[Add] Enforce file permissions.

common/src/lua_api.cpp

@@ -27,6 +27,11 @@ std::string rm(Session& context, const std::string& filename) {
     return "rm: cannot remove '" + filename + "': Is a directory.";
   }
 
+  vfs_node* parent_dir = it->second->parent;
+  if(parent_dir && !has_permission(parent_dir, context, WRITE_PERM)) {
+    return "rm: cannot remove '" + filename + "': Permission denied";
+  }
+
   delete it->second; /* Free the memory for the node. */
   current_dir->children.erase(it); /* Remove from map. */
   return "";
@@ -65,6 +70,10 @@ std::string write_file(Session& context, const std::string& path,
     return "write: cannot create file in '" + get_full_path(parent_dir) + "': Not a directory";
   }
 
+  if(!has_permission(parent_dir, context, WRITE_PERM)) {
+    return "write: cannot create file '" + path + "': Permission denied";
+  }
+
   auto it = parent_dir->children.find(filename);
   if(it != parent_dir->children.end()) {
     if(it->second->type == DIR_NODE) {
@@ -114,6 +123,10 @@ std::string create_executable(Session& context, const std::string& path,
         + "': Not a directory";
   }
 
+  if(!has_permission(parent_dir, context, WRITE_PERM)) {
+    return "create_executable: cannot create file '" + path + "': Permission denied";
+  }
+
   /* Overwrite if exists. */
   auto it = parent_dir->children.find(filename);
   if(it != parent_dir->children.end()) {
@@ -129,6 +142,10 @@ std::string create_executable(Session& context, const std::string& path,
 }
 
 std::string read_file(Session& context, const std::string& path) {
+  vfs_node* node = find_node_by_path(context.get_session_machine()->vfs_root, path);
+  if(node && !has_permission(node, context, READ_PERM)) {
+    return "cat: " + path + ": Permission denied";
+  }
   return context.read_file(path);
 }
 
@@ -142,6 +159,9 @@ std::string cd(Session& context, const std::string& path) {
   } else {
     auto it = current_dir->children.find(path);
     if(it != current_dir->children.end() && it->second->type == DIR_NODE) {
+      if(!has_permission(it->second, context, EXEC_PERM)) {
+        return "cd: " + path + ": Permission denied";
+      }
       context.set_current_dir(it->second);
     } else {
       return "cd: no such file or directory: " + path;

common/src/session.cpp

@@ -70,6 +70,14 @@ void Session::set_session_machine(Machine* machine) {
   }
 }
 
+uint32_t Session::get_current_uid(void) {
+  return _home_machine->owner_id;
+}
+
+uint32_t Session::get_current_gid(void) {
+  return _home_machine->owner_id;
+}
+
 std::string Session::process_command(const std::string& command) {
   /*
    * Creating the Lua processor on-demand to ensure it exists on the same
@@ -113,6 +121,9 @@ std::string Session::process_command(const std::string& command) {
 
   if(command_node) {
     if(command_node->type == EXEC_NODE) {
+      if(!has_permission(command_node, *this, EXEC_PERM)) {
+        return "Cannot execute '" + command_name + "': Permission denied.";
+      }
       bool is_remote = (_session_machine != _home_machine);
       std::string deobfuscated_content = util::xor_string(command_node->content);
       sol::object result = lua.execute(deobfuscated_content, *this, args, is_remote);

common/src/session.h

@@ -29,6 +29,9 @@ public:
   MachineManager* get_machine_manager(void);
   INetworkBridge* get_network_bridge(void);
 
+  uint32_t get_current_uid(void);
+  uint32_t get_current_gid(void);
+ 
   void set_current_dir(vfs_node* node);
   void set_session_machine(Machine* machine);
 

common/src/vfs.cpp

@@ -1,6 +1,30 @@
 #include <sstream>
 
 #include "vfs.h"
+#include "session.h"
+
+bool has_permission(vfs_node* node, Session& context, uint8_t required_perm) {
+  uint32_t uid = context.get_current_uid();
+  if(uid == 0) { /* Root user. */
+    return true;
+  }
+
+  uint32_t gid    = context.get_current_gid();
+  uint16_t perms  = node->permissions;
+
+  if(node->owner_id == uid) {
+    /* Check owner permissions. */
+    return ((perms >> 6) & required_perm) == required_perm;
+  } else if(node->group_id == gid) {
+    /* Check group permissions. */
+    return ((perms >> 3) & required_perm) == required_perm;
+  } else {
+    /* Check other permissions. */
+    return (perms & required_perm) == required_perm;
+  }
+
+  return false;
+}
 
 /* Create a new node. */
 vfs_node* new_node(std::string name, vfs_node_type type, vfs_node* parent,

common/src/vfs.h

@@ -4,6 +4,7 @@
 #include <string>
 #include <map>
 
+class Session;
 struct vfs_node;
 
 /* Store children for quick lookup by name. */
@@ -33,6 +34,11 @@ struct vfs_node {
   vfs_node* parent;
 };
 
+const uint8_t READ_PERM   = 4;
+const uint8_t WRITE_PERM  = 2;
+const uint8_t EXEC_PERM   = 1;
+
+bool has_permission(vfs_node* node, Session& context, uint8_t required_perm);
 vfs_node* new_node(std::string name, vfs_node_type type, vfs_node* parent,
                    uint32_t owner_id = 0, uint32_t group_id = 0, uint16_t permissions=0755);
 vfs_node* find_node_by_id(vfs_node* root, long long id);