From b6c432ca7ed930c7e9078ac2266ae439aa242632 Mon Sep 17 00:00:00 2001
From: Djalal Harouni <tixxdz@opendz.org>
Date: Sun, 25 Sep 2016 12:41:16 +0200
Subject: core:namespace: simplify ProtectHome= implementation

As with previous patch simplify ProtectHome and don't care about
duplicates, they will be sorted by most restrictive mode and cleaned.
---
 src/core/namespace.c | 75 +++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 53 insertions(+), 22 deletions(-)

(limited to 'src/core/namespace.c')

diff --git a/src/core/namespace.c b/src/core/namespace.c
index 985e343096..43a2f4ba6e 100644
--- a/src/core/namespace.c
+++ b/src/core/namespace.c
@@ -97,6 +97,23 @@ static const TargetMount protect_kernel_tunables_table[] = {
         { "/sys/fs/cgroup",             READWRITE,      false }, /* READONLY is set by ProtectControlGroups= option */
 };
 
+/*
+ * ProtectHome=read-only table, protect $HOME and $XDG_RUNTIME_DIR and rest of
+ * system should be protected by ProtectSystem=
+ */
+static const TargetMount protect_home_read_only_table[] = {
+        { "/home",      READONLY,       true },
+        { "/run/user",  READONLY,       true },
+        { "/root",      READONLY,       true },
+};
+
+/* ProtectHome=yes table */
+static const TargetMount protect_home_yes_table[] = {
+        { "/home",      INACCESSIBLE,   true },
+        { "/run/user",  INACCESSIBLE,   true },
+        { "/root",      INACCESSIBLE,   true },
+};
+
 /* ProtectSystem=yes table */
 static const TargetMount protect_system_yes_table[] = {
         { "/usr",       READONLY,       false },
@@ -190,6 +207,31 @@ static int append_protect_kernel_tunables(BindMount **p, const char *root_direct
                                     ELEMENTSOF(protect_kernel_tunables_table));
 }
 
+static int append_protect_home(BindMount **p, const char *root_directory, ProtectHome protect_home) {
+        int r = 0;
+
+        assert(p);
+
+        if (protect_home == PROTECT_HOME_NO)
+                return 0;
+
+        switch (protect_home) {
+        case PROTECT_HOME_READ_ONLY:
+                r = append_target_mounts(p, root_directory, protect_home_read_only_table,
+                                         ELEMENTSOF(protect_home_read_only_table));
+                break;
+        case PROTECT_HOME_YES:
+                r = append_target_mounts(p, root_directory, protect_home_yes_table,
+                                         ELEMENTSOF(protect_home_yes_table));
+                break;
+        default:
+                r = -EINVAL;
+                break;
+        }
+
+        return r;
+}
+
 static int append_protect_system(BindMount **p, const char *root_directory, ProtectSystem protect_system) {
         int r = 0;
 
@@ -629,6 +671,7 @@ static unsigned namespace_calculate_mounts(
                 ProtectHome protect_home,
                 ProtectSystem protect_system) {
 
+        unsigned protect_home_cnt;
         unsigned protect_system_cnt =
                 (protect_system == PROTECT_SYSTEM_STRICT ?
                  ELEMENTSOF(protect_system_strict_table) :
@@ -637,6 +680,12 @@ static unsigned namespace_calculate_mounts(
                   ((protect_system == PROTECT_SYSTEM_YES) ?
                    ELEMENTSOF(protect_system_yes_table) : 0)));
 
+        protect_home_cnt =
+                (protect_home == PROTECT_HOME_YES ?
+                 ELEMENTSOF(protect_home_yes_table) :
+                 ((protect_home == PROTECT_HOME_READ_ONLY) ?
+                  ELEMENTSOF(protect_home_read_only_table) : 0));
+
         return !!tmp_dir + !!var_tmp_dir +
                 strv_length(read_write_paths) +
                 strv_length(read_only_paths) +
@@ -644,8 +693,7 @@ static unsigned namespace_calculate_mounts(
                 private_dev +
                 (protect_sysctl ? ELEMENTSOF(protect_kernel_tunables_table) : 0) +
                 (protect_cgroups ? 1 : 0) +
-                (protect_home != PROTECT_HOME_NO || protect_system == PROTECT_SYSTEM_STRICT ? 3 : 0) +
-                protect_system_cnt;
+                protect_home_cnt + protect_system_cnt;
 }
 
 int setup_namespace(
@@ -723,26 +771,9 @@ int setup_namespace(
                         m++;
                 }
 
-                if (protect_home != PROTECT_HOME_NO || protect_system == PROTECT_SYSTEM_STRICT) {
-                        const char *home_dir, *run_user_dir, *root_dir;
-
-                        /* If protection of $HOME and $XDG_RUNTIME_DIR is requested, then go for it. If we are in
-                         * strict system protection mode, then also add entries for these directories, but mark them
-                         * writable. This is because we want ProtectHome= and ProtectSystem= to be fully orthogonal. */
-
-                        home_dir = prefix_roota(root_directory, "/home");
-                        home_dir = strjoina("-", home_dir);
-                        run_user_dir = prefix_roota(root_directory, "/run/user");
-                        run_user_dir = strjoina("-", run_user_dir);
-                        root_dir = prefix_roota(root_directory, "/root");
-                        root_dir = strjoina("-", root_dir);
-
-                        r = append_mounts(&m, STRV_MAKE(home_dir, run_user_dir, root_dir),
-                                protect_home == PROTECT_HOME_READ_ONLY ? READONLY :
-                                protect_home == PROTECT_HOME_YES ? INACCESSIBLE : READWRITE);
-                        if (r < 0)
-                                return r;
-                }
+                r = append_protect_home(&m, root_directory, protect_home);
+                if (r < 0)
+                        return r;
 
                 r = append_protect_system(&m, root_directory, protect_system);
                 if (r < 0)
-- 
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