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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] Implement watching of nodes which don't exist.
# HG changeset patch
# User cl349@xxxxxxxxxxxxxxxxxxxx
# Node ID 5eead9930294f699f8feb9f7f5b157cb9c607b69
# Parent a05338d886d9e43996c4061d912a15cc93ef145c
Implement watching of nodes which don't exist.
Requires permission check every time event is generated.
Requires generalization of permissions: ask arbitrary number of
parents whether it's OK to tell about node (eg. watching
/dir/subdir/x when /dir is deleted: root permissions will now
determine whether we fire event).
Add test that we don't leak information on whether a file exists
or not.
Signed-off-by: Rusty Russel <rusty@xxxxxxxxxxxxxxx>
Signed-off-by: Christian Limpach <Christian.Limpach@xxxxxxxxxxxx>
diff -r a05338d886d9 -r 5eead9930294 tools/xenstore/testsuite/07watch.sh
--- a/tools/xenstore/testsuite/07watch.sh Tue Aug 2 18:04:00 2005
+++ b/tools/xenstore/testsuite/07watch.sh Tue Aug 2 18:04:28 2005
@@ -160,3 +160,22 @@
1 waitwatch' | ./xs_test 2>&1`" = "1:/test2/foo:token
1:contents2
1:waitwatch timeout" ]
+
+# We can watch something which doesn't exist.
+[ "`echo '1 watch /dir/subdir token
+2 mkdir /dir/subdir
+1 waitwatch' | ./xs_test 2>&1`" = "1:/dir/subdir:token" ]
+
+# If we don't have permission, we won't see event (rm).
+[ "`echo '1 setid 1
+1 watch /dir/subdir token
+setperm /dir 0 NONE
+rm /dir/subdir
+1 waitwatch' | ./xs_test 2>&1`" = "1:waitwatch timeout" ]
+
+# If we don't have permission, we won't see event (create).
+[ "`echo '1 setid 1
+1 watch /dir/subdir token
+mkdir /dir/subdir
+write /dir/subdir/entry create contents
+1 waitwatch' | ./xs_test 2>&1`" = "1:waitwatch timeout" ]
diff -r a05338d886d9 -r 5eead9930294 tools/xenstore/xenstored_core.c
--- a/tools/xenstore/xenstored_core.c Tue Aug 2 18:04:00 2005
+++ b/tools/xenstore/xenstored_core.c Tue Aug 2 18:04:28 2005
@@ -707,7 +707,7 @@
/* Owners and tools get it all... */
if (!id || perms[0].id == id)
- return XS_PERM_READ|XS_PERM_WRITE|XS_PERM_CREATE|XS_PERM_OWNER;
+ return XS_PERM_READ|XS_PERM_WRITE|XS_PERM_OWNER;
for (i = 1; i < num; i++)
if (perms[i].id == id)
@@ -716,19 +716,12 @@
return perms[0].perms;
}
-/* We have a weird permissions system. You can allow someone into a
- * specific node without allowing it in the parents. If it's going to
- * fail, however, we don't want the errno to indicate any information
- * about the node. */
-static int check_with_parents(struct connection *conn, const char *node,
- int errnum)
+/* What do parents say? */
+static enum xs_perm_type ask_parents(struct connection *conn,
+ const char *node)
{
struct xs_permissions *perms;
unsigned int num;
-
- /* We always tell them about memory failures. */
- if (errnum == ENOMEM)
- return errnum;
do {
node = get_parent(node);
@@ -741,10 +734,23 @@
if (!perms)
corrupt(conn, "No permissions file at root");
- if (!(perm_for_id(conn->id, perms, num) & XS_PERM_READ))
- return EACCES;
-
- return errnum;
+ return perm_for_id(conn->id, perms, num);
+}
+
+/* We have a weird permissions system. You can allow someone into a
+ * specific node without allowing it in the parents. If it's going to
+ * fail, however, we don't want the errno to indicate any information
+ * about the node. */
+static int errno_from_parents(struct connection *conn, const char *node,
+ int errnum)
+{
+ /* We always tell them about memory failures. */
+ if (errnum == ENOMEM)
+ return errnum;
+
+ if (ask_parents(conn, node) & XS_PERM_READ)
+ return errnum;
+ return EACCES;
}
char *canonicalize(struct connection *conn, const char *node)
