LXR uboot/tools/efivar.py

   1#!/usr/bin/env python3
   2## SPDX-License-Identifier: GPL-2.0-only
   3#
   4# EFI variable store utilities.
   5#
   6# (c) 2020 Paulo Alcantara <palcantara@suse.de>
   7#
   8
   9import os
  10import struct
  11import uuid
  12import time
  13import zlib
  14import argparse
  15from OpenSSL import crypto
  16
  17# U-Boot variable store format (version 1)
  18UBOOT_EFI_VAR_FILE_MAGIC = 0x0161566966456255
  19
  20# UEFI variable attributes
  21EFI_VARIABLE_NON_VOLATILE = 0x1
  22EFI_VARIABLE_BOOTSERVICE_ACCESS = 0x2
  23EFI_VARIABLE_RUNTIME_ACCESS = 0x4
  24EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS = 0x10
  25EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS = 0x20
  26EFI_VARIABLE_READ_ONLY = 1 << 31
  27NV_BS = EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS
  28NV_BS_RT = NV_BS | EFI_VARIABLE_RUNTIME_ACCESS
  29NV_BS_RT_AT = NV_BS_RT | EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS
  30DEFAULT_VAR_ATTRS = NV_BS_RT
  31
  32# vendor GUIDs
  33EFI_GLOBAL_VARIABLE_GUID = '8be4df61-93ca-11d2-aa0d-00e098032b8c'
  34EFI_IMAGE_SECURITY_DATABASE_GUID = 'd719b2cb-3d3a-4596-a3bc-dad00e67656f'
  35EFI_CERT_TYPE_PKCS7_GUID = '4aafd29d-68df-49ee-8aa9-347d375665a7'
  36WIN_CERT_TYPE_EFI_GUID = 0x0ef1
  37WIN_CERT_REVISION = 0x0200
  38
  39var_attrs = {
  40        'NV': EFI_VARIABLE_NON_VOLATILE,
  41        'BS': EFI_VARIABLE_BOOTSERVICE_ACCESS,
  42        'RT': EFI_VARIABLE_RUNTIME_ACCESS,
  43        'AT': EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS,
  44        'RO': EFI_VARIABLE_READ_ONLY,
  45        'AW': EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS,
  46}
  47
  48var_guids = {
  49        'EFI_GLOBAL_VARIABLE_GUID': EFI_GLOBAL_VARIABLE_GUID,
  50        'EFI_IMAGE_SECURITY_DATABASE_GUID': EFI_IMAGE_SECURITY_DATABASE_GUID,
  51}
  52
  53class EfiStruct:
  54    # struct efi_var_file
  55    var_file_fmt = '<QQLL'
  56    var_file_size = struct.calcsize(var_file_fmt)
  57    # struct efi_var_entry
  58    var_entry_fmt = '<LLQ16s'
  59    var_entry_size = struct.calcsize(var_entry_fmt)
  60    # struct efi_time
  61    var_time_fmt = '<H6BLh2B'
  62    var_time_size = struct.calcsize(var_time_fmt)
  63    # WIN_CERTIFICATE
  64    var_win_cert_fmt = '<L2H'
  65    var_win_cert_size = struct.calcsize(var_win_cert_fmt)
  66    # WIN_CERTIFICATE_UEFI_GUID
  67    var_win_cert_uefi_guid_fmt = var_win_cert_fmt+'16s'
  68    var_win_cert_uefi_guid_size = struct.calcsize(var_win_cert_uefi_guid_fmt)
  69
  70class EfiVariable:
  71    def __init__(self, size, attrs, time, guid, name, data):
  72        self.size = size
  73        self.attrs = attrs
  74        self.time = time
  75        self.guid = guid
  76        self.name = name
  77        self.data = data
  78
  79def calc_crc32(buf):
  80    return zlib.crc32(buf) & 0xffffffff
  81
  82class EfiVariableStore:
  83    def __init__(self, infile):
  84        self.infile = infile
  85        self.efi = EfiStruct()
  86        if os.path.exists(self.infile) and os.stat(self.infile).st_size > self.efi.var_file_size:
  87            with open(self.infile, 'rb') as f:
  88                buf = f.read()
  89                self._check_header(buf)
  90                self.ents = buf[self.efi.var_file_size:]
  91        else:
  92            self.ents = bytearray()
  93
  94    def _check_header(self, buf):
  95        hdr = struct.unpack_from(self.efi.var_file_fmt, buf, 0)
  96        magic, crc32 = hdr[1], hdr[3]
  97
  98        if magic != UBOOT_EFI_VAR_FILE_MAGIC:
  99            print("err: invalid magic number: %s"%hex(magic))
 100            exit(1)
 101        if crc32 != calc_crc32(buf[self.efi.var_file_size:]):
 102            print("err: invalid crc32: %s"%hex(crc32))
 103            exit(1)
 104
 105    def _get_var_name(self, buf):
 106        name = ''
