Hi, I have observed some strange dropbear behavior with the -R argument (Create hostkeys as required) and Elliptic Curve host keys. The result is an extremely large temporary host key file (multiple megabytes).
SSH client: Google Chrome extension: Secure Shell 0.8.25 1) Connect to dropbear running without arguments and a single host key (ecdsa-sha2-nistp521) in /etc/dropbear/dropbear_ecdsa_host_key 2) Stop dropbear 3) Remove old host key and generate a single new host key (ecdsa-sha2-nistp256) in /etc/dropbear/dropbear_ecdsa_host_key 4) Start dropbear with -R argument 5) Reconnect to dropbear and it generate an extremely large host key (process never ends). Result: root@target:~ ll /etc/dropbear/ total 54508 dr-------- 2 root root 1024 Jan 28 13:38 . drwxrwxr-x 19 root root 1024 Jan 28 12:09 .. -r-------- 1 root root 140 Jan 28 13:35 dropbear_ecdsa_host_key -rw------- 1 root root 55593054 Jan 28 13:39 dropbear_ecdsa_host_key.tmp377 root@target:~ ll /etc/dropbear/ total 66001 dr-------- 2 root root 1024 Jan 28 13:38 . drwxrwxr-x 19 root root 1024 Jan 28 12:09 .. -r-------- 1 root root 140 Jan 28 13:35 dropbear_ecdsa_host_key -rw------- 1 root root 67316589 Jan 28 13:40 dropbear_ecdsa_host_key.tmp377 root@target:~ ll /etc/dropbear/ total 70657 dr-------- 2 root root 1024 Jan 28 13:38 . drwxrwxr-x 19 root root 1024 Jan 28 12:09 .. -r-------- 1 root root 140 Jan 28 13:35 dropbear_ecdsa_host_key -rw------- 1 root root 72064080 Jan 28 13:40 dropbear_ecdsa_host_key.tmp377 root@target:~ ll /etc/dropbear/ total 84631 dr-------- 2 root root 1024 Jan 28 13:38 . drwxrwxr-x 19 root root 1024 Jan 28 12:09 .. -r-------- 1 root root 140 Jan 28 13:35 dropbear_ecdsa_host_key -rw------- 1 root root 86317002 Jan 28 13:40 dropbear_ecdsa_host_key.tmp377 root@target:~ ll /etc/dropbear/ total 129200 dr-------- 2 root root 1024 Jan 28 13:38 . drwxrwxr-x 19 root root 1024 Jan 28 12:09 .. -r-------- 1 root root 140 Jan 28 13:35 dropbear_ecdsa_host_key -rw------- 1 root root 131778657 Jan 28 13:41 dropbear_ecdsa_host_key.tmp377 root@target:~ ll /etc/dropbear/ total 130372 dr-------- 2 root root 1024 Jan 28 13:38 . drwxrwxr-x 19 root root 1024 Jan 28 12:09 .. -r-------- 1 root root 140 Jan 28 13:35 dropbear_ecdsa_host_key -rw------- 1 root root 132973731 Jan 28 13:41 dropbear_ecdsa_host_key.tmp377 root@target:~ ll /etc/dropbear/ total 131219 dr-------- 2 root root 1024 Jan 28 13:38 . drwxrwxr-x 19 root root 1024 Jan 28 12:09 .. -r-------- 1 root root 140 Jan 28 13:35 dropbear_ecdsa_host_key -rw------- 1 root root 133837839 Jan 28 13:41 dropbear_ecdsa_host_key.tmp377 root@target:~ top Mem: 121580K used, 3376K free, 0K shrd, 10172K buff, 91900K cached CPU: 20.0% usr 80.0% sys 0.0% nic 0.0% idle 0.0% io 0.0% irq 0.0% sirq Load average: 2.30 1.04 0.52 2/55 1416 PID PPID USER STAT VSZ %MEM CPU %CPU COMMAND 377 31162 root R 2292 1.8 0 66.5 dropbear -R Maybe it's a collision in /etc/dropbear/dropbear_ecdsa_host_key that holds an ecdsa-sha2-nistp256 and when dropbear tries to generate a new ecdsa-sha2-nistp521. Venlig hilsen / Best regards Kamstrup A/S <http://www.kamstrup.dk> Bruno Thomsen Development engineer Technology Kamstrup A/S Industrivej 28 DK-8660 Skanderborg Tel: +45 89 93 10 00 Fax: +45 89 93 10 01 Dir: +45 89 93 13 94 E-mail: b...@kamstrup.dk Web: www.kamstrup.dk
