fuzz: Simplify definition of fuzzing targets and build them also with gcc

Signed-off-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>

tests/fuzz/CMakeLists.txt

@@ -1,26 +1,23 @@
 project(fuzzing CXX)
 
-if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
-    add_executable(ssh_client_fuzzer ssh_client_fuzzer.cpp)
-    target_link_libraries(ssh_client_fuzzer
+macro(fuzzer name)
+    add_executable(${name} ${name}.cpp)
+    target_link_libraries(${name}
                           PRIVATE
                               ssh::static)
-    set_target_properties(ssh_client_fuzzer
-                          PROPERTIES
-                              COMPILE_FLAGS "-fsanitize=fuzzer"
-                              LINK_FLAGS "-fsanitize=fuzzer")
+    if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+        set_target_properties(${name}
+                              PROPERTIES
+                                  COMPILE_FLAGS "-fsanitize=fuzzer"
+                                  LINK_FLAGS "-fsanitize=fuzzer")
+        # Run the fuzzer to make sure it works
+        add_test(${name} ${CMAKE_CURRENT_BINARY_DIR}/${name} -runs=1)
+    else()
+        target_sources(${name} PRIVATE fuzzer.c)
+        # Run the fuzzer to make sure it works
+        # add_test(${name} ${CMAKE_CURRENT_BINARY_DIR}/${name} EXAMPLE)
+    endif()
+endmacro()
 
-
-    add_executable(ssh_server_fuzzer ssh_server_fuzzer.cpp)
-    target_link_libraries(ssh_server_fuzzer
-                          PRIVATE
-                              ssh::static)
-    set_target_properties(ssh_server_fuzzer
-        PROPERTIES
-            COMPILE_FLAGS "-fsanitize=fuzzer"
-            LINK_FLAGS "-fsanitize=fuzzer")
-
-    # Run the fuzzer to make sure it works
-    add_test(ssh_client_fuzzer ${CMAKE_CURRENT_BINARY_DIR}/ssh_client_fuzzer -runs=1)
-    add_test(ssh_server_fuzzer ${CMAKE_CURRENT_BINARY_DIR}/ssh_server_fuzzer -runs=1)
-endif()
+fuzzer(ssh_client_fuzzer)
+fuzzer(ssh_server_fuzzer)

tests/fuzz/fuzzer.c

@@ -0,0 +1,39 @@
+/* Simpler gnu89 version of StandaloneFuzzTargetMain.c from LLVM */
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+int LLVMFuzzerTestOneInput (const unsigned char *data, size_t size);
+__attribute__((weak)) int LLVMFuzzerInitialize(int *argc, char ***argv);
+
+int
+main (int argc, char **argv)
+{
+    FILE *f = NULL;
+    size_t n_read, len;
+    unsigned char *buf = NULL;
+
+    if (argc < 2) {
+        return 1;
+    }
+
+    if (LLVMFuzzerInitialize) {
+        LLVMFuzzerInitialize(&argc, &argv);
+    }
+
+    f = fopen (argv[1], "r");
+    assert (f);
+    fseek (f, 0, SEEK_END);
+    len = ftell (f);
+    fseek (f, 0, SEEK_SET);
+    buf = (unsigned char*) malloc (len);
+    n_read = fread (buf, 1, len, f);
+    fclose (f);
+    assert (n_read == len);
+    LLVMFuzzerTestOneInput (buf, len);
+
+    free (buf);
+    printf ("Done!\n");
+    return 0;
+}