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
if ($phone =~ /d+-d+/) {
system("lookup-phone $phone");
}
else {
}
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
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