cppcheck/addons/cert.py

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#!/usr/bin/env python
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#
# Cert: Some extra CERT checkers
#
# Cppcheck itself handles many CERT rules. Cppcheck warns when there is undefined behaviour.
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# CERT Homepage: https://www.cert.org/secure-coding/
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#
# Example usage of this addon (scan a sourcefile main.cpp)
# cppcheck --dump main.cpp
# python cert.py main.cpp.dump
import cppcheckdata
import sys
import re
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VERIFY = ('-verify' in sys.argv)
VERIFY_EXPECTED = []
VERIFY_ACTUAL = []
CLI = False
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def reportError(token, severity, msg, id):
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if VERIFY:
VERIFY_ACTUAL.append(str(token.linenr) + ':' + id)
else:
msg = '[' + token.file + ':' + str(token.linenr) + ']: (' + severity + ') ' + msg + ' [' + id + ']'
if CLI:
print(msg)
else:
sys.stderr.write(msg + '\n')
def simpleMatch(token, pattern):
for p in pattern.split(' '):
if not token or token.str != p:
return False
token = token.next
return True
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def isUnpackedStruct(token):
if token.valueType is None:
return False
if token.valueType.typeScope is None:
return False
if token.valueType.typeScope.type != "Struct":
return False
startToken = token.valueType.typeScope.bodyStart
linenr = int(startToken.linenr)
for line in open(startToken.file):
linenr -= 1
if linenr == 0:
return True
if linenr < 3 and re.match(r'#pragma\s+pack\s*\(', line):
return False
return True
def isLocalUnpackedStruct(arg):
if arg and arg.str == '&' and not arg.astOperand2:
arg = arg.astOperand1
return arg and arg.variable and (arg.variable.isLocal or arg.variable.isArgument) and isUnpackedStruct(arg)
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def isBitwiseOp(token):
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return token and (token.str in {'&', '|', '^'})
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def isComparisonOp(token):
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return token and (token.str in {'==', '!=', '>', '>=', '<', '<='})
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def isCast(expr):
if not expr or expr.str != '(' or not expr.astOperand1 or expr.astOperand2:
return False
if simpleMatch(expr, '( )'):
return False
return True
def isStandardFunction(token):
if token.function:
return False
prev = token.previous
if prev:
if prev.str == '.':
return False
if prev.str == '::':
prevprev = prev.previous
if prevprev and not prevprev.str == 'std':
return False
return True
# Get function arguments
def getArgumentsRecursive(tok, arguments):
if tok is None:
return
if tok.str == ',':
getArgumentsRecursive(tok.astOperand1, arguments)
getArgumentsRecursive(tok.astOperand2, arguments)
else:
arguments.append(tok)
def getArguments(ftok):
arguments = []
getArgumentsRecursive(ftok.astOperand2, arguments)
return arguments
# EXP05-C
# do not attempt to cast away const
def exp05(data):
# TODO Reuse code in misra rule 11.8
for token in data.tokenlist:
if isCast(token):
# C-style cast
if not token.valueType:
continue
if not token.astOperand1.valueType:
continue
if token.valueType.pointer == 0:
continue
if token.astOperand1.valueType.pointer == 0:
continue
const1 = token.valueType.constness
const2 = token.astOperand1.valueType.constness
if (const1 % 2) < (const2 % 2):
reportError(token, 'style', "Attempt to cast away const", 'cert-EXP05-C')
elif token.str == '(' and token.astOperand1 and token.astOperand2 and token.astOperand1.function:
function = token.astOperand1.function
arguments = getArguments(token)
for argnr, argvar in function.argument.items():
if argnr < 1 or argnr > len(arguments):
continue
if not argvar.isPointer:
continue
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if (argvar.constness % 2) == 1: # data is const
continue
argtok = arguments[argnr - 1]
if not argtok.valueType:
continue
if argtok.valueType.pointer == 0:
continue
const2 = arguments[argnr - 1].valueType.constness
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if (const2 % 2) == 1:
reportError(token, 'style', "Attempt to cast away const", 'cert-EXP05-C')
# EXP42-C
# do not compare padding data
def exp42(data):
for token in data.tokenlist:
if token.str != '(' or not token.astOperand1 or token.astOperand1.str != 'memcmp':
continue
arg1 = None
arg2 = None
if token.astOperand2 and token.astOperand2.str == ',':