 107        for i in range(0, len(buf) - 1, 2):
 108            if not buf[i] and not buf[i+1]:
 109                break
 110            name += chr(buf[i])
 111        return ''.join([chr(x) for x in name.encode('utf_16_le') if x]), i + 2
 112
 113    def _next_var(self, offs=0):
 114        size, attrs, time, guid = struct.unpack_from(self.efi.var_entry_fmt, self.ents, offs)
 115        data_fmt = str(size)+"s"
 116        offs += self.efi.var_entry_size
 117        name, namelen = self._get_var_name(self.ents[offs:])
 118        offs += namelen
 119        data = struct.unpack_from(data_fmt, self.ents, offs)[0]
 120        # offset to next 8-byte aligned variable entry
 121        offs = (offs + len(data) + 7) & ~7
 122        return EfiVariable(size, attrs, time, uuid.UUID(bytes_le=guid), name, data), offs
 123
 124    def __iter__(self):
 125        self.offs = 0
 126        return self
 127
 128    def __next__(self):
 129        if self.offs < len(self.ents):
 130            var, noffs = self._next_var(self.offs)
 131            self.offs = noffs
 132            return var
 133        else:
 134            raise StopIteration
 135
 136    def __len__(self):
 137        return len(self.ents)
 138
 139    def _set_var(self, guid, name_data, size, attrs, tsec):
 140        ent = struct.pack(self.efi.var_entry_fmt,
 141                          size,
 142                          attrs,
 143                          tsec,
 144                          uuid.UUID(guid).bytes_le)
 145        ent += name_data
 146        self.ents += ent
 147
 148    def del_var(self, guid, name, attrs):
 149        offs = 0
 150        while offs < len(self.ents):
 151            var, loffs = self._next_var(offs)
 152            if var.name == name and str(var.guid) == guid:
 153                if var.attrs != attrs:
 154                    print("err: attributes don't match")
 155                    exit(1)
 156                self.ents = self.ents[:offs] + self.ents[loffs:]
 157                return
 158            offs = loffs
 159        print("err: variable not found")
 160        exit(1)
 161
 162    def set_var(self, guid, name, data, size, attrs):
 163        offs = 0
 164        while offs < len(self.ents):
 165            var, loffs = self._next_var(offs)
 166            if var.name == name and str(var.guid) == guid:
 167                if var.attrs != attrs:
 168                    print("err: attributes don't match")
 169                    exit(1)
 170                # make room for updating var
 171                self.ents = self.ents[:offs] + self.ents[loffs:]
 172                break
 173            offs = loffs
 174
 175        tsec = int(time.time()) if attrs & EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS else 0
 176        nd = name.encode('utf_16_le') + b"\x00\x00" + data
 177        # U-Boot variable format requires the name + data blob to be 8-byte aligned
 178        pad = ((len(nd) + 7) & ~7) - len(nd)
 179        nd += bytes([0] * pad)
 180
 181        return self._set_var(guid, nd, size, attrs, tsec)
 182
 183    def save(self):
 184        hdr = struct.pack(self.efi.var_file_fmt,
 185                          0,
 186                          UBOOT_EFI_VAR_FILE_MAGIC,
 187                          len(self.ents) + self.efi.var_file_size,
 188                          calc_crc32(self.ents))
 189
 190        with open(self.infile, 'wb') as f:
 191            f.write(hdr)
 192            f.write(self.ents)
 193
 194def parse_attrs(attrs):
 195    v = DEFAULT_VAR_ATTRS
 196    if attrs:
 197        v = 0
 198        for i in attrs.split(','):
 199            v |= var_attrs[i.upper()]
 200    return v
 201
 202def parse_data(val, vtype):
 203    if not val or not vtype:
 204        return None, 0
 205    fmt = { 'u8': '<B', 'u16': '<H', 'u32': '<L', 'u64': '<Q' }
