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Maintaining GNU Findutils
*************************
This manual explains how GNU findutils is maintained, how changes should
be made and tested, and what resources exist to help developers.
This document corresponds to version 4.8.0 of the GNU findutils.
Copyright (C) 2007-2021 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License,
Version 1.3 or any later version published by the Free Software
Foundation; with no Invariant Sections, no Front-Cover Texts, and
no Back-Cover Texts. A copy of the license is included in the
section entitled "GNU Free Documentation License".
* Menu:
* Introduction::
* Maintaining GNU Programs::
* Design Issues::
* Coding Conventions::
* Tools::
* Using the GNU Portability Library::
* Documentation::
* Testing::
* Bugs::
* Distributions::
* Internationalisation::
* Security::
* Making Releases::
* GNU Free Documentation License::
File: find-maint.info, Node: Introduction, Next: Maintaining GNU Programs, Up: Top
1 Introduction
**************
This document explains how to contribute to and maintain GNU Findutils.
It concentrates on developer-specific issues. For information about how
to use the software please refer to *Note Introduction:
(find)Introduction.
This manual aims to be useful without necessarily being verbose.
It's also a recent document, so there will be a many areas in which
improvements can be made. If you find that the document misses out
important information or any part of the document is be so terse as to
be unuseful, please ask for help on the <bug-findutils AT gnu.org> mailing
list. We'll try to improve this document too.
File: find-maint.info, Node: Maintaining GNU Programs, Next: Design Issues, Prev: Introduction, Up: Top
2 Maintaining GNU Programs
**************************
GNU Findutils is part of the GNU Project and so there are a number of
documents which set out standards for the maintenance of GNU software.
'standards.texi'
GNU Project Coding Standards. All changes to findutils should
comply with these standards. In some areas we go somewhat beyond
the requirements of the standards, but these cases are explained in
this manual.
'maintain.texi'
Information for Maintainers of GNU Software. This document
provides guidance for GNU maintainers. Everybody with commit
access should read this document. Everybody else is welcome to do
so too, of course.
File: find-maint.info, Node: Design Issues, Next: Coding Conventions, Prev: Maintaining GNU Programs, Up: Top
3 Design Issues
***************
The findutils package is installed on many many systems, usually as a
fundamental component. The programs in the package are often used in
order to successfully boot or fix the system.
This fact means that for findutils we bear in mind considerations
that may not apply so much as for other packages. For example, the fact
that findutils is often a base component motivates us to
* Limit dependencies on libraries
* Avoid dependencies on other large packages (for example,
interpreters)
* Be conservative when making changes to the 'stable' release branch
All those considerations come before functionality. Functional
enhancements are still made to findutils, but these are almost
exclusively introduced in the 'development' release branch, to allow
extensive testing and proving.
Sometimes it is useful to have a priority list to provide guidance
when making design trade-offs. For findutils, that priority list is:
1. Correctness
2. Standards compliance
3. Security
4. Backward compatibility
5. Performance
6. Functionality
For example, we support the '-exec' action because POSIX compliance
requires this, even though there are security problems with it and we
would otherwise prefer people to use '-execdir'. There are also cases
where some performance is sacrificed in the name of security. For
example, the sanity checks that 'find' performs while traversing a
directory tree may slow it down. We adopt functional changes, and
functional changes are allowed to make 'find' slower, but only if there
is no detectable impact on users who don't use the feature.
Backward-incompatible changes do get made in order to comply with
standards (for example the behaviour of '-perm -...' changed in order to
comply with POSIX). However, they don't get made in order to provide
better ease of use; for example the semantics of '-size -2G' are almost
always unexpected by users, but we retain the current behaviour because
of backward compatibility and for its similarity to the block-rounding
behaviour of '-size -30'. We might introduce a change which does not
have the unfortunate rounding behaviour, but we would choose another
syntax (for example '-size '<2G'') for this.
In a general sense, we try to do test-driven development of the
findutils code; that is, we try to implement test cases for new features
and bug fixes before modifying the code to make the test pass. Some
features of the code are tested well, but the test coverage for other
features is less good. If you are about to modify the code for a
predicate and aren't sure about the test coverage, use 'grep' on the
test directories and measure the coverage with 'lcov' or another test
coverage tool.
You should be able to use the 'coverage' Makefile target (it's
defined in 'maint.mk' to generate a test coverage report for findutils.
