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+# mod_auth_token
+
+This module enables Prosody to authenticate time-based one-time-pin (TOTP) HMAC tokens.
+
+This is an alternative to "external authentication" which avoids the need to
+make a blocking HTTP call to the external authentication service (usually a web application backend).
+
+Instead, the application generates the HMAC token, which is then sent to
+Prosody via the XMPP client and Prosody verifies the authenticity of this
+token.
+
+If the token is verified, then the user is authenticated.
+
+## How to generate the token
+
+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.
+
+You can generate the OTP_SEED value with Python, like so:
+
+    >>> import pyotp
+    >>> pyotp.random_base32()
+    u'XVGR73KMZH2M4XMY'
+
+and the shared secret key as follows:
+
+    >>> import pyotp
+    >>> pyotp.random_base32(length=32)
+    u'JYXEX4IQOEYFYQ2S3MC5P4ZT4SDHYEA7'
+
+These values then need to go into your Prosody.cfg file:
+
+token_secret = "JYXEX4IQOEYFYQ2S3MC5P4ZT4SDHYEA7"
+otp_seed = "XVGR73KMZH2M4XMY"
+
+The application that generates the tokens also needs access to these values.
+
+For an example on how to generate a token, take a look at the `generate_token`
+function in the `test_token_auth.lua` file inside this directory.
+
+## Custom SASL auth
+
+This module depends on a custom SASL auth mechanism called X-TOKEN and which
+is provided by the file `mod_sasl_token.lua`.
+
+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/`).