3 title: Communication modes
5 https://raw.githubusercontent.com/automotive-grade-linux/docs-sources/master/docs/security-blueprint/part-2/2-Communication-modes.md
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12 ## Disable USB, Serial and DOCSIS Support
14 To disable USB support in U-Boot, following config's shall not be defined:
17 CONFIG_CMD_USB: Enables basic USB support and the usb command.
18 CONFIG_USB_UHCI: Defines the lowlevel part.
19 CONFIG_USB_KEYBOARD: Enables the USB Keyboard.
20 CONFIG_USB_STORAGE: Enables the USB storage devices.
21 CONFIG_USB_HOST_ETHER: Enables USB Ethernet adapter support.
24 In addition, disable unnecessary communication modes like Ethernet, Serial
25 ports, DOCSIS in U-Boot and sboot that are not necessary.
27 Linux Kernel support for USB should be compiled-out if not required. If it is
28 needed, the Linux Kernel should be configured to only enable the minimum
29 required USB devices. User-initiated USB-filesystems should be treated with
30 special care. Whether or not the filesystems are mounted in userspace
31 (**FUSE**), restricted mount options should be observed.
33 <!-- section-config -->
35 Domain | Communication modes | _State_
36 -------------------- | ------------------------- | --------------------------------------------------------------------------------------------------------------------------------------
37 Boot-Communication-1 | `USB` | _Disabled_ and _Compiled-out_ if not required.
38 Boot-Communication-2 | `USB` | Else, Kernel should be configured to only enable the minimum required USB devices and filesystems should be treated with special care.
39 Boot-Communication-3 | `Ethernet` | _Disabled_
40 Boot-Communication-4 | U-boot and sboot `DOCSIS` | _Disabled_
41 Boot-Communication-5 | `Serial ports` | _Disabled_
43 <!-- end-section-config --> <!-- section-config -->
45 Domain | `Config` name | _State_
46 ------------------------ | ----------------------- | -------------
47 Boot-Communication-USB-1 | `CONFIG_CMD_USB` | _Not defined_
48 Boot-Communication-USB-2 | `CONFIG_USB_UHCI` | _Not defined_
49 Boot-Communication-USB-3 | `CONFIG_USB_KEYBOARD` | _Not defined_
50 Boot-Communication-USB-4 | `CONFIG_USB_STORAGE` | _Not defined_
51 Boot-Communication-USB-5 | `CONFIG_USB_HOST_ETHER` | _Not defined_
53 <!-- end-section-config -->
55 --------------------------------------------------------------------------------
57 ## Disable all unused Network Interfaces
59 Only used network interfaces should be enabled.
60 Where possible, services should also be limited to those necessary.
62 <!-- section-config -->
64 Domain | Communication modes | _State_
65 -------------------- | -------------------- | ---------------------------------------------------------------------------------------------
66 Boot-Communication-1 | `Network interfaces` | Preferably _no network interface is allowed_, otherwise, restrict the services to those used.
68 <!-- end-section-config -->
70 ## Remove or Disable Unnecessary Services, Ports, and Devices
72 Restrict the `services`, `ports` and `devices` to those used.
74 <!-- section-config -->
76 Domain | Object | Recommendations
77 -------------------- | --------------------------------- | -------------------------------------------------------------
78 Boot-Communication-1 | `Services`, `ports` and `devices` | Restrict the `services`, `ports` and `devices` to those used.
80 <!-- end-section-config -->
82 ## Disable flash access
86 In U-Boot following flash memory commands shall be disabled:
88 **NAND**: Support for nand flash access available through `do_nand` has to be disabled.
90 <!-- section-config -->
92 Domain | `Command` name | _State_
93 -------------------------- | -------------- | ---------
94 Boot-Communication-Flash-1 | `do_nand` | _Disable_
96 <!-- end-section-config -->
98 Similarly sboot should disable flash access support through command line if any.