계: Security Features

소프트웨어 보안은 보안 소프트웨어가 아닙니다. 여기서는 인증, 액세스 제어, 기밀성, 암호화, 권한 관리 등의 항목에 대해 설명합니다.

Key Management: Empty HMAC Key

Abstract

빈 HMAC 키는 쉽게 해결할 수 없는 방식으로 시스템 보안을 손상시킬 수 있습니다.

Explanation

빈 HMAC 키를 사용하는 것은 좋은 방법이 아닙니다. HMAC의 암호화 효력은 메시지 authentication 값의 계산 및 확인에 사용되는 암호 키의 크기에 따라 달라집니다. 빈 키를 사용하면 HMAC 함수의 암호화 효력이 손상됩니다.
예제 1: 다음 코드는 빈 키를 사용하여 HMAC를 계산합니다.


...
DATA: lo_hmac TYPE Ref To cl_abap_hmac,
             Input_string type string.

CALL METHOD cl_abap_hmac=>get_instance
  EXPORTING
    if_algorithm = 'SHA3'
    if_key       = space
  RECEIVING
    ro_object    = lo_hmac.

" update HMAC with input
lo_hmac->update( if_data = input_string ).

" finalise hmac
lo_digest->final( ).

...

Example 1에 표시된 코드는 성공적으로 실행될 수 있지만 코드에 접근할 수 있는 사용자는 빈 HMAC 키가 사용되고 있음을 알아낼 수 있습니다. 프로그램을 공개한 후에는 프로그램에 패치를 적용해야만 빈 HMAC 키를 변경할 수 있습니다. 비양심적인 직원이 이 정보에 대한 접근 권한을 갖게 되면 이를 사용하여 HMAC 함수를 손상시킬 수 있습니다. 또한 Example 1의 코드는 forgery 및 key recovery 공격에 취약합니다.

References

[1] RFC 2104 - HMAC: Keyed-Hashing for Message Authentication Internet Engineering Task Force (IETF)

[2] New Results on NMAC/HMAC when Instantiated with Popular Hash Functions Journal of Universal Computer Science (J.UCS)

[3] Standards Mapping - Common Weakness Enumeration CWE ID 321

[4] Standards Mapping - Common Weakness Enumeration Top 25 2019 [13] CWE ID 287, [19] CWE ID 798

[5] Standards Mapping - Common Weakness Enumeration Top 25 2020 [14] CWE ID 287, [20] CWE ID 798

[6] Standards Mapping - Common Weakness Enumeration Top 25 2021 [14] CWE ID 287, [16] CWE ID 798

[7] Standards Mapping - Common Weakness Enumeration Top 25 2022 [14] CWE ID 287, [15] CWE ID 798

[8] Standards Mapping - Common Weakness Enumeration Top 25 2023 [13] CWE ID 287, [18] CWE ID 798

[9] Standards Mapping - Common Weakness Enumeration Top 25 2024 [14] CWE ID 287, [22] CWE ID 798

[10] Standards Mapping - DISA Control Correlation Identifier Version 2 CCI-002450

[11] Standards Mapping - FIPS200 IA

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

[13] Standards Mapping - NIST Special Publication 800-53 Revision 4 SC-12 Cryptographic Key Establishment and Management (P1), SC-13 Cryptographic Protection (P1)

[14] Standards Mapping - NIST Special Publication 800-53 Revision 5 SC-12 Cryptographic Key Establishment and Management, SC-13 Cryptographic Protection

[15] Standards Mapping - OWASP Application Security Verification Standard 4.0 2.6.3 Look-up Secret Verifier Requirements (L2 L3), 2.7.1 Out of Band Verifier Requirements (L1 L2 L3), 2.7.2 Out of Band Verifier Requirements (L1 L2 L3), 2.7.3 Out of Band Verifier Requirements (L1 L2 L3), 2.8.4 Single or Multi Factor One Time Verifier Requirements (L2 L3), 2.8.5 Single or Multi Factor One Time Verifier Requirements (L2 L3), 2.9.1 Cryptographic Software and Devices Verifier Requirements (L2 L3), 2.10.2 Service Authentication Requirements (L2 L3), 2.10.4 Service Authentication Requirements (L2 L3), 3.5.2 Token-based Session Management (L2 L3), 3.7.1 Defenses Against Session Management Exploits (L1 L2 L3), 6.2.1 Algorithms (L1 L2 L3), 6.4.1 Secret Management (L2 L3), 6.4.2 Secret Management (L2 L3), 9.2.3 Server Communications Security Requirements (L2 L3), 10.2.3 Malicious Code Search (L3)

[16] Standards Mapping - OWASP Mobile 2014 M6 Broken Cryptography

[17] Standards Mapping - OWASP Mobile 2024 M10 Insufficient Cryptography

[18] Standards Mapping - OWASP Mobile Application Security Verification Standard 2.0 MASVS-CRYPTO-2

[19] Standards Mapping - OWASP Top 10 2004 A8 Insecure Storage

[20] Standards Mapping - OWASP Top 10 2007 A8 Insecure Cryptographic Storage

[21] Standards Mapping - OWASP Top 10 2010 A7 Insecure Cryptographic Storage

[22] Standards Mapping - OWASP Top 10 2013 A6 Sensitive Data Exposure

[23] Standards Mapping - OWASP Top 10 2017 A3 Sensitive Data Exposure

[24] Standards Mapping - OWASP Top 10 2021 A02 Cryptographic Failures

[25] Standards Mapping - Payment Card Industry Data Security Standard Version 1.1 Requirement 6.5.8, Requirement 8.4

