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|
--[[
Copyright (c) 2019, Vsevolod Stakhov <vsevolod@highsecure.ru>
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
]]--
--[[[
-- @module lua_content/pdf
-- This module contains some heuristics for PDF files
--]]
local rspamd_trie = require "rspamd_trie"
local rspamd_util = require "rspamd_util"
local rspamd_text = require "rspamd_text"
local rspamd_url = require "rspamd_url"
local rspamd_logger = require "rspamd_logger"
local bit = require "bit"
local N = "lua_content"
local lua_util = require "lua_util"
local rspamd_regexp = require "rspamd_regexp"
local lpeg = require "lpeg"
local pdf_patterns = {
trailer = {
patterns = {
[[\ntrailer\r?\n]]
}
},
suspicious = {
patterns = {
[[netsh\s]],
[[echo\s]],
[[\/[A-Za-z]*#\d\d(?:[#A-Za-z<>/\s])]], -- Hex encode obfuscation
}
},
start_object = {
patterns = {
[=[[\r\n\0]\s*\d+\s+\d+\s+obj[\s<]]=]
}
},
end_object = {
patterns = {
[=[endobj[\r\n]]=]
}
},
start_stream = {
patterns = {
[=[>\s*stream[\r\n]]=],
}
},
end_stream = {
patterns = {
[=[endstream[\r\n]]=]
}
}
}
local pdf_text_patterns = {
start = {
patterns = {
[[\sBT\s]]
}
},
stop = {
patterns = {
[[\sET\b]]
}
}
}
local pdf_cmap_patterns = {
start = {
patterns = {
[[\d\s+beginbfchar\s]],
[[\d\s+beginbfrange\s]]
}
},
stop = {
patterns = {
[[\sendbfrange\b]],
[[\sendbchar\b]]
}
}
}
-- index[n] ->
-- t[1] - pattern,
-- t[2] - key in patterns table,
-- t[3] - value in patterns table
-- t[4] - local pattern index
local pdf_indexes = {}
local pdf_text_indexes = {}
local pdf_cmap_indexes = {}
local pdf_trie
local pdf_text_trie
local pdf_cmap_trie
local exports = {}
local config = {
max_extraction_size = 512 * 1024,
max_processing_size = 32 * 1024,
text_extraction = false, -- NYI feature
url_extraction = true,
enabled = true,
js_fuzzy = true, -- Generate fuzzy hashes from PDF javascripts
min_js_fuzzy = 32, -- Minimum size of js to be considered as a fuzzy
openaction_fuzzy_only = false, -- Generate fuzzy from all scripts
}
-- Used to process patterns found in PDF
-- positions for functional processors should be a iter/table from trie matcher in form
---- [{n1, pat_idx1}, ... {nn, pat_idxn}] where
---- pat_idxn is pattern index and n1 ... nn are match positions
local processors = {}
-- PDF objects outer grammar in LPEG style (performing table captures)
local pdf_outer_grammar
local pdf_text_grammar
-- Used to match objects
local object_re = rspamd_regexp.create_cached([=[/(\d+)\s+(\d+)\s+obj\s*/]=])
local function config_module()
local opts = rspamd_config:get_all_opt('lua_content')
if opts and opts.pdf then
config = lua_util.override_defaults(config, opts.pdf)
end
end
local function compile_tries()
local default_compile_flags = bit.bor(rspamd_trie.flags.re,
rspamd_trie.flags.dot_all,
rspamd_trie.flags.no_start)
local function compile_pats(patterns, indexes, compile_flags)
local strs = {}
for what,data in pairs(patterns) do
for i,pat in ipairs(data.patterns) do
strs[#strs + 1] = pat
indexes[#indexes + 1] = {what, data, pat, i}
end
end
return rspamd_trie.create(strs, compile_flags or default_compile_flags)
end
if not pdf_trie then
pdf_trie = compile_pats(pdf_patterns, pdf_indexes)
end
if not pdf_text_trie then
pdf_text_trie = compile_pats(pdf_text_patterns, pdf_text_indexes)
end
if not pdf_cmap_trie then
pdf_cmap_trie = compile_pats(pdf_cmap_patterns, pdf_cmap_indexes)
end
end
-- Returns a table with generic grammar elements for PDF
local function generic_grammar_elts()
local P = lpeg.P
local R = lpeg.R
local S = lpeg.S
local V = lpeg.V
local C = lpeg.C
local D = R'09' -- Digits
local grammar_elts = {}
-- Helper functions
local function pdf_hexstring_unescape(s)
local function ue(cc)
return string.char(tonumber(cc, 16))
end
if #s % 2 == 0 then
-- Sane hex string
return s:gsub('..', ue)
end
-- WTF hex string
-- Append '0' to it and unescape...
