High level conclusions

Fuzzer load is blocked:

The runtime code coverage of load covers 29.03% of its statically reachable code. This means there is some place that blocks the fuzzer to continue exploring more code at run time.

Fuzzer scan is blocked:

The runtime code coverage of scan covers 27.27% of its statically reachable code. This means there is some place that blocks the fuzzer to continue exploring more code at run time.

Fuzzers reach 0.729% of cyclomatic complexity.

Fuzzers reach 4.950% of all functions.

Reachability and coverage overview

Functions statically reachable by fuzzers

15 / 303

Cyclomatic complexity statically reachable by fuzzers

12 / 1644

Runtime code coverage of functions

130 / 303

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: scan

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	155	14.9%
gold	[1:9]	15	1.44%
yellow	[10:29]	13	1.25%
greenyellow	[30:49]	11	1.05%
lawngreen	50+	846	81.3%
All colors	1040	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
11	540	yaml_parser_roll_indent	call site: 00540	yaml_queue_extend
10	778	yaml_parser_scan_flow_scalar	call site: 00778
7	360	api::yaml_string_extend	call site: 00360
7	415	yaml_parser_scan_uri_escapes	call site: 00415
6	49	externs::memcmp	call site: 00049
6	229	externs::strcmp	call site: 00229
6	406	yaml_parser_scan_uri_escapes	call site: 00406
5	1019	yaml_parser_delete	call site: 01019	yaml_free
4	1025	yaml_parser_delete	call site: 01025	yaml_free
3	131	yaml_parser_scan_to_next_token	call site: 00131
3	204	yaml_parser_scan_directive_name	call site: 00204	yaml_malloc
3	223	externs::strcmp	call site: 00223

Runtime coverage analysis

Covered functions

91

Functions that are reachable but not covered

24

Reachable functions

33

Percentage of reachable functions covered

27.27%

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
fuzz/fuzz_targets/scan.rs	10
src/api.rs	36
src/scanner.rs	95
src/lib.rs	9
src/ops.rs	4
src/reader.rs	9
src/macros.rs	27
src/dumper.rs	1

Fuzzer: 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	170	12.1%
gold	[1:9]	15	1.07%
yellow	[10:29]	12	0.85%
greenyellow	[30:49]	14	1.00%
lawngreen	50+	1185	84.8%
All colors	1396	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
11	543	yaml_parser_roll_indent	call site: 00543	yaml_queue_extend
10	781	yaml_parser_scan_flow_scalar	call site: 00781
7	363	api::yaml_string_extend	call site: 00363
7	418	yaml_parser_scan_uri_escapes	call site: 00418
6	52	externs::memcmp	call site: 00052
6	232	externs::strcmp	call site: 00232
6	409	yaml_parser_scan_uri_escapes	call site: 00409
5	1379	unsafe_libyaml::yaml_parser_delete	call site: 01379	yaml_free
4	1061	yaml_parser_process_directives	call site: 01061	yaml_free
3	134	yaml_parser_scan_to_next_token	call site: 00134
3	207	yaml_parser_scan_directive_name	call site: 00207	yaml_malloc
3	226	externs::strcmp	call site: 00226

Runtime coverage analysis

Covered functions

117

Functions that are reachable but not covered

16

Reachable functions

24

Percentage of reachable functions covered

33.33%

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
fuzz/fuzz_targets/parse.rs	10
src/api.rs	43
src/parser.rs	50
src/lib.rs	9
src/scanner.rs	93
src/ops.rs	5
src/reader.rs	9
src/macros.rs	28
src/dumper.rs	1

Fuzzer: load

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	185	12.1%
gold	[1:9]	12	0.78%
yellow	[10:29]	15	0.98%
greenyellow	[30:49]	16	1.04%
lawngreen	50+	1297	85.0%
All colors	1525	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
11	552	yaml_parser_roll_indent	call site: 00552	yaml_queue_extend
10	790	yaml_parser_scan_flow_scalar	call site: 00790
7	372	api::yaml_string_extend	call site: 00372
7	427	yaml_parser_scan_uri_escapes	call site: 00427
6	61	externs::memcmp	call site: 00061
6	241	externs::strcmp	call site: 00241
6	418	yaml_parser_scan_uri_escapes	call site: 00418
5	1508	unsafe_libyaml::yaml_parser_delete	call site: 01508	yaml_free
4	1067	yaml_parser_process_directives	call site: 01067	yaml_free
3	15	unsafe_libyaml::yaml_parser_load	call site: 00015	yaml_malloc
3	143	yaml_parser_scan_to_next_token	call site: 00143
3	216	yaml_parser_scan_directive_name	call site: 00216	yaml_malloc

