Trying to ssh and ssh-keyscan from Mac OS (Sierra 10.12.5) to a device, I was getting this error initially, "Unable to negotiate with 10.10.0.1 port 22: no matching key exchange method found. Their offer: diffie-hellman-group1-sha1".
I modified the /etc/ssh/ssh_config file as below. That made it work for "ssh" command.
Host *
HostkeyAlgorithms ssh-dss,ssh-rsa
KexAlgorithms +diffie-hellman-group1-sha1
However, "ssh-keyscan" is still complaining that no kex algo matched. I don't see the "diffie-hellman-group1-sha1" line in the list of KEX algo from the local client KXINIT proposal as in the output below.
$ ssh-keyscan -vv 10.10.0.1
debug2: fd 3 setting O_NONBLOCK
debug2: fd 4 setting O_NONBLOCK
debug2: fd 5 setting O_NONBLOCK
debug1: match: Cisco-1.25 pat Cisco-1.* compat 0x60000000
# 10.10.0.1:22 SSH-2.0-Cisco-1.25
debug1: Enabling compatibility mode for protocol 2.0
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1
debug2: host key algorithms: ssh-rsa
debug2: ciphers ctos: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-cbc,aes192-cbc,aes256-cbc
debug2: ciphers stoc: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-cbc,aes192-cbc,aes256-cbc
debug2: MACs ctos: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,zlib@openssh.com
debug2: compression stoc: none,zlib@openssh.com
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: diffie-hellman-group1-sha1
debug2: host key algorithms: ssh-rsa
debug2: ciphers ctos: aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc
debug2: ciphers stoc: aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc
debug2: MACs ctos: hmac-sha1,hmac-sha1-96,hmac-md5,hmac-md5-96
debug2: MACs stoc: hmac-sha1,hmac-sha1-96,hmac-md5,hmac-md5-96
debug2: compression ctos: none
debug2: compression stoc: none
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug1: kex: algorithm: (no match)
Is there another config file param to make this work with ssh-keyscan?
Regards, Rick.
