01 Giu 11 Openssl e ciphers… questi sconosciuti
La suite openssl supporta differenti meccanismi di crittografia asimmetrica.
Il client e il server negoziano in fase di handshake la modalita’ di cifratura che utilizzeranno per il trasferimento sicuro dei dati.
In openssl le ciphers implementano 4 algoritmi:
1) Key Exchange Algorithm (scambio delle chiavi)
Sono RSA o Diffie-Hellman
2) Authentication Algorithm (autenticazione dei sistemi)
RSA, Diffie-Hellman, DSS o nessuno
3) Cipher/Encryption Algorithm (cifratura dello stream di dati)
DES, Triple-DES, RC4, RC2, IDEA o nessuno
4) MAC Digest Algorithm (verifica della validita’ del pacchetto)
MD5, SHA o SHA1
Il comando “openssl s_client -ciphers <parametro cipher>” permette di forzare il client (in questo caso il comando openssl stesso) ad utilizzare i meccanismi di cifratura piu’ deboli (parametro LOW), medi (MEDIUM) o piu’ sicuri (HIGH). Tuttavia per poter colloquiare in modo corretto, anche il server SSL deve supportare tali modalita’.
La suite openssl presente al momento sul mio pc (0.9.8k) implementa le seguenti ciphers:
LOW (tutti hanno chiave di cifratura inferiore a 128 bit, e firma hash SHA1 o MD5):
ADH-DES-CBC-SHA SSLv3 Kx=DH Au=None Enc=DES(56) Mac=SHA1
EDH-RSA-DES-CBC-SHA SSLv3 Kx=DH Au=RSA Enc=DES(56) Mac=SHA1
EDH-DSS-DES-CBC-SHA SSLv3 Kx=DH Au=DSS Enc=DES(56) Mac=SHA1
DES-CBC-SHA SSLv3 Kx=RSA Au=RSA Enc=DES(56) Mac=SHA1
DES-CBC-MD5 SSLv2 Kx=RSA Au=RSA Enc=DES(56) Mac=MD5
MEDIUM (tutti hanno chiave di cifratura uguale a 128 bit, e firma hash SHA1 o MD5):
ADH-RC4-MD5 SSLv3 Kx=DH Au=None Enc=RC4(128) Mac=MD5
RC4-SHA SSLv3 Kx=RSA Au=RSA Enc=RC4(128) Mac=SHA1
RC4-MD5 SSLv3 Kx=RSA Au=RSA Enc=RC4(128) Mac=MD5
RC2-CBC-MD5 SSLv2 Kx=RSA Au=RSA Enc=RC2(128) Mac=MD5
RC4-MD5 SSLv2 Kx=RSA Au=RSA Enc=RC4(128) Mac=MD5
HIGH (tutti hanno chiave di cifratura superiore o uguale a 128 bit, e firma hash SHA1 o MD5):
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
ADH-DES-CBC3-SHA SSLv3 Kx=DH Au=None 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
DES-CBC3-MD5 SSLv2 Kx=RSA Au=RSA Enc=3DES(168) Mac=MD5
e altre modalita’ che non fanno capo ai tre alias descritti (LOW, MEDIUM e HIGH).
Per quanto riguarda la parte SERVER (per i bravi che usano APACHE) e’ possibile impostare le ciphers supportate tramite l’utilizzo del parametro SSLCipherSuite, ad esempio mettendo qualcosa del genere:
SSLCipherSuite +HIGH:+MEDIUM:!LOW:+SSLv2
Sempre parlando di apache, se non specificato, il default e’: SSLCipherSuite ALL:!ADH:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP
ovvero si cerca di mantenere la compatibilita’ con i client piu’ vecchi e che quindi supporano solo ciphers poco robuste.
Scusate la “lezione di crittografia” ma secondo me serve per fare un po’ di chiarezza generale sull’argomento, spesso un po’ oscuro a molti.
Ciao, Dino.