return s:sub(1, #s - 1):gsub('..' , ue) .. (s:sub(#s) .. '0'):gsub('..' , ue)
end
local function pdf_string_unescape(s)
local function ue_single(cc)
if cc == '\\r' then
return '\r'
elseif cc == '\\n' then
return '\n'
else
return cc:gsub(2, 2)
end
end
-- simple unescape \char
s = s:gsub('\\[^%d]', ue_single)
-- unescape octal
local function ue_octal(cc)
-- Replace unknown stuff with '?'
return string.char(tonumber(cc:sub(2), 8) or 63)
end
s = s:gsub('\\%d%d?%d?', ue_octal)
return s
end
local function pdf_id_unescape(s)
return (s:gsub('#%d%d', function (cc)
return string.char(tonumber(cc:sub(2), 16))
end))
end
local delim = S'()<>[]{}/%'
grammar_elts.ws = S'\0 \r\n\t\f'
local hex = R'af' + R'AF' + D
-- Comments.
local eol = P'\r\n' + '\n'
local line = (1 - S'\r\n\f')^0 * eol^-1
grammar_elts.comment = P'%' * line
-- Numbers.
local sign = S'+-'^-1
local decimal = D^1
local float = D^1 * P'.' * D^0 + P'.' * D^1
grammar_elts.number = C(sign * (float + decimal)) / tonumber
-- String
grammar_elts.str = P{ "(" * C(((1 - S"()\\") + (P '\\' * 1) + V(1))^0) / pdf_string_unescape * ")" }
grammar_elts.hexstr = P{"<" * C(hex^0) / pdf_hexstring_unescape * ">"}
-- Identifier
grammar_elts.id = P{'/' * C((1-(delim + grammar_elts.ws))^1) / pdf_id_unescape}
-- Booleans (who care about them?)
grammar_elts.boolean = C(P("true") + P("false"))
-- Stupid references
grammar_elts.ref = lpeg.Ct{lpeg.Cc("%REF%") * C(D^1) * " " * C(D^1) * " " * "R"}
return grammar_elts
end
-- Generates a grammar to parse outer elements (external objects in PDF notation)
local function gen_outer_grammar()
local V = lpeg.V
local gen = generic_grammar_elts()
return lpeg.P{
"EXPR";
EXPR = gen.ws^0 * V("ELT")^0 * gen.ws^0,
ELT = V("ARRAY") + V("DICT") + V("ATOM"),
ATOM = gen.ws^0 * (gen.comment + gen.boolean + gen.ref +
gen.number + V("STRING") + gen.id) * gen.ws^0,
DICT = "<<" * gen.ws^0 * lpeg.Cf(lpeg.Ct("") * V("KV_PAIR")^0, rawset) * gen.ws^0 * ">>",
KV_PAIR = lpeg.Cg(gen.id * gen.ws^0 * V("ELT") * gen.ws^0),
ARRAY = "[" * gen.ws^0 * lpeg.Ct(V("ELT")^0) * gen.ws^0 * "]",
STRING = lpeg.P{gen.str + gen.hexstr},
}
end
-- Graphic state in PDF
local function gen_graphics_unary()
local P = lpeg.P
local S = lpeg.S
return P("q") + P("Q") + P("h")
+ S("WSsFfBb") * P("*")^0 + P("n")
end
local function gen_graphics_binary()
local P = lpeg.P
local S = lpeg.S
return S("gGwJjMi") +
P("M") + P("ri") + P("gs") +
P("CS") + P("cs") + P("sh")
end
local function gen_graphics_ternary()
local P = lpeg.P
local S = lpeg.S
return P("d") + P("m") + S("lm")
end
local function gen_graphics_nary()
local P = lpeg.P
local S = lpeg.S
return P("SC") + P("sc") + P("SCN") + P("scn") + P("k") + P("K") + P("re") + S("cvy") +
P("RG") + P("rg")
end
-- Generates a grammar to parse text blocks (between BT and ET)
local function gen_text_grammar()
local V = lpeg.V
local P = lpeg.P
local C = lpeg.C
local gen = generic_grammar_elts()
local empty = ""
local unary_ops = C("T*") / "\n" +
C(gen_graphics_unary()) / empty
local binary_ops = P("Tc") + P("Tw") + P("Tz") + P("TL") + P("Tr") + P("Ts") +
gen_graphics_binary()
local ternary_ops = P("TD") + P("Td") + gen_graphics_ternary()
local nary_op = P("Tm") + gen_graphics_nary()
local text_binary_op = P("Tj") + P("TJ") + P("'")
local text_quote_op = P('"')
local font_op = P("Tf")
return lpeg.P{
"EXPR";
EXPR = gen.ws^0 * lpeg.Ct(V("COMMAND")^0),
COMMAND = (V("UNARY") + V("BINARY") + V("TERNARY") + V("NARY") + V("TEXT") +
V("FONT") + gen.comment) * gen.ws^0,
UNARY = unary_ops,
BINARY = V("ARG") / empty * gen.ws^1 * binary_ops,
TERNARY = V("ARG") / empty * gen.ws^1 * V("ARG") / empty * gen.ws^1 * ternary_ops,
NARY = (gen.number / 0 * gen.ws^1)^1 * (gen.id / empty * gen.ws^0)^-1 * nary_op,
ARG = V("ARRAY") + V("DICT") + V("ATOM"),
ATOM = (gen.comment + gen.boolean + gen.ref +
gen.number + V("STRING") + gen.id),
DICT = "<<" * gen.ws^0 * lpeg.Cf(lpeg.Ct("") * V("KV_PAIR")^0, rawset) * gen.ws^0 * ">>",
