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@@ -0,0 +1,380 @@
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+#!/usr/bin/env python3
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+## SPDX-License-Identifier: GPL-2.0-only
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+#
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+# EFI variable store utilities.
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+#
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+# (c) 2020 Paulo Alcantara <palcantara@suse.de>
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+#
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+
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+import os
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+import struct
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+import uuid
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+import time
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+import zlib
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+import argparse
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+from OpenSSL import crypto
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+
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+# U-Boot variable store format (version 1)
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+UBOOT_EFI_VAR_FILE_MAGIC = 0x0161566966456255
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+
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+# UEFI variable attributes
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+EFI_VARIABLE_NON_VOLATILE = 0x1
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+EFI_VARIABLE_BOOTSERVICE_ACCESS = 0x2
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+EFI_VARIABLE_RUNTIME_ACCESS = 0x4
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+EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS = 0x10
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+EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS = 0x20
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+EFI_VARIABLE_READ_ONLY = 1 << 31
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+NV_BS = EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS
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+NV_BS_RT = NV_BS | EFI_VARIABLE_RUNTIME_ACCESS
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+NV_BS_RT_AT = NV_BS_RT | EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS
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+DEFAULT_VAR_ATTRS = NV_BS_RT
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+
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+# vendor GUIDs
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+EFI_GLOBAL_VARIABLE_GUID = '8be4df61-93ca-11d2-aa0d-00e098032b8c'
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+EFI_IMAGE_SECURITY_DATABASE_GUID = 'd719b2cb-3d3a-4596-a3bc-dad00e67656f'
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+EFI_CERT_TYPE_PKCS7_GUID = '4aafd29d-68df-49ee-8aa9-347d375665a7'
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+WIN_CERT_TYPE_EFI_GUID = 0x0ef1
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+WIN_CERT_REVISION = 0x0200
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+
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+var_attrs = {
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+ 'NV': EFI_VARIABLE_NON_VOLATILE,
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+ 'BS': EFI_VARIABLE_BOOTSERVICE_ACCESS,
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+ 'RT': EFI_VARIABLE_RUNTIME_ACCESS,
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+ 'AT': EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS,
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+ 'RO': EFI_VARIABLE_READ_ONLY,
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+ 'AW': EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS,
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+}
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+
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+var_guids = {
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+ 'EFI_GLOBAL_VARIABLE_GUID': EFI_GLOBAL_VARIABLE_GUID,
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+ 'EFI_IMAGE_SECURITY_DATABASE_GUID': EFI_IMAGE_SECURITY_DATABASE_GUID,
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+}
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+
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+class EfiStruct:
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+ # struct efi_var_file
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+ var_file_fmt = '<QQLL'
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+ var_file_size = struct.calcsize(var_file_fmt)
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+ # struct efi_var_entry
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+ var_entry_fmt = '<LLQ16s'
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+ var_entry_size = struct.calcsize(var_entry_fmt)
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+ # struct efi_time
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+ var_time_fmt = '<H6BLh2B'
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+ var_time_size = struct.calcsize(var_time_fmt)
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+ # WIN_CERTIFICATE
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+ var_win_cert_fmt = '<L2H'
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+ var_win_cert_size = struct.calcsize(var_win_cert_fmt)
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+ # WIN_CERTIFICATE_UEFI_GUID
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+ var_win_cert_uefi_guid_fmt = var_win_cert_fmt+'16s'
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+ var_win_cert_uefi_guid_size = struct.calcsize(var_win_cert_uefi_guid_fmt)
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+
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+class EfiVariable:
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+ def __init__(self, size, attrs, time, guid, name, data):
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+ self.size = size
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+ self.attrs = attrs
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+ self.time = time
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+ self.guid = guid
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+ self.name = name
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+ self.data = data
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+
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+def calc_crc32(buf):
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+ return zlib.crc32(buf) & 0xffffffff
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+
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+class EfiVariableStore:
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+ def __init__(self, infile):
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+ self.infile = infile
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+ self.efi = EfiStruct()
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+ if os.path.exists(self.infile) and os.stat(self.infile).st_size > self.efi.var_file_size:
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+ with open(self.infile, 'rb') as f:
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+ buf = f.read()
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+ self._check_header(buf)
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+ self.ents = buf[self.efi.var_file_size:]
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+ else:
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+ self.ents = bytearray()
