nso.py

import struct
import lz4.block
import sys
import hashlib
import binascii

def main(argc, argv):
    if (argc != 3):
        print 'Usage: %s in.nso out.bin'
        sys.exit(1)
    try:
        nso = file(argv[1], 'rb').read()
    except:
        print 'Error: failed to read %s!' % argv[1]
        sys.exit(1)
    try:
        out = open(argv[2], 'wb')
    except:
        print 'Error: failed to open %s for writing!' % argv[2]

    if nso[:4] != 'NSO0':
        print 'Error: file provided is not an NSO!'
        sys.exit(1)

    decmp = lz4.block.decompress

    toff, tloc, tsize = struct.unpack('<III', nso[0x10:0x1C])
    roff, rloc, rsize = struct.unpack('<III', nso[0x20:0x2C])
    doff, dloc, dsize = struct.unpack('<III', nso[0x30:0x3C])

    thash, rhash, dhash = nso[0xA0:0xC0], nso[0xC0:0xE0], nso[0xE0:0x100]

    print '.text: %08X-%08X' % (tloc, tloc+tsize)
    print '.rodata: %08X-%08X' % (rloc, rloc+rsize)
    print '.data: %08X-%08X' % (dloc, dloc+dsize)

    text = decmp(nso[toff:roff], uncompressed_size=tsize)
    ro = decmp(nso[roff:doff], uncompressed_size=rsize)
    data = decmp(nso[doff:], uncompressed_size=dsize)

    cthash = hashlib.sha256(text).digest()
    crhash = hashlib.sha256(ro).digest()
    cdhash = hashlib.sha256(data).digest()

    if cthash != thash:
        print 'Warning: .text SHA256 hash does not match! (%s != %s)' % (binascii.hexlify(cthash), binascii.hexlify(thash))
    if crhash != rhash:
        print 'Warning: .rodata SHA256 hash does not match! (%s != %s)' % (binascii.hexlify(crhash), binascii.hexlify(rhash))
    if cdhash != dhash:
        print 'Warning: .data SHA256 hash does not match! (%s != %s)' % (binascii.hexlify(cdhash), binascii.hexlify(dhash))

    out.write(text)
    out.seek(rloc)
    out.write(ro)
    out.seek(dloc)
    out.write(data)
    out.close()


if __name__=='__main__':
    main(len(sys.argv), sys.argv)

In the rare case someone tries to use this for another file type, it currently creates a 0 byte file, may want to move the NSO check above the second try/catch block...