CWE-1267: Policy Uses Obsolete Encoding | Glexia
CWE-1267 (Policy Uses Obsolete Encoding) weakness overview with consequences, detection methods, mitigations, related CVEs and MITRE ATT&CK context.
Glexia's Take · Automated analysis
CWE-1267: Policy Uses Obsolete Encoding
Policy Uses Obsolete Encoding represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Executive Impact
- Confidentiality Integrity Availability Access Control: Modify Memory Read Memory Modify Files or Directories Read Files or Directories DoS: Resource Consumption (Other) Execute Unauthorized Code or Commands Gain Privileges or Assume Identity Bypass Protection Mechanism Reduce Reliability
Developer Pattern
CWE-1267 is the kind of defect developers can usually prevent with explicit validation, safer framework defaults, and tests that exercise hostile input or unsafe state transitions.
Automation confidence
high confidence from CWE-1267, 4.20.
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Official CWE Definition
CWE-1267: Policy Uses Obsolete Encoding
The product uses an obsolete encoding mechanism to implement access controls.
Within a System-On-a-Chip (SoC), various circuits and hardware engines generate transactions for the purpose of accessing (read/write) assets or performing various actions (e.g., reset, fetch, compute, etc.). Among various types of message information, a typical transaction is comprised of source identity (identifying the originator of the transaction) and a destination identity (routing the transaction to the respective entity). Sometimes the transactions are qualified with a Security Token. This Security Token helps the destination agent decide on the set of allowed actions (e.g., access to an asset for reads and writes). A policy encoder is used to map the bus transactions to Security Tokens that in turn are used as access-controls/protection mechanisms. A common weakness involves using an encoding which is no longer trusted, i.e., an obsolete encoding.
Developer And Remediation Guidance
How teams prevent and detect this weakness
Causes
- 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. 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: 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:
Remediation
- 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.
Detection
- Code review
- SAST
- DAST
- Focused regression tests
Mappings
Related CVEs, CWEs, and ATT&CK context
Related CWEs
ATT&CK Relevance
ATT&CK relevance is shown only when reviewed or responsibly inferred.