From: Tobias Ulmer <tu@emlix.com>
Date: Tue, 25 Feb 2014 13:18:39 +0000 (+0100)
Subject: Don't pass main string package into protected environment
X-Git-Tag: e2factory-2.3.15rc1~214
X-Git-Url: https://git.e2factory.org/?a=commitdiff_plain;h=118cd203b1026df1ccda4913ad6f18eef924914d;p=e2factory.git

Don't pass main string package into protected environment

The string package can easily be manipulated or variable passed around
in it. Supply each protected environment with its own copy of the
table and only add functions that are considered safe.
---

diff --git a/generic/e2lib.lua b/generic/e2lib.lua
index 9ea320f..126ea8e 100644
--- a/generic/e2lib.lua
+++ b/generic/e2lib.lua
@@ -1484,6 +1484,28 @@ function e2lib.callcmd_log(cmd, workdir, envdict)
     return rc, e
 end
 
+--- Generate a new table populated with all the safe Lua "string" functions.
+-- The intended use is to generate a now string table for each protected
+-- environment, so that no information can be passed through string, or worse,
+-- real string functions can be overwritten and thus escape the protected env.
+-- @return New "string" replacement package.
+function e2lib.safe_string_table()
+    local safefn = {
+        "byte", "char", "find", "format", "gmatch", "gsub", "len", "lower",
+        "match", "rep", "reverse", "sub", "upper"
+    }
+    -- unsafe: dump
+
+    local st = {}
+
+    for _,name in ipairs(safefn) do
+        assert(string[name])
+        st[name] = string[name]
+    end
+
+    return st
+end
+
 --- Executes Lua code loaded from path.
 --@param path Filename to load lua code from (string).
 --@param gtable Environment (table) that is used instead of the global _G.
diff --git a/local/chroot.lua b/local/chroot.lua
index b123ac1..3b8b9c9 100644
--- a/local/chroot.lua
+++ b/local/chroot.lua
@@ -174,12 +174,13 @@ function chroot.load_chroot_config(info)
     e = err.new("loading chroot config %q failed", path)
 
     t = nil
-    local function assign(table)
-        t = table
-    end
+    local g = {
+        e2chroot = function (data) t = data end,
+        env = info.env,
+        string = e2lib.safe_string_table(),
+    }
 
-    rc, re = e2lib.dofile2(path,
-        { e2chroot = assign, env = info.env, string = string })
+    rc, re = e2lib.dofile2(path, g)
     if not rc then
         return false, re
     end
diff --git a/local/e2tool.lua b/local/e2tool.lua
index 5c4ab2c..ffebb7e 100644
--- a/local/e2tool.lua
+++ b/local/e2tool.lua
@@ -169,7 +169,13 @@ local function load_user_config(info, path, dest, index, var)
         dest[index] = table
     end
 
-    rc, re = e2lib.dofile2(path, { [var] = func, env = info.env, string=string })
+    local g = {
+        [var] = func,
+        env = info.env,
+        string = e2lib.safe_string_table(),
+    }
+
+    rc, re = e2lib.dofile2(path, g)
     if not rc then
         return false, e:cat(re)
     end
@@ -216,11 +222,15 @@ local function load_user_config2(info, path, types)
         table.insert(list, t)
     end
 
-    local g = {}			-- compose the environment for the config file
-    g.env = info.env			-- env
-    g.string = string			-- string
+    -- compose the environment for the config file
+    local g = {
+        env = info.env,
+        string = e2lib.safe_string_table(),
+    }
+
+    -- and some config functions
     for _,typ in ipairs(types) do
-        g[typ] = f[typ]			-- and some config functions
+        g[typ] = f[typ]
     end
 
     rc, re = e2lib.dofile2(path, g)
@@ -574,8 +584,8 @@ local function load_env_config(info, file)
     local path = e2lib.join(info.root, file)
     local g = {
         e2env = info.env,
-        string = string,
         env = mergeenv,
+        string = e2lib.safe_string_table(),
     }
     rc, re = e2lib.dofile2(path, g)
     if not rc then
diff --git a/local/licence.lua b/local/licence.lua
index c3faabc..09aab3c 100644
--- a/local/licence.lua
+++ b/local/licence.lua
@@ -158,19 +158,22 @@ function licence.load_licence_config(info)
     e2lib.logf(3, "loading licence config %q", path)
     e = err.new("loading licence config %q failed", path)
 
-    ltable = {}
-    local function assign(table)
-        for k,v in pairs(table) do
-            ltable[k] = v
-        end
-    end
+    ltable = nil
+    local g = {
+        e2licence = function(data) ltable = data end,
+        env = info.env,
+        string = e2lib.safe_string_table(),
+    }
 
-    rc, re = e2lib.dofile2(path,
-        { e2licence = assign, env = info.env, string = string })
+    rc, re = e2lib.dofile2(path, g)
     if not rc then
         return false, re
     end
 
+    if type(ltable) ~= "table" then
+        return false, e:append("empty or invalid licence configuration")
+    end
+
     for k,v in pairs(ltable) do
         if type(k) ~= "string" then
             return false, e:append("key %q is not a string", tostring(k))