mirror of
https://github.com/chipsec/chipsec
synced 2026-06-08 13:31:00 +00:00
brentholtsclaw
f7fe1be074
E231, E201, E226 Signed-off-by: brentholtsclaw <brent.holtsclaw@intel.com>
89 lines
3.9 KiB
Python
89 lines
3.9 KiB
Python
#CHIPSEC: Platform Security Assessment Framework
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#Copyright (c) 2010-2020, Intel Corporation
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#
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#This program is free software; you can redistribute it and/or
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#modify it under the terms of the GNU General Public License
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#as published by the Free Software Foundation; Version 2.
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#
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#This program is distributed in the hope that it will be useful,
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#but WITHOUT ANY WARRANTY; without even the implied warranty of
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#MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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#GNU General Public License for more details.
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#
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#You should have received a copy of the GNU General Public License
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#along with this program; if not, write to the Free Software
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#Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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#
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#Contact information:
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#chipsec@intel.com
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#
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"""
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DEFCON 16: `Bypassing Pre-boot Authentication Passwords by Instrumenting the BIOS Keyboard Buffer <https://www.defcon.org/images/defcon-16/dc16-presentations/brossard/defcon-16-brossard-wp.pdf>`_ by Jonathan Brossard
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Checks for BIOS/HDD password exposure through BIOS keyboard buffer.
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Checks for exposure of pre-boot passwords (BIOS/HDD/pre-bot authentication SW) in the BIOS keyboard buffer.
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"""
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from chipsec.module_common import BaseModule, ModuleResult, MTAG_BIOS
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from chipsec.logger import print_buffer
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TAGS = [MTAG_BIOS]
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COMMON_FILL_PTRN = "".join( ['{:1}'.format((chr(x + 0x1E))) for x in range(32)] )
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class bios_kbrd_buffer(BaseModule):
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def __init__(self):
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BaseModule.__init__(self)
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def is_supported(self):
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return True
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def check_BIOS_keyboard_buffer(self):
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self.logger.start_test( "Pre-boot Passwords in the BIOS Keyboard Buffer" )
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bios_kbrd_buf_clear = 0
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kbrd_buf_head = self.cs.mem.read_physical_mem_dword( 0x41A ) & 0x000000FF
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kbrd_buf_tail = self.cs.mem.read_physical_mem_dword( 0x41C ) & 0x000000FF
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self.logger.log( "[*] Keyboard buffer head pointer = 0x{:X} (at 0x41A), tail pointer = 0x{:X} (at 0x41C)".format(kbrd_buf_head, kbrd_buf_tail) )
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bios_kbrd_buf = self.cs.mem.read_physical_mem( 0x41E, 32 )
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self.logger.log( "[*] Keyboard buffer contents (at 0x41E):" )
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bios_kbrd_buf = bios_kbrd_buf.decode('latin_1')
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print_buffer( bios_kbrd_buf )
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has_contents = False
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if COMMON_FILL_PTRN == bios_kbrd_buf:
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self.logger.log_passed_check( "Keyboard buffer is filled with common fill pattern" )
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return ModuleResult.PASSED
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for x in bios_kbrd_buf:
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if ( "\x00" != x and "\x20" != x ):
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has_contents = True
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break
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if (0x1E < kbrd_buf_tail) and (kbrd_buf_tail <= 0x1E +32):
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#has_contents = True
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self.logger.log_bad( "Keyboard buffer tail points inside the buffer (= 0x{:X})".format(kbrd_buf_tail) )
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self.logger.log( " It may potentially expose lengths of pre-boot passwords. Was your password {:d} characters long?".format((kbrd_buf_tail +2 - 0x1E) //2) )
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self.logger.log( "[*] Checking contents of the keyboard buffer..\n" )
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if has_contents: self.logger.log_warn_check( "Keyboard buffer is not empty. The test cannot determine conclusively if it contains pre-boot passwords.\n The contents might have not been cleared by pre-boot firmware or overwritten with garbage.\n Visually inspect the contents of keyboard buffer for pre-boot passwords (BIOS, HDD, full-disk encryption)." )
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else: self.logger.log_passed_check( "Keyboard buffer looks empty. Pre-boot passwords don't seem to be exposed" )
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return (ModuleResult.WARNING if has_contents else ModuleResult.PASSED)
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# --------------------------------------------------------------------------
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# run( module_argv )
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# Required function: run here all tests from this module
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# --------------------------------------------------------------------------
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def run( self, module_argv ):
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return self.check_BIOS_keyboard_buffer()
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