APPLIES TO : Solaris Operating System - Version 10 3/05 to 11.3
GOAL : This document explains how to determine which SSH Cyphers and HMAC Algorithms are in use by the SSH client/server and how to configure/limit these.
SOLUTION : To check for the offered ciphers and HMAC algorithms of an ssh server, you can use the command 'ssh -vvv remote_host' and verify the debug output of the session.
This will tell you which ciphers and HMAC algorithms are available on the client and server side. It will also tell you which one will be use after the negotiation.
Script to find weak ciphers Covered in another blog
Example:
$ ssh -vvv remote_host
Sun_SSH_2.2, SSH protocols 1.5/2.0, OpenSSL 0x1000110f
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Rhosts Authentication disabled, originating port will not be trusted.
debug1: ssh_connect: needpriv 0
debug1: Connecting to remote_host [10.163.240.26] port 22.
debug1: Connection established.
debug1: ssh_kmf_check_uri: /export/home/jack/.ssh/identity
debug1: Identity file/URI '/export/home/jack/.ssh/identity' pubkey type UNKNOWN
debug1: ssh_kmf_check_uri: /export/home/jack/.ssh/id_rsa
debug1: Identity file/URI '/export/home/jack/.ssh/id_rsa' pubkey type UNKNOWN
debug1: ssh_kmf_check_uri: /export/home/jack/.ssh/id_dsa
debug1: Identity file/URI '/export/home/jack/.ssh/id_dsa' pubkey type UNKNOWN
debug1: Logging to host: remote_host
debug1: Local user: jack Remote user: jack
debug1: Remote protocol version 2.0, remote software version Sun_SSH_2.2
debug1: match: Sun_SSH_2.2 pat Sun_SSH_2.*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-Sun_SSH_2.2
debug1: use_engine is 'yes'
debug1: pkcs11 engine initialized, now setting it as default for RSA, DSA, and symmetric ciphers
debug1: pkcs11 engine initialization complete
debug1: Creating a global KMF session.
debug1: My KEX proposal before adding the GSS KEX algorithm:
debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss,x509v3-sign-rsa,x509v3-sign-dss
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour128,arcfour256,arcfour,aes128-cbc,aes192-cbc,aes256-cbc,blowfish-cbc,3des-cbc
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour128,arcfour256,arcfour,aes128-cbc,aes192-cbc,aes256-cbc,blowfish-cbc,3des-cbc
debug2: kex_parse_kexinit: hmac-sha2-256,hmac-sha2-512,hmac-sha1,hmac-sha2-256-96,hmac-sha2-512-96,hmac-sha1-96,hmac-md5,hmac-md5-96
debug2: kex_parse_kexinit: hmac-sha2-256,hmac-sha2-512,hmac-sha1,hmac-sha2-256-96,hmac-sha2-512-96,hmac-sha1-96,hmac-md5,hmac-md5-96
debug2: kex_parse_kexinit: none,zlib
debug2: kex_parse_kexinit: none,zlib
debug2: kex_parse_kexinit: en-US
debug2: kex_parse_kexinit: en-US
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug1: Failed to acquire GSS-API credentials for any mechanisms (No credentials were supplied, or the credentials were unavailable or inaccessible
)
debug1: SSH2_MSG_KEXINIT sent
debug3: kex_reset_dispatch -- should we dispatch_set(KEXINIT) here? 0 && !0
debug1: SSH2_MSG_KEXINIT received
debug1: My KEX proposal I sent to the peer:
debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss,x509v3-sign-rsa,x509v3-sign-dss
A)======The ssh client offered the following Ciphers==========
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour128,arcfour256,arcfour,aes128-cbc,aes192-cbc,aes256-cbc,blowfish-cbc,3des-cbc
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour128,arcfour256,arcfour,aes128-cbc,aes192-cbc,aes256-cbc,blowfish-cbc,3des-cbc
B)======The ssh client offered the following HMAC Algorithms==========
debug2: kex_parse_kexinit: hmac-sha2-256,hmac-sha2-512,hmac-sha1,hmac-sha2-256-96,hmac-sha2-512-96,hmac-sha1-96,hmac-md5,hmac-md5-96
debug2: kex_parse_kexinit: hmac-sha2-256,hmac-sha2-512,hmac-sha1,hmac-sha2-256-96,hmac-sha2-512-96,hmac-sha1-96,hmac-md5,hmac-md5-96
debug2: kex_parse_kexinit: none,zlib
debug2: kex_parse_kexinit: none,zlib
debug2: kex_parse_kexinit: en-US
debug2: kex_parse_kexinit: en-US
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug1: KEX proposal I received from the peer:
debug2: kex_parse_kexinit: gss-group1-sha1-toWM5Slw5Ew8Mqkay+al2g==,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss
C)=====The sshd server offered the following Ciphers===========
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour128,arcfour256,arcfour
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour128,arcfour256,arcfour
D)======The ssh server offered or replied the following HMAC Algorithms==========
debug2: kex_parse_kexinit: hmac-sha2-256,hmac-sha2-512,hmac-sha1,hmac-sha2-256-96,hmac-sha2-512-96,hmac-sha1-96,hmac-md5,hmac-md5-96
debug2: kex_parse_kexinit: hmac-sha2-256,hmac-sha2-512,hmac-sha1,hmac-sha2-256-96,hmac-sha2-512-96,hmac-sha1-96,hmac-md5,hmac-md5-96
debug2: kex_parse_kexinit: none,zlib
debug2: kex_parse_kexinit: none,zlib
debug2: kex_parse_kexinit: de-DE,en-US,es-ES,fr-FR,it-IT,ja-JP,ko-KR,pt-BR,zh-CN,zh-TW,i-default
debug2: kex_parse_kexinit: de-DE,en-US,es-ES,fr-FR,it-IT,ja-JP,ko-KR,pt-BR,zh-CN,zh-TW,i-default
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: mac_setup: found hmac-sha2-256
E)======The Cipher and HMAC Algorithm used after the negotiation==========
debug1: kex: server->client aes128-ctr hmac-sha2-256 none
debug2: mac_setup: found hmac-sha2-256
debug1: kex: client->server aes128-ctr hmac-sha2-256 none
debug1: Host key algorithm 'ssh-rsa' chosen for the KEX.
