efibootmgr

package
v0.6.0 Latest Latest
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 Go to latest Published: Jun 25, 2026 License: GPL-3.0 Imports: 29 Imported by: 1

Documentation

Overview

Package efibootmgr contains a boot management library

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

func DelVariable added in v0.1.0 

func DelVariable(efivars EFIVariables, guid efi.GUID, name string) error

DelVariable deletes the non-authenticated variable with the specified name.

func GetEfiArchitecture 

func GetEfiArchitecture() string

GetEfiArchitecture returns the EFI architecture for the target system

func GetVariableNames added in v0.1.0 

func GetVariableNames(efiVars EFIVariables, filterGUID efi.GUID) (names []string, err error)

GetVariableNames returns the names of every variable with the specified GUID.

func InstallShim 

func InstallShim(esp string, source string, vendor string) (bool, error)

InstallShim installs the shim into the given ESP for the given vendor It returns true if it installed the shim.

func MaybeUpdateFile 

func MaybeUpdateFile(dst string, src string) (updated bool, err error)

MaybeUpdateFile copies src to dest if they are different It returns true if the destination file was successfully updated. If the return value is false, the state of the destination is unspecified. It might not exist, exist with partial data or exist with old data, amongst others.

func ResealKey added in v0.1.0 

func ResealKey(assets *TrustedAssets, km *KernelManager, esp, shimSource, vendor string) error

ResealKey updates the PCR profile for the disk encryption key to incorporate the boot assets installed directly by the package manager and those assets copied by this package to the ESP.

func TrustCurrentBoot added in v0.1.1 

func TrustCurrentBoot(assets *TrustedAssets, esp string) error

TrustCurrentBoot adds the assets used in the current boot to the list of boot assets trusted for adding to PCR profiles with ResealKey. It works by mapping EV_EFI_BOOT_SERVICES_APPLICATION events from the TCG log to files stored in the ESP.

func VariablesSupported added in v0.1.0 

func VariablesSupported(efiVars EFIVariables) bool

VariablesSupported indicates whether variables can be accessed.

func WriteShimFallback 

func WriteShimFallback(w io.Writer, entries []BootEntry) error

WriteShimFallback writes out a BOOT*.CSV for the shim fallback loader to the specified writer. The output of this function is unencoded, use a transformed UTF-16 writer.

func WriteShimFallbackToFile 

func WriteShimFallbackToFile(path string, entries []BootEntry) error

WriteShimFallbackToFile opens the specified path in UTF-16LE and then calls WriteShimFallback

Types

type BootEntry 

type BootEntry struct {
	Filename    string
	Label       string
	Options     string
	Description string
}

BootEntry is a boot entry.

func NewKernelBootEntry added in v0.6.0 

func NewKernelBootEntry(vendor string, kernel Kernel, kernelOptions string) BootEntry

type BootEntryVariable 

type BootEntryVariable struct {
	BootNumber int                    // number of the Boot variable, for example, for Boot0004 this is 4
	Data       []byte                 // the data of the variable
	Attributes efi.VariableAttributes // any attributes set on the variable
	LoadOption *efi.LoadOption        // the data of the variable parsed as a load option, if it is a valid load option
}

BootEntryVariable defines a boot entry variable

func NewBootEntryVariable added in v0.6.0 

func NewBootEntryVariable(entry BootEntry, bootNum int, dp efi.DevicePath) (BootEntryVariable, error)

NewBootEntryVariable creates a BootEntryVariable derived from a BootEntry, given a boot number and device path.

type BootManager 

type BootManager struct {
	// contains filtered or unexported fields
}

BootManager manages the boot device selection menu entries (Boot0000...BootFFFF).

func NewBootManagerForVariables added in v0.4.0 

func NewBootManagerForVariables(efivars EFIVariables) (BootManager, error)

NewBootManagerForVariables returns a boot manager for the given EFIVariables manager

func NewBootManagerFromSystem 

func NewBootManagerFromSystem() (BootManager, error)

NewBootManagerFromSystem returns a new BootManager object, initialized with the system state.

func (*BootManager) DeleteEntry 

func (bm *BootManager) DeleteEntry(bootNum int) error

DeleteEntry deletes an entry and updates the cached boot order.

