CWE-1267 Base Rascunho

Policy Uses Obsolete Encoding

This vulnerability occurs when a hardware system uses outdated or deprecated encoding methods to enforce security policies and access controls.

Definição

What is CWE-1267?

This vulnerability occurs when a hardware system uses outdated or deprecated encoding methods to enforce security policies and access controls.
In a System-on-a-Chip (SoC), different hardware components constantly generate transactions to read, write, or perform actions like reset or compute. Each transaction includes identifiers for its source and destination, and is often tagged with a Security Token. This token acts as a key, telling the destination what actions the transaction is permitted to perform. A policy encoder is responsible for creating these tokens by mapping transaction details to specific security permissions. A critical security flaw arises when this policy encoder relies on an obsolete or no-longer-trusted encoding scheme. Using weak or deprecated encoding undermines the entire access control system, as the security tokens can become predictable, forgeable, or easily bypassed. This leaves the chip's assets and functions vulnerable to unauthorized access or manipulation by malicious actors.
Impacto no mundo real

Real-world CVEs caused by CWE-1267

Ainda não há referências CVE públicas associadas a este CWE no catálogo da MITRE.

Como os atacantes a exploram

Trajeto do atacante passo a passo

  1. 1

    For example, consider a system that has four bus masters. The table below provides bus masters, their Security Tokens, and trust assumptions. | Bus Master | Security Token Decoding | Trust Assumptions | | --- | --- | --- | | Master_0 | "00" | Untrusted | | Master_1 | "01" | Trusted | | Master_2 | "10" | Untrusted | | Master_3 | "11" | Untrusted | The policy encoding is to be defined such that Security Token will be used in implemented access-controls. The bits in the bus transaction that contain Security-Token information are Bus_transaction [15:11]. The assets are the AES-Key registers for encryption or decryption. The key of 128 bits is implemented as a set of four, 32-bit registers. | Register | Field description | | --- | --- | | AES_ENC_DEC_KEY_0 | AES key [0:31] for encryption or decryption, Default 0x00000000 | | AES_ENC_DEC_KEY_1 | AES key [32:63] for encryption or decryption, Default 0x00000000 | | AES_ENC_DEC_KEY_2 | AES key [64:95] for encryption or decryption, Default 0x00000000 | | AES_ENC_DEC_KEY_4 | AES key [96:127] for encryption or decryption, Default 0x00000000 | Below is an example of a policy encoding scheme inherited from a previous project where all "ODD" numbered Security Tokens are trusted.

  2. 2

    The inherited policy encoding is obsolete and does not work for the new system where an untrusted bus master with an odd Security Token exists in the system, i.e., Master_3 whose Security Token is "11". Based on the old policy, the untrusted bus master (Master_3) has access to the AES-Key registers. To resolve this, a register AES_KEY_ACCESS_POLICY can be defined to provide necessary, access controls:

  3. 3

    New Policy: | | | | AES_KEY_ACCESS_POLICY | [31:0] Default 0x00000002 - agent with Security Token "1" has access to AES_ENC_DEC_KEY_0 through AES_ENC_DEC_KEY_4 registers | The AES_KEY_ACCESS_POLICY register defines which agents with a Security Token in the transaction can access the AES-key registers. Each bit in this 32-bit register defines a Security Token. There could be a maximum of 32 security Tokens that are allowed access to the AES-key registers. The number of the bit when set (i.e., "1") allows respective action from an agent whose identity matches the number of the bit and, if "0" (i.e., Clear), disallows the respective action to that corresponding agent. Thus, any bus master with Security Token "01" is allowed access to the AES-Key registers. Below is the Pseudo Code for policy encoding:

