Opened 2 years ago

Last modified 2 years ago

#1383 accepted defect

Error if using proxy_pass with variable and limit_except

Reported by: Haxe18@… Owned by:
Priority: minor Milestone:
Component: nginx-core Version: 1.12.x
Keywords: Cc:
uname -a: Linux test 3.16.0-4-amd64 #1 SMP Debian 3.16.43-2+deb8u3 (2017-08-15) x86_64 GNU/Linux
nginx -V: nginx version: nginx/1.12.1 built by gcc 4.9.2 (Debian 4.9.2-10) built with OpenSSL 1.0.1t 3 May 2016 TLS SNI support enabled configure arguments: --prefix=/etc/nginx --sbin-path=/usr/sbin/nginx --modules-path=/usr/lib/nginx/modules --conf-path=/etc/nginx/nginx.conf --error-log-path=/var/log/nginx/error.log --http-log-path=/var/log/nginx/access.log --pid-path=/var/run/nginx.pid --lock-path=/var/run/nginx.lock --http-client-body-temp-path=/var/cache/nginx/client_temp --http-proxy-temp-path=/var/cache/nginx/proxy_temp --http-fastcgi-temp-path=/var/cache/nginx/fastcgi_temp --http-uwsgi-temp-path=/var/cache/nginx/uwsgi_temp --http-scgi-temp-path=/var/cache/nginx/scgi_temp --user=nginx --group=nginx --with-compat --with-file-aio --with-threads --with-http_addition_module --with-http_auth_request_module --with-http_dav_module --with-http_flv_module --with-http_gunzip_module --with-http_gzip_static_module --with-http_mp4_module --with-http_random_index_module --with-http_realip_module --with-http_secure_link_module --with-http_slice_module --with-http_ssl_module --with-http_stub_status_module --with-http_sub_module --with-http_v2_module --with-mail --with-mail_ssl_module --with-stream --with-stream_realip_module --with-stream_ssl_module --with-stream_ssl_preread_module --with-cc-opt='-g -O2 -fstack-protector-strong -Wformat -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fPIC' --with-ld-opt='-Wl,-z,relro -Wl,-z,now -Wl,--as-needed -pie'

Description

Hi nginx guys,

i use a nginx in front of a varnish server.
I purge my varnish via purge method.

Nginx uses the following VHost config:

server {
    listen       *:80 default_server;

    location / {
        limit_except GET POST {
            allow 127.0.0.1/32;
            deny all;
        }

        set $upstream http://127.0.0.1:8080;

        if ($http_user_agent = 'mobile') {
            set $upstream http://127.0.0.1:8080;
        }

        proxy_pass              $upstream;
        proxy_set_header        Host $host;
        proxy_set_header        X-Forwarded-For $remote_addr;
    }
}

Suggested: From not localhost i only can request GET/HEAD/POST, localhost can do everything.

From remote it works as expected:

root@test:~# curl -X PURGE -I EXTIP
HTTP/1.1 403 Forbidden
Server: nginx
Date: Mon, 18 Sep 2017 10:39:23 GMT
Content-Type: text/html
Content-Length: 162
Connection: keep-alive
Vary: Accept-Encoding

But from localhost:

root@test:~# curl -X PURGE -I http://127.0.0.1
HTTP/1.1 500 Internal Server Error
Server: nginx
Date: Mon, 18 Sep 2017 10:39:06 GMT
Content-Type: text/html
Content-Length: 186
Connection: close

Nginx error log tells me:

==> /var/log/nginx/error.log <==
2017/09/18 12:39:06 [error] 2483#2483: *2 invalid URL prefix in "", client: 127.0.0.1, server: , request: "PURGE / HTTP/1.1", host: "127.0.0.1"

Without using Variables in VHost:

server {
    listen       *:80 default_server;

    location / {
        limit_except GET POST {
            allow 127.0.0.1/32;
            deny all;
        }

        proxy_pass              http://127.0.0.1:8080;
        proxy_set_header        Host $host;
        proxy_set_header        X-Forwarded-For $remote_addr;
    }
}

Works as expected:

root@test:~# curl -X PURGE -I http://127.0.0.1
HTTP/1.1 200 OK
Server: nginx
Date: Mon, 18 Sep 2017 10:45:35 GMT
Content-Type: text/html; charset=UTF-8
Transfer-Encoding: chunked
Connection: keep-alive
Vary: Accept-Encoding

Other tests with a variable proxy_pass e.g. using the get method instead of purge also fails with same error.

Please take a look why nginx fails when combining limit_except with proxypass and variables.
Thanks

Change History (1)

comment:1 Changed 2 years ago by mdounin

  • Status changed from new to accepted

The problem that rewrite module directives (set, if) are not inherited into the limit_except block, and not executed there. As such, the $upstream variable is not set, and proxy_pass complains. This behaviour is basically identical to a nested location block.

An obvious workaround would be to use map instead, for example:

map $http_user_agent $upstream {
    default http://127.0.0.1:8080;
    mobile http://127.0.0.1:8080;
}

server {
    listen       *:80 default_server;

    location / {
        limit_except GET POST {
            allow 127.0.0.1/32;
            deny all;
        }

        proxy_pass              $upstream;
        proxy_set_header        Host $host;
        proxy_set_header        X-Forwarded-For $remote_addr;
    }
}

It doesn't looks possible to fix this without disallowing all the configuration directives inside an if in location first. See also #633, #86.

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