# HG changeset patch
# User JC Brand <jc@opkode.com>
# Date 1551193138 -3600
# Node ID b4bcb84997e714edcc9166ee6f2d52d3ec3414d8
# Parent  c0fc739a1b8131dab9396ff1f0ae097645ae2b05
mod_auth_token: Update README.

Add luarocks dependencies and explain how to generate the token.

diff -r c0fc739a1b81 -r b4bcb84997e7 mod_auth_token/README.markdown
--- a/mod_auth_token/README.markdown	Sun Feb 24 01:02:30 2019 +0100
+++ b/mod_auth_token/README.markdown	Tue Feb 26 15:58:58 2019 +0100
@@ -11,10 +11,17 @@
 
 If the token is verified, then the user is authenticated.
 
-## How to generate the token
+## Luarocks dependencies
+
+You'll need to install the following luarocks
+
+  otp 0.1-5
+  luatz 0.3-1
+
+## How to generate the TOTP seed and shared signing secret
 
 You'll need a shared OTP_SEED value for generating time-based one-time-pin
-values and a shared private key for signing the HMAC token.
+(TOTP) values and a shared private key for signing the HMAC token.
 
 You can generate the OTP_SEED value with Python, like so:
 
@@ -28,10 +35,24 @@
     >>> pyotp.random_base32(length=32)
     u'JYXEX4IQOEYFYQ2S3MC5P4ZT4SDHYEA7'
 
-These values then need to go into your Prosody.cfg file:
+## Configuration
+
+Firest you need to enable the relevant modules to your Prosody.cfg file.
+
+Look for the line `modules_enabled` (either globally or for your
+particular `VirtualHost`), and then add the following to tokens:
 
-token_secret = "JYXEX4IQOEYFYQ2S3MC5P4ZT4SDHYEA7"
-otp_seed = "XVGR73KMZH2M4XMY"
+    modules_enabled = {
+        -- Token authentication
+            "auth_token";
+            "sasl_token";
+    }
+
+The previously generated token values also need to go into your Prosody.cfg file:
+
+    authentication = "token";
+    token_secret = "JYXEX4IQOEYFYQ2S3MC5P4ZT4SDHYEA7";
+    otp_seed = "XVGR73KMZH2M4XMY";
 
 The application that generates the tokens also needs access to these values.
 
@@ -46,3 +67,31 @@
 Prosody doesn't automatically pick up this file, so you'll need to update your
 configuration file's `plugin_paths` to link to this subdirectory (for example
 to `/usr/lib/prosody-modules/mod_auth_token/`).
+
+## Generating the token
+
+Here's a Python snippet showing how you can generate the token that Prosody
+will then verify:
+
+    import base64
+    import pyotp
+    import random
+
+    # Constants
+    OTP_INTERVAL = 30
+    OTP_DIGITS = 8
+
+    jid = '{}@{}'.format(username, domain)
+
+    otp_service = pyotp.TOTP(
+        OTP_SEED,  # OTP_SEED must be set to the value generated previously (see above)
+        digits=OTP_DIGITS,
+        interval=OTP_INTERVAL
+    )
+    otp = otp_service.generate_otp(otp_service.timecode(datetime.utcnow()))
+
+    nonce = ''.join([str(random.randint(0, 9)) for i in range(32)])
+    string_to_sign = otp + nonce + jid
+    signature = hmac.new(token_secret, string_to_sign, hashlib.sha256).digest()
+    token = u"{} {}".format(otp+nonce, base64.b64encode(signature))
+