Layers: Improve response if snappy not installed

volatility3/framework/layers/avml.py

@@ -2,13 +2,14 @@
 
 The user of the file doesn't have to worry about the compression,
 but random access is not allowed."""
-import io
 import struct
 from typing import Tuple, List, Optional
 
 from volatility3.framework import exceptions, interfaces, constants
 from volatility3.framework.layers import segmented
 
+vollog = logging.getLogger(__name__)
+
 try:
     import snappy
 
@@ -17,147 +18,6 @@ except ImportError:
     HAS_SNAPPY = False
 
 
-class SnappyFraming:
-    def __init__(self):
-        pass
-
-    # crc32-c (Castagnoli) (crc32c_poly=0x1EDC6F41)
-    crc32c_table = [
-        0x00000000, 0xF26B8303, 0xE13B70F7, 0x1350F3F4,
-        0xC79A971F, 0x35F1141C, 0x26A1E7E8, 0xD4CA64EB,
-        0x8AD958CF, 0x78B2DBCC, 0x6BE22838, 0x9989AB3B,
-        0x4D43CFD0, 0xBF284CD3, 0xAC78BF27, 0x5E133C24,
-        0x105EC76F, 0xE235446C, 0xF165B798, 0x030E349B,
-        0xD7C45070, 0x25AFD373, 0x36FF2087, 0xC494A384,
-        0x9A879FA0, 0x68EC1CA3, 0x7BBCEF57, 0x89D76C54,
-        0x5D1D08BF, 0xAF768BBC, 0xBC267848, 0x4E4DFB4B,
-        0x20BD8EDE, 0xD2D60DDD, 0xC186FE29, 0x33ED7D2A,
-        0xE72719C1, 0x154C9AC2, 0x061C6936, 0xF477EA35,
-        0xAA64D611, 0x580F5512, 0x4B5FA6E6, 0xB93425E5,
-        0x6DFE410E, 0x9F95C20D, 0x8CC531F9, 0x7EAEB2FA,
-        0x30E349B1, 0xC288CAB2, 0xD1D83946, 0x23B3BA45,
-        0xF779DEAE, 0x05125DAD, 0x1642AE59, 0xE4292D5A,
-        0xBA3A117E, 0x4851927D, 0x5B016189, 0xA96AE28A,
-        0x7DA08661, 0x8FCB0562, 0x9C9BF696, 0x6EF07595,
-        0x417B1DBC, 0xB3109EBF, 0xA0406D4B, 0x522BEE48,
-        0x86E18AA3, 0x748A09A0, 0x67DAFA54, 0x95B17957,
-        0xCBA24573, 0x39C9C670, 0x2A993584, 0xD8F2B687,
-        0x0C38D26C, 0xFE53516F, 0xED03A29B, 0x1F682198,
-        0x5125DAD3, 0xA34E59D0, 0xB01EAA24, 0x42752927,
-        0x96BF4DCC, 0x64D4CECF, 0x77843D3B, 0x85EFBE38,
-        0xDBFC821C, 0x2997011F, 0x3AC7F2EB, 0xC8AC71E8,
-        0x1C661503, 0xEE0D9600, 0xFD5D65F4, 0x0F36E6F7,
-        0x61C69362, 0x93AD1061, 0x80FDE395, 0x72966096,
-        0xA65C047D, 0x5437877E, 0x4767748A, 0xB50CF789,
-        0xEB1FCBAD, 0x197448AE, 0x0A24BB5A, 0xF84F3859,
-        0x2C855CB2, 0xDEEEDFB1, 0xCDBE2C45, 0x3FD5AF46,
-        0x7198540D, 0x83F3D70E, 0x90A324FA, 0x62C8A7F9,
-        0xB602C312, 0x44694011, 0x5739B3E5, 0xA55230E6,
-        0xFB410CC2, 0x092A8FC1, 0x1A7A7C35, 0xE811FF36,
-        0x3CDB9BDD, 0xCEB018DE, 0xDDE0EB2A, 0x2F8B6829,
-        0x82F63B78, 0x709DB87B, 0x63CD4B8F, 0x91A6C88C,
-        0x456CAC67, 0xB7072F64, 0xA457DC90, 0x563C5F93,
-        0x082F63B7, 0xFA44E0B4, 0xE9141340, 0x1B7F9043,
-        0xCFB5F4A8, 0x3DDE77AB, 0x2E8E845F, 0xDCE5075C,
-        0x92A8FC17, 0x60C37F14, 0x73938CE0, 0x81F80FE3,
-        0x55326B08, 0xA759E80B, 0xB4091BFF, 0x466298FC,
-        0x1871A4D8, 0xEA1A27DB, 0xF94AD42F, 0x0B21572C,
