Attacker obtains code execution in the GPG VM partially mitigated

THREATQW6 · Partially mitigated: Some controls are in place, but the risk is still too high. · Defined in catalog.py:3061

Risk: High impact × Low likelihood = 6 medium
After mitigations: Medium impact × Very Low likelihood = 2 low

How statuses and scores work

An attacker with code execution on GPG VM could exfiltrate the GPG submission key or perform arbitrary decryptions.

Threat actors: Nation State / Law Enforcement Large Corporation

Mitigations

No mitigations in place.

Possible further mitigations

Use hardware token to store submission key MITIGQW8 proposed
Remove applications e.g. Tor Browser in Journalist VM (proxy VM) MITIGQW4 proposed
Careful validation in SDK MITIGQW11 proposed
Default Qubes-RPC deny policy MITIGQW15 implemented
Sanitize/validate GPG payload in sd-svs prior to sending to sd-gpg (https://github.com/freedomofpress/securedrop-client/issues/433) MITIGQW16 proposed

Residual risk

In the event of a cross-vm attack or dom0 compromise, an attacker would be able to decrypt submissions or exfiltrate private keys.

Where it applies

Applies to 1 component in 2 scenarios.

sd-gpg Workstation VMs

Workstation: reading submissions · sd-gpg

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

    subgraph cluster_boundary_Application_Server {
        graph [
            fontsize = 10;
            fontcolor = black;
            style = dashed;
            color = firebrick2;
            label = <<i>Application Server</i>>;
        ]

        component_Journalist_Interface_Application_Server [
            shape = circle;
            color = black;
            fontcolor = black;
            label = "Journalist\nInterface";
            URL = "component_Journalist_Interface.html";
            tooltip = "Journalist Interface";
            margin = 0.02;
        ]

    }

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

        subgraph cluster_boundary_Workstation_VMs {
            graph [
                fontsize = 10;
                fontcolor = black;
                style = dashed;
                color = firebrick2;
                label = <<i>Workstation VMs</i>>;
            ]

            component_sd_app__SecureDrop_Client__Workstation_VMs [
                shape = circle;
                color = black;
                fontcolor = black;
                label = "sd-app\n(SecureDrop\nClient)";
                URL = "component_sd_app__SecureDrop_Client_.html";
                tooltip = "sd-app (SecureDrop Client)";
                margin = 0.02;
            ]

            component_sd_gpg_Workstation_VMs [
                shape = circle;
                color = black;
                fontcolor = black;
                label = "sd-gpg";
                URL = "component_sd_gpg.html";
                tooltip = "sd-gpg";
                margin = 0.02;

                style = "filled";

                fillcolor = "#c0392b";

                fontcolor = "white";

                class = "highlighted";
            ]

            component_sd_log_Workstation_VMs [
                shape = circle;
                color = black;
                fontcolor = black;
                label = "sd-log";
                URL = "component_sd_log.html";
                tooltip = "sd-log";
                margin = 0.02;
            ]

            component_sd_proxy_Workstation_VMs [
                shape = circle;
                color = black;
                fontcolor = black;
                label = "sd-proxy";
                URL = "component_sd_proxy.html";
                tooltip = "sd-proxy";
                margin = 0.02;
            ]

            component_sd_viewer__disposable_VMs__Workstation_VMs [
                shape = circle;
                color = black;
                fontcolor = black;
                label = "sd-viewer\n(disposable VMs)";
                URL = "component_sd_viewer__disposable_VMs_.html";
                tooltip = "sd-viewer (disposable VMs)";
                margin = 0.02;
            ]

            component_sys_firewall_Workstation_VMs [
                shape = circle;
                color = black;
                fontcolor = black;
                label = "sys-firewall";
                URL = "component_sys_firewall.html";
                tooltip = "sys-firewall";
                margin = 0.02;
            ]

            component_sys_net_Workstation_VMs [
                shape = circle;
                color = black;
                fontcolor = black;
                label = "sys-net";
                URL = "component_sys_net.html";
                tooltip = "sys-net";
                margin = 0.02;
            ]

