103 lines
3.8 KiB
Plaintext
103 lines
3.8 KiB
Plaintext
CAP prefix/clog
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===============
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Copyright (c) Soni L. \<fakedme plus irkv3 at gmail dot com>
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This capability provides a mechanism for identifying and conveying a cryptographically secured list of messages to IRC clients.
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This specification also suggests a mechanism by which IRC clients can sync logs, using the information provided by this capability.
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Cap syntax
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----------
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The capability shall be specified as
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prefix/clog=hash_type,hash_type/tag,tag,tag
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Example:
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prefix/clog=sha1,sha256/server-time,prefix/hash
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`server-time` and `prefix/hash` are always implicitly specified, and should be omitted.
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The `HASH` S2C command
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----------------------
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The `HASH` command shall be sent for hashes associated with a channel.
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Each hash must be a cryptographic hash. Non-cryptographic hashes must be ignored. Broken hash algorithms should be avoided. MD5 is explicitly disallowed and must not be used.
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The counter must be able to store numbers in the `0..2^62-1` range.
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These hashes specify the current "heads" of the clog. This is similar to git heads, if you're familiar with them.
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Syntax:
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HASH #channel :hash_type=counter/hash,type=counter/hash,...
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Example:
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>>> JOIN #channel
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<<< JOIN #channel
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<<< NAMES etc
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<<< HASH #channel :sha1=20,something_long
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<<< HASH #channel :sha1=60,something_else sha256=70,another
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Optionally, the server may include a server name with the HASH command:
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<<< :server1.example.com HASH #channel :etc
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<<< :server2.example.com HASH #channel :other
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The `hash` message tag
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----------------------
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The `hash` mesaage tag shall be sent with every `PRIVMSG`, `TOPIC` and `NOTICE`.
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Syntax:
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prefix/hash=type=counter/short_hash,type=counter/short_hash,...
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The use of `short_hash` lowers bandwidth requirements. Consult your cryptography expert for best practices on using cryptography.
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These hashes specify the previous "head(s)" of the clog. "Merges" are just messages with hashes from different sources.
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The hash encompasses the message tags specified by the capability (e.g. `server-time` and `hash`), sorted according to UTF-8 byte order, and the contents of the IRC message, as seen in the following format:
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@prefix/hash=...;server-time=... :nick!user@host PRIVMSG #channel :message
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(This line is what gets hashed)
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Examples:
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TODO
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Security Considerations
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-----------------------
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Clogs are meant for channels that want public logging. An example is the Rust IRC channel. As such, anything in a clog should be assumed public.
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It's possible to recover deleted clogs by setting up a separate IRC network and sending the right hashes on the right channel. However, you'd still need to know the hashes.
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Thus, this isn't a vulnerability, because if you had the hashes, you could just request the logs directly, without going through the process of setting up an IRC network.
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The network could be made to sign all hashes, but you'd need to share the signing key across all servers for it to work correctly. This still doesn't prevent someone
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from getting access to an intercepted, correctly-signed hash, and by sharing the signing key you increase the attack surface.
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The server can and should be able to "undo" hashes. This is useful if, for example, someone posts child pornography - you likely don't want that permanently recorded in a channel's history.
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[FIXME there may be more]
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The `SYNC` CTCP (informative)
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-----------------------------
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*This section is informative.*
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The `SYNC` CTCP is a hypothetical CTCP for syncing logs.
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Syntax:
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SYNC <tox-compatible public key> <port> <host> <host> <...> -[nospam+checksum]
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This is a highly flexible command supporting ipv4, ipv6, hostname, tor, i2p and tox ID.
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Messages sent over non-tox channels must be encrypted with the tox-compatible public key.
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