chore(userspace/libscap): cleanup weird usages of strncmp for engines.

Moreover, properly compile-check that bpf and kmod engines are built before de-referencing their vtable. Signed-off-by: Federico Di Pierro <nierro92@gmail.com>
falcosecurity · Oct 26, 2022 · 6549aaf · 6549aaf
1 parent 1b8cc0b
commit 6549aaf
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Showing 17 changed files with 32 additions and 66 deletions.
diff --git a/userspace/libscap/CMakeLists.txt b/userspace/libscap/CMakeLists.txt
@@ -188,9 +188,11 @@ add_subdirectory(engine/udig)
 target_link_libraries(scap scap_engine_udig)
 
 if(CMAKE_SYSTEM_NAME MATCHES "Linux")
-	add_definitions(-DHAS_ENGINE_BPF)
-	add_subdirectory(engine/bpf)
-	target_link_libraries(scap scap_engine_bpf)
+	if (NOT MINIMAL_BUILD)
+		add_definitions(-DHAS_ENGINE_BPF)
+		add_subdirectory(engine/bpf)
+		target_link_libraries(scap scap_engine_bpf)
+	endif()
 
 	add_definitions(-DHAS_ENGINE_KMOD)
 	add_subdirectory(engine/kmod)

diff --git a/userspace/libscap/engine/bpf/bpf_public.h b/userspace/libscap/engine/bpf/bpf_public.h
@@ -16,7 +16,6 @@ limitations under the License.
 #include <stdint.h>
 
 #define BPF_ENGINE "bpf"
-#define BPF_ENGINE_LEN 4
 
 #ifdef __cplusplus
 extern "C"

diff --git a/userspace/libscap/engine/bpf/scap_bpf.c b/userspace/libscap/engine/bpf/scap_bpf.c
@@ -87,7 +87,7 @@ struct bpf_map_data {
 
 static bool match(scap_open_args* oargs)
 {
-	return strncmp(oargs->engine_name, BPF_ENGINE, BPF_ENGINE_LEN) == 0;
+	return strcmp(oargs->engine_name, BPF_ENGINE) == 0;
 }
 
 static struct bpf_engine* alloc_handle(scap_t* main_handle, char* lasterr_ptr)
@@ -105,8 +105,6 @@ static void free_handle(struct scap_engine_handle engine)
 	free(engine.m_handle);
 }
 
-#ifndef MINIMAL_BUILD
-
 # define UINT32_MAX (4294967295U)
 
 /* Recommended log buffer size. 
@@ -1781,36 +1779,3 @@ const struct scap_vtable scap_bpf_engine = {
 	.get_vtid = noop_get_vxid,
 	.getpid_global = scap_os_getpid_global,
 };
-
-#else // MINIMAL_BUILD
-
-static int32_t init(scap_t* handle, scap_open_args *oargs)
-{
-	strlcpy(handle->m_lasterr, "The eBPF probe driver is not supported when using a minimal build", SCAP_LASTERR_SIZE);
-	return SCAP_NOT_SUPPORTED;
-}
-
-const struct scap_vtable scap_bpf_engine = {
-	.name = "bpf",
-	.mode = SCAP_MODE_LIVE,
-	.savefile_ops = NULL,
-
-	.match = match,
-	.alloc_handle = alloc_handle,
-	.init = init,
-	.free_handle = free_handle,
-	.close = noop_close_engine,
-	.next = noop_next,
-	.start_capture = noop_start_capture,
-	.stop_capture = noop_stop_capture,
-	.configure = noop_configure,
-	.get_stats = noop_get_stats,
-	.get_n_tracepoint_hit = noop_get_n_tracepoint_hit,
-	.get_n_devs = noop_get_n_devs,
-	.get_max_buf_used = noop_get_max_buf_used,
-	.get_threadlist = noop_get_threadlist,
-	.get_vpid = noop_get_vxid,
-	.get_vtid = noop_get_vxid,
-	.getpid_global = noop_getpid_global,
-};
-#endif // MINIMAL_BUILD
diff --git a/userspace/libscap/engine/gvisor/gvisor.cpp b/userspace/libscap/engine/gvisor/gvisor.cpp
@@ -79,7 +79,7 @@ static int32_t gvisor_next(struct scap_engine_handle engine, scap_evt **pevent,
 