KV_PAIR = lpeg.Cg(gen.id * gen.ws^0 * V("ARG") * gen.ws^0),
ARRAY = "[" * gen.ws^0 * lpeg.Ct(V("ARG")^0) * gen.ws^0 * "]",
STRING = lpeg.P{gen.str + gen.hexstr},
TEXT = (V("TEXT_ARG") * gen.ws^1 * text_binary_op) +
(V("ARG") / 0 * gen.ws^1 * V("ARG") / 0 * gen.ws^1 * V("TEXT_ARG") * gen.ws^1 * text_quote_op),
FONT = (V("FONT_ARG") * gen.ws^1 * (gen.number / 0) * gen.ws^1 * font_op),
FONT_ARG = lpeg.Ct(lpeg.Cc("%font%") * gen.id),
TEXT_ARG = lpeg.Ct(V("STRING")) + V("TEXT_ARRAY"),
TEXT_ARRAY = "[" *
lpeg.Ct(((gen.ws^0 * (gen.ws^0 * (gen.number / 0)^0 * gen.ws^0 * (gen.str + gen.hexstr)))^1)) * gen.ws^0 * "]",
}
end
-- Call immediately on require
compile_tries()
config_module()
pdf_outer_grammar = gen_outer_grammar()
pdf_text_grammar = gen_text_grammar()
local function extract_text_data(specific)
return nil -- NYI
end
-- Generates index for major/minor pair
local function obj_ref(major, minor)
return major * 10.0 + 1.0 / (minor + 1.0)
end
-- Return indirect object reference (if needed)
local function maybe_dereference_object(elt, pdf, task)
if type(elt) == 'table' and elt[1] == '%REF%' then
local ref = obj_ref(elt[2], elt[3])
if pdf.ref[ref] then
-- No recursion!
return pdf.ref[ref]
else
lua_util.debugm(N, task, 'cannot dereference %s:%s -> %s',
elt[2], elt[3], obj_ref(elt[2], elt[3]))
return nil
end
end
return elt
end
-- Apply PDF stream filter
local function apply_pdf_filter(input, filt)
if filt == 'FlateDecode' then
return rspamd_util.inflate(input, config.max_extraction_size)
end
return nil
end
-- Conditionally apply a pipeline of stream filters and return uncompressed data
local function maybe_apply_filter(dict, data)
local uncompressed = data
if dict.Filter then
local filt = dict.Filter
if type(filt) == 'string' then
filt = {filt}
end
for _,f in ipairs(filt) do
uncompressed = apply_pdf_filter(uncompressed, f)
if not uncompressed then break end
end
end
return uncompressed
end
-- Conditionally extract stream data from object and attach it as obj.uncompressed
local function maybe_extract_object_stream(obj, pdf, task)
if pdf.encrypted then
-- TODO add decryption some day
return nil
end
local dict = obj.dict
if dict.Length then
local len = math.min(obj.stream.len,
tonumber(maybe_dereference_object(dict.Length, pdf, task)) or 0)
local real_stream = obj.stream.data:span(1, len)
local uncompressed = maybe_apply_filter(dict, real_stream)
if uncompressed then
obj.uncompressed = uncompressed
lua_util.debugm(N, task, 'extracted object %s:%s: (%s -> %s)',
obj.major, obj.minor, len, uncompressed:len())
return obj.uncompressed
else
lua_util.debugm(N, task, 'cannot extract object %s:%s; len = %s; filter = %s',
obj.major, obj.minor, len, dict.Filter)
end
end
end
local function parse_object_grammar(obj, task, pdf)
-- Parse grammar
local obj_dict_span
if obj.stream then
obj_dict_span = obj.data:span(1, obj.stream.start - obj.start)
else
obj_dict_span = obj.data
end
if obj_dict_span:len() < config.max_processing_size then
local ret,obj_or_err = pcall(pdf_outer_grammar.match, pdf_outer_grammar, obj_dict_span)
if ret then
if obj.stream then
obj.dict = obj_or_err
lua_util.debugm(N, task, 'stream object %s:%s is parsed to: %s',
obj.major, obj.minor, obj_or_err)
else
-- Direct object
if type(obj_or_err) == 'table' then
obj.dict = obj_or_err
obj.uncompressed = obj_or_err
lua_util.debugm(N, task, 'direct object %s:%s is parsed to: %s',
obj.major, obj.minor, obj_or_err)
pdf.ref[obj_ref(obj.major, obj.minor)] = obj
else
pdf.ref[obj_ref(obj.major, obj.minor)] = obj_or_err
obj.dict = {}
obj.uncompressed = obj_or_err
end
end
else
lua_util.debugm(N, task, 'object %s:%s cannot be parsed: %s',
obj.major, obj.minor, obj_or_err)
end
else
lua_util.debugm(N, task, 'object %s:%s cannot be parsed: too large %s',
obj.major, obj.minor, obj_dict_span:len())
end
end
-- Extracts font data and process /ToUnicode mappings
-- NYI in fact as cmap is ridiculously stupid and complicated
