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@@ -1,311 +1 @@ - - ffff - ff firma - - ffff encrypted mailing list manager - ff - a firma cai mas nao quebra - ff - -Index ------ - - 1 - The concept - 2 - Everyone has the private key X The server has the private key - 3 - Why bash - 4 - Development Guidelines - 5 - Setup - 6 - Tips - 7 - Design and features - 8 - Caveats - 9 - Contact - -The concept ------------ - - In portuguese, "firma" means for signature, signature and trust checking and - is a slang for strength and enterprise. - - All this together just can be one thing: an encrypted mailing list manager :P - - In the streets, the expression "a firma cai mas nao quebra" (the enterprise - falls but does not breaks) is commonly used to talk about the strength of a - group that operates in secrecy. To our list manager, this concept says that - your encrypted mailing list can stops to work -- if the server goes offline - or abducted by aliens -- but the system can never be broken. With firma, we - are trying to follow this philosophy. - - Firma is based on the gpgmailalias.pl perl script, hosted at - http://www.rediris.es/app/pgplist/index.en.html, but completely rewritten - in bash. - - Firma works as a command line and MTA pipe alias tool that receives an - email message in its input, grab the encrypted/signed message, re-encrypt - and send it to each subscriber. - - In the server you just need the script, a keyring with the list keypair - and two config files. When mail arrives, it is redirected by the MTA to the - script and it process the message if its properly encrypted and signed. - No temporary files are written during a message processing and no default - message archive, so no messages -- encrypted or not -- rest on your system - in all steps of the process. - -Everyone has the private key X The server has the private key -------------------------------------------------------------- - - When using a encrypted mailing list software, one must choose between - keeping the private key in the server or send it to each of the - subscribers. We'll not consider the case where every subscribers encrypt - the message to all recipients cause this has none automation in the - process we are looking for. - - For the first there are some options: - - - Schleuder - http://schleuder2.nadir.org/ - - - GPG Mailman - http://medien.informatik.uni-ulm.de/~stefan/gpg-mailman.xhtml - - - Crypt-ML - gpg-ezmlm - http://www.synacklabs.net/projects/crypt-ml/ - - - Secure Email List Services (SELS) - http://sels.ncsa.illinois.edu/ - - For the second option there is the NAH6 Mailman patch, - http://mail.python.org/pipermail/mailman-coders/2003-June/000506.html - - For the firsts releases of Firma, we choose to use just the first option. - In the future the code should contain support for an one-keypair list, - but this is not the main behavior we want in an encrypted mailing list. - This is a question of centralized versus decentralized vulnerability. - - An one-keypair list is more or less just like a mail alias: someone - send an encrypted email to the list address and the manager just forwards - that encrypted email to the lists subscribers, optionally removing some - headers and performing some security auditing. Every user has the list - private key, so if someone lost it to the world then one must regenerate - a keypair and send again to every subscriber. - - In the case of a keypair stored in the server, where subscribers has just - the list pubkey, the list admin just need to remove the correspondent pubkey - from the list's keyring with in case some user has its keypair compromised. - - These two approaches has a similar external hole of some private key turned - public. Designing Firma, we decided for the centralized model, for three main - reasons: - - 1 - A server can be safer than any user's ordinary computer. - - 2 - Automation: when some user is removed from the list, we just remove their - key from the list keyring; in the decentralized approach, the list admin - needs to regenerate a new list keypair, otherwise the unsubscribed user - can still decrypt list messages if he can sniff the mail server traffic. - - 3 - Use a public-key and all info stored onto it as the subscriber info. - -Why Bash --------- - - You may ask why we choose bash. Its really strange a crypto project using - shell scripting language. But bash has many advantages: - - - Bash is found in almost all unix-like systems - - - Small dependencies: firma needs just tools like sed, awk, grep, cut and - gpg itself. Look at the file "GUIDELINES" to see a complete list of all - unix commands needed to run firma. - - - You can easily put all the tools, scripts and config files in a read-only - media to protect against cracks such as rootkits. - - - Keeping your encrypted list manager out from a huge and sometimes bugged - mail software prevents insecure use of your mailing list by an excess of - unwanted functions and routines. - - - Firma has a total KISS design, and bash helps to keep it simple. - - - Firma adopted the style suggested in the Advanced Bash-Scripting Guide, - http://www.tldp.org/LDP/abs/html/scrstyle.html - -Development Guidelines ----------------------- - - As a security project we made a restricted set of guidelines / design policy, - attempting to get a clean, bug-free and high quality code. We choose a slow - development rather than sit-and-code. These rules are detailed in the file - GUIDELINES. - -Setup ------ - - Note for Debian users: you'll need the "expect" package to run firma. - - Firma installation is quite simple: - - 1 - Create a folder to store lists; by default firma use /var/lib/firma/lists - but