Acelogic
1510d8c6ce
An EL2 monitor/hypervisor and toolchain that boots macOS 27 on the ASUS A16 (Snapdragon X2 Elite), with an Adreno Metal plug-in and IOGPU kext, and air2ir3, an AIR to Mesa ir3 shader compiler. MIT, with GPL-2.0 components listed in LICENSE and THIRD_PARTY_NOTICES.md. No Apple, Qualcomm, ASUS or Microsoft binaries are included.
87 lines
3.6 KiB
Python
Executable File
87 lines
3.6 KiB
Python
Executable File
#!/usr/bin/env python3
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# SPDX-License-Identifier: MIT
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"""Give a newly formatted, empty scratch APFS image the documented xART role.
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This creates guest test media, not SEP-backed trusted storage. Apple's host
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formatter restricts creation of this role to entitled callers. We instead
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encode the public APFS field in a separate, unmounted image file and retain
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the original. Never pass a physical device or an existing user filesystem.
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See docs/ISC-BOOT-MEDIA-20260922.md for the fresh-image creation recipe.
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"""
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import argparse
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import hashlib
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import json
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from pathlib import Path
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import struct
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MAX_SCRATCH_BYTES = 2 << 30 # permits native xART, Preboot and Hardware volumes
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def checksum(block):
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if len(block) != 4096:
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raise ValueError('expected a 4 KiB APFS metadata block')
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a = b = 0
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mod = 0xffffffff
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for word, in struct.iter_unpack('<I', block[8:]):
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a = (a + word) % mod
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b = (b + a) % mod
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low = mod - (a + b) % mod
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high = mod - (a + low) % mod
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return struct.pack('<II', low, high)
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def make_xart(source):
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if not 0x4000 <= len(source) <= MAX_SCRATCH_BYTES or len(source) % 0x4000:
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raise ValueError('scratch image size is outside the permitted bound')
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if source[32:36] != b'NXSB' or struct.unpack_from('<IQ', source, 36) != (4096, len(source) // 4096):
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raise ValueError('expected an unwrapped APFS scratch container')
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if source[:8] != checksum(source[:4096]):
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raise ValueError('invalid container superblock checksum')
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volumes = []
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for offset in range(0, len(source), 4096):
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if source[offset + 32:offset + 36] != b'APSB':
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continue
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block = source[offset:offset + 4096]
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if (block[:8] != checksum(block) or struct.unpack_from('<I', block, 24)[0] != 13 or
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struct.unpack_from('<H', block, 964)[0] != 0 or
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block[704:960].split(b'\0', 1)[0] != b'Snapintosh-xART' or
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any(struct.unpack_from('<5Q', block, 184)) or
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struct.unpack_from('<Q', block, 264)[0] != 1):
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raise ValueError('input is not the expected empty, unencrypted scratch volume')
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volumes.append(offset)
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if len(volumes) != 1:
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raise ValueError('expected exactly one freshly formatted volume superblock')
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result = bytearray(source)
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offset = volumes[0]
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struct.pack_into('<H', result, offset + 964, 0x100)
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result[offset:offset + 8] = checksum(result[offset:offset + 4096])
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return result, offset
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def main():
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ap = argparse.ArgumentParser(description=__doc__)
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ap.add_argument('source', type=Path)
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ap.add_argument('output', type=Path)
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ap.add_argument('--source-sha256', required=True)
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args = ap.parse_args()
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if not args.source.is_file() or args.source.is_symlink():
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ap.error('source must be a regular scratch image file')
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if args.source.stat().st_size > MAX_SCRATCH_BYTES:
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ap.error('source exceeds scratch image size limit')
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source = args.source.read_bytes()
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digest = hashlib.sha256(source).hexdigest()
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if digest != args.source_sha256:
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ap.error('fresh source image does not match the explicitly supplied SHA256')
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result, offset = make_xart(source)
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with args.output.open('xb') as stream:
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stream.write(result)
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print(json.dumps(dict(source=str(args.source), source_sha256=digest,
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output=str(args.output), bytes=len(result),
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sha256=hashlib.sha256(result).hexdigest(),
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superblock_offset=offset, role=256,
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sep_trusted_storage=False), indent=2))
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if __name__ == '__main__':
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main()
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