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
Include OpenSSH client configuration file during build.
Signed-off-by: Peter Müller peter.mueller@link38.eu --- lfs/openssh | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/lfs/openssh b/lfs/openssh index a88b2d126..0e6acc227 100644 --- a/lfs/openssh +++ b/lfs/openssh @@ -100,5 +100,10 @@ $(TARGET) : $(patsubst %,$(DIR_DL)/%,$(objects)) -e 's|^#?HostKey /etc/ssh/ssh_host_ed25519_key$$||' \ -e 's|^#?HostKey /etc/ssh/ssh_host_rsa_key$$|HostKey /etc/ssh/ssh_host_ecdsa_key\nHostKey /etc/ssh/ssh_host_ed25519_key\nHostKey /etc/ssh/ssh_host_rsa_key|' \ /etc/ssh/sshd_config + + # install custom OpenSSH client configuration + install -v -m 644 $(DIR_SRC)/config/ssh/ssh_config \ + /etc/ssh/ssh_config + @rm -rf $(DIR_APP) @$(POSTBUILD)
Hello,
did you notice that this file is excluded from being updated on existing installations?
How do we handle any custom changes from users here?
I merged this for new installations already.
-Michael
On Mon, 2018-09-10 at 16:29 +0200, Peter Müller wrote:
Include OpenSSH client configuration file during build.
Signed-off-by: Peter Müller peter.mueller@link38.eu
lfs/openssh | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/lfs/openssh b/lfs/openssh index a88b2d126..0e6acc227 100644 --- a/lfs/openssh +++ b/lfs/openssh @@ -100,5 +100,10 @@ $(TARGET) : $(patsubst %,$(DIR_DL)/%,$(objects)) -e 's|^#?HostKey /etc/ssh/ssh_host_ed25519_key$$||' \ -e 's|^#?HostKey /etc/ssh/ssh_host_rsa_key$$|HostKey /etc/ssh/ssh_host_ecdsa_key\nHostKey /etc/ssh/ssh_host_ed25519_key\nHostKey /etc/ssh/ssh_host_rsa_key|' \ /etc/ssh/sshd_config
- # install custom OpenSSH client configuration
- install -v -m 644 $(DIR_SRC)/config/ssh/ssh_config \
/etc/ssh/ssh_config- @rm -rf $(DIR_APP) @$(POSTBUILD)
Hello Michael,
Hello,
did you notice that this file is excluded from being updated on existing installations?
no - but I should have thought about that. :-\
How do we handle any custom changes from users here?
The only possibility of keeping the user's settings is to move existing SSH client configurations to a new location, replace /etc/ssh/ssh_config with this one and include the version before.
However, I strongly advise against this. (For example, some settings in the original config might revert hardening options, causing no security benefit after all.)
Since it is "just" the client configuration, I consider overwriting it the best procedure. Of course, there has to be a yellow warning box in the release notes, but it is better than no hardening at all.
I merged this for new installations already.
Great. SSH server configuration will follow.
Best regards, Peter Müller
-Michael
On Mon, 2018-09-10 at 16:29 +0200, Peter Müller wrote:
Include OpenSSH client configuration file during build.
Signed-off-by: Peter Müller peter.mueller@link38.eu
lfs/openssh | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/lfs/openssh b/lfs/openssh index a88b2d126..0e6acc227 100644 --- a/lfs/openssh +++ b/lfs/openssh @@ -100,5 +100,10 @@ $(TARGET) : $(patsubst %,$(DIR_DL)/%,$(objects)) -e 's|^#?HostKey /etc/ssh/ssh_host_ed25519_key$$||' \ -e 's|^#?HostKey /etc/ssh/ssh_host_rsa_key$$|HostKey /etc/ssh/ssh_host_ecdsa_key\nHostKey /etc/ssh/ssh_host_ed25519_key\nHostKey /etc/ssh/ssh_host_rsa_key|' \ /etc/ssh/sshd_config
- # install custom OpenSSH client configuration
- install -v -m 644 $(DIR_SRC)/config/ssh/ssh_config \
/etc/ssh/ssh_config- @rm -rf $(DIR_APP) @$(POSTBUILD)
-
Michael Tremer -
Peter Müller