Redmine

production.log with debug level logging:
Started POST "/redmine/login" for 192.168.1.3 at 2015-11-29 15:25:33 +0900
Processing by AccountController#login as HTML
Parameters: {"utf8"=>"?", "authenticity_token"=>"mLheHakimu3JuJeQuUtecekPEBnc59Y5ItUYAvDuIBRYqlVvIDxqp8cd7HDwZcUZ2ucEZHsDkAiSnv6fgYi1xg==", "back_url"=>"https://nekochan.homedns.org/redmine/", "username"=>"tyano", "password"=>"[FILTERED]", "login"=>"ログイン ≫"}
Current user: anonymous
Failed login for 'tyano' from 192.168.1.3 at 2015-11-29 06:25:33 UTC
Rendered account/login.html.erb within layouts/base (3.0ms)
Completed 200 OK in 72ms (Views: 18.3ms | ActiveRecord: 2.0ms)
Started POST "/redmine/login" for 192.168.1.3 at 2015-11-29 15:26:46 +0900
Processing by AccountController#login as HTML
Parameters: {"utf8"=>"?", "authenticity_token"=>"7tl8YD67xlAo5fNWhkKO1iMtDjLNV9GEw5jF37PjDJkuy3cSt6U2GiZAiLbPbBW+EMUaT2qzl7Vz0yNCwoWZSw==", "back_url"=>"https://nekochan.homedns.org/redmine/", "username"=>"tyano", "password"=>"[FILTERED]", "login"=>"ログイン ≫"}
Current user: anonymous
Failed login for 'tyano' from 192.168.1.3 at 2015-11-29 06:26:47 UTC
Rendered account/login.html.erb within layouts/base (3.0ms)
Completed 200 OK in 68ms (Views: 17.9ms | ActiveRecord: 2.0ms)
Started POST "/redmine/login" for 192.168.1.3 at 2015-11-29 15:27:06 +0900
Processing by AccountController#login as HTML

Please give us Submissions.

Submissions:

The simplest way to get information about your environment is to run the following command from within your Redmine installation:
Redmine 3.x:
ruby bin/about
Redmine 2.x:
ruby script/about

I am runnig 3.1.2 and 3.1.1. Both of 3.1.1 and 3.1.2 the problem occurs.
bin/about shows:
Environment:
Redmine version 3.1.1.stable
Ruby version 1.9.3-p484 (2013-11-22) [x86_64-linux]
Rails version 4.2.4
Environment production
Database adapter SQLite
SCM:
Subversion 1.8.8
Git 1.9.1
Filesystem
Redmine plugins:
redmine_agile 1.3.9
redmine_issue_templates 0.1.1

Takashi YANO wrote:

Environment production
Database adapter SQLite

Why do you use SQLite on production?
Do you sure you use LDAP authentication?
How do you upgrade?

Why do you use SQLite on production?
-> Only 2 or 3 users are using this redmine.

Do you sure you use LDAP authentication?
> Yes. If I swtich authentication to internal, it works.
> On 3.0, I could logon with LDAP authentication.
How do you upgrade?
->
tar zxvf redmine-3.1.2.tar.gz
cd ./redmine-3.1.2
cp -rpv ../redmine-3.0.0/files/ .
cp -rpv ../redmine-3.0.0/plugins/ .
cp -rpv ../redmine-3.0.0/db/ .
cp -pv ../redmine-3.0.0/config/database.yml config/
cp ../redmine-3.0.0/config/configuration.yml config/
service apache2 stop
gem update bundler
bundle install --without development test postgresql
bundle exec rake generate_secret_token
bundle exec rake db:migrate RAILS_ENV=production
bundle exec rake redmine:plugins:migrate RAILS_ENV=production
bundle exec rake tmp:cache:clear tmp:sessions:clear
chown -R www-data:www-data .
[edit /etc/apache2/conf-enabled/redmine.conf]
service apache2 start

By the way I have an idea:
define a new LDAP connaction with the same configuration of the old one and use it.
I will try