local function process_font(task, pdf, font, fname)
local dict = font
if font.dict then
dict = font.dict
end
if type(dict) == 'table' and dict.ToUnicode then
local cmap = maybe_dereference_object(dict.ToUnicode, pdf, task)
if cmap and cmap.dict then
maybe_extract_object_stream(cmap, pdf, task)
lua_util.debugm(N, task, 'found cmap for font %s: %s',
fname, cmap.uncompressed)
end
end
end
-- Forward declaration
local process_dict
-- This function processes javascript string and returns JS hash and JS rspamd_text
local function process_javascript(task, pdf, js)
local rspamd_cryptobox_hash = require "rspamd_cryptobox_hash"
if type(js) == 'string' then
js = rspamd_text.fromstring(js):oneline()
elseif type(js) == 'userdata' then
js = js:oneline()
else
return nil
end
local hash = rspamd_cryptobox_hash.create(js)
local bin_hash = hash:bin()
if not pdf.scripts then
pdf.scripts = {}
end
if pdf.scripts[bin_hash] then
-- Duplicate
return pdf.scripts[bin_hash]
end
local njs = {
data = js,
hash = rspamd_util.encode_base32(bin_hash),
bin_hash = bin_hash,
}
pdf.scripts[bin_hash] = njs
return njs
end
-- Extract interesting stuff from /Action, e.g. javascript
local function process_action(task, pdf, obj)
if not (obj.js or obj.launch) and (obj.dict and obj.dict.JS) then
local js = maybe_dereference_object(obj.dict.JS, pdf, task)
if js then
if type(js) == 'table' then
local extracted_js = maybe_extract_object_stream(js, pdf, task)
if not extracted_js then
lua_util.debugm(N, task, 'invalid type for javascript from %s:%s: %s',
obj.major, obj.minor, js)
else
js = extracted_js
end
end
js = process_javascript(task, pdf, js)
if js then
obj.js = js
lua_util.debugm(N, task, 'extracted javascript from %s:%s: %s',
obj.major, obj.minor, obj.js.data)
else
lua_util.debugm(N, task, 'invalid type for javascript from %s:%s: %s',
obj.major, obj.minor, js)
end
elseif obj.dict.F then
local launch = maybe_dereference_object(obj.dict.F, pdf, task)
if launch then
if type(launch) == 'string' then
obj.launch = rspamd_text.fromstring(launch):exclude_chars('%n%c')
lua_util.debugm(N, task, 'extracted launch from %s:%s: %s',
obj.major, obj.minor, obj.launch)
elseif type(launch) == 'userdata' then
obj.launch = launch:exclude_chars('%n%c')
lua_util.debugm(N, task, 'extracted launch from %s:%s: %s',
obj.major, obj.minor, obj.launch)
else
lua_util.debugm(N, task, 'invalid type for launch from %s:%s: %s',
obj.major, obj.minor, launch)
end
end
else
lua_util.debugm(N, task, 'no JS attribute in action %s:%s',
obj.major, obj.minor)
end
end
end
-- Extract interesting stuff from /Catalog, e.g. javascript in /OpenAction
local function process_catalog(task, pdf, obj)
if obj.dict then
if obj.dict.OpenAction then
local action = maybe_dereference_object(obj.dict.OpenAction, pdf, task)
if action and type(action) == 'table' then
-- This also processes action js (if not already processed)
process_dict(task, pdf, action, action.dict)
if action.js then
lua_util.debugm(N, task, 'found openaction JS in %s:%s: %s',
obj.major, obj.minor, action.js)
pdf.openaction = action.js
elseif action.launch then
lua_util.debugm(N, task, 'found openaction launch in %s:%s: %s',
obj.major, obj.minor, action.launch)
pdf.launch = action.launch
else
lua_util.debugm(N, task, 'no JS in openaction %s:%s: %s',
obj.major, obj.minor, action)
end
else
lua_util.debugm(N, task, 'cannot find openaction %s:%s: %s -> %s',
obj.major, obj.minor, obj.dict.OpenAction, action)
end
else
lua_util.debugm(N, task, 'no openaction in catalog %s:%s',
obj.major, obj.minor)
end
end
end
local function process_xref(task, pdf, obj)
if obj.dict then
if obj.dict.Encrypt then
local encrypt = maybe_dereference_object(obj.dict.Encrypt, pdf, task)
lua_util.debugm(N, task, 'found encrypt: %s in xref object %s:%s',
encrypt, obj.major, obj.minor)
pdf.encrypted = true
end
end
end
process_dict = function(task, pdf, obj, dict)
if not obj.type and type(dict) == 'table' then
