Asa

while I already mentioned couple of times on this blog, that handling dynamic routing on firewall is asking yourself for unexpected problems, sometimes it’s needed. as Cisco, we don’t normally recommend using ASA or FTD boxes as full table BGP routers. not because they can’t be used in this role, but because we don’t believe it’s a good networking and security practice. here’s example from my home lab testing lab cluster of two ASA 5516-X, running 9.13(1) and getting full BGP feed from my upstream ASR 1001-X router: ...

somewhere around 2013 (and precisely - for ‘small’ Santa Claus, so 6th of December), OpenSSH was extended to provide new way of storing keys. it’s important because the old format - MD5 hash - can be cracked veeeeery quickly. developers decide to use modification of bcrypt, that will slow down GPU-assisted cracking attempts in hashcat from gigahashes per second, to at most kilohashes. what you need to do to upgrade your defenses? first of all, take care of the keys themselves. i’m using 2048 bit long RSA keys, and because some of the older equipment can’t handle more, i have to stay with that. my private key looks like this today: ...

OpenSSH 7 among other things discontinued older key exchange protocols for Diffie-Hellmans group 1 (diffie-hellman-group1-sha1). we already know that it can be compromised by executing attack known as Logjam. that’s all good and nice, until you try to connect to such device using newly upgraded SSH. if your device doesn’t support DH group 1 key exchange, you need to upgrade software. if you already have software capable of doing so, it needs to be configured on the box. ...

it’s subject old as world (password-protected world, that is). i had to do some of cleanup on my devices and i hit a problem with 4096 bit keys. so, just as a reference that may be helpful somewhere for someone - you import keys to Cisco IOS without any special problems: router#conf t Enter configuration commands, one per line. End with CNTL/Z. router(config)#ip ssh pubkey-chain router(conf-ssh-pubkey)#username TEST router(conf-ssh-pubkey-user)#key-string router(conf-ssh-pubkey-data)#AAAAB3NzaC1yc2EAAAADAQABAAACAQDCiLBaopUwsFb9YJNhGqVYqBajlrH S/zwD6/yR6N8VcRzrpqMMNCFXe1q5GMGM[...]ANWInd9GHBjTzbJWVwavxy1ooQewii8ErofZuv1l/SXSdXLzfL p0zMoZ0L+BNPS0j4XBS0N3t8Vl8oVixqIeG2BNTCNaDDt6hx2Q== lukasz@bromirski.net router(conf-ssh-pubkey-user)#exit router(conf-ssh-pubkey)#exit for Cisco ASA, keys that are longer than 2048 bits need to be prepared using pkf format, as command line has limit of 512 bytes. so, to move key in OpenSSH compliant format like this one: ...

…supports BGP and it’s already out. do you like BGP on your firewalls? i don’t. should we have the tool in hand, just in case? well, sometimes it’s handy. but going back again - do you like BGP on your firewalls? ;)