Fix Segmentation fault if HOME not set

README.md

@@ -181,10 +181,20 @@ This feature was implemented due to Github
 ## Permanent cache system
 
 You can cache the files you have accessed permanently on your hard drive by
-using the ``--cache`` flag. The file it caches persist across sessions.
+using the ``--cache`` flag. The file it caches persist across sessions, but
+can clear the cache using ``--cache-clear``
+
+> [!WARNING]
+> If ``--cache-location <dir>`` appears before ``--cache-clear``, the entire
+> directory  ``<dir>`` will be deleted instead. Take caution when specifying
+> non-empty directories to be used as cache.
 
 By default, the cache files are stored under ``${XDG_CACHE_HOME}/httpdirfs``,
-which by default is ``${HOME}/.cache/httpdirfs``. Each HTTP directory gets its
+``${HOME}/.cache/httpdirfs``, or the current working directory ``./.cache``,
+whichever is found first. By default, ``${XDG_CACHE_HOME}/httpdirfs`` is
+normally ``${HOME}/.cache/httpdirfs``.
+
+Each HTTP directory gets its
 own cache folder, they are named using the escaped URL of the HTTP directory.
 
 Once a segment of the file has been downloaded once, it won't be downloaded

src/cache.c

@@ -35,26 +35,46 @@
  */
 static char *DATA_DIR;
 
-static char *CacheSystem_get_cache_home()
+
+char *CacheSystem_get_cache_dir()
 {
     if (CONFIG.cache_dir) {
         return CONFIG.cache_dir;
     }
-    char *xdg_cache_home = getenv("XDG_CACHE_HOME");
-    if (!xdg_cache_home) {
-        char *home = getenv("HOME");
-        char *xdg_cache_home_default = "/.cache";
-        xdg_cache_home = path_append(home, xdg_cache_home_default);
+
+    const char *default_cache_subdir = "/.cache";
+    char *cache_dir = NULL;
+
+    const char *xdg_cache_home = getenv("XDG_CACHE_HOME");
+    if (xdg_cache_home) {
+        cache_dir = strndup(xdg_cache_home, MAX_PATH_LEN);
+    } else {
+        const char *user_home = getenv("HOME");
+        if (user_home) {
+            cache_dir = path_append(user_home, default_cache_subdir);
+        } else {
+            lprintf(warning, "$HOME is unset\n");
+            /*
+             * XDG_CACHE_HOME and HOME already are full paths. Not relying
+             * on environment PWD since it too may be undefined.
+             */
+            const char *cur_dir = realpath("./", NULL);
+            if (cur_dir) {
+                cache_dir = path_append(cur_dir, default_cache_subdir);
+            } else {
+                lprintf(fatal, "Could not create cache directory\n");
+            }
+        }
     }
-    return xdg_cache_home;
+    return cache_dir;
 }
 
 /**
  * \brief Calculate cache system directory path
  */
 static char *CacheSystem_calc_dir(const char *url)
 {
-    char *cache_home = CacheSystem_get_cache_home();
+    char *cache_home = CacheSystem_get_cache_dir();
 
     if (mkdir
             (cache_home, S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH)
@@ -92,6 +112,7 @@
         lprintf(fatal, "mkdir(): %s\n", strerror(errno));
     }
     FREE(fn);
+    FREE(cache_home);
     FREE(cache_dir_root);
     curl_free(escaped_url);
     curl_easy_cleanup(c);
@@ -163,22 +184,18 @@
     return remove(fpath);
 }
 
