Opened 8 months ago

Closed 8 months ago

#1460 closed defect (worksforme)

$uri is double-decoded, reporting wrong value

Reported by: apps.viva.org.uk@… Owned by:
Priority: major Milestone:
Component: nginx-core Version: 1.10.x
Keywords: Cc:
uname -a: Linux ???? 4.9.36-x86_64-???? #1 SMP Thu Jul 6 15:31:23 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
nginx -V: nginx version: nginx/1.10.3 (Ubuntu) built with OpenSSL 1.0.2g 1 Mar 2016 TLS SNI support enabled configure arguments: --with-cc-opt='-g -O2 -fPIE -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2' --with-ld-opt='-Wl,-Bsymbolic-functions -fPIE -pie -Wl,-z,relro -Wl,-z,now' --prefix=/usr/share/nginx --conf-path=/etc/nginx/nginx.conf --http-log-path=/var/log/nginx/access.log --error-log-path=/var/log/nginx/error.log --lock-path=/var/lock/nginx.lock --pid-path=/run/nginx.pid --http-client-body-temp-path=/var/lib/nginx/body --http-fastcgi-temp-path=/var/lib/nginx/fastcgi --http-proxy-temp-path=/var/lib/nginx/proxy --http-scgi-temp-path=/var/lib/nginx/scgi --http-uwsgi-temp-path=/var/lib/nginx/uwsgi --with-debug --with-pcre-jit --with-ipv6 --with-http_ssl_module --with-http_stub_status_module --with-http_realip_module --with-http_auth_request_module --with-http_addition_module --with-http_dav_module --with-http_flv_module --with-http_geoip_module --with-http_gunzip_module --with-http_gzip_static_module --with-http_image_filter_module --with-http_mp4_module --with-http_perl_module --with-http_random_index_module --with-http_secure_link_module --with-http_v2_module --with-http_sub_module --with-http_xslt_module --with-mail --with-mail_ssl_module --with-stream --with-stream_ssl_module --with-threads --add-module=/build/nginx-Q158zN/nginx-1.10.3/debian/modules/headers-more-nginx-module --add-module=/build/nginx-Q158zN/nginx-1.10.3/debian/modules/nginx-auth-pam --add-module=/build/nginx-Q158zN/nginx-1.10.3/debian/modules/nginx-cache-purge --add-module=/build/nginx-Q158zN/nginx-1.10.3/debian/modules/nginx-dav-ext-module --add-module=/build/nginx-Q158zN/nginx-1.10.3/debian/modules/nginx-development-kit --add-module=/build/nginx-Q158zN/nginx-1.10.3/debian/modules/nginx-echo --add-module=/build/nginx-Q158zN/nginx-1.10.3/debian/modules/ngx-fancyindex --add-module=/build/nginx-Q158zN/nginx-1.10.3/debian/modules/nginx-http-push --add-module=/build/nginx-Q158zN/nginx-1.10.3/debian/modules/nginx-lua --add-module=/build/nginx-Q158zN/nginx-1.10.3/debian/modules/nginx-upload-progress --add-module=/build/nginx-Q158zN/nginx-1.10.3/debian/modules/nginx-upstream-fair --add-module=/build/nginx-Q158zN/nginx-1.10.3/debian/modules/ngx_http_substitutions_filter_module

Description

The config file variable $uri is a normalised version of $request_uri with URL entities decoded (e.g. %21 is decoded to !). The bug occurs if $request_uri includes %25 (which decodes to %) because then it is decoded a second time, which causes problems if there are numbers following it.

You can see the correct behaviour if the URL contains an encoded character other than %25:

Example $request_uri: /one-%2126-two
Actual (correct) $uri: one-!26-two

And now see the problem happens when %25 is used:

Example $request_uri: /one-%2526-two
Expected (correct) $uri: one-%26-two
Actual (wrong) $uri: one-&-two

The $uri should only be decoded once and contain %26, but it's actually being decoded twice and returning &.

Change History (1)

comment:1 Changed 8 months ago by mdounin

  • Resolution set to worksforme
  • Status changed from new to closed

A simple test case:

location / {
    return 200 "request: $request_uri\nuri: $uri\n";
}

Test results:

$ curl http://127.0.0.1:8080/one-%2126-two
request: /one-%2126-two
uri: /one-!26-two
$ curl http://127.0.0.1:8080/one-%2526-two
request: /one-%2526-two
uri: /one-%26-two

As you can see, in both cases $uri is correctly decoded once. Second decoding likely happens for some reason in your particular configuration. In particular, a rewrite which uses $uri in the replacement string might do this, as rewrite assumes that variables in the replacement string are escaped (and unescapes URI part as needed).

Note: See TracTickets for help on using tickets.