You've used OpenID Connect. You know a thing or two about OAuth. But have you ever wondered how to achieve Single Sign-On between Angular & ASP.NET Core MVC apps, and automated Single Sign-Out? How, and why, to work with reference tokens? How to create a custom grant, and for what use case that might be a good idea? In this in-depth session we'll cover all of these topics, extensively using IdentityServer4 in the process. Note that some previous knowledge on securing ASP.NET Core applications with OpenID Connect is a must.

1. KEVINDOCKX
https://www.kevindockx.com
OPENID CONNECT
IN-DEPTH
In this session, you’ll learn about
less-than-obvious OIDC
approaches and use cases

2. KEVINDOCKX
MARVIN
HI, I’M KEVIN
@KevinDockx
https://www.kevindockx.com
https://github.com/KevinDockx
Freelance solution architect
focused on APIs and security
Microsoft MVP
Pluralsight Author
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MARVIN
COMING UP
SSOn/SSOut
Reference tokens & token revocation
API to API communication on behalf of the user
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MARVIN
Given multiple
applications, using the
same set of credentials, a
user should only provide
these credentials once
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MARVIN
SINGLE SIGN-ON
id_token
Application A
IDP
id_token
Application B

6. KEVINDOCKX
MARVIN
DEMO TIME Time to dive into code
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7. KEVINDOCKX
MARVIN
SINGLE SIGN-OUT
Application A
IDP
Application B

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MARVIN
SINGLE SIGN OUT: SPECIFICATIONS
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Server-side
Front-Channel Logout
https://openid.net/specs/openid-connect-frontchannel-1_0.html
Back-Channel Logout
https://openid.net/specs/openid-connect-backchannel-1_0.html

9. KEVINDOCKX
MARVIN
SINGLE SIGN-OUT (SERVER, FRONT CHANNEL)
Application A IDP
Application B
sign-out endpoint
sign-out endpoint
iframe (hidden)
logged out
iframe (hidden)

10. KEVINDOCKX
MARVIN
SINGLE SIGN OUT: SPECIFICATIONS
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Client-side
OIDC Session Management (also front-channel)
https://openid.net/specs/openid-connect-session-1_0.html

11. KEVINDOCKX
MARVIN
SINGLE SIGN-OUT (USER AGENT, FRONT CHANNEL)
Application B IDP
Application C
(user agent based)
sign-out endpoint
iframe (hidden)
logged out
hidden iframe polling
check_session_iframe
(URI from discovery
document)

12. KEVINDOCKX
MARVIN
DEMO TIME Time to dive into code
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13. KEVINDOCKX
MARVIN
SELF-CONTAINED VS REFERENCE TOKENS
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JWT (self-contained) Reference token
{
"nbf": 1568970856,
"exp": 1568974456,
"iss": "https://localhost:44391",
"aud": [ "https://localhost:44391/
resources", "api1"],
"client_id": "webclient",
"sub": "818727",
"email": "AliceSmith@email.com",
"scope": ["openid", "email",
"api1"]
}
fe1370fab9e1c7f9edd0d85427f98e6da2fb28d27689fd030fc0042c56
d6e406

14. KEVINDOCKX
MARVIN
SELF-CONTAINED VS REFERENCE TOKENS
14
A self-contained token (JWT) is a protected data structure
with claims and an expiration
• Once the API knows about the public key to verify the signature, no
additional communication with the IDP is required
• A self-contained token potentially grants access for as long as that
token hasn’t expired
• There is no mechanism to revoke self-contained tokens

15. KEVINDOCKX
MARVIN
SELF-CONTAINED VS REFERENCE TOKENS
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A reference token is an identifier for the actual token
• It references a grant result (token) stored at IDP level
• Remove the grant result to revoke access ad hoc
• It requires communication with the IDP on each request
• The communication requirement is often tackled by caching the grant
result

16. KEVINDOCKX
MARVIN
DEMO TIME Time to dive into code
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MARVIN
Use reference tokens for
tokens that leave the
company walls
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Api1
{
sub: “kevin”,
aud: [“api1”]
}
Client
API TOAPIACCESS ON BEHALF OF THE USER

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MARVIN
API TOAPIACCESS ON BEHALF OF THE USER
19
Api1
{
sub: “kevin”,
aud: [“api1”]
}
Client
Api2

20. KEVINDOCKX
MARVIN
API TOAPIACCESS ON BEHALF OF THE USER
20
Api1
{
sub: “kevin”,
aud: [“api1”]
}
Client
Api2
{
aud: [“api2”]
}

21. KEVINDOCKX
MARVIN
API TOAPIACCESS ON BEHALF OF THE USER
21
Api1
{
sub: “kevin”,
aud: [“api1”, “api2”]
}
Client
Api2
{
sub: “kevin”,
aud: [“api1”, “api2”]
}

22. KEVINDOCKX
MARVIN
API TOAPIACCESS ON BEHALF OF THE USER
22
Api1
{
sub: “kevin”,
aud: [“api1”, “api2”]
}
Client
Api2
{
sub: “kevin”,
aud: [“api1”, “api2”]
}

23. KEVINDOCKX
MARVIN
API TOAPIACCESS ON BEHALF OF THE USER
23
Api1
{
sub: “kevin”,
aud: [“api1”]
}
Client
Api2
{
sub: “kevin”,
aud: [“api2”]
}

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MARVIN
API TOAPIACCESS ON BEHALF OF THE USER
24
Api1
{
sub: “kevin”,
aud: [“api1”]
}
Client
Api2
{
sub: “kevin”,
aud: [“api2”]
}

25. KEVINDOCKX
MARVIN
API TOAPIACCESS ON BEHALF OF THE USER
25
We need a custom flow
• OAuth2 was built with extensibility in mind
Token Exchange (proposed standard)
• https://tools.ietf.org/html/draft-ietf-oauth-token-exchange-19
• Describes how to safely exchange tokens for other tokens, including
how to request tokens for employing impersonation and delegation
• We can use impersonation semantics for this – we’re simply
“impersonating” our self

26. KEVINDOCKX
MARVIN
API TOAPIACCESS ON BEHALF OF THE USER
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POST /as/token.oauth2 HTTP/1.1
Host: as.example.com
Content-Type: application/x-www-form-urlencoded
grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Atoken-exchange
&subject_token=eyJhbGciOiJFUzI1NiIsImtpZCI6IjE2In0.eyJhdWQiOiJodHRwc
zovL2FzLmV4YW1wbGUuY29tIiwiaXNzIjoiaHR0cHM6Ly9vcmlnaW5hbC1pc3N1ZXI
uZXhhbXBsZS5uZXQiLCJleHAiOjE0NDE5MTA2MDAsIm5iZiI6MTQ0MTkwOTAwMCwic
3ViIjoiYmRjQGV4YW1wbGUubmV0Iiwic2NvcGUiOiJvcmRlcnMgcHJvZmlsZSBoaXN
0b3J5In0.PRBg-jXn4cJuj1gmYXFiGkZzRuzbXZ_sDxdE98ddW44ufsbWLKd3JJ1VZ
hF64pbTtfjy4VXFVBDaQpKjn5JzAw
&subject_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Aaccess_token

27. KEVINDOCKX
MARVIN
DEMO TIME Time to dive into code
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28. KEVINDOCKX
MARVIN
ADDITIONAL RESOURCES
Demo code on my Github
https://github.com/KevinDockx/
My Pluralsight Courses
https://app.pluralsight.com/profile/author/kevin-dockx
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29. THANK YOU