Description of problem:
The default configuration of openssh-server 6.7 disables some of the supported Ciphers and MACs. "In particular, CBC ciphers and arcfour* are disabled by default." [1]. MACs that are disabled by default are *md5*, *ripemd160*, *sha1*96*.

Version-Release number of selected component (if applicable):
openssh-6.6.1p1-25.el7_2

How reproducible:
always

Steps to Reproduce:

1. yum distribution-synchronization  # just to ensure the latest RHEL is installed

2. rm /etc/ssh/sshd_config

3. yum reinstall openssh-server      # recreates default /etc/ssh/sshd_config

4. sshd -T | grep -i "Ciphers\|MACs" # lists currently enabled Ciphers and MACs


Actual results:
The default enabled Ciphers include *cbc*, *arcfour*.
The default enabled MACs include *md5*, *ripemd160*, *sha1*96*.

Actual results of the command sshd -T | grep -i "Ciphers\|MACs"
ciphers 3des-cbc,blowfish-cbc,cast128-cbc,arcfour,arcfour128,arcfour256,aes128-cbc,aes192-cbc,aes256-cbc,rijndael-cbc.se,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm,aes256-gcm,chacha20-poly1305
macs hmac-sha1,hmac-sha1-96,hmac-sha2-256,hmac-sha2-512,hmac-md5,hmac-md5-96,hmac-ripemd160,hmac-ripemd160,umac-64,umac-128,hmac-sha1-etm,hmac-sha1-96-etm,hmac-sha2-256-etm,hmac-sha2-512-etm,hmac-md5-etm,hmac-md5-96-etm,hmac-ripemd160-etm,umac-64-etm,umac-128-etm


Expected results:
Defaults follow recent OpenSSH upstream versions.
These Ciphers are disabled by default: *cbc*, *arcfour*.
These MACs are disabled by default: *md5*, *ripemd160*, *sha1*96*.

Expected results of the command sshd -T | grep -i "Ciphers\|MACs"
ciphers aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm,aes256-gcm,chacha20-poly1305
macs hmac-sha1,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,hmac-ripemd160,umac-64,umac-128,hmac-sha1-etm,hmac-sha2-256-etm,hmac-sha2-512-etm,hmac-ripemd160-etm,umac-64-etm,umac-128-etm


Additional info:
* Red Hat's KB article about insecure Ciphers and MACs recommends non-default values [3]
* The latest RH-shipped version is 6.6.1p1 / 5.3p1; however it would be good to follow current security recommendations regarding the defaults.
* We have a Red Hat Insights rule for OpenSSH hardening that would get activated once the defaults in the openssh-server package are fixed. Red Hat Insights is a service to notify enrolled customers about problems on their systems. It is best when customers are not alerted about RHEL-default values.
* OpenSSH 6.7 through 7.1 disables hmac-sha1-etm and hmac-sha1 but OpenSSH 7.2 reenables it.
References:
[1] http://www.openssh.com/txt/release-6.7
[2] http://www.openssh.com/txt/release-7.2
[3] https://access.redhat.com/solutions/420283