Fuzz introspector
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Project coverage

Table of contents

Project overview: paramiko
High level conclusions
Reachability and coverage overview
Fuzzers overview
Project functions overview
Fuzzer details
Fuzzer: fuzz_packetizer
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
./fuzz_packetizer.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: 2025-07-02

Project overview: paramiko

High level conclusions

Reachability and coverage overview

Functions statically reachable by fuzzers
2.0%
34 / 1789
Cyclomatic complexity statically reachable by fuzzers
2.0%
115 / 5929
Runtime code coverage of functions
11.0%
203 / 1789

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_packetizer ./fuzz_packetizer.py 77 2689 7 11 43 241 fuzz_packetizer.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_packetizer

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 45 31.4%
gold [1:9] 0 0.0%
yellow [10:29] 0 0.0%
greenyellow [30:49] 0 0.0%
lawngreen 50+ 98 68.5%
All colors 143 100

Fuzz blockers

The following nodes represent call sites where fuzz blockers occur.

Amount of callsites blocked Calltree index Parent function Callsite Largest blocked function
17 108 paramiko.packet.Packetizer._build_packet call site: 00108 paramiko.util.format_binary
6 33 cryptography.hazmat.primitives.ciphers.modes.CBC.__init__ call site: 00033 paramiko.common.byte_chr
5 0 EP call site: 00000 paramiko.packet.Packetizer.__init__
5 40 paramiko.message.Message.__init__ call site: 00040 paramiko.message.Message.add
3 133 paramiko.packet.Packetizer.write_all call site: 00133 paramiko.packet.first_arg
3 138 paramiko.packet.Packetizer.send_message call site: 00138 paramiko.packet.Packetizer._log
2 68 paramiko.util.b call site: 00068 paramiko.message.Message.asbytes
1 10 paramiko.packet.Packetizer.__init__ call site: 00010 cryptography.hazmat.primitives.ciphers.base.Cipher.__init__
1 19 cryptography.hazmat.primitives.ciphers.modes._check_iv_length call site: 00019 cryptography.hazmat.primitives.ciphers.base.Cipher.encryptor
1 60 paramiko.common.byte_ord call site: 00060 .ord
1 71 paramiko.message.Message.asbytes call site: 00071 base64.encodebytes.asbytes

Runtime coverage analysis

Covered functions
294
Functions that are reachable but not covered
43
Reachable functions
77
Percentage of reachable functions covered
44.16%
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
/ 1
...paramiko.tests.fuzz_packetizer 24
paramiko.packet 24
cryptography.hazmat.primitives.ciphers.base 4
cryptography.hazmat.primitives.ciphers.modes 5
cryptography.hazmat.primitives.ciphers.algorithms 1
cryptography.hazmat.primitives._cipheralgorithm 2
cryptography.utils 1
paramiko.common 3
paramiko.message 15
paramiko.util 14

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
paramiko.client.SSHClient.connect paramiko.client 24 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 7 0 10 21 11 147 0 471 419
paramiko.ecdsakey.ECDSAKey.generate paramiko.ecdsakey 4 ['N/A', 'N/A', 'N/A', 'N/A'] 7 0 1 2 4 92 0 305 206
paramiko.sftp_client.SFTPClient.putfo paramiko.sftp_client 6 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 8 0 2 2 4 82 1 280 164
paramiko.transport.Transport.connect paramiko.transport 10 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 5 0 15 8 6 73 0 238 155
cryptography.hazmat.primitives.serialization.ssh.SSHCertificateBuilder.sign cryptography.hazmat.primitives.serialization.ssh 2 ['N/A', 'N/A'] 6 0 37 11 7 53 0 177 144
paramiko.transport.Transport.run paramiko.transport 1 ['N/A'] 6 0 42 23 12 69 0 224 118
paramiko.auth_handler.AuthHandler._parse_service_accept paramiko.auth_handler 2 ['N/A', 'N/A'] 6 0 30 14 9 79 0 256 107

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

Functions statically reachable by fuzzers
12.0%
223 / 1789
Cyclomatic complexity statically reachable by fuzzers
14.0%
812 / 5929

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.