-void CacheSystem_clear(const char *path)
+void CacheSystem_clear()
 {
-    char *cache_root_dir;
-    if (path) {
-        cache_root_dir = strdup(path);
+    char *cache_home = CacheSystem_get_cache_dir();
+    const char *cache_del;
+    lprintf(debug, "%s\n", cache_home);
+    if (CONFIG.cache_dir) {
+        cache_del = cache_home;
     } else {
-        char *cache_home = CacheSystem_get_cache_home();
-        cache_root_dir = path_append(cache_home, "/httpdirfs/");
-        FREE(cache_home);
+        cache_del = path_append(cache_home, "/httpdirfs/");
     }
-
-    lprintf(debug, "%s\n", path);
-
-    nftw(cache_root_dir, ntfw_cb, 64, FTW_DEPTH | FTW_PHYS | FTW_MOUNT);
-    FREE(cache_root_dir);
-
+    nftw(cache_del, ntfw_cb, 64, FTW_DEPTH | FTW_PHYS | FTW_MOUNT);
+    FREE(cache_home);
     exit(EXIT_SUCCESS);
 }
 

src/cache.h

@@ -95,7 +95,12 @@ void CacheSystem_init(const char *path, int url_supplied);
 /**
  * \brief clear the content of the cache directory
  */
-void CacheSystem_clear(const char *path);
+void CacheSystem_clear();
+
+/**
+ * \brief Return the fullpath to the cache directory
+ */
+char *CacheSystem_get_cache_dir();
 
 /**
  * \brief Create directories under the cache directory structure, if they do
@@ -148,4 +153,4 @@ void Cache_delete(const char *fn);
  */
 long Cache_read(Cache *cf, char *const output_buf, const off_t len,
                 const off_t offset_start);
-#endif
+#endif

src/main.c

@@ -114,17 +114,38 @@
     return 0;
 }
 
+static char *get_XDG_CONFIG_HOME()
+{
+    const char *default_config_subdir = "/.config";
+    char *config_dir = NULL;
+
+    const char *xdg_config_home = getenv("XDG_CONFIG_HOME");
+    if (xdg_config_home) {
+        config_dir = strndup(xdg_config_home, MAX_PATH_LEN);
+    } else {
+        const char *user_home = getenv("HOME");
+        if (user_home) {
+            config_dir = path_append(user_home, default_config_subdir);
+        } else {
+            lprintf(warning, "$HOME is unset\n");
+            const char *cur_dir = realpath("./", NULL);
+            if (cur_dir) {
+                config_dir = path_append(cur_dir, default_config_subdir);
+            } else {
+                lprintf(warning, "Could not get config directory\n");
+            }
+        }
+    }
+    return config_dir;
+}
+
 void parse_config_file(char ***argv, int *argc)
 {
     char *full_path;
     if (!config_path) {
-        char *xdg_config_home = getenv("XDG_CONFIG_HOME");
-        if (!xdg_config_home) {
-            char *home = getenv("HOME");
-            char *xdg_config_home_default = "/.config";
-            xdg_config_home = path_append(home, xdg_config_home_default);
-        }
+        char *xdg_config_home = get_XDG_CONFIG_HOME();
         full_path = path_append(xdg_config_home, "/httpdirfs/config");
+        FREE(xdg_config_home);
     } else {
         full_path = config_path;
     }
@@ -316,11 +337,7 @@
                     curl_slist_append(CONFIG.http_headers, strdup(optarg));
                 break;
             case 27:
-                if (CONFIG.cache_dir) {
-                    CacheSystem_clear(CONFIG.cache_dir);
-                } else {
-                    CacheSystem_clear(NULL);
-                }
+                CacheSystem_clear();
                 break;
             default:
                 fprintf(stderr, "see httpdirfs -h for usage\n");
@@ -377,7 +394,9 @@
         --cache             Enable cache (default: off)\n\
         --cache-location    Set a custom cache location\n\
                             (default: \"${XDG_CACHE_HOME}/httpdirfs\")\n\
-        --cache-clear       Clear cache directory and exit\n\
+        --cache-clear       Delete the cache directory or the custom location\n\
+                            specifid with `--cache-location`, if the option is\n\
+                            seen first. Then exit in either case.\n\
         --cacert            Certificate authority for the server\n\
         --dl-seg-size       Set cache download segment size, in MB (default: 8)\n\
                             Note: this setting is ignored if previously\n\
@@ -412,4 +431,4 @@
                             using the insecure username / hex encoded password\n\
                             scheme\n\
 \n");
-}
+}