Oauth 2 - params ordering and signature integrity - oauth-2.0

I have two questions:
Q1: Why does OAuth2 require params to be ordered and encoded (for 2-legged)?
All it has to worry about is the matching signature in both the end for the given data(query string).
We can just check the signature generated using the query string.(e.g ?a=1&b=2). Since the signature is generated based on the secret key which is known only to the client and provider, we can only consider the query string without any ordering/encoding.
So, what's the advantage in doing ordering/encoding and then creating the signature?
Q2: How can this signature save me from man-in-the middle attack?
If I have to make a request like this to my server from a client:
increaseUserPoints?userId=1&pointsToAdd=5&appId=x&token=XYZ
Now the token XYZ will be always same, so a hacker could keep posting the same request to increase points. Since the generated token from the given appId is the same, the server will allow this. How is this case handled?

Q1: Ordering the query parameters brings sanity to the HMAC.
Let's say you have two parameters: 'pointsToAdd' and 'appId'. Using the query string pointsToAdd=X&appID=y creates a different HMAC to appID=y&pointsToAdd=X. Because both you and the server need to generate the same HMAC to verify the requests having unordered query parmeters plain fails.
Q2: This saves you from an attack because only you and the server know how to sign your request.
You have a secret key, and only you and the server knows it. This key signs the request. If the HMAC doesn't match according to this secret key, the request fails.
Because all parameters have been used to create the HMAC the request is secure from MITM attacks — a hacker can't change, add or delete any query parameters, or the server will produce a different HMAC when it attempts to authorise and the request fails.

Related

What is an opaque token?

And what does it mean that they are in a "proprietary format"? I am reading about JWT refresh tokens and they are opaque tokens, but I don't understand the term.
A JWT has readable content, as you can see for example on https://jwt.io/.
Everyone can decode the token and read the information in it. The format is documented in RFC 7519.
An opaque token on the other hand has a format that is not intended to be read by you. Only the issuer knows the format.
The meaning of the word already gives a hint:
opaque
/ə(ʊ)ˈpeɪk/
adjective
not able to be seen through; not transparent.
Here's a quote from https://auth0.com/docs/tokens:
Opaque tokens: Tokens in a proprietary format that typically contain some identifier to information in a server’s persistent storage. To validate an opaque token, the recipient of the token needs to call the server that issued the token.
A "opaque JWT refresh token" is a contradiction as per definition above. What actually is meant here is, that in some JWT frameworks only the authentication token is a JWT, but as refresh token they use opaque tokens.
Here, the term "opaque" means the string (that serves as token) is like a reference (in OOPs), or pointer (in C), or foreign keys (in relational DBs).
i.e. You need an external content to resolve it.
Simple versus Composite:
The string is a "simple" string, as opposed to JWS, where is "composite"; It has parts "inside" it.
Inside versus Outside:
You can extract a payload (with claims, etc) out of it without referring to an external server or storage, "outside" this string.
Since an opaque token is a simple string it is just a reference, hence, naturally, its format is entirely arbitrarily determined by the server that issues it (hence the term "proprietary format"). The token string is determined at the time of creation of the underlying (referred-to) content, i.e. when it is paired (associated) with the contents that this token (as the reference or foreign key) refers to.

Handle hash (#) in query string

I try create simple OAuthHandler.
After my request (using the implicit flow), server send request to my page, with an authorization code. But in query string from server, all parameters starts with hash (#) instead?
In method HandleRemoteAuthenticateAsync, I'm trying to parse query string, but none of the properties contain authorization code or anything like that.
How can I handle hash in query string?
As Joppe and David mentioned in the comments, anything after the hash (#) is part of the fragment, and is not sent to the server by the browser. That's why your server code can't see it.
The implicit flow is for JavaScript clients, not web servers. You want the authorization code flow instead. The redirect will look like:
REDIRECT_URI?code=7a6fa...
Since the code is transmitted in the query string, instead of the fragment, your server-side code will be able to see it.

F5 iRule for UIE - Extracting a value from HTTP response payload/body

We are trying to write a iRule for the BIG-IP universal persistence module.
Our mission is to extract and persist from a HTTP response payload/body an application unique identifier (something like a seesionid for us).
Then use it in a consecutive HTTP requests.
Note, this unique identifier return in text/xml/soap-xml response formats and there is no cookie involve here.
We're having problem to write the TCL code for the extraction of our custom unique identifier from the HTTP response payload/body.
We have checked these manuals and did not find example for this kind of functionality:
https://devcentral.f5.com/wiki/iRules.HTTP_RESPONSE.ashx
https://devcentral.f5.com/wiki/iRules.HTTP__payload.ashx
Thanks.
Here's an example with jsession IDs that should get you started with basic persistence flow, and this example gives you an idea on how to work with payload data.

Apigee doesn't seem to support the OAuth 2 specification, is there a reason why?