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+
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+ def _check_header(self, buf):
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+ hdr = struct.unpack_from(self.efi.var_file_fmt, buf, 0)
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+ magic, crc32 = hdr[1], hdr[3]
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+
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+ if magic != UBOOT_EFI_VAR_FILE_MAGIC:
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+ print("err: invalid magic number: %s"%hex(magic))
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+ exit(1)
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+ if crc32 != calc_crc32(buf[self.efi.var_file_size:]):
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+ print("err: invalid crc32: %s"%hex(crc32))
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+ exit(1)
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+
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+ def _get_var_name(self, buf):
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+ name = ''
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+ for i in range(0, len(buf) - 1, 2):
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+ if not buf[i] and not buf[i+1]:
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+ break
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+ name += chr(buf[i])
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+ return ''.join([chr(x) for x in name.encode('utf_16_le') if x]), i + 2
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+
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+ def _next_var(self, offs=0):
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+ size, attrs, time, guid = struct.unpack_from(self.efi.var_entry_fmt, self.ents, offs)
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+ data_fmt = str(size)+"s"
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+ offs += self.efi.var_entry_size
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+ name, namelen = self._get_var_name(self.ents[offs:])
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+ offs += namelen
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+ data = struct.unpack_from(data_fmt, self.ents, offs)[0]
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+ # offset to next 8-byte aligned variable entry
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+ offs = (offs + len(data) + 7) & ~7
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+ return EfiVariable(size, attrs, time, uuid.UUID(bytes_le=guid), name, data), offs
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+
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+ def __iter__(self):
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+ self.offs = 0
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+ return self
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+
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+ def __next__(self):
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+ if self.offs < len(self.ents):
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+ var, noffs = self._next_var(self.offs)
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+ self.offs = noffs
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+ return var
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+ else:
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+ raise StopIteration
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+
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+ def __len__(self):
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+ return len(self.ents)
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+
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+ def _set_var(self, guid, name_data, size, attrs, tsec):
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+ ent = struct.pack(self.efi.var_entry_fmt,
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+ size,
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+ attrs,
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+ tsec,
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+ uuid.UUID(guid).bytes_le)
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+ ent += name_data
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+ self.ents += ent
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+
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+ def del_var(self, guid, name, attrs):
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+ offs = 0
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+ while offs < len(self.ents):
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+ var, loffs = self._next_var(offs)
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+ if var.name == name and str(var.guid):
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+ if var.attrs != attrs:
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+ print("err: attributes don't match")
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+ exit(1)
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+ self.ents = self.ents[:offs] + self.ents[loffs:]
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+ return
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+ offs = loffs
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+ print("err: variable not found")
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+ exit(1)
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+
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+ def set_var(self, guid, name, data, size, attrs):
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+ offs = 0
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+ while offs < len(self.ents):
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+ var, loffs = self._next_var(offs)
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+ if var.name == name and str(var.guid) == guid:
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+ if var.attrs != attrs:
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+ print("err: attributes don't match")
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+ exit(1)
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+ # make room for updating var
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+ self.ents = self.ents[:offs] + self.ents[loffs:]
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+ break
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+ offs = loffs
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+
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+ tsec = int(time.time()) if attrs & EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS else 0
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+ nd = name.encode('utf_16_le') + b"\x00\x00" + data
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+ # U-Boot variable format requires the name + data blob to be 8-byte aligned
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+ pad = ((len(nd) + 7) & ~7) - len(nd)
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+ nd += bytes([0] * pad)
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+
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+ return self._set_var(guid, nd, size, attrs, tsec)
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+
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+ def save(self):
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+ hdr = struct.pack(self.efi.var_file_fmt,
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+ 0,
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+ UBOOT_EFI_VAR_FILE_MAGIC,
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+ len(self.ents) + self.efi.var_file_size,
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+ calc_crc32(self.ents))
