@@ -417,35 +417,48 @@ A network interface in use for its intended purpose is integrated into a host sy
### 4.3.2 Physical/Hardware environment
A physical network interface is attached to a host by a system bus, and the network by a transmission media adapter. Other products may also have access to the system bus or the network.
A physical network interface communicates with its host by a system bus, and the network by a transmission media adapter. A physical network interface may have access to host system assets via the system bus. Other devices may also have access to the system bus or the network and therefore access to the product via these interfaces.
A physical network interface may have access to host system assets via the system bus.
In a physical network interface, the system bus connection, transmission media adapter, or entire interface may be physically accessible to unauthorized users. Some examples of physical environments that an network interface may encounter:
The system bus and transmission media adapter of a physical network interface may be physically accessible to untrusted users.
* a factory for an integrator
* the interior of a physically secured appliance
* plugged into the USB port of a laptop in a home
* in a library computer with the physical tranmission adapter physically accessible to the user
A physical network interface will vary in ease of removal from the host system.
A virtual network interface communicates with the host system and the network via software interfaces to the host software, all of which runs on a hardware platform.
### 4.3.3 Logical/Software environment
The host system make use of the physical or virtual network interface via host software, most often an operating system that implements a network stack.
The host system makes use of the physical or virtual network interface via host software that communicates with the network interface, most often an operating system that implements a device driver interface and a network stack.
The host software is responsible for controlling access to the network interface from the host system. For the purposes of protecting the cybersecurity of the user of the network interface, the network interface fully trusts the host system to protect the assets exposed to the host system.
However, the network interface may, for regulatory or business reasons, implement features that do not rely on trusting the host system. For example, a radio frequency transmission media adapter may not accept the installation of firmware not cryptographically signed by the manufacturer to fulfill regulatory requirements (such as the power of a software-controlled radio) or satisfy intellectual property concerns (such as revealing the content of the firmware binary).
The host system typically uses the functions of a physical network interface through a device driver. If the device driver is not included with the product, it will be provided by the operating system or other part of the system.
The host system typically uses the functions of a physical network interface through a device driver. This device driver may be included with the product or provided independently of the product.
A virtual network interface does not require a separate device driver.
A virtual network interface is a device driver running in the context of the host software. A virtual network interface does not require a separate device driver.
Untrusted agents may be able to run unprivileged software on the host system.
Users may be able to gain unauthorized access to the host system via compromise of the host system, and therefore may bypass the host system's authorization and access control system.
The hardware and software on the product and any associated device driver will range in complexity depending on the number and type of features implemented.
The sensitivity of the data stored on and transmitted by the host system will vary, as will the functions of the host system.
Users not authorized by the host system to directly access the network interface may have the ability to indirectly exercise the functions of the product, such as by sending data using a host system interface that send the data over the network interface.
### 4.3.4 Connectivity aspects
A network interface is attached to a network which may be accessible by other products attached to the network.
A network interface is connected to a network which may be accessible by other devices connected to the network.
A physical network interface is connected to a host system bus which may be accessible to other devices connected to the system bus.
A physical network interface is attached to a host system bus which may be accessible by other products attached to the system bus.
A virtual network interface is connected to a host system by a software interface and by shared memory or other system resources which may be accessible by other software on the system.
The attached network may be an isolated private network, a private network with a filtered connection to a public network, or a public network directly accessible by many untrusted agents.
The network the device is connected to may be an isolated private network with no connection to a public network, a private network with a filtered connection to a public network, or a public network directly accessible by many untrusted agents.
## 4.4 Distribution of Security Functions
@@ -455,33 +468,35 @@ The attached network may be an isolated private network, a private network with
For each cybersecurity requirement, a product may:
1. Provide all necessary security functions itself
2. Require security functions be provided by some other part of its context
3. Provide security functions for the use of other components
1. Provide some or all of the necessary security functions itself
2. Require some or all of the security functions be provided by the operational environment
3. Provide security functions used by other components for their cybersecurity requirement
For example, most individual hardware components do not have a built-in method of securely updating any firmware in the product. Usually this requires a full-featured system running an operating system which can check for firmware updates, download and verify them, and carry out the process of updating the firmware.
For example, many network interfaces do not have a built-in method of securely updating the software or firmware in the product. Instead, they rely on host system to check for security updates, download and verify them, and write the updated software image. The host system does this by using interfaces provided by the network interface to query the version of the installed software and write the software image.
### 4.4.2 Security functions provided outside the product
The following security functionalities are frequently handled by the operating system or other external component:
The following security functionalities are often provided partly or entirely by the operational environment, such as the host operating system or the physical protection of the product:
* Secure by default configuration
* Secure configuration changes
* Secure update of firmware and/or device driver
* Authentication of users
* Authorization of users
* Authentication and access control
* Confidentiality and integrity protection of data stored and transmitted
* Availability protection other than at the physical or link layer of the network
* Exploit mitigation
* Deletion and transfer of user data
* Provision of cryptographic keys to network interface
A component that provides a security function critical to the cybersecurity of the product is assumed to be trustworthy for the purposes of the present document.
### 4.4.3 Security functions provided to other components
The network interface provides the following security functions to other parts of the system:
*Reporting of network-related statistics
*Monitoring, such as reporting of network-related statistics or interface state changes
Optional features the product may implement, with hardware offloading or features built into the driver.
Availability and implementation style is often tied to the protocol.
These features can be, but are not limited to:
The product may implement additional optional security functions, such as with hardware offloading of encryption. These features are often implemented as part of the network protocol the network interface implements. These functions can be, but are not limited to:
* Integrity protection via data link layer error detection and correction
* Confidential communication channel when providing encryption at the data link layer (WPA2, MACSEC)