 206    if vtype.lower() == 'file':
 207        with open(val, 'rb') as f:
 208            data = f.read()
 209            return data, len(data)
 210    if vtype.lower() == 'str':
 211        data = val.encode('utf-8')
 212        return data, len(data)
 213    if vtype.lower() == 'nil':
 214        return None, 0
 215    i = fmt[vtype.lower()]
 216    return struct.pack(i, int(val)), struct.calcsize(i)
 217
 218def parse_args(args):
 219    name = args.name
 220    attrs = parse_attrs(args.attrs)
 221    guid = args.guid if args.guid else EFI_GLOBAL_VARIABLE_GUID
 222
 223    if name.lower() == 'db' or name.lower() == 'dbx':
 224        name = name.lower()
 225        guid = EFI_IMAGE_SECURITY_DATABASE_GUID
 226        attrs = NV_BS_RT_AT
 227    elif name.lower() == 'pk' or name.lower() == 'kek':
 228        name = name.upper()
 229        guid = EFI_GLOBAL_VARIABLE_GUID
 230        attrs = NV_BS_RT_AT
 231
 232    data, size = parse_data(args.data, args.type)
 233    return guid, name, attrs, data, size
 234
 235def cmd_set(args):
 236    env = EfiVariableStore(args.infile)
 237    guid, name, attrs, data, size = parse_args(args)
 238    env.set_var(guid=guid, name=name, data=data, size=size, attrs=attrs)
 239    env.save()
 240
 241def print_var(var):
 242    print(var.name+':')
 243    print("    "+str(var.guid)+' '+''.join([x for x in var_guids if str(var.guid) == var_guids[x]]))
 244    print("    "+'|'.join([x for x in var_attrs if var.attrs & var_attrs[x]])+", DataSize = %s"%hex(var.size))
 245    hexdump(var.data)
 246
 247def cmd_print(args):
 248    env = EfiVariableStore(args.infile)
 249    if not args.name and not args.guid and not len(env):
 250        return
 251
 252    found = False
 253    for var in env:
 254        if not args.name:
 255            if args.guid and args.guid != str(var.guid):
 256                continue
 257            print_var(var)
 258            found = True
 259        else:
 260            if args.name != var.name or (args.guid and args.guid != str(var.guid)):
 261                continue
 262            print_var(var)
 263            found = True
 264
 265    if not found:
 266        print("err: variable not found")
 267        exit(1)
 268
 269def cmd_del(args):
 270    env = EfiVariableStore(args.infile)
 271    attrs = parse_attrs(args.attrs)
 272    guid = args.guid if args.guid else EFI_GLOBAL_VARIABLE_GUID
 273    env.del_var(guid, args.name, attrs)
 274    env.save()
 275
 276def pkcs7_sign(cert, key, buf):
 277    with open(cert, 'r') as f:
 278        crt = crypto.load_certificate(crypto.FILETYPE_PEM, f.read())
 279    with open(key, 'r') as f:
 280        pkey = crypto.load_privatekey(crypto.FILETYPE_PEM, f.read())
 281
 282    PKCS7_BINARY = 0x80
 283    PKCS7_DETACHED = 0x40
 284    PKCS7_NOATTR = 0x100
 285
 286    bio_in = crypto._new_mem_buf(buf)
 287    p7 = crypto._lib.PKCS7_sign(crt._x509, pkey._pkey, crypto._ffi.NULL, bio_in,
 288                                PKCS7_BINARY|PKCS7_DETACHED|PKCS7_NOATTR)
 289    bio_out = crypto._new_mem_buf()
 290    crypto._lib.i2d_PKCS7_bio(bio_out, p7)
 291    return crypto._bio_to_string(bio_out)
 292
 293# UEFI 2.8 Errata B "8.2.2 Using the EFI_VARIABLE_AUTHENTICATION_2 descriptor"
 294def cmd_sign(args):
 295    guid, name, attrs, data, _ = parse_args(args)
 296    attrs |= EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS
 297    efi = EfiStruct()
 298
 299    tm = time.localtime()
 300    etime = struct.pack(efi.var_time_fmt,
 301                        tm.tm_year, tm.tm_mon, tm.tm_mday,
 302                        tm.tm_hour, tm.tm_min, tm.tm_sec,
 303                        0, 0, 0, 0, 0)
 304
 305    buf = name.encode('utf_16_le') + uuid.UUID(guid).bytes_le + attrs.to_bytes(4, byteorder='little') + etime
 306    if data:
 307        buf += data
 308    sig = pkcs7_sign(args.cert, args.key, buf)
