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Odi's astoundingly incomplete notes

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Configure forward secrecy

Chosing you SSL cipher suites is one thing. But configuring various services is  another.

Please note that the following algorithms are considered completely broken nowadays: RC4, MD5, 3DES.

OpenLDAP: /etc/openssl/slapd.conf:
TLSCipherSuite EDH+CAMELLIA:EDH+aRSA:EECDH+aRSA+AESGCM:EECDH+aRSA+SHA384:EECDH+aRSA+SHA256:EECDH:+CAMELLIA256:+AES256:+CAMELLIA128:+AES128:+SSLv3:!aNULL:!eNULL:!LOW:!3DES:!MD5:!EXP:!PSK:!SRP:!DSS:!RC4:!SEED:!ECDSA:CAMELLIA256-SHA:AES256-SHA:CAMELLIA128-SHA:AES128-SHA
TLSProtocolMin 3.1
Apache httpd:
SSLCipherSuite EDH+CAMELLIA:EDH+aRSA:EECDH+aRSA+AESGCM:EECDH+aRSA+SHA384:EECDH+aRSA+SHA256:EECDH:+CAMELLIA256:+AES256:+CAMELLIA128:+AES128:+SSLv3:!aNULL:!eNULL:!LOW:!3DES:!MD5:!EXP:!PSK:!SRP:!DSS:!RC4:!SEED:!ECDSA:CAMELLIA256-SHA:AES256-SHA:CAMELLIA128-SHA:AES128-SHA
SSLProtocol all -SSLv2 -SSLv3
Courier-Imap: /etc/courier-imap/imapd-ssl
TLS_CIPHER_LIST="EDH+CAMELLIA:EDH+aRSA:EECDH+aRSA+AESGCM:EECDH+aRSA+SHA384:EECDH+aRSA+SHA256:EECDH:+CAMELLIA256:+AES256:+CAMELLIA128:+AES128:+SSLv3:!aNULL:!eNULL:!LOW:!3DES:!MD5:!EXP:!PSK:!SRP:!DSS:!RC4:!SEED:!ECDSA:CAMELLIA256-SHA:AES256-SHA:CAMELLIA128-SHA:AES128-SHA"
TLS_PROTOCOL=TLSv1.2

