/* * Cppcheck - A tool for static C/C++ code analysis * Copyright (C) 2007-2011 Daniel Marjamäki and Cppcheck team. * * 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 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see . */ //--------------------------------------------------------------------------- // Buffer overrun.. //--------------------------------------------------------------------------- #include "checkbufferoverrun.h" #include "tokenize.h" #include "errorlogger.h" #include "mathlib.h" #include #include #include #include #include #include #include // <- assert #include // <- strtoul //--------------------------------------------------------------------------- // Register this check class (by creating a static instance of it) namespace { CheckBufferOverrun instance; } //--------------------------------------------------------------------------- void CheckBufferOverrun::arrayIndexOutOfBounds(const Token *tok, MathLib::bigint size, MathLib::bigint index) { if (size >= 1) { std::ostringstream errmsg; errmsg << "Array '"; if (tok) errmsg << tok->str(); else errmsg << "array"; errmsg << "[" << size << "]' index " << index << " out of bounds"; reportError(tok, Severity::error, "arrayIndexOutOfBounds", errmsg.str().c_str()); } } void CheckBufferOverrun::arrayIndexOutOfBounds(const Token *tok, const ArrayInfo &arrayInfo, const std::vector &index) { std::ostringstream oss; oss << "Array '" << arrayInfo.varname; for (unsigned int i = 0; i < arrayInfo.num.size(); ++i) oss << "[" << arrayInfo.num[i] << "]"; oss << "' index "; if (index.size() == 1) oss << index[0]; else { oss << arrayInfo.varname; for (unsigned int i = 0; i < index.size(); ++i) oss << "[" << index[i] << "]"; } oss << " out of bounds"; reportError(tok, Severity::error, "arrayIndexOutOfBounds", oss.str().c_str()); } void CheckBufferOverrun::arrayIndexOutOfBounds(const std::list &callstack, const ArrayInfo &arrayInfo, const std::vector &index) { std::ostringstream oss; oss << "Array '" << arrayInfo.varname; for (unsigned int i = 0; i < arrayInfo.num.size(); ++i) oss << "[" << arrayInfo.num[i] << "]"; oss << "' index "; if (index.size() == 1) oss << index[0]; else { oss << arrayInfo.varname; for (unsigned int i = 0; i < index.size(); ++i) oss << "[" << index[i] << "]"; } oss << " out of bounds"; reportError(callstack, Severity::error, "arrayIndexOutOfBounds", oss.str().c_str()); } void CheckBufferOverrun::bufferOverrun(const Token *tok, const std::string &varnames) { std::string v = varnames; while (v.find(" ") != std::string::npos) v.erase(v.find(" "), 1); std::string errmsg("Buffer access out-of-bounds"); if (!v.empty()) errmsg += ": " + v; reportError(tok, Severity::error, "bufferAccessOutOfBounds", errmsg); } void CheckBufferOverrun::strncatUsage(const Token *tok) { if (_settings && !_settings->_checkCodingStyle) return; reportError(tok, Severity::warning, "strncatUsage", "Dangerous usage of strncat - 3rd parameter is the maximum number of characters to append.\n" "strncat appends at max its 3rd parameter's amount of characters. The safe way to use " "strncat is to calculate remaining space in the buffer and use it as 3rd parameter."); } void CheckBufferOverrun::outOfBounds(const Token *tok, const std::string &what) { reportError(tok, Severity::error, "outOfBounds", what + " is out of bounds"); } void CheckBufferOverrun::pointerOutOfBounds(const Token *tok, const std::string &object) { reportError(tok, Severity::portability, "pointerOutOfBounds", "Undefined behaviour: pointer arithmetic result does not point into or just past the end of the " + object + "\n" "Undefined behaviour: Using pointer arithmetic so that the result does not point into or just past the end of the same object. Further information: https://www.securecoding.cert.org/confluence/display/seccode/ARR30-C.+Do+not+form+or+use+out+of+bounds+pointers+or+array+subscripts"); } void CheckBufferOverrun::sizeArgumentAsChar(const Token *tok) { if (_settings && !_settings->_checkCodingStyle) return; reportError(tok, Severity::warning, "sizeArgumentAsChar", "The size argument is given as a char constant"); } void CheckBufferOverrun::terminateStrncpyError(const Token *tok) { reportError(tok, Severity::warning, "terminateStrncpy", "After a strncpy() the buffer should be zero-terminated"); } void CheckBufferOverrun::cmdLineArgsError(const Token *tok) { reportError(tok, Severity::error, "insecureCmdLineArgs", "Buffer overrun possible for long cmd-line args"); } //--------------------------------------------------------------------------- //--------------------------------------------------------------------------- // Check array usage.. //--------------------------------------------------------------------------- /** * @brief This is a helper class to be used with std::find_if */ class TokenStrEquals { public: /** * @param str Token::str() is compared against this. */ TokenStrEquals(const std::string &str) : value(str) { } /** * Called automatically by std::find_if * @param tok Token inside the list */ bool operator()(const Token *tok) const { return value == tok->str(); } private: TokenStrEquals& operator=(const TokenStrEquals&); // disallow assignments const std::string value; }; /** * bailout if variable is used inside if/else/switch block or if there is "break" * @param tok token for "if" or "switch" * @param varid variable id * @return is bailout recommended? */ static bool bailoutIfSwitch(const Token *tok, const unsigned int varid) { // Used later to check if the body belongs to a "if" const std::string str1(tok->str()); // Count { and } unsigned int indentlevel = 0; for (; tok; tok = tok->next()) { if (tok->str() == "{") indentlevel++; else if (tok->str() == "}") { // scan the else-block if (indentlevel == 1 && Token::simpleMatch(tok, "} else {")) { --indentlevel; continue; } else if (indentlevel <= 1) { break; } --indentlevel; } // If scanning a "if" block then bailout for "break" else if (str1 == "if" && tok->str() == "break") return true; // bailout for "return" else if (tok->str() == "return") return true; // bailout if varid is found else if (tok->varId() == varid) return true; } // No bailout stuff found => return false return false; } /** * Parse for loop initialization statement. Look for a counter variable * \param tok [in] first token inside the parentheses * \param varid [out] varid of counter variable * \param init_value [out] init value of counter variable * \return success => pointer to the for loop condition. fail => 0 */ static const Token *for_init(const Token *tok, unsigned int &varid, std::string &init_value) { if (Token::Match(tok, "%var% = %any% ;")) { if (tok->tokAt(2)->isNumber()) { init_value = tok->strAt(2); } varid = tok->varId(); tok = tok->tokAt(4); } else if (Token::Match(tok, "%type% %var% = %any% ;")) { if (tok->tokAt(3)->isNumber()) { init_value = tok->strAt(3); } varid = tok->next()->varId(); tok = tok->tokAt(5); } else if (Token::Match(tok, "%type% %type% %var% = %any% ;")) { if (tok->tokAt(4)->isNumber()) { init_value = tok->strAt(4); } varid = tok->tokAt(2)->varId(); tok = tok->tokAt(6); } else return 0; return tok; } /** Parse for condition */ static bool for_condition(const Token * const tok2, unsigned int varid, std::string &min_value, std::string &max_value, std::string &strindex, bool &maxMinFlipped) { if (Token::Match(tok2, "%varid% < %num% ;", varid) || Token::Match(tok2, "%varid% != %num% ; ++ %varid%", varid) || Token::Match(tok2, "%varid% != %num% ; %varid% ++", varid)) { maxMinFlipped = false; const MathLib::bigint value = MathLib::toLongNumber(tok2->strAt(2)); max_value = MathLib::toString(value - 1); } else if (Token::Match(tok2, "%varid% <= %num% ;", varid)) { maxMinFlipped = false; max_value = tok2->strAt(2); } else if (Token::Match(tok2, "%num% < %varid% ;", varid) || Token::Match(tok2, "%num% != %varid% ; ++ %varid%", varid) || Token::Match(tok2, "%num% != %varid% ; %varid% ++", varid)) { maxMinFlipped = true; const MathLib::bigint value = MathLib::toLongNumber(tok2->str()); max_value = min_value; min_value = MathLib::toString(value + 1); } else if (Token::Match(tok2, "%num% <= %varid% ;", varid)) { maxMinFlipped = true; max_value = min_value; min_value = tok2->str(); } else { return false; } strindex = tok2->isName() ? tok2->str() : tok2->strAt(2); return true; } /** * Parse the third sub-statement in for head * \param tok first token * \param varid variable id of counter * \param min_value min value of counter * \param max_value max value of counter * \param maxMinFlipped counting from max to min */ static bool for3(const Token * const tok, unsigned int varid, std::string &min_value, std::string &max_value, const bool maxMinFlipped) { assert(tok != 0); if (Token::Match(tok, "%varid% += %num% )", varid) || Token::Match(tok, "%varid% = %num% + %varid% )", varid)) { if (!MathLib::isInt(tok->strAt(2))) return false; const MathLib::bigint num = MathLib::toLongNumber(tok->strAt(2)); // We have for example code: "for(i=2;i<22;i+=6) // We can calculate that max value for i is 20, not 21 // 21-2 = 19 // 19/6 = 3 // 6*3+2 = 20 MathLib::bigint max = MathLib::toLongNumber(max_value); MathLib::bigint min = MathLib::toLongNumber(min_value); max = ((max - min) / num) * num + min; max_value = MathLib::toString(max); } else if (Token::Match(tok, "%varid% = %varid% + %num% )", varid)) { if (!MathLib::isInt(tok->strAt(4))) return false; const MathLib::bigint num = MathLib::toLongNumber(tok->strAt(4)); MathLib::bigint max = MathLib::toLongNumber(max_value); MathLib::bigint min = MathLib::toLongNumber(min_value); max = ((max - min) / num) * num + min; max_value = MathLib::toString(max); } else if (Token::Match(tok, "%varid% -= %num% )", varid) || Token::Match(tok, "%varid% = %num% - %varid% )", varid)) { if (!MathLib::isInt(tok->strAt(2))) return false; const MathLib::bigint num = MathLib::toLongNumber(tok->strAt(2)); MathLib::bigint max = MathLib::toLongNumber(max_value); MathLib::bigint min = MathLib::toLongNumber(min_value); max = ((max - min) / num) * num + min; max_value = MathLib::toString(max); } else if (Token::Match(tok, "%varid% = %varid% - %num% )", varid)) { if (!MathLib::isInt(tok->strAt(4))) return false; const MathLib::bigint num = MathLib::toLongNumber(tok->strAt(4)); MathLib::bigint max = MathLib::toLongNumber(max_value); MathLib::bigint min = MathLib::toLongNumber(min_value); max = ((max - min) / num) * num + min; max_value = MathLib::toString(max); } else if (Token::Match(tok, "--| %varid% --| )", varid)) { if (!maxMinFlipped && MathLib::toLongNumber(min_value) < MathLib::toLongNumber(max_value)) { // Code relies on the fact that integer will overflow: // for (unsigned int i = 3; i < 5; --i) // Set min value in this case to zero. max_value = min_value; min_value = "0"; } } else if (! Token::Match(tok, "++| %varid% ++| )", varid)) { return false; } return true; } /** * Check is the counter variable increased elsewhere inside the loop or used * for anything else except reading * \param tok1 first token of for-body * \param varid counter variable id * \return bailout needed => true */ static bool for_bailout(const Token * const tok1, unsigned int varid) { for (const Token *loopTok = tok1; loopTok && loopTok != tok1->link(); loopTok = loopTok->next()) { if (loopTok->varId() == varid) { // Counter variable used inside loop if (Token::Match(loopTok->next(), "+=|-=|++|--|=") || Token::Match(loopTok->previous(), "++|--")) { return true; } } } return false; } void CheckBufferOverrun::parse_for_body(const Token *tok2, const ArrayInfo &arrayInfo, const std::string &strindex, bool condition_out_of_bounds, unsigned int counter_varid, const std::string &min_counter_value, const std::string &max_counter_value) { const std::string pattern((arrayInfo.varid ? std::string("%varid%") : arrayInfo.varname) + " [ " + strindex + " ]"); // count { and } for tok2 int indentlevel2 = 0; for (; tok2; tok2 = tok2->next()) { if (tok2->str() == ";" && indentlevel2 == 0) break; if (tok2->str() == "{") ++indentlevel2; if (tok2->str() == "}") { --indentlevel2; if (indentlevel2 <= 0) break; } // TODO: try to reduce false negatives. This is just a quick fix // for TestBufferOverrun::array_index_for_question if (tok2->str() == "?") break; if (Token::Match(tok2, "if|switch")) { if (bailoutIfSwitch(tok2, arrayInfo.varid)) break; } if (condition_out_of_bounds && Token::Match(tok2, pattern.c_str(), arrayInfo.varid)) { bufferOverrun(tok2, arrayInfo.varname); break; } else if (arrayInfo.varid && counter_varid > 0 && !min_counter_value.empty() && !max_counter_value.empty()) { // Is the loop variable used to calculate the array index? // In this scope it is determined if such calculated // array indexes are out of bounds. // Only the minimum and maximum results of the calculation is // determined // Minimum calculated array index int min_index = 0; // Maximum calculated array index int max_index = 0; if (Token::Match(tok2, "%varid% [ %var% +|-|*|/ %num% ]", arrayInfo.varid) && tok2->tokAt(2)->varId() == counter_varid) { // operator: +-*/ const char action = tok2->strAt(3)[0]; // second operator const std::string &second(tok2->tokAt(4)->str()); //printf("min_index: %s %c %s\n", min_counter_value.c_str(), action, second.c_str()); //printf("max_index: %s %c %s\n", max_counter_value.c_str(), action, second.c_str()); min_index = std::atoi(MathLib::calculate(min_counter_value, second, action, _tokenizer).c_str()); max_index = std::atoi(MathLib::calculate(max_counter_value, second, action, _tokenizer).c_str()); } else if (Token::Match(tok2, "%varid% [ %num% +|-|*|/ %var% ]", arrayInfo.varid) && tok2->tokAt(4)->varId() == counter_varid) { // operator: +-*/ const char action = tok2->strAt(3)[0]; // first operand const std::string &first(tok2->tokAt(2)->str()); //printf("min_index: %s %c %s\n", first.c_str(), action, min_counter_value.c_str()); //printf("max_index: %s %c %s\n", first.c_str(), action, max_counter_value.c_str()); min_index = std::atoi(MathLib::calculate(first, min_counter_value, action, _tokenizer).c_str()); max_index = std::atoi(MathLib::calculate(first, max_counter_value, action, _tokenizer).c_str()); } //printf("min_index = %d, max_index = %d, size = %d\n", min_index, max_index, size); if (min_index < 0 || max_index < 0) { arrayIndexOutOfBounds(tok2, (int)arrayInfo.num[0], std::min(min_index, max_index)); } if (min_index >= (int)arrayInfo.num[0] || max_index >= (int)arrayInfo.num[0]) { arrayIndexOutOfBounds(tok2, (int)arrayInfo.num[0], std::max(min_index, max_index)); } } } } void CheckBufferOverrun::checkFunctionParameter(const Token &tok, unsigned int par, const ArrayInfo &arrayInfo) { // total_size : which parameter in function call takes the total size? std::map total_size; total_size["fgets"] = 2; // The second argument for fgets can't exceed the total size of the array total_size["memcmp"] = 3; total_size["memcpy"] = 3; total_size["memmove"] = 3; if (par == 1) { // reading from array // if it is zero terminated properly there won't be buffer overruns total_size["strncat"] = 3; total_size["strncpy"] = 3; total_size["memset"] = 3; total_size["fread"] = 1001; // parameter 2 * parameter 3 total_size["fwrite"] = 1001; // parameter 2 * parameter 3 } if (par == 2) { total_size["read"] = 3; total_size["pread"] = 3; total_size["write"] = 3; total_size["recv"] = 3; total_size["recvfrom"] = 3; total_size["send"] = 3; total_size["sendto"] = 3; } std::map::const_iterator it = total_size.find(tok.str()); if (it != total_size.end()) { if (arrayInfo.element_size == 0) return; // arg : the index of the "wanted" argument in the function call. unsigned int arg = it->second; // Parse function call. When a ',' is seen, arg is decremented. // if arg becomes 1 then the current function parameter is the wanted parameter. // if arg becomes 1000 then multiply current and next argument. for (const Token *tok2 = tok.tokAt(2); tok2; tok2 = tok2->next()) { if (tok2->str() == "(") { tok2 = tok2->link(); continue; } if (tok2->str() == ")") break; if (tok2->str() == ",") { --arg; if (arg == 1) { if (Token::Match(tok2, ", %num% ,|)")) { const MathLib::bigint sz = MathLib::toLongNumber(tok2->strAt(1)); MathLib::bigint elements = 1; for (unsigned int i = 0; i < arrayInfo.num.size(); ++i) elements *= arrayInfo.num[i]; if (sz < 0 || sz > int(elements * arrayInfo.element_size)) { bufferOverrun(&tok, arrayInfo.varname); } } else if (Token::Match(tok2, ", %any% ,|)") && tok2->next()->str()[0] == '\'') { sizeArgumentAsChar(tok2->next()); } break; } if (arg == 1000) // special code. This parameter multiplied with the next must not exceed total_size { if (Token::Match(tok2, ", %num% , %num% ,|)")) { const MathLib::bigint sz = MathLib::toLongNumber(MathLib::multiply(tok2->strAt(1), tok2->strAt(3))); MathLib::bigint elements = 1; for (unsigned int i = 0; i < arrayInfo.num.size(); ++i) elements *= arrayInfo.num[i]; if (sz < 0 || sz > int(elements * arrayInfo.element_size)) { bufferOverrun(&tok, arrayInfo.varname); } } break; } } } } // Calling a user function? // only 1-dimensional arrays can be checked currently else if (arrayInfo.num.size() == 1) { const Token *ftok = _tokenizer->getFunctionTokenByName(tok.str().c_str()); if (Token::Match(ftok, "%var% (") && Token::Match(ftok->next()->link(), ") const| {")) { // Get varid for the corresponding parameter.. unsigned int parameter = 1; unsigned int parameterVarId = 0; for (const Token *ftok2 = ftok->tokAt(2); ftok2; ftok2 = ftok2->next()) { if (ftok2->str() == ",") { if (parameter >= par) break; ++parameter; } else if (ftok2->str() == ")") break; else if (parameter == par && Token::Match(ftok2, "%var% ,|)")) parameterVarId = ftok2->varId(); } // No parameterVarId => bail out if (parameterVarId == 0) return; // Step into the function scope.. ftok = ftok->next()->link(); if (!Token::Match(ftok, ") const| {")) return; ftok = Token::findmatch(ftok, "{"); ftok = ftok->next(); // Check the parameter usage in the function scope.. for (; ftok; ftok = ftok->next()) { if (Token::Match(ftok, "if|for|while (")) { // bailout if there is buffer usage.. if (bailoutIfSwitch(ftok, parameterVarId)) { break; } // no bailout is needed. skip the if-block else { // goto end of if block.. ftok = ftok->next()->link()->next()->link(); if (Token::simpleMatch(ftok, "} else {")) ftok = ftok->tokAt(2)->link(); continue; } } if (ftok->str() == "}") break; if (ftok->varId() == parameterVarId) { if (Token::Match(ftok->previous(), "-- %var%") || Token::Match(ftok, "%var% --")) break; if (Token::Match(ftok->previous(), "[=+-*/;{}] %var% [ %num% ]")) { const MathLib::bigint index = MathLib::toLongNumber(ftok->strAt(2)); if (index >= 0 && arrayInfo.num[0] > 0 && index >= arrayInfo.num[0]) { std::list callstack; callstack.push_back(&tok); callstack.push_back(ftok); std::vector indexes; indexes.push_back(index); arrayIndexOutOfBounds(callstack, arrayInfo, indexes); } } } } } } } void CheckBufferOverrun::checkFunctionCall(const Token *tok, const ArrayInfo &arrayInfo) { // 1st parameter.. if (Token::Match(tok->tokAt(2), "%varid% ,|)", arrayInfo.varid)) checkFunctionParameter(*tok, 1, arrayInfo); else if (Token::Match(tok->tokAt(2), "%varid% + %num% ,|)", arrayInfo.varid)) { const ArrayInfo ai(arrayInfo.limit(MathLib::toLongNumber(tok->strAt(4)))); checkFunctionParameter(*tok, 1, ai); } // goto 2nd parameter and check it.. for (const Token *tok2 = tok->tokAt(2); tok2; tok2 = tok2->next()) { if (tok2->str() == "(") { tok2 = tok2->link(); continue; } if (tok2->str() == ";" || tok2->str() == ")") break; if (tok2->str() == ",") { if (Token::Match(tok2, ", %varid% ,|)", arrayInfo.varid)) checkFunctionParameter(*tok, 2, arrayInfo); else if (Token::Match(tok2, ", %varid% + %num% ,|)", arrayInfo.varid)) { const ArrayInfo ai(arrayInfo.limit(MathLib::toLongNumber(tok2->strAt(3)))); checkFunctionParameter(*tok, 2, ai); } break; } } } void CheckBufferOverrun::checkScopeForBody(const Token *tok, const ArrayInfo &arrayInfo, bool &bailout) { bailout = false; const Token *tok2 = tok->tokAt(2); const MathLib::bigint size = arrayInfo.num[0]; // Check if there is a break in the body.. { const Token *bodyStart = tok->next()->link()->next(); const Token *bodyEnd = bodyStart->link(); if (Token::findmatch(bodyStart, "break ;", bodyEnd)) return; } unsigned int counter_varid = 0; std::string min_counter_value; std::string max_counter_value; tok2 = for_init(tok2, counter_varid, min_counter_value); if (tok2 == 0 || counter_varid == 0) return; bool maxMinFlipped = false; std::string strindex; if (!for_condition(tok2, counter_varid, min_counter_value, max_counter_value, strindex, maxMinFlipped)) return; // Get index variable and stopsize. bool condition_out_of_bounds = true; if (MathLib::toLongNumber(max_counter_value) < size) condition_out_of_bounds = false; if (!for3(tok2->tokAt(4), counter_varid, min_counter_value, max_counter_value, maxMinFlipped)) return; if (Token::Match(tok2->tokAt(4), "%var% =|+=|-=") && MathLib::toLongNumber(max_counter_value) <= size) condition_out_of_bounds = false; // Goto the end parenthesis of the for-statement: "for (x; y; z)" .. tok2 = tok->next()->link(); if (!tok2 || !tok2->tokAt(5)) { bailout = true; return; } // Check is the counter variable increased elsewhere inside the loop or used // for anything else except reading if (for_bailout(tok2->next(), counter_varid)) { bailout = true; return; } parse_for_body(tok2->next(), arrayInfo, strindex, condition_out_of_bounds, counter_varid, min_counter_value, max_counter_value); } void CheckBufferOverrun::checkScope(const Token *tok, const std::vector &varname, const MathLib::bigint size, const MathLib::bigint total_size, unsigned int varid) { std::string varnames; for (unsigned int i = 0; i < varname.size(); ++i) varnames += (i == 0 ? "" : " . ") + varname[i]; const unsigned char varc(static_cast(varname.empty() ? 0U : (varname.size() - 1) * 2U)); if (Token::simpleMatch(tok, "return")) { tok = tok->next(); if (!tok) return; } // Array index.. if (varid > 0) { if (Token::Match(tok, "%varid% [ %num% ]", varid)) { const MathLib::bigint index = MathLib::toLongNumber(tok->strAt(2)); if (index >= size) { arrayIndexOutOfBounds(tok, size, index); } } } else if (Token::Match(tok, (varnames + " [ %num% ]").c_str())) { const MathLib::bigint index = MathLib::toLongNumber(tok->strAt(2 + varc)); if (index >= size) { arrayIndexOutOfBounds(tok->tokAt(varc), size, index); } } // If the result of pointer arithmetic means that the pointer is // out of bounds then this flag will be set. bool pointerIsOutOfBounds = false; // Count { and } for tok int indentlevel = 0; for (; tok; tok = tok->next()) { if (tok->str() == "{") { ++indentlevel; } else if (tok->str() == "}") { --indentlevel; if (indentlevel < 0) return; } if (varid != 0 && Token::Match(tok, "%varid% = new|malloc|realloc", varid)) { // Abort break; } // Array index.. if (varid > 0) { if (!tok->isName() && !Token::Match(tok, "[.&]") && Token::Match(tok->next(), "%varid% [ %num% ]", varid)) { const MathLib::bigint index = MathLib::toLongNumber(tok->strAt(3)); if (index < 0 || index >= size) { if (index > size || !Token::simpleMatch(tok->previous(), "& (")) { arrayIndexOutOfBounds(tok->next(), size, index); } } } if (Token::Match(tok, "return %varid% [ %num% ]", varid)) { const MathLib::bigint index = MathLib::toLongNumber(tok->strAt(3)); if (index < 0 || index >= size) { arrayIndexOutOfBounds(tok->next(), size, index); } } } else if (!tok->isName() && !Token::Match(tok, "[.&]") && Token::Match(tok->next(), (varnames + " [ %num% ]").c_str())) { const MathLib::bigint index = MathLib::toLongNumber(tok->strAt(3 + varc)); if (index >= size) { arrayIndexOutOfBounds(tok->tokAt(1 + varc), size, index); } tok = tok->tokAt(4); continue; } // memset, memcmp, memcpy, strncpy, fgets.. if (varid == 0 && size > 0) { ArrayInfo arrayInfo(0U, varnames, (unsigned int)(total_size / size), (unsigned int)size); if (Token::Match(tok, ("%var% ( " + varnames + " ,").c_str())) checkFunctionParameter(*tok, 1, arrayInfo); if (Token::Match(tok, ("%var% ( %var% , " + varnames + " ,").c_str())) checkFunctionParameter(*tok, 2, arrayInfo); } // Loop.. if (Token::simpleMatch(tok, "for (")) { const ArrayInfo arrayInfo(varid, varnames, (unsigned int)size, (unsigned int)total_size); bool bailout = false; checkScopeForBody(tok, arrayInfo, bailout); if (bailout) break; continue; } // Writing data into array.. if ((varid > 0 && Token::Match(tok, "strcpy|strcat ( %varid% , %str% )", varid)) || (varid == 0 && Token::Match(tok, ("strcpy|strcat ( " + varnames + " , %str% )").c_str()))) { const std::size_t len = Token::getStrLength(tok->tokAt(varc + 4)); if (total_size > 0 && len >= (unsigned int)total_size) { bufferOverrun(tok, varid > 0 ? "" : varnames.c_str()); continue; } } // Detect few strcat() calls const std::string strcatPattern = varid > 0 ? std::string("strcat ( %varid% , %str% ) ;") : ("strcat ( " + varnames + " , %str% ) ;"); if (Token::Match(tok, strcatPattern.c_str(), varid)) { size_t charactersAppend = 0; const Token *tok2 = tok; while (tok2 && Token::Match(tok2, strcatPattern.c_str(), varid)) { charactersAppend += Token::getStrLength(tok2->tokAt(4 + varc)); if (charactersAppend >= static_cast(total_size)) { bufferOverrun(tok2); break; } tok2 = tok2->tokAt(7 + varc); } } // sprintf.. // TODO: change total_size to an unsigned value and remove the "&& total_size > 0" check. const std::string sprintfPattern = varid > 0 ? std::string("sprintf ( %varid% , %str% [,)]") : ("sprintf ( " + varnames + " , %str% [,)]"); if (Token::Match(tok, sprintfPattern.c_str(), varid) && total_size > 0) { checkSprintfCall(tok, static_cast(total_size)); } // snprintf.. const std::string snprintfPattern = varid > 0 ? std::string("snprintf ( %varid% , %num% ,") : ("snprintf ( " + varnames + " , %num% ,"); if (Token::Match(tok, snprintfPattern.c_str(), varid)) { const MathLib::bigint n = MathLib::toLongNumber(tok->strAt(4 + varc)); if (n > total_size) outOfBounds(tok->tokAt(4 + varc), "snprintf size"); } // Check function call.. if (Token::Match(tok, "%var% (")) { // No varid => function calls are not handled if (varid == 0) continue; const ArrayInfo arrayInfo(varid, varnames, size, total_size / size); checkFunctionCall(tok, arrayInfo); } // undefined behaviour: result of pointer arithmetic is out of bounds if (varid && Token::Match(tok, "= %varid% + %num% ;", varid)) { const MathLib::bigint index = MathLib::toLongNumber(tok->strAt(3)); if (index > size && _settings->_checkCodingStyle) pointerOutOfBounds(tok->next(), "buffer"); if (index >= size && Token::Match(tok->tokAt(-2), "[;{}] %varid% =", varid)) pointerIsOutOfBounds = true; } if (pointerIsOutOfBounds && Token::Match(tok, "[;{}=] * %varid% [;=]", varid)) { outOfBounds(tok->tokAt(2), tok->strAt(2)); } } } void CheckBufferOverrun::checkScope(const Token *tok, const ArrayInfo &arrayInfo) { const MathLib::bigint total_size = arrayInfo.num[0] * arrayInfo.element_size; // Count { and } for tok unsigned int indentlevel = 0; for (; tok; tok = tok->next()) { if (tok->str() == "{") { ++indentlevel; } else if (tok->str() == "}") { if (indentlevel == 0) return; --indentlevel; } else if (Token::Match(tok, "%varid% [ %num% ]", arrayInfo.varid)) { std::vector indexes; for (const Token *tok2 = tok->next(); Token::Match(tok2, "[ %num% ]"); tok2 = tok2->tokAt(3)) { const MathLib::bigint index = MathLib::toLongNumber(tok2->strAt(1)); if (index < 0) { indexes.clear(); break; } indexes.push_back(index); } if (indexes.size() == arrayInfo.num.size()) { // Check if the indexes point outside the whole array.. // char a[10][10]; // a[0][20] <-- ok. // a[9][20] <-- error. // total number of elements of array.. MathLib::bigint totalElements = 1; // total index.. MathLib::bigint totalIndex = 0; // calculate the totalElements and totalIndex.. for (unsigned int i = 0; i < indexes.size(); ++i) { std::size_t ri = indexes.size() - 1 - i; totalIndex += indexes[ri] * totalElements; totalElements *= arrayInfo.num[ri]; } // just taking the address? const bool addr(Token::Match(tok->previous(), "[.