Hi!
After upgrading to 2018.76, I can no longer log in. On the dropbear
end, it complains about not being able to read the host key (/mnt/nv
is the non-volatile storage in my target HW):
Mar 1 11:19:03 gbprobe authpriv.info dropbear[11579]: Child connection from
10.0.30.15:50746
Mar 1 11:19:03 gbprobe authpriv.info dropbear[11579]: Exit before auth:
Couldn't read or generate hostkey /mnt/nv/dropbear_ecdsa_host_key
The file is there, and if I put the 2017.75 binary back, it works fine.
On the client end, I see this subtle difference when running ssh -v:
* 2017.75 (working):
debug1: Remote protocol version 2.0, remote software version
dropbear_2017.75
debug1: no match: dropbear_2017.75
debug1: Authenticating to 10.0.30.175:22 as 'root'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: curve25519-sha...@libssh.org
debug1: kex: host key algorithm: ecdsa-sha2-nistp521
debug1: kex: server->client cipher: aes128-ctr MAC: hmac-sha2-256
compression: none
debug1: kex: client->server cipher: aes128-ctr MAC: hmac-sha2-256
compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp521
SHA256:9bs+RuIrv2YCscwXc9W/3FsK/emloGYZGR+fw0bzj3c
* 2018.76 (failing):
debug1: Remote protocol version 2.0, remote software version
dropbear_2018.76
debug1: no match: dropbear_2018.76
debug1: Authenticating to 10.0.30.175:22 as 'root'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: aes128-ctr MAC: hmac-sha2-256
compression: none
debug1: kex: client->server cipher: aes128-ctr MAC: hmac-sha2-256
compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
Connection closed by 10.0.30.175 port 22
The actual host key seems to be in the "521" format:
# strings /mnt/nv/dropbear_ecdsa_host_key
ecdsa-sha2-nistp521
nistp521
This seems to indicate that the issue is due to this change
- Default generated ECDSA key size is now 256 (rather than 521)
for better interoperability
But shouldn't it keep working with already existing host keys in the
other format?
Rather than modifying options.h, local options are now
placed in localoptions.h where they will override defaults.
The header file default_options.h lists the available
options similar to the old options.h - it should be left
unmodified.
Confusingly, the changelog calls it "local_options.h". Additionally, I
found that the "localoptions.h" file must be placed in the build tree,
not the source tree, when doing out-of-tree builds. This makes a lot
of sense, but took me some time to figure out :-)
--
\\// Peter - http://www.softwolves.pp.se/