-        0xDFEB33C7, 0x2D80B0C4, 0x3ED04330, 0xCCBBC033,
-        0xA24BB5A6, 0x502036A5, 0x4370C551, 0xB11B4652,
-        0x65D122B9, 0x97BAA1BA, 0x84EA524E, 0x7681D14D,
-        0x2892ED69, 0xDAF96E6A, 0xC9A99D9E, 0x3BC21E9D,
-        0xEF087A76, 0x1D63F975, 0x0E330A81, 0xFC588982,
-        0xB21572C9, 0x407EF1CA, 0x532E023E, 0xA145813D,
-        0x758FE5D6, 0x87E466D5, 0x94B49521, 0x66DF1622,
-        0x38CC2A06, 0xCAA7A905, 0xD9F75AF1, 0x2B9CD9F2,
-        0xFF56BD19, 0x0D3D3E1A, 0x1E6DCDEE, 0xEC064EED,
-        0xC38D26C4, 0x31E6A5C7, 0x22B65633, 0xD0DDD530,
-        0x0417B1DB, 0xF67C32D8, 0xE52CC12C, 0x1747422F,
-        0x49547E0B, 0xBB3FFD08, 0xA86F0EFC, 0x5A048DFF,
-        0x8ECEE914, 0x7CA56A17, 0x6FF599E3, 0x9D9E1AE0,
-        0xD3D3E1AB, 0x21B862A8, 0x32E8915C, 0xC083125F,
-        0x144976B4, 0xE622F5B7, 0xF5720643, 0x07198540,
-        0x590AB964, 0xAB613A67, 0xB831C993, 0x4A5A4A90,
-        0x9E902E7B, 0x6CFBAD78, 0x7FAB5E8C, 0x8DC0DD8F,
-        0xE330A81A, 0x115B2B19, 0x020BD8ED, 0xF0605BEE,
-        0x24AA3F05, 0xD6C1BC06, 0xC5914FF2, 0x37FACCF1,
-        0x69E9F0D5, 0x9B8273D6, 0x88D28022, 0x7AB90321,
-        0xAE7367CA, 0x5C18E4C9, 0x4F48173D, 0xBD23943E,
-        0xF36E6F75, 0x0105EC76, 0x12551F82, 0xE03E9C81,
-        0x34F4F86A, 0xC69F7B69, 0xD5CF889D, 0x27A40B9E,
-        0x79B737BA, 0x8BDCB4B9, 0x988C474D, 0x6AE7C44E,
-        0xBE2DA0A5, 0x4C4623A6, 0x5F16D052, 0xAD7D5351,
-    ]
-
-    def masked_crc32c(self, buf: bytes) -> int:
-        crc = 0xffffffff
-        for c in buf:
-            crc = (crc >> 8) ^ self.crc32c_table[(crc ^ c) & 0xFF]
-        crc = (~crc) & 0xffffffff
-        # reverse endianness
-        crc = struct.unpack(">I", struct.pack("<I", crc))[0]
-        return (((crc >> 15) | (crc << 17)) + 0xa282ead8) & 0xffffffff
-
-    def decompress(self, source_data: bytes) -> io.BytesIO:
-        offset = 0
-        data = io.BytesIO()
-        while offset < len(source_data):
-            header_structure = "<IIQQQ"
-            header_size = struct.calcsize(header_structure)
-            header_data = source_data[offset:offset + header_size]
-            magic, version, start, end, padding = struct.unpack(header_structure, header_data)
-            print(magic, version, start, end, padding)
-            if magic not in [0x4c4d5641]:
-                raise RuntimeError("File not in AVML or LiME format")
-            chunk_data = source_data[offset + header_size: offset + header_size + (end - start)]
-            chunk, consumed = self.read_snappy_data(chunk_data, end - start)
-            data.seek(start)
-            data.write(chunk)
-            # TODO: Check whatever the remaining 8 bytes are
-            offset += header_size + consumed + 8
-        data.seek(0)
-        return data
-
-    def read_snappy_data(self, data: bytes, limit: int) -> Tuple[bytes, int]:
-        """Decompresses data up to the size limit provided
-
-        Args:
