Esta é uma repostagem da minha pergunta original (OpenVPN não consegue estabelecer conexão com nenhuma cifra TLS 1.2) O problema está dividido em dois porque foi encontrada uma solução para os conjuntos de criptografia de 128 bits.
O OpenVPN não consegue se conectar com estes conjuntos de criptografia:
TLS-DHE-RSA-WITH-AES-256-GCM-SHA384
TLS-DHE-RSA-WITH-AES-256-CBC-SHA256
Gostaria de saber se mais alguém está usando isso com sucesso.
Eu executo a versão atual2.3.6, compilado da fonte.
Tentei com várias distros Linux e clientes Windows.
De acordo com o wiki as cifras deveriam estar funcionando: https://community.openvpn.net/openvpn/wiki/Hardening#Useof--tls-cipher
Erro do cliente:
[... Desktop]$ sudo openvpn home.ovpn
Sat Jan 24 15:18:28 2015 OpenVPN 2.3.6 x86_64-unknown-linux-gnu [SSL (OpenSSL)] [LZO] [EPOLL] [MH] [IPv6] built on Jan 24 2015
Sat Jan 24 15:18:28 2015 library versions: OpenSSL 1.0.1l 15 Jan 2015, LZO 2.08
Sat Jan 24 15:18:28 2015 WARNING: file 'home/client1.key' is group or others accessible
Sat Jan 24 15:18:28 2015 WARNING: file 'home/ta.key' is group or others accessible
Sat Jan 24 15:18:28 2015 Control Channel Authentication: using 'home/ta.key' as a OpenVPN static key file
Sat Jan 24 15:18:28 2015 Outgoing Control Channel Authentication: Using 256 bit message hash 'SHA256' for HMAC authentication
Sat Jan 24 15:18:28 2015 Incoming Control Channel Authentication: Using 256 bit message hash 'SHA256' for HMAC authentication
Sat Jan 24 15:18:28 2015 Attempting to establish TCP connection with [AF_INET]192.168.1.67:1194 [nonblock]
Sat Jan 24 15:18:29 2015 TCP connection established with [AF_INET]192.168.1.67:1194
Sat Jan 24 15:18:29 2015 TCPv4_CLIENT link local: [undef]
Sat Jan 24 15:18:29 2015 TCPv4_CLIENT link remote: [AF_INET]192.168.1.67:1194
Sat Jan 24 15:18:29 2015 TLS_ERROR: BIO read tls_read_plaintext error: error:140830B5:SSL routines:SSL3_CLIENT_HELLO:no ciphers available
Sat Jan 24 15:18:29 2015 TLS Error: TLS object -> incoming plaintext read error
Sat Jan 24 15:18:29 2015 TLS Error: TLS handshake failed
Sat Jan 24 15:18:29 2015 Fatal TLS error (check_tls_errors_co), restarting
Sat Jan 24 15:18:29 2015 SIGUSR1[soft,tls-error] received, process restarting
Sat Jan 24 15:18:30 2015 SIGINT[hard,init_instance] received, process exiting
Responder1
Sim, isso deve funcionar e funciona para mim:
$ openvpn --config loopback-client --tls-cipher TLS-DHE-RSA-WITH-AES-256-GCM-SHA384 --tls-version-min 1.0
Thu Jan 29 00:13:13 2015 OpenVPN 2.3.6 x86_64-unknown-linux-gnu [SSL (OpenSSL)] [LZO] [EPOLL] [PKCS11] [MH] [IPv6] built on Dec 16 2014
Thu Jan 29 00:13:13 2015 library versions: OpenSSL 1.0.1f 6 Jan 2014, LZO 2.06
[...]
Thu Jan 29 00:13:13 2015 Control Channel: TLSv1.2, cipher TLSv1/SSLv3 DHE-RSA-AES256-GCM-SHA384, 2048 bit RSA
Thu Jan 29 00:13:13 2015 [Test-Server] Peer Connection Initiated with [AF_INET]127.0.0.1:16000
Thu Jan 29 00:13:14 2015 Initialization Sequence Completed
Isso está usando os arquivos de configuração padrão do loopback-server e do loopback-client fornecidos com o openvpn. Certifique-se de adicionar tls-version-min 1.0(ou 1.2, se quiser impor isso) às configurações em ambas as extremidades. Fora isso, não fiz nada de especial.
O problema é especificamente o AES-256? Ou seja, você obtém o mesmo comportamento com TLS-DHE-RSA-WITH-AES-128-CBC-SHA vs TLS-DHE-RSA-WITH-AES-256-CBC-SHA?