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![Heinrich Schuchardt](/assets/img/avatar_default.png)
Unused variables should be called '_'. Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de> Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
384 lines
14 KiB
Python
Executable File
384 lines
14 KiB
Python
Executable File
#!/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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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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# U-Boot variable store format (version 1)
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UBOOT_EFI_VAR_FILE_MAGIC = 0x0161566966456255
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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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# 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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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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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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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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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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def calc_crc32(buf):
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return zlib.crc32(buf) & 0xffffffff
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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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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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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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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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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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def __iter__(self):
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self.offs = 0
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return self
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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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def __len__(self):
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return len(self.ents)
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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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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) == 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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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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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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return self._set_var(guid, nd, size, attrs, tsec)
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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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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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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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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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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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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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data, size = parse_data(args.data, args.type)
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return guid, name, attrs, data, size
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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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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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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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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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if not found:
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print("err: variable not found")
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exit(1)
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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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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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PKCS7_BINARY = 0x80
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PKCS7_DETACHED = 0x40
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PKCS7_NOATTR = 0x100
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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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# 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, _ = 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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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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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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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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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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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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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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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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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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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')
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signp.add_argument('--attrs', '-a', help='variable attributes (values: nv,bs,rt,at,ro,aw)')
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signp.add_argument('--guid', '-g', help="vendor GUID (default: %s)"%EFI_GLOBAL_VARIABLE_GUID)
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signp.add_argument('--type', '-t', required=True, help='variable type (values: file|u8|u16|u32|u64|str|nil)')
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signp.add_argument('--data', '-d', help='data or filename')
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signp.add_argument('--outfile', '-o', required=True, help='output filename of signed EFI payload')
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signp.set_defaults(func=cmd_sign)
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args = ap.parse_args()
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if hasattr(args, "func"):
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args.func(args)
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else:
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ap.print_help()
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def group(a, *ns):
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for n in ns:
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a = [a[i:i+n] for i in range(0, len(a), n)]
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return a
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def join(a, *cs):
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return [cs[0].join(join(t, *cs[1:])) for t in a] if cs else a
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def hexdump(data):
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toHex = lambda c: '{:02X}'.format(c)
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toChr = lambda c: chr(c) if 32 <= c < 127 else '.'
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make = lambda f, *cs: join(group(list(map(f, data)), 8, 2), *cs)
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hs = make(toHex, ' ', ' ')
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cs = make(toChr, ' ', '')
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for i, (h, c) in enumerate(zip(hs, cs)):
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print (' {:010X}: {:48} {:16}'.format(i * 16, h, c))
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if __name__ == '__main__':
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main()
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