@privacybydesign/yivi-client
v0.1.3
Published
A plugin to allow your Yivi flows to communicate with a server
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Yivi client
This plugin for yivi-core
allows your Yivi flow to communicate with a back-end.
It is highly configurable for use in many different setups. This plugin takes
care of initiating most of the transitions to the yivi-core
state machine.
Usage
For a simple demo where you directly start an Yivi session at an IRMA server (not recommended in web browsers!, see below) you can use this snippet:
const YiviCore = require('@privacybydesign/yivi-core');
const Client = require('@privacybydesign/yivi-client');
const yivi = new YiviCore({
session: {
// Point this to your IRMA server:
url: 'http://localhost:8088',
// Define your disclosure request:
start: {
method: 'POST',
headers: {
'Content-Type': 'application/json',
},
body: JSON.stringify({
'@context': 'https://irma.app/ld/request/disclosure/v2',
'disclose': [
[
[ 'pbdf.pbdf.email.email' ],
[ 'pbdf.sidn-pbdf.email.email' ],
]
]
})
}
}
});
yivi.use(Client);
yivi.start();
Options
debugging
This plugin listens to the debugging
option, and will render some basic
information when debugging is enabled.
session
The session
options contains three property structs with options for
starting and finishing Yivi sessions:
start
dealing with fetching the information needed for a new Yivi session (like the session pointer) from a remote server;mapping
dealing with parsing the needed information out of the information fetched duringstart
;result
dealing with fetching the result from a remote server.
More details about these property structs can be found below.
The only separate option session
contains is the url
option,
specifying the url of your remote server. This option is required when you
use the start
and/or the result
option.
If you want to use another plugin for starting Yivi sessions, you can disable
the session functionality of yivi-client
by saying session: false
.
This means you have to specify a custom plugin instead that requests
the transitions related to starting and finishing a session.
It concerns the transitions in the following states:
General outline:
session: {
url: 'http://example.com/irmaserver',
start: {
...
},
mapping: {
...
},
result: {
...
}
}
Option start
These options define the HTTP request yivi-client
has to do in order
to fetch the information of the Yivi session that has to be performed.
The response of this endpoint must at least contain an Yivi sessionPtr
,
and ideally also a frontendRequest
to use the latest features.
A session pointer and frontend request can be retrieved at the IRMA server
by using the IRMA server library,
the IRMA server REST API
or using one of the IRMA backend packages.
The default values for start
are such that an HTTP GET request is performed on
the endpoint ${o.url}/session
(during yivi-core
state Loading
).
In here, o
is the value of the session
struct as described above. The response
that is received is parsed using the specified parseResponse
function. The default values for start
can be found below.
start: {
url: o => `${o.url}/session`,
parseResponse: r => r.json()
// And the default settings for fetch()'s init parameter
// https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch
}
We use the fetch()
default settings.
The properties from start
are passed as custom options
to fetch()
. This means you can use all options
of fetch()
to customize the request yivi-client
does for you. For example,
in case you want a specific POST request to be done instead of the default
GET request, you can do so.
start: {
method: 'POST',
headers: {
'Content-Type': 'application/json',
},
body: JSON.stringify({
'@context': 'https://irma.app/ld/request/disclosure/v2',
'disclose': [
[
[ 'pbdf.pbdf.email.email' ],
[ 'pbdf.sidn-pbdf.email.email' ],
]
]
})
}
If you don't need your Javascript to fetch the session pointer, you can set
start
to false
. This is for example useful when you obtained the
session pointer, frontend request, etc. in another way. Please check the mapping options
how to insert your custom parameters into yivi-client
.
Be aware that when you set start
to false, a user can only handle a session
once. When the user cancels a session or runs into some error, no restart
can be done by the user. As a developer you are responsible yourself to take
into account alternative flows for these cases. We therefore do not recommend
disabling start
.
