Kernel: Implement unveil() as a prefix-tree

Fixes #4530.

Userland/test-unveil.cpp

@@ -0,0 +1,86 @@
+/*
+ * Copyright (c) 2020, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <LibCore/ArgsParser.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int main(int argc, char** argv)
+{
+    Vector<StringView> paths_to_test;
+    const char* permissions = "r";
+    bool should_sleep = false;
+
+    Core::ArgsParser parser;
+    parser.add_option(permissions, "Apply these permissions going forward", "permissions", 'p', "unveil-permissions");
+    parser.add_option(should_sleep, "Sleep after processing all arguments", "sleep", 's');
+    parser.add_option(Core::ArgsParser::Option {
+        .requires_argument = true,
+        .help_string = "Add a path to the unveil list",
+        .long_name = "unveil",
+        .short_name = 'u',
+        .value_name = "path",
+        .accept_value = [&](auto* s) {
+            StringView path { s };
+            if (path.is_empty())
+                return false;
+            if (unveil(s, permissions) < 0) {
+                perror("unveil");
+                return false;
+            }
+            return true;
+        } });
+    parser.add_option(Core::ArgsParser::Option {
+        .requires_argument = false,
+        .help_string = "Lock the veil",
+        .long_name = "lock",
+        .short_name = 'l',
+        .accept_value = [&](auto*) {
+            if (unveil(nullptr, nullptr) < 0) {
+                perror("unveil(nullptr, nullptr)");
+                return false;
+            }
+            return true;
+        } });
+    parser.add_positional_argument(Core::ArgsParser::Arg {
+        .help_string = "Test a path against the veil",
+        .name = "path",
+        .min_values = 0,
+        .max_values = INT_MAX,
+        .accept_value = [&](auto* s) {
+            if (access(s, X_OK) == 0)
+                warnln("'{}' - ok", s);
+            else
+                warnln("'{}' - fail: {}", s, strerror(errno));
+            return true;
+        } });
+
+    parser.parse(argc, argv);
+    if (should_sleep)
+        sleep(INT_MAX);
+    return 0;
+}