfReader.read_object_header', 'pypdf._reader.PdfReader._read_standard_xref_table', 'pypdf.generic._base.IndirectObject.get_object']

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
pypdf._writer.PdfWriter.__init__._get_clone_from 37 17 45.94% ['fuzz_encryption']
pypdf._writer.PdfWriter._add_page 33 0 0.0% []
pypdf._writer.PdfWriter.update_page_form_field_values 63 0 0.0% []
pypdf._writer.PdfWriter._write_increment 34 0 0.0% ['fuzz_encryption']
pypdf._writer.PdfWriter.compress_identical_objects.replace_in_obj 39 0 0.0% []
pypdf._writer.PdfWriter.remove_objects_from_page.clean_forms 41 0 0.0% []
pypdf._writer.PdfWriter.merge._process_named_dests 53 0 0.0% []
pypdf._writer.PdfWriter._insert_filtered_annotations 36 0 0.0% []
pypdf._reader.PdfReader.get_object 75 22 29.33% ['fuzz_encryption']
pypdf._reader.PdfReader.read 41 19 46.34% ['fuzz_encryption']
pypdf._reader.PdfReader._rebuild_xref_table 39 0 0.0% ['fuzz_encryption']
Crypto.Cipher.ARC4.ARC4Cipher 36 10 27.77% ['fuzz_encryption']
Crypto.Util.Padding.pad.encode 36 8 22.22% ['fuzz_encryption']
pypdf.generic._appearance_stream.TextStreamAppearance._scale_text 43 0 0.0% []
pypdf.generic._appearance_stream.TextStreamAppearance._generate_appearance_stream_data 38 0 0.0% []
pypdf.generic._appearance_stream.TextStreamAppearance.from_text_annotation 42 0 0.0% []
pypdf._page.PageObject._merge_resources.compute_unique_key 33 0 0.0% []
pypdf._page.PageObject._merge_page 52 0 0.0% []
pypdf._page.PageObject._merge_page_writer 70 0 0.0% []
pypdf._page.PageObject._extract_text 74 0 0.0% []
pypdf._page._VirtualList.__delitem__ 36 0 0.0% []
pypdf.generic._data_structures.DictionaryObject._clone 50 0 0.0% []
pypdf.generic._data_structures.DictionaryObject.read_from_stream.read_unsized_from_stream 101 30 29.70% ['fuzz_encryption']
pypdf.generic._data_structures.TreeObject.insert_child 38 0 0.0% []
pypdf.generic._data_structures.ContentStream._read_inline_image 51 0 0.0% []
pypdf.generic._data_structures.Destination.__init__ 32 0 0.0% []
pypdf.filters.FlateDecode.decode 34 0 0.0% ['fuzz_encryption']
pypdf.filters.FlateDecode._decode_png_prediction 46 0 0.0% ['fuzz_encryption']
pypdf.filters.decode_stream_data 38 0 0.0% ['fuzz_encryption']
pypdf.filters._xobj_to_image._apply_alpha 79 0 0.0% []
pypdf.generic._image_inline.extract_inline_AHx 31 0 0.0% []
pypdf.generic._image_inline.extract_inline_DCT.read 31 0 0.0% []
pypdf.generic._image_inline.extract_inline_default 32 0 0.0% []
pypdf.generic._utils.read_string_from_stream 43 0 0.0% ['fuzz_encryption']
pypdf._codecs._codecs.LzwCodec.decode 38 0 0.0% []
pypdf._doc_common.PdfDocCommon._get_named_destinations 46 0 0.0% []
pypdf._doc_common.PdfDocCommon.get_pages_showing_field._get_inherited 39 2 5.128% ['fuzz_encryption']
pypdf._doc_common.PdfDocCommon._build_outline_item 46 0 0.0% []
pypdf._doc_common.PdfDocCommon._flatten 36 0 0.0% ['fuzz_encryption']
pypdf._cmap._parse_encoding 40 0 0.0% []
pypdf._cmap.parse_bfrange 35 0 0.0% []
pypdf._cmap.build_font_width_map 60 0 0.0% []
pypdf._text_extraction._layout_mode._fixed_width_page.recurs_to_target_op 84 0 0.0% []
pypdf._text_extraction._layout_mode._font.Font.__post_init__ 34 0 0.0% []
pypdf._text_extraction.crlf_space_check 37 0 0.0% []