 static bool gvisor_match(scap_open_args* oargs)
 {
-	return strncmp(oargs->engine_name, GVISOR_ENGINE, GVISOR_ENGINE_LEN) == 0;
+	return strcmp(oargs->engine_name, GVISOR_ENGINE) == 0;
 }
 
 static int32_t gvisor_configure(struct scap_engine_handle engine, enum scap_setting setting, unsigned long arg1, unsigned long arg2)

diff --git a/userspace/libscap/engine/gvisor/gvisor_public.h b/userspace/libscap/engine/gvisor/gvisor_public.h
@@ -14,7 +14,6 @@ limitations under the License.
 #pragma once
 
 #define GVISOR_ENGINE "gvisor"
-#define GVISOR_ENGINE_LEN 7
 
 #ifdef __cplusplus
 extern "C"

diff --git a/userspace/libscap/engine/kmod/kmod_public.h b/userspace/libscap/engine/kmod/kmod_public.h
@@ -16,7 +16,6 @@ limitations under the License.
 #include <stdint.h>
 
 #define KMOD_ENGINE "kmod"
-#define KMOD_ENGINE_LEN 5
 
 #ifdef __cplusplus
 extern "C"

diff --git a/userspace/libscap/engine/kmod/scap_kmod.c b/userspace/libscap/engine/kmod/scap_kmod.c
@@ -37,7 +37,7 @@ limitations under the License.
 
 static bool match(scap_open_args* oargs)
 {
-	return strncmp(oargs->engine_name, KMOD_ENGINE, KMOD_ENGINE_LEN) == 0;
+	return strcmp(oargs->engine_name, KMOD_ENGINE) == 0;
 }
 
 static struct kmod_engine* alloc_handle(scap_t* main_handle, char* lasterr_ptr)

diff --git a/userspace/libscap/engine/modern_bpf/modern_bpf_public.h b/userspace/libscap/engine/modern_bpf/modern_bpf_public.h
@@ -16,7 +16,6 @@ limitations under the License.
 #include <stdint.h>
 
 #define MODERN_BPF_ENGINE "modern_bpf"
-#define MODERN_BPF_ENGINE_LEN 11
 
 #ifdef __cplusplus
 extern "C"

diff --git a/userspace/libscap/engine/modern_bpf/scap_modern_bpf.c b/userspace/libscap/engine/modern_bpf/scap_modern_bpf.c
@@ -115,7 +115,7 @@ static int32_t populate_64bit_interesting_syscalls_table(bool* ppm_sc_array)
 /* Right now this is not used */
 bool scap_modern_bpf__match(scap_open_args* oargs)
 {
-	return strncmp(oargs->engine_name, MODERN_BPF_ENGINE, MODERN_BPF_ENGINE_LEN) == 0;
+	return strcmp(oargs->engine_name, MODERN_BPF_ENGINE) == 0;
 }
 
 static struct modern_bpf_engine* scap_modern_bpf__alloc_engine(scap_t* main_handle, char* lasterr_ptr)

diff --git a/userspace/libscap/engine/nodriver/nodriver_public.h b/userspace/libscap/engine/nodriver/nodriver_public.h
@@ -14,4 +14,3 @@ limitations under the License.
 #pragma once
 
 #define NODRIVER_ENGINE "nodriver"
-#define NODRIVER_ENGINE_LEN 9
diff --git a/userspace/libscap/engine/savefile/savefile_public.h b/userspace/libscap/engine/savefile/savefile_public.h
@@ -16,7 +16,6 @@ limitations under the License.
 #include <stdint.h>
 