debug1: Peer sent proposed langtags, ctos: de-DE,en-US,es-ES,fr-FR,it-IT,ja-JP,ko-KR,pt-BR,zh-CN,zh-TW,i-default
debug1: Peer sent proposed langtags, stoc: de-DE,en-US,es-ES,fr-FR,it-IT,ja-JP,ko-KR,pt-BR,zh-CN,zh-TW,i-default
debug1: We proposed langtags, ctos: en-US
debug1: We proposed langtags, stoc: en-US
debug1: Negotiated lang: en-US
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug1: Remote: Negotiated main locale: en_US.UTF-8
debug1: Remote: Negotiated messages locale: en_US.UTF-8
debug1: dh_gen_key: priv key bits set: 251/512
debug1: bits set: 2062/4095
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug1: ssh_kmf_key_from_blob: blob length is 277.
debug3: check_host_in_hostfile: filename /export/home/jack/.ssh/known_hosts
debug3: check_host_in_hostfile: filename /etc/ssh/ssh_known_hosts
debug3: check_host_in_hostfile: filename /export/home/jack/.ssh/known_hosts
debug3: check_host_in_hostfile: filename /etc/ssh/ssh_known_hosts
debug3: check_host_in_hostfile: filename /export/home/jack/.ssh/known_hosts
debug3: check_host_in_hostfile: filename /etc/ssh/ssh_known_hosts
debug2: no key of type 0 for host remote_host
From the above debug output, one can see the following steps:
A) The ssh client offered the following Ciphers:
aes128-ctr,aes192-ctr,aes256-ctr,arcfour128,arcfour256,arcfour,aes128-cbc,aes192-cbc,aes256-cbc,blowfish-cbc,3des-cbc
B) The ssh client offered the following HMAC Algorithms:
hmac-sha2-256,hmac-sha2-512,hmac-sha1,hmac-sha2-256-96,hmac-sha2-512-96,hmac-sha1-96,hmac-md5,hmac-md5-96
C) The sshd server offered the following Ciphers:
aes128-ctr,aes192-ctr,aes256-ctr,arcfour128,arcfour256,arcfour
D) The ssh server offered the following HMAC Algorithms:
hmac-sha2-256,hmac-sha2-512,hmac-sha1,hmac-sha2-256-96,hmac-sha2-512-96,hmac-sha1-96,hmac-md5,hmac-md5-96
E) The Cipher and HMAC Algorithm used after the negotiation:
aes128-ctr hmac-sha2-256
If you need to configure or limit the offered ciphers, use the /etc/ssh/sshd_config file on the server side
and the /etc/ssh/ssh_config on the client side, and specify your own set in the "Ciphers ...." and/or "MACs ...." lines.
Example:
The following entries in /etc/ssh/sshd_config and /etc/ssh/ssh _config file will :
Disable the arcfour and CBC mode ciphers
Disable the MD5 and -96 MAC algorithms
cp -p /etc/ssh/sshd_config /etc/ssh/sshd_config.`date +%d-%b-%Y-%H-%M`
vi /etc/ssh/sshd_config
Ciphers aes128-ctr,aes192-ctr,aes256-ctr
Macs hmac-sha2-256,hmac-sha2-512,
svcadm restart ssh
Oracle Document Reference (Doc ID 2086158.1)
Script to find weak ciphers Covered in another blog
~Judi~
Disable weak SSH Cyphers and HMAC Algorithms;
Disable weak MD5 and -96 MAC algorithms;
SSH Weak MAC Algorithms;
Solaris 10;
Solaris 11;
Ciphers aes128-ctr,aes192-ctr,aes256-ctr;
Macs hmac-sha2-256,hmac-sha2-512;
aes128-ctr,aes192-ctr,aes256-ctr,arcfour128,arcfour256,arcfour,aes128-cbc,aes192-cbc,aes256-cbc,blowfish-cbc,3des-cbc
hmac-sha2-256,hmac-sha2-512,hmac-sha1,hmac-sha2-256-96,hmac-sha2-512-96,hmac-sha1-96,hmac-md5,hmac-md5-96;
how to disable weak ciphers in solaris 10;
failed to acquire gss-api credentials for any mechanisms;
ssh weak mac algorithms enabled;
ssh server cbc mode ciphers enabled;
How to Disable Ciphers and Reconfigure Encryption
how to enable some cipher or esclude weak cipher
encryption - SSH: How to disable weak ciphers?
Disable weak ssl ciphers HTTPD apache | Unix Sun Solaris Admin tricks
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