-            data: Input data
-            limit: The maximum size of decompressed data
-
-        Returns:
-            Tuple of decompressed data, and number of compressed bytes consumed
-        """
-        decompressed = bytearray()
-        offset = 0
-        crc_len = 4
-        chunk_header_struct = '<L'
-        chunk_header_len = struct.calcsize(chunk_header_struct)
-        while len(decompressed) <= limit:
-            if offset + chunk_header_len < len(data):
-                chunk_header = data[offset:offset + chunk_header_len]
-                chunk_header_val = struct.unpack('<L', chunk_header)[0]
-                chunk_type, chunk_size = chunk_header_val & 0xff, chunk_header_val >> 8
-                if chunk_type == 0xff:
-                    if data[offset + chunk_header_len:offset + chunk_header_len + chunk_size] != b'sNaPpY':
-                        raise ValueError(f"Snappy header missing at offset: {offset}")
-                elif chunk_type in [0x00, 0x01]:
-                    # CRC + (Un)compressed data
-                    start = offset + chunk_header_len
-                    chunk_crc = data[start: start + crc_len]
-                    chunk_data = data[start + crc_len: start + chunk_size]
-                    if chunk_type == 0x00:
-                        # Compressed data
-                        chunk_data = snappy.decompress(chunk_data)
-                    # TODO: Verify CRC
-                    decompressed.extend(chunk_data)
-                elif chunk_type in range(0x2, 0x80):
-                    # Unskippable
-                    raise ValueError(f"Unskippable chunk of type {chunk_type} found: {offset}")
-                offset += chunk_header_len + chunk_size
-        return decompressed, offset
-
-
 class AVMLLayer(segmented.NonLinearlySegmentedLayer):
     """A Lime format TranslationLayer.
 
@@ -176,6 +36,8 @@ class AVMLLayer(segmented.NonLinearlySegmentedLayer):
                                        layer.read(layer.minimum_address, struct.calcsize(header_structure)))
         if magic not in [0x4c4d5641] or version != 2:
             raise exceptions.LayerException("File not completely in AVML format")
+        if not HAS_SNAPPY:
+            vollog.warning('AVML file detected, but snappy python library not installed')
 
     def _load_segments(self) -> None:
         base_layer = self.context.layers[self._base_layer]
@@ -270,13 +132,3 @@ class AVMLStacker(interfaces.automagic.StackerLayerInterface):
         new_name = context.layers.free_layer_name("AVMLLayer")
         context.config[interfaces.configuration.path_join(new_name, "base_layer")] = layer_name
         return AVMLLayer(context, new_name, new_name)
-
-
-if __name__ == '__main__':
-    import sys
-
-    source_data = open(sys.argv[1], 'br').read()
-
-    sf = SnappyFraming()
-    with open('outputfile', 'wb') as fp:
-        fp.write(sf.decompress(source_data).read())