 #define SAVEFILE_ENGINE "savefile"
-#define SAVEFILE_ENGINE_LEN 9
 
 #ifdef __cplusplus
 extern "C"

diff --git a/userspace/libscap/engine/savefile/scap_savefile.c b/userspace/libscap/engine/savefile/scap_savefile.c
@@ -2031,7 +2031,7 @@ void scap_savefile_fseek(struct scap_engine_handle engine, uint64_t off)
 
 static bool match(struct scap_open_args* oargs)
 {
-	return strncmp(oargs->engine_name, SAVEFILE_ENGINE, SAVEFILE_ENGINE_LEN) == 0;
+	return strcmp(oargs->engine_name, SAVEFILE_ENGINE) == 0;
 }
 
 static struct savefile_engine* alloc_handle(struct scap* main_handle, char* lasterr_ptr)

diff --git a/userspace/libscap/engine/source_plugin/source_plugin_public.h b/userspace/libscap/engine/source_plugin/source_plugin_public.h
@@ -16,7 +16,6 @@ limitations under the License.
 #include "../../plugin_info.h"
 
 #define SOURCE_PLUGIN_ENGINE "source_plugin"
-#define SOURCE_PLUGIN_ENGINE_LEN 14
 
 #ifdef __cplusplus
 extern "C"

diff --git a/userspace/libscap/engine/test_input/test_input_public.h b/userspace/libscap/engine/test_input/test_input_public.h
@@ -16,7 +16,6 @@ limitations under the License.
 #include "../../scap_test.h"
 
 #define TEST_INPUT_ENGINE "test_input"
-#define TEST_INPUT_ENGINE_LEN 11
 
 #ifdef __cplusplus
 extern "C"

diff --git a/userspace/libscap/engine/udig/scap_udig.c b/userspace/libscap/engine/udig/scap_udig.c
@@ -843,7 +843,7 @@ static int32_t configure(struct scap_engine_handle engine, enum scap_setting set
 
 static bool match(scap_open_args* oargs)
 {
-	return strncmp(oargs->engine_name, UDIG_ENGINE, UDIG_ENGINE_LEN) == 0;
+	return strcmp(oargs->engine_name, UDIG_ENGINE) == 0;
 }
 
 static struct udig_engine* alloc_handle(scap_t* main_handle, char* lasterr_ptr)

diff --git a/userspace/libscap/engine/udig/udig_public.h b/userspace/libscap/engine/udig/udig_public.h
@@ -16,7 +16,6 @@ limitations under the License.
 #include <stdint.h>
 
 #define UDIG_ENGINE "udig"
-#define UDIG_ENGINE_LEN 5
 
 #ifdef __cplusplus
 extern "C"

