Guard against bad link destinations.

src/libisofs.h

@@ -819,8 +819,10 @@ const char *iso_symlink_get_dest(const IsoSymlink *link);
  * @param dest
  *     New destination for the link. It must be a non-empty string, otherwise
  *     this function doesn't modify previous destination.
+ * @return
+ *     1 on success, < 0 on error
  */
-void iso_symlink_set_dest(IsoSymlink *link, const char *dest);
+int iso_symlink_set_dest(IsoSymlink *link, const char *dest);
 
 /**
  * Sets the order in which a node will be written on image. High weihted files

src/node.c

@@ -14,6 +14,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <time.h>
+#include <limits.h>
 
 /**
  * Increments the reference counting of the given node.
@@ -541,15 +542,20 @@ const char *iso_symlink_get_dest(const IsoSymlink *link)
 /**
  * Set the destination of a link.
  */
-void iso_symlink_set_dest(IsoSymlink *link, const char *dest)
+int iso_symlink_set_dest(IsoSymlink *link, const char *dest)
 {
-    // TODO guard against bad destinations, such as components bigger than 255
-    if (dest == NULL || dest[0] == '\0') {
+    char *d;
+    if (!iso_node_is_valid_link_dest(dest)) {
         /* guard against null or empty dest */
-        return;
+        return ISO_WRONG_ARG_VALUE;
+    }
+    d = strdup(dest);
+    if (d == NULL) {
+        return ISO_MEM_ERROR;
     }
     free(link->dest);
-    link->dest = strdup(dest);
+    link->dest = d;
+    return ISO_SUCCESS;
 }
 
 /**
@@ -615,6 +621,48 @@ int iso_node_is_valid_name(const char *name)
     return 1;
 }
 
+int iso_node_is_valid_link_dest(const char *dest)
+{
+    int ret;
+    char *ptr, *brk_info, *component;
+
+    /* a dest can't be NULL */
+    if (dest == NULL) {
+        return 0;
+    }
+
+    /* guard against the empty string or big dest... */
+    if (dest[0] == '\0' || strlen(dest) > PATH_MAX) {
+        return 0;
+    }
+    
+    /* check that all components are valid */
+    if (!strcmp(dest, "/")) {
+        /* "/" is a valid component */
+        return 1;
+    }
+    
+    ptr = strdup(dest);
+    if (ptr == NULL) {
+        return 0;
+    }
+    
+    ret = 1;
+    component = strtok_r(ptr, "/", &brk_info);
+    while (component) {
+        if (strcmp(component, ".") && strcmp(component, "..")) {
+            ret = iso_node_is_valid_name(component);
+            if (ret == 0) {
+                break;
+            }
+        }
+        component = strtok_r(NULL, "/", &brk_info);
+    }
+    free(ptr);
+
+    return ret;
+}
+
 int iso_node_new_root(IsoDir **root)
 {
     IsoDir *dir;

src/node.h

@@ -115,4 +115,12 @@ int iso_node_new_root(IsoDir **root);
  */
 int iso_node_is_valid_name(const char *name);
 
+/**
+ * Check if a given path is valid for the destination of a link.
+ * 
+ * @return
+ *     1 if yes, 0 if not
+ */
+int iso_node_is_valid_link_dest(const char *dest);
+
 #endif /*LIBISO_NODE_H_*/

src/tree.c

@@ -150,6 +150,12 @@ int iso_tree_add_new_symlink(IsoDir *parent, const char *name,
     if (!iso_node_is_valid_name(name)) {
         return ISO_WRONG_ARG_VALUE;
     }
+    
+    /* check if destination is valid */
+    if (!iso_node_is_valid_link_dest(dest)) {
+        /* guard against null or empty dest */
+        return ISO_WRONG_ARG_VALUE;
+    }
 
     /* find place where to insert */
     pos = &(parent->children);