JSONString Parameters

Mythic 4.0 adds the JSONString parameter type for payload build parameters and C2 profile parameters. The stored value remains a JSON string, while json_string_schema lets the Create Payload UI offer synchronized Visual and Source editors.

The schema is declarative UI metadata, not JSON Schema draft-07/2020-12. Use the supported vocabulary below.

Python example

from mythic_container.PayloadBuilder import BuildParameter, BuildParameterType

http_config_schema = {
    "type": "object",
    "label": "HTTP Configuration",
    "fields": [
        {"name": "callback_host", "type": "string", "label": "Callback Host"},
        {"name": "callback_port", "type": "number", "label": "Port"},
        {"name": "use_ssl", "type": "boolean", "label": "Use TLS"},
        {
            "name": "method",
            "type": "enum",
            "label": "HTTP Method",
            "choices": ["GET", "POST"],
            "choices_display_names": {"GET": "HTTP GET", "POST": "HTTP POST"},
        },
        {
            "name": "headers",
            "type": "string_map",
            "label": "Headers",
            "key_label": "Header",
            "value_label": "Value",
        },
        {
            "name": "client_certificate",
            "type": "string",
            "label": "Client certificate",
            "show_when": {"field": "use_ssl", "in": [True]},
        },
    ],
}

build_parameters = [
    BuildParameter(
        name="http_config",
        display_name="HTTP Configuration",
        parameter_type=BuildParameterType.JSONString,
        default_value='{"callback_host":"https://example.com","callback_port":443,"use_ssl":true,"method":"POST","headers":{}}',
        json_string_schema=http_config_schema,
    )
]

The same schema can be supplied to C2ProfileParameter(..., parameter_type=ParameterType.JSONString, json_string_schema=http_config_schema).

Go example

configSchema := map[string]interface{}{
    "type":  "object",
    "label": "HTTP Configuration",
    "fields": []map[string]interface{}{
        {"name": "callback_host", "type": "string", "label": "Callback Host"},
        {"name": "callback_port", "type": "number", "label": "Port"},
        {"name": "use_ssl", "type": "boolean", "label": "Use TLS"},
        {
            "name": "headers",
            "type": "string_map",
            "label": "Headers",
            "key_label": "Header",
            "value_label": "Value",
        },
    },
}

parameter := agentstructs.BuildParameter{
    Name:             "http_config",
    DisplayName:      "HTTP Configuration",
    ParameterType:    agentstructs.BUILD_PARAMETER_TYPE_JSON_STRING,
    DefaultValue:     `{"callback_host":"https://example.com","callback_port":443,"use_ssl":true,"headers":{}}`,
    JsonStringSchema: configSchema,
}

For a C2 profile, use c2structs.C2_PARAMETER_TYPE_JSON_STRING and the JsonStringSchema field.

Schema vocabulary

`type`	Stored JSON value	Important fields
`object`	object	`fields`, where each field has a unique `name`
`array`	array	`items` schema
`enum`	one primitive value	`choices`, optional `choices_display_names`
`string`	string	optional `placeholder`
`number`	number	—
`boolean`	boolean	—
`string_map`	object of string keys/values	optional `key_label`, `value_label`

All nodes can include label and description. A field inside an object’s fields can include:

show_when: {field: "sibling_name", in: [values...]} to control visibility;
placeholder_when: {field: "sibling_name", map: {value: "placeholder"}} for a contextual string placeholder.

Hidden fields keep their current value. Consumers should tolerate a value that is present even when its editor control is hidden.

Round-trip behavior

The Source editor holds the exact string. Switching to Visual calls JSON.parse; invalid JSON blocks the switch. Each visual change is serialized back with formatted JSON. The top-level schema should therefore describe the JSON document itself, normally an object. The UI seeds missing values as {} for objects and maps, [] for arrays, "" for strings, 0 for numbers, false for booleans, and the first enum choice when available.

​Python example

​Go example

​Schema vocabulary

​Round-trip behavior

Python example

Go example

Schema vocabulary

Round-trip behavior