sebastianbiallas/ht

HT Editor
=========

This is HT 2.1.0; Have fun...

About
=====

This program is a file viewer, editor and analyzer for text, binary,
and (especially) executable files.

     This program is free software; you can redistribute it and/or
     modify it under the terms of the GNU General Public License
     version 2 as published by the Free Software Foundation.

     This program is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     General Public License for more details.

     You should have received a copy of the GNU General Public License
     along with this program; if not, write to the Free Software
     Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
     02110-1301 USA.

Key bindings
============

   * General key bindings

     Return            follow link (if applicable)
     Backspace         undo "follow link"
     Space/F6          choose view mode
     Alt+[1-9]         select window
     Alt+0             select window list
     Ctrl+Left/Right   scroll left/right
     Cursor keys       move around
     Page Up/Down      next/prev page
     Alt+S             toggle select
     Ctrl+Ins/Alt+C    copy
     Shift+Ins/Alt+V   insert
     Ctrl+Del/Alt+D    delete
     Shift+Del/Alt+X   cut

   * Window key bindings

     Alt+F3/Ctrl+W     close window
     Ctrl+F5           resize/move mode
                       (in resize/move mode only:)
     Space             toggle resize/move mode
     Cursor keys       resize/move window
     Escape/Return/Ctrl+F5leave resize/move mode

   * Analyser key bindings

     c                 continue code analysis at cursor
     f                 follow dword ptr at address
     n                 name current address (empty string to delete)
     x                 show xrefs (search for xrefs)
     #                 edit comments
     s                 define a string
     i                 define an integer (32bit)
     h                 define a halfword (16bit)
     b                 define a byte (8bit)
     Ctrl+A            call assembler
     Ctrl+F            goto start of current function
                       (indicated in the 2nd line)
     Ctrl+L            goto previous label
     Ctrl+T            show recursive function references



Note: Some keys don't work in HT-posix. Try using Escape instead of
Control or something...

Authors
=======

   * Stefan Weyergraf

   * Sebastian Biallas <[email protected]>

Features
========

HT contains some very advanced and useful features, which you should
carefully inspect:

General features
================

  1. Supported file formats
        * common object file format (COFF/XCOFF32)
               - header
               - image with code/data analyser (x86)

        * executable and linkable format (ELF)
               - header
               - section headers
               - program headers
               - symbol tables
               - image with code/data analyser (x86, AMD64, Alpha,
               PowerPC, ARM, AVR) and relocations

        * linear executables (LE)
               - header
               - VxD descriptor
               - object table
               - page table
               - image with code/data analyser (x86)
               - auto-relocation layer (only internal refs for now)

        * standard dos executables (MZ)
               - header
               - relocations
               - image (disassembly only)

        * new executables (NE)
               - header
               - segments
               - names
               - entrypoints
               - image with code/data analyser (x86)
               - auto-relocation layer (pretty complete)

        * portable executables (PE32, PE64)
               - header
               - import section
               - delay-import section
               - export section
               - resources
               - image with code/data analyser (x86, AMD64, PowerPC,
               Alpha, ARM)
               - preliminary support for .net executables

        * java class files (CLASS)
               - header
               - image with code/data analyser (java bytecode
               disassembler)

        * Mach exe/link format (MachO)
               - header
               - image with code/data analyser (x86, AMD64, PowerPC,
               ARM)

        * X-Box executable (XBE)
               - header
               - imports
               - image with code/data analyser (x86)

        * Flat (FLT)
               - header
               - image with data analyser (no disassembler yet)

        * PowerPC executable format (PEF)
               - header
               - imports - image with code/data analyser (PowerPC)

        * Still some to be implemented (M$-OBJ, ARCH, LX)

  2. Code & Data Analyser
          - finds branch sources and destinations recursively
          - finds procedure entries
          - creates labels based on this information
          - creates xref information
          - allows to interactively analyse unexplored code (press 'c')
          - allows to create/rename/delete labels (press 'n')
          - allows to create/edit comments (press '#')

  3. Target systems
          - GNU/Linux
          - FreeBSD
          - Win32

Configuration files
===================

Global configuration
--------------------

HT automatically creates a file to store its configuration.  It is
called `~/.htcfg2' on Unices and `ht.cfg2' (where ht.exe resides) on
Windows. More specifically it contains HT's registry and the *Note
Global history::.

Per file configuration
----------------------

The analyser (for analysable files) will be stored in an extra file
called `FILENAME.htcfg', where FILENAME is the analysed file. This file
contains all information to restore the complete state of the analyser.

Clipboard
=========

All open files and dialogs use the common clipboard, where all copied
and cut text or binary data is stored. Clipboard operations are
normally binary safe, that means you can copy some binary data out of a
file and paste it into an input line. Exceptions are only the \0
character (binary null), it will be converted to a space in places
where it would not make sense (e.g. file open).

   Although the clipboard won't be saved between different HT sessions
(ie. you will loose it when exiting HT), you can either save and load it
or part of it manually (via Edit->paste into/copy from file) or rely on
the input lines' *Note history: Global history, which is stored and
retrieved from the config file automatically.