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+
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+ with open(self.infile, 'wb') as f:
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+ f.write(hdr)
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+ f.write(self.ents)
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+
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+def parse_attrs(attrs):
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+ v = DEFAULT_VAR_ATTRS
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+ if attrs:
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+ v = 0
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+ for i in attrs.split(','):
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+ v |= var_attrs[i.upper()]
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+ return v
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+
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+def parse_data(val, vtype):
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+ if not val or not vtype:
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+ return None, 0
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+ fmt = { 'u8': '<B', 'u16': '<H', 'u32': '<L', 'u64': '<Q' }
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+ if vtype.lower() == 'file':
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+ with open(val, 'rb') as f:
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+ data = f.read()
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+ return data, len(data)
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+ if vtype.lower() == 'str':
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+ data = val.encode('utf-8')
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+ return data, len(data)
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+ if vtype.lower() == 'nil':
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+ return None, 0
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+ i = fmt[vtype.lower()]
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+ return struct.pack(i, int(val)), struct.calcsize(i)
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+
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+def parse_args(args):
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+ name = args.name
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+ attrs = parse_attrs(args.attrs)
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+ guid = args.guid if args.guid else EFI_GLOBAL_VARIABLE_GUID
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+
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+ if name.lower() == 'db' or name.lower() == 'dbx':
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+ name = name.lower()
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+ guid = EFI_IMAGE_SECURITY_DATABASE_GUID
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+ attrs = NV_BS_RT_AT
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+ elif name.lower() == 'pk' or name.lower() == 'kek':
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+ name = name.upper()
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+ guid = EFI_GLOBAL_VARIABLE_GUID
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+ attrs = NV_BS_RT_AT
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+
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+ data, size = parse_data(args.data, args.type)
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+ return guid, name, attrs, data, size
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+
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+def cmd_set(args):
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+ env = EfiVariableStore(args.infile)
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+ guid, name, attrs, data, size = parse_args(args)
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+ env.set_var(guid=guid, name=name, data=data, size=size, attrs=attrs)
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+ env.save()
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+
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+def print_var(var):
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+ print(var.name+':')
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+ print(" "+str(var.guid)+' '+''.join([x for x in var_guids if str(var.guid) == var_guids[x]]))
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+ print(" "+'|'.join([x for x in var_attrs if var.attrs & var_attrs[x]])+", DataSize = %s"%hex(var.size))
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+ hexdump(var.data)
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+
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+def cmd_print(args):
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+ env = EfiVariableStore(args.infile)
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+ if not args.name and not args.guid and not len(env):
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+ return
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+
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+ found = False
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+ for var in env:
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+ if not args.name:
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+ if args.guid and args.guid != str(var.guid):
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+ continue
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+ print_var(var)
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+ found = True
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+ else:
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+ if args.name != var.name or (args.guid and args.guid != str(var.guid)):
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+ continue
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+ print_var(var)
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+ found = True
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+
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+ if not found:
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+ print("err: variable not found")
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+ exit(1)
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+
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+def cmd_del(args):
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+ env = EfiVariableStore(args.infile)
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+ attrs = parse_attrs(args.attrs)
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+ guid = args.guid if args.guid else EFI_GLOBAL_VARIABLE_GUID
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+ env.del_var(guid, args.name, attrs)
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+ env.save()
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+
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+def pkcs7_sign(cert, key, buf):
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+ with open(cert, 'r') as f:
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+ crt = crypto.load_certificate(crypto.FILETYPE_PEM, f.read())
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+ with open(key, 'r') as f:
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+ pkey = crypto.load_privatekey(crypto.FILETYPE_PEM, f.read())
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+
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+ PKCS7_BINARY = 0x80
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+ PKCS7_DETACHED = 0x40
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+ PKCS7_NOATTR = 0x100
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+
