[Dovecot] ssl_cipher_list

[Robert Allerstorfer]

Hi,

I have noticed the 'ssl_cipher_list' directive in the 1.0-test
snapshots which is not in 0.99. It's default value seems to be
"all:!low". However, this would not be compatible with openssl's
cipher listing format. Thus, I would vote to change it's format to be
openssl compatible. To be compatible, it has to be changed to
"ALL:!LOW" (just upercased in this case). IMO, this would be helpful
because executing

openssl ciphers -v 'all:!low'

would not return any cipher, but

openssl ciphers -v 'ALL:!LOW'

would return the expected cipher list such as

ADH-AES256-SHA          SSLv3 Kx=DH       Au=None Enc=AES(256)  Mac=SHA1
DHE-RSA-AES256-SHA      SSLv3 Kx=DH       Au=RSA  Enc=AES(256)  Mac=SHA1
DHE-DSS-AES256-SHA      SSLv3 Kx=DH       Au=DSS  Enc=AES(256)  Mac=SHA1
AES256-SHA              SSLv3 Kx=RSA      Au=RSA  Enc=AES(256)  Mac=SHA1
ADH-AES128-SHA          SSLv3 Kx=DH       Au=None Enc=AES(128)  Mac=SHA1
DHE-RSA-AES128-SHA      SSLv3 Kx=DH       Au=RSA  Enc=AES(128)  Mac=SHA1
DHE-DSS-AES128-SHA      SSLv3 Kx=DH       Au=DSS  Enc=AES(128)  Mac=SHA1
AES128-SHA              SSLv3 Kx=RSA      Au=RSA  Enc=AES(128)  Mac=SHA1
DHE-DSS-RC4-SHA         SSLv3 Kx=DH       Au=DSS  Enc=RC4(128)  Mac=SHA1
EXP1024-DHE-DSS-RC4-SHA SSLv3 Kx=DH(1024) Au=DSS  Enc=RC4(56)   Mac=SHA1 export
EXP1024-RC4-SHA         SSLv3 Kx=RSA(1024) Au=RSA  Enc=RC4(56)   Mac=SHA1 export
EXP1024-DHE-DSS-DES-CBC-SHA SSLv3 Kx=DH(1024) Au=DSS  Enc=DES(56)   Mac=SHA1 export
EXP1024-DES-CBC-SHA     SSLv3 Kx=RSA(1024) Au=RSA  Enc=DES(56)   Mac=SHA1 export
EXP1024-RC2-CBC-MD5     SSLv3 Kx=RSA(1024) Au=RSA  Enc=RC2(56)   Mac=MD5  export
EXP1024-RC4-MD5         SSLv3 Kx=RSA(1024) Au=RSA  Enc=RC4(56)   Mac=MD5  export
EXP-KRB5-RC4-MD5        SSLv3 Kx=KRB5     Au=KRB5 Enc=RC4(40)   Mac=MD5  export
EXP-KRB5-RC2-CBC-MD5    SSLv3 Kx=KRB5     Au=KRB5 Enc=RC2(40)   Mac=MD5  export
EXP-KRB5-DES-CBC-MD5    SSLv3 Kx=KRB5     Au=KRB5 Enc=DES(40)   Mac=MD5  export
EXP-KRB5-RC4-SHA        SSLv3 Kx=KRB5     Au=KRB5 Enc=RC4(40)   Mac=SHA1 export
EXP-KRB5-RC2-CBC-SHA    SSLv3 Kx=KRB5     Au=KRB5 Enc=RC2(40)   Mac=SHA1 export
EXP-KRB5-DES-CBC-SHA    SSLv3 Kx=KRB5     Au=KRB5 Enc=DES(40)   Mac=SHA1 export
KRB5-RC4-MD5            SSLv3 Kx=KRB5     Au=KRB5 Enc=RC4(128)  Mac=MD5 
KRB5-DES-CBC3-MD5       SSLv3 Kx=KRB5     Au=KRB5 Enc=3DES(168) Mac=MD5 
KRB5-RC4-SHA            SSLv3 Kx=KRB5     Au=KRB5 Enc=RC4(128)  Mac=SHA1
KRB5-DES-CBC3-SHA       SSLv3 Kx=KRB5     Au=KRB5 Enc=3DES(168) Mac=SHA1
EDH-RSA-DES-CBC3-SHA    SSLv3 Kx=DH       Au=RSA  Enc=3DES(168) Mac=SHA1
EXP-EDH-RSA-DES-CBC-SHA SSLv3 Kx=DH(512)  Au=RSA  Enc=DES(40)   Mac=SHA1 export
EDH-DSS-DES-CBC3-SHA    SSLv3 Kx=DH       Au=DSS  Enc=3DES(168) Mac=SHA1
EXP-EDH-DSS-DES-CBC-SHA SSLv3 Kx=DH(512)  Au=DSS  Enc=DES(40)   Mac=SHA1 export
DES-CBC3-SHA            SSLv3 Kx=RSA      Au=RSA  Enc=3DES(168) Mac=SHA1
EXP-DES-CBC-SHA         SSLv3 Kx=RSA(512) Au=RSA  Enc=DES(40)   Mac=SHA1 export
EXP-RC2-CBC-MD5         SSLv3 Kx=RSA(512) Au=RSA  Enc=RC2(40)   Mac=MD5  export
RC4-SHA                 SSLv3 Kx=RSA      Au=RSA  Enc=RC4(128)  Mac=SHA1
RC4-MD5                 SSLv3 Kx=RSA      Au=RSA  Enc=RC4(128)  Mac=MD5 
EXP-RC4-MD5             SSLv3 Kx=RSA(512) Au=RSA  Enc=RC4(40)   Mac=MD5  export
ADH-DES-CBC3-SHA        SSLv3 Kx=DH       Au=None Enc=3DES(168) Mac=SHA1
EXP-ADH-DES-CBC-SHA     SSLv3 Kx=DH(512)  Au=None Enc=DES(40)   Mac=SHA1 export
ADH-RC4-MD5             SSLv3 Kx=DH       Au=None Enc=RC4(128)  Mac=MD5 
EXP-ADH-RC4-MD5         SSLv3 Kx=DH(512)  Au=None Enc=RC4(40)   Mac=MD5  export
DES-CBC3-MD5            SSLv2 Kx=RSA      Au=RSA  Enc=3DES(168) Mac=MD5 
RC2-CBC-MD5             SSLv2 Kx=RSA      Au=RSA  Enc=RC2(128)  Mac=MD5 
EXP-RC2-CBC-MD5         SSLv2 Kx=RSA(512) Au=RSA  Enc=RC2(40)   Mac=MD5  export
RC4-MD5                 SSLv2 Kx=RSA      Au=RSA  Enc=RC4(128)  Mac=MD5 
EXP-RC4-MD5             SSLv2 Kx=RSA(512) Au=RSA  Enc=RC4(40)   Mac=MD5  export

