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authorKarl Berry <karl@freefriends.org>2024-06-30 22:17:00 +0000
committerKarl Berry <karl@freefriends.org>2024-06-30 22:17:00 +0000
commitee038309774ac7c79b5a8a4013eab738cf761c0c (patch)
treef451b941b48e580ccc50b6a22f8ea7499acc8113 /Master/texmf-dist
parentcf99e73a6f064cbe900226e778bf49b2ad4d9765 (diff)
extractbb.lua wrapper for safety
git-svn-id: svn://tug.org/texlive/trunk@71664 c570f23f-e606-0410-a88d-b1316a301751
Diffstat (limited to 'Master/texmf-dist')
-rwxr-xr-xMaster/texmf-dist/scripts/texlive/extractbb.lua247
-rw-r--r--Master/texmf-dist/web2c/texmf.cnf2
2 files changed, 248 insertions, 1 deletions
diff --git a/Master/texmf-dist/scripts/texlive/extractbb.lua b/Master/texmf-dist/scripts/texlive/extractbb.lua
new file mode 100755
index 00000000000..7584814ee80
--- /dev/null
+++ b/Master/texmf-dist/scripts/texlive/extractbb.lua
@@ -0,0 +1,247 @@
+#!/usr/bin/env texlua
+-- $Id$
+-- SPDX-License-Identifier: CC0-1.0
+-- SPDX-FileCopyrightText: 2024 Max Chernoff
+--
+-- A generic wrapper to make commands safe to run with restricted shell escape.
+--
+-- Originally created for extractbb, which is listed in shell_escape_commands,
+-- but can be run as dvipdfm(x), which in turn can run arbitrary commands
+-- using its -D option.
+--
+-- The idea is to exec "ebb --ebb <other args>", since only argv[1] is
+-- used by dvipdfmx to determine its behavior.
+--
+-- Note: This script can only adjust the paths and arguments of the target
+-- executable; it *CANNOT* make an arbitrary program safe to run with
+-- restricted shell escape.
+
+-- A shorter, less paranoid version.
+-- (Prepend a hyphen to the line below to enable).
+--[=[
+arg[0] = arg[0]:gsub("extractbb", "ebb")
+table.insert(arg, 1, "ebb")
+table.insert(arg, 2, "--ebb")
+os.exec(arg)
+os.exit(1)
+--]=]
+
+---------------------
+--- Configuration ---
+---------------------
+
+-- The base name of this script. (Example: ``extractbb'')
+local SCRIPT_NAME = "extractbb"
+
+-- The extension of the script. Extensionless-names are also permitted.
+-- (Example: ``lua'')
+local SCRIPT_EXT = "lua"
+
+-- The base name of the path to the target program. (Example: ``xdvipdfmx'')
+local TARGET_PATH_NAME = "xdvipdfmx"
+
+-- The name to use when calling the target program. Equivalent to ``argv[0]''
+-- in C. (Example: ``extractbb'')
+local TARGET_EXEC_NAME = "ebb"
+
+-- Any extra arguments to be prepended to the target program, before any
+-- user-supplied arguments. Equivalent to ``argv[1], ...'' in C.
+-- (Example: ``--extractbb'')
+local TARGET_PREPEND_ARGS = { "--ebb" }
+
+-- Any extra arguments to be appended to the target program, after any
+-- user-supplied arguments. Equivalent to ``..., argv[argc]'' in C.
+local TARGET_APPEND_ARGS = {}
+
+-- Sets the value of ``openin_any'' to this value. If ``nil'', then the value
+-- will be left unchanged. (Example: ``r'')
+local READ_PERMS = "r"
+
+-- Sets the value of ``openout_any'' to this value. If ``nil'', then the value
+-- will be left unchanged. (Example: ``p'')
+local WRITE_PERMS = "p"
+
+-- The name of the Lua interpreter. (Example: ``texlua'')
+local INTERPRETER_NAME = "texlua"
+
+-- The extension of the interpreter. Extensionless-names are also permitted.
+-- (Example: ``exe'')
+local INTERPRETER_EXT = "exe"
+
+
+----------------------
+--- Initialization ---
+----------------------
+
+-- Save often-used globals for a slight speed boost.
+local insert = table.insert
+
+-- Set the kpathsea program name
+kpse.set_program_name(INTERPRETER_NAME, SCRIPT_NAME)
+
+-- Rename the input arguments so we don't get confused
+local script_args = arg
+
+
+----------------------------
+--- Function Definitions ---
+----------------------------
+
+-- Error messages
+local function error(message)
+ io.stderr:write("! ERROR (extractbb.lua): " .. message, "\n")
+ io.stderr:write(debug.traceback(nil, 2), "\n")
+ io.stderr:flush()
+ os.exit(1)
+end
+
+-- Get the directory, name, and extension from a full path. We'll split on
+-- either a forward or backward slash---Windows can use either, and we don't
+-- need to support Unix systems with TL installed to a directory with
+-- backslashes in its name.