The boot order still needs to be committed afterwards. It is not written back immediately, as there will usually be multiple places to update boot order, and we can coalesce those writes. We still have to update the boot order though, such that when we delete an entry and then create a new one with the same number we don't accidentally have the new one in the order.

func (*BootManager) FindBootEntryVariable added in v0.6.0 

func (bm *BootManager) FindBootEntryVariable(entry BootEntry, relativeTo string) (BootEntryVariable, error)

FindBootEntryVariable finds a matching BootEntryVariable from the boot device selection menu associated to the input BootEntry in a relative directory.

The argument relativeTo specifies the directory entry.Filename is in.

If a BootEntryVariable cannot be found, returns BootVarNotFoundError.

func (*BootManager) FindOrCreateEntry 

func (bm *BootManager) FindOrCreateEntry(entry BootEntry, relativeTo string) (int, error)

FindOrCreateEntry finds a matching entry in the boot device selection menu, or creates one if it is missing.

It returns the number of the entry created, or invalidBootNumber on failure, with error set.

The argument relativeTo specifies the directory entry.Filename is in.

func (*BootManager) NextFreeEntry 

func (bm *BootManager) NextFreeEntry() (int, error)

NextFreeEntry returns the number of the next free Boot variable.

func (*BootManager) PrependAndSetBootOrder 

func (bm *BootManager) PrependAndSetBootOrder(head []int) error

PrependAndSetBootOrder commits a new boot order or returns an error.

The boot order specified is prepended to the existing one, and the order is deduplicated before committing.

func (*BootManager) RegisterBootEntryVariable added in v0.6.0 

func (bm *BootManager) RegisterBootEntryVariable(entryVar BootEntryVariable) error

RegisterBootEntryVariable registers a system boot variable to the bm.efivars and bm.entries.

It returns an error should there be an issue registering the system variable.

func (*BootManager) SetBootNext added in v0.6.0 

func (bm *BootManager) SetBootNext(bootNum int) error

SetBootNext sets the system BootNext variable to the encoded value of the input boot number.

Returns an error in the event that the variable cannot be set.

type BootVarNotFoundError added in v0.6.0 

type BootVarNotFoundError struct {
	Message string
	Err     error
}

func (BootVarNotFoundError) Error added in v0.6.0 

func (e BootVarNotFoundError) Error() string

func (BootVarNotFoundError) Unwrap added in v0.6.0 

func (e BootVarNotFoundError) Unwrap() error

type EFIVariables 

type EFIVariables interface {
	ListVariables() ([]efi.VariableDescriptor, error)
	GetVariable(guid efi.GUID, name string) (data []byte, attrs efi.VariableAttributes, err error)
	SetVariable(guid efi.GUID, name string, data []byte, attrs efi.VariableAttributes) error
	NewFileDevicePath(filepath string, mode efi_linux.FilePathToDevicePathMode) (efi.DevicePath, error)
}

EFIVariables abstracts away the host-specific bits of the efivars module

type FS 

type FS interface {
	// Create behaves like os.Create()
	Create(path string) (File, error)
	// MkdirAll behaves like os.MkdirAll()
	MkdirAll(path string, perm os.FileMode) error
	// Open behaves like os.Open()
	Open(path string) (File, error)
	// ReadDir behaves like os.ReadDir()
	ReadDir(path string) ([]os.DirEntry, error)
	// Readlink behaves like os.Readlink()
	Readlink(path string) (string, error)
	// Remove behaves like os.Remove()
	Remove(path string) error
	// Rename behaves like os.Rename()
	Rename(oldname, newname string) error
	// Stat behaves like os.Stat()
	Stat(path string) (os.FileInfo, error)
	// TempFile behaves like ioutil.TempFile()
	TempFile(dir, prefix string) (File, error)
}

FS abstracts away the filesystem.

