Fleshed out login spec.

1 files changed, 164 insertions, 158 deletions

diff --git a/docs/specification.rst b/docs/specification.rst
index c271308675..8df5d478a1 100644
--- a/docs/specification.rst
+++ b/docs/specification.rst
@@ -201,124 +201,133 @@ Clients must register with a home server in order to use Matrix. After
 registering, the client will be given an access token which must be used in ALL
 requests to that home server as a query parameter 'access_token'.
 
-- TODO Kegan : Make registration like login
+- TODO Kegan : Make registration like login (just omit the "user" key on the 
+  initial request?)
 - TODO Kegan : Allow alternative forms of login (>1 route)
 
 If the client has already registered, they need to be able to login to their
 account. The home server may provide many different ways of logging in, such
-as user/password auth, login via a social network (OAuth), login by confirming 
+as user/password auth, login via a social network (OAuth2), login by confirming 
 a token sent to their email address, etc. This specification does not define how
 home servers should authorise their users who want to login to their existing 
 accounts, but instead defines the standard interface which implementations 
 should follow so that ANY client can login to ANY home server.
 
 The login process breaks down into the following:
-  1. Get login process info.
+  1. Determine the requirements for logging in.
   2. Submit the login stage credentials.
-  3. Get access token or be told the next stage in the login process and repeat 
+  3. Get credentials or be told the next stage in the login process and repeat 
      step 2.
      
-- What are types?
-
-Matrix-defined login types
---------------------------
-- m.login.password
-- m.login.oauth2
-- m.login.email.code
-- m.login.email.url
-
-Password-based
---------------
-Type: "m.login.password"
-LoginSubmission::
+As each home server may have different ways of logging in, the client needs to know how
+they should login. All distinct login stages MUST have a corresponding ``'type'``.
+A ``'type'`` is a namespaced string which details the mechanism for logging in.
+
+A client may be able to login via multiple valid login flows, and should choose a single
+flow when logging in. A flow is a series of login stages. The home server MUST respond 
+with all the valid login flows when requested::
+
+  The client can login via 3 paths: 1a and 1b, 2a and 2b, or 3. The client should
+  select one of these paths.
+  
+  [
+    {
+      "type": "<login type1a>",
+      "stages": [ "<login type 1a>", "<login type 1b>" ]
+    },
+    {
+      "type": "<login type2a>",
+      "stages": [ "<login type 2a>", "<login type 2b>" ]
+    },
+    {
+      "type": "<login type3>"
+    }
+  ]
+
+After the login is completed, the client's fully-qualified user ID and a new access 
+token MUST be returned::
 
   {
-    "type": "m.login.password",
-    "user": <user_id>,
-    "password": <password>
+    "user_id": "@user:matrix.org",
+    "access_token": "abcdef0123456789"
   }
 
-Example:
-Assume you are @bob:matrix.org and you wish to login on another mobile device.
-First, you GET /login which returns::
+The ``user_id`` key is particularly useful if the home server wishes to support 
+localpart entry of usernames (e.g. "user" rather than "@user:matrix.org"), as the
+client may not be able to determine its ``user_id`` in this case.
+
+If a login has multiple requests, the home server may wish to create a session. If
+a home server responds with a 'session' key to a request, clients MUST submit it in 
+subsequent requests until the login is completed::
 
   {
-    "type": "m.login.password"
+    "session": "<session id>"
   }
 
-Your client knows how to handle this, so your client prompts the user to enter
-their username and password. This is then submitted::
+This specification defines the following login types:
+ - m.login.password
+ - m.login.oauth2
+ - m.login.email.code
+ - m.login.email.url
 
-  {
-    "type": "m.login.password",
-    "user": "@bob:matrix.org",
-    "password": "monkey"
-  }
 
-The server checks this, finds it is valid, and returns::
+Password-based
+--------------
+Type: 
+  "m.login.password"
+Description:
+  Login is supported via a username and password.
+
+To respond to this type, reply with::
 
   {
-    "access_token": "abcdef0123456789"
+    "type": "m.login.password",
+    "user": "<user_id or user localpart>",
+    "password": "<password>"
   }
 
-The server may optionally return "user_id" to confirm or change the user's ID.
-This is particularly useful if the home server wishes to support localpart entry
-of usernames (e.g. "bob" rather than "@bob:matrix.org").
+The home server MUST respond with either new credentials, the next stage of the login
+process, or a standard error response.
 
 OAuth2-based
 ------------
-Type: "m.login.oauth2"
-This is a multi-stage login.
+Type: 
+  "m.login.oauth2"
+Description:
+  Login is supported via OAuth2 URLs. This login consists of multiple requests.
 
