Introduce a custom OpenSSH client configuration file for IPFire. Some people use it as a jumping host, so applying hardening options system-wide improves security.
Cryptography setup is the same as for OpenSSH server configuration.
The second version of this patch re-adds some non-AEAD cipher suites which are needed for connecting to older RHEL systems.
Partially fixes #11751
Signed-off-by: Peter Müller peter.mueller@link38.eu --- config/ssh/ssh_config | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) create mode 100644 config/ssh/ssh_config
diff --git a/config/ssh/ssh_config b/config/ssh/ssh_config new file mode 100644 index 000000000..2abfae6d1 --- /dev/null +++ b/config/ssh/ssh_config @@ -0,0 +1,33 @@ +# OpenSSH client configuration +# +# set some basic hardening options for all connections +Host * + # disable Roaming as it is known to be vulnerable + UseRoaming no + + # only use secure crypto algorithm + KexAlgorithms curve25519-sha256@libssh.org,diffie-hellman-group-exchange-sha256 + Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr + MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,umac-128@openssh.com + + # always visualise server host keys (has no technical + # effect, but helps to identify key based MITM attacks) + VisualHostKey yes + + # use SSHFP (might work on some up-to-date networks) to look up host keys + VerifyHostKeyDNS yes + + # send keep-alive messages to connected server to avoid broken connections + ServerAliveInterval 10 + ServerAliveCountMax 6 + + # disable X11 forwarding (security risk) + ForwardX11 no + + # always check server IP address + CheckHostIP yes + + # ensure only allowed authentication methods are used + PreferredAuthentications publickey,keyboard-interactive,password + +# EOF