./fuzz_packetizer.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=['paramiko.packet.Packetizer._build_packet', 'cryptography.hazmat.primitives.ciphers.modes.CBC.__init__', 'paramiko.message.Message.__init__', 'paramiko.packet.Packetizer.write_all', 'paramiko.packet.Packetizer.send_message', 'paramiko.util.b', 'paramiko.packet.Packetizer.__init__', 'cryptography.hazmat.primitives.ciphers.modes._check_iv_length', 'paramiko.common.byte_ord']

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
paramiko.packet.Packetizer.read_all 31 0 0.0% []
paramiko.packet.Packetizer.read_message 75 0 0.0% []
paramiko.channel.Channel._handle_request 69 0 0.0% []
paramiko.config.SSHConfig._does_match 35 0 0.0% []
paramiko.auth_handler.AuthHandler._parse_service_accept 80 0 0.0% []
paramiko.auth_handler.AuthHandler._parse_userauth_request 111 0 0.0% []
paramiko.transport.Transport.__init__ 87 0 0.0% []
paramiko.transport.Transport.open_channel 49 0 0.0% []
paramiko.transport.Transport.run 108 0 0.0% []
paramiko.transport.Transport._send_kex_init 36 0 0.0% []
paramiko.transport.Transport._parse_kex_init 88 0 0.0% []
paramiko.transport.Transport._activate_outbound 41 0 0.0% []
paramiko.transport.Transport._parse_channel_open 81 0 0.0% []
re.search 74 21 28.37% ['fuzz_packetizer']
cryptography.hazmat.primitives.serialization.ssh.load_ssh_private_key 68 0 0.0% []
cryptography.hazmat.primitives.serialization.ssh._serialize_ssh_private_key 52 5 9.615% ['fuzz_packetizer']
cryptography.hazmat.primitives.serialization.ssh._load_ssh_public_identity 56 0 0.0% []
cryptography.hazmat.primitives.serialization.ssh.SSHCertificateBuilder.sign 85 0 0.0% []
paramiko.pkey.PKey._read_private_key_pem 38 0 0.0% []
paramiko.pkey.PKey._read_private_key_openssh 35 0 0.0% []
paramiko.ecdsakey.ECDSAKey.__init__ 32 0 0.0% []
paramiko.client.SSHClient.connect 66 0 0.0% []
paramiko.client.SSHClient._auth 88 0 0.0% []
paramiko.ber.BER.decode_next 32 0 0.0% []
paramiko.kex_gss.KexGSSGroup1._parse_kexgss_init 33 0 0.0% []
paramiko.kex_gss.KexGSSGex._parse_kexgss_gex_init 39 0 0.0% []
paramiko.kex_gss.KexGSSGex._parse_kexgss_complete 31 0 0.0% []
paramiko.ed25519key.Ed25519Key._parse_signing_key_data 49 0 0.0% []
nacl.signing.SigningKey 90 36 40.0% ['fuzz_packetizer']
paramiko.sftp_attr.SFTPAttributes.__str__ 38 0 0.0% []
paramiko.file.BufferedFile.read 40 0 0.0% []
paramiko.file.BufferedFile.readline 54 0 0.0% []
paramiko.sftp_server.SFTPServer._check_file 49 0 0.0% []
paramiko.sftp_server.SFTPServer._process 121 1 0.826% ['fuzz_packetizer']

