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 33.48% of cyclomatic complexity.

Fuzzers reach 22.60% of all functions.

Reachability and coverage overview

Functions statically reachable by fuzzers

132 / 584

Cyclomatic complexity statically reachable by fuzzers

1573 / 4697

Runtime code coverage of functions

149 / 584

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-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	184	61.1%
gold	[1:9]	0	0.0%
yellow	[10:29]	5	1.66%
greenyellow	[30:49]	0	0.0%
lawngreen	50+	112	37.2%
All colors	301	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
572	1131	14 : View List ['derive_secret', 'ptls__key_schedule_update_hash', 'push_change_cipher_spec', 'derive_exporter_secret', 'free', 'setup_traffic_protection', 'ptls_buffer__do_pushv', 'commission_handshake_secret', 'ptls_buffer__adjust_quic_blocksize', 'send_certificate', 'send_finished', 'ptls_iovec_init', 'key_schedule_extract', 'send_certificate_verify']	572	1131	client_handle_finished	call site: 00000	/src/picotls/lib/picotls.c:3428
144	144	2 : View List ['client_ech_select_hello', 'free']	144	1117	client_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:2803
144	144	1 : View List ['client_ech_select_hello']	144	660	client_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:2823
82	164	2 : View List ['derive_secret_with_empty_digest', 'calc_verify_data']	282	1437	send_client_hello	call site: 00143	/src/picotls/lib/picotls.c:2447
73	73	1 : View List ['buffer_encrypt_record']	73	73	commit_record_message	call site: 00000	/src/picotls/lib/picotls.c:849
47	214	2 : View List ['setup_traffic_protection', 'push_change_cipher_spec']	192	359	send_client_hello	call site: 00168	/src/picotls/lib/picotls.c:2529
8	906	8 : View List ['encode_client_hello', 'ptls__key_schedule_update_hash', 'ptls_aead_encrypt', 'outer_ech_header_size', 'strlen', 'ptls_iovec_init', 'ptls_buffer_reserve', 'malloc']	200	1265	send_client_hello	call site: 00158	/src/picotls/lib/picotls.c:2459
7	107	7 : View List ['ptls_decode16', 'ptls_decode24', 'ptls__key_schedule_update_hash', 'client_do_handle_certificate', 'ptls_decode_quicint', 'ptls_iovec_init', 'malloc']	7	107	client_handle_compressed_certificate	call site: 00000	/src/picotls/lib/picotls.c:3305
5	7	2 : View List ['ptls_is_server', 'ptls_is_ech_handshake']	5	7	handle_certificate	call site: 00000	/src/picotls/lib/picotls.c:3252
2	2	1 : View List ['posix_memalign']	2	5	ptls_buffer_reserve_aligned	call site: 00028	/src/picotls/lib/picotls.c:580
0	87	1 : View List ['key_schedule_extract']	0	87	key_schedule_select_cipher	call site: 00000	/src/picotls/lib/picotls.c:1346
0	82	2 : View List ['derive_secret', 'malloc']	0	82	client_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:2859

Runtime coverage analysis

Covered functions

105

Functions that are reachable but not covered

62

Reachable functions

121

Percentage of reachable functions covered

48.76%

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	6
lib/picotls.c	74
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	163	54.8%
gold	[1:9]	2	0.67%
yellow	[10:29]	0	0.0%
greenyellow	[30:49]	14	4.71%
lawngreen	50+	118	39.7%
All colors	297	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
226	472	4 : View List ['push_signature_algorithms', 'ptls_buffer__do_pushv', 'ptls_buffer__adjust_quic_blocksize', 'ptls__key_schedule_update_hash']	226	857	server_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:4781
170	170	1 : View List ['commission_handshake_secret']	170	380	server_finish_handshake	call site: 00209	/src/picotls/lib/picotls.c:4871
165	457	5 : View List ['ptls_aead_decrypt', 'check_client_hello_constraints', 'ptls_aead_free', 'rebuild_ch_inner', 'decode_client_hello']	1612	6330	server_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:4375
66	160	5 : View List ['ptls_buffer__do_pushv', 'build_certificate_verify_signdata', 'ptls_buffer__adjust_quic_blocksize', 'ptls__key_schedule_update_hash', 'ptls_iovec_init']	66	160	send_certificate_verify	call site: 00198	/src/picotls/lib/picotls.c:3165
66	66	3 : View List ['buffer_push_encrypted_records', 'free', 'malloc']	66	66	buffer_encrypt_record	call site: 00258	/src/picotls/lib/picotls.c:799
6	6	1 : View List ['key_schedule_update_ch1hash_prefix']	999	4572	server_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:4488
2	2	1 : View List ['posix_memalign']	2	5	ptls_buffer_reserve_aligned	call site: 00028	/src/picotls/lib/picotls.c:580
0	171	2 : View List ['setup_traffic_protection', 'ptls__key_schedule_update_hash']	0	171	server_handle_finished	call site: 00000	/src/picotls/lib/picotls.c:4920
0	145	2 : View List ['derive_exporter_secret', 'malloc']	796	3577	server_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:4663
0	82	1 : View List ['derive_secret']	498	2039	server_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:4731
0	47	1 : View List ['push_change_cipher_spec']	0	47	server_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:4596
0	4	1 : View List ['ptls_iovec_init']	0	7	ptls_free	call site: 00294	/src/picotls/lib/picotls.c:5415

