Best Practices in Building an API Security Ecosystem Prabath Siriwardena, Director of Security, WSO2 Twitter : @prabath
Aug 16, 2015
Best Practices in Building an API Security EcosystemPrabath Siriwardena, Director of Security, WSO2
Twitter : @prabath
About Me
Director of Security Architecture @ WSO2 Apache Axis PMC member Blogs
- http://blog.facilelogin.com- http://blog.api-security.org
Books- “Enterprise Integration with WSO2 ESB” with PACKT- “Advanced API Security” with Apress - “Mastering Apache Maven” with PACKT
Naked APIs vs. Managed APIs
API Ecosystem
Gateway Pattern - Benefits
• Decouple clients from the actual API implementation
• No point-to-point to connection• Centralized security enforcing• Centralized auditing & monitoring• Version controlling
Forces Driving IT Business Re-design
Pre OAuth Era
Pre OAuth Era
Pre OAuth Era
Pre OAuth Era
Third-party applications are required to store the resource owner's credentials for future use, typically a
password in clear-text.
Need a better approach ?
Servers are required to support password authentication, despite the security weaknesses created
by passwords.
Need a better approach ?
Third-party applications gain overly broad access to the resource owner's protected resources, leaving resource owners without any ability to restrict duration or access
to a limited subset of resources.
Need a better approach ?
Resource owners cannot revoke access to an individual third-party without revoking access to all third-parties,
and must do so by changing their password.
Need a better approach ?
Compromise of any third-party application results in compromise of the end-user's password and all of the
data protected by that password.
Need a better approach ?
Delegation
Pre OAuth Era
OAuth Evolution
OAuth 1.0a
OAuth 1.0a : Three Legged
OAuth 1.0a : Two Legged
OAuth 2.0 : Resource Owner
• An entity capable of granting access to a protected resource.
• When the resource owner is a person, it is referred to as an end-user.
OAuth 2.0 : Resource Server
• The server hosting the protected resources, capable of accepting and responding to protected resource requests using access tokens.
OAuth 2.0 : Client
• An application making protected resource requests on behalf of the resource owner and with its authorization
OAuth 2.0 : Authorization Server
• The server issuing access tokens to the client after successfully authenticating the resource owner and obtaining authorization
OAuth 2.0
OAuth 2.0 : Authorization Grant Types
Authorization Code
Implicit
Resource Owner Password Credentials
Client Credentials
OAuth 2.0 : Authorization Code
OAuth Handshake
Scope
OAuth 2.0
OAuth Handshake
Scope
Scope is defined by the Authorization Server.
Scope indicates what resource client wants access and which actions he wants to perform on that.
The value of the scope parameter is expressed as a list of space-delimited, case sensitive strings.
The strings are defined by the authorization server.
OAuth 2.0 : Authorization Code
Confidential Client Type
Web Application
OAuth Handshake
OAuth 2.0 : Authorization Code
Client Authenticates to AuthZ Server
BasicAuth client_id / client_secret
OAuth Handshake
OAuth 2.0 : Authorization Code
Authorization Grant Request
OAuth Handshake
• response_type : REQUIRED. Value MUST be set to "code".• client_id : REQUIRED. The client identifier.• redirect_uri : OPTIONAL. Where to be redirected by the Authorization Server.• scope : OPTIONAL. The scope of the access request.• state : RECOMMENDED. An opaque value used by the client to maintain state between the
request and callback.
OAuth 2.0 : Authorization Code
Authorization Grant Response
OAuth Handshake
• code: REQUIRED. The authorization code generated by the authorization server• state : REQUIRED if the "state" parameter was present in the client authorization request.
