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 33.83% of cyclomatic complexity.

Fuzzers reach 23.76% of all functions.

Reachability and coverage overview

Functions statically reachable by fuzzers

144 / 606

Cyclomatic complexity statically reachable by fuzzers

1597 / 4720

Runtime code coverage of functions

146 / 606

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	308	64.3%
gold	[1:9]	7	1.46%
yellow	[10:29]	3	0.62%
greenyellow	[30:49]	1	0.20%
lawngreen	50+	160	33.4%
All colors	479	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
49	343	build_certificate_verify_signdata	call site: 00343	commission_handshake_secret
30	125	ptls_buffer__do_pushv	call site: 00125	ptls_hpke_setup_base_s
30	202	clear_ech	call site: 00202	decode_stored_session_ticket
28	173	ptls_hkdf_expand	call site: 00173	key_schedule
21	48	ptls_buffer_dispose	call site: 00048	ptls_log__do_write_end
18	106	ptls_decode16	call site: 00106	client_setup_ech
16	423	ptls_send_alert	call site: 00423	buffer_encrypt_record
15	15	ptls_log__recalc_point	call site: 00015	ptls_log_conn_maybe_active
15	442	LLVMFuzzerTestOneInput	call site: 00442	ptls_receive
14	158	ptls_hmac_create	call site: 00158	labeled_expand
12	31	ptls_buffer_init	call site: 00031	ptls_log__do_push_element_unsigned64
12	289	send_client_hello	call site: 00289	encode_client_hello

Runtime coverage analysis

Covered functions

106

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	287	60.2%
gold	[1:9]	4	0.84%
yellow	[10:29]	1	0.21%
greenyellow	[30:49]	1	0.21%
lawngreen	50+	183	38.4%
All colors	476	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
39	173	ptls_hkdf_expand	call site: 00173	decode_stored_session_ticket
30	125	ptls_buffer__do_pushv	call site: 00125	ptls_hpke_setup_base_s
23	255	key_schedule_extract	call site: 00255	encode_client_hello
18	106	ptls_decode16	call site: 00106	client_setup_ech
17	219	ptls_decode32	call site: 00219	key_schedule_extract
15	54	ptls_server_new	call site: 00054	ptls_log__recalc_conn
14	158	ptls_hmac_create	call site: 00158	labeled_expand
13	288	calc_verify_data	call site: 00288	encode_client_hello
12	427	buffer_encrypt_record	call site: 00427	buffer_push_encrypted_records
10	443	ptls_receive	call site: 00443	handle_input_tls12
9	17	ptls_server_new	call site: 00017	ptls_log__recalc_conn
9	83	log_client_random	call site: 00083	ptls_log__do_write_end

Runtime coverage analysis

Covered functions

118

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 following nodes represent call sites where fuzz blockers occur.

Amount of callsites blocked	Calltree index	Parent function	Callsite	Largest blocked function
33	52	ptls_buffer_dispose	call site: 00052	ptls_minicrypto_load_private_key
16	3	LLVMFuzzerTestOneInput	call site: 00003	ptls_asn1_validation
14	32	ptls_buffer_init	call site: 00032	ptls_get_pem_object
9	22	LLVMFuzzerTestOneInput	call site: 00022	ptls_load_certificates
1	0	EP	call site: 00000	feeder_init
1	20	LLVMFuzzerTestOneInput	call site: 00020	feeder_next_byte
1	48	ptls_buffer_reserve	call site: 00048	posix_memalign
1	50	ptls_buffer_reserve_aligned	call site: 00050	ptls_buffer_dispose

Runtime coverage analysis

Covered functions

148

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	58	6	3	179	0	2737	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	218	37	11	55	0	217	195
ptls_export	/src/picotls/lib/picotls.c	2	['N/A', 'N/A']	4	0	1072	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	80	8	4	33	0	99	75
ptls_import	/src/picotls/lib/picotls.c	4	['N/A', 'N/A', 'N/A', 'size_t']	11	0	885	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	151	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	279	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	132	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	202	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	90	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 / 606

Cyclomatic complexity statically reachable by fuzzers

3729 / 4720

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	57	29.08%	['fuzz-client-hello', 'fuzz-server-hello', '/src/picotls/fuzz/fuzz-asn1.c']
client_handle_hello	86	46	53.48%	['fuzz-server-hello', '/src/picotls/fuzz/fuzz-asn1.c']
client_handle_compressed_certificate	38	13	34.21%	['fuzz-server-hello', '/src/picotls/fuzz/fuzz-asn1.c']
client_handle_finished	45	8	17.77%	['fuzz-server-hello', '/src/picotls/fuzz/fuzz-asn1.c']
send_certificate_verify	32	5	15.62%	['fuzz-client-hello', 'fuzz-server-hello', '/src/picotls/fuzz/fuzz-asn1.c']
buffer_encrypt_record	31	15	48.38%	['fuzz-client-hello', 'fuzz-server-hello', '/src/picotls/fuzz/fuzz-asn1.c']
handle_server_handshake_message	65	29	44.61%	['fuzz-client-hello', '/src/picotls/fuzz/fuzz-asn1.c']

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

Directories in report

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