file-zip: decode local file header

1 files changed, 104 insertions, 1 deletions

diff --git a/lua/file-zip.lua b/lua/file-zip.lua
index aec8ac0..3a8c465 100644
--- a/lua/file-zip.lua
+++ b/lua/file-zip.lua
@@ -1,19 +1,122 @@
 --
 -- Zip Archive dissector
 -- Author: Peter Wu <peter@lekensteyn.nl>
+--
+-- Spec: https://en.wikipedia.org/wiki/Zip_(file_format)#File_headers
+--
 
 --
 -- Dissection of Zip file contents
 --
 
+-- takes a table where keys are the field names and values are descriptions of
+-- fields. If a value is a table without numeric indicdes, assume that it is a
+-- nested tree.
+local function make_fields(field_abbr_prefix, field_defs, hfs_out, hfs_list_out)
+    for name, params in pairs(field_defs) do
+        if #params == 0 then
+            -- Assume nested table, flatten it
+            hfs_out[name] = {}
+            make_fields(field_abbr_prefix .. name .. ".", params,
+                hfs_out[name], hfs_list_out)
+        else
+            local proto_field_constructor = params[1]
+            local field_abbr = field_abbr_prefix .. name
+            local field
+            if type(params[2]) == "string" then
+                -- Name was given, use it
+                field = proto_field_constructor(field_abbr, unpack(params, 2))
+            else
+                -- Name was not given, use field name (the suffix)
+                field = proto_field_constructor(field_abbr, name, unpack(params, 2))
+            end
+            hfs_out[name] = field
+            table.insert(hfs_list_out, field)
+        end
+    end
+end
+
 local proto_zip = Proto.new("zip_archive", "Zip Archive")
+local hf = {}
+make_fields("zip_archive", {
+    signature = {ProtoField.uint32, base.HEX},
+    entry = {
+        _ = {ProtoField.none, "File entry"},
+        version         = {ProtoField.uint16, base.DEC},
+        flag            = {ProtoField.uint16, base.HEX},
+        comp_method     = {ProtoField.uint16, base.HEX},
+        mod_time        = {ProtoField.uint16, base.HEX},
+        mod_date        = {ProtoField.uint16, base.HEX},
+        crc32           = {ProtoField.uint32, base.HEX},
+        size_comp       = {ProtoField.uint32, base.DEC},
+        size_uncomp     = {ProtoField.uint32, base.DEC},
+        filename_len    = {ProtoField.uint16, base.DEC},
+        extra_len       = {ProtoField.uint16, base.DEC},
+        filename        = {ProtoField.string},
+        extra           = {ProtoField.bytes},
+        data            = {ProtoField.bytes},
+    },
+    cd = {
+        _ = {ProtoField.none, "Central Directory Record"}
+    },
+}, hf, proto_zip.fields)
+
+local function dissect_entry(tvb, pinfo, tree)
+end
+
+local function dissect_one(tvb, offset, pinfo, tree)
+    local orig_offset = offset
+    local magic = tvb(offset, 4):le_int()
+    if magic == 0x04034b50 then -- File entry
+        local subtree = tree:add_le(hf.entry._, tvb(offset, 30))
+        -- header
+        subtree:add_le(hf.signature,            tvb(offset, 4))
+        subtree:add_le(hf.entry.version,        tvb(offset + 4, 2))
+        subtree:add_le(hf.entry.flag,           tvb(offset + 6, 2))
+        subtree:add_le(hf.entry.comp_method,    tvb(offset + 8, 2))
+        subtree:add_le(hf.entry.mod_time,       tvb(offset + 10, 2))
+        subtree:add_le(hf.entry.mod_date,       tvb(offset + 12, 2))
+        subtree:add_le(hf.entry.crc32,          tvb(offset + 14, 4))
+        subtree:add_le(hf.entry.size_comp,      tvb(offset + 18, 4))
+        subtree:add_le(hf.entry.size_uncomp,    tvb(offset + 22, 4))
+        subtree:add_le(hf.entry.filename_len,   tvb(offset + 26, 2))
+        subtree:add_le(hf.entry.extra_len,      tvb(offset + 28, 2))
+        local data_len = tvb(offset + 18, 2):le_uint()
+        local filename_len = tvb(offset + 26, 2):le_uint()
+        local extra_len = tvb(offset + 28, 2):le_uint()
+
+        -- skip header
+        offset = offset + 30
+        subtree:add(hf.entry.filename,          tvb(offset, filename_len))
+        subtree:append_text(": " .. tvb(offset, filename_len):string())
+        offset = offset + filename_len
+        subtree:add(hf.entry.extra,             tvb(offset, extra_len))
+        offset = offset + extra_len
+        subtree:add(hf.entry.data,              tvb(offset, data_len))
+        offset = offset + data_len
+
+        subtree:set_len(offset - orig_offset)
+        return offset
+    elseif magic == 0x02014b50 then -- Central Directory
+        local subtree = tree:add_le(hf.cd._,    tvb(offset, 30))
+    elseif tvb:raw(offset, 2) == "PK" then
+        -- Unknown signature
+        tree:add_le(hf.signature, tvb(offset, 4))
+    end
+end
 
 function proto_zip.dissector(tvb, pinfo, tree)
     pinfo.cols.protocol = "zip"
     --pinfo.cols.info = ""
+
+    local next_offset = 0
+    while next_offset do
+        next_offset = dissect_one(tvb, next_offset, pinfo, tree)
+    end
+    return next_offset
 end
 
-function zip_heur(tvb, pinfo, tree)
+local function zip_heur(tvb, pinfo, tree)
     if tvb:raw(0, 2) ~= "PK" then
         return false
     end