内容简介:I tried to make this as understandable as possible for any party reading it which means that the wording, references, and terminology used may not reflect that of a technical paper or resource. Excuse me if you may for I wish all to understand this, and no
The OAuth Bible
I tried to make this as understandable as possible for any party reading it which means that the wording, references, and terminology used may not reflect that of a technical paper or resource. Excuse me if you may for I wish all to understand this, and not just those with a degree in understanding legal or technical jargon.
Created with love by Nijikokun @ Mashape, the team behing the OSS API management layer Kong , and Mashape Analytics for visualizing and monitoring API traffic.
Hey!Interested in simplifying the process to consume OAuth services like twitter, facebook, github, and thousands more? Check out Guardian , it was built with simplicity, security, and ease of use in mind, allowing you to consume OAuth in a single request.
Table Of Contents
Terminology / Reference
-
Signed / Signature
- String made up of several HTTP request elements in a single string.
These include the
Request Method
&
URL Query
&
Parameters
, which is then encrypted against the key which consists of: (consumer_secret
&
token_secret
). In some cases this may be the key, plaintext, or may use simply theconsumer_secret
, for RSA encryption. -
Consumer Secret
- Usually given by application as a secret token for starting the OAuth handshakes.
-
Consumer Key
- Key usually given along-side Consumer Secret for OAuth handshakes.
-
Nonce / UID
- Uniquely generated ID of a given length using the
a-zA-Z0-9
charset, by default these are usually32
characters long.
- Uniquely generated ID of a given length using the
-
OAuth Token
- This is a token sent by the server or endpoint. It can refer to either the Request or Access token.
-
OAuth Token Secret
- This is a secret generally sent with the response for a certain token. Used for exchanges / refreshing.
-
Query
- Part of the URL that contains key-value data invoked by the
?
symbol, the keys and values are seperated by the=
sign and each data-store is seperated by the&
symbol:?query=looks&like=this
- Part of the URL that contains key-value data invoked by the
-
Parameter / Argument
- These are snippets of information that have a name reference such as
oauth_token="helloWorld"
whereoauth_token
is the parameter or argument andhelloWorld
is the value.
- These are snippets of information that have a name reference such as
-
Plaintext
- Signature Encryption Method, Plain Text, as in Human Readable Text such as this is.
-
HMAC-SHA1 [ W ]
- Signature Encryption Method, Secure Hash Algorithm (1) Method, Encrypted Text
-
RSA-SHA1 [[W]( http://en.wikipedia.org/wiki/RSA_(algorithm) )]
- Signature Encryption Method, Secure Hash Algorithm (1) coupled with a public and private key. You may have seen this being used for your Github account at one point, also in SSH.
-
Service
- Provider of information, data-source, or supplying use. Twitter is an example of a service.
-
Signature Method
- OAuth Accepted Encryption method, one of the following: PLAINTEXT, HMAC-SHA1, and RSA-SHA1.
-
Value
- Information in relation to something such as a parameter.
-
URL / URI
- Location on the internet or resource locator.
Signed Requests
This section is in regards to OAuth 1.0
Signing requests is more than just the signature so in this section we will look at how the signature process should be handled and how each parameter should be used with references to flows. When signing requests the Application takes all the information it has been given, gathered, or generated, and places it in a single location. There are two ways of transporting this information, through the OAuth
header or the Query
string.
Before we can generate this string we must gather all the required parameters and their values, some of these are used inside of the string directly and others in-directly through the encryption or encoding of the signature.
Signature Base String
Gathering the Method
of the request, the URL
of the request (or in the case of OAuth Echo
the verifying credentials uri) and the Query String
joined together by the &
symbol would look like this without encryption (example from twitter ):
POST&https%3A%2F%2Fapi.twitter.com%2F1%2Fstatuses%2Fupdate.json&include_entities%3Dtrue%26oauth_consumer_key%3Dxvz1evFS4wEEPTGEFPHBog%26oauth_nonce%3DkYjzVBB8Y0ZFabxSWbWovY3uYSQ2pTgmZeNu2VS4cg%26oauth_signature_method%3DHMAC-SHA1%26oauth_timestamp%3D1318622958%26oauth_token%3D370773112-GmHxMAgYyLbNEtIKZeRNFsMKPR9EyMZeS9weJAEb%26oauth_version%3D1.0%26status%3DHello%2520Ladies%2520%252B%2520Gentlemen%252C%2520a%2520signed%2520OAuth%2520request%2521
Signing Key
The signature base
string is then encrypted with a salt called the signing key which is a joining of the OAuth Consumer Secret
and Token Secret
once again by the &
character like so:
Note:Sometimes in case of RSA and xAuth the signing key may only be the Consumer Secret
with an &
symbol appended or not. For more insights check out lines 233 & 238 of mashape-oauth/lib/oauth.js
kAcSOqF21Fu85e7zjz7ZN2U4ZRhfV3WpwPAoE3Z7kBw&LswwdoUaIvS8ltyTt5jkRh4J50vUPVVHtR2YPi5kE
Encoding the Signature
At last, we are able to encode our signature using these two strings of information. If you read the Terminology guide you would know that there are three ways we can do this. PLAINTEXT, HMAC, or RSA. Each method is slightly different from each other.