        }

    }

    actor_Journalist_ [
        shape = square;
        color = black;
        fontcolor = black;
        label = "Journalist";
        URL = "component_Journalist.html";
        tooltip = "Journalist";
        margin = 0.02;
    ]

    actor_Journalist_ -> component_sd_app__SecureDrop_Client__Workstation_VMs [        color = black;        fontcolor = black;        dir = forward;        label = "1. Use the client";    ]
    component_sd_app__SecureDrop_Client__Workstation_VMs -> component_sd_proxy_Workstation_VMs [        color = black;        fontcolor = black;        dir = forward;        label = "2. Journalist API\nrequest";    ]
    component_sd_proxy_Workstation_VMs -> component_sys_firewall_Workstation_VMs [        color = black;        fontcolor = black;        dir = forward;        label = "3. Route via\nfirewall";    ]
    component_sys_firewall_Workstation_VMs -> component_sys_net_Workstation_VMs [        color = black;        fontcolor = black;        dir = forward;        label = "4. Route to network";    ]
    component_sys_net_Workstation_VMs -> component_Journalist_Interface_Application_Server [        color = black;        fontcolor = black;        dir = forward;        label = "5. Reach the\nJournalist Interface";    ]
    component_Journalist_Interface_Application_Server -> component_sys_net_Workstation_VMs [        color = black;        fontcolor = black;        dir = forward;        label = "6. Encrypted\nsubmissions";    ]
    component_sd_proxy_Workstation_VMs -> component_sd_app__SecureDrop_Client__Workstation_VMs [        color = black;        fontcolor = black;        dir = forward;        label = "7. Relay to client";    ]
    component_sd_app__SecureDrop_Client__Workstation_VMs -> component_sd_gpg_Workstation_VMs [        color = black;        fontcolor = black;        dir = forward;        label = "8. Decrypt";    ]
    component_sd_app__SecureDrop_Client__Workstation_VMs -> component_sd_viewer__disposable_VMs__Workstation_VMs [        color = black;        fontcolor = black;        dir = forward;        label = "9. Open a file";    ]
    component_sd_app__SecureDrop_Client__Workstation_VMs -> component_sd_log_Workstation_VMs [        color = black;        fontcolor = black;        dir = forward;        label = "10. Send logs";    ]
}

Workstation: boot, provisioning and updates · sd-gpg

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_FPF_apt_repository_External_Services [
            shape = circle;
            color = black;
            fontcolor = black;
            label = "FPF apt\nrepository";
            URL = "component_FPF_apt_repository.html";
            tooltip = "FPF apt repository";
            margin = 0.02;
        ]

    }

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

        subgraph cluster_boundary_Workstation_VMs {
            graph [
                fontsize = 10;
                fontcolor = black;
                style = dashed;
                color = firebrick2;
                label = <<i>Workstation VMs</i>>;
            ]

            component_sd_gpg_Workstation_VMs [
                shape = circle;
                color = black;
                fontcolor = black;
                label = "sd-gpg";
                URL = "component_sd_gpg.html";
                tooltip = "sd-gpg";
                margin = 0.02;

                style = "filled";

                fillcolor = "#c0392b";

                fontcolor = "white";

                class = "highlighted";
            ]

        }

        component_Qubes_OS_and_Xen_SecureDrop_Workstation [
            shape = circle;
            color = black;
            fontcolor = black;
            label = "Qubes OS and Xen";
            URL = "component_Qubes_OS_and_Xen.html";
            tooltip = "Qubes OS and Xen";
            margin = 0.02;
        ]

        component_Workstation_bootloader_SecureDrop_Workstation [
            shape = circle;
            color = black;
            fontcolor = black;
            label = "Workstation\nbootloader";
            URL = "component_Workstation_bootloader.html";
            tooltip = "Workstation bootloader";
            margin = 0.02;
        ]

        component_Workstation_firmware_SecureDrop_Workstation [
            shape = circle;
            color = black;
            fontcolor = black;
            label = "Workstation\nfirmware";
            URL = "component_Workstation_firmware.html";
            tooltip = "Workstation firmware";
            margin = 0.02;
        ]