you can use anything, just edit firma and change FIRMA_LIST_PATH - variable. - - 2 - Copy firma script to whatever you like, e.g. /usr/local/bin and check that - it has no write permission - - 3 - Create a list-wide config file (default is /var/lib/firma/firma.conf) with - the common definitions for all lists. You might just copy the sample - firma.conf.dist and edit according to your needs. - - All config variables can be overwritten at each list's own config file; - firma.conf should be chmoded as 600, chowned nobody.nobody or whatever - user your MTA runs. If you run postfix, the user is specified by the - main.cf parameter "default_privs". - - For a list of all config parameters, type - - firma --help config - - 4 - Then create your lists with the command - - firma -c your-list - - Then firma will ask some questions and create a gpg keyring and a config - file with the following variables: - - LIST_ADDRESS= list's email address - LIST_ADMIN= list's administrators email addresses (space separated) - LIST_HOMEDIR= list's GnuPG homedir, where the list's keyrings are located - PASSPHRASE= passphrase for the list's private keyring - - Then a gpg keypair and a config file are automatically generated; - the owner of the config file and keyring should be nobody.nobody - (or the user your MTA run as) and its permissions must be 600. - - After that you can add some optional parameters on this list config file: - - SUBJECT_PREFIX= prefix to be included in the subject of list messages - - REMOVE_THESE_HEADERS= headers that should be stripped from list messages - (space separated case-insensitive entries) - (may include regexps (e.g., X-.*) - - REPLIES_SHOULD_GO_TO_LIST= set to '1' to add a Reply-To header containing the - list address - - SILENTLY_DISCARD_INVALID_MESSAGES= set to '1' to silently discard invalid - messages (message not signed/encrypted, - sender not subscribed to the list, etc.) - instead of sending bounces back to sender - - KEYSERVER= default keyserver to import/export keys - (defaults to keyserver.noreply.org) - - REQUIRE_SIGNATURE= whether messages sent to the list should be (1) or don't - need to be (0) signed to be processed; defaults to '1'; - this doesn't affect the way email administration works, - when signature is mandatory - - For a list of all config parameters, type - - firma --help config - - 5 - Create an alias to the list at your MTA; on sendmail or postfix, - add this to your aliases file: - - your-list: "| /usr/local/bin/firma -p your-list" - your-list-request: "| /usr/local/bin/firma -e your-list" - - and then run the command - - newaliases - - alternatively, you can use a virtual mailbox table if you want - to easily host a lot of encrypted mailing lists. - - 6 - Admin tasks are performed through aliases like your-list-request@yourmachine - or via command-line: - - firma -a your-list - - inside this command or encrypted in your mailing list request, use the - following commands: - - sub keyserver|keyfile key-id - - subscribe key-id pubkey from file or keyserver (currently not - implemented) - - unsub email-address - - unsubscribe all keys with email-address IDs (currently not - implemented) - - use email-address - - uses the given address for message delivery instead - of the primary address of a subscribed key - - 7 - To subscribe and unsubscribe manually the users and the list admins on, use - a command line like - - gpg --homedir [path-to-your-list-keyring] --import < file - - and be sure that after this command the list keyring is owned by nobody.nobody. - - 8 - Send encrypted AND signed messages to your-list@yourmachine and look - what happens :) - -Tips ----- - - - Use an encrypted swap memory - - Use a read-only media to store firma and its needed apps - - Use ramdisk to FIRMA_LIST_PATH so all keys and passwords vanishes if the server is shutdown - - Use a big PASSPHRASE, 25+ chars with alpha-numeric and special ascii keys - -Design and features (OUTDATED) -------------------- - - Firma is simple but its simplicity doesn't reflect in lack of design. - - - Uses a gpg keyring to store both the keys and the subscribers options - - - Command line is simple to avoid admin tasks resting in some .bash_history - - - Non-pgp blocks in a message are discarded since we don't want to deal with - unencrypted content - - - All unwanted email headers are striped as a privacy measure for who sends - the message - - - Firma doesn't use any disk write when processing a message; no temp files - that may rest in the system; everything goes in memory (but take care, - sometimes it will use the swap and then is best to make it encrypted) - - - By default it doesn't archive messages in the server - - - By default it removes the Subject header and put it inside the encrypted - message, as Subject are outside the PGP/MIME context - - - Messages appear to be sent To: Undisclosed Recipients - - Major features are: - - - Keyring support - - - Administration through email or command-line - -8 - Caveats - - People that uses Sylpheed should config the list to accept messages that - arent signed. Thats because currently firma depends that the encrypted - and signed parts come in the same PGP block and Sylpheed splits the - encrypted message and the signature in two separate blocks. Thats a - firma and not Sylpheed issue. The PGP/MIME spec allows one to send - the PGP/MIME encrypted message in two separate blocks. We hope to fix - this someday :) - -9 - Contact - - Contact: firma (@) firma.sarava.org - - Messages should be encrypted with the list pubkey - 3DF104314023E18358EFDD270D51B4E79E693CF7 found at keys.indymedia.org. - +index.mdwn
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