Login attempt for nonexistent user on Alpine Linux

[Hugo Genesse]

Hi!

I've been trying to use dropbear (compiled myself statically with  
./configure; make STATIC=1) on a Alpine Linux Docker container (Linux  
4.13.12-1-ARCH) with the latest Alpine Docker image (3.6 if I'm not  
mistaken). I run dropbear like this: "./dropbear -R" and can't login  
with proper credentials. With the "-E" switch I get the following:

  /root/dropbear -R -E
[59] Dec 01 04:31:32 Running in background
[60] Dec 01 04:31:36 Child connection from <IP>
[60] Dec 01 04:31:36 Login attempt for nonexistent user from <IP>

My credentials are right and the command to connect is: "ssh  
root at 127.0.0.1" (the port is properly forwarded to the container).  
With the ssh client verbose option I get:

debug1: Next authentication method: password
root at 127.0.0.1's password:
debug1: Authentications that can continue: publickey,password
Permission denied, please try again.
root at 127.0.0.1's password:
debug1: Authentications that can continue: publickey,password
Permission denied, please try again.
root at 127.0.0.1's password:
debug1: Authentications that can continue: publickey,password
debug1: No more authentication methods to try.
root at 127.0.0.1: Permission denied (publickey,password).

and the root account exists as you can see here:

cat /etc/passwd
root:x:0:0:root:/root:/bin/ash
[...]

I've seen issues that seem similar on the web:  
https://lists.debian.org/debian-arm/2012/06/msg00056.html
The ones I found were fixed by copying libnss to another location but  
shouldn't a statically dropbear already solve this problem?

I also have telnet activated and I can login with root (don't worry  
this won't be put into production, it is for demonstration purposes  
only).

Is there any other things I should check or modify to be able to login  
with dropbear?

Thanks!