tools/xenstore: merge get_spec_node() into get_node_canonicalized()

Add a "allow_special" parameter to get_node_canonicalized() allowing
to merge get_spec_node() into get_node_canonicalized().

Add the same parameter to is_valid_nodename(), as this will simplify
check_watch_path().

This is done in preparation to introducing a get_node() variant
returning a pointer to const struct node.

Note that this will change how special node names are going to be
validated, as now the normal restrictions for node names will be
applied:

- they can't end with "/"
- they can't contain "//"
- they can't contain characters other than the ones allowed for normal
  nodes
- the length of the node name is restricted by the max path length
  quota

For defined special node names this isn't any real restriction, though.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>

tools/xenstore/xenstored_core.c

@@ -1219,13 +1219,14 @@ static bool valid_chars(const char *node)
 		       "0123456789-/_@") == strlen(node));
 }
 
-bool is_valid_nodename(const struct connection *conn, const char *node)
+bool is_valid_nodename(const struct connection *conn, const char *node,
+		       bool allow_special)
 {
 	int local_off = 0;
 	unsigned int domid;
 
-	/* Must start in /. */
-	if (!strstarts(node, "/"))
+	/* Must start in / or - if special nodes are allowed - in @. */
+	if (!strstarts(node, "/") && (!allow_special || !strstarts(node, "@")))
 		return false;
 
 	/* Cannot end in / (unless it's just "/"). */
@@ -1293,7 +1294,8 @@ static struct node *get_node_canonicalized(struct connection *conn,
 					   const void *ctx,
 					   const char *name,
 					   const char **canonical_name,
-					   unsigned int perm)
+					   unsigned int perm,
+					   bool allow_special)
 {
 	const char *tmp_name;
 
@@ -1302,33 +1304,20 @@ static struct node *get_node_canonicalized(struct connection *conn,
 	*canonical_name = canonicalize(conn, ctx, name);
 	if (!*canonical_name)
 		return NULL;
-	if (!is_valid_nodename(conn, *canonical_name)) {
+	if (!is_valid_nodename(conn, *canonical_name, allow_special)) {
 		errno = EINVAL;
 		return NULL;
 	}
 	return get_node(conn, ctx, *canonical_name, perm);
 }
 
-static struct node *get_spec_node(struct connection *conn, const void *ctx,
-				  const char *name, const char **canonical_name,
-				  unsigned int perm)
-{
-	if (name[0] == '@') {
-		if (canonical_name)
-			*canonical_name = name;
-		return get_node(conn, ctx, name, perm);
-	}
-
-	return get_node_canonicalized(conn, ctx, name, canonical_name, perm);
-}
-
 static int send_directory(const void *ctx, struct connection *conn,
 			  struct buffered_data *in)
 {
 	struct node *node;
 
 	node = get_node_canonicalized(conn, ctx, onearg(in), NULL,
-				      XS_PERM_READ);
+				      XS_PERM_READ, false);
 	if (!node)
 		return errno;
 
@@ -1350,7 +1339,7 @@ static int send_directory_part(const void *ctx, struct connection *conn,
 
 	/* First arg is node name. */
 	node = get_node_canonicalized(conn, ctx, in->buffer, NULL,
-				      XS_PERM_READ);
+				      XS_PERM_READ, false);
 	if (!node)
 		return errno;
 
@@ -1400,7 +1389,7 @@ static int do_read(const void *ctx, struct connection *conn,
 	struct node *node;
 
 	node = get_node_canonicalized(conn, ctx, onearg(in), NULL,
-				      XS_PERM_READ);
+				      XS_PERM_READ, false);
 	if (!node)
 		return errno;
 
@@ -1614,7 +1603,8 @@ static int do_write(const void *ctx, struct connection *conn,
 	offset = strlen(vec[0]) + 1;
 	datalen = in->used - offset;
 
-	node = get_node_canonicalized(conn, ctx, vec[0], &name, XS_PERM_WRITE);
+	node = get_node_canonicalized(conn, ctx, vec[0], &name, XS_PERM_WRITE,
+				      false);
 	if (!node) {
 		/* No permissions, invalid input? */
 		if (errno != ENOENT)
@@ -1643,7 +1633,7 @@ static int do_mkdir(const void *ctx, struct connection *conn,
 	const char *name;
 
 	node = get_node_canonicalized(conn, ctx, onearg(in), &name,
-				      XS_PERM_WRITE);
+				      XS_PERM_WRITE, false);
 
 	/* If it already exists, fine. */
 	if (!node) {
@@ -1773,7 +1763,7 @@ static int do_rm(const void *ctx, struct connection *conn,
 	char *parentname;
 
 	node = get_node_canonicalized(conn, ctx, onearg(in), &name,
-				      XS_PERM_WRITE);
+				      XS_PERM_WRITE, false);
 	if (!node) {
 		/* Didn't exist already?  Fine, if parent exists. */
 		if (errno == ENOENT) {
@@ -1814,7 +1804,8 @@ static int do_get_perms(const void *ctx, struct connection *conn,
 	char *strings;
 	unsigned int len;
 
-	node = get_spec_node(conn, ctx, onearg(in), NULL, XS_PERM_READ);
+	node = get_node_canonicalized(conn, ctx, onearg(in), NULL, XS_PERM_READ,
+				      true);
 	if (!node)
 		return errno;
 
@@ -1857,8 +1848,8 @@ static int do_set_perms(const void *ctx, struct connection *conn,
 		return ENOENT;
 
 	/* We must own node to do this (tools can do this too). */
-	node = get_spec_node(conn, ctx, in->buffer, &name,
-			     XS_PERM_WRITE | XS_PERM_OWNER);
+	node = get_node_canonicalized(conn, ctx, in->buffer, &name,
+				      XS_PERM_WRITE | XS_PERM_OWNER, true);
 	if (!node)
 		return errno;
 

tools/xenstore/xenstored_core.h

@@ -305,7 +305,8 @@ void check_store(void);
 void corrupt(struct connection *conn, const char *fmt, ...);
 
 /* Is this a valid node name? */
-bool is_valid_nodename(const struct connection *conn, const char *node);
+bool is_valid_nodename(const struct connection *conn, const char *node,
+		       bool allow_special);
 
 /* Get name of parent node. */
 char *get_parent(const void *ctx, const char *node);

tools/xenstore/xenstored_watch.c

@@ -163,19 +163,12 @@ static int destroy_watch(void *_watch)
 static int check_watch_path(struct connection *conn, const void *ctx,
 			    const char **path, bool *relative)
 {
-	/* Check if valid event. */
-	if (strstarts(*path, "@")) {
-		*relative = false;
-		if (strlen(*path) > XENSTORE_REL_PATH_MAX)
-			goto inval;
-	} else {
-		*relative = !strstarts(*path, "/");
-		*path = canonicalize(conn, ctx, *path);
-		if (!*path)
-			return errno;
-		if (!is_valid_nodename(conn, *path))
-			goto inval;
-	}
+	*relative = !strstarts(*path, "/") && !strstarts(*path, "@");
+	*path = canonicalize(conn, ctx, *path);
+	if (!*path)
+		return errno;
+	if (!is_valid_nodename(conn, *path, true))
+		goto inval;
 
 	return 0;