if dict.Type and type(dict.Type) == 'string' then
-- Common stuff
obj.type = dict.Type
end
if not obj.type then
if obj.dict.S and obj.dict.JS then
obj.type = 'Javascript'
lua_util.debugm(N, task, 'implicit type for Javascript object %s:%s',
obj.major, obj.minor)
else
lua_util.debugm(N, task, 'no type for %s:%s',
obj.major, obj.minor)
return
end
end
lua_util.debugm(N, task, 'processed stream dictionary for object %s:%s -> %s',
obj.major, obj.minor, obj.type)
local contents = dict.Contents
if contents and type(contents) == 'table' then
if contents[1] == '%REF%' then
-- Single reference
contents = {contents}
end
obj.contents = {}
for _,c in ipairs(contents) do
local cobj = maybe_dereference_object(c, pdf, task)
if cobj and type(cobj) == 'table' then
obj.contents[#obj.contents + 1] = cobj
cobj.parent = obj
cobj.type = 'content'
end
end
lua_util.debugm(N, task, 'found content objects for %s:%s -> %s',
obj.major, obj.minor, #obj.contents)
end
local resources = dict.Resources
if resources and type(resources) == 'table' then
obj.resources = maybe_dereference_object(resources, pdf, task)
if type(obj.resources) ~= 'table' then
rspamd_logger.infox(task, 'cannot parse resources from pdf: %s returned by grammar',
obj.resources)
obj.resources = {}
elseif obj.resources.dict then
obj.resources = obj.resources.dict
end
else
-- Fucking pdf: we need to inherit from parent
resources = {}
if dict.Parent then
local parent = maybe_dereference_object(dict.Parent, pdf, task)
if parent and type(parent) == 'table' and parent.dict then
if parent.resources then
lua_util.debugm(N, task, 'propagated resources from %s:%s to %s:%s',
parent.major, parent.minor, obj.major, obj.minor)
resources = parent.resources
end
end
end
obj.resources = resources
end
local fonts = obj.resources.Font
if fonts and type(fonts) == 'table' then
obj.fonts = {}
for k,v in pairs(fonts) do
obj.fonts[k] = maybe_dereference_object(v, pdf, task)
if obj.fonts[k] then
local font = obj.fonts[k]
if config.text_extraction then
process_font(task, pdf, font, k)
lua_util.debugm(N, task, 'found font "%s" for object %s:%s -> %s',
k, obj.major, obj.minor, font)
end
end
end
end
lua_util.debugm(N, task, 'found resources for object %s:%s (%s): %s',
obj.major, obj.minor, obj.type, obj.resources)
if obj.type == 'Action' then
process_action(task, pdf, obj)
elseif obj.type == 'Catalog' then
process_catalog(task, pdf, obj)
elseif obj.type == 'XRef' then
-- XRef stream instead of trailer from PDF 1.5 (thanks Adobe)
process_xref(task, pdf, obj)
elseif obj.type == 'Javascript' then
local js = maybe_dereference_object(obj.dict.JS, pdf, task)
if js then
if type(js) == 'table' then
local extracted_js = maybe_extract_object_stream(js, pdf, task)
if not extracted_js then
lua_util.debugm(N, task, 'invalid type for javascript from %s:%s: %s',
obj.major, obj.minor, js)
else
js = extracted_js
end
end
js = process_javascript(task, pdf, js)
if js then
obj.js = js
lua_util.debugm(N, task, 'extracted javascript from %s:%s: %s',
obj.major, obj.minor, obj.js.data)
else
lua_util.debugm(N, task, 'invalid type for javascript from %s:%s: %s',
obj.major, obj.minor, js)
end
end
end
end -- Already processed dict (obj.type is not empty)
end
-- This function is intended to unpack objects from ObjStm crappy structure
local compound_obj_grammar
local function compound_obj_grammar_gen()
if not compound_obj_grammar then
local gen = generic_grammar_elts()
compound_obj_grammar = gen.ws^0 * (gen.comment * gen.ws^1)^0 *
lpeg.Ct(lpeg.Ct(gen.number * gen.ws^1 * gen.number * gen.ws^0)^1)
end
return compound_obj_grammar
end
local function pdf_compound_object_unpack(_, uncompressed, pdf, task, first)
-- First, we need to parse data line by line likely to find a line
-- that consists of pairs of numbers
compound_obj_grammar_gen()
local elts = compound_obj_grammar:match(uncompressed)
if elts and #elts > 0 then
lua_util.debugm(N, task, 'compound elts (chunk length %s): %s',
