IOS keep asking password with nginx auth_basic

[tiendungitd]

> The access log that I see there does not seem to show me what you
describe.
Well, I just hightlight what I described, see http://prntscr.com/pm2qhl
> Can you show an nginx configuration that leads to the problem that you
report?
Sure, you can see in https://pastebin.com/iagU4XFC
> Does nginx just serve from the filesystem, or does it proxy_pass to an
upstream server?
It proxy_pass to the upstream server.
I tried which some IOS devices, they all got this issues.
Here is my nginx version

nginx version: nginx/1.13.6
built by gcc 4.8.4 (Ubuntu 4.8.4-2ubuntu1~14.04.3)
built with OpenSSL 1.0.1f 6 Jan 2014
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
--param=ssp-buffer-size=4 -Wformat -Werror=format-security
-Wp,-D_FORTIFY_SOURCE=2 -fPIC' --with-ld-opt='-Wl,-Bsymbolic-functions
-Wl,-z,relro -Wl,-z,now -Wl,--as-needed -pie'

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,285874,285950#msg-285950