From: Christian Taedcke christian.taedcke@weidmueller.com

This adds a new etype encrypted.

It creates a new cipher node in the related image similar to the cipher node used by u-boot, see boot/image-cipher.c.

Signed-off-by: Christian Taedcke christian.taedcke@weidmueller.com ---

Changes in v5: - encrypted entry now inherits from Entry - remove unnecessary methods ObtainContents and ProcessContents

Changes in v3: - rebase on u-boot-dm/mkim-working - update doc for functions ObtainContents and ProcessContents - update entries.rst

Changes in v2: - add entry documentation - remove global /cipher node - replace key-name-hint with key-source property

tools/binman/entries.rst | 86 ++++++++++++++++++++ tools/binman/etype/encrypted.py | 138 ++++++++++++++++++++++++++++++++ 2 files changed, 224 insertions(+) create mode 100644 tools/binman/etype/encrypted.py

diff --git a/tools/binman/entries.rst b/tools/binman/entries.rst index b55f424620..24abc8354a 100644 --- a/tools/binman/entries.rst +++ b/tools/binman/entries.rst @@ -468,6 +468,92 @@ updating the EC on startup via software sync.

+.. _etype_encrypted: + +Entry: encrypted: Externally built encrypted binary blob +-------------------------------------------------------- + +This entry provides the functionality to include information about how to +decrypt an encrypted binary. This information is added to the +resulting device tree by adding a new cipher node in the entry's parent +node (i.e. the binary). + +The key that must be used to decrypt the binary is either directly embedded +in the device tree or indirectly by specifying a key source. The key source +can be used as an id of a key that is stored in an external device. + +Using an embedded key +~~~~~~~~~~~~~~~~~~~~~ + +This is an example using an embedded key:: + + blob-ext { + filename = "encrypted-blob.bin"; + }; + + cipher { + algo = "aes256-gcm"; + iv-filename = "encrypted-blob.bin.iv"; + key-filename = "encrypted-blob.bin.key"; + }; + +This entry generates the following device tree structure form the example +above:: + + data = [...] + cipher { + algo = "aes256-gcm"; + key = <0x...>; + iv = <0x...>; + }; + +The data property is generated by the blob-ext etype, the cipher node and +its content is generated by this etype. + +Using an external key +~~~~~~~~~~~~~~~~~~~~~ + +Instead of embedding the key itself into the device tree, it is also +possible to address an externally stored key by specifying a 'key-source' +instead of the 'key':: + + blob-ext { + filename = "encrypted-blob.bin"; + }; + + cipher { + algo = "aes256-gcm"; + iv-filename = "encrypted-blob.bin.iv"; + key-source = "external-key-id"; + }; + +This entry generates the following device tree structure form the example +above:: + + data = [...] + cipher { + algo = "aes256-gcm"; + key-source = "external-key-id"; + iv = <0x...>; + }; + +Properties +~~~~~~~~~~ + +Properties / Entry arguments: + - algo: The encryption algorithm. Currently no algorithm is supported + out-of-the-box. Certain algorithms will be added in future + patches. + - iv-filename: The name of the file containing the initialization + vector (in short iv). See + https://en.wikipedia.org/wiki/Initialization_vector + - key-filename: The name of the file containing the key. Either + key-filename or key-source must be provided. + - key-source: The key that should be used. Either key-filename or + key-source must be provided. + + + .. _etype_fdtmap:

Entry: fdtmap: An entry which contains an FDT map diff --git a/tools/binman/etype/encrypted.py b/tools/binman/etype/encrypted.py new file mode 100644 index 0000000000..9906f78601 --- /dev/null +++ b/tools/binman/etype/encrypted.py @@ -0,0 +1,138 @@ +# SPDX-License-Identifier: GPL-2.0+ +# Copyright 2023 Weidmüller Interface GmbH & Co. KG +# Written by Christian Taedcke christian.taedcke@weidmueller.com +# +# Entry-type module for cipher information of encrypted blobs/binaries +# + +from binman.etype.collection import Entry +from dtoc import fdt_util +from u_boot_pylib import tools + +# This is imported if needed +state = None + + +class Entry_encrypted(Entry): + """Externally built encrypted binary blob + + This entry provides the functionality to include information about how to + decrypt an encrypted binary. This information is added to the + resulting device tree by adding a new cipher node in the entry's parent + node (i.e. the binary). + + The key that must be used to decrypt the binary is either directly embedded + in the device tree or indirectly by specifying a key source. The key source + can be used as an id of a key that is stored in an external device. + + Using an embedded key + ~~~~~~~~~~~~~~~~~~~~~ + + This is an example using an embedded key:: + + blob-ext { + filename = "encrypted-blob.bin"; + }; + + cipher { + algo = "aes256-gcm"; + iv-filename = "encrypted-blob.bin.iv"; + key-filename = "encrypted-blob.bin.key"; + }; + + This entry generates the following device tree structure form the example + above:: + + data = [...] + cipher { + algo = "aes256-gcm"; + key = <0x...>; + iv = <0x...>; + }; + + The data property is generated by the blob-ext etype, the cipher node and + its content is generated by this etype. + + Using an external key + ~~~~~~~~~~~~~~~~~~~~~ + + Instead of embedding the key itself into the device tree, it is also + possible to address an externally stored key by specifying a 'key-source' + instead of the 'key':: + + blob-ext { + filename = "encrypted-blob.bin"; + }; + + cipher { + algo = "aes256-gcm"; + iv-filename = "encrypted-blob.bin.iv"; + key-source = "external-key-id"; + }; + + This entry generates the following device tree structure form the example + above:: + + data = [...] + cipher { + algo = "aes256-gcm"; + key-source = "external-key-id"; + iv = <0x...>; + }; + + Properties + ~~~~~~~~~~ + + Properties / Entry arguments: + - algo: The encryption algorithm. Currently no algorithm is supported + out-of-the-box. Certain algorithms will be added in future + patches. + - iv-filename: The name of the file containing the initialization + vector (in short iv). See + https://en.wikipedia.org/wiki/Initialization_vector + - key-filename: The name of the file containing the key. Either + key-filename or key-source must be provided. + - key-source: The key that should be used. Either key-filename or + key-source must be provided. + """ + + def __init__(self, section, etype, node): + # Put this here to allow entry-docs and help to work without libfdt + global state + from binman import state + + super().__init__(section, etype, node) + self.required_props = ['algo', 'iv-filename'] + self._algo = None + self._iv_filename = None + self._key_name_hint = None + self._key_filename = None + + def ReadNode(self): + super().ReadNode() + + self._algo = fdt_util.GetString(self._node, 'algo') + self._iv_filename = fdt_util.GetString(self._node, 'iv-filename') + self._key_filename = fdt_util.GetString(self._node, 'key-filename') + self._key_source = fdt_util.GetString(self._node, 'key-source') + + if self._key_filename is None and self._key_source is None: + self.Raise("Provide either 'key-filename' or 'key-source'") + + def gen_entries(self): + super().gen_entries() + + iv_filename = tools.get_input_filename(self._iv_filename) + iv = tools.read_file(iv_filename, binary=True) + + cipher_node = state.AddSubnode(self._node.parent, "cipher") + cipher_node.AddString("algo", self._algo) + cipher_node.AddData("iv", iv) + + if self._key_filename: + key_filename = tools.get_input_filename(self._key_filename) + key = tools.read_file(key_filename, binary=True) + cipher_node.AddData("key", key) + + if self._key_source: + cipher_node.AddString("key-source", self._key_source)