id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	uname	nginx_version
2016	nginx does not percent-encode Location header properly	yurivkhan@…		"When nginx is serving static files and the client requests a path that maps to a name of a directory, nginx will respond with a 301 status code and a Location header, redirecting to the same path with a trailing slash.

This Location header is not properly percent-encoded. Example 1:

{{{
$ mkdir ""/var/www/html/test dir""
$ curl -v ""localhost/test dir"" 2>&1 | grep Location
< Location: http://localhost/test dir/
}}}

Example 2:

{{{
$ mkdir ""/var/www/html/баг""
$ curl -v ""localhost/%D0%B1%D0%B0%D0%B3"" 2>&1 | grep Location
< Location: http://localhost/баг/
}}}

The Location header is defined in RFC 7231 section 7.1.2 as having a value of URI-reference, which, in turn, is defined in RFC 3986 section 4.1. The BNF grammar there allows a subset of ASCII characters to appear raw; all other characters must be percent-encoding.

By sheer luck, most such percent-unencoded redirects will appear to work. However, example 3:

{{{
$ mkdir ""/var/www/html/foo%25""
$ echo 123 >""/var/www/html/foo%25/index.html""
$ mkdir ""/var/www/html/foo%2525""
$ echo 456 >""/var/www/html/foo%2525/index.html""

$ curl -v ""localhost/foo%25"" 2>&1 | grep ""< HTTP""
< HTTP/1.1 404 Not Found
# expected; foo%25 decodes to ""foo%"" and that does not exist

$ curl ""localhost/foo%2525/""
123
# expected; foo%2525 decodes to ""foo%25""

$ curl ""localhost/foo%252525/""
456
# expected; foo%252525 decodes to ""foo%2525""

$ curl -Lv ""localhost/foo%2525"" 2>&1 | grep ""> GET\|< HTTP\|Location""
> GET /foo%2525 HTTP/1.1
< HTTP/1.1 301 Moved Permanently
< Location: http://localhost/foo%25/
> GET /foo%25/ HTTP/1.1
< HTTP/1.1 404 Not Found
# Unexpected! Note that curl is diligently repeating the path given.

$ curl ""localhost/foo%252525""
123
# Unexpected! By now you see what’s happening behind the scenes.
}}}"	defect	closed	minor		nginx-module	1.18.x	duplicate		yurivkhan@…	Linux partaker 5.4.0-40-generic #44-Ubuntu SMP Tue Jun 23 00:01:04 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux	"nginx version: nginx/1.18.0 (Ubuntu)
built with OpenSSL 1.1.1f  31 Mar 2020
TLS SNI support enabled
configure arguments: --with-cc-opt='-g -O2 -fdebug-prefix-map=/build/nginx-5J5hor/nginx-1.18.0=. -fstack-protector-strong -Wformat -Werror=format-security -fPIC -Wdate-time -D_FORTIFY_SOURCE=2' --with-ld-opt='-Wl,-Bsymbolic-functions -Wl,-z,relro -Wl,-z,now -fPIC' --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 --modules-path=/usr/lib/nginx/modules --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-compat --with-pcre-jit --with-http_ssl_module --with-http_stub_status_module --with-http_realip_module --with-http_auth_request_module --with-http_v2_module --with-http_dav_module --with-http_slice_module --with-threads --with-http_addition_module --with-http_gunzip_module --with-http_gzip_static_module --with-http_image_filter_module=dynamic --with-http_sub_module --with-http_xslt_module=dynamic --with-stream=dynamic --with-stream_ssl_module --with-mail=dynamic --with-mail_ssl_module"