It is also recommended to not start sessions or fetch results on the IRMA server
from a web browser directly. Instead, you mostly have a service in between that starts
the session and checks the result for you. So in the browser the url
property of
session
should point to a server that you control, which isn't your IRMA server.
Option mapping
With the mapping
properties you can specify how the session pointer, the frontend
request, the requestor token, and possibly other values
can be derived from the start session response. The response received using
the options from start
is first parsed by its parseResponse
. The mapping
functions then specify how to map the parsed response on particular
variables. By default, the following mappings are present:
sessionPtr
: the result from thesessionPtr
mapping should be a valid YivisessionPtr
, as being received from theirma server
. This mapping is mandatory. It defaults to using thesessionPtr
field from the parsed JSON response of thestart
endpoint.sessionToken
: the result from thesessionToken
mapping should be a valid Yivi requestor token, as being received from theirma server
. This mapping is only mandatory if the token is required by the specifiedresult
endpoint. It defaults to using thetoken
field from the parsed JSON response of thestart
endpoint (if present).frontendRequest
: the result from thefrontendRequest
mapping should be a valid Yivi frontend session request, as being received from theirma server
. It defaults to using thefrontendRequest
field from the parsed JSON response of thestart
endpoint (if present). If not present, only frontend protocol version 1.0 is supported. This means that pairing functionality cannot be used. This might be a security risk. Furthermore, frontend protocol version 1.0 lacks proper support for chained sessions.
Additional mappings can also be added. Their names are free to choose (as long as there is no name collision).
The resulting variables are given as payload to the loaded
transition of the yivi-core
state machine. The payload is an object and the result of each mapping
function is recorded as a field
within this object, being named after its map key. In this way the mappings can be accessed by all other plugins.
Within yivi-client
the mappings can also be accessed as second parameter in the url
option of
the result
property struct. There it can be used to compose
the result endpoint. Furthermore, the mappings are used in several state options.
In case you obtain a session pointer (and possibly the other values) in another way than via start
,
you can override the mapping functions to manually specify your mappings. For example, when you
somewhere collected the necessary information to start an Yivi session in JavaScript variables,
say customQr
and customFrontendRequest
, you can start this session by doing:
session: {
start: false,
mapping: {
sessionPtr: () => customQr,
frontendRequest: () => customFrontendRequest
},
result: false
}
In case no mapping option is specified (i.e. the mapping
option is not
specified within session
), the default mapping is used. The default
mapping can be found below.
mapping: {
sessionPtr: r => r.sessionPtr,
sessionToken: r => r.token,
frontendRequest: r => r.frontendRequest
}
Option result
These options define the HTTP request yivi-client
has to do when an Yivi
session succeeds. In this way results of the Yivi session can be fetched.
This option has the same outline as the start
option.
The default values are set for fetching the session result (in the PreparingResult
state)
with a GET request on the endpoint ${o.url}/session/${sessionToken}/result
.
In this, o
(in ${o.url}
) points to the value of the session
struct as described above.
We use the fetch()
default settings.
The result
properties are passed as custom options
to fetch()
. This means you can use all options
of fetch()
to customize the request yivi-client
does for you.
If you don't need your Javascript to fetch a session result, you can set
result
to false
. The yivi-core
Promise will then just resolve
with the mapping
values as result when the session is done.
The default values for the result
options can be found below.
result: {
url: (o, {sessionPtr, sessionToken}) => `${o.url}/session/${sessionToken}/result`,
parseResponse: r => r.json()
// And the default settings for fetch()'s init parameter
// https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch
}
state
The state
option tells the plugin what states it should use and how to subscribe for
listeners that monitor state changes on the IRMA server. You can find an overview of
the possible option sets in the subsections.
There are two general options, url
and legacyUrl
, to determine the location of the
frontend endpoints of the IRMA server. The legacyUrl
is used for frontend protocol
version 1.0 (for IRMA server v0.7.x and earlier)
and the url
is used for frontend protocol version 1.1 and above.
