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Implement stribika SSH tips #16

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dolmen opened this issue Jan 7, 2015 · 6 comments
Open

Implement stribika SSH tips #16

dolmen opened this issue Jan 7, 2015 · 6 comments
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@dolmen
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dolmen commented Jan 7, 2015

https://stribika.github.io/2015/01/04/secure-secure-shell.html
https://news.ycombinator.com/item?id=8843994

  • set Protocol 2 (to override a default configuration that may allow version 1)
  • select Ciphers
  • select KexAlgorithms
  • select MACs
  • use -o -a $rounds for ssh-keygen

Use ssh -v to enable only algorithms supported by Github.
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dolmen commented Jan 7, 2015

Also, change the default $key_type and $key_bits.

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dolmen commented Feb 11, 2015

Extract of ssh -vv [email protected]:

debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug2: kex_parse_kexinit: [email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: [email protected],[email protected],[email protected],[email protected],ssh-rsa,ssh-dss,[email protected],[email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,[email protected],[email protected],[email protected],aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected]
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,[email protected],[email protected],[email protected],aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected]
debug2: kex_parse_kexinit: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-md5,hmac-sha1,[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-md5,hmac-sha1,[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,[email protected],zlib
debug2: kex_parse_kexinit: none,[email protected],zlib
debug2: kex_parse_kexinit: 
debug2: kex_parse_kexinit: 
debug2: kex_parse_kexinit: first_kex_follows 0 
debug2: kex_parse_kexinit: reserved 0 
debug2: kex_parse_kexinit: ecdh-sha2-nistp256,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-dss,ssh-rsa
debug2: kex_parse_kexinit: aes256-ctr,aes192-ctr,aes128-ctr,aes256-cbc,aes192-cbc,aes128-cbc,blowfish-cbc,3des-cbc,des-cbc-ssh1
debug2: kex_parse_kexinit: aes256-ctr,aes192-ctr,aes128-ctr,aes256-cbc,aes192-cbc,aes128-cbc,blowfish-cbc,3des-cbc,des-cbc-ssh1
debug2: kex_parse_kexinit: hmac-sha1,hmac-sha2-256,hmac-sha2-512
debug2: kex_parse_kexinit: hmac-sha1,hmac-sha2-256,hmac-sha2-512
debug2: kex_parse_kexinit: none,zlib,[email protected]
debug2: kex_parse_kexinit: none,zlib,[email protected]
debug2: kex_parse_kexinit: 
debug2: kex_parse_kexinit: 
debug2: kex_parse_kexinit: first_kex_follows 0 
debug2: kex_parse_kexinit: reserved 0 
debug2: mac_setup: setup hmac-sha1
debug1: kex: server->client aes128-ctr hmac-sha1 none
debug2: mac_setup: setup hmac-sha1
debug1: kex: client->server aes128-ctr hmac-sha1 none
debug1: sending SSH2_MSG_KEX_ECDH_INIT
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY

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dolmen commented Feb 12, 2015

Algorithms selection implemented in f12b1f5.

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dolmen commented Feb 12, 2015

After the change: ssh -v dolmen.github.com

debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes256-ctr hmac-sha2-512 none
debug1: kex: client->server aes256-ctr hmac-sha2-512 none

So we now use aes256-ctr instead of aes128-ctr, and hmac-sha2-512 instead of hmac-sha1.

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dolmen commented Apr 3, 2015

Related: https://plus.google.com/+ArjanvandeVen/posts/VAK1SRHjTZm
Also, check openssl ciphers -v and openssl list-cipher-algorithms.

@dolmen dolmen self-assigned this Apr 3, 2015
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dolmen commented Nov 24, 2015

2015-11-24:

debug1: kex: server->client [email protected] <implicit> none
debug1: kex: client->server [email protected] <implicit> none

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