OAuth 2.0 : Authorization Code
Access Token Request
OAuth Handshake
• grant_type : REQUIRED. Value MUST be set to "authorization_code".• code : REQUIRED. The authorization code received from the Authorization Server.• redirect_uri : REQUIRED, if the "redirect_uri" parameter was included in the authorization
OAuth 2.0 : Authorization Code
Access Token Response
OAuth Handshake
• access_token : REQUIRED. The access token issued by the authorization server.• token_type : REQUIRED. The type of the token. Value is case insensitive.• expires_in : RECOMMENDED. The lifetime in seconds of the access token
OAuth 2.0 : Implicit
OAuth Handshake
Scope
OAuth 2.0 : Implicit
Public Client Type
User Agent based Application
OAuth Handshake
OAuth 2.0 : Implicit
Anonymous Clients
OAuth Handshake
OAuth Handshake
Authorization Grant Request
• response_type : REQUIRED. Value MUST be set to ”token".• client_id : REQUIRED. The client identifier.• redirect_uri : OPTIONAL. Where to be redirected by the Authorization Server.• scope : OPTIONAL. The scope of the access request.• state : RECOMMENDED. An opaque value used by the client to maintain state between the
request and callback.
OAuth 2.0 : Implicit
Access Token Response
OAuth Handshake
• access_token : REQUIRED. The access token issued by the authorization server.• token_type : REQUIRED. The type of the token. Value is case insensitive.• expires_in : RECOMMENDED. The lifetime in seconds of the access token• scope : OPTIONAL, if identical to the scope requested by the client, otherwise REQUIRED.• state : REQUIRED if the "state" parameter was present in the client authorization request
OAuth 2.0 : Implicit
OAuth 2.0 : Client Credential
OAuth Handshake
Scope
OAuth 2.0 : Client Credential
Confidential Client Type
OAuth Handshake
OAuth 2.0 : Client Credential
BasicAuth
OAuth Handshake
OAuth Handshake
Authorization Grant Request
Since the client authentication is used as the authorization grant, no additional authorization request is needed.
OAuth 2.0 : Client Credential
OAuth Handshake
Access Token Request
OAuth 2.0 : Client Credential
• grant_type : REQUIRED. Value MUST be set to ”client_credentials".• scope: OPTIONAL. The scope of the access request.
Note : The client needs to pass BasicAuth headers or authenticate to the Authorization Server in other means.
Access Token Response
OAuth Handshake
OAuth 2.0 : Client Credential
• access_token : REQUIRED. The access token issued by the authorization server.• token_type : REQUIRED. The type of the token. Value is case insensitive.• expires_in : RECOMMENDED. The lifetime in seconds of the access token
OAuth 2.0 : Resource Owner Password Credentials
OAuth Handshake
Scope
OAuth 2.0 : Resource Owner Password Credentials
Confidential Client Type
OAuth Handshake
OAuth 2.0 : Resource Owner Password Credentials
BasicAuth
OAuth Handshake
OAuth Handshake
Authorization Grant Request
The method through which the client obtains the resource owner credentials is beyond the scope of this specification. The client
MUST discard the credentials once an access token has been obtained
OAuth 2.0 : Resource Owner Password Credentials
OAuth Handshake
Access Token Request
• grant_type : REQUIRED. Value MUST be set to ”client_credentials".• username : REQUIRED. The resource owner username, encoded as UTF-8.• password : REQUIRED. The resource owner password, encoded as UTF-8.• scope: OPTIONAL. The scope of the access request.
OAuth 2.0 : Resource Owner Password Credentials
Access Token Response
OAuth Handshake
• access_token : REQUIRED. The access token issued by the authorization server.• token_type : REQUIRED. The type of the token. Value is case insensitive.• expires_in : RECOMMENDED. The lifetime in seconds of the access token
OAuth 2.0 : Resource Owner Password Credentials
OAuth 2.0
Runtime
OAuth 2.0
Runtime
Bearer MAC
OAuth 2.0
Runtime
Bearer MAC
Any party in possession of a bearer token (a "bearer") can use it to get access to the associated resources (without demonstrating possession
of a cryptographic key).
