Strange rewrite_by_lua outcome

[Nginx User]

On 17 October 2011 03:55, agentzh <agentzh at gmail.com> wrote:
> On Mon, Oct 17, 2011 at 4:11 AM, Nginx User <nginx at nginxuser.net> wrote:
>>
>> This produces a 500 Internal server error instead:
>> #GET /submit_links/
>> rewrite_by_lua '
>>        local request_uri = ngx.re.match(ngx.var.request_uri,
>> "\:|\[|\]|\-\-|\@|\^|\{|\}|\~|\<|\>|\.\.|\+\+|//|\%0|\%A|\%B|\%C|\%D|\%E|\%F|\%22|\%27|\%28|\%29|\%3C|\%3E|\%5C|\%7B|\%7C|\%7D|select(\s*)\(|convert(\s*)\(|/query/|function\.|remoteFile|servername|\&rptmode\=|/\(null\)/|(maincore|authorize|macromates|head_auth|submit_links|change_action|admin_db_utilities|admin\.webring\.docs|Table/Latest/index)\.|w00t|MNG/LIVE|/x[0-9][0-9]|\\x[0-9][0-9]|/(cgi|https?)/|\.css\(|\)\+|/\,/|\{0\}|eval\(|\_vti\_|\(null\)|echo.*kae|function(\.array\-rand|\(\))",
>> "io")
>
> I think you should escape "\" here according to nginx's string literal
> syntax (you do not need to escape "\" in your previous "if" example
> because Nginx uses special regex syntax in that regex context. You'll
> also have to escape the "\" according to Lua string escaping rules
> too. That is, escaping "\" *twice*.
>
>>
>> Line 62: "23388#0: *258 Failed to load Lua inlined code: [string
>> "rewrite_by_lua"]:24: ')' expected near '|', client: xx.xxx.xx.xx,
>> server: testsite.com, request: "GET /submit_links HTTP/1.1", host:
>> "testsite.com""
>> http://pastebin.com/XYNwEciX
>>
>
> The error message indicates a Lua syntax error in your Lua source
> code. A quick solution to this is to put your code into a separate
> .lua file and use rewrite_by_lua_file instead such that you do not
> have to escape "\" twice (once for Nginx string escaping rules and
> another for Lua string escaping rules).
>
> Here's an example:
>    # nginx.conf
>    location /foo {
>        rewrite_by_lua 'ngx.re.match("\\\\d+", ngx.var.uri)';  # we're
> using \d+ here but requires twice escaping
>    }
>
> And to use external .lua file:
>
>    # nginx.conf
>    location /foo {
>        rewrite_by_lua_file conf/my.lua;
>    }
>
>    # conf/my.lua
>    ngx.re.match("\\d+", ngx.var.uri)
>
> We can see that in the first example, we need to escape "\" for Nginx
> string literals (so it becomes "\\") and then escape each of these two
> back-slashes again according for Lua string literals and thus got
> "\\\\" at last.
>
> But in the second example, we only need to esacpe "\" once according
> to Lua string literal syntax, which is a bit better looking :)
>
> This gotcha is documented in ngx_lua's wiki page here:
>
>    http://wiki.nginx.org/HttpLuaModule#ngx.re.match

I'll use the rewrite module for this regex since it works as is and
try to understand the issue later.

Thanks.