PLAINTEXT
Here we ignore any encoding and simply pass along the Signature Key
HMAC-SHA1
This encoding method outputs our key into binary which we update our base with, which after this step gets Base64 encoded into it's final signature string:
tnnArxj06cWHq44gCs1OSKk/jLY=
RSA-SHA1
On the more complex side of encoding and security we have the RSA method that we have to encode the generated private key
against our Signature Base
.
Note:Line 74 of mashape-oauth/tests/oauth.js may clear up how to use the generated private key to encode against the signature base.
Then on the service side they verify the public key that was generated along-side the private key against the encoded string passed as oauth_signature
.
OAuth Header
The OAuth header is a part of the signed request, it contains the oauth_signature
and oauth_signature_method
parameters and their values. It is a single string and separated generally by a comma (spaces are supported here by some services, stick to comma by default unless told otherwise by the service) and named Authorization
with OAuth
being the Bearer, in other flows this may change such as the OAuth Mac Bearer and other similar methods.
The header itself is built up by all the oauth_*
parameters sorted (by name, then some more complex things ). Here is an example taken from Twitter for getting a Request Token:
POST /oauth/request_token HTTP/1.1 User-Agent: themattharris' HTTP Client Host: api.twitter.com Accept: */* Authorization: OAuth oauth_callback="http%3A%2F%2Flocalhost%2Fsign-in-with-twitter%2F", oauth_consumer_key="cChZNFj6T5R0TigYB9yd1w", oauth_nonce="ea9ec8429b68d6b77cd5600adbbb0456", oauth_signature="F1Li3tvehgcraF8DMJ7OyxO4w9Y%3D", oauth_signature_method="HMAC-SHA1", oauth_timestamp="1318467427", oauth_version="1.0"
The oauth_callback
is what twitter will invoke or respond to when the authentication step happens, some services tell you they have successfully confirmed this information with a oauth_callback_confirmed
token (This should be the de facto situation).
Now, lets see the example response:
HTTP/1.1 200 OK Date: Thu, 13 Oct 2011 00:57:06 GMT Status: 200 OK Content-Type: text/html; charset=utf-8 Content-Length: 146 Pragma: no-cache Expires: Tue, 31 Mar 1981 05:00:00 GMT Cache-Control: no-cache, no-store, must-revalidate, pre-check=0, post-check=0 Vary: Accept-Encoding Server: tfe oauth_token=NPcudxy0yU5T3tBzho7iCotZ3cnetKwcTIRlX0iwRl0& oauth_token_secret=veNRnAWe6inFuo8o2u8SLLZLjolYDmDP7SzL0YfYI& oauth_callback_confirmed=true
Great, 200
response with the oauth_token
, oauth_token_secret
and oauth_callback_confirmed
parameters. This is perfect, now you can use the oauth_token_secret
for creating your signature for the access token and oauth_token
for authenticating the request.
Generally, the oauth_token
will be sent along as a query parameter ?oauth_token=[token goes here]
on the authenticate endpoint when doing a 3-Legged OAuth 1.0a
request which should give you back the oauth_token
and oauth_verifier
which then are used as well in your Access Token request [19] .
OAuth 1.0a (one-legged)
What is commonly known as two-legged is actually one legged, there is only one step, thus you are standing on one leg.
Note:Google requires an unorthodox non-oauth parameter that must be added to the query string of the url you are request called xoauth_requester_id
[ R ] this has also been deprecated in favor of OAuth2.
- Application sends a signed request to the Service giving it:
-
oauth_token
Empty String -
oauth_consumer_key
-
oauth_timestamp
-
oauth_nonce
-
oauth_signature
-
oauth_signature_method
-
oauth_version
Optional
-
- Service Validates and Grants Access to Resources.
- Application Utilizes Requested Resources
This is probably the quickest method of consuming an OAuth implementation, however it comes with a few security drawbacks. You can decide for yourself whether it is the best for your application.
OAuth 1.0a (two-legged)
The real two-legged OAuth implementation, so lucrative it's like finding a diamond in the rough. Here we also avoid the user authentication step but follow the other flows of OAuth.
