README

This is the README file for LibSecRm, a library which ensures
 secure removing of files and clearing memory on the system to
 prevent leakage of sensitive data.

The function replacements in LibSecRm first securely wipe the part of the
 file which would be deleted (just like 'shred', but only rejected
 parts of files get destroyed, not the whole files) to prevent leakage of
 sensitive data.
After that, the original functions get called to do their job, so that the
 calling program can continue working as usual.

Read the info documentation (type 'info doc/libsecrm.info') to get more
 information.

Project homepage: https://libsecrm.sourceforge.io/.

Author: Bogdan Drozdowski, bogdro (at) users . sourceforge . net
License: GPLv3+

================================================================

The binary version of LibSecRm is linked with the GNU C Library,
 licensed under the GNU LGPL:

Copyright (C) 1991,92,93,94,95,96,97,98,99,2000,2001,2002,2003,2004,2005,
 2006,2007 Free Software Foundation, Inc.

The GNU C Library is free software; you can redistribute it and/or modify
 it under the terms of the GNU Lesser General Public License as published
 by the Free Software Foundation; either version 2.1 of the License, or
 (at your option) any later version.

The GNU C Library 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 Lesser General Public
 License for more details.

You should have received a copy of the GNU Lesser General Public License
 along with the GNU C Library; if not, see <http://www.gnu.org/licenses/>.

================================================================

Requirements for compiling:

- a working C compiler (C++ compilers won't work due to variable casts)

- development package for the C library (like glibc-devel and glibc-headers)
  with the signal.h and (especially) fcntl.h, unistd.h and sys/stat.h headers.

  Note that some glibc versions (2.11 is known of this) have a bug in their
  dl(v)sym implementation, which may cause LibSecRm to hang during searching
  for the original versions of the substituted C functions. If you observe
  this, it is best to upgrade glibc. If not possible, you can start deleting
  substituted functions from open() and check each time it your current
  version started to work (yes, this decreases security).

  The unistd.h contains functions needed for wiping to work at all. Nothing
  will be done if this file is missing.

  The sys/stat.h contains functions needed to check the wiped object's type.
  LibSecRm will wipe only regular files. If this file is missing, nothing can
  be wiped. This file, along with dirent.h, is also required for advanced
  file checking to work.

  The dlfcn.h header contains functions needed to call the original functions.
  It has to have RTLD_NEXT defined. LibSecRm wouldn't work without this, so it
  won't compile without this.

  The fcntl header has functions needed to prevent wiping files that are
  set to be deleted, but still open. It has to have F_SETLEASE, F_GETSIG and
  F_SETSIG defined in it (this is available on GNU/Linux, but may not be
  available everywhere) for this feature to work.
  LibSecRm will work without this, but strange things may happen. If you don't
  have this, put /bin/bash in the program ban file and "ICE" (without the
  double quotes) in the file ban file (read the "Manual configuration" chapter
  in the "info" documentation).

  The dirent.h header is required for browsing through the /proc file system
  to check if a given file is already opened by anyone (this is the "advanced
  file checking").

- libdl, the dynamic loading library, with its development package
  (unless the required functions are in the C library)

- the 'make' program

Type

	./configure

to configure the library for your system.

LibSecRm allows some programs and files to be banned (not allowed to run under
 LibSecRm, because it could cause data corruption or other problems).
 Two banning files are always supported - ${sysconfdir}/libsecrm.progban and
 ${sysconfdir}/libsecrm.fileban (${sysconfdir} is /usr/local/etc unless
 set otherwise during configure).

If you want to disable additional banning files pointed to by environment
 variables, configure the library with

	./configure --enable-environment=no

If you want to disable additional banning files in users' home directories,
 configure the library with

	./configure --enable-user-files=no

Type 'make' to compile the library.
Documentation comes complied (you can copy it right away), but can be changed
 and recompiled, if you have the 'makeinfo' program ('texinfo' package).

