UnknownSec Bypass 403

: /usr/share/apport/general-hooks/ [ drwxr-xr-x ]
name : parse_segv.py #!/usr/bin/python3 # Examine the crash files saved by apport to attempt to determine the cause # of a segfault. Currently very very simplistic, and only finds commonly # understood situations for x86/x86_64. # # Copyright 2009-2010 Canonical, Ltd. # Author: Kees Cook <kees@ubuntu.com> # # This program is free software; you can redistribute it and/or modify it # under the terms of the GNU General Public License as published by the # Free Software Foundation; either version 2 of the License, or (at your # option) any later version. See http://www.gnu.org/copyleft/gpl.html for # the full text of the license. import sys, re, logging, io class ParseSegv(object): def __init__(self, registers, disassembly, maps, debug=False): if debug: if sys.version > '3': logging.basicConfig(level=logging.DEBUG, stream=io.TextIOWrapper(sys.stderr, encoding='UTF-8')) else: logging.basicConfig(level=logging.DEBUG, stream=sys.stderr) self.regs = self.parse_regs(registers) self.sp = None for reg in ['rsp', 'esp']: if reg in self.regs: self.sp = self.regs[reg] self.line, self.pc, self.insn, self.src, self.dest = \ self.parse_disassembly(disassembly) self.stack_vma = None self.maps = self.parse_maps(maps) def find_vma(self, addr): for vma in self.maps: if addr >= vma['start'] and addr < vma['end']: return vma return None def parse_maps(self, maps_str): maps = [] for line in maps_str.splitlines(): items = line.strip().split() try: span, perms, bits, dev = items[0:4] except Exception: raise ValueError('Cannot parse maps line: %s' % (line.strip())) if len(items) == 5: name = None else: name = items[5] start, end = [int(x, 16) for x in span.split('-')] if name == '[stack]': self.stack_vma = len(maps) maps.append({'start': start, 'end': end, 'perms': perms, 'name': name}) logging.debug('start: %s, end: %s, perms: %s, name: %s', start, end, perms, name) return maps def parse_regs(self, reg_str): regs = dict() for line in reg_str.splitlines(): reg, hexvalue = line.split()[0:2] regs[reg] = int(hexvalue, 16) logging.debug('%s:0x%08x', reg, regs[reg]) return regs def parse_disassembly(self, disassembly): if not self.regs: raise ValueError('Registers not loaded yet!?') lines = disassembly.splitlines() # Throw away possible 'Dump' gdb report line if len(lines) > 0 and lines[0].startswith('Dump'): lines.pop(0) if len(lines) < 1: raise ValueError('Failed to load empty disassembly') line = lines[0].strip() # Drop GDB 7.1's leading $pc mark if line.startswith('=>'): line = line[2:].strip() logging.debug(line) pc_str = line.split()[0] if pc_str.startswith('0x'): pc = int(pc_str.split(':')[0], 16) else: # Could not identify this instruction line raise ValueError('Could not parse PC "%s" from disassembly line: %s' % (pc_str, line)) logging.debug('pc: 0x%08x', pc) full_insn_str = line.split(':', 1)[1].strip() # Handle invalid memory if 'Cannot access memory at address' in full_insn_str or (full_insn_str == '' and len(lines) == 1): return line, pc, None, None, None # Handle wrapped lines if full_insn_str == '' and lines[1].startswith(' '): line = line + ' ' + lines[1].strip() full_insn_str = line.split(':', 1)[1].strip() insn_parts = full_insn_str.split() # Drop call target names "call 0xb7a805af <_Unwind_Find_FDE@plt+111>" if insn_parts[-1].endswith('>') and insn_parts[-1].startswith('<'): insn_parts.pop(-1) # Attempt to find arguments args_str = '' if len(insn_parts) > 1: args_str = insn_parts.pop(-1) # Assume remainder is the insn itself insn = ' '.join(insn_parts) logging.debug('insn: %s', insn) args = [] src = None dest = None if args_str == '': # Could not find insn args args = None else: logging.debug('args: "%s"', args_str) for m in re.finditer(r'([^,\(]*(\(:?