High level conclusions

Fuzzer fuzz/fuzz-asn1.c is blocked:

The runtime code coverage of fuzz/fuzz-asn1.c covers 19.04% 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 34.02% of cyclomatic complexity.

Fuzzers reach 24.16% of all functions.

Reachability and coverage overview

Functions statically reachable by fuzzers

144 / 596

Cyclomatic complexity statically reachable by fuzzers

1596 / 4690

Runtime code coverage of functions

152 / 596

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	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-server-hello

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	306	63.8%
gold	[1:9]	3	0.62%
yellow	[10:29]	8	1.67%
greenyellow	[30:49]	0	0.0%
lawngreen	50+	162	33.8%
All colors	479	100

Fuzz blockers

The followings are the branches where fuzzer fails to bypass.

Unique non-covered Complexity	Unique Reachable Complexities	Unique Reachable Functions	All non-covered Complexity	All Reachable Complexity	Function Name	Function Callsite	Blocked Branch
698	1383	14 : View List ['derive_secret', 'ptls_buffer__adjust_quic_blocksize', 'send_certificate_verify', 'setup_traffic_protection', 'send_certificate', 'commission_handshake_secret', 'ptls_buffer__do_pushv', 'derive_exporter_secret', 'ptls__key_schedule_update_hash', 'push_change_cipher_spec', 'send_finished', 'ptls_iovec_init', 'key_schedule_extract', 'free']	698	1383	client_handle_finished	call site: 00000	/src/picotls/lib/picotls.c:3455
210	210	2 : View List ['client_ech_select_hello', 'free']	210	1259	client_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:2828
210	210	1 : View List ['client_ech_select_hello']	210	852	client_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:2848
82	164	2 : View List ['derive_secret_with_empty_digest', 'calc_verify_data']	345	1587	send_client_hello	call site: 00256	/src/picotls/lib/picotls.c:2472
73	73	1 : View List ['buffer_encrypt_record']	73	73	commit_record_message	call site: 00000	/src/picotls/lib/picotls.c:867
47	277	2 : View List ['setup_traffic_protection', 'push_change_cipher_spec']	255	485	send_client_hello	call site: 00299	/src/picotls/lib/picotls.c:2554
8	930	8 : View List ['ptls_buffer_reserve', 'encode_client_hello', 'strlen', 'ptls__key_schedule_update_hash', 'outer_ech_header_size', 'ptls_iovec_init', 'malloc', 'ptls_aead_encrypt']	263	1415	send_client_hello	call site: 00289	/src/picotls/lib/picotls.c:2484
7	107	7 : View List ['client_do_handle_certificate', 'ptls_decode16', 'ptls_decode_quicint', 'ptls__key_schedule_update_hash', 'ptls_iovec_init', 'malloc', 'ptls_decode24']	7	107	client_handle_compressed_certificate	call site: 00000	/src/picotls/lib/picotls.c:3332
5	7	2 : View List ['ptls_is_server', 'ptls_is_ech_handshake']	5	7	handle_certificate	call site: 00000	/src/picotls/lib/picotls.c:3279
2	2	1 : View List ['posix_memalign']	2	5	ptls_buffer_reserve_aligned	call site: 00044	/src/picotls/lib/picotls.c:598
0	87	1 : View List ['key_schedule_extract']	0	87	key_schedule_select_cipher	call site: 00000	/src/picotls/lib/picotls.c:1364
0	82	2 : View List ['derive_secret', 'malloc']	0	82	client_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:2886

Runtime coverage analysis

Covered functions

108

Functions that are reachable but not covered

78

Reachable functions

140

Percentage of reachable functions covered

44.29%

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
fuzz/fuzz-server-hello.c	1
include/picotls.h	9
lib/picotls.c	105
lib/hpke.c	8

Fuzzer: fuzz-client-hello

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	286	60.0%
gold	[1:9]	4	0.84%
yellow	[10:29]	1	0.21%
greenyellow	[30:49]	0	0.0%
lawngreen	50+	185	38.8%
All colors	476	100

Fuzz blockers

The followings are the branches where fuzzer fails to bypass.

