"Public key content has been used." on mssql after first key

• Gogs version (or commit ref): 0.11.4.0405
• Git version: ~2.7
• Operating system: ~Ubuntu Server 16.04.2 LTS
• Database (use [x]):
  • PostgreSQL
  • MySQL
  • MSSQL
  • SQLite
• Can you reproduce the bug at https://try.gogs.io:
  • Yes (provide example URL)
  • No
  • Not relevant
• Log gist (usually found in log/gogs.log):

Description

• If I try to add a ssh key the error message "Public key content has been used." is displayd. User does not matter.
• The very first ssh-key for the first user is added.
• If I manually add a key to the Database and "Rewrite '.ssh/authorized_keys' file" the key is written and working

SQL Profiler yields the following statements (User-ID: 3):

exec sp_executesql N'SELECT "id", "owner_id", "name", "fingerprint", "content", "mode", "type", "created_unix", "updated_unix" FROM "public_key" WHERE owner_id = @p1',N'@p1 bigint',@p1=3

=> yields 2 records for 2 keys

exec sp_executesql N'SELECT  TOP 1 "id", "owner_id", "name", "fingerprint", "content", "mode", "type", "created_unix", "updated_unix" FROM "public_key" WHERE "type"=@p1',N'@p1 bigint',@p1=1

=> yields 1 record for 2 keys

I guess this is the function that checks if the key exists: https://github.com/gogits/gogs/blob/63598688e454274da53fea1d072d60dd0e783c4b/models/ssh_key.go#L368

if yes, could it be that the content is missing in the last sql query generated?

Start with the linked function in models/ssh_key.go and compare it with the MSSQL queries captured in the SQL Profiler output. Reproduce the first-key and second-key cases on MSSQL, then verify that adding another distinct SSH key no longer reports it as already used.