Find usermountN using execve and set FUSERMOUNT_PROG if not set

Author: probonopd

src/runtime/runtime.c

@@ -405,6 +405,61 @@ int appimage_print_binary(char* fname, unsigned long offset, unsigned long lengt
 	return 0;
 }
 
+char* find_fusermount() {
+    char* fusermount_base = "fusermount";
+    int i = 0;
+
+    char* fusermount_path = getenv("PATH");
+    if (fusermount_path == NULL) {
+        return NULL;
+    }
+
+    char* path_copy = strdup(fusermount_path);
+    char* dir = strtok(path_copy, ":");
+
+    while (dir != NULL) {
+        DIR* dir_ptr = opendir(dir);
+        if (dir_ptr == NULL) {
+            dir = strtok(NULL, ":");
+            continue;
+        }
+
+        struct dirent* entry;
+        while ((entry = readdir(dir_ptr)) != NULL) {
+            // Check if the entry starts with "fusermount"
+            if (strncmp(entry->d_name, fusermount_base, 10) == 0) {
+                // Check if the rest of the entry is a digit
+                char* suffix = entry->d_name + 10;
+                int j = 0;
+                while (suffix[j] != '\0' && isdigit(suffix[j])) {
+                    j++;
+                }
+
+                if (suffix[j] == '\0') {
+                    // Construct the full path of the entry
+                    char* fusermount_full_path = malloc(strlen(dir) + strlen(entry->d_name) + 2);
+                    sprintf(fusermount_full_path, "%s/%s", dir, entry->d_name);
+
+                    // Check if the entry is executable
+                    if (access(fusermount_full_path, X_OK) == 0) {
+                        closedir(dir_ptr);
+                        free(path_copy);
+                        return fusermount_full_path;
+                    }
+
+                    free(fusermount_full_path);
+                }
+            }
+        }
+
+        closedir(dir_ptr);
+        dir = strtok(NULL, ":");
+    }
+
+    free(path_copy);
+    return NULL;
+}
+
 /* Exit status to use when launching an AppImage fails.
  * For applications that assign meanings to exit status codes (e.g. rsync),
  * we avoid "cluttering" pre-defined exit status codes by using 127 which
@@ -474,6 +529,20 @@ sqfs_err private_sqfs_stat(sqfs* fs, sqfs_inode* inode, struct stat* st) {
 
 /* ================= End ELF parsing */
 
+char* fusermount_prog = getenv("FUSERMOUNT_PROG");
+if (fusermount_prog == NULL) {
+fusermount_prog = find_fusermount();
+if (fusermount_prog != NULL) {
+    setenv("FUSERMOUNT_PROG", fusermount_prog, 1);
+    // printf("FUSERMOUNT_PROG set to %s\n", fusermount_prog);
+    free(fusermount_prog);
+} else {
+    printf("Error: fusermount not found\n");
+}
+} else {
+printf("FUSERMOUNT_PROG is already set to %s\n", fusermount_prog);
+}
+
 extern int fusefs_main(int argc, char* argv[], void (* mounted)(void));
 // extern void ext2_quit(void);