High level conclusions

Reachability and coverage 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.

Fuzzer: ssh2_client_fuzzer

Call tree

Fuzz blockers

The following nodes represent call sites where fuzz blockers occur.

Runtime coverage analysis

Files reached

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.

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

All functions overview

If you implement fuzzers for these functions, the status of all functions in the project will be:

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.

tests/ossfuzz/ssh2_client_fuzzer.cc

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=['session_free', 'ssh2_channel_locate', 'packet_queue_listener', 'ssh2_hash', 'transport_fullpacket', 'packet_authagent_open', 'packet_x11_open', 'ssh2_transport_send']

This section shows analysis of runtime coverage data.

Complex functions with low coverage

New fuzzers

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

hostkey.c

#include "ada_fuzz_header.h"

int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
  af_safe_gb_init(data, size);

  /* target hostkey_method_ssh_ed25519_initPEM */
  UNKNOWN_TYPE unknown_0;
  char *new_var1 = ada_safe_get_char_p();
  char *new_var2 = ada_safe_get_char_p();
  UNKNOWN_TYPE unknown_3;
  char *new_var4 = ada_safe_get_char_p();
  UNKNOWN_TYPE unknown_5;
  hostkey_method_ssh_ed25519_initPEM(unknown_0, new_var1, new_var2, unknown_3, new_var4, unknown_5);

  af_safe_gb_cleanup();
}

session_fixture.c

#include "ada_fuzz_header.h"

int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
  af_safe_gb_init(data, size);

  /* target test_auth_pubkey */
  UNKNOWN_TYPE unknown_6;
  int new_var7 = ada_safe_get_int();
  char *new_var8 = ada_safe_get_char_p();
  char *new_var9 = ada_safe_get_char_p();
  char *new_var10 = ada_safe_get_char_p();
  char *new_var11 = ada_safe_get_char_p();
  test_auth_pubkey(unknown_6, new_var7, new_var8, new_var9, new_var10, new_var11);

  /* target start_session_fixture */
  int *new_var30 = af_get_int_p();
  int *new_var31 = af_get_int_p();
  start_session_fixture(new_var30, new_var31);

  af_safe_gb_cleanup();
}

scp.c

#include "ada_fuzz_header.h"

int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
  af_safe_gb_init(data, size);

  /* target libssh2_scp_recv */
  UNKNOWN_TYPE unknown_12;
  char *new_var13 = ada_safe_get_char_p();
  structstat* new_var14 = calloc(sizeof(structstat), 1);
  libssh2_scp_recv(unknown_12, new_var13, new_var14);

  af_safe_gb_cleanup();
}

kex.c

#include "ada_fuzz_header.h"

int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
  af_safe_gb_init(data, size);

  /* target kex_method_mlkem768x25519_key_exchange */
  UNKNOWN_TYPE unknown_15;
  structkey_exchange_state_low* new_var16 = calloc(sizeof(structkey_exchange_state_low), 1);
  kex_method_mlkem768x25519_key_exchange(unknown_15, new_var16);

  /* target kex_method_diffie_hellman_group_exchange_sha1_key_exchange */
  UNKNOWN_TYPE unknown_28;
  structkey_exchange_state_low* new_var29 = calloc(sizeof(structkey_exchange_state_low), 1);
  kex_method_diffie_hellman_group_exchange_sha1_key_exchange(unknown_28, new_var29);

  af_safe_gb_cleanup();
}

test_simple.c

#include "ada_fuzz_header.h"

int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
  af_safe_gb_init(data, size);

  /* target test_knownhost_ipv6_case */
  UNKNOWN_TYPE unknown_17;
  char *new_var18 = ada_safe_get_char_p();
  char *new_var19 = ada_safe_get_char_p();
  int new_var20 = ada_safe_get_int();
  int new_var21 = ada_safe_get_int();
  test_knownhost_ipv6_case(unknown_17, new_var18, new_var19, new_var20, new_var21);

  af_safe_gb_cleanup();
}

sftp.c

#include "ada_fuzz_header.h"

int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
  af_safe_gb_init(data, size);

  /* target sftp_readdir */
  UNKNOWN_TYPE unknown_22;
  char *new_var23 = ada_safe_get_char_p();
  UNKNOWN_TYPE unknown_24;
  char *new_var25 = ada_safe_get_char_p();
  UNKNOWN_TYPE unknown_26;
  UNKNOWN_TYPE unknown_27;
  sftp_readdir(unknown_22, new_var23, unknown_24, new_var25, unknown_26, unknown_27);

  af_safe_gb_cleanup();
}

x11.c

#include "ada_fuzz_header.h"

int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
  af_safe_gb_init(data, size);

  /* target x11_send_receive */
  UNKNOWN_TYPE unknown_32;
  UNKNOWN_TYPE unknown_33;
  x11_send_receive(unknown_32, unknown_33);

  af_safe_gb_cleanup();
}

publickey.c

#include "ada_fuzz_header.h"

int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
  af_safe_gb_init(data, size);

  /* target libssh2_publickey_list_fetch */
  UNKNOWN_TYPE unknown_34;
  UNKNOWN_TYPE unknown_35;
  UNKNOWN_TYPE unknown_36;
  libssh2_publickey_list_fetch(unknown_34, unknown_35, unknown_36);

  af_safe_gb_cleanup();
}

Files in report

Directories in report

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

This section contains multiple tables, each table contains a list of sink functions/methods found in the project for one of the CWE supported by the sink analyser, together with information like which fuzzers statically reach the sink functions/methods and possible call path to that sink functions/methods if it is not statically reached by any fuzzers. Column 1 is the function/method name of the sink functions/methods found in the project. Column 2 lists all fuzzers (or no fuzzers at all) that have covered that particular function method statically. Column 3 shows a list of possible call paths to reach the specific function/method call if none of the fuzzers cover the target function/method calls. Lastly, column 4 shows possible fuzzer blockers that prevent an existing fuzzer from reaching the target sink functions/methods dynamically.

Sink functions/methods found for CWE78

Sink functions/methods found for CWE22