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
[] []
pypdf.generic._outline [] []
pypdf._page ['fuzz_encryption'] []
pypdf._reader ['fuzz_encryption'] []
pypdf._protocols [] []
mult [] []
binascii [] []
hashlib [] []
pypdf.generic [] []
decimal [] []
pypdf.generic._utils ['fuzz_encryption'] []
pypdf.pagerange [] []
pypdf.generic._image_inline [] []
subprocess [] []
pypdf.generic._appearance_stream [] []
pypdf.annotations._non_markup_annotations [] []
crlf_space_check [] []
re [] []
get_text_operands [] []
pypdf._version [] []
pypdf.generic._data_structures ['fuzz_encryption'] []
bisect [] []
warnings [] []
pypdf._crypt_providers._fallback ['fuzz_encryption'] []
pypdf.annotations._base [] []
zlib [] []
pathlib [] []
pypdf._codecs [] []
cryptography [] []
pypdf._codecs.zapfding [] []
pypdf.generic._files [] []
pypdf._text_extraction._text_extractor [] []
pypdf.generic._base ['fuzz_encryption'] []
struct [] []
pypdf._codecs.pdfdoc [] []
os [] []
pypdf._crypt_providers._cryptography ['fuzz_encryption'] []
[] []
datetime [] []
pypdf.errors [] []
pypdf.filters ['fuzz_encryption'] []
json [] []
pypdf._codecs.std [] []
base64 [] []
pypdf.generic._link [] []
pypdf._encryption ['fuzz_encryption'] []
tempfile [] []
enum [] []
get_display_str [] []
_codecs [] []
pypdf.generic._fit [] []
pypdf._text_extraction._layout_mode._fixed_width_page [] []
pypdf.types [] []
shutil [] []
dataclasses [] []
pypdf._text_extraction._layout_mode._text_state_params [] []
pypdf [] []
uuid [] []
pypdf._codecs._codecs [] []
pypdf.generic._viewerpref [] []
...fuzz_encryption ['fuzz_encryption'] []
secrets [] []
pypdf._crypt_providers._pycryptodome ['fuzz_encryption'] []
pypdf._font [] []
typing [] []
pypdf._text_extraction._layout_mode._font [] []
pypdf._utils ['fuzz_encryption'] []
pypdf._cmap [] []
pypdf.xmp [] []
io [] []
pypdf._crypt_providers._base [] []
pypdf.papersizes [] []
pypdf._writer ['fuzz_encryption'] []
itertools [] []
Crypto [] []
pypdf._xobj_image_helpers [] []
pypdf._text_extraction._layout_mode._text_state_manager [] []
pypdf._codecs.symbol [] []
atheris [] []
pypdf._text_extraction._layout_mode [] []
pypdf._codecs.adobe_glyphs [] []
pypdf._text_extraction._layout_mode._font_widths [] []
xml [] []
pypdf.annotations._markup_annotations [] []
pypdf.generic._rectangle [] []
pypdf.constants [] []
pypdf._crypt_providers [] []
pypdf._text_extraction [] []
math [] []
pypdf._page_labels [] []
pypdf.annotations [] []
logging [] []
collections [] []
pypdf._doc_common ['fuzz_encryption'] []
pypdf._codecs.core_fontmetrics [] []
PIL [] []

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_encryption fuzzerLogFile-fuzz_encryption.data fuzzerLogFile-fuzz_encryption.data.yaml all_cov.json