[^\)]+\))*)', args_str): if len(m.group(0)): args.append(m.group(0)) if len(args) > 0: src = args[0] logging.debug('src: %s', src) if len(args) > 1: dest = args[1] logging.debug('dest: %s', dest) # Set up possible implicit memory destinations (stack actions) if insn in ['push', 'pop', 'pushl', 'popl', 'call', 'callq', 'ret', 'retq']: for reg in ['rsp', 'esp']: if reg in self.regs: dest = '(%%%s)' % (reg) break return line, pc, insn, src, dest def validate_vma(self, perm, addr, name): perm_name = {'x': ['executable', 'executing'], 'r': ['readable', 'reading'], 'w': ['writable', 'writing']} vma = self.find_vma(addr) if vma is None: alarmist = 'unknown' if addr < 65536: alarmist = 'NULL' return False, '%s (0x%08x) not located in a known VMA region (needed %s region)!' % (name, addr, perm_name[perm][0]), '%s %s VMA' % (perm_name[perm][1], alarmist) elif perm not in vma['perms']: alarmist = '' if perm == 'x': if 'w' in vma['perms']: alarmist = 'writable ' else: alarmist = 'non-writable ' short = '%s %sVMA %s' % (perm_name[perm][1], alarmist, vma['name']) return False, '%s (0x%08x) in non-%s VMA region: 0x%08x-0x%08x %s %s' % (name, addr, perm_name[perm][0], vma['start'], vma['end'], vma['perms'], vma['name']), short else: return True, '%s (0x%08x) ok' % (name, addr), '%s ok' % (perm_name[perm][1]) def register_value(self, reg): reg_orig = reg # print reg mask = 0 if reg.startswith('%'): # print('%s -> %s' % (reg, reg[1:])) reg = reg[1:] if reg in self.regs: # print('got %s (%d & %d == %d)' % (reg, self.regs[reg], mask, self.regs[reg] & ~mask)) return self.regs[reg] if len(reg) == 2 and reg.endswith('l'): mask |= 0xff00 # print('%s -> %sx' % (reg, reg[0])) reg = '%sx' % reg[0] if reg in self.regs: # print('got %s (%d & %d == %d)' % (reg, self.regs[reg], mask, self.regs[reg] & ~mask)) return self.regs[reg] & ~mask if len(reg) == 2 and reg.endswith('x'): mask |= 0xffff0000 # print('%s -> e%s' % (reg, reg)) reg = 'e%s' % reg if reg in self.regs: # print('got %s (%d & %d == %d)' % (reg, self.regs[reg], mask, self.regs[reg] & ~mask)) return self.regs[reg] & ~mask if len(reg) == 3 and reg.startswith('e'): mask |= 0xffffffff00000000 # print('%s -> r%s' % (reg, reg[1:])) reg = 'r%s' % reg[1:] if reg in self.regs: # print('got %s (%d & %d == %d)' % (reg, self.regs[reg], mask, self.regs[reg] & ~mask)) return self.regs[reg] & ~mask raise ValueError("Could not resolve register '%s'" % (reg_orig)) def calculate_arg(self, arg): # Check for and pre-remove segment offset segment = 0 if arg.startswith('%') and ':' in arg: parts = arg.split(':', 1) segment = self.regs[parts[0][1:]] arg = parts[1] # Handle standard offsets parts = arg.split('(') offset = parts[0] # Handle negative signs sign = 1 if offset.startswith('-'): sign = -1 offset = offset[1:] # Skip call target dereferences if offset.startswith('*'): offset = offset[1:] if len(offset) > 0: if offset.startswith('%'): # Handle the *%REG case add = self.regs[offset[1:]] else: if not offset.startswith('0x'): raise ValueError('Unknown offset literal: %s' % (parts[0])) add = int(offset[2:], 16) * sign else: add = 0 def _reg_val(self, text, val=0): if text.startswith('%'): val = self.regs[text[1:]] elif text == "": val = 0 else: val = int(text) return val # (%ebx, %ecx, 4) style value = 0 if len(parts) > 1: parens = parts[1][0:-1] reg_list = parens.split(',') base = 0 if len(reg_list) > 0: base = _reg_val(self, reg_list[0], base) index = 0 if len(reg_list) > 1: index = _reg_val(self, reg_list[1], index) scale = 1 if len(reg_list) > 2: scale = _reg_val(self, reg_list[2], scale) value = base + index * scale value = segment + value + add if 'esp' in self.regs: # 32bit