These are the accepted general properties and their defaults:
state: {
url: (m, endpoint) => `${m.sessionPtr.u}/frontend/${endpoint}`,
legacyUrl: (m, endpoint) => `${m.sessionPtr.u}/${endpoint}`,
...
}
The URL from m.sessionPtr.u
will point directly to your IRMA server.
This is intentional; the Yivi app should be able to access those endpoints too.
State monitoring
For state monitoring, we offer the options serverSentEvents
and polling
.
By default, the plugin tries to use Server Sent Events for receiving state changes, and if
that fails it will fall back to basic polling. You can disable either feature by setting
the option to false
instead of an object.
These are the accepted properties and their defaults for state monitoring:
state: {
serverSentEvents: {
endpoint: 'statusevents',
timeout: 2000
},
polling: {
endpoint: 'status',
interval: 500,
startState: 'INITIALIZED'
}
}
Cancellation
The irma server
knows an endpoint to delete sessions. This endpoint is being
used to communicate session cancellation initiated by the user via this library.
Communicating cancellation to the irma server
can be disabled by
setting the cancel
option to false
instead of an object.
These are the accepted properties and their defaults for cancellation:
state: {
cancel: {
url: m => m.sessionPtr['u']
},
}
The URL from m.sessionPtr['u']
will point directly to your IRMA server.
This is intentional; the Yivi app should be able to access those endpoints too.
Please remark that for cancellation there is no frontend specific endpoint at the Yivi
server. Therefore, the URL of the cancellation endpoint deviates from the frontend
endpoint format being specified by the general url
option above.
Pairing
The pairing state is an optional state that can be introduced to prevent QR theft, added between scanning a Yivi QR code and actually performing the session. In this state, a pairing code is visible in the Yivi app. The user should enter that pairing code in the frontend to continue. For the following session types it is important that the right user scans the QR, since the session might contain sensitive information.
- Issuing sessions
- Disclosing sessions with fixed attribute values (e.g. show that your email address is [email protected])
- Signing sessions (the message that needs signing might contain sensitive information)
- Chained sessions (i.e. a
nextSession
is being specified as extra parameter in the session request)
For these session types, the frontendRequest
will include an extra field "pairingHint": true
.
When this happens, pairing will be enabled by default when a QR is scanned. In case
of a mobile session, a pairing state is never introduced.
In case you do not want a pairing state to happen for the above session
types, the pairing state can be disabled by setting the pairing
option to false
instead of an object. You can also change the condition in which pairing is enabled
by modifying the onlyEnableIf
option. For example, you can enable pairing
unconditionally by doing onlyEnableIf: () => true
.
These are the accepted properties and their defaults for pairing. You can overrule options one by one. When you don't specify an option explicitly, the default value is used.
state: {
frontendOptions: {
endpoint: 'options',
requestContext: 'https://irma.app/ld/request/options/v1'
},
pairing: {
onlyEnableIf: m => m.frontendRequest.pairingHint,
completedEndpoint: 'pairingcompleted',
minCheckingDelay: 500, // Minimum delay before accepting or rejecting a pairing code, for better user experience.
pairingMethod: 'pin'
}
}
As an example on how to use the pairing options, you can specify the following options if you want to disable pairing in all cases. Only do this if you are aware of the security implications!
state: {
pairing: false
}
Behaviour
This plugin initiates the following transitions to the yivi-core
state machine.
When being in state Uninitialized
If session
option is set to false
, the plugin does nothing in this state.
Otherwise, this plugin will initiate the initialize
transition when start()
is called. The canRestart
indicator is set to true when the start
option
is enabled (so if start
is not explicitly set to false
).
| Possible transitions | With payload | Next state |
|----------------------|----------------------------|---------------------|
| initialize
| { canRestart: true/false } | Loading |
When being in state Loading
If session
option is set to false
, the plugin does nothing in this state.