-LoginSubmission::
+To respond to this type, reply with::
 
   {
     "type": "m.login.oauth2",
-    "user": <user_id>
+    "user": "<user_id or user localpart>"
   }
 
-Returns::
+The server MUST respond with::
 
   {
-    "uri": <Authorization Request uri OR service selection uri>
+    "uri": <Authorization Request URI OR service selection URI>
   }
 
-The home server acts as a 'confidential' Client for the purposes of OAuth2.
-
-If the uri is a "sevice selection uri", it is a simple page which prompts the 
-user to choose which service to authorize with. On selection of a service, they
-link through to Authorization Request URIs. If there is only 1 service which the
+The home server acts as a 'confidential' client for the purposes of OAuth2.
+If the uri is a ``sevice selection URI``, it MUST point to a webpage which prompts the 
+user to choose which service to authorize with. On selection of a service, this
+MUST link through to an ``Authorization Request URI``. If there is only 1 service which the
 home server accepts when logging in, this indirection can be skipped and the
-"uri" key can be the Authorization Request URI. 
+"uri" key can be the ``Authorization Request URI``. 
 
-The client visits the Authorization Request URI, which then shows the OAuth2 
-Allow/Deny prompt. Hitting 'Allow' returns the redirect URI with the auth code. 
-Home servers can choose any path for the redirect URI. The client should visit 
-the redirect URI, which will then finish the OAuth2 login process, granting the 
+The client then visits the ``Authorization Request URI``, which then shows the OAuth2 
+Allow/Deny prompt. Hitting 'Allow' returns the ``redirect URI`` with the auth code. 
+Home servers can choose any path for the ``redirect URI``. The client should visit 
+the ``redirect URI``, which will then finish the OAuth2 login process, granting the 
 home server an access token for the chosen service. When the home server gets 
-this access token, it knows that the cilent has authed with the 3rd party, and 
-so can return a LoginResult.
-
-The OAuth redirect URI (with auth code) MUST return a LoginResult.
+this access token, it verifies that the cilent has authorised with the 3rd party, and 
+can now complete the login. The OAuth2 ``redirect URI`` (with auth code) MUST respond 
+with either new credentials, the next stage of the login process, or a standard error 
+response.
     
-Example:
-Assume you are @bob:matrix.org and you wish to login on another mobile device.
-First, you GET /login which returns::
-
-  {
-    "type": "m.login.oauth2"
-  }
-
-Your client knows how to handle this, so your client prompts the user to enter
-their username. This is then submitted::
-
-  {
-    "type": "m.login.oauth2",
-    "user": "@bob:matrix.org"
-  }
-
-The server only accepts auth from Google, so returns the Authorization Request
-URI for Google::
+For example, if a home server accepts OAuth2 from Google, it would return the 
+Authorization Request URI for Google::
 
   {
     "uri": "https://accounts.google.com/o/oauth2/auth?response_type=code&
@@ -329,145 +338,142 @@ The client then visits this URI and authorizes the home server. The client then
 visits the REDIRECT_URI with the auth code= query parameter which returns::
 
   {
+    "user_id": "@user:matrix.org",
     "access_token": "0123456789abcdef"
   }
 
 Email-based (code)
 ------------------
-Type: "m.login.email.code"
-This is a multi-stage login.
+Type: 
+  "m.login.email.code"
+Description:
+  Login is supported by typing in a code which is sent in an email. This login 
+  consists of multiple requests.
 
-First LoginSubmission::
+To respond to this type, reply with::
 
   {
     "type": "m.login.email.code",
-    "user": <user_id>
-    "email": <email address>
+    "user": "<user_id or user localpart>",
+    "email": "<email address>"
   }
 
-Returns::
+After validating the email address, the home server MUST send an email containing
+an authentication code and return::
 
   {
-    "type": m.login.email.code
-    "session": <session id>
+    "type": "m.login.email.code",
+    "session": "<session id>"
   }
 
-The email contains a code which must be sent in the next LoginSubmission::
+The second request in this login stage involves sending this authentication code::
 
   {
     "type": "m.login.email.code",
-    "session": <session id>,
-    "code": <code in email sent>
+    "session": "<session id>",
+    "code": "<code in email sent>"
   }
 
-Returns::
-
-  {
-    "access_token": <access token>
-  }
+The home server MUST respond to this with either new credentials, the next stage of 
+the login process, or a standard error response.
 
 Email-based (url)
 -----------------
-Type: "m.login.email.url"
-This is a multi-stage login.
+Type: 
+  "m.login.email.url"
+Description:
+  Login is supported by clicking on a URL in an email. This login consists of 
+  multiple requests.
 