OpenSSH server: /etc/ssh/sshd_config
Protocol 2
Ciphers aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes128-ctr
MACs umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,hmac-ripemd160
OpenSSH client: /etc/ssh/ssh_config:
Ciphers aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes128-ctr
MACs umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,hmac-ripemd160
Postfix: important only for mandatory TLS, as there is no end-to-end encryption in SMTP anyway. Email to/from your local system may go through many hops that are not under your control. Also there is no authentication between those hosts, so even TLS doesn't protect against man-in-the-middle attacks here (key agreement protocols don't solve that problem).
/etc/postfix/main.cf:
smtpd_tls_eecdh_grade=ultra
smtpd_tls_mandatory_ciphers=high
tls_high_cipherlist=EDH+CAMELLIA:EDH+aRSA:EECDH+aRSA+AESGCM:EECDH+aRSA+SHA384:EECDH+aRSA+SHA256:EECDH:+CAMELLIA256:+AES256:+CAMELLIA128:+AES128:+SSLv3:!aNULL:!eNULL:!LOW:!3DES:!MD5:!EXP:!PSK:!SRP:!DSS:!RC4:!SEED:!ECDSA:CAMELLIA256-SHA:AES256-SHA:CAMELLIA128-SHA:AES128-SHA
smtpd_tls_protocols = !SSLv2, !SSLv3
smtp_tls_mandatory_protocols = !SSLv2, !SSLv3
Openswan:
For protostack=netkey make sure to enable all relevant crypto algorithms in your kernel, for all crypto is done by the kernel and Openswan can only configure what's supported.
To get a list of supported algorithms: ipsec auto --status | less
000 algorithm ESP encrypt: id=2, name=ESP_DES, ivlen=8, keysizemin=64, keysizemax=64
000 algorithm ESP encrypt: id=3, name=ESP_3DES, ivlen=8, keysizemin=192, keysizemax=192
000 algorithm ESP encrypt: id=11, name=ESP_NULL, ivlen=0, keysizemin=0, keysizemax=0
000 algorithm ESP encrypt: id=12, name=ESP_AES, ivlen=8, keysizemin=128, keysizemax=256
000 algorithm ESP encrypt: id=13, name=ESP_AES_CTR, ivlen=8, keysizemin=160, keysizemax=288
000 algorithm ESP encrypt: id=14, name=ESP_AES_CCM_A, ivlen=8, keysizemin=128, keysizemax=256
000 algorithm ESP encrypt: id=15, name=ESP_AES_CCM_B, ivlen=8, keysizemin=128, keysizemax=256
000 algorithm ESP encrypt: id=16, name=ESP_AES_CCM_C, ivlen=8, keysizemin=128, keysizemax=256
000 algorithm ESP encrypt: id=18, name=ESP_AES_GCM_A, ivlen=8, keysizemin=160, keysizemax=288
000 algorithm ESP encrypt: id=19, name=ESP_AES_GCM_B, ivlen=12, keysizemin=160, keysizemax=288
000 algorithm ESP encrypt: id=20, name=ESP_AES_GCM_C, ivlen=16, keysizemin=160, keysizemax=288
000 algorithm ESP encrypt: id=22, name=ESP_CAMELLIA, ivlen=8, keysizemin=128, keysizemax=256
000 algorithm ESP auth attr: id=1, name=AUTH_ALGORITHM_HMAC_MD5, keysizemin=128, keysizemax=128
000 algorithm ESP auth attr: id=2, name=AUTH_ALGORITHM_HMAC_SHA1, keysizemin=160, keysizemax=160
000 algorithm ESP auth attr: id=5, name=AUTH_ALGORITHM_HMAC_SHA2_256, keysizemin=256, keysizemax=256
000 algorithm ESP auth attr: id=6, name=AUTH_ALGORITHM_HMAC_SHA2_384, keysizemin=384, keysizemax=384
000 algorithm ESP auth attr: id=7, name=AUTH_ALGORITHM_HMAC_SHA2_512, keysizemin=512, keysizemax=512
000 algorithm ESP auth attr: id=9, name=AUTH_ALGORITHM_AES_CBC, keysizemin=128, keysizemax=128
000 algorithm ESP auth attr: id=251, name=AUTH_ALGORITHM_NULL_KAME, keysizemin=0, keysizemax=0
000
000 algorithm IKE encrypt: id=0, name=(null), blocksize=16, keydeflen=131
000 algorithm IKE encrypt: id=1, name=OAKLEY_DES_CBC, blocksize=8, keydeflen=64
000 algorithm IKE encrypt: id=3, name=OAKLEY_BLOWFISH_CBC, blocksize=8, keydeflen=128
000 algorithm IKE encrypt: id=5, name=OAKLEY_3DES_CBC, blocksize=8, keydeflen=192
000 algorithm IKE encrypt: id=7, name=OAKLEY_AES_CBC, blocksize=16, keydeflen=128
000 algorithm IKE encrypt: id=65004, name=OAKLEY_SERPENT_CBC, blocksize=16, keydeflen=128
000 algorithm IKE encrypt: id=65005, name=OAKLEY_TWOFISH_CBC, blocksize=16, keydeflen=128
000 algorithm IKE encrypt: id=65289, name=OAKLEY_TWOFISH_CBC_SSH, blocksize=16, keydeflen=128
000 algorithm IKE hash: id=1, name=OAKLEY_MD5, hashsize=16
000 algorithm IKE hash: id=2, name=OAKLEY_SHA1, hashsize=20
000 algorithm IKE hash: id=4, name=OAKLEY_SHA2_256, hashsize=32
000 algorithm IKE hash: id=6, name=OAKLEY_SHA2_512, hashsize=64
000 algorithm IKE dh group: id=1, name=OAKLEY_GROUP_MODP768, bits=768
000 algorithm IKE dh group: id=2, name=OAKLEY_GROUP_MODP1024, bits=1024
000 algorithm IKE dh group: id=5, name=OAKLEY_GROUP_MODP1536, bits=1536
000 algorithm IKE dh group: id=14, name=OAKLEY_GROUP_MODP2048, bits=2048
000 algorithm IKE dh group: id=15, name=OAKLEY_GROUP_MODP3072, bits=3072
000 algorithm IKE dh group: id=16, name=OAKLEY_GROUP_MODP4096, bits=4096
000 algorithm IKE dh group: id=17, name=OAKLEY_GROUP_MODP6144, bits=6144
000 algorithm IKE dh group: id=18, name=OAKLEY_GROUP_MODP8192, bits=8192
000 algorithm IKE dh group: id=22, name=OAKLEY_GROUP_DH22, bits=1024
000 algorithm IKE dh group: id=23, name=OAKLEY_GROUP_DH23, bits=2048
000 algorithm IKE dh group: id=24, name=OAKLEY_GROUP_DH24, bits=2048

The algorithms are configured like so (Openswan documentation is very incomplete!):
        # PHASE 1
        # negothiation mode
        aggrmode=no
        ike=aes-sha2_256;modp2048
        # PHASE 2
        type=tunnel
        phase2=esp
        phase2alg=aes_gcm_c-256-sha2_256;modp2048
        salifetime=8h
        pfs=yes
        auto=ignore
The lenth of the PSKs in /etc/ipsec.secrets is very relevant. The minimum safe size depends on IKE hash, but you can always choose longer keys of course:
posted on 2013-11-25 12:25 CET in Code | 0 comments | permalink