Uninitialized Variable

Abstract

程式能夠在變數被初始化之前使用它。

Explanation

在 .Net 中，會將靜態變數初始化為預設值，但是如果未進行初始化就直接使用那些變數，將可能導致以業務邏輯為主的問題，或者可能被用於執行阻斷服務 (DoS) 攻擊。程式永遠不會使用變數的預設值。

對於程式設計師來說，通常不會使用在程式碼中 Uninitialized Variable 來處理錯誤或是處理一些特殊的情況。對 Uninitialized Variable 提出的警告有時能夠指出程式碼中的打字錯誤。

範例 1：下列程式碼將由 .Net 編譯器在不會發生任何錯誤的情況下進行編譯。不過，下列陳述式 int a = (Int32)i + (Int32)j; 會拋出無法處理的異常，並使應用程式在執行階段當機。


    class Program
        {
            static int? i = j;
            static int? j;
            static void Main(string[] args)
            {
                j = 100;
                int a = (Int32)i + (Int32)j;

                Console.WriteLine(i);
                Console.WriteLine(j);
                Console.WriteLine(a);
            }
        }

多數 Uninitialized Variable 問題都是由軟體可靠性造成的，但是如果攻擊者能夠使 Uninitialized Variable 被使用，就能發動 Denial of Service 攻擊。

References

[1] Standards Mapping - Common Weakness Enumeration CWE ID 457, CWE ID 824

[2] Standards Mapping - Common Weakness Enumeration Top 25 2024 [12] CWE ID 020, [20] CWE ID 119

[3] Standards Mapping - DISA Control Correlation Identifier Version 2 CCI-001094

[4] Standards Mapping - Motor Industry Software Reliability Association (MISRA) C Guidelines 2012 Rule 9.1

[5] Standards Mapping - Motor Industry Software Reliability Association (MISRA) C Guidelines 2023 Rule 9.1

[6] Standards Mapping - Motor Industry Software Reliability Association (MISRA) C++ Guidelines 2008 Rule 8-5-1

[7] Standards Mapping - Motor Industry Software Reliability Association (MISRA) C++ Guidelines 2023 Rule 11.6.2

[8] Standards Mapping - NIST Special Publication 800-53 Revision 4 SC-5 Denial of Service Protection (P1)

[9] Standards Mapping - NIST Special Publication 800-53 Revision 5 SC-5 Denial of Service Protection

[10] Standards Mapping - OWASP Top 10 2004 A9 Application Denial of Service

[11] Standards Mapping - Payment Card Industry Data Security Standard Version 1.1 Requirement 6.5.9

[12] Standards Mapping - SANS Top 25 2009 Risky Resource Management - CWE ID 665

[13] Standards Mapping - Security Technical Implementation Guide Version 3.1 APP6080 CAT II

[14] Standards Mapping - Security Technical Implementation Guide Version 3.4 APP6080 CAT II

[15] Standards Mapping - Security Technical Implementation Guide Version 3.5 APP6080 CAT II

[16] Standards Mapping - Security Technical Implementation Guide Version 3.6 APP6080 CAT II

[17] Standards Mapping - Security Technical Implementation Guide Version 3.7 APP6080 CAT II

[18] Standards Mapping - Security Technical Implementation Guide Version 3.9 APP6080 CAT II

[19] Standards Mapping - Security Technical Implementation Guide Version 3.10 APP6080 CAT II

[20] Standards Mapping - Security Technical Implementation Guide Version 4.2 APSC-DV-002400 CAT II

[21] Standards Mapping - Security Technical Implementation Guide Version 4.3 APSC-DV-002400 CAT II

[22] Standards Mapping - Security Technical Implementation Guide Version 4.4 APSC-DV-002400 CAT II

[23] Standards Mapping - Security Technical Implementation Guide Version 4.5 APSC-DV-002400 CAT II

[24] Standards Mapping - Security Technical Implementation Guide Version 4.6 APSC-DV-002400 CAT II

[25] Standards Mapping - Security Technical Implementation Guide Version 4.7 APSC-DV-002400 CAT II

[26] Standards Mapping - Security Technical Implementation Guide Version 4.8 APSC-DV-002400 CAT II

[27] Standards Mapping - Security Technical Implementation Guide Version 4.9 APSC-DV-002400 CAT II

[28] Standards Mapping - Security Technical Implementation Guide Version 4.10 APSC-DV-002400 CAT II

[29] Standards Mapping - Security Technical Implementation Guide Version 4.11 APSC-DV-002400 CAT II

[30] Standards Mapping - Security Technical Implementation Guide Version 4.1 APSC-DV-002400 CAT II

[31] Standards Mapping - Security Technical Implementation Guide Version 5.1 APSC-DV-002400 CAT II

[32] Standards Mapping - Security Technical Implementation Guide Version 5.2 APSC-DV-002400 CAT II

[33] Standards Mapping - Security Technical Implementation Guide Version 5.3 APSC-DV-002400 CAT II

[34] Standards Mapping - Security Technical Implementation Guide Version 6.1 APSC-DV-002400 CAT II

[35] Standards Mapping - Smart Contract Weakness Classification SWC-109

[36] Standards Mapping - Web Application Security Consortium Version 2.00 Denial of Service (WASC-10)

[37] Standards Mapping - Web Application Security Consortium 24 + 2 Denial of Service

desc.structural.dotnet.uninitialized_variable

Abstract

程式可能會在初始化之前使用變數。

Explanation

根據預設，C 和 C++ 中的堆疊變數不會被初始化。它們的初始值取決於當函數被呼叫時，其在堆疊中發生的情況而定。程式永遠不會使用 Uninitialized Variable 的值。

對於程式設計師來說，通常不會使用在程式碼中 Uninitialized Variable 來處理錯誤或是處理一些特殊的情況。對 Uninitialized Variable 提出的警告有時能夠指出程式碼中的打字錯誤。

範例 1：以下 switch 陳述式企圖為變數 aN 和 bN 設定值，但是在預設案例中，程式設計師不小心將 aN 的值設定了兩次。


switch (ctl) {
  case -1:
    aN = 0; bN = 0;
    break;
  case 0:
    aN = i; bN = -i;
    break;
  case 1:
    aN = i + NEXT_SZ; bN = i - NEXT_SZ;
    break;
  default:
    aN = -1; aN = -1;
    break;
}

大部分的 Uninitialized Variable 都會導致一般軟體可靠性問題，但是如果攻擊者蓄意觸發使用 Uninitialized Variable，就能夠透過使程式當機的方式發動 Denial of Service 攻擊。在適當的情況下，攻擊者可以藉由在呼叫函數之前影響堆疊中的數值來控制 Uninitialized Variable 的值。