What are the characteristics of an OAuth token? - oauth

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.

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.

Should the WWW-Authenticate realm parameter be encoded?

When building the WWW-Authenticate header value for OAuth/OAuth1a it calls for percent-encoding the parameters. The spec and implementations are ambiguous on whether the realm parameter should be percent-encoded or not.
Section 5.4.1. Authorization Header of the spec reads:
The OAuth Protocol Parameters are sent in the Authorization header the
following way:
Parameter names and values are encoded per Parameter Encoding.
For each parameter, the name is immediately followed by an '=' character (ASCII code 61), a '"' character (ASCII code 34), the parameter value (MAY be empty), and another '"' character (ASCII code 34).
Parameters are separated by a comma character (ASCII code 44) and OPTIONAL linear whitespace per [RFC2617].
The OPTIONAL realm parameter is added and interpreted per [RFC2617], section 1.2.
For example:
Authorization: OAuth realm="http://sp.example.com/",
oauth_consumer_key="0685bd9184jfhq22",
oauth_token="ad180jjd733klru7",
oauth_signature_method="HMAC-SHA1",
oauth_signature="wOJIO9A2W5mFwDgiDvZbTSMK%2FPY%3D",
oauth_timestamp="137131200",
oauth_nonce="4572616e48616d6d65724c61686176",
oauth_version="1.0"
If these steps are meant to be taken in order, then it seems like only the OAuth specific parameters are meant to be url encoded.
If these steps are not meant to be taken in order, then maybe the realm parameter is included in step 1. However, the WWW-Authenticate header example in the OAuth1a spec shows the realm as realm="http://sp.example.com/" which is not percent-encoding the colon or the slashes.
To make matters more confusing, it seems this varies from implementation to implementation. Many OAuth implementations give no special treatment to the parameters and simply percent-encode all of them, but other OAuth implementations give special treatment to the realm parameter and exclude it from percent-encoding.
What is the correct behavior for adding the realm parameter to the WWW-Authenticate header?
The WWW-Authenticate header and the realm parameter, in particular, are defined by rfc2617 and rfc7235, which do not say anything about encoding. rfc7235 shows an example where the spaces in "Login to \"apps\"" are not percent-encoded.
rfc2617 and rfc7235 are the authority on the WWW-Authenticate header and realm parameter while the OAuth1a spec is only the authority on the additional OAuth specific parameters. Therefore the realm parameter should not be percent-encoded and section 5.4.1 of the OAuth1a spec should be interpreted to only be talking about OAuth Protocol Parameters with regards to percent-encoding.

International characters resulting in bad OAuth 1.0 body hash

I'm getting a body hash mismatch when the POST body of an XML web service request contains international characters.
From what I've read, it sounds like international characters in a POST body have to be encoded before calculating the OAuth body hash. UTF-8 for CAFÉ of "CAF%c3%89" doesn't seem to work with the MasterCard Match web service. I'm having trouble with the tool we're using (iWay Service Manager) re-interpreting "CAFÉ" back to "CAFÉ". Before I figure out how to squeeze an encoder in before the OAuth step, I was hoping to confirm with someone who had dealt with this issue. What is the proper encoding to use on a POST body with international characters (or is my problem likely to be something else)?
For calculating MasterCard OAuth body hash, the recommended encoding is UTF-8. Also the Core SDK made available by MasterCard uses UTF-8 encoder to encode oauth_body_hash.

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?

Oauth 2 - params ordering and signature integrity

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.

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