Php intval () decimal Security Vulnerability Analysis

This article first introduces the simple usage of php intval, which can convert characters, numbers, and decimals into gray-numeric data. However, some problems may occur during conversion, such as converting decimal 1.1 to 1, see the instance below.

Convert a variable to an integer.

Syntax: int intval (mixed var, int [base]);

Return Value: integer

Function types: PHP system functions

 
Description

This function converts a variable to an integer. The base parameter that can be omitted is the basis for conversion. The default value is 10. The converted variable var can be any type variable outside the array or class.

Security vulnerability analysis due to improper use of intval ()

The intval function has a feature: "conversion starts only when a number or positive or negative sign is encountered, and the conversion ends when a non-number or string ends ", in some applications, due to insufficient understanding of the intval function, improper use may cause security vulnerabilities caused by bypassing some security judgments.

Ii. Analysis

The Code is as follows:

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PHP_FUNCTION (intval) { Zval ** num, ** arg_base; Int base; Switch (ZEND_NUM_ARGS ()){ Case 1: If (zend_get_parameters_ex (1, & num) = FAILURE ){ WRONG_PARAM_COUNT; } Base = 10; Break; Case 2: If (zend_get_parameters_ex (2, & num, & arg_base) = FAILURE ){ WRONG_PARAM_COUNT; } Convert_to_long_ex (arg_base ); Base = Z_LVAL_PP (arg_base ); Break; Default: WRONG_PARAM_COUNT; } RETVAL_ZVAL (* num, 1, 0 ); Convert_to_long_base (return_value, base ); } Zend/zend_operators.c-> convert_to_long_base () ...... Case IS_STRING: Strval = Z_STRVAL_P (op ); Z_LVAL_P (op) = strtol (strval, NULL, base ); STR_FREE (strval ); Break;

When the intval function receives a string parameter, it calls convert_to_long_base () for processing, and then calls Z_LVAL_P (op) = strtol (strval, NULL, base). The strtol function is used to process the parameter.

The function prototype is as follows:

Long int strtol (const char * nptr, char ** endptr, int base );

This function converts the nptr parameter to a growth integer number based on the base parameter. The base parameter ranges from 2 to 36, or 0. the base parameter indicates the base mode. For example, if the base value is 10, the base value is 10. If the base value is 16, the base value is hexadecimal.

The process is as follows:

Strtol () scans the nptr parameter string, skips the leading space character, and ends the conversion only when a number or positive or negative sign is encountered, and return the result.

When intval is used in the if and so on, it will cause the judgment to be de-meaningful, leading to security vulnerabilities.

Iii. Test code

The Code is as follows:

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<? Php USD o = 0.1; For ($ a = 1; $ a <100; $ a ++ ){ $ O + = 0.1; Echo "<br/> intval ($ o) =". intval ($ o ); If (intval ($ o )){ Print ("& nbsp; true "); } Else { Print ("& nbsp; false "); } }?> Output result: Intval (0.2) = 0 false Intval (0.3) = 0 false Intval (0.4) = 0 false Intval (0.5) = 0 false Intval (0.6) = 0 false Intval (0.7) = 0 false Intval (0.8) = 0 false Intval (0.9) = 0 false Intval (1) = 0 false Intval (1.1) = 1 true Intval (1.2) = 1 true Intval (1.3) = 1 true Intval (1.4) = 1 true Intval (1.5) = 1 true Intval (1.6) = 1 true Intval (1.7) = 1 true Intval (1.8) = 1 true Intval (1.9) = 1 true Intval (2) = 2 true .....

Differences between php intval and int

The Code is as follows:

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$ T = '000000 '; Echo gettype (int) ($ t )); Echo 'Echo gettype (intval ($ t )); // Output result: integer value: 165 $ T = 'a165 '; Echo gettype (int) ($ t )); Echo 'Echo gettype (intval ($ t )); // Result integer value: 0, 0 $ String = "2a "; $ String1 = intval ($ string ); Echo '$ string1 value:'. $ string1. '$ string2 value:'; // The variable is not output in single quotes and is output as is. $ String2 = (int) ($ string ); Echo $ string2