Redirect to 404 if filename passed as parameter does not exitsts

Question

I have special parameter data=/path/to/filename.htm in uri.

Its old and rusty site builded on SSI, and I can't modify it.

Problem is when filename passed as arg_data not exists, page is broken.

I want redirect to 404.htm in this case.

Something like that:

if (!-f $arg_data){
     rewrite ^.*$  /404.htm last;
   }

But I get:

rewrite or internal redirection cycle while processing "/404.htm

I think its because I didn't check if arg_data exists.

But nginx have not nested if-s.

I tried:

set $data index.htm;                                                                                                                                               
if ($args ~ "data=(.+)") {                                                                                                                                         
    set $data $1;                                                                                                                                                  
}                                                                                                                                                                                                                                                                                                                                          
if (!-f $data) {                                                                                                                                                
    rewrite ^.*$  /404.htm last;                                                                                                                                   
}

Idea was set $data to some file which 100% exists, and after that rewrite if data param is passed.

For some reason its give the same error, internal redirection cycle

Looks like I do it in wrong way.

You need to be using `try_files`. This is not Apache where you have to rewrite everything. — Michael Hampton, Feb 23 '14 at 13:49
I have "inversed logic". 404 if $data NOT exists, what to try? — Korjavin Ivan, Feb 23 '14 at 17:04
Inverse of what? That is a perfectly normal circumstance. Show your entire `server` block so that we can figure out what you are trying to do. — Michael Hampton, Feb 23 '14 at 17:05
Aha, ok. My example. Uri is: /detail.htm?data=product.htm. I must show the detail.htm if exists product.htm, and 404.htm otherwise. — Korjavin Ivan, Feb 23 '14 at 17:52

score 3 · Answer 1 · answered Feb 23 '14 at 18:33

3

OK, this is a very strange scenario, and you seem to be on the right track.

Instead of the rewrite, though, I would return 404; and use an error_page to define the 404 error page.

For example:

server {

    #...your other stuff...

    error_page 404 /404.htm;

    if (!-f $arg_data){
        return 404;
    }
}

answered Feb 23 '14 at 18:33

Michael Hampton

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Entire config : https://gist.github.com/korjavin/9181939 Its still show index.htm even if aaa.htm not exists in uri index.htm?data=aaa.htm – Korjavin Ivan Feb 24 '14 at 04:26
1

@Korjavin Ivan Try with `if (!-f /full/path/to/$arg_data)` – krisFR Feb 24 '14 at 15:42
Oh, yes, much closer. But big problem if this $arg_data not passed to uri. I also need to do that ONLY if $arg_data exists. Nested if again. – Korjavin Ivan Feb 24 '14 at 15:45
@Korjavin Ivan Ok, i've written an answer to deal with this problem – krisFR Feb 24 '14 at 19:26

krisFR · Accepted Answer · 2014-02-25T00:36:49.787

2

Ok, so regarding the last comments we had, you need an AND condition for two if statements.

NGinx is not able to do this.

To achieve this, we will use a little trick dealing with a $test var :

server {

  #...directives...

  error_page 404 /404.htm;

  if ($args != "") {                  # Test if there are some args       
     set $test A;
  }

  if (!-f /full/path/to/$arg_data) {  # Test if file in args doesn't exist
     set $test "${test}B";
  }

  if ($test = AB) {       # If there are some args AND if file doesn't exist
     return 404;
  }

}

edited Feb 25 '14 at 00:36

answered Feb 24 '14 at 19:24

krisFR

13,280
4
36
42

Thank you! Its new trick for me. I saw it in bash, but forget – Korjavin Ivan Feb 25 '14 at 03:27
1

You know what man ? i've worked 2 days (not full time) on your issue ! – krisFR Feb 25 '14 at 03:28
Wow!! I hope you have some fun with it. – Korjavin Ivan Feb 25 '14 at 03:29
Of course i had ! If not, i won't do this ;) – krisFR Feb 25 '14 at 03:47

Redirect to 404 if filename passed as parameter does not exitsts

2 Answers2