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
[] []
paramiko.file [] []
os [] []
cryptography.fernet [] []
cryptography.hazmat.bindings.openssl [] []
cryptography.hazmat.backends.openssl.backend [] []
cryptography.hazmat.primitives.poly1305 [] []
paramiko.channel [] []
cryptography.hazmat.primitives.asymmetric.rsa [] []
cryptography.hazmat.primitives.asymmetric.x448 [] []
cryptography.__about__ [] []
paramiko.sftp_attr [] []
cryptography.hazmat.primitives.serialization [] []
cryptography.hazmat.primitives.ciphers.modes ['fuzz_packetizer'] []
paramiko.pkey [] []
cryptography.exceptions [] []
paramiko.ecdsakey [] []
paramiko.sftp [] []
paramiko.pipe [] []
...paramiko.tests.fuzz_packetizer ['fuzz_packetizer'] []
paramiko.kex_ecdh_nist [] []
paramiko.kex_gss [] []
cryptography.hazmat.primitives.kdf.x963kdf [] []
cryptography.hazmat.primitives.asymmetric.x25519 [] []
base64 [] []
cryptography.hazmat._oid [] []
paramiko.primes [] []
cryptography.hazmat.primitives.ciphers [] []
cryptography.hazmat.bindings.openssl.binding [] []
paramiko.hostkeys [] []
paramiko.ssh_exception [] []
_loop [] []
datetime [] []
atexit [] []
cryptography.hazmat.primitives.hmac [] []
cryptography.hazmat.primitives.kdf.kbkdf [] []
cryptography.hazmat.primitives.ciphers.base ['fuzz_packetizer'] []
logging [] []
cryptography.hazmat.primitives.asymmetric.padding [] []
socket [] []
paramiko.auth_handler [] []
paramiko.transport [] []
cryptography.hazmat.primitives.kdf.argon2 [] []
paramiko.kex_group1 [] []
atheris [] []
cryptography.x509.oid [] []
cryptography.hazmat.primitives._asymmetric [] []
collections [] []
paramiko.sftp_server [] []
paramiko.client [] []
paramiko.kex_group16 [] []
cryptography.hazmat.primitives.twofactor.hotp [] []
cryptography.hazmat.primitives.asymmetric.types [] []
fnmatch [] []
random [] []
tempfile [] []
paramiko.proxy [] []
paramiko.ssh_gss [] []
cryptography.x509.extensions [] []
paramiko.compress [] []
paramiko.win_openssh [] []
[] []
cryptography.hazmat.bindings.openssl._conditional [] []
cryptography.hazmat.bindings._rust [] []
fcntl [] []
cryptography.hazmat.primitives.serialization.ssh [] []
shlex [] []
types [] []
cryptography.hazmat.primitives.hashes [] []
typing [] []
cryptography.hazmat.primitives.serialization.base [] []
threading [] []
paramiko.win_pageant [] []
cryptography.hazmat.decrepit.ciphers.algorithms [] []
_thread [] []
array [] []
cryptography.hazmat.primitives.kdf [] []
cryptography.utils ['fuzz_packetizer'] []
paramiko.ber [] []
cryptography.hazmat.primitives.asymmetric.ed25519 [] []
paramiko.auth_strategy [] []
subprocess [] []
paramiko.sftp_file [] []
paramiko.config [] []
cryptography.x509 [] []
warnings [] []
paramiko._version [] []
traceback [] []
math [] []
getpass [] []
cryptography.hazmat.primitives.asymmetric.utils [] []
cryptography.x509.certificate_transparency [] []
cryptography.x509.verification [] []
cryptography.x509.general_name [] []
paramiko.kex_curve25519 [] []
weakref [] []
cryptography.hazmat.primitives.asymmetric.ed448 [] []
paramiko.util ['fuzz_packetizer'] []
invoke [] []
paramiko.packet ['fuzz_packetizer'] []
cryptography.hazmat.primitives.asymmetric.dsa [] []
cryptography.hazmat.primitives.asymmetric [] []
paramiko.kex_gex [] []
cryptography [] []
select [] []
urllib [] []
cryptography.hazmat.backends.openssl [] []
stat [] []
cryptography.hazmat.backends [] []
struct [] []
paramiko [] []
paramiko.message ['fuzz_packetizer'] []
cryptography.hazmat.primitives.ciphers.algorithms ['fuzz_packetizer'] []
re [] []
hashlib [] []
cryptography.hazmat.primitives.asymmetric.ec [] []
bcrypt [] []
paramiko.kex_group14 [] []
cryptography.x509.name [] []
pathlib [] []
cryptography.hazmat.primitives.kdf.scrypt [] []
functools [] []
cryptography.hazmat.primitives._serialization [] []
cryptography.hazmat.primitives.ciphers.aead [] []
cryptography.hazmat.primitives._cipheralgorithm ['fuzz_packetizer'] []
sys [] []
cryptography.hazmat.decrepit.ciphers [] []
time [] []
paramiko.dsskey [] []
paramiko.sftp_client [] []
paramiko.rsakey [] []
platform [] []
zlib [] []
cryptography.hazmat.primitives.keywrap [] []
cryptography.hazmat.primitives.kdf.pbkdf2 [] []
pyasn1 [] []
cryptography.hazmat.primitives.kdf.hkdf [] []
sspi [] []
cryptography.hazmat.primitives [] []
cryptography.hazmat.decrepit [] []
cryptography.hazmat.primitives.twofactor.totp [] []
cryptography.hazmat.primitives.constant_time [] []
cryptography.hazmat.primitives.padding [] []
cryptography.hazmat.primitives.cmac [] []
cryptography.hazmat.primitives.asymmetric.dh [] []
email [] []
cryptography.hazmat.primitives.serialization.pkcs7 [] []
paramiko.server [] []
paramiko.sftp_handle [] []
cryptography.x509.base [] []
cryptography.hazmat.primitives.kdf.concatkdf [] []
cryptography.hazmat.bindings [] []
paramiko.agent [] []
paramiko._winapi [] []
paramiko.sftp_si [] []
hmac [] []
paramiko.common ['fuzz_packetizer'] []
io [] []
paramiko.buffered_pipe [] []
cryptography.x509.ocsp [] []
gssapi [] []
paramiko.ed25519key [] []
cryptography.hazmat.primitives.twofactor [] []
cryptography.hazmat.primitives.serialization.pkcs12 [] []
inspect [] []
binascii [] []
cryptography.hazmat [] []

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_packetizer fuzzerLogFile-fuzz_packetizer.data fuzzerLogFile-fuzz_packetizer.data.yaml all_cov.json