界: Environment

本節包括原始程式碼之外的所有內容，但對於建立中產品的安全性仍至關重要。由於此領域所涵蓋的問題與原始程式碼沒有直接關係，因此我們將其與其他領域分開。

PHP Misconfiguration: Missing open_basedir Entry

Abstract

若給予 PHP 程式存取整個 file system 的權限，可讓攻擊者讀取、寫入或建立他們原本不該擁有存取權的檔案。

Explanation

若啟用 open_basedir 組態選項，該選項會試圖阻止 PHP 程式對 php.ini 中所指定的目錄結構以外的檔案執行操作。如果沒有使用 open_basedir 選項指定任何目錄，則在 PHP 下執行的程式將被授予擁有本地 file system 上所有檔案的完整存取權，這會使攻擊者可讀取、寫入或建立他們原本不該擁有存取權的檔案。

若無法透過 open_basedir 指定限制的目錄集，可能會讓攻擊者更容易發動其他盜取攻擊。

雖然 open_basedir 選項可保證系統的安全性，但其執行方式卻受到 race condition 的不利影響，這可能會讓攻擊者在某些情況下略過該選項所定義的限制[2]。PHP 執行存取權限檢查和開啟檔案間，會存在 time-of-check、time-of-use (TOCTOU) race condition。與其他語言中 file system 的 race condition 相同，此種情況會讓攻擊者將指向透過 access control 檢查的 symlink 替換成另一個原來不能通過測試的檔案，以取得受保護檔案的存取權。

此類攻擊針對的弱點大小視執行存取檢查和開啟檔案間的時間長短而定。即使連續執行呼叫，現今的作業系統也無法保證在處理程序讓出 CPU 之前執行的程式碼數量。攻擊者有許多技術來加長時間長度，使得盜取攻擊更加容易，但即使是很小的時間長度，此攻擊企圖也可以不斷的重複，直到成功為止。

References

[1] M. Achour et al. PHP Manual

[2] Stefan Esser PHP open_basedir Race Condition Vulnerability

[3] open_basedir Confusion

[4] Artur Maj Securing PHP

[5] Emmanuel Dreyfus Securing Systems with Chroot

[6] Standards Mapping - Common Weakness Enumeration CWE ID 284

[7] Standards Mapping - DISA Control Correlation Identifier Version 2 CCI-000213, CCI-002165

[8] Standards Mapping - FIPS200 AC

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

[10] Standards Mapping - NIST Special Publication 800-53 Revision 4 AC-3 Access Enforcement (P1)

[11] Standards Mapping - NIST Special Publication 800-53 Revision 5 AC-3 Access Enforcement

[12] Standards Mapping - OWASP API 2023 API8 Security Misconfiguration

[13] Standards Mapping - OWASP Application Security Verification Standard 4.0 1.4.2 Access Control Architectural Requirements (L2 L3), 1.4.4 Access Control Architectural Requirements (L2 L3)

[14] Standards Mapping - OWASP Mobile 2014 M5 Poor Authorization and Authentication

[15] Standards Mapping - OWASP Top 10 2004 A2 Broken Access Control

[16] Standards Mapping - OWASP Top 10 2007 A10 Failure to Restrict URL Access

[17] Standards Mapping - OWASP Top 10 2010 A8 Failure to Restrict URL Access

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

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

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

[21] Standards Mapping - Payment Card Industry Data Security Standard Version 1.1 Requirement 6.5.2, Requirement 7.2

[22] Standards Mapping - Payment Card Industry Data Security Standard Version 1.2 Requirement 6.5.10, Requirement 7.2

[23] Standards Mapping - Payment Card Industry Data Security Standard Version 2.0 Requirement 6.5.8, Requirement 7.2

[24] Standards Mapping - Payment Card Industry Data Security Standard Version 3.0 Requirement 6.5.8, Requirement 7.2

[25] Standards Mapping - Payment Card Industry Data Security Standard Version 3.1 Requirement 6.5.8, Requirement 7.2

