界: Time and State
分散式運算與時間和狀態相關。也就是說,為了使多個元件進行通訊,必須共用狀態,並且這一切都需要時間。
大多數的程式設計師將他們的工作擬人化。他們想採用一種控制執行緒來執行整個程式,就像他們必須自己完成這項工作一樣。但是,現代的電腦可以非常快速地切換工作,並且在多核心多 CPU 或分散式系統中,兩個事件可能恰好同時發生。瑕疵急於填補程式設計師在程式執行模型與實際情況之間的差距。這些瑕疵與執行緒、處理序、時間和資訊之間的意外互動有關。這些互動透過共用狀態發生:信號、變數、檔案系統,以及基本上任何可以儲存資訊的項目。
Race Condition: Singleton Member Field
Abstract
Servlet 成員欄位可能會允許某一使用者看見其他使用者的資料。
Explanation
許多 Servlet 開發人員並不了解 Servlet 都是單一個體。Servlet 只能有一個實例,而且當不同執行緒同時處理多個要求時,都會使用及重複使用該單一實例來處理這些要求。
這種誤解的結果為:由於開發人員使用 Servlet 成員欄位,所以使用者可能會看到其他使用者的資料。換句話說,將使用者資料儲存在 Servlet 成員欄位中會造成資料存取的 race condition。
範例 1:下面的 Servlet 將要求參數的值儲存在成員欄位中,並且接著會將該參數值回傳到回應輸出串流。
當這段程式碼在單一使用者環境中正常地運作時,如果兩個使用者幾乎同時存取此 Servlet,可能會導致這兩個要求處理器的執行緒以下列方式插入:
執行緒 1: 將「
執行緒 2: 將「
執行緒 1: 列印「
執行緒 2: 列印「
因此會向第一個使用者顯示第二個使用者的名稱。
這種誤解的結果為:由於開發人員使用 Servlet 成員欄位,所以使用者可能會看到其他使用者的資料。換句話說,將使用者資料儲存在 Servlet 成員欄位中會造成資料存取的 race condition。
範例 1:下面的 Servlet 將要求參數的值儲存在成員欄位中,並且接著會將該參數值回傳到回應輸出串流。
public class GuestBook extends HttpServlet {
String name;
protected void doPost (HttpServletRequest req, HttpServletResponse res) {
name = req.getParameter("name");
...
out.println(name + ", thanks for visiting!");
}
}
當這段程式碼在單一使用者環境中正常地運作時,如果兩個使用者幾乎同時存取此 Servlet,可能會導致這兩個要求處理器的執行緒以下列方式插入:
執行緒 1: 將「
Dick
」指派至 name
執行緒 2: 將「
Jane
」指派至 name
執行緒 1: 列印「
Jane, thanks for visiting!
」執行緒 2: 列印「
Jane, thanks for visiting!
」因此會向第一個使用者顯示第二個使用者的名稱。
References
[1] The Java Servlet Specification Sun Microsystems
[2] Standards Mapping - CIS Azure Kubernetes Service Benchmark 2.0
[3] Standards Mapping - CIS Amazon Elastic Kubernetes Service Benchmark 3.0
[4] Standards Mapping - CIS Amazon Web Services Foundations Benchmark 5
[5] Standards Mapping - CIS Google Kubernetes Engine Benchmark confidentiality
[6] Standards Mapping - CIS Kubernetes Benchmark partial
[7] Standards Mapping - Common Weakness Enumeration CWE ID 362, CWE ID 488
[8] Standards Mapping - Common Weakness Enumeration Top 25 2022 [22] CWE ID 362
[9] Standards Mapping - Common Weakness Enumeration Top 25 2023 [21] CWE ID 362
[10] Standards Mapping - DISA Control Correlation Identifier Version 2 CCI-001090, CCI-003178
[11] Standards Mapping - General Data Protection Regulation (GDPR) Access Violation
[12] Standards Mapping - NIST Special Publication 800-53 Revision 4 CM-6 Configuration Settings (P1), SC-4 Information in Shared Resources (P1)
[13] Standards Mapping - NIST Special Publication 800-53 Revision 5 CM-6 Configuration Settings, SC-4 Information in Shared System Resources
[14] Standards Mapping - OWASP Top 10 2007 A6 Information Leakage and Improper Error Handling
[15] Standards Mapping - OWASP Top 10 2021 A04 Insecure Design
[16] Standards Mapping - OWASP Application Security Verification Standard 4.0 1.11.2 Business Logic Architectural Requirements (L2 L3)
[17] Standards Mapping - Payment Card Industry Data Security Standard Version 1.2 Requirement 6.5.6
[18] Standards Mapping - Payment Card Industry Data Security Standard Version 2.0 Requirement 6.5.5
[19] Standards Mapping - Payment Card Industry Data Security Standard Version 3.0 Requirement 6.5.6
[20] Standards Mapping - Payment Card Industry Data Security Standard Version 3.1 Requirement 6.5.6
[21] Standards Mapping - Payment Card Industry Data Security Standard Version 3.2 Requirement 6.5.6
[22] Standards Mapping - Payment Card Industry Data Security Standard Version 3.2.1 Requirement 6.5.6
