TLS support Last revised: Jan 26, 2020

TLS support

This document provides information about TLS support which is a new eggdrop feature since version 1.8.0.

About

Eggdrop can be optionally compiled with TLS support. This requires OpenSSL 0.9.8 or more recent installed on your system. TLS support includes encryption for IRC, DCC, botnet, telnet and scripted connections as well as certificate authentication for users and bots.

Installation

./configure and install as usual, the configure script will detect if your system meets the requirements and will enable TLS automatically. You can override the autodetection and manually disable TLS with ./configure –disable-tls. You can’t forcefully enable it though. The configure script will look for OpenSSL at the default system locations. If you have it installed at a non-standard location or locally in your home directory, you’ll need to specify the paths to header and library files with the –with-sslinc and –with-ssllib options. You can also use these if you want to override the default OpenSSL installation with a custom one, as they take precedence over any system-wide paths.

Usage

As of v1.9.0, TLS support must be requested explicitly for botnet links. To create a TLS-enabled listening port or connect to a TLS-enabled listening port, you must prefix the port with a plus sign (+). If a port number could normally be omitted as part of a command syntax must be included (and prefixed) to enable TLS.

Scripts can also upgrade a regular plaintext connection to TLS via STARTTLS using the starttls Tcl command.

Prior to v1.9.0, Eggdrop would use STARTTLS to automatically attempt to upgrade a plain connection to an encrypted connection for botnet links, without any additional configuration (This was changed to provide users the flexibility to configure their own environments and assist in debugging).

IRC

To connect to IRC using SSL, specify the port number and prefix it with a plus sign. Example: .jump irc.server.com +6697. The same goes for the server list in the config file.

Some NickServ services allow you to authenticate with a certificate. Eggdrop will use the certificte pair specified in ssl-privatekey/ ssl-certificate for authentication.

Botnet

Eggdrop can use TLS connections to protect botnet links if it is compiled with TLS support. As of version 1.9.0, only raw TLS sockets are used to protect a connection. By prefixing a listen port in the Eggdrop configuration with a plus (+), that specifies that port as a TLS-enabled port, and will only accept TLS connections (no plain text connections will be allowed). With two TLS-enabled Eggdrops, it graphically looks like this:

Leaf bot sets hub port as… and Hub bot config uses… the connection will…
port listen port be plain, but can be upgraded to TLS manually with the starttls Tcl/bot command
+port listen +port connect with TLS
port listen +port fail as hub only wants TLS
+port listen port fail as leaf only wants TLS

In short, a bot added to your Eggdrop with a +port in the address can only connect to a bot listening with a +port in the config. Conversely, a bot added to your eggdrop without a + prefix can only connect to a bot listening without a + prefix in the config.

If TLS negotiation fails, the connection is deliberately aborted and no clear text is ever sent by the TLS-requiring party.

Eggdrop can also upgrade a plaintext connection with the starttls Tcl command. To use this, a plaintext connection is first made to a non-TLS port (ie, one that is not prefixed with a plus), then the starttls command is issued to upgrade that link to a TLS connection. In the Eggdrop 1.8 series, Eggdrop automatically attempted a starttls upgrade on all botnet connections. As such, if a 1.8 Eggdrop connects to a plain listening port on a 1.9.0 or later Eggdrop, it will automatically attempt to upgrade the link to TLS.

Secure DCC

Eggdrop supports the SDCC protocol, allowing you to establish DCC chat and file transfers over SSL. Example: /ctcp bot schat Note, that currently the only IRC client supporting SDCC is KVIrc. For information on how to initiate secure DCC chat from KVIrc (rather than from the bot with /ctcp bot chat), consult the KVIrc documentation.

Scripts

Scripts can open or connect to TLS ports the usual way specifying the port with a plus sign. Alternatively, the connection could be established as plaintext and later switched on with the starttls Tcl command. (Note that the other side should also switch to TLS at the same time - the synchronization is the script’s job, not eggdrop’s.)

Keys, certificates and authentication

You need a private key and a digital certificate whenever your bot will act as a server in a connection of any type. Common examples are hub bots and TLS listening ports. General information about certificates and public key infrastructure can be obtained from Internet. This document only contains eggdrop-specific information on the subject. The easy way to create a key and a certificate is to type ‘make sslcert’ after compiling your bot (If you installed eggdrop to a non-standard location, use make sslcert DEST=/path/to/eggdrop). This will generate a 4096-bit private key (eggdrop.key) and a certificate (eggdrop.crt) after you fill in the required fields. Alternatively, you can use ‘make sslsilent’ to generate a key and certificate non-interactively, using pre-set values. This is useful when installing Eggdrop via a scripted process.

To authenticate with a certificate instead of using password, you should make a ssl certificate for yourself and enable ssl-cert-auth in the config file. Then either connect to the bot using TLS and type “.fprint +” or enter your certificate fingerprint with .fprint SHA1-FINGERPRINT. To generate a ssl certificate for yourself, you can run the following command from the eggdrop source directory:

openssl req -new -x509 -nodes -keyout my.key -out my.crt -config ssl.conf

When asked about bot’s handle, put your handle instead. How to use your new certificate to connect to eggdrop, depends on your irc client. To connect to your bot from the command line, you can use the OpenSSL ssl client:

openssl s_client -cert my.crt -key my.key -connect host:sslport

SSL/TLS Settings

There are some new settings allowing control over certificate verification and authorization.

ssl-privatekey

file containing Eggdrop’s private key, required for the certificate.

ssl-certificate

Specify the filename where your SSL certificate is located. if your bot will accept SSL connections, it must have a certificate.

ssl-verify-depth

maximum verification depth when checking certificate validity. Determines the maximum certificate chain length to allow.
ssl-capath
ssl-cafile
specify the location of certificate authorities certificates. These are used for verification. Both can be active at the same time. If you don’t set this, validation of the issuer won’t be possible and depending on verification settings, the peer certificate might fail verification.

ssl-ciphers

specify the list of ciphers (in order of preference) allowed for use with ssl.

ssl-cert-auth

enables or disables certificate authorization for partyline/botnet. This works only for SSL connections (SDCC or telnet over SSL). A setting of 1 means optional authorization: If the user/bot has a fingerprint set and it matches the certificate SHA1 fingerprint, access is granted, otherwise ordinary password authentication takes place.

If you set this to 2 however, users without a fingerprint set or with a fingerprint not matching the certificate, will not be allowed to enter the partyline with SSL. In addition to this user and bot certificates will be required to have an UID field matching the handle of the user/bot.

ssl-verify-dcc
ssl-verify-bots
ssl-verify-server
ssl-verify-clients
control ssl certificate verification. A value of 0 disables verification completely. A value of 1 enables full verification. Higher values enable specific exceptions like allowing self-signed or expired certificates. Details are documented in eggdrop.conf.

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