CWE-185 不正确的正则表达式

Incorrect Regular Expression

结构: Simple

Abstraction: Base

状态: Draft

被利用可能性: unkown

基本描述

The software specifies a regular expression in a way that causes data to be improperly matched or compared.

扩展描述

When the regular expression is used in protection mechanisms such as filtering or validation, this may allow an attacker to bypass the intended restrictions on the incoming data.

相关缺陷

  • cwe_Nature: ChildOf cwe_CWE_ID: 697 cwe_View_ID: 1000 cwe_Ordinal: Primary

  • cwe_Nature: CanPrecede cwe_CWE_ID: 187 cwe_View_ID: 1000

  • cwe_Nature: CanPrecede cwe_CWE_ID: 182 cwe_View_ID: 1000

适用平台

Language: {'cwe_Class': 'Language-Independent', 'cwe_Prevalence': 'Undetermined'}

常见的影响

范围 影响 注释
Other ['Unexpected State', 'Varies by Context'] When the regular expression is not correctly specified, data might have a different format or type than the rest of the program expects, producing resultant weaknesses or errors.
Access Control Bypass Protection Mechanism In PHP, regular expression checks can sometimes be bypassed with a null byte, leading to any number of weaknesses.

可能的缓解方案

MIT-45 Architecture and Design

策略: Refactoring

Regular expressions can become error prone when defining a complex language even for those experienced in writing grammars. Determine if several smaller regular expressions simplify one large regular expression. Also, subject the regular expression to thorough testing techniques such as equivalence partitioning, boundary value analysis, and robustness. After testing and a reasonable confidence level is achieved, a regular expression may not be foolproof. If an exploit is allowed to slip through, then record the exploit and refactor the regular expression.

示例代码

例

The following code takes phone numbers as input, and uses a regular expression to reject invalid phone numbers.

bad Perl

$phone = GetPhoneNumber();
if ($phone =~ /\d+-\d+/) {
# looks like it only has hyphens and digits
system("lookup-phone $phone");
}
else {
error("malformed number!");
}

An attacker could provide an argument such as: "; ls -l ; echo 123-456" This would pass the check, since "123-456" is sufficient to match the "\d+-\d+" portion of the regular expression.

分析过的案例

标识 说明 链接
CVE-2002-2109 Regexp isn't "anchored" to the beginning or end, which allows spoofed values that have trusted values as substrings. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2002-2109
CVE-2005-1949 Regexp for IP address isn't anchored at the end, allowing appending of shell metacharacters. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-1949
CVE-2001-1072 Bypass access restrictions via multiple leading slash, which causes a regular expression to fail. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2001-1072
CVE-2000-0115 Local user DoS via invalid regular expressions. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2000-0115
CVE-2002-1527 chain: Malformed input generates a regular expression error that leads to information exposure. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2002-1527
CVE-2005-1061 Certain strings are later used in a regexp, leading to a resultant crash. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-1061
CVE-2005-2169 MFV. Regular expression intended to protect against directory traversal reduces ".../...//" to "../". https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-2169
CVE-2005-0603 Malformed regexp syntax leads to information exposure in error message. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-0603
CVE-2005-1820 Code injection due to improper quoting of regular expression. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-1820
CVE-2005-3153 Null byte bypasses PHP regexp check. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-3153
CVE-2005-4155 Null byte bypasses PHP regexp check. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-4155

Notes

Relationship While there is some overlap with whitelist/blacklist problems, this entry is intended to deal with incorrectly written regular expressions, regardless of their intended use. Not every regular expression is intended for use as a whitelist or blacklist. In addition, whitelists and blacklists can be implemented using other mechanisms besides regular expressions. Research Gap Regexp errors are likely a primary factor in many MFVs, especially those that require multiple manipulations to exploit. However, they are rarely diagnosed at this level of detail.

分类映射

映射的分类名 ImNode ID Fit Mapped Node Name
PLOVER Regular Expression Error

相关攻击模式

  • CAPEC-15
  • CAPEC-6
  • CAPEC-79

引用