Runtime coverage analysis

Covered functions

135

Functions that are reachable but not covered

22

Reachable functions

31

Percentage of reachable functions covered

29.03%

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
fuzz/fuzz_targets/load.rs	11
src/api.rs	44
src/loader.rs	39
src/lib.rs	9
src/macros.rs	28
src/parser.rs	50
src/scanner.rs	93
src/ops.rs	5
src/reader.rs	9
src/dumper.rs	1

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

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

Functions statically reachable by fuzzers

15 / 303

Cyclomatic complexity statically reachable by fuzzers

12 / 1644

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.

fuzz/fuzz_targets/scan.rs

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=['yaml_parser_roll_indent', 'yaml_parser_scan_flow_scalar', 'api::yaml_string_extend', 'yaml_parser_scan_uri_escapes', 'externs::memcmp', 'externs::strcmp', 'yaml_parser_delete', 'yaml_parser_scan_to_next_token']

fuzz/fuzz_targets/parse.rs

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=['yaml_parser_roll_indent', 'yaml_parser_scan_flow_scalar', 'api::yaml_string_extend', 'yaml_parser_scan_uri_escapes', 'externs::memcmp', 'externs::strcmp', 'unsafe_libyaml::yaml_parser_delete', 'yaml_parser_process_directives', 'yaml_parser_scan_to_next_token']

fuzz/fuzz_targets/load.rs

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=['yaml_parser_roll_indent', 'yaml_parser_scan_flow_scalar', 'api::yaml_string_extend', 'yaml_parser_scan_uri_escapes', 'externs::memcmp', 'externs::strcmp', 'unsafe_libyaml::yaml_parser_delete', 'yaml_parser_process_directives', 'unsafe_libyaml::yaml_parser_load']

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

New fuzzers

The below fuzzers are templates and suggestions for how to target the set of optimal functions above

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/unsafe-libyaml/src/scanner.rs	['scan', 'parse', 'load']	['scan', 'parse', 'load']
/src/unsafe-libyaml/src/dumper.rs	['scan', 'parse', 'load']	[]
/src/unsafe-libyaml/src/lib.rs	['scan', 'parse', 'load']	['scan', 'parse', 'load']
/src/unsafe-libyaml/src/bin/run-parser-test-suite.rs	[]	[]
/src/unsafe-libyaml/src/macros.rs	['scan', 'parse', 'load']	[]
/src/unsafe-libyaml/src/bin/cstr/mod.rs	[]	[]
/src/unsafe-libyaml/src/loader.rs	['load']	['load']
/src/unsafe-libyaml/src/bin/run-emitter-test-suite.rs	[]	[]
/src/unsafe-libyaml/src/ops.rs	['scan', 'parse', 'load']	['scan', 'parse', 'load']
/src/unsafe-libyaml/src/yaml.rs	[]	[]
/src/unsafe-libyaml/fuzz/fuzz_targets/parse.rs	['parse']	['parse']
/src/unsafe-libyaml/src/emitter.rs	[]	[]
/src/unsafe-libyaml/fuzz/fuzz_targets/load.rs	['load']	['load']
/src/unsafe-libyaml/src/api.rs	['scan', 'parse', 'load']	['scan', 'parse', 'load']
/src/unsafe-libyaml/tests/data/lib.rs	[]	[]
/src/unsafe-libyaml/src/writer.rs	[]	[]
/src/unsafe-libyaml/src/success.rs	[]	[]
/src/unsafe-libyaml/fuzz/fuzz_targets/scan.rs	['scan']	['scan']
/src/unsafe-libyaml/src/reader.rs	['scan', 'parse', 'load']	['scan', 'parse', 'load']
/src/unsafe-libyaml/src/parser.rs	['parse', 'load']	['parse', 'load']
/src/unsafe-libyaml/tests/bin/mod.rs	[]	[]
/src/unsafe-libyaml/tests/data/build.rs	[]	[]

Directories in report

Directory
/src/unsafe-libyaml/tests/data/
/src/unsafe-libyaml/fuzz/fuzz_targets/
/src/unsafe-libyaml/src/bin/cstr/
/src/unsafe-libyaml/tests/bin/
/src/unsafe-libyaml/src/
/src/unsafe-libyaml/src/bin/

This section shows a list of 3rd party function calls and their relative coverage information. By static analysis of the target project code, all of the 3rd party function call and their caller information, including the source file and line number that initiate the call are captured. The caller source code file and line number are shown in column 2 while column 1 is the function name of the 3rd party function call. Each occurrent of the 3rd party function call will occuply a separate row. Column 3 of each row indicate if the 3rd party call in the source file line is unreachable. Column 4 lists all fuzzers that have covered that particular system call in that specific location (source file and line)during their dynamic fuzzing.

Function in each files in report

Target sink	Callsite location	Reached by fuzzer	Covered by Fuzzers