08 Feb 11 NuvolaBase.com, the OrientDB on the Cloud
So this is finally there. NuvolaBase.com (alpha release) has been published yesterday at UIM-GDB in Barcelona by Luca Garulli, the OrientDB author.
I am really excited as TuxWeb cofounder for joining our technical collaboration with him for the alpha realization of this project.
I personally cover all the system administration and low level stuff.
– dAm2K!!
24 Ago 10 Why do not host sites from your own home
I would not recommend you to host sites that way, you have to be sure that your ISP give you public IP(s) and setup your router to port forward ports 80, 443, 53, and so on.
There are other problems too:
1) if you want to host more than one site with SSL you must have one public IP for each SSL site or use different SSL ports for each site, because name virtualhosting with SSL is not possible;
2) dsl lines are not designed to be stable. The connection can go down and make your site not visible. This is a major problem if you make the mistake to have your own DNS server on it!! The ISP assigned public IP address can change more than one time a day and you have to sync the DNS zone each time.
3) dsl ips are putted into DNS based blacklists zones. You may not be reached from various HTTP proxy servers around the world. For the same reason you cannot send mails, for example originated from your sites.
4) adsl lines are asymmetric (unbalanced for download). You have few kbytes per second in upload, that is just what you need to publish web sites, so this can be a problem when you have just more than 3 users.
5) you probably have problems with High-Availability and Load-Balancing on domestic hardware and you may have blackouts.
6) DNS subsystem may need primary and secondary DNS servers.
The best way (imho) is to use services like slicehost where you have a HA virtual server slice running linux, public IP addresses, free primary and secondary DNS hosting service, large public bandwidth, disk space… and not last your own root password that you can use to have maintenance on your own server for your own.
https://manage.slicehost.com/customers/new?referrer=af57db3020e04bb27352e271753a7a18
26 Mar 10 Il tuo server linux personale
Se quello che hai sempre cercato e’ avere il tuo personalissimo server linux up and running 24 ore su 24, SliceHost e’ l’opzione giusta per te.
Questa meravigliosa azienda americana (in Italia purtroppo certe cose ce le sogniamo alla grande!) ha sviluppato un sistema automatico con interfaccia web in grado di fornirti in tempo reale per pochi dollari al mese una tua personalissima macchina virtuale con cui potrai realizzare e gestire il tuo server linux in tutta tranquillita’.
Banda e connettivita’ internazionale a internet non sono un problema e potrai scegliere tra vari tagli di offerte pronte per te.
Se sei interessato, dai un’occhiata al sito https://manage.slicehost.com/customers/new?referrer=af57db3020e04bb27352e271753a7a18 e affiliati anche tu.
Avrai la possibilita’ di scegliere la distribuzione linux che piu’ ti aggrada e il tuo server linux personale sara’ in piedi in pochi secondi.
Noi di TuxWeb lo stiamo utilizzando con successo per gestire i siti internet di alcuni nostri clienti.
Ciao, Dino – http://www.tuxweb.it/
21 Feb 10 Scandalo, the fast and Simple clamdscan mail frontend
Hi people.
I’m now talking about a simple GPLv2, C written, small program that work as a very fast clamdscan antivirus frontend.
Scandalo can take a mail on standard input and parse it from viruses, piping it to clamdscan.
It then get the virus status from clamdscan and put a mail header called “X-Virus-Ret” returning the virus scanner status.
It also put a mail header called “X-Virus-stream” returning the first virus name found (if any).
You can then setup a rule on your (say, maildrop) mail filter to pipe the incoming mail to scandalo, and another rule to check the return scanned mail header for viruses.
If a virus was found, you can drop the mail, or put it into a .Virus maildir.
If you have any question, I’m the developer of scandalo.
Scandalo – http://www.tuxweb.it/?section=progetti/scandalo&
Write me a note at dino@tuxweb.it.
Ciao, Dino.
Follow me!
Stack Overflow
IPv6 Certified (he.net)