Bearer
Request with Bearer
GET /resource/1 HTTP/1.1Host: example.comAuthorization: Bearer “access_token_value”
OAuth 2.0
Runtime
http://tools.ietf.org/html/draft-ietf-oauth-v2-bearer-20
OAuth 2.0
Runtime
Bearer MAC
HTTP MAC access authentication scheme
MAC
Request with MAC
GET /resource/1 HTTP/1.1Host: example.com Authorization: MAC id="h480djs93hd8", ts="1336363200”, nonce="274312:dj83hs9s", mac="kDZvddkndxvhGRXZhvuDjEWhGeE="
OAuth 2.0
Runtime
http://tools.ietf.org/html/draft-ietf-oauth-v2-http-mac-01
Decoupling Authorization Server from Resource Server
Decoupling Authorization Server from Resource Server
POST /introspection HTTP/1.1 Accept: application/x-www-form-urlencoded Host: server.example.com Authorization: Basic czZCaGRSa3F0Mzo3RmpmcDBaQnIxS3REUmJuZlZkbUl3
token=X3241Affw.4233-99JXJ&resource_id=…
{ "active": true, "client_id":"s6BhdRkqt3", "scope": "read write dolphin", "sub": "2309fj32kl", "aud": http://example.org/protected-resource/*}
Externalizing Authorization
XACML
OAuth & XACML
A given access token has a scope associated with it and it governs the access token’s capabilities
A user delegates access to his Facebook profile to a third party, under the scope “user_activities”. This provides access to the user's list of activities as the activities’ connection. To achieve fine-grained access control, this can be represented in an XACML policy.
token=gfgew789hkhjkew87 resource_id=GET https://graph.facebook.com/prabathsiriwardena/activities
XACML Request<Request> <Attributes Category="urn:oasis:names:tc:xacml:3.0:attribute-category:oauth-client"> <Attribute AttributeId="urn:oasis:names:tc:xacml:1.0:client:client-id"> <AttributeValue DataType="http://www.w3.org/2001/XMLSchema#string">32324343434</AttributeValue> </Attribute> <Attributes> <Attributes Category="urn:oasis:names:tc:xacml:3.0:attribute-category:action"> <Attribute AttributeId="urn:oasis:names:tc:xacml:1.0:action:action-id"> <AttributeValue DataType="http://www.w3.org/2001/XMLSchema#string">GET</AttributeValue> </Attribute> </Attributes> <Attributes Category="urn:oasis:names:tc:xacml:3.0:attribute-category:scope"> <Attribute AttributeId="urn:oasis:names:tc:xacml:1.0:scope:scope-id"> <AttributeValue DataType="http://www.w3.org/2001/XMLSchema#string">user_activities</AttributeValue> </Attribute> </Attributes> <Attributes Category="urn:oasis:names:tc:xacml:3.0:attribute-category:resource"> <Attribute AttributeId="urn:oasis:names:tc:xacml:1.0:resource:resource-id"> <AttributeValue DataType="http://www.w3.org/2001/XMLSchema#string"> https://graph.facebook.com/prabathsiriwardena/activities</AttributeValue> </Attribute> </Attributes></Request>
XACML Policy
<Policy> <Target> <AnyOf> <AllOf> <Match MatchId="urn:oasis:names:tc:xacml:1.0:function:string-equal"> <AttributeValue DataType="http://www.w3.org/2001/XMLSchema#string"> user_activities</AttributeValue> <AttributeDesignator MustBePresent="false" Category="urn:oasis:names:tc:xacml:3.0:attribute-category:scope" AttributeId="urn:oasis:names:tc:xacml:1.0:scope:scope-id" DataType="http://www.w3.org/2001/XMLSchema#string"></AttributeDesignator> </Match> </AllOf> </AnyOf> </Target> <Rule RuleId="permit_rule" Effect="Permit"> </Rule> <Rule RuleId="deny_rule" Effect="Deny"> </Rule></Policy>
Cross-Domain API Access
Cross-Domain API Access
curl -X POST -u "QlthIzYUOK5DS0BXW8Cy8uFJjKAa:XFfgPmTbMaQ5eScc0rSnAW9ZIgwa” -H "Content-Type: application/x-www-form-urlencoded;charset=UTF-8" -d "grant_type=urn:ietf:params:oauth:grant-type:saml2 bearer&assertion=PHNhbWxwOl...[omitted for brevity]...ZT4" https://localhost:9443/oauth2/token
Auditing / Monitoring
Chained APIs
Centralized Authorization with Distributed Resource Servers
User Managed Access
• PAT (Protection API Token) : Token issued to the Resource Server to access the Protection API (Authorization Server) with the approval of the Resource Owner.
• AAT (Authorization API Token) : Token issued to the Client to access the Authorization API (Authorization Server)..
• RPT (Requesting Party Token) : Token issued to the Client to access the Protected Resource on behalf of the Requesting Party by the Authorization Server.
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