fix: memory safety — malloc NULL checks, strcpy→memcpy

src/shared/config.c

@@ -14,6 +14,7 @@ Config* config_create(char* version, char* send_directory, char* receive_directo
                       bool use_sendfile, unsigned long long chunk_size) {
 
   Config* config = malloc(sizeof(Config));
+  if (config == NULL) return NULL;
   config->version = version;
   config->send_directory = send_directory;
   config->receive_root_directory = receive_directory;

src/shared/file.c

@@ -34,7 +34,7 @@ File* file_create(const char* path) {
     return NULL;
   }
 
-  strcpy(file->path, path);
+  memcpy(file->path, path, path_len + 1);
   file->data = data_create_reserve(0);
   if (file->data == NULL) {
     free(file->path);

src/shared/metadata.c

@@ -54,6 +54,7 @@ FileMetadata* metadata_from_buf(char** buf) {
   if (!present)
     return NULL;
   FileMetadata* m = malloc(sizeof(FileMetadata));
+  if (m == NULL) return NULL;
   int32_t mode;
   memcpy(&mode, *buf, sizeof(mode));
   *buf += sizeof(mode);

src/shared/utils.c

@@ -54,7 +54,7 @@ char* str_dup(const char* string) {
   if (string == NULL)
     return NULL;
   char* new_string = (char*)malloc(strlen(string) + 1);
-  strcpy(new_string, string);
+  memcpy(new_string, string, strlen(string) + 1);
   return new_string;
 }