#uncompressed, elts)
for i,pair in ipairs(elts) do
local obj_number,offset = pair[1], pair[2]
offset = offset + first
if offset < #uncompressed then
local span_len
if i == #elts then
span_len = #uncompressed - offset
else
span_len = (elts[i + 1][2] + first) - offset
end
if span_len > 0 and offset + span_len < #uncompressed then
local obj = {
major = obj_number,
minor = 0, -- Implicit
data = uncompressed:span(offset + 1, span_len),
ref = obj_ref(obj_number, 0)
}
parse_object_grammar(obj, task, pdf)
if obj.dict then
pdf.objects[#pdf.objects + 1] = obj
end
end
end
end
end
end
-- PDF 1.5 ObjStmt
local function extract_pdf_compound_objects(task, pdf)
for _,obj in ipairs(pdf.objects or {}) do
if obj.stream and obj.dict and type(obj.dict) == 'table' then
local t = obj.dict.Type
if t and t == 'ObjStm' then
-- We are in troubles sir...
local nobjs = tonumber(maybe_dereference_object(obj.dict.N, pdf, task))
local first = tonumber(maybe_dereference_object(obj.dict.First, pdf, task))
if nobjs and first then
--local extend = maybe_dereference_object(obj.dict.Extends, pdf, task)
lua_util.debugm(N, task, 'extract ObjStm with %s objects (%s first) %s extend',
nobjs, first, obj.dict.Extends)
local uncompressed = maybe_extract_object_stream(obj, pdf, task)
if uncompressed then
pdf_compound_object_unpack(obj, uncompressed, pdf, task, first)
end
else
lua_util.debugm(N, task, 'ObjStm object %s:%s has bad dict: %s',
obj.major, obj.minor, obj.dict)
end
end
end
end
end
-- This function arranges starts and ends of all objects and process them into initial
-- set of objects
local function extract_outer_objects(task, input, pdf)
local start_pos, end_pos = 1, 1
local obj_count = 0
while start_pos <= #pdf.start_objects and end_pos <= #pdf.end_objects do
local first = pdf.start_objects[start_pos]
local last = pdf.end_objects[end_pos]
-- 7 is length of `endobj\n`
if first + 7 < last then
local len = last - first - 7
-- Also get the starting span and try to match it versus obj re to get numbers
local obj_line_potential = first - 32
if obj_line_potential < 1 then obj_line_potential = 1 end
local prev_obj_end = pdf.end_objects[end_pos - 1]
if end_pos > 1 and prev_obj_end >= obj_line_potential and prev_obj_end < first then
obj_line_potential = prev_obj_end + 1
end
local obj_line_span = input:span(obj_line_potential, first - obj_line_potential + 1)
local matches = object_re:search(obj_line_span, true, true)
if matches and matches[1] then
local nobj = {
start = first,
len = len,
data = input:span(first, len),
major = tonumber(matches[1][2]),
minor = tonumber(matches[1][3]),
}
pdf.objects[obj_count + 1] = nobj
if nobj.major and nobj.minor then
-- Add reference
local ref = obj_ref(nobj.major, nobj.minor)
nobj.ref = ref -- Our internal reference
pdf.ref[ref] = nobj
end
end
obj_count = obj_count + 1
start_pos = start_pos + 1
end_pos = end_pos + 1
elseif first > last then
end_pos = end_pos + 1
else
start_pos = start_pos + 1
end_pos = end_pos + 1
end
end
end
-- This function attaches streams to objects and processes outer pdf grammar
local function attach_pdf_streams(task, input, pdf)
if pdf.start_streams and pdf.end_streams then
local start_pos, end_pos = 1, 1
for _,obj in ipairs(pdf.objects) do
while start_pos <= #pdf.start_streams and end_pos <= #pdf.end_streams do
local first = pdf.start_streams[start_pos]
local last = pdf.end_streams[end_pos]
last = last - 10 -- Exclude endstream\n pattern
lua_util.debugm(N, task, "start: %s, end: %s; obj: %s-%s",
first, last, obj.start, obj.start + obj.len)
if first > obj.start and last < obj.start + obj.len and last > first then
-- In case if we have fake endstream :(
while pdf.end_streams[end_pos + 1] and pdf.end_streams[end_pos + 1] < obj.start + obj.len do
end_pos = end_pos + 1
last = pdf.end_streams[end_pos]
end
-- Strip the first \n
while first < last do
local chr = input:at(first)
if chr ~= 13 and chr ~= 10 then break end