Exemplo de código vulnerável

Vulnerable code

For example, consider a system that has four bus masters. The table below provides bus masters, their Security Tokens, and trust assumptions. | Bus Master | Security Token Decoding | Trust Assumptions | | --- | --- | --- | | Master_0 | "00" | Untrusted | | Master_1 | "01" | Trusted | | Master_2 | "10" | Untrusted | | Master_3 | "11" | Untrusted | The policy encoding is to be defined such that Security Token will be used in implemented access-controls. The bits in the bus transaction that contain Security-Token information are Bus_transaction [15:11]. The assets are the AES-Key registers for encryption or decryption. The key of 128 bits is implemented as a set of four, 32-bit registers. | Register | Field description | | --- | --- | | AES_ENC_DEC_KEY_0 | AES key [0:31] for encryption or decryption, Default 0x00000000 | | AES_ENC_DEC_KEY_1 | AES key [32:63] for encryption or decryption, Default 0x00000000 | | AES_ENC_DEC_KEY_2 | AES key [64:95] for encryption or decryption, Default 0x00000000 | | AES_ENC_DEC_KEY_4 | AES key [96:127] for encryption or decryption, Default 0x00000000 | Below is an example of a policy encoding scheme inherited from a previous project where all "ODD" numbered Security Tokens are trusted.

Vulnerável 
If (Bus_transaction[14] == "1")
  	Trusted = "1"
  Else
  	Trusted = "0"
  If (trusted)
  	Allow access to AES-Key registers
  Else
  	Deny access to AES-Key registers
Exemplo de código seguro

Secure code

New Policy: | | | | AES_KEY_ACCESS_POLICY | [31:0] Default 0x00000002 - agent with Security Token "1" has access to AES_ENC_DEC_KEY_0 through AES_ENC_DEC_KEY_4 registers | The AES_KEY_ACCESS_POLICY register defines which agents with a Security Token in the transaction can access the AES-key registers. Each bit in this 32-bit register defines a Security Token. There could be a maximum of 32 security Tokens that are allowed access to the AES-key registers. The number of the bit when set (i.e., "1") allows respective action from an agent whose identity matches the number of the bit and, if "0" (i.e., Clear), disallows the respective action to that corresponding agent. Thus, any bus master with Security Token "01" is allowed access to the AES-Key registers. Below is the Pseudo Code for policy encoding:

Seguro 
Security_Token[4:0] = Bus_transaction[15:11]
  If (AES_KEY_ACCESS_POLICY[Security_Token] == "1")
  	Allow access to AES-Key registers
  Else
  	Deny access to AES-Key registers
What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Lista de verificação de prevenção

How to prevent CWE-1267

  • Architecture and Design / Implementation Security Token Decoders should be reviewed for design inconsistency and common weaknesses. Access and programming flows should be tested in both pre-silicon and post-silicon testing.
Sinais de deteção

How to detect CWE-1267

SAST High

Executar análise estática (SAST) na base de código à procura do padrão inseguro no fluxo de dados.

DAST Moderate

Executar testes dinâmicos de segurança de aplicações (DAST) contra o endpoint em execução.

Runtime Moderate

Monitorizar os registos em tempo de execução para traços de exceção invulgares, input malformado ou tentativas de contornar a autorização.

Code review Moderate

Revisão de código: sinalizar qualquer novo código que trate input desta superfície sem usar os ajudantes validados do framework.

Correção automática do Plexicus

O Plexicus deteta automaticamente o CWE-1267 e abre um PR de correção em menos de 60 segundos.

O Codex Remedium analisa cada commit, identifica esta fraqueza exata e entrega um pull request pronto para revisão com o patch. Sem tickets. Sem transferências.

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Perguntas frequentes

Frequently asked questions

O que é o CWE-1267?

This vulnerability occurs when a hardware system uses outdated or deprecated encoding methods to enforce security policies and access controls.

Qual a gravidade do CWE-1267?

A MITRE não publicou uma classificação de probabilidade de exploração para esta fraqueza. Trate-a como impacto médio até o seu modelo de ameaças provar o contrário.

Que linguagens ou plataformas são afetadas pelo CWE-1267?

MITRE lists the following affected platforms: Not OS-Specific, Not Architecture-Specific, Not Technology-Specific.

Como posso prevenir o CWE-1267?

Security Token Decoders should be reviewed for design inconsistency and common weaknesses. Access and programming flows should be tested in both pre-silicon and post-silicon testing.

Como é que o Plexicus deteta e corrige o CWE-1267?

O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-1267 em cada commit. Quando é encontrada uma correspondência, o nosso agente Codex Remedium abre um PR de correção com o código corrigido, testes e um resumo de uma linha para o revisor.

Onde posso saber mais sobre o CWE-1267?

A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/1267.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.

Fraquezas relacionadas

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Recursos

Further reading

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