- Application sends a signed request for a Request Token:
-
oauth_consumer_key
-
oauth_timestamp
-
oauth_nonce
-
oauth_signature
-
oauth_signature_method
-
oauth_version
Optional
-
- Grants application Request Token:
oauth_token oauth_token_secret
- Exchange Request Token for Access Token, signed request
-
oauth_token
Request Token -
oauth_consumer_key
-
oauth_timestamp
-
oauth_nonce
-
oauth_signature
-
oauth_signature_method
-
oauth_version
-
- Service grants Access Token & Token Secret (same arguments generally as Step 2)
- Application uses
oauth_token
&oauth_token_secret
to access protected resources.
Here is the actual flow of OAuth 1.0a 2-legged, here we can see the extra security measures in place to make sure a secure access connection has been made without bothering the user to authorize details.
OAuth 1.0a (three-legged)
This flow is the full experience, the grand finale, the whole shebang. It's the full-flow of OAuth 1.0a, and the most complex, excluding the other two variants on it. The user interaction in the middle of the flow is usually what causes most confusion.
- Application sends a signed request for a Request Token:
-
oauth_consumer_key
-
oauth_timestamp
-
oauth_nonce
-
oauth_signature
-
oauth_signature_method
-
oauth_version
Optional -
oauth_callback
-
- Grants application Request Token:
oauth_token oauth_token_secret oauth_callback_confirmed
- Send user to authorize url using:
-
oauth_token
-
- Prompts user to authorize / grant access
- User grants access
- Directs back to application with:
oauth_token oauth_verifier
- Exchange Request Token / Verifier for Access Token, signed request
-
oauth_token
Request Token; -
oauth_consumer_key
-
oauth_timestamp
-
oauth_nonce
-
oauth_signature
-
oauth_signature_method
-
oauth_version
-
oauth_verifier
-
- Service grants Access Token & Token Secret (same arguments generally as Step 2)
- Application uses
oauth_token
&oauth_token_secret
to access protected resources.
Note:In Step 6 if oauth_verifier
has not been set, this is a failed OAuth 1.0a 3-Legged implementation and probably only requires the oauth_token
to be sent. Rarely seen but they exist.
The most secure OAuth implementation so far, yet a little more complicated seeing as the user is a part of the handshake and must interact with interfaces during the transactions.
OAuth 1.0a (Echo)
Not necessarily the most common of OAuth implementations, but it exists. Created by Raffi from twitter it uses two extra headers in the initial request token step to validate your user on their behalf by delegation.
So essentially the Service (third-party, delegator) will authenticate and verify the user against the originating service such as Twitter (Origin Service).
-
Application sends a signed request along with any data and:
-
oauth_consumer_key
-
oauth_timestamp
-
oauth_nonce
-
oauth_signature
-
oauth_signature_method
-
oauth_version
Optional -
oauth_callback
Along with two additional headers:
X-Auth-Service-Provider X-Verify-Credentials-Authorization
-
-
Service takes the additional headers and validates against the Origin Service.
-
Service then validates against given information and returns protected resource information. This could be storing an image, generating the url and returning that information.
OAuth 1.0a (xAuth)
xAuth is a way for desktop and mobile apps to get an OAuth access token from a user’s email and password, and it is still OAuth. So the third-party will ask for your credentials on the origin service to authenticate with.
The xAuth process will give back read-only, or read-write access tokens. Some limitations can apply, as in the Twitter spec Direct Messages read access is not provided and you must use the full OAuth flow (three-legged).
Note:The user's credentials should never be kept by the application requesting them.
-
Application Requests User Credentials
-
Application creates signed request for Access Token:
-
oauth_consumer_key
-
oauth_timestamp
-
oauth_nonce
-
oauth_signature
-
oauth_signature_method
-
oauth_version
Optional -
oauth_callback
Along with additional parameters:
-
x_auth_mode
=client_auth
-
x_auth_username
-
x_auth_password
-
x_auth_permission
Optional; Scope of the requested token [17]
-
-
Service validates user details and grants Access Token
oauth_token oauth_token_secret
-
Application uses Access Token to retrieve protected resources.
OAuth 2 (two-legged)
By far the easiest to explain, here we have what is called a Client Credentials authorization flow. [20, 4.4] Which is also basically just the Resource Owner Password flow without the username and password appended to the encoded query passed along as the body, unless the service states through the url in which case is wrong.
NoteIf you are using basic, you will need to additionally pass along an Authorization
header with the bearer type as Basic
and as the value you use client_id
:
client_secret
Base64 encoded.
Authorization: Basic Base64(client_id:client_secret)
Client Credentials
- Application makes request to Service:
-
grant_type
=client_credentials
If you aren't using the Authorization
header:
client_id client_secret
- Service responds with Access Token:
access_token expires_in token_type
Resource Owner Password
Basically OAuth 1.0a Echo… without the signing and complications. Let's do this.
-
Application request credentials, shown below , from resource owner (also known as the user).
username password
-
Application makes request to Service using the given credentials as a query string for the body:
-
grant_type
=password
-
username
-
password
It should look like this:
-
grant_type=password&username=my_username&password=my_password
If you aren't using the `Authorization` header, these must be passed as well: - `client_id` - `client_secret` Which would become: ``` grant_type=password&username=my_username&password=my_password&client_id=random_string&client_secret=random_secret
- Service responds with Access Token details and expiration information:
access_token expires_in token_type
OAuth 2 (three-legged)
OAuth2 three-legged cuts out a lot of clutter just like the two-legged, no longer are things so complex with signing your requests.
Fun Fact:Scope by spec was to be space seperated (i.e. user pull-request
) to which nobody followed and we are now left in a state of constant wonder as to what the next api we tackle uses.
-
Application redirects User to Service for Authorization:
-
client_id
-
redirect_uri
-
response_type
[20, 4.1.1] -
state
Optional; Unique identifier to protect against CSRF [25] -
scope
Optional; what data your application can access.
Example Authorization URL (Not-Encoded for Readability):
-
https://oauth_service/login/oauth/authorize?client_id=3MVG9lKcPoNINVB&redirect_uri= http://localhost/oauth/code_callback&scope=user ``` 2. User logs into the Service and grants Application access. 3. Service redirects User back to the redirect_uri
with: - `code` - `state` 4. Application takes the `code` and exchanges it for an Access Token: - `client_id` - `client_secret` - `code` - `redirect_uri` Optional; see [20, 4.1.3] - `grant_type` = `"authorization_code"` [20, 4.1.3] 2. If `client_id` and `client_secret` are valid the Service will invoke a callback on `redirect_url` that contains an `access_token`: - `access_token` - `expires_in` - `refresh_token` 3. Application stores `access_token` to use in subsequent requests in various manners dependent on the Service. - Generally this value is stored in a session or cookie, and then placed into the request as an `Authorization: [Bearer] access_token` header string where `[Bearer]` is the Header Authorization Bearer Name it could be Bearer, OAuth, MAC, etc…
OAuth 2 (refresh token)
In OAuth2 the access_token
sometimes, which is most of the time, has a limited lifetime expectancy. We can assume by the expires_in
parameter passed along at the Access Token response stage whether it will live forever or decay in a certain amount of time.
If an expired token is used the Service will respond with a Session expired or Invalid response error. This means we must use the refresh_token
along with a few other previously obtained parameters to generate a new one. A lot easier than the whole flow.
- Create request to Service Refresh Token URI:
-
grant_type
="refresh_token"
-
scope
Optional; Cannot have any new scopes not previously defined. -
refresh_token
-
client_id
-
client_secret
-
- Service validates and responds with the following parameters:
-
access_token
-
issued_at
-
refresh_token
Optional; Server MAY revoke and reissue the refresh token
-
Tips & Tricks
Generating Access Token & Refresh Key
Instead of encrypting information and using this as a sort of reversible string it's a lot more secure to simply utilize the same method of generation as the nonce
string, a uuid. Randomly selected characters in a specific length.
Example
var OAuth = require('mashape-oauth').OAuth, access_token = OAuth.nonce(/* Length, Default 32 */);
Tools
- Guardian - Simplify consuming OAuth with a single request
- Grant - Authentication Middleware for Express (built on Guardian) by @simov
- oauthd - OAuth Provider Server, plugins engineered towards provider specifics.
Sources
Here is a long, windy list of places where I tracked down specific information regarding certain legs or auth specification excluding the original RFC and it's revisions.
- Authorizing with OAuth - Flickr Documentation
- OAuth on Bitbucket - Bitbucket Documentation
- OAuth Documentation - Twitter Documentation
- OAuth Extended Flows
- 2-Legged OAuth - OAuth-PHP
- OAuth for Consumer Requests
- OAuth Example - term.ie
- OAuth 1.0 Guide - Heuniverse
- OAuth 1.0a Diagram
- OAuth Wiki
- 2-Legged OAuth 1.0 & 2.0 - DZone
- OAuth & OAuth2 - Google Documentation
- What is 2-legged OAuth? - Nerdbank
- List of Service Providers - Wikipedia
- OAuth Echo - mobypicture
- OAuth Echo - Twitter
- Advanced API - Vimeo Developer();
- About xAuth - Twitter xAuth Documentation
- Implementing Sign-in - Twitter Sign-in Documentation
- RFC6749 - IETF
- Web Application Flow - Github OAuth2
- OAuth2 Quickstart - Salesforce
- Authentication Mechanisms - Geoloqi
- Understanding Web Server OAuth Flow - Salesforce
- CSRF & OAuth2 - Springsource
- OAuth v2-31 - IETF
- Resource Owner Flow - Hybris
以上所述就是小编给大家介绍的《The OAuth Bible [2016]》,希望对大家有所帮助,如果大家有任何疑问请给我留言,小编会及时回复大家的。在此也非常感谢大家对 码农网 的支持!
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