These docs are under active development and cover the v0.20 Kobicha security model.
Peios Learn
On this page
Print Full Specification
§3.2

ACL Format

An Access Control List (ACL) is the binary container for ACEs. DACLs, SACLs, and CAAP policy ACL blobs all use the same standard binary ACL format.

§3.2.1 Binary format

An ACL begins with an 8-byte header followed by AceCount ACEs packed contiguously:

Offset Size Field Description
0 1 AclRevision ACL revision number. Determines which ACE families the ACL formally permits.
1 1 Sbz1 Reserved. Preserved for compatibility but not interpreted by KACS.
2 2 AclSize Total size of the ACL in bytes, including the 8-byte header. Little-endian.
4 2 AceCount Number of ACEs in the ACL. Little-endian.
6 2 Sbz2 Reserved. Preserved for compatibility but not interpreted by KACS.

The ACE array begins immediately at offset 8. Each ACE is self-delimiting via its AceSize field. The parser walks the ACL by iterating exactly AceCount ACEs within the AclSize boundary.

§3.2.2 Parsing rules

  • AclSize MUST be at least 8 bytes.
  • AclSize MUST NOT exceed the containing buffer.
  • The ACL body MUST contain exactly AceCount ACEs within the declared AclSize.
  • Truncated ACEs, ACE overruns, or leftover bytes within AclSize are malformed.
  • The architectural maximum ACL size is 64 KB because AclSize is a 16-bit field.

ACE structure, ACE-type definitions, and revision-versus-ACE-family rules are specified in the ACE Types section.