        component_Workstation_hardware_SecureDrop_Workstation [
            shape = circle;
            color = black;
            fontcolor = black;
            label = "Workstation\nhardware";
            URL = "component_Workstation_hardware.html";
            tooltip = "Workstation hardware";
            margin = 0.02;
        ]

        component_Workstation_provisioning_code_SecureDrop_Workstation [
            shape = circle;
            color = black;
            fontcolor = black;
            label = "Workstation\nprovisioning\ncode";
            URL = "component_Workstation_provisioning_code.html";
            tooltip = "Workstation provisioning code";
            margin = 0.02;
        ]

        component_dom0_SecureDrop_Workstation [
            shape = circle;
            color = black;
            fontcolor = black;
            label = "dom0";
            URL = "component_dom0.html";
            tooltip = "dom0";
            margin = 0.02;
        ]

    }

    actor_Administrator_ [
        shape = square;
        color = black;
        fontcolor = black;
        label = "Administrator";
        URL = "component_Administrator.html";
        tooltip = "Administrator";
        margin = 0.02;
    ]

    actor_Journalist_ [
        shape = square;
        color = black;
        fontcolor = black;
        label = "Journalist";
        URL = "component_Journalist.html";
        tooltip = "Journalist";
        margin = 0.02;
    ]

    actor_Journalist_ -> component_Workstation_hardware_SecureDrop_Workstation [        color = black;        fontcolor = black;        dir = forward;        label = "1. Power on";    ]
    component_Workstation_hardware_SecureDrop_Workstation -> component_Workstation_firmware_SecureDrop_Workstation [        color = black;        fontcolor = black;        dir = forward;        label = "2. Start firmware";    ]
    component_Workstation_firmware_SecureDrop_Workstation -> component_Workstation_bootloader_SecureDrop_Workstation [        color = black;        fontcolor = black;        dir = forward;        label = "3. Load bootloader";    ]
    component_Workstation_bootloader_SecureDrop_Workstation -> component_Qubes_OS_and_Xen_SecureDrop_Workstation [        color = black;        fontcolor = black;        dir = forward;        label = "4. Boot Qubes";    ]
    component_Qubes_OS_and_Xen_SecureDrop_Workstation -> component_dom0_SecureDrop_Workstation [        color = black;        fontcolor = black;        dir = forward;        label = "5. Start dom0";    ]
    actor_Administrator_ -> component_Workstation_provisioning_code_SecureDrop_Workstation [        color = black;        fontcolor = black;        dir = forward;        label = "6. Install and\nconfigure";    ]
    component_Workstation_provisioning_code_SecureDrop_Workstation -> component_dom0_SecureDrop_Workstation [        color = black;        fontcolor = black;        dir = forward;        label = "7. Apply salt states";    ]
    component_dom0_SecureDrop_Workstation -> component_sd_gpg_Workstation_VMs [        color = black;        fontcolor = black;        dir = forward;        label = "8. Provide secret\nkeys";    ]
    component_dom0_SecureDrop_Workstation -> component_FPF_apt_repository_External_Services [        color = black;        fontcolor = black;        dir = forward;        label = "9. Fetch updates";    ]
    component_FPF_apt_repository_External_Services -> component_dom0_SecureDrop_Workstation [        color = black;        fontcolor = black;        dir = forward;        label = "10. Signed packages";    ]
}

Notes

Existing mitigations: sd-gpg vm has a limited attack surface as it only stores GPG keys and performs decryptions of SecureDrop-generated gzip archives through the Qubes split-gpg feature. Qubes-rpc policies restrict only sd-app from accessing this VM, all other requests are denied by default. Decrypted Gzip files are immediately sent to another vm for processing/display. GPG VM does not have any network connectivity. Further mitigations: - Use hardware token (yubikey, nitrokey) (MITIGQW8) to prevent exporting the key. - Consider using a more stripped down Template (kernel, OS) to reduce attack surface (MITIGQW4) - Validate that GPG files are valid (to potentially prevent exploitation of a GPG vulnerability by not attempting to decrypt malicious files (noting that the parsing of files also is a risk)) (MITIGQW11) - Qubes RPC policy to deny (MITIGQW15) - Validate GPG payload in sd-svs prior to sending to sd-gpg for decryption (MITIGQW16).

How this threat is matched

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