[26] Standards Mapping - Payment Card Industry Data Security Standard Version 3.2 Requirement 6.5.8, Requirement 7.2

[27] Standards Mapping - Payment Card Industry Data Security Standard Version 3.2.1 Requirement 6.5.8, Requirement 7.2

[28] Standards Mapping - Payment Card Industry Data Security Standard Version 4.0 Requirement 6.2.4, Requirement 7.3.2

[29] Standards Mapping - Payment Card Industry Software Security Framework 1.0 Control Objective 5.4 - Authentication and Access Control

[30] Standards Mapping - Payment Card Industry Software Security Framework 1.1 Control Objective 5.4 - Authentication and Access Control

[31] Standards Mapping - Payment Card Industry Software Security Framework 1.2 Control Objective 5.4 - Authentication and Access Control, Control Objective C.2.3 - Web Software Access Controls

[32] Standards Mapping - Security Technical Implementation Guide Version 3.1 APP3480.1 CAT II

[33] Standards Mapping - Security Technical Implementation Guide Version 3.4 APP3480.1 CAT I

[34] Standards Mapping - Security Technical Implementation Guide Version 3.5 APP3480.1 CAT I

[35] Standards Mapping - Security Technical Implementation Guide Version 3.6 APP3480.1 CAT I

[36] Standards Mapping - Security Technical Implementation Guide Version 3.7 APP3480.1 CAT I

[37] Standards Mapping - Security Technical Implementation Guide Version 3.9 APP3480.1 CAT I

[38] Standards Mapping - Security Technical Implementation Guide Version 3.10 APP3480.1 CAT I

[39] Standards Mapping - Security Technical Implementation Guide Version 4.2 APSC-DV-000460 CAT I, APSC-DV-000470 CAT II

[40] Standards Mapping - Security Technical Implementation Guide Version 4.3 APSC-DV-000460 CAT I, APSC-DV-000470 CAT II

[41] Standards Mapping - Security Technical Implementation Guide Version 4.4 APSC-DV-000460 CAT I, APSC-DV-000470 CAT II

[42] Standards Mapping - Security Technical Implementation Guide Version 4.5 APSC-DV-000460 CAT I, APSC-DV-000470 CAT II

[43] Standards Mapping - Security Technical Implementation Guide Version 4.6 APSC-DV-000460 CAT I, APSC-DV-000470 CAT II

[44] Standards Mapping - Security Technical Implementation Guide Version 4.7 APSC-DV-000460 CAT I, APSC-DV-000470 CAT II

[45] Standards Mapping - Security Technical Implementation Guide Version 4.8 APSC-DV-000460 CAT I, APSC-DV-000470 CAT II

[46] Standards Mapping - Security Technical Implementation Guide Version 4.9 APSC-DV-000460 CAT I, APSC-DV-000470 CAT II

[47] Standards Mapping - Security Technical Implementation Guide Version 4.10 APSC-DV-000460 CAT I, APSC-DV-000470 CAT II

[48] Standards Mapping - Security Technical Implementation Guide Version 4.11 APSC-DV-000460 CAT I, APSC-DV-000470 CAT II

[49] Standards Mapping - Security Technical Implementation Guide Version 4.1 APSC-DV-000460 CAT I, APSC-DV-000470 CAT II

[50] Standards Mapping - Security Technical Implementation Guide Version 5.1 APSC-DV-000460 CAT I, APSC-DV-000470 CAT II

[51] Standards Mapping - Security Technical Implementation Guide Version 5.2 APSC-DV-000460 CAT I, APSC-DV-000470 CAT II

[52] Standards Mapping - Security Technical Implementation Guide Version 5.3 APSC-DV-000460 CAT I, APSC-DV-000470 CAT II

[53] Standards Mapping - Security Technical Implementation Guide Version 6.1 APSC-DV-000460 CAT I, APSC-DV-000470 CAT II

[54] Standards Mapping - Web Application Security Consortium Version 2.00 Application Misconfiguration (WASC-15)

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