diff --git a/userspace/libscap/scap.c b/userspace/libscap/scap.c
@@ -111,23 +111,31 @@ scap_t* scap_open_live_int(char *error, int32_t *rc, scap_open_args* oargs)
 	// Preliminary initializations
 	//
 	handle->m_mode = SCAP_MODE_LIVE;
-	if(strncmp(oargs->engine_name, BPF_ENGINE, BPF_ENGINE_LEN) == 0)
+	if (false)
+	{
+
+	}
+#ifdef HAS_ENGINE_BPF
+	else if(strcmp(oargs->engine_name, BPF_ENGINE) == 0)
 	{
 		handle->m_vtable = &scap_bpf_engine;
 	}
-	else if(strncmp(oargs->engine_name, KMOD_ENGINE, KMOD_ENGINE_LEN) == 0)
+#endif
+#ifdef HAS_ENGINE_KMOD
+	else if(strcmp(oargs->engine_name, KMOD_ENGINE) == 0)
 	{
 		handle->m_vtable = &scap_kmod_engine;
 	}
+#endif
 #ifdef HAS_ENGINE_MODERN_BPF
-	else if(strncmp(oargs->engine_name, MODERN_BPF_ENGINE, MODERN_BPF_ENGINE_LEN) == 0)
+	else if(strcmp(oargs->engine_name, MODERN_BPF_ENGINE) == 0)
 	{
 		handle->m_vtable = &scap_modern_bpf_engine;
 	}
 #endif /* HAS_ENGINE_MODERN_BPF */
 	else
 	{
-		snprintf(error, SCAP_LASTERR_SIZE, "libscap: unknown engine called `scap_open_live_int()`");
+		snprintf(error, SCAP_LASTERR_SIZE, "libscap: unknown engine '%s' called `scap_open_live_int()`", oargs->engine_name);
 		*rc = SCAP_FAILURE;
 		return NULL;
 	}
@@ -886,38 +894,38 @@ scap_t* scap_open(scap_open_args* oargs, char *error, int32_t *rc)
 	 * with an internal switch that selects the right vtable! For the moment
 	 * let's keep different functions.
 	 */
-	if(strncmp(engine_name, SAVEFILE_ENGINE, SAVEFILE_ENGINE_LEN) == 0)
+	if(strcmp(engine_name, SAVEFILE_ENGINE) == 0)
 	{
 		return scap_open_offline_int(oargs, rc, error);
 	}
-	else if(strncmp(engine_name, UDIG_ENGINE, UDIG_ENGINE_LEN) == 0)
+	else if(strcmp(engine_name, UDIG_ENGINE) == 0)
 	{
 		return scap_open_udig_int(error, rc, oargs->proc_callback,
 								oargs->proc_callback_context,
 								oargs->import_users,
 								oargs->suppressed_comms);
 	}
-	else if(strncmp(engine_name, GVISOR_ENGINE, GVISOR_ENGINE_LEN) == 0)
+	else if(strcmp(engine_name, GVISOR_ENGINE) == 0)
 	{
 		return scap_open_gvisor_int(error, rc, oargs);
 	}
-	else if(strncmp(engine_name, TEST_INPUT_ENGINE, TEST_INPUT_ENGINE_LEN) == 0)
+	else if(strcmp(engine_name, TEST_INPUT_ENGINE) == 0)
 	{
 		return scap_open_test_input_int(error, rc, oargs);
 	}
-	else if(strncmp(engine_name, KMOD_ENGINE, KMOD_ENGINE_LEN) == 0 ||
-			strncmp(engine_name, BPF_ENGINE, BPF_ENGINE_LEN) == 0 ||
-			strncmp(engine_name, MODERN_BPF_ENGINE, MODERN_BPF_ENGINE_LEN) == 0)
+	else if(strcmp(engine_name, KMOD_ENGINE) == 0 ||
+			strcmp(engine_name, BPF_ENGINE) == 0 ||
+			strcmp(engine_name, MODERN_BPF_ENGINE) == 0)
 	{
 		return scap_open_live_int(error, rc, oargs);
 	}
-	else if(strncmp(engine_name, NODRIVER_ENGINE, NODRIVER_ENGINE_LEN) == 0)
+	else if(strcmp(engine_name, NODRIVER_ENGINE) == 0)
 	{
 		return scap_open_nodriver_int(error, rc, oargs->proc_callback,
 					      oargs->proc_callback_context,
 					      oargs->import_users);
 	}
-	else if(strncmp(engine_name, SOURCE_PLUGIN_ENGINE, SOURCE_PLUGIN_ENGINE_LEN) == 0)
+	else if(strcmp(engine_name, SOURCE_PLUGIN_ENGINE) == 0)
 	{
 		return scap_open_plugin_int(error, rc, oargs);
 	}
Original file line number	Diff line number	Diff line change
Expand Up		@@ -14,4 +14,3 @@ limitations under the License.
		#pragma once

		#define NODRIVER_ENGINE "nodriver"
		#define NODRIVER_ENGINE_LEN 9