#!/usr/bin/env python # # Cert: Some extra CERT checkers # # Cppcheck itself handles many CERT rules. Cppcheck warns when there is undefined behaviour. # CERT Homepage: https://www.cert.org/secure-coding/ # # 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 VERIFY = ('-verify' in sys.argv) VERIFY_EXPECTED = [] VERIFY_ACTUAL = [] def reportError(token, severity, msg, id): if VERIFY: VERIFY_ACTUAL.append(str(token.linenr) + ':' + id) else: sys.stderr.write( '[' + token.file + ':' + str(token.linenr) + '] (' + severity + '): ' + msg + ' [' + id + ']\n') def simpleMatch(token, pattern): for p in pattern.split(' '): if not token or token.str != p: return False token = token.next return True 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) def isBitwiseOp(token): return token and (token.str in {'&', '|', '^'}) def isComparisonOp(token): return token and (token.str in {'==', '!=', '>', '>=', '<', '<='}) 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 # 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 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 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( token, 'style', "Comparison of struct padding data " + "(fix either by packing the struct using '#pragma pack' or by rewriting the comparison)", 'cert-EXP42-C') # 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( token, 'style', 'Bitwise operator is used with a Boolean-like operand', 'cert-EXP46-c') # 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 elif token.valueType.type == 'long long': bits = platform.long_long_bit else: continue if token.valueType.sign == 'unsigned': found = False for value in token.astOperand1.values: if value.intvalue < 0: 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 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: if value.intvalue < minval or value.intvalue > maxval: destType = '' if token.valueType.sign: destType = token.valueType.sign + ' ' + token.valueType.type else: destType = token.valueType.type reportError( token, 'style', 'Ensure that integer conversions do not result in lost or misinterpreted data (casting ' + str(value.intvalue) + ' to ' + destType + ')', 'cert-INT31-c') break for arg in sys.argv[1:]: if arg == '-verify': VERIFY = True continue print('Checking ' + arg + '...') data = cppcheckdata.parsedump(arg) 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(' '): if re.match(r'cert-[A-Z][A-Z][A-Z][0-9][0-9].*',word): 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) 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)