Add a partial decoder for VDI

1 files changed, 88 insertions, 0 deletions

diff --git a/plugins/vdi.lua b/plugins/vdi.lua
new file mode 100644
index 0000000..75bfd78
--- /dev/null
+++ b/plugins/vdi.lua
@@ -0,0 +1,88 @@
+--
+-- vdi.lua: VirtualBox Disk Image
+--
+-- Copyright (c) 2017, Přemysl Janouch <p.janouch@gmail.com>
+--
+-- Permission to use, copy, modify, and/or distribute this software for any
+-- purpose with or without fee is hereby granted, provided that the above
+-- copyright notice and this permission notice appear in all copies.
+--
+-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+-- WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+-- MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+-- SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+-- WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+-- OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+-- CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+--
+
+local detect = function (c)
+	c.position = 65
+	return c:read (4) == "\x7F\x10\xDA\xBE"
+end
+
+-- As described by https://forums.virtualbox.org/viewtopic.php?t=8046
+local decode = function (c)
+	if not detect (c ()) then error ("not a VDI file") end
+	c.endianity = "le"
+
+	-- The header is preceded by an arbitrary string
+	c.position = 65
+	local signature = c:u32 ("image signature")
+
+	local p, vmajor, vminor = c.position, c:u16 (), c:u16 ()
+	c (p, c.position - 1):mark ("VDI version: %d.%d", vmajor, vminor)
+
+	local size = c:u32 ("size of header: %d")
+	c (64 + 1, 64 + size):mark ("VDI header")
+
+	local type = c:u32 ("image type: %s", function (u32)
+		if u32 == 1 then return "dynamic" end
+		if u32 == 2 then return "static" end
+		return "unknown: %d", u32
+	end)
+	local flags = c:u32 ("image flags: %#x")
+
+	local p, desc = c.position, c:read (256)
+	c (p, c.position - 1):mark ("image description: %s", desc:match ("%C+"))
+
+	local offset_blocks = c:u32 ("offset to blocks: %#x")
+	local offset_data = c:u32 ("offset to data: %#x")
+	local n_cylinders = c:u32 ("#cylinders: %d")
+	local n_heads = c:u32 ("#heads: %d")
+	local n_sectors = c:u32 ("#sectors: %d")
+	local sector_size = c:u32 ("sector size: %d")
+	local unused = c:read (4)
+	local disk_size = c:u64 ("disk size: %d bytes")
+	local block_size = c:u32 ("block size: %d")
+	-- TODO: we should probably count that in -> is it in "blocks" or "data"?
+	local block_extra_data = c:u32 ("block extra data: %d")
+	local n_blocks = c:u32 ("#blocks in HDD: %d")
+	local n_blocks_allocated = c:u32 ("#blocks allocated: %d")
+
+	local function read_uuid4 (c, name)
+		local p, uuid = c.position, c:read (16)
+		local b = table.pack (uuid:byte (1, #uuid))
+		c (p, c.position - 1):mark ("%s: %02x%02x%02x%02x-"
+			.. "%02x%02x-%02x%02x-%02x%02x-"
+			.. "%02x%02x%02x%02x%02x%02x", name,
+			b[1], b[2], b[3], b[4],
+			b[5], b[6], b[7], b[8], b[9], b[10],
+			b[11], b[12], b[13], b[14], b[15], b[16])
+		return uuid
+	end
+
+	local uuid_vdi = read_uuid4 (c, "UUID of VDI")
+	local uuid_last_snap = read_uuid4 (c, "UUID of last snapshot")
+	local uuid_link = read_uuid4 (c, "UUID of link")
+	local uuid_parent = read_uuid4 (c, "UUID of parent")
+
+	-- TODO: perhaps this should be more granular and identify all blocks
+	c (offset_blocks + 1, offset_blocks + 4 * n_blocks)
+		:mark ("VDI blocks")
+	c (offset_data + 1, offset_data + block_size * n_blocks_allocated)
+		:mark ("VDI data")
+end
+
+hex.register { type="vdi", detect=detect, decode=decode }
+