[23] Standards Mapping - Payment Card Industry Data Security Standard Version 4.0 Requirement 6.2.4
[24] Standards Mapping - Payment Card Industry Software Security Framework 1.0 Control Objective 4.2 - Critical Asset Protection
[25] Standards Mapping - Payment Card Industry Software Security Framework 1.1 Control Objective 4.2 - Critical Asset Protection, Control Objective B.3.3 - Terminal Software Attack Mitigation
[26] Standards Mapping - Payment Card Industry Software Security Framework 1.2 Control Objective 4.2 - Critical Asset Protection, Control Objective B.3.3 - Terminal Software Attack Mitigation
[27] Standards Mapping - SANS Top 25 2009 Insecure Interaction - CWE ID 362
[28] Standards Mapping - SANS Top 25 2010 Insecure Interaction - CWE ID 362
[29] Standards Mapping - Security Technical Implementation Guide Version 3.1 APP3630.1 CAT II
[30] Standards Mapping - Security Technical Implementation Guide Version 3.4 APP3630.1 CAT II
[31] Standards Mapping - Security Technical Implementation Guide Version 3.5 APP3630.1 CAT II
[32] Standards Mapping - Security Technical Implementation Guide Version 3.6 APP3630.1 CAT II
[33] Standards Mapping - Security Technical Implementation Guide Version 3.7 APP3630.1 CAT II
[34] Standards Mapping - Security Technical Implementation Guide Version 3.9 APP3630.1 CAT II
[35] Standards Mapping - Security Technical Implementation Guide Version 3.10 APP3630.1 CAT II
[36] Standards Mapping - Security Technical Implementation Guide Version 4.1 APSC-DV-001995 CAT II, APSC-DV-002380 CAT II
[37] Standards Mapping - Security Technical Implementation Guide Version 4.2 APSC-DV-001995 CAT II, APSC-DV-002380 CAT II
[38] Standards Mapping - Security Technical Implementation Guide Version 4.3 APSC-DV-001995 CAT II, APSC-DV-002380 CAT II
[39] Standards Mapping - Security Technical Implementation Guide Version 4.4 APSC-DV-001995 CAT II, APSC-DV-002380 CAT II
[40] Standards Mapping - Security Technical Implementation Guide Version 4.5 APSC-DV-001995 CAT II, APSC-DV-002380 CAT II
[41] Standards Mapping - Security Technical Implementation Guide Version 4.6 APSC-DV-001995 CAT II, APSC-DV-002380 CAT II
[42] Standards Mapping - Security Technical Implementation Guide Version 4.7 APSC-DV-001995 CAT II, APSC-DV-002380 CAT II
[43] Standards Mapping - Security Technical Implementation Guide Version 4.8 APSC-DV-001995 CAT II, APSC-DV-002380 CAT II
[44] Standards Mapping - Security Technical Implementation Guide Version 4.9 APSC-DV-001995 CAT II, APSC-DV-002380 CAT II
[45] Standards Mapping - Security Technical Implementation Guide Version 4.10 APSC-DV-001995 CAT II, APSC-DV-002380 CAT II
[46] Standards Mapping - Security Technical Implementation Guide Version 4.11 APSC-DV-001995 CAT II, APSC-DV-002380 CAT II
[47] Standards Mapping - Security Technical Implementation Guide Version 5.1 APSC-DV-001995 CAT II, APSC-DV-002380 CAT II
[48] Standards Mapping - Security Technical Implementation Guide Version 5.2 APSC-DV-001995 CAT II, APSC-DV-002380 CAT II
[49] Standards Mapping - Security Technical Implementation Guide Version 5.3 APSC-DV-001995 CAT II, APSC-DV-002380 CAT II
[50] Standards Mapping - Web Application Security Consortium Version 2.00 Information Leakage (WASC-13)
[51] Standards Mapping - Web Application Security Consortium 24 + 2 Information Leakage
desc.structural.java.singleton_member_field_race_condition