SSI include infinite loop

Server NGINX
1

Hello,

I’ve encountered a problem about “SSI include infinite loop”.

We have a system that our editors can compose a html page from some
templates using SSI. Sometimes unwarily combination will cause infinite
loop, such as ‘A include A’, ‘A include B, B include A’, or even ‘A
include
B, B include C, C include A’. And this page will cause nginx eating up
all
memories, and certainly won’t serve any more unless we restart nginx.

I’m wondering is there any solution for this problem? Or other ways to
avoid
this?

I’ve googled apache and lighttpd, and there also no official solution
for
this, unless lightptd has a patch which will limit the whole ‘include’
count, and I think it’s just a tricky way to fix the infinite loop.

Thanks a lot for any help!

2

Hello!

On Tue, May 24, 2011 at 10:49:45AM +0800, eagle sbc wrote:

I’m wondering is there any solution for this problem? Or other ways to avoid
this?

I’ve googled apache and lighttpd, and there also no official solution for
this, unless lightptd has a patch which will limit the whole ‘include’
count, and I think it’s just a tricky way to fix the infinite loop.

Thanks a lot for any help!

Number of in-flight ssi includes used to be limited in nginx,
though this limit was broken somewhere near 0.7.25.

This patch brings it back:

http://nginx.org/pipermail/nginx-devel/2011-February/000746.html

Maxim D.

3

Hello,

Thanks for your reply! And I think the limit on the number is proper for
most of the conditions.

However in our case, the index page may have hundreds of SSI ‘include’
(combined from lots of our sub sites), and the number limitation may not
be
so proper.

So here I made a patch: For every ‘include’, a ‘parents uri check’ is
made.
The patch is like this:

diff -crB
nginx-0.7.65.org/src/http/modules/ngx_http_ssi_filter_module.cnginx-0.7.65.patch/src/http/modules/ngx_http_ssi_filter_module.c
*** nginx-0.7.65.org/src/http/modules/ngx_http_ssi_filter_module.c
2011-05-24 18:46:53.676370002 +0800
— nginx-0.7.65.patch/src/http/modules/ngx_http_ssi_filter_module.c
2011-05-25 11:19:20.372370002 +0800

*** 2024,2029 ****
— 2024,2044 ----
flags |=
NGX_HTTP_SUBREQUEST_IN_MEMORY|NGX_HTTP_SUBREQUEST_WAITED;
}

  • ngx_http_request_t *ir = r;

  • for(;ir != NULL;ir = ir->parent) {

  •     ngx_log_debug4(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,

  •                    " include path: %V, args: %V; parent path: %V,

args: %V",

  •                    uri, &args, &ir->uri, &ir->args);

  •     if (uri->len == ir->uri.len

  •         && args.len == ir->args.len

  •         && ngx_strncmp(uri->data, ir->uri.data, uri->len) == 0

  •         && ngx_strncmp(args.data, ir->args.data, args.len) == 0) {

  •         ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,

  •                       "A loop include \"%V\" is found", uri);

  •         return NGX_HTTP_SSI_ERROR;

  •     }

  • }

  • if (ngx_http_subrequest(r, uri, &args, &sr, psr, flags) != NGX_OK)

{
return NGX_HTTP_SSI_ERROR;
}

Hope for any reply of my patch !

And thanks to my fellow Ҧΰ for reminding me on the ‘args’ check!