first = first + 1
end
local len = last - first
obj.stream = {
start = first,
len = len,
data = input:span(first, len)
}
start_pos = start_pos + 1
end_pos = end_pos + 1
break
elseif first < obj.start then
start_pos = start_pos + 1
elseif last > obj.start + obj.len then
-- Not this object
break
else
start_pos = start_pos + 1
end_pos = end_pos + 1
end
end
if obj.stream then
lua_util.debugm(N, task, 'found object %s:%s %s start %s len, %s stream start, %s stream length',
obj.major, obj.minor, obj.start, obj.len, obj.stream.start, obj.stream.len)
else
lua_util.debugm(N, task, 'found object %s:%s %s start %s len, no stream',
obj.major, obj.minor, obj.start, obj.len)
end
end
end
end
-- Processes PDF objects: extracts streams, object numbers, process outer grammar,
-- augment object types
local function postprocess_pdf_objects(task, input, pdf)
pdf.objects = {} -- objects table
pdf.ref = {} -- references table
extract_outer_objects(task, input, pdf)
-- Now we have objects and we need to attach streams that are in bounds
attach_pdf_streams(task, input, pdf)
-- Parse grammar for outer objects
for _,obj in ipairs(pdf.objects) do
if obj.ref then
parse_object_grammar(obj, task, pdf)
end
end
extract_pdf_compound_objects(task, pdf)
-- Now we might probably have all objects being processed
for _,obj in ipairs(pdf.objects) do
if obj.dict then
-- Types processing
process_dict(task, pdf, obj, obj.dict)
end
end
end
local function offsets_to_blocks(starts, ends, out)
local start_pos, end_pos = 1, 1
while start_pos <= #starts and end_pos <= #ends do
local first = starts[start_pos]
local last = ends[end_pos]
if first < last then
local len = last - first
out[#out + 1] = {
start = first,
len = len,
}
start_pos = start_pos + 1
end_pos = end_pos + 1
elseif first > last then
end_pos = end_pos + 1
else
-- Not ordered properly!
break
end
end
end
local function search_text(task, pdf)
for _,obj in ipairs(pdf.objects) do
if obj.type == 'Page' and obj.contents then
local text = {}
for _,tobj in ipairs(obj.contents) do
maybe_extract_object_stream(tobj, pdf, task)
local matches = pdf_text_trie:match(tobj.uncompressed or '')
if matches then
local text_blocks = {}
local starts = {}
local ends = {}
for npat,matched_positions in pairs(matches) do
if npat == 1 then
for _,pos in ipairs(matched_positions) do
starts[#starts + 1] = pos
end
else
for _,pos in ipairs(matched_positions) do
ends[#ends + 1] = pos
end
end
end
offsets_to_blocks(starts, ends, text_blocks)
for _,bl in ipairs(text_blocks) do
if bl.len > 2 then
-- To remove \s+ET\b pattern (it can leave trailing space or not but it doesn't matter)
bl.len = bl.len - 2
end
bl.data = tobj.uncompressed:span(bl.start, bl.len)
--lua_util.debugm(N, task, 'extracted text from object %s:%s: %s',
-- tobj.major, tobj.minor, bl.data)
if bl.len < config.max_processing_size then
local ret,obj_or_err = pcall(pdf_text_grammar.match, pdf_text_grammar,
bl.data)
if ret then
text[#text + 1] = obj_or_err
lua_util.debugm(N, task, 'attached %s from content object %s:%s to %s:%s',
obj_or_err, tobj.major, tobj.minor, obj.major, obj.minor)
else
lua_util.debugm(N, task, 'object %s:%s cannot be parsed: %s',
obj.major, obj.minor, obj_or_err)
end
end
end
end
end
-- Join all text data together
if #text > 0 then
obj.text = rspamd_text.fromtable(text)
lua_util.debugm(N, task, 'object %s:%s is parsed to: %s',
obj.major, obj.minor, obj.text)
end
end
end
end
-- This function searches objects for `/URI` key and parses it's content
local function search_urls(task, pdf)
local function recursive_object_traverse(obj, dict, rec)
if rec > 10 then
lua_util.debugm(N, task, 'object %s:%s recurses too much',
obj.major, obj.minor)
return
end
for k,v in pairs(dict) do
if type(v) == 'table' then
recursive_object_traverse(obj, v, rec + 1)
elseif k == 'URI' then
v = maybe_dereference_object(v, pdf, task)
if type(v) == 'string' then
local url = rspamd_url.create(task:get_mempool(), v, {'content'})
