Sending credentials for unknown HTTP authentication method as cleartext allowed

Issue ID: v3-global-securityscheme-http-unknown-clear

Average severity: Minimal

Description

One or more global security schemes in your API allows setting HTTP authentication methods that are not included in IANA Authentication Scheme Registry and that accept credentials sent in cleartext over an unencrypted channel. Attackers can easily intercept API calls and retrieve the credentials. They can then use the credentials to make other API calls.

This is a potential risk, because the definition is in security schemes. However, it easily turns into an actual risk when the unsafe method is used in a security requirement.

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. The scheme myAuth defines a custom HTTP authentication method. The server object sets HTTP as the supported transportation protocol. This means that the API could accept an API call over an unencrypted HTTP connection, and use an unknown authentication method:

{  
    "servers": [
        {
            "url": "http://my.api.server.com/",
            "description": "API server"
        }
    ],
    // ...  
    "components": {
        "securitySchemes": {
            "myAuth": {
                "type": "http",
                "scheme": "foo"
            }
        }
    }
}

Possible exploit scenario

Attackers can intercept the credentials simply by listening to the network traffic in a public WiFi network. They could also use a traffic logging tool on a smartphone, computer, or browser, or sniff the traffic in the network to get the credentials. HTTP digest access authentication has become obsolete and insecure, with the long lifetime of credentials providing extended opportunity for exploits.

If the HTTP authentication you have set is not included in IANA Authentication Scheme Registry, it must be considered unknown, because it cannot be trusted to adhere to any recognized standard.

Using unknown HTTP authentication methods is risky, because it is unclear how thoroughly they have been vetted or tested. In addition, your API consumers do not know what your HTTP authentication means, or how it works.

Remediation

Set all server objects to support HTTPS only so that all traffic is encrypted.

Do not use HTTP authentication methods that are not included in IANA Authentication Scheme Registry.

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"
            ]
        }
    ]
}