Unique non-covered Complexity	Unique Reachable Complexities	Unique Reachable Functions	All non-covered Complexity	All Reachable Complexity	Function Name	Function Callsite	Blocked Branch
233	233	1 : View List ['commission_handshake_secret']	233	443	server_finish_handshake	call site: 00359	/src/picotls/lib/picotls.c:4928
226	472	4 : View List ['ptls__key_schedule_update_hash', 'ptls_buffer__adjust_quic_blocksize', 'ptls_buffer__do_pushv', 'push_signature_algorithms']	226	920	server_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:4838
165	458	5 : View List ['ptls_aead_free', 'rebuild_ch_inner', 'decode_client_hello', 'check_client_hello_constraints', 'ptls_aead_decrypt']	1642	6805	server_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:4410
66	160	5 : View List ['ptls_buffer__do_pushv', 'ptls__key_schedule_update_hash', 'ptls_iovec_init', 'ptls_buffer__adjust_quic_blocksize', 'build_certificate_verify_signdata']	66	160	send_certificate_verify	call site: 00338	/src/picotls/lib/picotls.c:3192
66	66	3 : View List ['buffer_push_encrypted_records', 'malloc', 'free']	66	66	buffer_encrypt_record	call site: 00424	/src/picotls/lib/picotls.c:817
6	6	1 : View List ['key_schedule_update_ch1hash_prefix']	1029	5046	server_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:4523
2	2	1 : View List ['posix_memalign']	2	5	ptls_buffer_reserve_aligned	call site: 00044	/src/picotls/lib/picotls.c:598
0	234	2 : View List ['setup_traffic_protection', 'ptls__key_schedule_update_hash']	0	234	server_handle_finished	call site: 00000	/src/picotls/lib/picotls.c:4979
0	208	2 : View List ['malloc', 'derive_exporter_secret']	826	4051	server_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:4714
0	82	1 : View List ['derive_secret']	528	2261	server_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:4785
0	47	1 : View List ['push_change_cipher_spec']	0	47	server_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:4631
0	4	1 : View List ['ptls_iovec_init']	0	7	ptls_free	call site: 00473	/src/picotls/lib/picotls.c:5482

Runtime coverage analysis

Covered functions

124

Functions that are reachable but not covered

68

Reachable functions

140

Percentage of reachable functions covered

51.43%

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
fuzz/fuzz-client-hello.c	1
include/picotls.h	9
lib/picotls.c	105
lib/hpke.c	8

Fuzzer: fuzz/fuzz-asn1.c

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	76	88.3%
gold	[1:9]	0	0.0%
yellow	[10:29]	0	0.0%
greenyellow	[30:49]	0	0.0%
lawngreen	50+	10	11.6%
All colors	86	100

Fuzz blockers

The followings are the branches where fuzzer fails to bypass.

Unique non-covered Complexity	Unique Reachable Complexities	Unique Reachable Functions	All non-covered Complexity	All Reachable Complexity	Function Name	Function Callsite	Blocked Branch
263	1383	14 : View List ['derive_secret', 'ptls_buffer__adjust_quic_blocksize', 'send_certificate_verify', 'setup_traffic_protection', 'send_certificate', 'commission_handshake_secret', 'ptls_buffer__do_pushv', 'derive_exporter_secret', 'ptls__key_schedule_update_hash', 'push_change_cipher_spec', 'send_finished', 'ptls_iovec_init', 'key_schedule_extract', 'free']	263	1383	client_handle_finished	call site: 00000	/src/picotls/lib/picotls.c:3455
233	233	1 : View List ['commission_handshake_secret']	233	443	server_finish_handshake	call site: 00000	/src/picotls/lib/picotls.c:4928
210	210	2 : View List ['client_ech_select_hello', 'free']	210	1259	client_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:2828
210	210	1 : View List ['client_ech_select_hello']	210	852	client_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:2848
180	472	4 : View List ['ptls__key_schedule_update_hash', 'ptls_buffer__adjust_quic_blocksize', 'ptls_buffer__do_pushv', 'push_signature_algorithms']	180	920	server_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:4838
165	458	5 : View List ['ptls_aead_free', 'rebuild_ch_inner', 'decode_client_hello', 'check_client_hello_constraints', 'ptls_aead_decrypt']	1596	6805	server_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:4410
66	66	3 : View List ['buffer_push_encrypted_records', 'malloc', 'free']	66	66	buffer_encrypt_record	call site: 00000	/src/picotls/lib/picotls.c:817
60	160	5 : View List ['ptls_buffer__do_pushv', 'ptls__key_schedule_update_hash', 'ptls_iovec_init', 'ptls_buffer__adjust_quic_blocksize', 'build_certificate_verify_signdata']	60	160	send_certificate_verify	call site: 00000	/src/picotls/lib/picotls.c:3192
8	930	8 : View List ['ptls_buffer_reserve', 'encode_client_hello', 'strlen', 'ptls__key_schedule_update_hash', 'outer_ech_header_size', 'ptls_iovec_init', 'malloc', 'ptls_aead_encrypt']	8	1415	send_client_hello	call site: 00000	/src/picotls/lib/picotls.c:2484
7	107	7 : View List ['client_do_handle_certificate', 'ptls_decode16', 'ptls_decode_quicint', 'ptls__key_schedule_update_hash', 'ptls_iovec_init', 'malloc', 'ptls_decode24']	7	107	client_handle_compressed_certificate	call site: 00000	/src/picotls/lib/picotls.c:3332
6	6	1 : View List ['key_schedule_update_ch1hash_prefix']	983	5046	server_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:4523
2	2	1 : View List ['posix_memalign']	2	5	ptls_buffer_reserve_aligned	call site: 00048	/src/picotls/lib/picotls.c:598