If you wish to use the 25-pass random pattern selection method (like shred)
instead of the 35-pass Gutmann method, use

	./configure --enable-random-method

or

	make CFLAGS='-DLSR_WANT_RANDOM'

If you wish to use Schneier's method instead of the 35-pass Gutmann method, use

	./configure --enable-schneier-method

or

	make CFLAGS='-DLSR_WANT_SCHNEIER'

If you wish to use the DoD method instead of the 35-pass Gutmann method, use

	./configure --enable-dod-method

or

	make CFLAGS='-DLSR_WANT_DOD'

Default number of passes used to wipe data is:
- 35 in Gutmann method
- 25 in random method
- 7 in Schneier's method
- 3 in the DoD method.
Big number of passes can get annoying on slow devices. To use some other
 number of passes, configure LibSecRm with

	./configure --with-passes=n

 or compile the library as follows:

	make CFLAGS='-DPASSES=n'

Replace 'n' with your desired number of passes (minimum recommended is 3).

Default limit size is 1MB - wiping more than 1MB bytes will be done 1kB at a
 time. If you think some other limit would be more suitable, configure
 LibSecRm with

	./configure --with-buffer-size=n

 or compile the library like this:

	make CFLAGS='-DBUF_SIZE=n'

Replace 'n' with your desired limit in bytes. If you wish to have an
 additional pass wiping with zeros, use

	./configure --enable-last-zero

or

	make CFLAGS='-DLAST_PASS_ZERO'

If you wish to have all passes wipe with zeros, use

	./configure --enable-all-zeros

or

	make CFLAGS='-DALL_PASSES_ZERO'

Intercepting the malloc() function is now disabled by default, because it
 causes a crash during initialization on some systems (where dlvsym() calls
 malloc(), causing an infinite loop). If your system doesn't do this and you
 wish to have malloc() intercepted, use

	./configure --enable-intercept-malloc

 (note that not having malloc() intercepted may reveal only the running
 program's data to itself, possibility of reading another's program freed
 memory is removed by intercepting (s)brk).

To use LibSecRm as a development library, configure it with

	./configure --enable-public-interface

and include the header BEFORE any system headers. Compile-time errors
may occur otherwise. Remeber to link your program with LibSecRm -
 adding `-lsecrm' (optionally preceeded with `-L ${libdir}') to GCC is enough.

The public interface is compatible with SWIG (http://www.swig.org), so
 you can make native bindings to LibSecRm for any supported language.

Any flags can be combined like this:

	./configure --enable-all-zeros
	make CFLAGS='-DPASSES=n -DBUF_SIZE=x -DLAST_PASS_ZERO'

Type

	make install

 to install the library. Do NOT make the library suid.
 You wouldn't want user 'nobody' to be able to delete system files, would you?

To make LibSecRm impossible to detect, you must change all the internal
 public function names. To do this, you can use the name randomizing scripts
 in the src directory. You will need the 'sed' and 'sort' programs and either
 Perl or GNU awk.
You can change the name prefix at the top of these scripts to something
 unique. When the script is done working, reconfigure, recompile and reinstall
 the library.
Thus, a typical build sequence with less detection would be

	./configure
	cd src
	./randomize_names_gawk.sh (or 'make x-randomnames')
	cd ..
	make


NOTE: 'make install' is NOT recommended. Create and install an rpm
 package instead, if possible (see below).

Type 'info libsecrm' (after installation) or 'info doc/libsecrm.info'
(before installation) to get help.

=======================================================

Building an RPM package:

1) copy the libsecrm.spec file to $HOME/rpmbuild/SPECS
2) copy the source package libsecrm-XX.tar.gz to $HOME/rpmbuild/SOURCES
3) type
        rpmbuild -ba $HOME/rpmbuild/SPECS/libsecrm.spec
4) get the RPMs from $HOME/rpmbuild/RPMS/<arch> and $HOME/rpmbuild/SRPMS

Building an RPM package (the old way):

1) copy the libsecrm.spec file to /usr/src/redhat/SPECS
2) copy the source package libsecrm-XX.tar.gz to /usr/src/redhat/SOURCES
3) type
	rpmbuild -ba /usr/src/redhat/SPECS/libsecrm.spec
4) get the RPMs from /usr/src/redhat/RPMS/<arch> and /usr/src/redhat/SRPMS