@@ -776,24 +782,26 @@
}
perms = get_perms(conn->transaction, node, &num);
- /* No permissions. If we want to create it and
- * it doesn't exist, check parent directory. */
- if (!perms && errno == ENOENT && (perm & XS_PERM_CREATE)) {
- char *parent = get_parent(node);
- if (!parent)
- return false;
-
- perms = get_perms(conn->transaction, parent, &num);
- }
- if (!perms) {
- errno = check_with_parents(conn, node, errno);
+
+ if (perms) {
+ if (perm_for_id(conn->id, perms, num) & perm)
+ return true;
+ errno = EACCES;
return false;
}
- if (perm_for_id(conn->id, perms, num) & perm)
- return true;
-
- errno = check_with_parents(conn, node, EACCES);
+ /* If it's OK not to exist, we consult parents. */
+ if (errno == ENOENT && (perm & XS_PERM_ENOENT_OK)) {
+ if (ask_parents(conn, node) & perm)
+ return true;
+ /* Parents say they should not know. */
+ errno = EACCES;
+ return false;
+ }
+
+ /* They might not have permission to even *see* this node, in
+ * which case we return EACCES even if it's ENOENT or EIO. */
+ errno = errno_from_parents(conn, node, errno);
return false;
}
@@ -930,9 +938,9 @@
if (streq(vec[1], XS_WRITE_NONE))
mode = XS_PERM_WRITE;
else if (streq(vec[1], XS_WRITE_CREATE))
- mode = XS_PERM_WRITE|XS_PERM_CREATE;
+ mode = XS_PERM_WRITE|XS_PERM_ENOENT_OK;
else if (streq(vec[1], XS_WRITE_CREATE_EXCL))
- mode = XS_PERM_WRITE|XS_PERM_CREATE;
+ mode = XS_PERM_WRITE|XS_PERM_ENOENT_OK;
else {
send_error(conn, EINVAL);
return;
@@ -951,7 +959,7 @@
}
/* Not going to create it? */
- if (!(mode & XS_PERM_CREATE)) {
+ if (streq(vec[1], XS_WRITE_NONE)) {
send_error(conn, ENOENT);
return;
}
@@ -985,7 +993,7 @@
static void do_mkdir(struct connection *conn, const char *node)
{
node = canonicalize(conn, node);
- if (!check_node_perms(conn, node, XS_PERM_WRITE|XS_PERM_CREATE)) {
+ if (!check_node_perms(conn, node, XS_PERM_WRITE|XS_PERM_ENOENT_OK)) {
send_error(conn, errno);
return;
}
diff -r a05338d886d9 -r 5eead9930294 tools/xenstore/xenstored_watch.c
--- a/tools/xenstore/xenstored_watch.c Tue Aug 2 18:04:00 2005
+++ b/tools/xenstore/xenstored_watch.c Tue Aug 2 18:04:28 2005
@@ -95,9 +95,18 @@
return 0;
}
-static void add_event(struct watch *watch, const char *node)
+static void add_event(struct connection *conn,
+ struct watch *watch, const char *node)
{
struct watch_event *event;
+
+ /* Check read permission: no permission, no watch event.
+ * If it doesn't exist, we need permission to read parent.
+ */
+ if (!check_node_perms(conn, node, XS_PERM_READ|XS_PERM_ENOENT_OK)) {
+ fprintf(stderr, "No permission for %s\n", node);
+ return;
+ }
if (watch->relative_path) {
node += strlen(watch->relative_path);
@@ -132,9 +141,9 @@
list_for_each_entry(watch, &i->watches, list) {
if (is_child(node, watch->node))
- add_event(watch, node);
+ add_event(i, watch, node);
else if (recurse && is_child(watch->node, node))
- add_event(watch, watch->node);
+ add_event(i, watch, watch->node);
else
continue;
/* If connection not doing anything, queue this. */
@@ -206,7 +215,7 @@
relative = !strstarts(vec[0], "/");
vec[0] = canonicalize(conn, vec[0]);
- if (!check_node_perms(conn, vec[0], XS_PERM_READ)) {
+ if (!is_valid_nodename(vec[0])) {
send_error(conn, errno);
return;
}
diff -r a05338d886d9 -r 5eead9930294 tools/xenstore/xs_lib.h
--- a/tools/xenstore/xs_lib.h Tue Aug 2 18:04:00 2005
+++ b/tools/xenstore/xs_lib.h Tue Aug 2 18:04:28 2005
@@ -30,7 +30,7 @@
XS_PERM_READ = 1,
XS_PERM_WRITE = 2,
/* Internal use. */
- XS_PERM_CREATE = 4,
+ XS_PERM_ENOENT_OK = 4,
XS_PERM_OWNER = 8,
};
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