if url then
lua_util.debugm(N, task, 'found url %s in object %s:%s',
v, obj.major, obj.minor)
task:inject_url(url)
end
end
end
end
end
for _,obj in ipairs(pdf.objects) do
if obj.dict and type(obj.dict) == 'table' then
recursive_object_traverse(obj, obj.dict, 0)
end
end
end
local function process_pdf(input, _, task)
if not config.enabled then
-- Skip processing
return {}
end
local matches = pdf_trie:match(input)
if matches then
local pdf_output = {
tag = 'pdf',
extract_text = extract_text_data,
}
local grouped_processors = {}
for npat,matched_positions in pairs(matches) do
local index = pdf_indexes[npat]
local proc_key,loc_npat = index[1], index[4]
if not grouped_processors[proc_key] then
grouped_processors[proc_key] = {
processor_func = processors[proc_key],
offsets = {},
}
end
local proc = grouped_processors[proc_key]
-- Fill offsets
for _,pos in ipairs(matched_positions) do
proc.offsets[#proc.offsets + 1] = {pos, loc_npat}
end
end
for name,processor in pairs(grouped_processors) do
-- Sort by offset
lua_util.debugm(N, task, "pdf: process group %s with %s matches",
name, #processor.offsets)
table.sort(processor.offsets, function(e1, e2) return e1[1] < e2[1] end)
processor.processor_func(input, task, processor.offsets, pdf_output)
end
pdf_output.flags = {}
if pdf_output.start_objects and pdf_output.end_objects then
-- Postprocess objects
postprocess_pdf_objects(task, input, pdf_output)
if config.text_extraction then
search_text(task, pdf_output)
end
if config.url_extraction then
search_urls(task, pdf_output)
end
if config.js_fuzzy and pdf_output.scripts then
pdf_output.fuzzy_hashes = {}
if config.openaction_fuzzy_only then
-- OpenAction only
if pdf_output.openaction and pdf_output.openaction.bin_hash then
if config.min_js_fuzzy and #pdf_output.openaction.data >= config.min_js_fuzzy then
lua_util.debugm(N, task, "pdf: add fuzzy hash from openaction: %s",
pdf_output.openaction.hash)
table.insert(pdf_output.fuzzy_hashes, pdf_output.openaction.bin_hash)
else
lua_util.debugm(N, task, "pdf: skip fuzzy hash from Javascript: %s, too short: %s",
pdf_output.openaction.hash, #pdf_output.openaction.data)
end
end
else
-- All hashes
for h,sc in pairs(pdf_output.scripts) do
if config.min_js_fuzzy and #sc.data >= config.min_js_fuzzy then
lua_util.debugm(N, task, "pdf: add fuzzy hash from Javascript: %s",
sc.hash)
table.insert(pdf_output.fuzzy_hashes, h)
else
lua_util.debugm(N, task, "pdf: skip fuzzy hash from Javascript: %s, too short: %s",
sc.hash, #sc.data)
end
end
end
end
else
pdf_output.flags.no_objects = true
end
return pdf_output
end
end
-- Processes the PDF trailer
processors.trailer = function(input, task, positions, output)
local last_pos = positions[#positions]
local last_span = input:span(last_pos[1])
for line in last_span:lines(true) do
if line:find('/Encrypt ') then
lua_util.debugm(N, task, "pdf: found encrypted line in trailer: %s",
line)
output.encrypted = true
end
end
end
processors.suspicious = function(_, task, _, output)
lua_util.debugm(N, task, "pdf: found a suspicious pattern")
output.suspicious = true
end
local function generic_table_inserter(positions, output, output_key)
if not output[output_key] then
output[output_key] = {}
end
local shift = #output[output_key]
for i,pos in ipairs(positions) do
output[output_key][i + shift] = pos[1]
end
end
processors.start_object = function(_, task, positions, output)
generic_table_inserter(positions, output, 'start_objects')
end
processors.end_object = function(_, task, positions, output)
generic_table_inserter(positions, output, 'end_objects')
end
processors.start_stream = function(_, task, positions, output)
generic_table_inserter(positions, output, 'start_streams')
end
processors.end_stream = function(_, task, positions, output)
generic_table_inserter(positions, output, 'end_streams')
end
exports.process = process_pdf
return exports
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