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Mon, 13 Oct 2025 17:30:20 -0700 (PDT) Date: Tue, 14 Oct 2025 00:30:07 +0000 In-Reply-To: <20251014003008.2520701-1-navidem@google.com> Mime-Version: 1.0 References: <20251014003008.2520701-1-navidem@google.com> X-Mailer: git-send-email 2.51.0.760.g7b8bcc2412-goog Message-ID: <20251014003008.2520701-2-navidem@google.com> Subject: [PATCH v2 1/1] tests/qtest/fuzz: Add generic fuzzer for VNC From: Navid Emamdoost To: qemu-devel@nongnu.org Cc: alxndr@bu.edu, berrange@redhat.com, Navid Emamdoost , Paolo Bonzini , Bandan Das , Stefan Hajnoczi , Fabiano Rosas , Darren Kenny , Qiuhao Li , Laurent Vivier Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2607:f8b0:4864:20::1049; envelope-from=3nJntaAcKCtMCzK723B5DD5A3.1DBF3BJ-23K3ACDC5CJ.DG5@flex--navidem.bounces.google.com; helo=mail-pj1-x1049.google.com X-Spam_score_int: -98 X-Spam_score: -9.9 X-Spam_bar: --------- X-Spam_report: (-9.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_MED=-0.268, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, USER_IN_DEF_DKIM_WL=-7.5 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @google.com) X-ZM-MESSAGEID: 1760401886847158500 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add a new generic fuzz target for the QEMU VNC server. This target exercises both the standard VNC protocol and the VNC-over-WebSocket transport layer, increasing coverage of a primary remote attack surface. To support parallel fuzzing (e.g., with oss-fuzz), the VNC unix socket paths are generated dynamically. The fuzzer harness inspects the command line for placeholders and replaces them with unique paths created by mkstemp() before execution. --- This new target increases code coverage in the VNC subsystem and related networking and I/O code. The baseline coverage below was generated by running all existing fuzz targets with the oss-fuzz corpus. The new target shows significant gains: ---------------------------------------------------------------------------- File New Target Baseline Change ---------------------------------------------------------------------------- vnc.c 339/3212 (10.6%) 3/3212 (0.1%) +336 keymaps.c 91/184 (49.5%) 0/184 (0.0%) +91 net-listener.c 76/198 (38.4%) 3/198 (1.5%) +73 channel-socket.c 73/575 (12.7%) 19/575 (3.3%) +54 qemu-sockets.c 44/1019 (4.3%) 0/1019 (0.0%) +44 vnc-jobs.c 41/219 (18.7%) 0/219 (0.0%) +41 dns-resolver.c 28/145 (19.3%) 3/145 (2.1%) +25 Signed-off-by: Navid Emamdoost --- tests/qtest/fuzz/fuzz.c | 65 +++++++++++++++++++++++++ tests/qtest/fuzz/generic_fuzz_configs.h | 5 ++ 2 files changed, 70 insertions(+) diff --git a/tests/qtest/fuzz/fuzz.c b/tests/qtest/fuzz/fuzz.c index ca248a51a6..b77c3ceb2b 100644 --- a/tests/qtest/fuzz/fuzz.c +++ b/tests/qtest/fuzz/fuzz.c @@ -126,6 +126,46 @@ static FuzzTarget *fuzz_get_target(char* name) return NULL; } =20 +/* + * Global variables to hold the unique socket paths for cleanup. + */ +static char g_vnc_socket_path[sizeof("/tmp/qemu-vnc.XXXXXX")]; +static char g_vnc_ws_socket_path[sizeof("/tmp/qemu-vnc-ws.XXXXXX")]; + +/* + * atexit() handler to clean up both socket files. + */ +static void cleanup_vnc_sockets(void) +{ + if (g_vnc_socket_path[0] !=3D '\0') { + unlink(g_vnc_socket_path); + } + if (g_vnc_ws_socket_path[0] !=3D '\0') { + unlink(g_vnc_ws_socket_path); + } +} + +/* Helper function to find and replace a placeholder in a GString */ +static bool replace_socket_placeholder(GString *cmd_line, const char *plac= eholder, + const char *path_template, char *gl= obal_path_out) +{ + char *placeholder_ptr =3D strstr(cmd_line->str, placeholder); + if (placeholder_ptr) { + int fd; + strcpy(global_path_out, path_template); + fd =3D mkstemp(global_path_out); + if (fd =3D=3D -1) { + perror("mkstemp failed"); + return false; + } + close(fd); + + gssize pos =3D placeholder_ptr - cmd_line->str; + g_string_erase(cmd_line, pos, strlen(placeholder)); + g_string_insert(cmd_line, pos, global_path_out); + } + return true; +} =20 /* Sometimes called by libfuzzer to mutate two inputs into one */ size_t LLVMFuzzerCustomCrossOver(const uint8_t *data1, size_t size1, @@ -213,6 +253,31 @@ int LLVMFuzzerInitialize(int *argc, char ***argv, char= ***envp) g_string_append_printf(cmd_line, " %s -qtest /dev/null ", getenv("QTEST_LOG") ? "" : "-qtest-log none"); =20 + /* + * For the VNC fuzzer, we replace placeholders for both the standard + * and WebSocket VNC listeners with unique socket paths. + */ + if (strcmp(fuzz_target->name, "generic-fuzz-vnc") =3D=3D 0) { + bool success =3D true; + success &=3D replace_socket_placeholder(cmd_line, "VNC_SOCKET_PATH= ", + "/tmp/qemu-vnc.XXXXXX", g_vn= c_socket_path); + success &=3D replace_socket_placeholder(cmd_line, "VNC_WS_SOCKET_P= ATH", + "/tmp/qemu-vnc-ws.XXXXXX", g= _vnc_ws_socket_path); + + if (!success) { + exit(1); + } + + /* Check that placeholders were actually found and replaced */ + if (g_vnc_socket_path[0] =3D=3D '\0' || g_vnc_ws_socket_path[0] = =3D=3D '\0') { + fprintf(stderr, "ERROR: VNC fuzzer is missing a socket placeho= lder\n"); + exit(1); + } + + /* Register a single cleanup handler for both sockets */ + atexit(cleanup_vnc_sockets); + } + /* Split the runcmd into an argv and argc */ wordexp_t result; wordexp(cmd_line->str, &result, 0); diff --git a/tests/qtest/fuzz/generic_fuzz_configs.h b/tests/qtest/fuzz/gen= eric_fuzz_configs.h index ef0ad95712..bd2d875dd8 100644 --- a/tests/qtest/fuzz/generic_fuzz_configs.h +++ b/tests/qtest/fuzz/generic_fuzz_configs.h @@ -247,6 +247,11 @@ const generic_fuzz_config predefined_configs[] =3D { .args =3D "-machine q35 -nodefaults " "-parallel file:/dev/null", .objects =3D "parallel*", + },{ + .name =3D "vnc", + .args =3D "-machine q35 -nodefaults " + "-vnc vnc=3Dunix:VNC_SOCKET_PATH,websocket=3Dunix:VNC_WS_SOCKET_PATH", + .objects =3D "*", } }; =20 --=20 2.51.0.760.g7b8bcc2412-goog