b38dea0597
Share Gaia assets and adapters, keep private profiles and development documents local, and update both public READMEs.
76 lines
3.1 KiB
Python
76 lines
3.1 KiB
Python
# SPDX-License-Identifier: MPL-2.0
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"""Read verified newc ramdisks, resolving hardlinks without extracting secrets."""
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import gzip
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from pathlib import PurePosixPath
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import stat
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import subprocess
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import re
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import os
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def read_newc(data):
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if data[:2] == b'\x1f\x8b':
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data = gzip.decompress(data)
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entries, payloads, offset = {}, {}, 0
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while offset + 110 <= len(data):
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header = data[offset:offset+110]
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if header[:6] != b'070701':
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raise ValueError('Expected newc ramdisk')
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fields = [int(header[6+i*8:14+i*8],16) for i in range(13)]
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inode, mode, uid, gid, links, mtime, size, major, minor, rmajor, rminor, namesize, check = fields
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name = data[offset+110:offset+110+namesize-1].decode()
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start = (offset+110+namesize+3)&~3
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offset = (start+size+3)&~3
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if name == 'TRAILER!!!':
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break
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path = PurePosixPath(name)
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if path.is_absolute() or '..' in path.parts or offset > len(data):
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raise ValueError('Invalid ramdisk entry')
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if name == '.':
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continue
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key = (major,minor,inode)
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payload = data[start:start+size]
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entries[str(path)] = {'mode':mode,'data':payload,'key':key,'links':links}
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if stat.S_ISREG(mode) and payload:
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payloads[key] = payload
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for entry in entries.values():
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if stat.S_ISREG(entry['mode']) and entry['links'] > 1 and not entry['data']:
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entry['data'] = payloads.get(entry['key'],b'')
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return entries
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def resolve(entries, name):
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import posixpath
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seen = set()
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while stat.S_ISLNK(entries[name]['mode']):
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if name in seen:
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raise ValueError('Cyclic ramdisk link')
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seen.add(name)
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link = entries[name]['data'].decode()
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name = posixpath.normpath(link.lstrip('/') if link.startswith('/') else posixpath.join(posixpath.dirname(name),link))
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if name.startswith('../'):
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raise ValueError('Link escapes ramdisk')
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return entries[name]['data']
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def select_helpers(entries, scratch, extra=()):
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"""Copy only explicit programs and their ELF dependencies, never /etc or /root."""
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selected = {}
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queue = ['bin/busybox','sbin/dropbear','sbin/dmsetup','lib/aarch64-linux-gnu/libnss_files.so.2', *extra]
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while queue:
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name = queue.pop()
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if name in selected:
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continue
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content = resolve(entries,name)
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selected[name] = content
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probe = scratch/'elf';probe.write_bytes(content)
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info = subprocess.check_output(['readelf','-ld',str(probe)],text=True,env={**os.environ, 'LC_ALL':'C'})
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interpreter = re.search(r'Requesting program interpreter: ([^\]]+)',info)
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if interpreter:
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queue.append(interpreter.group(1).lstrip('/'))
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for library in re.findall(r'\(NEEDED\).*\[([^\]]+)\]',info):
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found = next((base+library for base in ('lib/aarch64-linux-gnu/','usr/lib/aarch64-linux-gnu/','lib/','usr/lib/') if base+library in entries),None)
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if found is None:
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raise ValueError('Missing ramdisk library: '+library)
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queue.append(found)
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return selected
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