Add note regarding OpenSSH's 2048-bit GEX fallback, and suppress the related recommendation since the user cannot control it (partly related to #168).

This commit is contained in:
Joe Testa
2023-03-21 11:44:45 -04:00
parent c02ab8f170
commit 71feaa191e
4 changed files with 35 additions and 8 deletions

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@ -21,6 +21,7 @@
`- [info] available since OpenSSH 5.7, Dropbear SSH 2013.62
(kex) diffie-hellman-group-exchange-sha256 (2048-bit) -- [warn] 2048-bit modulus only provides 112-bits of symmetric strength
`- [info] available since OpenSSH 4.4
`- [info] A bug in OpenSSH causes it to fall back to a 2048-bit modulus regardless of server configuration (https://bugzilla.mindrot.org/show_bug.cgi?id=2793)
(kex) diffie-hellman-group16-sha512 -- [info] available since OpenSSH 7.3, Dropbear SSH 2016.73
(kex) diffie-hellman-group18-sha512 -- [info] available since OpenSSH 7.3
(kex) diffie-hellman-group14-sha256 -- [warn] 2048-bit modulus only provides 112-bits of symmetric strength
@ -75,7 +76,6 @@
(fin) ssh-rsa: SHA256:nsWtdJ9Z67Vrf7OsUzQov7esXhsWAfVppArGh25u244
# algorithm recommendations (for OpenSSH 8.0)
(rec) !diffie-hellman-group-exchange-sha256 -- kex algorithm to change (increase modulus size to 3072 bits or larger) 
(rec) -ecdh-sha2-nistp256 -- kex algorithm to remove 
(rec) -ecdh-sha2-nistp384 -- kex algorithm to remove 
(rec) -ecdh-sha2-nistp521 -- kex algorithm to remove 

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@ -21,6 +21,7 @@
`- [info] available since OpenSSH 5.7, Dropbear SSH 2013.62
(kex) diffie-hellman-group-exchange-sha256 (2048-bit) -- [warn] 2048-bit modulus only provides 112-bits of symmetric strength
`- [info] available since OpenSSH 4.4
`- [info] A bug in OpenSSH causes it to fall back to a 2048-bit modulus regardless of server configuration (https://bugzilla.mindrot.org/show_bug.cgi?id=2793)
(kex) diffie-hellman-group16-sha512 -- [info] available since OpenSSH 7.3, Dropbear SSH 2016.73
(kex) diffie-hellman-group18-sha512 -- [info] available since OpenSSH 7.3
(kex) diffie-hellman-group14-sha256 -- [warn] 2048-bit modulus only provides 112-bits of symmetric strength
@ -67,7 +68,6 @@
(fin) ssh-ed25519: SHA256:UrnXIVH+7dlw8UqYocl48yUEcKrthGDQG2CPCgp7MxU
# algorithm recommendations (for OpenSSH 8.0)
(rec) !diffie-hellman-group-exchange-sha256 -- kex algorithm to change (increase modulus size to 3072 bits or larger) 
(rec) -ecdh-sha2-nistp256 -- kex algorithm to remove 
(rec) -ecdh-sha2-nistp384 -- kex algorithm to remove 
(rec) -ecdh-sha2-nistp521 -- kex algorithm to remove 

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@ -15,6 +15,7 @@
(kex) curve25519-sha256@libssh.org -- [info] available since OpenSSH 6.5, Dropbear SSH 2013.62
(kex) diffie-hellman-group-exchange-sha256 (2048-bit) -- [warn] 2048-bit modulus only provides 112-bits of symmetric strength
`- [info] available since OpenSSH 4.4
`- [info] A bug in OpenSSH causes it to fall back to a 2048-bit modulus regardless of server configuration (https://bugzilla.mindrot.org/show_bug.cgi?id=2793)
# host-key algorithms
(key) ssh-ed25519 -- [info] available since OpenSSH 6.5
@ -37,12 +38,8 @@
(fin) ssh-ed25519: SHA256:UrnXIVH+7dlw8UqYocl48yUEcKrthGDQG2CPCgp7MxU
# algorithm recommendations (for OpenSSH 8.0)
(rec) !diffie-hellman-group-exchange-sha256 -- kex algorithm to change (increase modulus size to 3072 bits or larger) 
(rec) +diffie-hellman-group16-sha512 -- kex algorithm to append 
(rec) +diffie-hellman-group18-sha512 -- kex algorithm to append 
(rec) +rsa-sha2-256 -- key algorithm to append 
(rec) +rsa-sha2-512 -- key algorithm to append 
# additional info
(nfo) For hardening guides on common OSes, please see: <https://www.ssh-audit.com/hardening_guides.html>