Otherwise this plugin:
- Fetches the
start
endpoint (unlessstart
is explicitly set tofalse
). - Extracts the session pointer (and, if specified, the session token and frontend authentication token)
using the functions from the
mapping
option.
| Possible transitions | With payload | Next state |
|----------------------|---------------------------|---------------------|
| loaded
| mappings | CheckingUserAgent |
| fail
| Error that fetch returned | Error |
When being in state CheckingUserAgent
Determines which flow should be started: the QR flow or the mobile flow.
| Possible transitions | With payload | Next state |
|----------------------|--------------|---------------------|
| prepareQRCode
| | PreparingQRCode |
| prepareButton
| | PreparingYiviButton |
When being in state PreparingQRCode
or PreparingYiviButton
In these states the plugin prepares for showing a QR or a button to a mobile session. This includes enabling or disabling the pairing state if necessary.
| Possible transitions | With payload | Next state |
|----------------------------------------------------|----------------------------------------------------------|-------------------|
| showQRCode
if state is PreparingQRCode
| {qr: <payload for in QRs>, showBackButton: true/false}
| ShowQRCode |
| showYiviButton
if state is PreparingYiviButton
| {mobile: <app link for launching the Yivi app>}
| ShowYiviButton |
| fail
if updating pairing state fails | Error that fetch returned | Error |
When being in state ShowingQRCode
or ShowingYiviButton
In these states the plugin polls the status at IRMA server using the state
options.
| Possible transitions | With payload | Next state |
|---------------------------------------------|---------------------------|-----------------------------------------|
| appConnected
if new status is CONNECTED
| | ContinueOn2ndDevice / ContinueInYiviApp |
| appPairing
if new status is PAIRING
| | EnterPairingCode |
| timeout
if new status is TIMEOUT
| | TimedOut |
| cancel
if new status is CANCELLED
| | Cancelled |
| fail
if sse/polling fails | Error that fetch returned | Error |
When being in state EnterPairingCode
In these states the plugin polls the status at IRMA server using the state
options.
| Possible transitions | With payload | Next state |
|---------------------------------------------|---------------------------|-----------------------------------------|
| timeout
if new status is TIMEOUT
| | TimedOut |
| cancel
if new status is CANCELLED
| | Cancelled |
| fail
if sse/polling fails | Error that fetch returned | Error |
When being in state Pairing
In these states the plugin polls the status at IRMA server using the state
options.
| Possible transitions | With payload | Next state |
|--------------------------------------------------------|---------------------------|---------------------|
| pairingRejected
if entered pairing code is incorrect | Rejected pairing code | EnterPairingCode |
| appConnected
if new status is CONNECTED
| | ContinueOn2ndDevice |
| timeout
if new status is TIMEOUT
| | TimedOut |
| cancel
if new status is CANCELLED
| | Cancelled |
| fail
if sse/polling fails | Error that fetch returned | Error |
When being in state ContinueOn2ndDevice
or ContinueInYiviApp
In this state we continue polling the IRMA server using the state
options.
| Possible transitions | With payload | Next state |
|---------------------------------------------|---------------------------|-------------------|
| prepareResult
if new status is DONE
| | PreparingResult |
| timeout
if new status is TIMEOUT
| | TimedOut |
| cancel
if new status is CANCELLED
| | Cancelled |
| fail
if sse/polling fails | Error that fetch returned | Error |
When being in state PreparingResult
If the session
option is set to false
, the plugin does nothing in this state.
Otherwise, when the result
endpoint is enabled (so if result
is not explicitly set to false
),
then the result
endpoint is fetched.
| Possible transitions | With payload | Next state |
|--------------------------------------|---------------------------|--------------|
| succeed
if result can be fetched | Fetched result | Succeed |
| succeed
if result is disabled | | Succeed |
| fail
if fetching the result failed | Error that fetch returned | Error |