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+ bio_in = crypto._new_mem_buf(buf)
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+ p7 = crypto._lib.PKCS7_sign(crt._x509, pkey._pkey, crypto._ffi.NULL, bio_in,
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+ PKCS7_BINARY|PKCS7_DETACHED|PKCS7_NOATTR)
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+ bio_out = crypto._new_mem_buf()
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+ crypto._lib.i2d_PKCS7_bio(bio_out, p7)
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+ return crypto._bio_to_string(bio_out)
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+
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+# UEFI 2.8 Errata B "8.2.2 Using the EFI_VARIABLE_AUTHENTICATION_2 descriptor"
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+def cmd_sign(args):
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+ guid, name, attrs, data, size = parse_args(args)
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+ attrs |= EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS
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+ efi = EfiStruct()
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+
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+ tm = time.localtime()
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+ etime = struct.pack(efi.var_time_fmt,
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+ tm.tm_year, tm.tm_mon, tm.tm_mday,
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+ tm.tm_hour, tm.tm_min, tm.tm_sec,
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+ 0, 0, 0, 0, 0)
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+
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+ buf = name.encode('utf_16_le') + uuid.UUID(guid).bytes_le + attrs.to_bytes(4, byteorder='little') + etime
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+ if data:
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+ buf += data
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+ sig = pkcs7_sign(args.cert, args.key, buf)
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+
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+ desc = struct.pack(efi.var_win_cert_uefi_guid_fmt,
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+ efi.var_win_cert_uefi_guid_size + len(sig),
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+ WIN_CERT_REVISION,
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+ WIN_CERT_TYPE_EFI_GUID,
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+ uuid.UUID(EFI_CERT_TYPE_PKCS7_GUID).bytes_le)
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+
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+ with open(args.outfile, 'wb') as f:
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+ if data:
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+ f.write(etime + desc + sig + data)
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+ else:
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+ f.write(etime + desc + sig)
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+
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+def main():
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+ ap = argparse.ArgumentParser(description='EFI variable store utilities')
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+ subp = ap.add_subparsers(help="sub-command help")
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+
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+ printp = subp.add_parser('print', help='get/list EFI variables')
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+ printp.add_argument('--infile', '-i', required=True, help='file to save the EFI variables')
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+ printp.add_argument('--name', '-n', help='variable name')
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+ printp.add_argument('--guid', '-g', help='vendor GUID')
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+ printp.set_defaults(func=cmd_print)
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+
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+ setp = subp.add_parser('set', help='set EFI variable')
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+ setp.add_argument('--infile', '-i', required=True, help='file to save the EFI variables')
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+ setp.add_argument('--name', '-n', required=True, help='variable name')
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+ setp.add_argument('--attrs', '-a', help='variable attributes (values: nv,bs,rt,at,ro,aw)')
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+ setp.add_argument('--guid', '-g', help="vendor GUID (default: %s)"%EFI_GLOBAL_VARIABLE_GUID)
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+ setp.add_argument('--type', '-t', help='variable type (values: file|u8|u16|u32|u64|str)')
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+ setp.add_argument('--data', '-d', help='data or filename')
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+ setp.set_defaults(func=cmd_set)
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+
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+ delp = subp.add_parser('del', help='delete EFI variable')
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+ delp.add_argument('--infile', '-i', required=True, help='file to save the EFI variables')
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+ delp.add_argument('--name', '-n', required=True, help='variable name')
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+ delp.add_argument('--attrs', '-a', help='variable attributes (values: nv,bs,rt,at,ro,aw)')
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+ delp.add_argument('--guid', '-g', help="vendor GUID (default: %s)"%EFI_GLOBAL_VARIABLE_GUID)
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+ delp.set_defaults(func=cmd_del)
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+
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+ signp = subp.add_parser('sign', help='sign time-based EFI payload')
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+ signp.add_argument('--cert', '-c', required=True, help='x509 certificate filename in PEM format')
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+ signp.add_argument('--key', '-k', required=True, help='signing certificate filename in PEM format')
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+ signp.add_argument('--name', '-n', required=True, help='variable name')
|
|
|
+ signp.add_argument('--attrs', '-a', help='variable attributes (values: nv,bs,rt,at,ro,aw)')
|
|
|
+ signp.add_argument('--guid', '-g', help="vendor GUID (default: %s)"%EFI_GLOBAL_VARIABLE_GUID)
|
|
|
+ signp.add_argument('--type', '-t', required=True, help='variable type (values: file|u8|u16|u32|u64|str|nil)')
|
|
|
+ signp.add_argument('--data', '-d', help='data or filename')
|
|
|
+ signp.add_argument('--outfile', '-o', required=True, help='output filename of signed EFI payload')
|
|
|
+ signp.set_defaults(func=cmd_sign)
|
|
|
+
|
|
|
+ args = ap.parse_args()
|
|
|
+ args.func(args)
|
|
|
+
|
|
|
+def group(a, *ns):
|
|
|
+ for n in ns:
|
|
|
+ a = [a[i:i+n] for i in range(0, len(a), n)]
|
|
|
+ return a
|
|
|
+
|
|
|
+def join(a, *cs):
|
|
|
+ return [cs[0].join(join(t, *cs[1:])) for t in a] if cs else a
|
|
|
+
|
|
|
+def hexdump(data):
|
|
|
+ toHex = lambda c: '{:02X}'.format(c)
|
|
|
+ toChr = lambda c: chr(c) if 32 <= c < 127 else '.'
|
|
|
+ make = lambda f, *cs: join(group(list(map(f, data)), 8, 2), *cs)
|
|
|
+ hs = make(toHex, ' ', ' ')
|
|
|
+ cs = make(toChr, ' ', '')
|
|
|
+ for i, (h, c) in enumerate(zip(hs, cs)):
|
|
|
+ print (' {:010X}: {:48} {:16}'.format(i * 16, h, c))
|
|
|
+
|
|
|
+if __name__ == '__main__':
|
|
|
+ main()
|