Global history
==============

HTs history system is global, which means that you can use it for all
open files. Histories are also grouped by their context. I.e.
file-related and regex-search-related dialogs have their own history
(who would want to open "[0-9][0-9a-z]+" anyway?).

   History entries are stored within the *Note Configuration files::,
so they can be reused when you relaunch.

   You can delete a history entry by pressing DEL inside the history
popup.

Expression evaluation
=====================

HT contains a very powerful expression evaluator which is used in all
dialogs where expressions are expected. These are mainly
blockoperation, goto, search and of course evaluate itself
(Edit->Evaluate).

   You can use all standard math operators (+ - / * % **), logical
operators (! && || ^^), relational operators (== != < > <= >=), bit
operators (~ & | ^), string operators (. for concatenation),
parenthesis, the ternary operator (a?b:c), functions and symbols (both
depending on context).

   The evaluator uses integer, string and float types depending on
context. You can always convert a result via the `int()', `string()'
and `float()' functions to appropriate type. Try Edit->Evaluate to see
how it works...

Functions and symbols
---------------------

You can always use the standard built-in math (`round', `sin',
`random', etc.) and string (`strcmp', `strchr', `sprintf', etc.)
functions, they work more or less like the corresponding C functions
(actually they ARE more or less wrappers for them); see `eval/eval.y'
for details (sorry but a detailed help would get outdated rather soon).

   The symbol _ always refers to the last result.  If you are in a hex
buffer, the variable `first' contains the offset of the first byte and
the variable `last' contains the offset of the last byte. This is
useful, for instance, if you want to jump to the last byte of a file.

   When using *Note Block operations::, or searching you have some
context depending functions and symbols; see these sections for
explanation.

Block operations
================

Block operation (Blockop) is a very powerful tool to perform
modifications on binary files. It is available in hex viewer only.

   Blockop takes four parameters: START, END, MODE and EXPRESSION.
Blockop works as follows:

   * START: Start at the offset specified by START

   * REPEAT: Evaluate EXPRESSION and store n bytes (1 - byte, 2 - word,
     4 - dword, variable - string) at the current offset. Increment
     current offset by n. Stop if END has been reached.

Special variables/functions that can be used in EXPRESSION:

`readbyte(ofs)'
     read a byte from offset OFS, returns a number

`readstring(ofs, size)'
     read SIZE bytes from offset OFS, returns a string

`i'
     contains the iteration count/index starting with 0

`o'
     contains the current offset

Search and its different modes
==============================

The search function is one of the most advanced functions of HT.  It is
invoked through F7, Shift-F7 continues a search from cursor.  Depending
on context (ie. file type and mode) the following modes are enabled:

bin: ASCII / Hex
----------------

Enter an exact search string either via ascii characters or via
hexadecimal interpretation. This is the fastest search mode. You may
specify a case-insensitive search.

bin: eval str
-------------

Enter an expression, it will be evaluated ONCE (difference to the 4th
mode), and HT will then search for the result-string. This is pretty
useful when searching for intermixed text and control-chars/binary,
e.g. `"hello world\n\0"'

display: regex
--------------

As the prefix indicates, this search doesn't search in the binary file
but in the display on screen. HT searches for a regular expression so
this can be very powerful, e.g. in PE/Image you can search for
`(add|sub).+?,\ [78]$'.  This will find all add or sub instructions
with second parameter 7 or 8.

expr nonzero
------------

This is the slowest but also most advanced search mode. Enter an
expression and the search stops if this expression evaluates to
non-zero (it will be evaluated on every byte). In this mode there are
two predefined symbols and some functions: I is always the number of
current iteration and O stands for the current offset in file. With the
functions `readbyte(ofs)' and `readstring(ofs, size)' you access the
file's content.

   It's easier to understand this with examples:

  1. Searching for patterns:

       a. Enter `readbyte(o) == readbyte(o+1)'
          This will search for two equal bytes ("AA", "55", "!!", etc.).

       b. Enter `(readbyte(o) == readbyte(o+1)-1) &&
          (readbyte(o)==readbyte(o+2)-2)'
          This will search for three ascending bytes ("ABC", "123",
          etc).

  2. Search with special functions:

     With HT you can easily detect the RSA key in the `ADVAPI32.DLL':
     Search for `entropy(readstring(o, 64)) > 82' in expr!=0 mode, and
     you will find it very quickly. How does it work? `readstring(o,
     64)' reads a 64 byte string from current offset and entropy
     calculates the entropy ("randomness") of a string (result is
     0..100).  So the search stops if an entropy greater than 82%
     (guessed value) is encountered, which normally indicates packed or
     encrypted data.

     Note: the `entropy()' function is not the best of its kind, if you
     know of a better one please let us know!


Command line options
====================

`--'                   treat all additional parameters as file names
`-v'    `--version'    show version and copyright on console
`-h'    `--help'       show help
`-t'    `--text'       load file(s) in text editor mode
`-b'    `--bin'        load file(s) in hex editor mode
`-a'    `--auto'       try to guess file type

Where to download?
==================

The HT homepage is located at `http://hte.sourceforge.net'

Downloads are available from the 'download' section.  Please also take
a look at `http://sourceforge.net/projects/hte'