Memory Leak: Reallocation

C/C++
COBOL

Abstract

程式重新調整分配記憶體區塊的大小。若重新調整大小失敗，就會洩露原始區塊。

Explanation

記憶體洩露有兩個常見的原因 (有時這兩個原因會一起出現)：

- 錯誤條件以及其他異常情況。

- 對於程式中負責釋放記憶體的部分混淆了。

大部分記憶體洩漏會導致一般軟體可靠性問題，但是如果攻擊者能夠蓄意觸發資源的洩漏，攻擊者就可能會發動 Denial of Service 攻擊 (藉由損壞程式)，或利用因記憶體不足的狀況 [1] 導致的其他非預期程式行為。

範例 1：以下的 C 函數在呼叫 realloc() 調整原始分配大小失敗時，洩露了分配記憶體區塊。


char* getBlocks(int fd) {
  int amt;
  int request = BLOCK_SIZE;
  char* buf = (char*) malloc(BLOCK_SIZE + 1);
  if (!buf) {
    goto ERR;
  }
  amt = read(fd, buf, request);
  while ((amt % BLOCK_SIZE) != 0) {
     if (amt < request) {
        goto ERR;
     }
     request = request + BLOCK_SIZE;
     buf = realloc(buf, request);
     if (!buf) {
        goto ERR;
     }
     amt = read(fd, buf, request);
  }

  return buf;

  ERR:
  if (buf) {
    free(buf);
  }
  return NULL;
}

References

[1] J. Whittaker and H. Thompson How to Break Software Security Addison Wesley

[2] Standards Mapping - CIS Azure Kubernetes Service Benchmark 1

[3] Standards Mapping - CIS Amazon Elastic Kubernetes Service Benchmark 5

[4] Standards Mapping - CIS Amazon Web Services Foundations Benchmark 2

[5] Standards Mapping - CIS Google Kubernetes Engine Benchmark normal

[6] Standards Mapping - Common Weakness Enumeration CWE ID 401

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

[8] Standards Mapping - General Data Protection Regulation (GDPR) Indirect Access to Sensitive Data

[9] Standards Mapping - Motor Industry Software Reliability Association (MISRA) C Guidelines 2012 Rule 21.3

[10] Standards Mapping - Motor Industry Software Reliability Association (MISRA) C++ Guidelines 2008 Rule 18-4-1

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

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

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

[14] Standards Mapping - OWASP Mobile Application Security Verification Standard 2.0 MASVS-STORAGE-2

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

desc.controlflow.cpp.memory_leak_reallocation

Abstract

程式會調整配置的記憶體區塊大小。如果調整大小失敗，就會洩漏原始區塊。

Explanation

記憶體洩漏有兩個常見且有時重疊的原因：

- 錯誤條件以及其他異常情況。

- 不確定程式的哪一部分負責釋放記憶體。

大多數的記憶體洩漏會導致一般的軟體可靠性問題，但是如果攻擊者蓄意觸發記憶體洩漏，則攻擊者可能可以發動 Denial of Service 攻擊 (透過使程式當機的方式)，或利用由記憶不足狀況導致的其他意外程式行為[1]。

範例 1：如果對 realloc() 的呼叫未能調整原始配置的大小，則以下 Micro Focus COBOL 程式就會洩漏配置的記憶體區塊。


CALL "malloc" USING
    BY VALUE mem-size
    RETURNING mem-pointer
END-CALL

ADD 1000 TO mem-size

CALL "realloc" USING
    BY VALUE mem-pointer
    BY VALUE mem-size
    RETURNING mem-pointer
END-CALL

IF mem-pointer <> null
    CALL "free" USING
        BY VALUE mem-pointer
    END-CALL
END-IF