So we really wanted to use afero because it does all the magic for us, but it doubles our binary size, so that seems a tad much.

type File added in v0.1.0 

type File interface {
	io.Closer
	io.Writer
	io.Reader
	io.ReaderAt
	io.Seeker

	Name() string
	Stat() (os.FileInfo, error)
}

File abstracts an open file.

type Kernel added in v0.6.0 

type Kernel struct {
	Version  version.Version
	FilePath string
}

func NewKernel added in v0.6.0 

func NewKernel(kernelPath string) (Kernel, error)

func (*Kernel) Equals added in v0.6.0 

func (k *Kernel) Equals(other Kernel) bool

func (*Kernel) GetKernelName added in v0.6.0 

func (k *Kernel) GetKernelName() string

type KernelEntry added in v0.6.0 

type KernelEntry struct {
	// contains filtered or unexported fields
}

type KernelManager 

type KernelManager struct {
	// contains filtered or unexported fields
}

KernelManager manages kernels in an SP vendor directory.

It will update or install shim, copy in any new kernels, remove old kernels, and configure boot in shim and BDS.

func NewKernelManager 

func NewKernelManager(esp, sourceDir, vendor string, bootManager *BootManager) (*KernelManager, error)

NewKernelManager returns a new kernel manager managing kernels in the host system

func (*KernelManager) CommitToBootLoader 

func (km *KernelManager) CommitToBootLoader() error

CommitToBootLoader updates the firmware BDS entries and shim's boot.csv

func (*KernelManager) GetLatestKernelEntry added in v0.6.0 

func (km *KernelManager) GetLatestKernelEntry() (KernelEntry, error)

Returns the KernelEntry with the largest version in km.kernelEntries

func (*KernelManager) InstallKernels 

func (km *KernelManager) InstallKernels() error

InstallKernels installs the kernels to the ESP and builds up the boot entries to commit using CommitToBootLoader()

func (*KernelManager) IsCurrentBootLatest added in v0.6.0 

func (km *KernelManager) IsCurrentBootLatest() (bool, error)

func (*KernelManager) RegisterNewKernelEFIs added in v0.6.0 

func (km *KernelManager) RegisterNewKernelEFIs() error

RegisterNewKernelEFIs creates EFI variables for each new kernel installed via InstallKernels, adding them to the BootManager and creating the variables on the host machine.

func (*KernelManager) RemoveObsoleteKernels 

func (km *KernelManager) RemoveObsoleteKernels() error

RemoveObsoleteKernels removes old kernels in the ESP vendor directory

func (*KernelManager) SetLatestKernelToBootNext added in v0.6.0 

func (km *KernelManager) SetLatestKernelToBootNext() error

SetLatestKernelToBootNext sets the latest kernel to be BootNext.

Returns an error if the entry does not yet exist as a BootEntryVariable or if there is an error setting BootNext.

type LoadChain added in v0.6.0 

type LoadChain struct {

	// Next is a list of alternative chains that can be loaded
	// following the boot file.
	Next []*LoadChain
	// contains filtered or unexported fields
}

func NewLoadChain added in v0.6.0 

func NewLoadChain(image *trustedEFIImage, next ...*LoadChain) *LoadChain

func (LoadChain) Open added in v0.6.0 

func (i LoadChain) Open() (imageReader secboot_efi.ImageReader, err error)

func (LoadChain) String added in v0.6.0 

func (i LoadChain) String() string

type MockEFIVariables added in v0.4.0 

type MockEFIVariables struct {
	// contains filtered or unexported fields
}

MockEFIVariables implements an in-memory variable store.

func (MockEFIVariables) GetVariable added in v0.4.0 

func (m MockEFIVariables) GetVariable(guid efi.GUID, name string) (data []byte, attrs efi.VariableAttributes, err error)

GetVariable implements EFIVariables

func (MockEFIVariables) JSON added in v0.4.0 

func (m MockEFIVariables) JSON() ([]byte, error)

JSON renders the MockEFIVariables as an Azure JSON config

func (MockEFIVariables) ListVariables added in v0.4.0 

func (m MockEFIVariables) ListVariables() (out []efi.VariableDescriptor, err error)

