/usr/share/fusil/fuzzers/fusil-libc-printf is in fusil 1.4-1.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
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# -*- coding: UTF-8 -*-
"""
Generate valid printf format to test GNU libc implementation
Written using manual page to get all options.
"""
FORMAT_TO_SIZE = {
's': 'str',
'S': 'wide str',
'c': 'char',
'C': 'wide char',
'p': 'pointer',
'm': None,
'%': None,
'n': 'write',
'a': 'double',
'A': 'double',
'e': 'double',
'E': 'double',
'f': 'double',
'F': 'double',
'g': 'double',
'G': 'double',
'i': 'int',
'u': 'int',
'd': 'int',
'x': 'int',
'X': 'int',
'o': 'int',
'O': 'int',
}
from fusil.application import Application
from optparse import OptionGroup
from random import choice, randint
from fusil.c_tools import encodeUTF32, quoteString, CodeC, CompilerError
from fusil.process.create import CreateProcess
from fusil.process.watch import WatchProcess
from fusil.project_agent import ProjectAgent
from ptrace.compatibility import any
HELLO_UTF32 = encodeUTF32(u"Héllô")+"\0"*4
class Fuzzer(Application):
NAME = "printf"
def createFuzzerOptions(self, parser):
options = OptionGroup(parser, "printf fuzzer")
options.add_option("--asprintf", help="Don't use asprintf()",
action="store_true")
return options
def setupProject(self):
project = self.project
printf = GeneratePrintfProgram(project, self.options)
printf.max_nb_arg = 10
# AVOID printf("%*d", 10000000, 42) crash
#printf.max_width = 10*1000
# AVOID "%.10000000s" crash
#printf.max_precision = 10*1000
# AVOID "%10000000hc" crash
del printf.modifiers['char']['h']
# AVOID "%qp" and "%llC" crashes
for size in ('char', 'wide char', 'pointer'):
for key in ('ll', 'q', 'j'):
del printf.modifiers[size][key]
process = PrintfProcess(project, name="printf", stdout='null')
WatchProcess(process)
class PrintfProcess(CreateProcess):
def on_printf_program(self, program):
self.cmdline.arguments = [program]
self.createProcess()
class GeneratePrintfArguments:
def __init__(self, printf):
self.printf = printf
def genFormat(self, argument_index):
# choose type
prefix = None
type = choice(self.printf.types)
size = FORMAT_TO_SIZE[type]
format = ['%']
# add attribute
format.append(choice(self.printf.format_attr))
# add width
rnd = randint(0, 2)
if rnd == 1:
format.append(str(randint(0, self.printf.max_width)))
elif rnd == 2:
width = randint(self.printf.min_width, self.printf.max_width)
prefix = '/* width of x%s */ %s' % (argument_index, width)
format.append('*')
#if randint(0, 1) == 1:
# format.append('*')
#else:
# format.append('%s$*%s$' % (
# argument_index+2, argument_index+1))
# add precision
if randint(0, 1) == 1:
format.append('.%s' % randint(0, self.printf.max_precision))
# add modifier
if size in self.printf.modifiers:
modifiers = self.printf.modifiers[size]
keys = modifiers.keys()+[None]
modifier = choice(keys)
if modifier:
format.append(modifier)
size = modifiers[modifier]
# add type
format.append(type)
return format, prefix, size
def generate(self, nb_arg):
text = []
arguments = []
for index in xrange(nb_arg):
if text:
text.append(' -- ')
# Generate format and value
format, prefix, size = self.genFormat(index)
if size:
value = self.printf.values[size]
else:
value = None
# Append format and value
format = ''.join(format)
text.append('x%s' % index + '=' + format)
if prefix:
arguments.append(prefix)
if value is not None:
if value == "&written":
arguments.append('/* written bytes at x%s */ ' % index + value)
else:
arguments.append('/* x%s value */ ' % index + value)
text.append('\n')
return [quoteString(''.join(text))]+arguments
class GeneratePrintfProgram(ProjectAgent):
def __init__(self, project, options):
ProjectAgent.__init__(self, project, "gen printf")
self.has_asprintf = (not options.asprintf)
# --- printf options ---
self.min_nb_arg = 1
self.max_nb_arg = 6
self.types = 'aAcCdeEfFgGimnopuxXsS%'
self.format_attr = ('#', '0', '-', ' ', '+', "'", 'I', '')
self.min_width = 0
self.max_width = 10*1000*1000
self.max_precision = 10*1000*1000
self.values = {
'str': quoteString('Hello'),
'wide str': quoteString(HELLO_UTF32),
'char': "'A'",
'wide char': "(wchar_t)322", # 'ł'
'double': "(double)3.14",
'short': "(short)7",
'pointer': "(void *)0xDEADBEEF",
'int': "(int)42",
'intmax': "(intmax_t)232",
'size_t': "(size_t)-1",
'long': "(long)1234567890",
'long long': "(long long)10101010",
'ptrdiff_t': "(ptrdiff_t)100",
'write': "&written",
'long double': '(long double)5.92',
}
int_modifiers = {
'hh': 'char',
'h': 'short',
'l': 'long',
'll': 'long long',
'q': 'long long',
'j': 'intmax',
'z': 'size_t',
't': 'ptrdiff_t',
}
self.modifiers = {
'int': dict(int_modifiers),
'char': dict(int_modifiers),
'wide char': dict(int_modifiers),
'pointer': dict(int_modifiers),
'str': {'l': 'wide str'},
'wide str': {'l': 'wide str'},
'double': {'L': 'long double'},
}
def on_session_start(self):
self.use_locale = (randint(0, 1) == 0)
if self.has_asprintf:
self.use_asprintf = (randint(0, 1) == 0)
else:
self.use_asprintf = False
# Generate printf() arguments
nb_arg = randint(self.min_nb_arg, self.max_nb_arg)
arguments = GeneratePrintfArguments(self).generate(nb_arg)
self.info("Arguments: %s" % repr(arguments[1:]))
self.info("Format: %s" % repr(arguments[0]))
# Write C code to reproduce the bug
code = CodeC()
self.writeC(code, arguments)
session = self.session()
self.c_filename = session.createFilename("printf.c")
self.program_filename = session.createFilename("printf")
try:
code.compile(self, self.c_filename, self.program_filename, options="-Wno-format")
except CompilerError, err:
self.error("Compiler error: %s" % err)
self.send('project_stop')
return
self.send('printf_program', self.program_filename)
def writeC(self, code, arguments):
if self.use_asprintf:
code.gnu_source = True
code.includes = [
'<stddef.h>', # for ptrdiff_t
'<stdint.h>', # for intmax_t
'<stdio.h>', # for printf()
]
if self.use_locale:
code.includes.append('<locale.h>') # for setlocale()
main = code.addMain()
if any( "&written" in text for text in arguments):
main.variables.append('int written')
if self.use_locale:
main.callFunction('setlocale', ['LC_ALL', '""'])
if self.use_asprintf:
main.variables.append("char *text = NULL")
arguments.insert(0, "&text")
name = "asprintf"
else:
name = "printf"
main.callFunction(name, arguments)
if __name__ == "__main__":
Fuzzer().main()
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