Runtime coverage analysis

Covered functions

121

Functions that are reachable but not covered

52

Reachable functions

121

Percentage of reachable functions covered

57.02%

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	6
lib/picotls.c	74
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	71	84.5%
gold	[1:9]	0	0.0%
yellow	[10:29]	0	0.0%
greenyellow	[30:49]	0	0.0%
lawngreen	50+	13	15.4%
All colors	84	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
200	1131	14 : View List ['derive_secret', 'ptls__key_schedule_update_hash', 'push_change_cipher_spec', 'derive_exporter_secret', 'free', 'setup_traffic_protection', 'ptls_buffer__do_pushv', 'commission_handshake_secret', 'ptls_buffer__adjust_quic_blocksize', 'send_certificate', 'send_finished', 'ptls_iovec_init', 'key_schedule_extract', 'send_certificate_verify']	200	1131	client_handle_finished	call site: 00000	/src/picotls/lib/picotls.c:3428
180	472	4 : View List ['push_signature_algorithms', 'ptls_buffer__do_pushv', 'ptls_buffer__adjust_quic_blocksize', 'ptls__key_schedule_update_hash']	180	857	server_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:4781
170	170	1 : View List ['commission_handshake_secret']	170	380	server_finish_handshake	call site: 00000	/src/picotls/lib/picotls.c:4871
165	457	5 : View List ['ptls_aead_decrypt', 'check_client_hello_constraints', 'ptls_aead_free', 'rebuild_ch_inner', 'decode_client_hello']	1566	6330	server_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:4375
144	144	2 : View List ['client_ech_select_hello', 'free']	144	1117	client_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:2803
144	144	1 : View List ['client_ech_select_hello']	144	660	client_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:2823
66	66	3 : View List ['buffer_push_encrypted_records', 'free', 'malloc']	66	66	buffer_encrypt_record	call site: 00000	/src/picotls/lib/picotls.c:799
60	160	5 : View List ['ptls_buffer__do_pushv', 'build_certificate_verify_signdata', 'ptls_buffer__adjust_quic_blocksize', 'ptls__key_schedule_update_hash', 'ptls_iovec_init']	60	160	send_certificate_verify	call site: 00000	/src/picotls/lib/picotls.c:3165
8	906	8 : View List ['encode_client_hello', 'ptls__key_schedule_update_hash', 'ptls_aead_encrypt', 'outer_ech_header_size', 'strlen', 'ptls_iovec_init', 'ptls_buffer_reserve', 'malloc']	8	1265	send_client_hello	call site: 00000	/src/picotls/lib/picotls.c:2459
7	107	7 : View List ['ptls_decode16', 'ptls_decode24', 'ptls__key_schedule_update_hash', 'client_do_handle_certificate', 'ptls_decode_quicint', 'ptls_iovec_init', 'malloc']	7	107	client_handle_compressed_certificate	call site: 00000	/src/picotls/lib/picotls.c:3305
6	6	1 : View List ['key_schedule_update_ch1hash_prefix']	953	4572	server_handle_hello	call site: 00000	/src/picotls/lib/picotls.c:4488
2	2	1 : View List ['posix_memalign']	2	5	ptls_buffer_reserve_aligned	call site: 00048	/src/picotls/lib/picotls.c:580

Runtime coverage analysis

Covered functions

151

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	162	0	2718	1530
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	58	0	339	69
evp_keyex_exchange	/src/picotls/lib/openssl.c	5	['N/A', 'N/A', 'N/A', 'N/A', 'size_t']	3	0	141	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

303 / 584

Cyclomatic complexity statically reachable by fuzzers

3751 / 4697

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-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=['send_client_hello', 'ptls_buffer_reserve_aligned', 'ptls_hkdf_expand', 'LLVMFuzzerTestOneInput', 'ptls_buffer_dispose', 'clear_ech', 'ptls_send_alert', 'new_aead']

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_reserve_aligned', 'ptls_buffer_dispose', 'calc_verify_data', 'ptls_handshake', 'ptls_receive', 'ptls_decode16', 'key_schedule_extract', 'push_change_cipher_spec', 'buffer_encrypt_record']

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%	['fuzz-server-hello', 'fuzz-client-hello']
client_handle_hello	84	44	52.38%	[]
client_handle_compressed_certificate	38	13	34.21%	[]
client_handle_finished	45	8	17.77%	[]
send_certificate_verify	34	5	14.70%	['fuzz-server-hello', 'fuzz-client-hello']
buffer_encrypt_record	31	15	48.38%	['fuzz-server-hello', 'fuzz-client-hello']
handle_server_handshake_message	65	28	43.07%	[]

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

Directories in report

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