ListVariables implements EFIVariables

func (MockEFIVariables) NewFileDevicePath added in v0.4.0 

func (m MockEFIVariables) NewFileDevicePath(filepath string, mode efi_linux.FilePathToDevicePathMode) (efi.DevicePath, error)

NewFileDevicePath implements EFIVariables

func (*MockEFIVariables) SetVariable added in v0.4.0 

func (m *MockEFIVariables) SetVariable(guid efi.GUID, name string, data []byte, attrs efi.VariableAttributes) error

SetVariable implements EFIVariables

type RealEFIVariables 

type RealEFIVariables struct{}

RealEFIVariables provides the real implementation of efivars

func (RealEFIVariables) GetVariable 

func (vars RealEFIVariables) GetVariable(guid efi.GUID, name string) (data []byte, attrs efi.VariableAttributes, err error)

GetVariable proxy

func (RealEFIVariables) ListVariables added in v0.1.0 

func (vars RealEFIVariables) ListVariables() ([]efi.VariableDescriptor, error)

ListVariables proxy

func (RealEFIVariables) NewFileDevicePath added in v0.1.0 

func (vars RealEFIVariables) NewFileDevicePath(filepath string, mode efi_linux.FilePathToDevicePathMode) (efi.DevicePath, error)

NewFileDevicePath proxy

func (RealEFIVariables) SetVariable 

func (vars RealEFIVariables) SetVariable(guid efi.GUID, name string, data []byte, attrs efi.VariableAttributes) error

SetVariable proxy

type TrustedAssets added in v0.1.0 

type TrustedAssets struct {
	// contains filtered or unexported fields
}

TrustedAssets keeps a record of boot asset hashes that are trusted for the purpose of computing PCR profiles. New hashes are added by adding a directory that is trusted using TrustNewFromDir - the directory will be one inside the encrypted container, writable by root and managed by the package manager).

Boot assets may be copied outside of a trusted directory, eg, to the ESP. Assets loaded from outside of a trusted directory in order to compute a PCR profile must be checked against one of the trusted hashes, to avoid tricking the resealing code into adding a malicious asset to a PCR profile.

Snapd achieves the same thing by keeping a cache of trusted assets inside the encrypted data partition. This avoids having to do that.

Note that the hashes are not constructed by hashing the file contents in a single pass, as this would require keeping entire PE images in memory after verifying their hashes in order to avoid TOCTOU type bugs. Files are hashed by producing a hash tree with a 4k block size. If a file's size is not a multiple of 4k, the last block is padded with zeros.

The hash tree is not stored anywhere - only the root hash is stored. In order to verify that a file's contents are trusted, the leaf hashes are constructed when the file is read and then closed (see hashedFile) and the rest of the hash tree is reconstructed by calling checkLeafHashes. In order to verify any blocks, the entire file has to eventually be read in order to reconstruct the entire hash tree. This is a tradeoff between having to read an entire file in order to verify a few blocks, and not having to read an entire file in order to verify a few blocks, but having to store the entire hash tree somewhere.

Use newCheckedHashedFile to have a file checked against the set of trusted boot assets.

func ReadTrustedAssets added in v0.1.0 

func ReadTrustedAssets() (*TrustedAssets, error)

ReadTrustedAssets loads the list of previously trusted hashes from disk.

func (*TrustedAssets) RemoveObsolete added in v0.1.0 

func (t *TrustedAssets) RemoveObsolete()

RemoveObsolete drops all asset hashes that haven't been added in this context via a call to TrustNewFromDir. This should be called after newly trusted assets have been properly committed and obsolete assets have been removed.

func (*TrustedAssets) Save added in v0.1.0 

func (t *TrustedAssets) Save() (err error)

Save persists the list of trusted hashes to disk.

func (*TrustedAssets) TrustNewFromDir added in v0.1.0 

func (t *TrustedAssets) TrustNewFromDir(path string) error

TrustNewFromDir adds hashes of the files under the specified path to the list of trusted hashes for the purpose of computing PCR profiles. The path should be within the encrypted container, writable only by root and managed by the package manager.

Source Files

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