Add OTR support.

This patch adds support for the OTR protocol to irssi. This is an import
of the external irssi-otr project that we are now taking over
maintership for.

Major thanks to the original authors of Irssi-OTR: Uli Meis and David
Goulet. Thanks to the OTR community in #OTR on OFTC, thanks to everyone
who have helped testing the patches and submitted UI suggestions.

2 files changed, 117 insertions, 0 deletions

diff --git a/docs/help/in/otr.in b/docs/help/in/otr.in
new file mode 100644
index 00000000..c31bd8e8
--- /dev/null
+++ b/docs/help/in/otr.in
@@ -0,0 +1,111 @@
+
+OTR %|[OPTION]
+
+Command to control the OTR module. Without an option, this help is printed.
+
+This help contains three sections which are %9options, quickstart and files.%n
+
+To add the OTR status bar (highly recommended):
+
+%9/statusbar window add otr%n
+
+%9Options:%n
+
+AUTH <secret>
+    Start or respond to an authentication process.
+
+AUTHQ <question> <secret>
+    Start a SMP authentication process.
+
+    Example: %9/otr authq "My question is" "this is the secret"%n
+
+AUTHABORT
+    Abort an ongoing authentication process.
+
+CONTEXTS
+    List known contexts which basically list the known fingerprints and their
+    state.
+
+DEBUG
+    Turn on debugging.
+
+DISTRUST <fingerprint>
+    Distrust a specific fingerprint. This command can be done inside a private
+    window for which the current fingerprint of the other person will be used
+    or else set fp to a human readable OTR fingerprint available with the above
+    contexts command.
+
+    Examples: %9/otr distrust 487FFADA 5073FEDD C5AB5C14 5BB6C1FF 6D40D48A%n
+
+FINISH
+    End the OTR session. This MUST be done inside a private conversation
+    window.
+
+FORGET <fingerprint>
+    Forget a specific fingerprint (deleted from the known fingerprints). The
+    behavior is the same as the distrust command explained above.
+
+GENKEY <name>
+    Generate OTR keys for a given account name. This is done automatically
+    if someone tries to establish a secure session.
+
+    This process is done in a background worker and can take an arbitrary
+    amount of time. The completion is checked when another irssi event is
+    catched.
+
+HELP
+    Print this help.
+
+INFO
+    Display the OTR fingerprint(s) of all your account(s).
+
+INIT
+    Initialize an OTR conversation within a private conversation window.
+
+TRUST <fingerprint>
+    Trust a specific fingerprint. The behavior is the same as the forget and
+    distrust commands explained above.
+
+VERSION
+    Print the version of the OTR module.
+
+%9Quickstart:%n
+
+Start a private conversation with the person you want to initiate a secure
+session. Once in the private message window:
+
+%9/otr init%n
+
+Key generation should start if no key is found for your account name. Once the
+process is done, either type a message which should automatically start the
+session or redo the init command.
+
+Time to authenticate the person. Either use a shared secret exchange through
+phone or GPG-signed email or use the socialist millionaire problem mechanism
+(SMP) which is basically to ask a question for which the answer can only be
+known by the other person.
+
+%9/otr auth <shared-secret>%n OR %9/otr authq "A question" <shared-secret>%n
+
+Or to respond to an authentication:
+
+%9/otr auth <secret>%n
+
+%9Files:%n
+
+This otr modules creates a directory in %9$HOME/.irssi/otr%n and creates three
+files:
+
+* %9otr.key%n
+    Contains your OTR private key(s). NEVER shared this directory with someone
+    else unless you know what you are doing.
+
+* %9otr.fp%n
+    The known fingerprints with their _trust_ status.
+
+* %9otr.instag
+    Instance tag of the libotr. This should NEVER be copied to an other
+    computer. If unsure, just ignore this file.
+
+For more information on OTR, see https://otr.cypherpunks.ca/
+
diff --git a/docs/signals.txt b/docs/signals.txt
index 7776dad7..84d4518f 100644
--- a/docs/signals.txt
+++ b/docs/signals.txt
@@ -350,3 +350,9 @@ Perl
 ----
 
 "script error", PERL_SCRIPT_REC, char *errormsg
+
+OTR Core
+--------
+
+otr.c:
+ "otr event", SERVER_REC, char *nick, char *status