On 2018/11/22 19:55, owl700@xxxxxxxxx wrote: > Hi, I have compatibility issues with the latest version of > openssh-server and an old dropbear client, the dopbear client stops at > preauth > > ov 22 14:34:03 myhostname sshd[3905]: debug1: Client protocol version > 2.0; client software version dropbear_0.46 > Nov 22 14:34:03 myhostname sshd[3905]: debug1: no match: dropbear_0.46 > Nov 22 14:34:03 myhostname sshd[3905]: debug1: Local version string > SSH-2.0-OpenSSH_7.4p1 Debian-10+deb9u4 > Nov 22 14:34:03 myhostname sshd[3905]: debug1: Enabling compatibility > mode for protocol 2.0 > Nov 22 14:34:03 myhostname sshd[3905]: debug2: fd 3 setting O_NONBLOCK > Nov 22 14:34:03 myhostname sshd[3905]: debug2: Network child is on pid 3906 > Nov 22 14:34:03 myhostname sshd[3905]: debug3: preauth child monitor started > Nov 22 14:34:03 myhostname sshd[3905]: debug3: privsep user:group > 106:65534 [preauth] > Nov 22 14:34:03 myhostname sshd[3905]: debug1: permanently_set_uid: > 106/65534 [preauth] > Nov 22 14:34:03 myhostname sshd[3905]: debug1: list_hostkey_types: > ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256 [preauth] > Nov 22 14:34:03 myhostname sshd[3905]: debug3: send packet: type 20 [preauth] > Nov 22 14:34:03 myhostname sshd[3905]: debug1: SSH2_MSG_KEXINIT sent [preauth] > > Can you help? That ~13-year-old version of dbclient only has weak key exchange methods - diffie-hellman-group1-sha1, "OpenSSH supports this method, but does not enable it by default because is weak and within theoretical range of the so-called Logjam attack" and diffie-hellman-group1-dss, disabled by default in OpenSSH in 2015. Also only weak CBC-mode ciphers, disabled by default in 2014. The right answer is to run a newer client. If there's no way to do that, least worst is probably to connect to a jump host on the LAN (locked-down as much as possible), running modern OpenSSH sshd but with weak kex/ciphers enabled, in this case you could use something like KexAlgorithms +diffie-hellman-group1-sha1 Ciphers +aes128-cbc This is still not recommended, but at least you could keep the weak crypto off the internet this way. _______________________________________________ openssh-unix-dev mailing list openssh-unix-dev@xxxxxxxxxxx https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev
