# Authorization code grant flow without proof key for code exchange

# Introduction

While the traditional authorization code flow remains a valid method for web applications, it is highly recommended to adopt Proof Key for Code Exchange (PKCE). By using PKCE, you ensure a more robust and secure implementation of the OAuth 2.0 protocol.

But the OAuth 2.0 specification allows to obtain a token pair via authorization code flow even without PKCE as well. If the external system/application is unable to enhance to support PKCE, then this method can be used.

It consists of the following steps:

# Step 1: Authorizing the user

The URL of the Pagero Login page is:

https://sso.pageroonline.com/oauth/v2/oauth-authorize

Request method: GET

Required query parameters:

Parameter	Description
`response_type`	Should be set to `code` to generate an `authorization_code`.
`redirect_uri`	The client URI where the user will be redirected after successfully providing credentials. This URI must be the one that was agreed upon when the client was registered. Note: This URI should be URL-encoded with `UTF-8` to ensure it is correctly processed.
`client_id`	The client ID.

Optional query parameters:

Parameter	Description
`state`	Returned to the client in the final redirect to track the session or prevent unauthorized requests.
`scope`	The scopes must be separated by spaces. These scopes must be a subset of the scopes configured on the client. Possible values: - `all`: Default value - `openid`: If set, it will provide an additional `id_token` property along with the `access_token` and `refresh_token` in the response
`prompt`	Specifies whether the authorization server prompts the user login for re-authentication. Possible values: - `login`: Force the user to re-authenticate, ensuring that the person using the application is the legitimate owner of the account.

# Example

https://sso.pageroonline.com/oauth/v2/oauth-authorize?response_type=code&client_id=test-client&redirect_uri=https://urltoclient:4443

# Step 2: Obtaining authorization code

Upon successful login, the authorization_code is posted back as a query parameter to the url defined in the redirect_uri query parameter.

Response Structure:

Parameter	Description
`state`	Matches the value provided in the initial request. Used to align the request with the redirect response.
`iss`	Identifier of the authorization server where the request was sent.
`code`	A code used for authorization, utilized in the token request.

# Example

https://urltoclient:4443/?code=0F7ijeaW4BCwhvyg6ozY9PeLsFF6KUi1&state=exampleState&iss=https%3A%2F%2Fauthorization-server.com

# Step 3: Exchanging to a token

Using the authorization_code, it’s now possible to obtain an access_token and a refresh_token.

The URL for doing so is:

https://sso.pageroonline.com/oauth/v2/oauth-token

Request method: POST

Required parameters in application/x-www-form-urlencoded:

Parameter	Description
`grant_type`	Should be `authorization_code`.
`code`	The authorization code.
`redirect_uri`	Must be identical to the redirected uri that was provided in the first step above.
`client_id`*	The client ID.
`client_secret`*	The client secret.

Required headers (if not client_id and client_secret provided in the body):

Header	Description
`Authorization`	Authorization header for basic authorization, where the user should be the client id and password should be the client secret.

Response Structure:

Parameter	Description
`access_token`	A freshly generated access token
`refresh_token`	A freshly generated refresh token
`expires_in`	Time in seconds until expiration
`scope`	A string with space-separated values
`token_type`	Bearer or another type of token
`id_token`*	A signed JSON Web Token (JWT) containing user information like `email` and this is only present if the `scope` is set to `openid`

# Example with header option

Example with curl
curl https://sso.pageroonline.com/oauth/v2/oauth-token \
  -d grant_type=authorization_code \
  -d code=0F7ijeaW4BCwhvyg6ozY9PeLsFF6KUi1 \
  -d redirect_uri=https://urltoclient:4443 \
  --user 'client-id:client-secret'  

The response will contain a JSON body that looks like this (when scope is set to all):

{
  "token_type": "bearer",
  "access_token": "_0XBPWQQ_2a66dd33-e108-4dc3-b653-e71b9feae02e",
  "refresh_token": "_1XBPWQQ_e61b091b-9139-4268-a7c7-765d2d418d52",
  "scope": "",
  "claims": "publicid",
  "expires_in": 600
}

# Making an API request using an access token

When making an API request, the access token should be provided in an Authentication header as a bearer token.

Example with curl
curl https://api.pageroonline.com/someresource \
  -H 'Authorization: Bearer _0XBPWQQ_2a66dd33-e108-4dc3-b653-e71b9feae02e'