API keys in a header transported over network

Issue ID: v3-global-securityrequirement-apikey-inheader

Average severity: Medium

Description

The API accepts API keys that are transported in a header over the network. The credentials are sent over the network on each API call, over and over again, and are exposed to attack attempts to retrieve them.

For more details, see the OpenAPI Specification.

Example

The following is an example of how this type of risk could look in your API definition. Here, the authentication method is specified to use API keys in a header:

{  
    "servers": [
        {
            "url": "https://my.api.server.com/",
            "description": "API server"
        }
    ],
    // ...  
    "components": {
        "securitySchemes": {
            "apiKey": {
                "type": "apiKey",
                "name": "X-API-Key",
                "in": "header"
            }
        }
    },
    // ...
    "security": [
        {
            "apiKey": []
        }
    ]
}

Possible exploit scenario

Attackers can eavesdrop credentials transported over the network and try to intercept the traffic between the API consumer and your API to retrieve them. If they succeed, they can access all API operations protected with the same security requirement until the credentials are specifically revoked or changed. API keys have long lifetime providing extended opportunity for exploits.

Remediation

Use a more secure authentication method, like OAuth 2.0. It uses access tokens with limited lifetime and authorizations (the scopes) granted that the resource owner grants from an authorization server.

An API operation can be consumed only if the request includes an access token and the scopes of the token match the scopes that the API operation requires. Even if attackers successfully retrieved access tokens, they can only use the token on a subset of the API operation and for a limited time.

{  
    "servers": [
        {
            "url": "https://my.api.server.com/",
            "description": "API server"
        }
    ],
    // ...  
    "components": {
        "securitySchemes": {
            "OAuth2": {
                "type": "oauth2",
                "flows": {
                    "authorizationCode": {
                        "scopes": {
                            "write": "modify objects in your account",
                            "read": "read objects in your account"
                        },
                        "authorizationUrl": "https://example.com/oauth/authorize",
                        "tokenUrl": "https://example.com/oauth/token" 
                    }
                }
            }
        }
    },
    // ...
    "security": [
        {
        "OAuth2": [
                "write",
                "read"
            ]
        }
    ]
}