-First LoginSubmission::
+To respond to this type, reply with::
 
   {
     "type": "m.login.email.url",
-    "user": <user_id>
-    "email": <email address>
+    "user": "<user_id or user localpart>",
+    "email": "<email address>"
   }
 
-Returns::
+After validating the email address, the home server MUST send an email containing
+an authentication URL and return::
 
   {
-    "session": <session id>
+    "type": "m.login.email.url",
+    "session": "<session id>"
   }
 
 The email contains a URL which must be clicked. After it has been clicked, the
-client should perform a request::
-
-  {
-    "type": "m.login.email.code",
-    "session": <session id>
-  }
-
-Returns::
-
-  {
-    "access_token": <access token>
-  }
-
-Example:
-Assume you are @bob:matrix.org and you wish to login on another mobile device.
-First, you GET /login which returns::
-
-  {
-    "type": "m.login.email.url"
-  }
-
-Your client knows how to handle this, so your client prompts the user to enter
-their email address. This is then submitted::
+client should perform another request::
 
   {
     "type": "m.login.email.url",
-    "user": "@bob:matrix.org",
-    "email": "bob@mydomain.com"
+    "session": "<session id>"
   }
 
-The server confirms that bob@mydomain.com is linked to @bob:matrix.org, then 
-sends an email to this address and returns::
+The home server MUST respond to this with either new credentials, the next stage of 
+the login process, or a standard error response. 
 
-  {
-    "session": "ewuigf7462"
-  }
+A common client implementation will be to periodically poll until the link is clicked.
+If the link has not been visited yet, a standard error response with an errcode of 
+``M_LOGIN_EMAIL_URL_NOT_YET`` should be returned.
 
-The client then starts polling the server with the following::
 
-  {
-    "type": "m.login.email.url",
-    "session": "ewuigf7462"
-  }
+N-Factor Authentication
+-----------------------
+Multiple login stages can be combined to create N-factor authentication during login.
 
-(Alternatively, the server could send the device a push notification when the
-email has been validated). The email arrives and it contains a URL to click on.
-The user clicks on the which completes the login process with the server. The
-next time the client polls, it returns::
+This can be achieved by responding with the ``'next'`` login type on completion of a 
+previous login stage::
 
   {
-    "access_token": "abcdef0123456789"
+    "next": "<next login type>"
   }
 
-N-Factor auth
--------------
-Multiple login stages can be combined with the "next" key in the LoginResult.
-
-Example:
-A server demands an email.code then password auth before logging in. First, the
-client performs a GET /login which returns::
+If a home server implements N-factor authentication, it MUST respond with all 
+``'stages'`` when initially queried for their login requirements::
 
   {
-    "type": "m.login.email.code",
-    "stages": ["m.login.email.code", "m.login.password"]
+    "type": "<1st login type>",
+    "stages": [ <1st login type>, <2nd login type>, ... , <Nth login type> ]
   }
 
-The client performs the email login (See "Email-based (code)"), but instead of
-returning an access_token, it returns::
+This can be represented conceptually as::
+
+   _______________________
+  |    Login Stage 1      |
+  | type: "<login type1>" |
+  |  ___________________  |
+  | |_Request_1_________| | <-- Returns "session" key which is used throughout.
+  |  ___________________  |     
+  | |_Request_2_________| | <-- Returns a "next" value of "login type2"
+  |_______________________|
+            |
+            |
+   _________V_____________
+  |    Login Stage 2      |
+  | type: "<login type2>" |
+  |  ___________________  |
+  | |_Request_1_________| |
+  |  ___________________  |
+  | |_Request_2_________| |
+  |  ___________________  |
+  | |_Request_3_________| | <-- Returns a "next" value of "login type3"
+  |_______________________|
+            |
+            |
+   _________V_____________
+  |    Login Stage 3      |
+  | type: "<login type3>" |
+  |  ___________________  |
+  | |_Request_1_________| | <-- Returns user credentials
+  |_______________________|
 
-  {
-    "next": "m.login.password"
-  }
-
-The client then presents a user/password screen and the login continues until
-this is complete (See "Password-based"), which then returns the "access_token".
-     
 Fallback
 --------
+Clients cannot be expected to be able to know how to process every single
+login type. If a client determines it does not know how to handle a given
+login type, it should request a login fallback page::
 
-If the client does NOT know how to handle the given type, they should::
-
-  GET /login/fallback
+  GET matrix/client/api/v1/login/fallback
 
 This MUST return an HTML page which can perform the entire login process.