Runtime coverage analysis

Covered functions

154

Functions that are reachable but not covered

34

Reachable functions

42

Percentage of reachable functions covered

19.05%

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-asn1.c	3
lib/asn1.c	9
lib/pembase64.c	6
include/picotls.h	3
lib/picotls.c	4
lib/minicrypto-pem.c	4
lib/uecc.c	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
ptls_handle_message	/src/picotls/lib/picotls.c	7	['N/A', 'N/A', 'N/A', 'size_t', 'N/A', 'size_t', 'N/A']	15	0	65	6	3	179	0	2736	1484
secp256r1sha256_sign	/src/picotls/lib/uecc.c	8	['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'size_t']	6	0	237	37	11	55	0	217	195
ptls_export	/src/picotls/lib/picotls.c	2	['N/A', 'N/A']	4	0	1105	196	53	12	0	146	108
aesgcm_decrypt	/src/picotls/lib/cifra/aes-common.h	7	['N/A', 'N/A', 'N/A', 'size_t', 'size_t', 'N/A', 'size_t']	8	0	90	8	4	33	0	99	75
ptls_import	/src/picotls/lib/picotls.c	4	['N/A', 'N/A', 'N/A', 'size_t']	11	0	919	159	50	76	0	397	69
evp_keyex_exchange	/src/picotls/lib/openssl.c	5	['N/A', 'N/A', 'N/A', 'N/A', 'size_t']	3	0	158	18	6	20	0	73	69
default_emit_certificate_cb	/src/picotls/lib/picotls.c	9	['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'size_t', 'int', 'N/A', 'size_t']	5	0	297	46	14	11	0	106	66
sign_certificate	/src/picotls/lib/openssl.c	8	['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'size_t']	6	0	143	20	7	23	0	88	64
verify_cert	/src/picotls/lib/openssl.c	7	['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'size_t']	3	0	217	31	12	26	0	72	62
secp_key_exchange	/src/picotls/lib/openssl.c	5	['N/A', 'N/A', 'N/A', 'N/A', 'size_t']	3	0	98	14	6	19	0	60	60

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

Functions statically reachable by fuzzers

315 / 596

Cyclomatic complexity statically reachable by fuzzers

3728 / 4690

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.

fuzz/fuzz-server-hello.c

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=['build_certificate_verify_signdata', 'ptls_buffer__do_pushv', 'clear_ech', 'ptls_hkdf_expand', 'ptls_buffer_dispose', 'ptls_decode16', 'ptls_send_alert', 'ptls_log__recalc_point', 'LLVMFuzzerTestOneInput', 'ptls_hmac_create']

fuzz/fuzz-client-hello.c

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=['ptls_hkdf_expand', 'ptls_buffer__do_pushv', 'key_schedule_extract', 'ptls_decode16', 'ptls_decode32', 'ptls_server_new', 'ptls_hmac_create', 'calc_verify_data', 'buffer_encrypt_record', 'ptls_receive']

fuzz/fuzz-asn1.c

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=['ptls_buffer_dispose', 'LLVMFuzzerTestOneInput', 'ptls_buffer_init', 'ptls_buffer_reserve', 'ptls_buffer_reserve_aligned']