&]") || Token::simpleMatch(tok->tokAt(-2), "& (")); // Is totalIndex in bounds? if (totalIndex > totalElements || (!addr && totalIndex == totalElements)) { arrayIndexOutOfBounds(tok, arrayInfo, indexes); } } } // Loop.. else if (Token::simpleMatch(tok, "for (")) { bool bailout = false; checkScopeForBody(tok, arrayInfo, bailout); if (bailout) break; continue; } // Check function call.. if (Token::Match(tok, "%var% (")) { checkFunctionCall(tok, arrayInfo); } if (_settings->_checkCodingStyle) { // check for strncpy which is not terminated if ((Token::Match(tok, "strncpy ( %varid% , %var% , %num% )", arrayInfo.varid))) { // strncpy takes entire variable length as input size if ((unsigned int)MathLib::toLongNumber(tok->strAt(6)) >= total_size) { const Token *tok2 = tok->next()->link()->next(); for (; tok2; tok2 = tok2->next()) { if (tok2->varId() == tok->tokAt(2)->varId()) { if (!Token::Match(tok2, "%varid% [ %any% ] = 0 ;", tok->tokAt(2)->varId())) { // this is currently inconclusive. See TestBufferOverrun::terminateStrncpy3 if (_settings->inconclusive) terminateStrncpyError(tok); } break; } } } } } // Dangerous usage of strncat.. if (Token::Match(tok, "strncpy|strncat ( %varid% , %any% , %num% )", arrayInfo.varid)) { if (tok->str() == "strncat") { const MathLib::bigint n = MathLib::toLongNumber(tok->strAt(6)); if (n >= total_size) strncatUsage(tok); } // Dangerous usage of strncpy + strncat.. if (Token::Match(tok->tokAt(8), "; strncat ( %varid% , %any% , %num% )", arrayInfo.varid)) { const MathLib::bigint n = MathLib::toLongNumber(tok->strAt(6)) + MathLib::toLongNumber(tok->strAt(15)); if (n > total_size) strncatUsage(tok->tokAt(9)); } } // Writing data into array.. if (Token::Match(tok, "strcpy|strcat ( %varid% , %str% )", arrayInfo.varid)) { const std::size_t len = Token::getStrLength(tok->tokAt(4)); if (total_size > 0 && len >= (unsigned int)total_size) { bufferOverrun(tok, arrayInfo.varname); continue; } } // Detect few strcat() calls if (total_size > 0 && Token::Match(tok, "strcat ( %varid% , %str% ) ;", arrayInfo.varid)) { std::size_t charactersAppend = 0; const Token *tok2 = tok; while (tok2 && Token::Match(tok2, "strcat ( %varid% , %str% ) ;", arrayInfo.varid)) { charactersAppend += Token::getStrLength(tok2->tokAt(4)); if (charactersAppend >= (unsigned int)total_size) { bufferOverrun(tok2, arrayInfo.varname); break; } tok2 = tok2->tokAt(7); } } if (Token::Match(tok, "sprintf ( %varid% , %str% [,)]", arrayInfo.varid)) { checkSprintfCall(tok, total_size); } // snprintf.. if (total_size > 0 && Token::Match(tok, "snprintf ( %varid% , %num% ,", arrayInfo.varid)) { const MathLib::bigint n = MathLib::toLongNumber(tok->strAt(4)); if (n > total_size) outOfBounds(tok->tokAt(4), "snprintf size"); } // undefined behaviour: result of pointer arithmetic is out of bounds if (_settings->_checkCodingStyle && Token::Match(tok, "= %varid% + %num% ;", arrayInfo.varid)) { const MathLib::bigint index = MathLib::toLongNumber(tok->strAt(3)); if (index < 0 || index > arrayInfo.num[0]) { pointerOutOfBounds(tok->next(), "array"); } } } } //--------------------------------------------------------------------------- // Checking local variables in a scope //--------------------------------------------------------------------------- void CheckBufferOverrun::checkGlobalAndLocalVariable() { // Count { and } when parsing all tokens int indentlevel = 0; for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next()) { if (tok->str() == "{") ++indentlevel; else if (tok->str() == "}") --indentlevel; // size : Max array index MathLib::bigint size = 0; // type : The type of a array element std::string type; // varid : The variable id for the array unsigned int varid = 0; // nextTok : number of tokens used in variable declaration - used to skip to next statement. int nextTok = 0; // if the previous token exists, it must be either a variable name or "[;{}]" if (tok->previous() && (!tok->previous()->isName() && !Token::Match(tok->previous(), "[;{}]"))) continue; _errorLogger->reportProgress(_tokenizer->getFiles()->front(), "Check (BufferOverrun::checkGlobalAndLocalVariable)", tok->progressValue()); ArrayInfo arrayInfo; if (arrayInfo.declare(tok, *_tokenizer)) { while (tok && tok->str() != ";") tok = tok->next(); if (!tok) break; checkScope(tok, arrayInfo); continue; } if (Token::Match(tok, "%type% *| %var% [ %var% ] [;=]")) { // varpos : position for variable token unsigned char varpos = 1; if (tok->next()->str() == "*") ++varpos; // make sure the variable is defined if (tok->tokAt(varpos + 2)->varId() == 0) continue; // FIXME we loose the check for negative index when we bail // get maximum size from type // find where this token is defined const Token *index_type = Token::findmatch(_tokenizer->tokens(), "%varid%", tok->tokAt(varpos + 2)->varId()); index_type = index_type->previous(); if (index_type->str() == "char") { if (index_type->isUnsigned()) size = UCHAR_MAX + 1; else if (index_type->isSigned()) size = SCHAR_MAX + 1; else size = CHAR_MAX + 1; } else if (index_type->str() == "short") { if (index_type->isUnsigned()) size = USHRT_MAX + 1; else size = SHRT_MAX + 1; } // checkScope assumes size is signed int so we limit the following sizes to INT_MAX else if (index_type->str() == "int") { if (index_type->isUnsigned()) size = INT_MAX; // should be UINT_MAX + 1U; else size = INT_MAX; // should be INT_MAX + 1U; } else if (index_type->str() == "long") { if (index_type->isUnsigned()) { if (index_type->isLong()) size = INT_MAX; // should be ULLONG_MAX + 1ULL; else size = INT_MAX; // should be ULONG_MAX + 1UL; } else { if (index_type->isLong()) size = INT_MAX; // should be LLONG_MAX + 1LL; else size = INT_MAX; // should be LONG_MAX + 1L; } } type = tok->strAt(varpos - 1); varid = tok->tokAt(varpos)->varId(); nextTok = varpos + 5; } else if (indentlevel > 0 && Token::Match(tok, "[*;{}] %var% = new %type% [ %num% ]")) { size = MathLib::toLongNumber(tok->strAt(6)); type = tok->strAt(4); varid = tok->tokAt(1)->varId(); nextTok = 8; } else if (indentlevel > 0 && Token::Match(tok, "[*;{}] %var% = new %type% ( %num% )")) { size = 1; type = tok->strAt(4); varid = tok->tokAt(1)->varId(); nextTok = 8; } else if (indentlevel > 0 && Token::Match(tok, "[;{}] %var% = %str% ;") && tok->next()->varId() > 0 && NULL != Token::findmatch(_tokenizer->tokens(), "[;{}] const| %type% * %varid% ;", tok->next()->varId())) { size = 1 + int(tok->tokAt(3)->strValue().size()); type = "char"; varid = tok->next()->varId(); nextTok = 4; } else if (indentlevel > 0 && Token::Match(tok, "[*;{}] %var% = malloc ( %num% ) ;")) { size = MathLib::toLongNumber(tok->strAt(5)); type = "char"; // minimum type, typesize=1 varid = tok->tokAt(1)->varId(); nextTok = 7; if (varid > 0) { // get type of variable const Token *declTok = Token::findmatch(_tokenizer->tokens(), "[;{}] %type% * %varid% ;", varid); if (!declTok) continue; type = declTok->next()->str(); // malloc() gets count of bytes and not count of // elements, so we should calculate count of elements // manually unsigned int sizeOfType = _tokenizer->sizeOfType(declTok->next()); if (sizeOfType > 0) size /= static_cast(sizeOfType); } } else { continue; } if (varid == 0) continue; Token sizeTok(0); sizeTok.str(type); const MathLib::bigint total_size = size * static_cast(_tokenizer->sizeOfType(&sizeTok)); if (total_size == 0) continue; std::vector v; checkScope(tok->tokAt(nextTok), v, size, total_size, varid); } } //--------------------------------------------------------------------------- //--------------------------------------------------------------------------- // Checking member variables of structs.. //--------------------------------------------------------------------------- void CheckBufferOverrun::checkStructVariable() { for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next()) { if (tok->str() == "{") { tok = tok->link(); } if (!Token::Match(tok, "struct|class %var% {|:")) continue; const std::string &structname = tok->next()->str(); const Token *tok2 = tok; while (tok2->str() != "{") tok2 = tok2->next(); // Found a struct declaration. Search for arrays.. for (; tok2; tok2 = tok2->next()) { // skip inner scopes.. if (tok2->next() && tok2->next()->str() == "{") { tok2 = tok2->next()->link(); continue; } if (tok2->str() == "}") break; ArrayInfo arrayInfo; if (!arrayInfo.declare(tok2->next(), *_tokenizer)) continue; // Only handling 1-dimensional arrays yet.. if (arrayInfo.num.size() > 1) continue; // Skip array with only 0/1 elements because those are // often overrun intentionally if (arrayInfo.num[0] <= 1) continue; std::vector varname; varname.push_back(""); varname.push_back(arrayInfo.varname); // Class member variable => Check functions if (tok->str() == "class") { std::string func_pattern(structname + " :: %var% ("); const Token *tok3 = Token::findmatch(_tokenizer->tokens(), func_pattern.c_str()); while (tok3) { for (const Token *tok4 = tok3; tok4; tok4 = tok4->next()) { if (Token::Match(tok4, "[;{}]")) break; if (Token::simpleMatch(tok4, ") {")) { std::vector v; checkScope(tok4->tokAt(2), v, static_cast(arrayInfo.num[0]), static_cast(arrayInfo.num[0] * arrayInfo.element_size), arrayInfo.varid); break; } } tok3 = Token::findmatch(tok3->next(), func_pattern.c_str()); } } for (const Token *tok3 = _tokenizer->tokens(); tok3; tok3 = tok3->next()) { if (tok3->str() != structname) continue; // Declare variable: Fred fred1; if (Token::Match(tok3->next(), "%var% ;")) varname[0] = tok3->strAt(1); // Declare pointer: Fred *fred1 else if (Token::Match(tok3->next(), "* %var% [,);=]")) varname[0] = tok3->strAt(2); else continue; // Goto end of statement. const Token *CheckTok = NULL; while (tok3) { // End of statement. if (tok3->str() == ";") { CheckTok = tok3; break; } // End of function declaration.. if (Token::simpleMatch(tok3, ") ;")) break; // Function implementation.. if (Token::simpleMatch(tok3, ") {")) { CheckTok = tok3->tokAt(2); break; } tok3 = tok3->next(); } if (!tok3) break; if (!CheckTok) continue; // Check variable usage.. checkScope(CheckTok, varname, static_cast(arrayInfo.num[0]), static_cast(arrayInfo.num[0] * arrayInfo.element_size), 0); } } } } //--------------------------------------------------------------------------- void CheckBufferOverrun::bufferOverrun() { checkGlobalAndLocalVariable(); checkStructVariable(); checkBufferAllocatedWithStrlen(); checkInsecureCmdLineArgs(); } //--------------------------------------------------------------------------- MathLib::bigint CheckBufferOverrun::countSprintfLength(const std::string &input_string, const std::list ¶meters) { bool percentCharFound = false; std::size_t input_string_size = 1; bool handleNextParameter = false; std::string digits_string = ""; bool i_d_x_f_found = false; std::list::const_iterator paramIter = parameters.begin(); std::size_t parameterLength = 0; for (std::string::size_type i = 0; i < input_string.length(); ++i) { if (input_string[i] == '\\') { if (input_string[i+1] == '0') break; ++input_string_size; ++i; continue; } if (percentCharFound) { switch (input_string[i]) { case 'f': case 'x': case 'X': case 'i': i_d_x_f_found = true; case 'c': case 'e': case 'E': case 'g': case 'o': case 'u': case 'p': case 'n': handleNextParameter = true; break; case 'd': i_d_x_f_found = true; if (paramIter != parameters.end() && *paramIter && (*paramIter)->str()[0] != '"') parameterLength = (*paramIter)->str().length(); handleNextParameter = true; break; case 's': if (paramIter != parameters.end() && *paramIter && (*paramIter)->str()[0] == '"') parameterLength = Token::getStrLength(*paramIter); handleNextParameter = true; break; } } if (input_string[i] == '%') percentCharFound = !percentCharFound; else if (percentCharFound) { digits_string.append(1, input_string[i]); } if (!percentCharFound) input_string_size++; if (handleNextParameter) { unsigned int tempDigits = static_cast(std::abs(std::atoi(digits_string.c_str()))); if (i_d_x_f_found) tempDigits = std::max(static_cast(tempDigits), 1U); if (digits_string.find('.') != std::string::npos) { const std::string endStr = digits_string.substr(digits_string.find('.') + 1); unsigned int maxLen = std::max(static_cast(std::abs(std::atoi(endStr.c_str()))), 1U); if (input_string[i] == 's') { // For strings, the length after the dot "%.2s" will limit // the length of the string. if (parameterLength > maxLen) parameterLength = maxLen; } else { // For integers, the length after the dot "%.2d" can // increase required length if (tempDigits < maxLen) tempDigits = maxLen; } } if (tempDigits < parameterLength) input_string_size += parameterLength; else input_string_size += tempDigits; parameterLength = 0; digits_string = ""; i_d_x_f_found = false; percentCharFound = false; handleNextParameter = false; if (paramIter != parameters.end()) ++paramIter; } } return (MathLib::bigint)input_string_size; } void CheckBufferOverrun::checkSprintfCall(const Token *tok, const MathLib::bigint size) { if (size == 0) return; const Token *end = tok->next()->link(); // Count the number of tokens in the buffer variable's name int varc = 0; for (const Token *tok1 = tok->tokAt(3); tok1 != end; tok1 = tok1->next()) { if (tok1->str() == ",") break; ++ varc; } std::list parameters; if (tok->tokAt(5 + varc)->str() == ",") { for (const Token *tok2 = tok->tokAt(5 + varc); tok2 && tok2 != end; tok2 = tok2->next()) { if (Token::Match(tok2, ", %any% [,)]")) { if (Token::Match(tok2->next(), "%str%")) parameters.push_back(tok2->next()); else if (Token::Match(tok2->next(), "%num%")) parameters.push_back(tok2->next()); else parameters.push_back(0); } else { // Parameter is more complex, than just a value or variable. Ignore it for now // and skip to next token. parameters.push_back(0); // count parantheses for tok3 int ind = 0; for (const Token *tok3 = tok2->next(); tok3; tok3 = tok3->next()) { if (tok3->str() == "(") ++ind; else if (tok3->str() == ")") { --ind; if (ind < 0) break; } else if (ind == 0 && tok3->str() == ",") { tok2 = tok3->previous(); break; } } if (ind < 0) break; } } } MathLib::bigint len = countSprintfLength(tok->tokAt(4 + varc)->strValue(), parameters); if (len > size) { bufferOverrun(tok); } } //--------------------------------------------------------------------------- // Checking for allocating insufficient memory for copying a string by // allocating only strlen(src) bytes instead of strlen(src) + 1 bytes (one // extra for the terminating null character). // Example: // char *b = malloc(strlen(a)); // Should be malloc(strlen(a) + 1); // strcpy(b, a); // <== Buffer overrun //--------------------------------------------------------------------------- void CheckBufferOverrun::checkBufferAllocatedWithStrlen() { const char pattern[] = "%var% = new|malloc|g_malloc|g_try_malloc|realloc|g_realloc|g_try_realloc"; for (const Token *tok = Token::findmatch(_tokenizer->tokens(), pattern); tok; tok = Token::findmatch(tok->next(),pattern)) { unsigned int dstVarId; unsigned int srcVarId; // Look for allocation of a buffer based on the size of a string if (Token::Match(tok, "%var% = malloc|g_malloc|g_try_malloc ( strlen ( %var% ) )")) { dstVarId = tok->varId(); srcVarId = tok->tokAt(6)->varId(); tok = tok->tokAt(8); } else if (Token::Match(tok, "%var% = new char [ strlen ( %var% ) ]")) { dstVarId = tok->varId(); srcVarId = tok->tokAt(7)->varId(); tok = tok->tokAt(9); } else if (Token::Match(tok, "%var% = realloc|g_realloc|g_try_realloc ( %var% , strlen ( %var% ) )")) { dstVarId = tok->varId(); srcVarId = tok->tokAt(8)->varId(); tok = tok->tokAt(10); } else continue; // count { and } for tok int indentlevel = 0; for (; tok && tok->next(); tok = tok->next()) { // To avoid false positives and added complexity, we will only look for // improper usage of the buffer within the block that it was allocated if (tok->str() == "{") { ++indentlevel; } else if (tok->str() == "}") { --indentlevel; if (indentlevel < 0) return; } // If the buffers are modified, we can't be sure of their sizes if (tok->varId() == srcVarId || tok->varId() == dstVarId) break; if (Token::Match(tok, "strcpy ( %varid% , %var% )", dstVarId) && tok->tokAt(4)->varId() == srcVarId) { bufferOverrun(tok); } else if (Token::Match(tok, "sprintf ( %varid% , %str% , %var% )", dstVarId) && tok->tokAt(6)->varId() == srcVarId && tok->tokAt(4)->str().find("%s") != std::string::npos) { bufferOverrun(tok); } } } } //--------------------------------------------------------------------------- // Checking for buffer overflow caused by copying command line arguments // into fixed-sized buffers without checking to make sure that the command // line arguments will not overflow the buffer. // // int main(int argc, char* argv[]) // { // char prog[10]; // strcpy(prog, argv[0]); <-- Possible buffer overrun // } //--------------------------------------------------------------------------- void CheckBufferOverrun::checkInsecureCmdLineArgs() { const char pattern[] = "main ( int %var% , char *"; for (const Token *tok = Token::findmatch(_tokenizer->tokens(), pattern); tok; tok = Token::findmatch(tok->next(),pattern)) { // Get the name of the argv variable unsigned int varid = 0; if (Token::Match(tok, "main ( int %var% , char * %var% [ ] ,|)")) { varid = tok->tokAt(7)->varId(); } else if (Token::Match(tok, "main ( int %var% , char * * %var% ,|)")) { varid = tok->tokAt(8)->varId(); } if (varid == 0) continue; // Jump to the opening curly brace tok = tok->next()->link(); if (!Token::simpleMatch(tok, ") {")) continue; tok = tok->next(); // Search within main() for possible buffer overruns involving argv int indentlevel = -1; for (; tok; tok = tok->next()) { if (tok->str() == "{") { ++indentlevel; } else if (tok->str() == "}") { --indentlevel; if (indentlevel < 0) return; } // If argv is modified or tested, its size may be being limited properly if (tok->varId() == varid) break; // Match common patterns that can result in a buffer overrun // e.g. strcpy(buffer, argv[0]) if (Token::Match(tok, "strcpy|strcat ( %var% , * %varid%", varid) || Token::Match(tok, "strcpy|strcat ( %var% , %varid% [", varid)) { cmdLineArgsError(tok); } else if (Token::Match(tok, "sprintf ( %var% , %str% , %varid% [", varid) && tok->tokAt(4)->str().find("%s") != std::string::npos) { cmdLineArgsError(tok); } else if (Token::Match(tok, "sprintf ( %var% , %str% , * %varid%", varid) && tok->tokAt(4)->str().find("%s") != std::string::npos) { cmdLineArgsError(tok); } } } } //--------------------------------------------------------------------------- void CheckBufferOverrun::negativeIndexError(const Token *tok, MathLib::bigint index) { std::ostringstream ostr; ostr << "Array index " << index << " is out of bounds"; reportError(tok, Severity::error, "negativeIndex", ostr.str()); } void CheckBufferOverrun::negativeIndex() { const char pattern[] = "[ %num% ]"; for (const Token *tok = Token::findmatch(_tokenizer->tokens(), pattern); tok; tok = Token::findmatch(tok->next(),pattern)) { const MathLib::bigint index = MathLib::toLongNumber(tok->next()->str()); if (index < 0) { // Negative index. Check if it's an array. const Token *tok2 = tok; while (Token::simpleMatch(tok2->previous(), "]")) tok2 = tok2->previous()->link(); if (tok2->previous() && tok2->previous()->varId()) { const Token *tok3 = Token::findmatch(_tokenizer->tokens(), "%varid%", tok2->previous()->varId()); if (tok3 && Token::Match(tok3->next(), "[ %any% ] ;|[")) negativeIndexError(tok, index); } } } } #include "executionpath.h" /// @addtogroup Checks /// @{ CheckBufferOverrun::ArrayInfo::ArrayInfo() : num(_num), element_size(_element_size), varid(_varid), varname(_varname) { _element_size = 0; _varid = 0; } CheckBufferOverrun::ArrayInfo::ArrayInfo(const CheckBufferOverrun::ArrayInfo &ai) : num(_num), element_size(_element_size), varid(_varid), varname(_varname) { *this = ai; } CheckBufferOverrun::ArrayInfo & CheckBufferOverrun::ArrayInfo::operator=(const CheckBufferOverrun::ArrayInfo &ai) { if (&ai != this) { _element_size = ai.element_size; _num = ai.num; _varid = ai.varid; _varname = ai.varname; } return *this; } /** * Create array info with specified data * The intention is that this is only a temporary solution.. all * checking should be based on ArrayInfo from the start and then * this will not be needed as the declare can be used instead. */ CheckBufferOverrun::ArrayInfo::ArrayInfo(unsigned int id, const std::string &name, MathLib::bigint size1, MathLib::bigint n) : num(_num), element_size(_element_size), varid(_varid), varname(_varname) { _element_size = size1; _num.push_back(n); _varid = id; _varname = name; } CheckBufferOverrun::ArrayInfo CheckBufferOverrun::ArrayInfo::limit(MathLib::bigint value) const { MathLib::bigint uvalue = std::max(MathLib::bigint(0), value); MathLib::bigint n = 1; for (unsigned int i = 0; i < num.size(); ++i) n *= num[i]; if (uvalue > n) n = uvalue; return ArrayInfo(varid, varname, element_size, n - uvalue); } bool CheckBufferOverrun::ArrayInfo::declare(const Token *tok, const Tokenizer &tokenizer) { _num.clear(); _element_size = 0; _varname.clear(); if (!tok->isName() || tok->str() == "return") return false; while (tok && (tok->str() == "static" || tok->str() == "const" || tok->str() == "extern")) tok = tok->next(); // ivar : number of type tokens int ivar = 0; if (Token::Match(tok, "%type% *| %var% [")) ivar = 1; else if (Token::Match(tok, "%type% %type% *| %var% [")) ivar = 2; else return false; if (tok->str().find(":") != std::string::npos) return false; // Goto variable name token, get element size.. const Token *vartok = tok->tokAt(ivar); if (vartok->str() == "*") { _element_size = tokenizer.sizeOfType(vartok); vartok = vartok->next(); } else if (tok->str() == "struct") { _element_size = 100; } else { _element_size = tokenizer.sizeOfType(tok); } _varname = vartok->str(); _varid = vartok->varId(); if (!varid) return false; const Token *atok = vartok->tokAt(2); if (!Token::Match(atok, "%num% ] ;|=|[")) return false; while (Token::Match(atok, "%num% ] ;|=|[")) { _num.push_back(MathLib::toLongNumber(atok->str())); atok = atok->next(); if (Token::simpleMatch(atok, "] [")) atok = atok->tokAt(2); } return (!_num.empty() && Token::Match(atok, "] ;|=")); } /** * @brief %Check for buffer overruns (using ExecutionPath) */ class ExecutionPathBufferOverrun : public ExecutionPath { public: /** Startup constructor */ ExecutionPathBufferOverrun(Check *c, const std::map &arrayinfo) : ExecutionPath(c, 0), arrayInfo(arrayinfo), value(0) { } private: /** @brief Copy this check. Called from the ExecutionPath baseclass. */ ExecutionPath *copy() { return new ExecutionPathBufferOverrun(*this); } /** @brief is other execution path equal? */ bool is_equal(const ExecutionPath *e) const { const ExecutionPathBufferOverrun *c = static_cast(e); return (value == c->value); } /** @brief Buffer information */ const std::map &arrayInfo; /** no implementation => compiler error if used by accident */ void operator=(const ExecutionPathBufferOverrun &); /** internal constructor for creating extra checks */ ExecutionPathBufferOverrun(Check *c, const std::map &arrayinfo, unsigned int varid_) : ExecutionPath(c, varid_), arrayInfo(arrayinfo) { // Pretend that variables are initialized to 0 // This checking is not about uninitialized variables value = 0; } /** @brief Variable value. */ MathLib::bigint value; /** * @brief Assign value to a variable * @param checks the execution paths * @param varid the variable id * @param value the assigned value */ static void assign_value(std::list &checks, unsigned int varid, const std::string &value) { if (varid == 0) return; std::list::const_iterator it; for (it = checks.begin(); it != checks.end(); ++it) { ExecutionPathBufferOverrun *c = dynamic_cast(*it); if (c && c->varId == varid) c->value = MathLib::toLongNumber(value); } } /** * @brief Found array usage, analyse the array usage * @param tok token where usage occurs (only used when reporting the error) * @param checks The execution paths * @param varid1 variable id for the array * @param varid2 variable id for the index */ static void array_index(const Token *tok, std::list &checks, unsigned int varid1, unsigned int varid2) { if (checks.empty() || varid1 == 0 || varid2 == 0) return; // Locate array info corresponding to varid1 CheckBufferOverrun::ArrayInfo ai; { ExecutionPathBufferOverrun *c = dynamic_cast(checks.front()); std::map::const_iterator it; it = c->arrayInfo.find(varid1); if (it == c->arrayInfo.end()) return; ai = it->second; } // Check if varid2 variable has a value that is out-of-bounds std::list::const_iterator it; for (it = checks.begin(); it != checks.end(); ++it) { ExecutionPathBufferOverrun *c = dynamic_cast(*it); if (c && c->varId == varid2 && c->value >= ai.num[0]) { // variable value is out of bounds, report error CheckBufferOverrun *checkBufferOverrun = dynamic_cast(c->owner); if (checkBufferOverrun) { std::vector index; index.push_back(c->value); checkBufferOverrun->arrayIndexOutOfBounds(tok, ai, index); break; } } } } const Token *parse(const Token &tok, std::list &checks) const { if (Token::Match(tok.previous(), "[;{}]")) { // Declaring variable.. if (Token::Match(&tok, "%type% %var% ;") && tok.isStandardType()) { checks.push_back(new ExecutionPathBufferOverrun(owner, arrayInfo, tok.next()->varId())); return tok.tokAt(2); } // Assign variable.. if (Token::Match(&tok, "%var% = %num% ;")) { assign_value(checks, tok.varId(), tok.strAt(2)); return tok.tokAt(3); } } // Assign variable (unknown value = 0).. if (Token::Match(&tok, "%var% =")) { assign_value(checks, tok.varId(), "0"); return &tok; } // Assign variable (unknown value = 0).. if (Token::Match(tok.tokAt(-2), "(|, & %var% ,|)")) { assign_value(checks, tok.varId(), "0"); return &tok; } // Array index.. if (Token::Match(&tok, "%var% [ %var% ]")) { array_index(&tok, checks, tok.varId(), tok.tokAt(2)->varId()); return tok.tokAt(3); } return &tok; } }; /// @} void CheckBufferOverrun::executionPaths() { // Parse all tokens and extract array info.. std::map arrayInfo; for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next()) { if (Token::Match(tok, "[;{}] %type%")) { ArrayInfo ai; if (!ai.declare(tok->next(), *_tokenizer)) continue; arrayInfo[ai.varid] = ai; } } // Perform checking - check how the arrayInfo arrays are used ExecutionPathBufferOverrun c(this, arrayInfo); checkExecutionPaths(_tokenizer->tokens(), &c); }