Source uses tor2web out of scope

THREAT75 · Out of scope: Outside what this threat model covers. · Defined in catalog.py:1321

Risk: High impact × Medium likelihood = 9 high
After mitigations: High impact × Low likelihood = 6 medium

A malicious operator or compromised Tor2Web relay may be in a position to de-anonymise a source or potential source and inspect contents of the communication between Source interface and Source

Threat actors: Nation State / Law Enforcement Large Corporation

Mitigations

Mitigation	Status
Warning displayed when Tor2Web headers are present MITIG124	implemented

Possible further mitigations

Source guide explains Tor2Web issues MITIG125 proposed
Support for HTTPS on source interface MITIG6 optional

Residual risk

The message is shown when a user already reached the Tor2Web service, it's already too late. A malicious or compromised Tor2Web relay could log activity and deanonymise the source.

Where it applies

Applies to 1 component in 1 scenario.

Source Tor Browser Source Area

Source discovery and OPSEC · Source Tor Browser

digraph tm {
    graph [
        fontname = Arial;
        fontsize = 14;
    ]
    node [
        fontname = Arial;
        fontsize = 14;
    ]
    edge [
        fontname = Arial;
        fontsize = 12;
    ]
    nodesep = 1;

    subgraph cluster_boundary_External_Services {
        graph [
            fontsize = 10;
            fontcolor = black;
            style = dashed;
            color = firebrick2;
            label = <<i>External Services</i>>;
        ]

        component_Landing_page_External_Services [
            shape = circle;
            color = black;
            fontcolor = black;
            label = "Landing page";
            URL = "component_Landing_page.html";
            tooltip = "Landing page";
            margin = 0.02;
        ]

        component_SecureDrop_org_directory_External_Services [
            shape = circle;
            color = black;
            fontcolor = black;
            label = "SecureDrop.org\ndirectory";
            URL = "component_SecureDrop_org_directory.html";
            tooltip = "SecureDrop.org directory";
            margin = 0.02;
        ]

    }

    subgraph cluster_boundary_SecureDrop_Area {
        graph [
            fontsize = 10;
            fontcolor = black;
            style = dashed;
            color = firebrick2;
            label = <<i>SecureDrop Area</i>>;
        ]

        component_Dedicated_Hardware_Firewall_SecureDrop_Area [
            shape = circle;
            color = black;
            fontcolor = black;
            label = "Dedicated\nHardware\nFirewall";
            URL = "component_Dedicated_Hardware_Firewall.html";
            tooltip = "Dedicated Hardware Firewall";
            margin = 0.02;
        ]

    }

    subgraph cluster_boundary_Source_Area {
        graph [
            fontsize = 10;
            fontcolor = black;
            style = dashed;
            color = firebrick2;
            label = <<i>Source Area</i>>;
        ]

        actor_Source_Source_Area [
            shape = square;
            color = black;
            fontcolor = black;
            label = "Source";
            URL = "component_Source.html";
            tooltip = "Source";
            margin = 0.02;
        ]

        component_Source_Tor_Browser_Source_Area [
            shape = circle;
            color = black;
            fontcolor = black;
            label = "Source Tor\nBrowser";
            URL = "component_Source_Tor_Browser.html";
            tooltip = "Source Tor Browser";
            margin = 0.02;

            style = "filled";

            fillcolor = "#c0392b";

            fontcolor = "white";

            class = "highlighted";
        ]

        component_Source_environment_Source_Area [
            shape = circle;
            color = black;
            fontcolor = black;
            label = "Source\nenvironment";
            URL = "component_Source_environment.html";
            tooltip = "Source environment";
            margin = 0.02;
        ]

    }

    actor_Source_Source_Area -> component_Source_environment_Source_Area [        color = black;        fontcolor = black;        dir = forward;        label = "1. Research / browse";    ]
    component_Source_environment_Source_Area -> component_SecureDrop_org_directory_External_Services [        color = black;        fontcolor = black;        dir = forward;        label = "2. Check directory";    ]
    component_Source_environment_Source_Area -> component_Landing_page_External_Services [        color = black;        fontcolor = black;        dir = forward;        label = "3. Visit landing\npage";    ]
    actor_Source_Source_Area -> component_Source_Tor_Browser_Source_Area [        color = black;        fontcolor = black;        dir = forward;        label = "4. Open Tor Browser";    ]
    component_Source_Tor_Browser_Source_Area -> component_Dedicated_Hardware_Firewall_SecureDrop_Area [        color = black;        fontcolor = black;        dir = forward;        label = "5. Connect to onion";    ]
}

Notes

Existing mitigations: Warning message for tor2web user https://github.com/freedomofpress/securedrop/commit/b40ec26ee2f262585b852e6a78e6f8ac98fca24d (MITIG124). Further mitigations: Source guide should be updated to strongly discourage the use of Tor2Web (MITIG125). The confidentiality risk could be mitigated by using HTTPS on the source interface (MITIG6). Automated test for mitigation: No.

How this threat is matched

Listed for these components. A boundary covers every component inside it.