[26] Standards Mapping - Payment Card Industry Data Security Standard Version 1.2 Requirement 6.3.1.3, Requirement 6.5.8, Requirement 8.4

[27] Standards Mapping - Payment Card Industry Data Security Standard Version 2.0 Requirement 6.3.1, Requirement 6.5.3, Requirement 8.4

[28] Standards Mapping - Payment Card Industry Data Security Standard Version 3.0 Requirement 6.3.1, Requirement 6.5.3, Requirement 8.2.1

[29] Standards Mapping - Payment Card Industry Data Security Standard Version 3.1 Requirement 6.3.1, Requirement 6.5.3, Requirement 8.2.1

[30] Standards Mapping - Payment Card Industry Data Security Standard Version 3.2 Requirement 6.3.1, Requirement 6.5.3, Requirement 8.2.1

[31] Standards Mapping - Payment Card Industry Data Security Standard Version 3.2.1 Requirement 6.3.1, Requirement 6.5.3, Requirement 8.2.1

[32] Standards Mapping - Payment Card Industry Data Security Standard Version 4.0 Requirement 6.2.4, Requirement 6.5.3, Requirement 6.5.6, Requirement 8.3.2

[33] Standards Mapping - Payment Card Industry Data Security Standard Version 4.0.1 Requirement 6.2.4, Requirement 6.5.3, Requirement 6.5.6, Requirement 8.3.2

[34] Standards Mapping - Payment Card Industry Software Security Framework 1.0 Control Objective 7.2 - Use of Cryptography

[35] Standards Mapping - Payment Card Industry Software Security Framework 1.1 Control Objective 7.2 - Use of Cryptography, Control Objective B.2.3 - Terminal Software Design

[36] Standards Mapping - Payment Card Industry Software Security Framework 1.2 Control Objective 7.2 - Use of Cryptography, Control Objective B.2.3 - Terminal Software Design

[37] Standards Mapping - SANS Top 25 2009 Porous Defenses - CWE ID 259

[38] Standards Mapping - Security Technical Implementation Guide Version 3.1 APP3210.1 CAT II, APP3350 CAT I

[39] Standards Mapping - Security Technical Implementation Guide Version 3.4 APP3210.1 CAT II, APP3350 CAT I

[40] Standards Mapping - Security Technical Implementation Guide Version 3.5 APP3210.1 CAT II, APP3350 CAT I

[41] Standards Mapping - Security Technical Implementation Guide Version 3.6 APP3210.1 CAT II, APP3350 CAT I

[42] Standards Mapping - Security Technical Implementation Guide Version 3.7 APP3210.1 CAT II, APP3350 CAT I

[43] Standards Mapping - Security Technical Implementation Guide Version 3.9 APP3210.1 CAT II, APP3350 CAT I

[44] Standards Mapping - Security Technical Implementation Guide Version 3.10 APP3210.1 CAT II, APP3350 CAT I

[45] Standards Mapping - Security Technical Implementation Guide Version 4.2 APSC-DV-002010 CAT II

[46] Standards Mapping - Security Technical Implementation Guide Version 4.3 APSC-DV-002010 CAT II

[47] Standards Mapping - Security Technical Implementation Guide Version 4.4 APSC-DV-002010 CAT II

[48] Standards Mapping - Security Technical Implementation Guide Version 4.5 APSC-DV-002010 CAT II

[49] Standards Mapping - Security Technical Implementation Guide Version 4.6 APSC-DV-002010 CAT II

[50] Standards Mapping - Security Technical Implementation Guide Version 4.7 APSC-DV-002010 CAT II

[51] Standards Mapping - Security Technical Implementation Guide Version 4.8 APSC-DV-002010 CAT II

[52] Standards Mapping - Security Technical Implementation Guide Version 4.9 APSC-DV-002010 CAT II

[53] Standards Mapping - Security Technical Implementation Guide Version 4.10 APSC-DV-002010 CAT II

[54] Standards Mapping - Security Technical Implementation Guide Version 4.11 APSC-DV-002010 CAT II

[55] Standards Mapping - Security Technical Implementation Guide Version 4.1 APSC-DV-002010 CAT II

[56] Standards Mapping - Security Technical Implementation Guide Version 5.1 APSC-DV-002010 CAT II

[57] Standards Mapping - Security Technical Implementation Guide Version 5.2 APSC-DV-002010 CAT II

[58] Standards Mapping - Security Technical Implementation Guide Version 5.3 APSC-DV-002010 CAT II

[59] Standards Mapping - Security Technical Implementation Guide Version 6.1 APSC-DV-002010 CAT II

[60] Standards Mapping - Web Application Security Consortium Version 2.00 Information Leakage (WASC-13)

desc.structural.abap.key_management_empty_hmac_key

Abstract

빈 HMAC 키는 쉽게 해결할 수 없는 방식으로 시스템 보안을 손상시킬 수 있습니다.

Explanation


...
using (HMAC hmac = HMAC.Create("HMACSHA512"))
{
  string hmacKey = "";
  byte[] keyBytes = Encoding.ASCII.GetBytes(hmacKey);
  hmac.Key = keyBytes;
  ...
}
...

Example 1의 코드는 성공적으로 실행될 수 있지만 코드에 접근할 수 있는 사용자는 빈 HMAC 키가 사용되고 있음을 알아낼 수 있습니다. 프로그램을 공개한 후에는 프로그램에 패치를 적용해야만 빈 HMAC 키를 변경할 수 있습니다. 비양심적인 직원이 이 정보에 대한 접근 권한을 갖게 되면 이를 사용하여 HMAC 함수를 손상시킬 수 있습니다. 또한 Example 1의 코드는 forgery 및 key recovery 공격에 취약합니다.