I want dovecot to only accept high encrypted ciphers, thus it should
support

ssl_cipher_list = ALL:!ADH!LOW:!SSLv2:!EXP:+HIGH:+MEDIUM

corresponding to a openssl list such as

DHE-RSA-AES256-SHA      SSLv3 Kx=DH       Au=RSA  Enc=AES(256)  Mac=SHA1
DHE-DSS-AES256-SHA      SSLv3 Kx=DH       Au=DSS  Enc=AES(256)  Mac=SHA1
AES256-SHA              SSLv3 Kx=RSA      Au=RSA  Enc=AES(256)  Mac=SHA1
KRB5-DES-CBC3-MD5       SSLv3 Kx=KRB5     Au=KRB5 Enc=3DES(168) Mac=MD5 
KRB5-DES-CBC3-SHA       SSLv3 Kx=KRB5     Au=KRB5 Enc=3DES(168) Mac=SHA1
EDH-RSA-DES-CBC3-SHA    SSLv3 Kx=DH       Au=RSA  Enc=3DES(168) Mac=SHA1
EDH-DSS-DES-CBC3-SHA    SSLv3 Kx=DH       Au=DSS  Enc=3DES(168) Mac=SHA1
DES-CBC3-SHA            SSLv3 Kx=RSA      Au=RSA  Enc=3DES(168) Mac=SHA1
DHE-RSA-AES128-SHA      SSLv3 Kx=DH       Au=RSA  Enc=AES(128)  Mac=SHA1
DHE-DSS-AES128-SHA      SSLv3 Kx=DH       Au=DSS  Enc=AES(128)  Mac=SHA1
AES128-SHA              SSLv3 Kx=RSA      Au=RSA  Enc=AES(128)  Mac=SHA1
DHE-DSS-RC4-SHA         SSLv3 Kx=DH       Au=DSS  Enc=RC4(128)  Mac=SHA1
KRB5-RC4-MD5            SSLv3 Kx=KRB5     Au=KRB5 Enc=RC4(128)  Mac=MD5 
KRB5-RC4-SHA            SSLv3 Kx=KRB5     Au=KRB5 Enc=RC4(128)  Mac=SHA1
RC4-SHA                 SSLv3 Kx=RSA      Au=RSA  Enc=RC4(128)  Mac=SHA1
RC4-MD5                 SSLv3 Kx=RSA      Au=RSA  Enc=RC4(128)  Mac=MD5

This would really make "Dovecot (...) written with security primarily
in mind"

Thanks for consideration!
rob.