 309
 310    desc = struct.pack(efi.var_win_cert_uefi_guid_fmt,
 311                       efi.var_win_cert_uefi_guid_size + len(sig),
 312                       WIN_CERT_REVISION,
 313                       WIN_CERT_TYPE_EFI_GUID,
 314                       uuid.UUID(EFI_CERT_TYPE_PKCS7_GUID).bytes_le)
 315
 316    with open(args.outfile, 'wb') as f:
 317        if data:
 318            f.write(etime + desc + sig + data)
 319        else:
 320            f.write(etime + desc + sig)
 321
 322def main():
 323    ap = argparse.ArgumentParser(description='EFI variable store utilities')
 324    subp = ap.add_subparsers(help="sub-command help")
 325
 326    printp = subp.add_parser('print', help='get/list EFI variables')
 327    printp.add_argument('--infile', '-i', required=True, help='file to save the EFI variables')
 328    printp.add_argument('--name', '-n', help='variable name')
 329    printp.add_argument('--guid', '-g', help='vendor GUID')
 330    printp.set_defaults(func=cmd_print)
 331
 332    setp = subp.add_parser('set', help='set EFI variable')
 333    setp.add_argument('--infile', '-i', required=True, help='file to save the EFI variables')
 334    setp.add_argument('--name', '-n', required=True, help='variable name')
 335    setp.add_argument('--attrs', '-a', help='variable attributes (values: nv,bs,rt,at,ro,aw)')
 336    setp.add_argument('--guid', '-g', help="vendor GUID (default: %s)"%EFI_GLOBAL_VARIABLE_GUID)
 337    setp.add_argument('--type', '-t', help='variable type (values: file|u8|u16|u32|u64|str)')
 338    setp.add_argument('--data', '-d', help='data or filename')
 339    setp.set_defaults(func=cmd_set)
 340
 341    delp = subp.add_parser('del', help='delete EFI variable')
 342    delp.add_argument('--infile', '-i', required=True, help='file to save the EFI variables')
 343    delp.add_argument('--name', '-n', required=True, help='variable name')
 344    delp.add_argument('--attrs', '-a', help='variable attributes (values: nv,bs,rt,at,ro,aw)')
 345    delp.add_argument('--guid', '-g', help="vendor GUID (default: %s)"%EFI_GLOBAL_VARIABLE_GUID)
 346    delp.set_defaults(func=cmd_del)
 347
 348    signp = subp.add_parser('sign', help='sign time-based EFI payload')
 349    signp.add_argument('--cert', '-c', required=True, help='x509 certificate filename in PEM format')
 350    signp.add_argument('--key', '-k', required=True, help='signing certificate filename in PEM format')
 351    signp.add_argument('--name', '-n', required=True, help='variable name')
 352    signp.add_argument('--attrs', '-a', help='variable attributes (values: nv,bs,rt,at,ro,aw)')
 353    signp.add_argument('--guid', '-g', help="vendor GUID (default: %s)"%EFI_GLOBAL_VARIABLE_GUID)
 354    signp.add_argument('--type', '-t', required=True, help='variable type (values: file|u8|u16|u32|u64|str|nil)')
 355    signp.add_argument('--data', '-d', help='data or filename')
 356    signp.add_argument('--outfile', '-o', required=True, help='output filename of signed EFI payload')
 357    signp.set_defaults(func=cmd_sign)
 358
 359    args = ap.parse_args()
 360    if hasattr(args, "func"):
 361        args.func(args)
 362    else:
 363        ap.print_help()
 364
 365def group(a, *ns):
 366    for n in ns:
 367        a = [a[i:i+n] for i in range(0, len(a), n)]
 368    return a
 369
 370def join(a, *cs):
 371    return [cs[0].join(join(t, *cs[1:])) for t in a] if cs else a
 372
 373def hexdump(data):
 374    toHex = lambda c: '{:02X}'.format(c)
 375    toChr = lambda c: chr(c) if 32 <= c < 127 else '.'
 376    make = lambda f, *cs: join(group(list(map(f, data)), 8, 2), *cs)
 377    hs = make(toHex, '  ', ' ')
 378    cs = make(toChr, ' ', '')
 379    for i, (h, c) in enumerate(zip(hs, cs)):
 380        print ('    {:010X}: {:48}  {:16}'.format(i * 16, h, c))
 381
 382if __name__ == '__main__':
 383    main()
 384