Set image trust requirement

  imgtrust [--allow] [--permanent]

  imgtrust

  imgtrust --allow

  imgtrust --permanent

Require the use of trusted images. When trusted images are required, any attempts to execute an untrusted image will fail. All images are untrusted by default. To become trusted, an image must be verified using the imgverify command.

If the --allow option is specified then the trusted images will no longer be required, and untrusted images may be executed.

If the --permanent option is specified, then the image trust requirement will be made permanent. Any future attempts to change the image trust requirement will fail. For example:

  iPXE> imgtrust               # Require trusted images
  iPXE> imgtrust --allow       # Allow untrusted images
  
  iPXE> imgtrust --permanent   # Permanently require trusted images
  iPXE> imgtrust --allow       # Try to allow untrusted images
  Could not set image trust requirement: Permission denied (http://ipxe.org/0200823c)

• imgverify
• iPXE cryptography guide
• List of all iPXE commands

This command is available only when the build option IMAGE_TRUST_CMD is enabled.

The default configuration is always to allow untrusted images. To require the use of trusted images, you must use an embedded script that includes the imgtrust command. For example:

  #!ipxe
  
  imgtrust --permanent
  dhcp
  imgfetch --name vmlinuz ${filename}
  imgverify vmlinuz ${filename}.sig
  imgexec vmlinuz

There is no way to use trusted images without using an embedded script.¹⁾

The imgtrust command only prevents iPXE from directly executing an untrusted image. For example: when executing a Linux kernel image, imgtrust will prevent the execution of an untrusted kernel image, but will not prevent the use of an untrusted initrd. If you want to ensure that any additional images (such as an initrd) are also trusted, then you must explicitly verify them using the imgverify command.