fix: support symlink attribute checking on RewriteCond

Addresses e404#24

Author: rkaiser0324

Dockerfile

@@ -2,6 +2,25 @@
 
 FROM fabiocicerchia/nginx-lua:1.23.2-almalinux8.7-20221201
 
+# The luajit package expects Lua 5.1, but this container has 5.3 so remove that.  
+# Then build Lua 5.1 and luarocks from source so you can install the luafilesystem module
+RUN dnf remove -y lua \
+    && dnf install -y cmake luajit readline-devel \
+    && cd /tmp \
+        && curl https://www.lua.org/ftp/lua-5.1.5.tar.gz -L -o lua-5.1.5.tar.gz \
+        && tar -zxvf lua-5.1.5.tar.gz \
+        && cd lua-5.1.5 \
+            && CFLAGS=-DLUA_USE_LINUX make linux \
+            && make install \
+            && cd .. \
+        && curl https://luarocks.org/releases/luarocks-3.8.0.tar.gz -L -o luarocks-3.8.0.tar.gz \
+        && tar -zxvf luarocks-3.8.0.tar.gz \
+        && cd luarocks-3.8.0 \
+            && ./configure --with-lua-include=/usr/local/include \
+            && make install \
+            && cd .. \
+    && luarocks install luafilesystem
+    
 # Build the EmmyLuaDebugger from source for debugging Lua via IntelliJ IDEA
 RUN curl https://github.com/EmmyLua/EmmyLuaDebugger/archive/refs/tags/1.0.16.tar.gz \
          -L -o EmmyLuaDebugger-1.0.16.tar.gz && \

README.md

@@ -65,10 +65,10 @@ When you request a URL that triggers the Lua script, it will pause on the `dbg.b
 
 ### Manual installation
 
-1. Install nginx with the [Lua module](https://github.com/openresty/lua-nginx-module) `libnginx-mod-http-lua` and the `luajit` package.
-    1. Debian: `apt-get install nginx libnginx-mod-http-lua luajit`
-    2. Fedora: `yum install nginx libnginx-mod-http-lua luajit`
-    
+1. Install nginx with the [Lua module](https://github.com/openresty/lua-nginx-module) `libnginx-mod-http-lua` and the `luajit` and `luarocks` packages.
+    1. Debian: `apt-get install nginx libnginx-mod-http-lua luajit luarocks`
+    2. Fedora: `dnf install nginx libnginx-mod-http-lua luajit luarocks`
+1. Install the [LuaFileSystem](https://lunarmodules.github.io/luafilesystem/) module via `luarocks install luafilesystem`
 1. Verify that the Lua module is properly installed by running:
     ```bash
     nginx -V 2>&1 | tr ' ' '\n' | grep lua
@@ -266,7 +266,7 @@ mod_negotiation	|	`ForceLanguagePriority`	|	No	|
 mod_negotiation	|	`LanguagePriority`	|	No	|	
 mod_reflector	|	`*`	|	Never	|	Security reasons
 mod_rewrite	|	`RewriteBase`	|	Yes	|	
-mod_rewrite	|	`RewriteCond`	|	Partial	|	Environment (E=) flag is unsupported, as are *CondPattern* integer comparisons and some file attribute tests listed in the [documentation](https://httpd.apache.org/docs/2.4/mod/mod_rewrite.html)
+mod_rewrite	|	`RewriteCond`	|	Partial	|	Environment (E=) flag is unsupported, as are *CondPattern* integer comparisons and some file attribute tests listed in the [documentation](https://httpd.apache.org/docs/2.4/mod/mod_rewrite.html).
 mod_rewrite	|	`RewriteEngine`	|	Yes	|	
 mod_rewrite	|	`RewriteOptions`	|	No	|	
 mod_rewrite	|	`RewriteRule`	|	Yes	|	

htaccess.lua

@@ -150,6 +150,27 @@ local path_exists = function(filepath, soft_fail)
 	return ok
 end
 
+-- Get the type of a file system object
+-- @param filepath .... the filename
+-- @return file_type .. One of (directory|link|file), or nil if the path is invalid
+local get_file_type = function(filepath)
+	local lfs = require "lfs"
+	local file_type = nil
+	if (lfs.symlinkattributes (filepath) ~= nil) then
+		local attr = lfs.symlinkattributes (filepath);
+		assert (type(attr) == "table")
+		if attr.mode == "directory" then
+			file_type = 'directory'
+		elseif attr['target'] ~= nil then
+			-- print ("*** symlink found   "..attr['target'])
+			file_type = 'link'
+		else
+			file_type = 'file'
+		end
+	end
+	return file_type
+end
+
 -- Read contents of any file
 local get_file_contents = function(name)
 	ensure_doc_root(name) -- Security: enforce document root
@@ -1101,10 +1122,16 @@ if get_cdir('rewrite') and #parsed_rewriterules > 0 then
 					fail('RewriteCond expressions ("expr ...") are unsupported') -- We don't support expr style conditions due to their weird complexity and redundancy
 				elseif cond_pattern:sub(1,1) == '-' then -- File attribute tests or integer comparisons (case sensitive)
 					local filepath = cond_test:gsub('/$','',1)
+					local file_type = get_file_type(filepath)
+
+					cond_matches = false
+
 					if cond_pattern == '-d' then -- is directory
-						cond_matches = path_exists(filepath..'/')
+						cond_matches = file_type == 'directory'
 					elseif cond_pattern == '-f' or cond_pattern == '-F' then -- is file
-						cond_matches = path_exists(filepath) and not path_exists(filepath..'/')
+						cond_matches = file_type == 'file'
+					elseif cond_pattern == '-l' or cond_pattern == '-L' then -- is symlink
+						cond_matches = file_type == 'link'
 					else
 						fail('RewriteCond pattern unsupported: '..cond_pattern)
 					end