file/magic/Magdir/syd

#------------------------------------------------------------------------------
# $File: syd,v 1.1 2025/09/11 01:49:40 christos Exp $
# syd: file(1) magic for syd(1) encrypted files
#
# From: Ali Polatel <alip@chesswob.org>
# Documentation: https://man.exherbo.org/syd.7.html#Crypt_Sandboxing
# No defined extension yet; files are recognized by magic header only.
#
# Layout:
#   0..3   : "\x7fSYD"
#   4	   : version byte (current API: 3)
#   5..36  : HMAC (32 bytes, SHA256)
#   37..52 : IV (16 bytes)
#   53..   : ciphertext (AES-256-CTR)
#------------------------------------------------------------------------------

# Header and version
0		string		\x7fSYD		SYD encrypted file
>4		ubyte		x		\b, version %u
# Version 3: algorithm + HMAC/IV as hex blobs + ciphertext size
>>4		ubyte		=3		\b, AES-256-CTR; HMAC-SHA256:
>>>5		belong		 x		\b%08x
>>>9		belong		 x		\b%08x
>>>13		belong		 x		\b%08x
>>>17		belong		 x		\b%08x
>>>21		belong		 x		\b%08x
>>>25		belong		 x		\b%08x
>>>29		belong		 x		\b%08x
>>>33		belong		 x		\b%08x
>>>37		belong		 x		\b, IV:%08x
>>>41		belong		 x		\b%08x
>>>45		belong		 x		\b%08x
>>>49		belong		 x		\b%08x
>>>-0		offset-53	 x		\b, ciphertext %llu bytes

# End of syd