+local split_dir_pattern = "^(.*)[/\\]([^/\\]-)$"
+local split_ext_pattern = "(.*)%.([^.]-)$"
+
+local function split_path(path)
+ -- Make sure that we were given a string
+ if type(path) ~= "string" then
+ return nil, nil, nil
+ end
+
+ -- Split the (directory) from the (name and extension)
+ local dir, name_ext = path:match(split_dir_pattern)
+
+ -- No directory
+ if not dir then
+ dir = nil
+ name_ext = path
+
+ -- A bare directory (with a trailing slash)
+ elseif name_ext == "" then
+ return dir, nil, nil
+ end
+
+ -- Split the (name) from the (extension)
+ local name, ext = name_ext:match(split_ext_pattern)
+
+ -- No extension (or a dotfile)
+ if (not name) or (name == "") then
+ name = name_ext
+ ext = nil
+ end
+
+ return dir, name, ext
+end
+
+-- See if a file exists
+local function file_exists(path)
+ local mode = lfs.attributes(path, "mode")
+ return (mode == "file") or (mode == "link")
+end
+
+
+---------------------
+--- Safety Checks ---
+---------------------
+
+-- Make sure that we're running unrestricted.
+if status.shell_escape ~= 1 then
+ error("Shell escape has been disabled.")
+end
+
+if status.safer_option ~= 0 then
+ error("The ``safer'' option has been enabled.")
+end
+
+-- Set the file permissions.
+if READ_PERMS then
+ os.setenv("openin_any", READ_PERMS)
+end
+
+if WRITE_PERMS then
+ os.setenv("openout_any", WRITE_PERMS)
+end
+
+-- Get the directory of the script and interpreter
+local script_path = debug.getinfo(1, "S").source:sub(2)
+local script_dir, script_name, script_ext = split_path(script_path)
+
+local interpreter_dir = kpse.var_value("SELFAUTOLOC")
+local _, interpreter_name, interpreter_ext = split_path(script_args[-1])
+if os.type == 'windows' then
+ interpreter_ext = INTERPRETER_EXT
+end
+-- Look up the script again with kpathsea
+local resolved_script_path = kpse.find_file(
+ script_name .. "." .. (script_ext or SCRIPT_EXT), "texmfscripts", true
+)
+
+-- Make sure that our paths are correct
+if not script_dir then
+ error("Empty script dir")
+end
+
+if not resolved_script_path then
+ error("Empty resolved script path")
+end
+
+if (script_dir ~= interpreter_dir) and (script_path ~= resolved_script_path) then
+ error("The script is in an incorrect location: " .. script_dir)
+end
+
+if script_name ~= SCRIPT_NAME then
+ error("Incorrect script name: " .. script_name)
+end
+
+if interpreter_name ~= INTERPRETER_NAME then
+ error("Incorrect interpreter name: " .. interpreter_name)
+end
+
+if (script_ext ~= SCRIPT_EXT) and (script_ext ~= nil) then
+ error("Incorrect script extension: " .. script_ext)
+end
+
+if (interpreter_ext ~= INTERPRETER_EXT) and (interpreter_ext ~= nil) then
+ error("Incorrect interpreter extension: " .. interpreter_ext)
+end
+
+-- Get the path to the target program
+local target_ext = interpreter_ext and ("." .. interpreter_ext) or ""
+local target_path = interpreter_dir .. "/" .. TARGET_PATH_NAME .. target_ext
+
+-- Make sure that the target program exists
+if not file_exists(target_path) then
+ error("The target program does not exist: " .. target_path)
+end
+
+
+----------------------
+--- Run the target ---
+----------------------
+
+-- Generate the target arguments
+local target_args = {
+ [0] = target_path, -- Path to the executable
+ [1] = TARGET_EXEC_NAME, -- argv[0]
+}
+
+-- argv[2] through argv[n]
+for _, arg in ipairs(TARGET_PREPEND_ARGS) do
+ insert(target_args, arg)
+end
+
+for i = 1, #script_args do
+ -- We use a numeric iterator here to avoid ``arg[-1]'' and ``arg[0]''.
+ insert(target_args, script_args[i])
+end
+
+for _, arg in ipairs(TARGET_APPEND_ARGS) do
+ insert(target_args, arg)
+end
+
+-- Run the target program, replacing the current process
+local _, err = os.exec(target_args)
+
+if err then
+ error("The target program failed to run.")
+end
diff --git a/Master/texmf-dist/web2c/texmf.cnf b/Master/texmf-dist/web2c/texmf.cnf
index 333e6325b3d..5df6bd97f9c 100644
--- a/Master/texmf-dist/web2c/texmf.cnf
+++ b/Master/texmf-dist/web2c/texmf.cnf
@@ -649,6 +649,7 @@ shell_escape = p
%
shell_escape_commands = \
bibtex,bibtex8,\
+extractbb,\
gregorio,\
kpsewhich,\
l3sys-query,\
@@ -660,7 +661,6 @@ r-mpost,\
texosquery-jre8,\
% other programs considered:
-% extractbb - allowed in the past, but can be exploited.
% dvips - but external commands can be executed, need at least -R1.
% epspdf, ps2pdf, pstopdf - need to respect openout_any,
% and gs -dSAFER must be used and check for shell injection with filenames.