return value % 0x100000000 else: # 64bit return value % 0x10000000000000000 def report(self): understood = False reason = [] details = ['Segfault happened at: %s' % (self.line)] # Verify PC is in an executable region valid, out, short = self.validate_vma('x', self.pc, 'PC') details.append(out) if not valid: reason.append(short) understood = True if self.insn in ['lea', 'leal']: # Short-circuit for instructions that do not cause vma access details.append('insn (%s) does not access VMA' % (self.insn)) else: # Verify source is readable if self.src: if ':' not in self.src and (self.src[0] in ['%', '$', '*']) and not self.src.startswith('*%'): details.append('source "%s" ok' % (self.src)) else: addr = self.calculate_arg(self.src) valid, out, short = self.validate_vma('r', addr, 'source "%s"' % (self.src)) details.append(out) if not valid: reason.append(short) understood = True # Verify destination is writable if self.dest: if ':' not in self.dest and (self.dest[0] in ['%', '$', '*']): details.append('destination "%s" ok' % (self.dest)) else: addr = self.calculate_arg(self.dest) valid, out, short = self.validate_vma('w', addr, 'destination "%s"' % (self.dest)) details.append(out) if not valid: reason.append(short) understood = True # Handle I/O port operations if self.insn in ['out', 'in'] and not understood: reason.append('disallowed I/O port operation on port %d' % (self.register_value(self.src))) details.append('disallowed I/O port operation on port %d' % (self.register_value(self.src))) understood = True # Note position of SP with regard to "[stack]" VMA if self.sp is not None: if self.stack_vma is not None: if self.sp < self.maps[self.stack_vma]['start']: details.append("Stack memory exhausted (SP below stack segment)") if self.sp >= self.maps[self.stack_vma]['end']: details.append("Stack pointer not within stack segment") if not understood: valid, out, short = self.validate_vma('r', self.sp, 'SP') details.append(out) if not valid: reason.append(short) understood = True if not understood: vma = self.find_vma(self.pc) if vma and (vma['name'] == '[vdso]' or vma['name'] == '[vsyscall]'): reason.append('Reason could not be automatically determined. (Unhandled exception in kernel code?)') details.append('Reason could not be automatically determined. (Unhandled exception in kernel code?)') else: reason.append('Reason could not be automatically determined.') details.append('Reason could not be automatically determined.') return understood, '\n'.join(reason), '\n'.join(details) def add_info(report): # Only interested in segmentation faults... if report.get('Signal', '0') != '11': return needed = ['Signal', 'Architecture', 'Disassembly', 'ProcMaps', 'Registers'] for field in needed: if field not in report: report['SegvAnalysis'] = 'Skipped: missing required field "%s"' % (field) return # Only run on segv for x86 and x86_64... if not report['Architecture'] in ['i386', 'amd64']: return try: segv = ParseSegv(report['Registers'], report['Disassembly'], report['ProcMaps']) understood, reason, details = segv.report() if understood: report['SegvReason'] = reason report['SegvAnalysis'] = details except BaseException as e: report['SegvAnalysis'] = 'Failure: %s' % (str(e)) if __name__ == '__main__': if len(sys.argv) != 4 or sys.argv[1] in ['-h', '--help']: print('To run self-test, run without any arguments (or with -v)') print('To do stand-alone crash parsing:') print(' Usage: %s Registers.txt Disassembly.txt ProcMaps.txt' % (sys.argv[0])) sys.exit(0) segv = ParseSegv(open(sys.argv[1]).read(), open(sys.argv[2]).read(), open(sys.argv[3]).read()) understood, reason, details = segv.report() print('%s\n\n%s' % (reason, details)) rc = 0 if not understood: rc = 1 sys.exit(rc)