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
send_client_hello	196	58	29.59%	['/src/picotls/fuzz/fuzz-asn1.c', 'fuzz-server-hello', 'fuzz-client-hello']
client_handle_hello	86	46	53.48%	['/src/picotls/fuzz/fuzz-asn1.c', 'fuzz-server-hello']
client_handle_compressed_certificate	38	13	34.21%	['/src/picotls/fuzz/fuzz-asn1.c', 'fuzz-server-hello']
client_handle_finished	45	8	17.77%	['/src/picotls/fuzz/fuzz-asn1.c', 'fuzz-server-hello']
send_certificate_verify	34	5	14.70%	['/src/picotls/fuzz/fuzz-asn1.c', 'fuzz-server-hello', 'fuzz-client-hello']
buffer_encrypt_record	31	15	48.38%	['/src/picotls/fuzz/fuzz-asn1.c', 'fuzz-server-hello', 'fuzz-client-hello']
handle_server_handshake_message	65	28	43.07%	['/src/picotls/fuzz/fuzz-asn1.c', 'fuzz-client-hello']

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/picotls/lib/pembase64.c	['fuzz/fuzz-asn1.c']	[]
/src/picotls/deps/micro-ecc/uECC.c	[]	[]
/src/picotls/fuzz/fuzz-server-hello.c	['fuzz-server-hello']	['fuzz-server-hello']
/src/picotls/lib/hpke.c	['fuzz-server-hello', 'fuzz-client-hello']	[]
/src/picotls/include/picotls.h	['fuzz-server-hello', 'fuzz-client-hello', 'fuzz/fuzz-asn1.c']	['fuzz-server-hello', 'fuzz-client-hello', 'fuzz/fuzz-asn1.c']
/src/picotls/lib/cifra/chacha20.c	[]	[]
/src/picotls/deps/cifra/src/ext/handy.h	[]	[]
/src/picotls/lib/openssl.c	[]	[]
/src/picotls/deps/cifra/src/gcm.c	[]	[]
/src/picotls/deps/cifra/src/modes.c	[]	[]
/src/picotls/deps/cifra/src/hmac.c	[]	[]
/src/picotls/deps/cifra/src/bitops.h	[]	[]
/src/picotls/deps/cifra/src/sha512.c	[]	[]
/src/picotls/lib/cifra/aes-common.h	[]	[]
/src/picotls/deps/cifra/src/blockwise.c	[]	[]
/usr/include/openssl/x509.h	[]	[]
/src/picotls/lib/picotls.c	['fuzz-server-hello', 'fuzz-client-hello', 'fuzz/fuzz-asn1.c']	['fuzz-server-hello', 'fuzz-client-hello', 'fuzz/fuzz-asn1.c']
/src/picotls/lib/cifra/../chacha20poly1305.h	[]	[]
/src/picotls/lib/uecc.c	['fuzz/fuzz-asn1.c']	[]
/src/picotls/lib/asn1.c	['fuzz/fuzz-asn1.c']	[]
/src/picotls/fuzz/fuzz-client-hello.c	['fuzz-client-hello']	['fuzz-client-hello']
/src/picotls/deps/cifra/src/gf128.c	[]	[]
/src/picotls/lib/cifra/aes256.c	[]	[]
/src/picotls/fuzz/fuzz-asn1.c	['fuzz/fuzz-asn1.c']	['fuzz/fuzz-asn1.c']
/src/picotls/lib/minicrypto-pem.c	['fuzz/fuzz-asn1.c']	[]
/src/picotls/deps/cifra/src/chash.c	[]	[]
/src/picotls/lib/cifra/random.c	[]	[]
/src/picotls/deps/cifra/src/chacha20.c	[]	[]
/src/picotls/deps/cifra/src/poly1305.c	[]	[]
/src/picotls/deps/micro-ecc/platform-specific.inc	[]	[]
/src/picotls/deps/micro-ecc/curve-specific.inc	[]	[]
/src/picotls/deps/cifra/src/aes.c	[]	[]
/src/picotls/deps/cifra/src/sha256.c	[]	[]
/src/picotls/deps/cifra/src/drbg.c	[]	[]
/src/picotls/lib/cifra/aes128.c	[]	[]

Directories in report

Directory
/src/picotls/deps/cifra/src/ext/
/src/picotls/fuzz/
/src/picotls/deps/micro-ecc/
/src/picotls/include/
/src/picotls/lib/cifra/../
/src/picotls/lib/cifra/
/src/picotls/lib/
/usr/include/openssl/
/src/picotls/deps/cifra/src/