Default HSTS pinning time and Let's Encrypt certificate life time
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### Summary
Let's encrypt will only serve you a 3 month certificate and the default HSTS value is one year. When this 3 month period from LE expires, you are stuck with a broken domain and will have to move domains.
### Steps to reproduce
1. Set up gitlab to get a Let's Encrypt certificate and watch what happens after 3 months.
### Example Project
N/A
### What is the current *bug* behavior?
Not screwing the domain over by allowing a default HSTS value to be greater than LE's 3 month period if you are using LE certificates.
### What is the expected *correct* behavior?
See above.
### Relevant logs and/or screenshots
N/A
### Output of checks
N/A
#### Results of GitLab environment info
<details>
<summary>Expand for output related to GitLab environment info</summary>
<pre>
System information
System: Debian 9.5
Proxy: no
Current User: git
Using RVM: no
Ruby Version: 2.4.4p296
Gem Version: 2.7.6
Bundler Version:1.16.2
Rake Version: 12.3.1
Redis Version: 3.2.11
Git Version: 2.17.1
Sidekiq Version:5.1.3
Go Version: unknown
GitLab information
Version: 11.1.4-ee
Revision: d17962f
Directory: /opt/gitlab/embedded/service/gitlab-rails
DB Adapter: postgresql
DB Version: 9.6.8
URL: https://<censored>.red-m.net
HTTP Clone URL: https://<censored>.red-m.net/some-group/some-project.git
SSH Clone URL: git@<censored>.red-m.net:some-group/some-project.git
Elasticsearch: no
Geo: no
Using LDAP: no
Using Omniauth: no
GitLab Shell
Version: 7.1.4
Repository storage paths:
- default: /var/opt/gitlab/git-data/repositories
Hooks: /opt/gitlab/embedded/service/gitlab-shell/hooks
Git: /opt/gitlab/embedded/bin/git
</pre>
</details>
#### Results of GitLab application Check
<details>
<summary>Expand for output related to the GitLab application check</summary>
<pre>
Checking GitLab Shell ...
GitLab Shell version >= 7.1.4 ? ... OK (7.1.4)
Repo base directory exists?
default... yes
Repo storage directories are symlinks?
default... no
Repo paths owned by git:root, or git:git?
default... yes
Repo paths access is drwxrws---?
default... yes
hooks directories in repos are links: ...
17/9 ... ok
16/10 ... ok
16/11 ... ok
16/12 ... ok
17/13 ... ok
17/15 ... ok
3/21 ... ok
15/23 ... ok
5/27 ... ok
32/28 ... ok
5/29 ... ok
3/30 ... ok
91/31 ... ok
91/32 ... ok
2/33 ... ok
16/34 ... ok
89/35 ... ok
17/36 ... ok
17/37 ... ok
3/38 ... ok
21/39 ... ok
10/40 ... ok
3/41 ... ok
3/42 ... ok
3/43 ... ok
3/44 ... ok
Running /opt/gitlab/embedded/service/gitlab-shell/bin/check
Check GitLab API access: OK
Redis available via internal API: OK
Access to /var/opt/gitlab/.ssh/authorized_keys: OK
gitlab-shell self-check successful
Checking GitLab Shell ... Finished
Checking Sidekiq ...
Running? ... yes
Number of Sidekiq processes ... 1
Checking Sidekiq ... Finished
Reply by email is disabled in config/gitlab.yml
Checking LDAP ...
LDAP is disabled in config/gitlab.yml
Checking LDAP ... Finished
Checking GitLab ...
Git configured correctly? ... yes
Database config exists? ... yes
All migrations up? ... yes
Database contains orphaned GroupMembers? ... no
GitLab config exists? ... yes
GitLab config up to date? ... yes
Log directory writable? ... yes
Tmp directory writable? ... yes
Uploads directory exists? ... yes
Uploads directory has correct permissions? ... yes
Uploads directory tmp has correct permissions? ... yes
Init script exists? ... skipped (omnibus-gitlab has no init script)
Init script up-to-date? ... skipped (omnibus-gitlab has no init script)
Projects have namespace: ...
17/9 ... yes
16/10 ... yes
16/11 ... yes
16/12 ... yes
17/13 ... yes
17/15 ... yes
3/21 ... yes
15/23 ... yes
5/27 ... yes
32/28 ... yes
5/29 ... yes
3/30 ... yes
91/31 ... yes
91/32 ... yes
2/33 ... yes
16/34 ... yes
89/35 ... yes
17/36 ... yes
17/37 ... yes
3/38 ... yes
21/39 ... yes
10/40 ... yes
3/41 ... yes
3/42 ... yes
3/43 ... yes
3/44 ... yes
Redis version >= 2.8.0? ... yes
Ruby version >= 2.3.5 ? ... yes (2.4.4)
Git version >= 2.9.5 ? ... yes (2.17.1)
Git user has default SSH configuration? ... yes
Active users: ... 105
Elasticsearch version 5.1 - 5.5? ... skipped (elasticsearch is disabled)
Checking GitLab ... Finished
</pre>
</details>
### Possible fixes
When `gitlab-ctl reconfigure`ing don't allow when LE certs are being used to have a HSTS timer higher than 3 months.
issue