if token.astOperand2.astOperand1 and token.astOperand2.astOperand1.str == ',':
arg1 = token.astOperand2.astOperand1.astOperand1
arg2 = token.astOperand2.astOperand1.astOperand2
if isLocalUnpackedStruct(arg1) or isLocalUnpackedStruct(arg2):
reportError(
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token, 'style', "Comparison of struct padding data " +
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"(fix either by packing the struct using '#pragma pack' or by rewriting the comparison)", 'cert-EXP42-C')
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# EXP46-C
# Do not use a bitwise operator with a Boolean-like operand
# int x = (a == b) & c;
def exp46(data):
for token in data.tokenlist:
if isBitwiseOp(token) and (isComparisonOp(token.astOperand1) or isComparisonOp(token.astOperand2)):
reportError(
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token, 'style', 'Bitwise operator is used with a Boolean-like operand', 'cert-EXP46-c')
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# INT31-C
# Ensure that integer conversions do not result in lost or misinterpreted data
def int31(data, platform):
if not platform:
return
for token in data.tokenlist:
if not isCast(token):
continue
if not token.valueType or not token.astOperand1.values:
continue
bits = None
if token.valueType.type == 'char':
bits = platform.char_bit
elif token.valueType.type == 'short':
bits = platform.short_bit
elif token.valueType.type == 'int':
bits = platform.int_bit
elif token.valueType.type == 'long':
bits = platform.long_bit
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elif token.valueType.type == 'long long':
bits = platform.long_long_bit
else:
continue
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if token.valueType.sign == 'unsigned':
found = False
for value in token.astOperand1.values:
if value.intvalue and value.intvalue < 0:
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found = True
reportError(
token,
'style',
'Ensure that integer conversions do not result in lost or misinterpreted data (casting ' + str(value.intvalue) + ' to unsigned ' + token.valueType.type + ')',
'cert-INT31-c')
break
if found:
continue
if bits >= 64:
continue
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minval = 0
maxval = 1
if token.valueType.sign == 'signed':
minval = -(1 << (bits - 1))
maxval = ((1 << (bits - 1)) - 1)
else:
minval = 0
maxval = ((1 << bits) - 1)
for value in token.astOperand1.values:
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if value.intvalue and (value.intvalue < minval or value.intvalue > maxval):
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destType = ''
if token.valueType.sign:
destType = token.valueType.sign + ' ' + token.valueType.type
else:
destType = token.valueType.type
reportError(
token,
'style',
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'Ensure that integer conversions do not result in lost or misinterpreted data (casting ' + str(value.intvalue) + ' to ' + destType + ')',
'cert-INT31-c')
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break
# MSC30-C
# Do not use the rand() function for generating pseudorandom numbers
def msc30(data):
for token in data.tokenlist:
if simpleMatch(token, "rand ( )") and isStandardFunction(token):
reportError(token, 'style', 'Do not use the rand() function for generating pseudorandom numbers', 'cert-MSC30-c')
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for arg in sys.argv[1:]:
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if arg == '-verify':
VERIFY = True
continue
if arg == '--cli':
CLI = True
continue
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print('Checking ' + arg + '...')
data = cppcheckdata.parsedump(arg)
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if VERIFY:
VERIFY_ACTUAL = []
VERIFY_EXPECTED = []
for tok in data.rawTokens:
if tok.str.startswith('//') and 'TODO' not in tok.str:
for word in tok.str[2:].split(' '):
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if re.match(r'cert-[A-Z][A-Z][A-Z][0-9][0-9].*',word):
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VERIFY_EXPECTED.append(str(tok.linenr) + ':' + word)
for cfg in data.configurations:
if len(data.configurations) > 1:
print('Checking ' + arg + ', config "' + cfg.name + '"...')
exp05(cfg)
exp42(cfg)
exp46(cfg)
int31(cfg, data.platform)
msc30(cfg)
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if VERIFY:
for expected in VERIFY_EXPECTED:
if expected not in VERIFY_ACTUAL:
print('Expected but not seen: ' + expected)
sys.exit(1)
for actual in VERIFY_ACTUAL:
if actual not in VERIFY_EXPECTED:
print('Not expected: ' + actual)
sys.exit(1)