界: Input Validation and Representation

輸入驗證和表示法問題是由中繼字元、替代編碼和數值表示法引起的。信任輸入會導致安全問題。問題包括：「Buffer Overflows」、「Cross-Site Scripting」攻擊、「SQL Injection」及其他許多問題。

Insecure Sanitizer Policy

Java/JSP

Abstract

使用使用者控制的資料或不可信賴的資料定義 HTML 序列化程式原則時，可能會允許攻擊者避開序列化需求，並啟動 Cross-site scripting (XSS) 攻擊。

Explanation

「輸入處理」這個概括性用語是指，對輸入資料執行驗證、序列化、篩選及編碼/解碼等功能。Cross-Site Scripting、SQL Injection 和程序控制弱點是由於輸入處理錯誤或缺少輸入處理而造成的。序列化輸入需要將輸入轉換成可接受的形式，通常在實作之外加上輸入驗證。HTML 序列化是指，清理並清除使用者輸入，以僅允許視為安全的標籤、屬性和元素。
實作一個徹底的 HTML 序列化原則很困難，成功實作的關鍵在於瞭解將使用資料的環境。每一個環境有其自己的弱點，無法一體適用。雖然使用 HTML 序列化程式 (例如 OWASP HTML 序列化程式) 防範 Web 應用程式中的 XSS 弱點是明智的做法，但是實作不當可能會導致產生虛假的安全感。
範例 1：以下 Java 程式碼使用使用者控制的輸入變數 elements 來建立 HTML 序列化程式原則：


...
String elements = prop.getProperty("AllowedElements");
...
public static final PolicyFactory POLICY_DEFINITION = new HtmlPolicyBuilder()
															.allowElements(elements)
															.toFactory();

....

惡意使用者會藉由提供 <script> 之類的危險元素給 elements，造成 HTML 序列化程式原則接受這些危險元素。

References

[1] OWASP Cross-Site Scripting (XSS) Prevention Cheat Sheet

[2] Understanding Malicious Content Mitigation for Web Developers CERT

[3] HTML 4.01 Specification W3

[4] Standards Mapping - Common Weakness Enumeration CWE ID 79, CWE ID 80

[5] Standards Mapping - Common Weakness Enumeration Top 25 2019 [2] CWE ID 079

[6] Standards Mapping - Common Weakness Enumeration Top 25 2020 [1] CWE ID 079

[7] Standards Mapping - Common Weakness Enumeration Top 25 2021 [2] CWE ID 079

[8] Standards Mapping - Common Weakness Enumeration Top 25 2022 [2] CWE ID 079

[9] Standards Mapping - Common Weakness Enumeration Top 25 2023 [2] CWE ID 079

[10] Standards Mapping - Common Weakness Enumeration Top 25 2024 [1] CWE ID 079

[11] Standards Mapping - DISA Control Correlation Identifier Version 2 CCI-001310

[12] Standards Mapping - FIPS200 SI

[13] Standards Mapping - General Data Protection Regulation (GDPR) Insufficient Data Protection

[14] Standards Mapping - NIST Special Publication 800-53 Revision 4 SI-10 Information Input Validation (P1), SI-15 Information Output Filtering (P0)

[15] Standards Mapping - NIST Special Publication 800-53 Revision 5 SI-10 Information Input Validation, SI-15 Information Output Filtering

[16] Standards Mapping - OWASP Application Security Verification Standard 4.0 5.3.3 Output Encoding and Injection Prevention Requirements (L1 L2 L3), 5.3.6 Output Encoding and Injection Prevention Requirements (L1 L2 L3)

[17] Standards Mapping - OWASP Mobile 2014 M7 Client Side Injection

[18] Standards Mapping - OWASP Mobile 2024 M4 Insufficient Input/Output Validation

[19] Standards Mapping - OWASP Top 10 2004 A4 Cross Site Scripting

[20] Standards Mapping - OWASP Top 10 2007 A1 Cross Site Scripting (XSS)

[21] Standards Mapping - OWASP Top 10 2010 A2 Cross-Site Scripting (XSS)

[22] Standards Mapping - OWASP Top 10 2013 A5 Security Misconfiguration

[23] Standards Mapping - OWASP Top 10 2017 A6 Security Misconfiguration

[24] Standards Mapping - OWASP Top 10 2021 A05 Security Misconfiguration

[25] Standards Mapping - Payment Card Industry Data Security Standard Version 1.1 Requirement 6.5.4

[26] Standards Mapping - Payment Card Industry Data Security Standard Version 1.2 Requirement 6.3.1.1, Requirement 6.5.1

[27] Standards Mapping - Payment Card Industry Data Security Standard Version 2.0 Requirement 6.5.7

[28] Standards Mapping - Payment Card Industry Data Security Standard Version 3.0 Requirement 6.5.7

[29] Standards Mapping - Payment Card Industry Data Security Standard Version 3.1 Requirement 6.5.7

[30] Standards Mapping - Payment Card Industry Data Security Standard Version 3.2 Requirement 6.5.7

[31] Standards Mapping - Payment Card Industry Data Security Standard Version 3.2.1 Requirement 6.5.7

[32] Standards Mapping - Payment Card Industry Data Security Standard Version 4.0 Requirement 6.2.4

[33] Standards Mapping - Payment Card Industry Data Security Standard Version 4.0.1 Requirement 6.2.4

[34] Standards Mapping - Payment Card Industry Software Security Framework 1.0 Control Objective 4.2 - Critical Asset Protection

[35] Standards Mapping - Payment Card Industry Software Security Framework 1.1 Control Objective 4.2 - Critical Asset Protection, Control Objective B.3.1 - Terminal Software Attack Mitigation, Control Objective B.3.1.1 - Terminal Software Attack Mitigation

[36] Standards Mapping - Payment Card Industry Software Security Framework 1.2 Control Objective 4.2 - Critical Asset Protection, Control Objective B.3.1 - Terminal Software Attack Mitigation, Control Objective B.3.1.1 - Terminal Software Attack Mitigation, Control Objective C.3.2 - Web Software Attack Mitigation

[37] Standards Mapping - SANS Top 25 2009 Insecure Interaction - CWE ID 079

[38] Standards Mapping - SANS Top 25 2010 Insecure Interaction - CWE ID 079

[39] Standards Mapping - SANS Top 25 2011 Insecure Interaction - CWE ID 079

[40] Standards Mapping - Security Technical Implementation Guide Version 3.1 APP3510 CAT I, APP3580 CAT I

[41] Standards Mapping - Security Technical Implementation Guide Version 3.4 APP3510 CAT I, APP3580 CAT I

[42] Standards Mapping - Security Technical Implementation Guide Version 3.5 APP3510 CAT I, APP3580 CAT I

[43] Standards Mapping - Security Technical Implementation Guide Version 3.6 APP3510 CAT I, APP3580 CAT I

[44] Standards Mapping - Security Technical Implementation Guide Version 3.7 APP3510 CAT I, APP3580 CAT I

[45] Standards Mapping - Security Technical Implementation Guide Version 3.9 APP3510 CAT I, APP3580 CAT I

[46] Standards Mapping - Security Technical Implementation Guide Version 3.10 APP3510 CAT I, APP3580 CAT I

[47] Standards Mapping - Security Technical Implementation Guide Version 5.3 APSC-DV-002530 CAT II

[48] Standards Mapping - Security Technical Implementation Guide Version 6.1 APSC-DV-002530 CAT II

[49] Standards Mapping - Web Application Security Consortium Version 2.00 Cross-Site Scripting (WASC-08)

[50] Standards Mapping - Web Application Security Consortium 24 + 2 Cross-Site Scripting

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