We're making requests for bearer tokens using client_credentials OAuth 2 grant flow with Apigee. According to the spec:
4.4.2. Access Token Request
The client makes a request to the token endpoint by adding the
following parameters using the "application/x-www-form-urlencoded"
format per Appendix B with a character encoding of UTF-8 in the HTTP
request entity-body:
grant_type
REQUIRED. Value MUST be set to "client_credentials".
If we make a call however we get an error like this:
{"ErrorCode" : "invalid_request", "Error" :"Required param : grant_type"}
It seems that using Apigee we have to send grant_type as a query parameter.
Why is this? We have clients of Apigee that are unable to use OAuth libraries in their language of choice because of the way that Apigee deals with OAuth 2, and it would be good to know if there is by-design or not.
In addition it doesn't seem like it supports grant_type in the post body and sending id and key using basic auth.
Turns out you do not need to send in grant_type as a query parameter. There is a <GrantType> element in your GenerateAccessToken policy that takes in a variable. For instance, I can use the following:
<OAuthV2 name="GenerateAccessToken">
<DisplayName>GenerateAccessToken</DisplayName>
<FaultRules/>
<Properties/>
<!-- This policy generates an OAuth 2.0 access token using the password grant type -->
<Operation>GenerateAccessToken</Operation>
<!-- This is in millseconds -->
<ExpiresIn>1800000</ExpiresIn>
<Attributes/>
<SupportedGrantTypes>
<GrantType>password</GrantType>
</SupportedGrantTypes>
<GenerateResponse enabled="false">
<Format>FORM_PARAM</Format>
</GenerateResponse>
<GrantType>user.grant_type</GrantType>
<UserName>request.header.username</UserName>
<PassWord>request.header.password</PassWord>
</OAuthV2>
In this example, the grant_type is passed in as user.grant_type. But user.grant_type can be anything-- header, query param, form param, or even a hard-coded value. This way, you (the developer) are provided maximum flexibility on how you want to send in the grant_type.
Can you paste the exact API call that you are making (obviously you should obfuscate the key and secret)?
I'd like to understand what you say when you say "Apigee" -- it could mean API BAAS (https://api.usergrid.com) or a proxy that you defined using API services and attached an OAuth 2 policy to, or something else?

What are the characteristics of an OAuth token?

How many characters long can an oauth access token and oauth access secret be and what are the allowed characters? I need to store them in a database.
I am not sure there are any explicit limits. The spec doesn't have any.
That said, OAuth tokens are often passed as url parameters and so have some of the same limitations. ie need to be properly encoded, etc.
OAuth doesn't specify the format or content of a token. We simply use encrypted name-value pairs as token. You can use any characters in token but it's much easier to handle if the token is URL-safe. We achieve this by encoding the ciphertext with an URL-safe Base64.
As most people already pointed out. The OAuth specification doesn't give you exact directions but they do say...
cited from: https://datatracker.ietf.org/doc/html/draft-hammer-oauth-10#section-4.9
"Servers should be careful to assign
shared-secrets which are long enough,
and random enough, to resist such
attacks for at least the length of
time that the shared-secrets are
valid."
"Of course, servers are urged to err
on the side of caution, and use the
longest secrets reasonable."
on the other hand, you should consider the maximum URL length of browsers:
see: http://www.boutell.com/newfaq/misc/urllength.html
If you read the spec, it says,
The authorization server issues the registered client a client
identifier - a unique string representing the registration
information provided by the client. The client identifier is not a
secret; it is exposed to the resource owner, and MUST NOT be used
alone for client authentication. The client identifier is unique to
the authorization server.
The client identifier string size is left undefined by this
specification. The client should avoid making assumptions about the
identifier size. The authorization server SHOULD document the size
of any identifier it issues.
Second, Access Token should be sent as header, not as a URL param.
Authorization: Bearer < token>.
An OAuth token is conceptually an arbitrary-sized sequence of bytes, not characters. In URLs, it gets encoded using standard URL escaping mechanisms:
unreserved = ALPHA, DIGIT, '-', '.', '_', '~'
Everything not unreserved gets %-encoded.
I'm not sure whether you just talk about the oauth_token parameter that gets passed around. Usually, additional parameters need to be stored and transmitted as well, such as oauth_token_secret, oauth_signature, etc. Some of them have different data types, for example, oauth_timestamp is an integer representing seconds since 1970 (encoded in decimal ASCII digits).
Valid chars for OAuth token are limited by HTTP header value restrictions as OAuth token is frequently sent in HTTP header "Authorization".
Valid chars for HTTP headers are specified by https://www.rfc-editor.org/rfc/rfc7230#section-3.2.6. Alternatively you may check HTTP header validating code of some popular HTTP client libs, for example see Headers.checkNameAndValue() util of OkHttp framework: https://github.com/square/okhttp/blob/master/okhttp/src/main/java/okhttp3/Headers.java
And this is not all. I wouldn't include HTTP header separator (; and many others) and whitespace symbols (' ' and '\t') and double quote (") (see https://www.rfc-editor.org/rfc/rfc7230#section-3.2.6) as it would require to escape OAuth token before using in HTTP header. Frequently tokens are used by humans in curl test requests, and so good token generators don't add such characters. But you should check what characters may produce Oauth token generator with which your service is working before making any assumptions.
To be specific, even if Oauth spec doesn't say anything, if you are using java and mysql then it will be 16 characters as we generally generate the tokens using UUID and store it as BINARY(16) in the database. I know these details as I have recently done the development using OAuth.

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