Due to limitations in 'lcov', this only works if your build directory is
the same asthe source directory (that is, you're not using a VPATH build
configuration).
Lastly, we try not to depend on having a "working system". The
findutils suite is used for diagnosis of problems, and this applies
especially to 'find'. We should ensure that 'find' still works on
relatively broken systems, for example systems with damaged
'/etc/passwd' or '/etc/fstab' files. Another interesting example is the
case where a system is a client of one or more unresponsive NFS servers.
On such a system, if you try to stat all mount points, your program will
hang indefinitely, waiting for the remote NFS server to respond.
Another interesting but unusual case is broken NFS servers and
corrupt filesystems; sometimes they return 'impossible' file modes.
It's important that find does not entirely fail when encountering such a
file.
File: find-maint.info, Node: Coding Conventions, Next: Tools, Prev: Design Issues, Up: Top
4 Coding Conventions
********************
Coding style documents which set out to establish a uniform look and
feel to source code have worthy goals, for example greater ease of
maintenance and readability. However, I do not believe that in general
coding style guide authors can envisage every situation, and it is
always possible that it might on occasion be necessary to break the
letter of the style guide in order to honour its spirit, or to better
achieve the style guide's goals.
I've certainly seen many style guides outside the free software world
which make bald statements such as "functions shall have exactly one
return statement". The desire to ensure consistency and obviousness of
control flow is laudable, but it is all too common for such bald
requirements to be followed unthinkingly. Certainly I've seen such
coding standards result in unmaintainable code with terrible
infelicities such as functions containing 'if' statements nested nine
levels deep. I suppose such coding standards don't survive in free
software projects because they tend to drive away potential contributors
or tend to generate heated discussions on mailing lists. Equally, a
nine-level-deep function in a free software program would quickly get
refactored, assuming it is obvious what the function is supposed to
do...
Be that as it may, the approach I will take for this document is to
explain some idioms and practices in use in the findutils source code,
and leave it up to the reader's engineering judgement to decide which
considerations apply to the code they are working on, and whether or not
there is sufficient reason to ignore the guidance in current
circumstances.
* Menu:
* Make the Compiler Find the Bugs::
* Factor Out Repeated Code::
* Debugging is For Users Too::
* Don't Trust the File System Contents::
* The File System Is Being Modified::
File: find-maint.info, Node: Make the Compiler Find the Bugs, Next: Factor Out Repeated Code, Up: Coding Conventions
4.1 Make the Compiler Find the Bugs
===================================
Finding bugs is tedious. If I have a filesystem containing two million
files, and a find command line should print one million of them, but in
fact it misses out 1%, you can tell the program is printing the wrong
result only if you know the right answer for that filesystem at that
time. If you don't know this, you may just not find out about that bug.
For this reason it is important to have a comprehensive test suite.
The test suite is of course not the only way to find the bugs. The
findutils source code makes liberal use of the assert macro. While on
the one hand these might be a performance drain, the performance impact
of most of these is negligible compared to the time taken to fetch even
one sector from a disk drive.
Assertions should not be used to check the results of operations
which may be affected by the program's external environment. For
example, never assert that a file could be opened successfully. Errors
relating to problems with the program's execution environment should be
diagnosed with a user-oriented error message. An assertion failure
should always denote a bug in the program.
Avoid using 'assert' to mark not-fully-implemented features of your
code as such. Finish the implementation, disable the code, or leave the
unfinished version on a local branch.
Several programs in the findutils suite perform self-checks. See for
example the function 'pred_sanity_check' in 'find/pred.c'. This is
generally desirable.
There are also a number of small ways in which we can help the
compiler to find the bugs for us.
4.1.1 Constants in Equality Testing
-----------------------------------
It's a common error to write '=' when '==' is meant. Sometimes this
happens in new code and is simply due to finger trouble. Sometimes it
is the result of the inadvertent deletion of a character. In any case,
there is a subset of cases where we can persuade the compiler to
generate an error message when we make this mistake; this is where the
equality test is with a constant.
This is an example of a vulnerable piece of code.
if (x == 2)
...
A simple typo converts the above into
if (x = 2)
...
We've introduced a bug; the condition is always true, and the value
of 'x' has been changed. However, a simple change to our practice would
have made us immune to this problem:
if (2 == x)
...
Usually, the Emacs keystroke 'M-t' can be used to swap the operands.
4.1.2 Spelling of ASCII NUL
---------------------------
Strings in C are just sequences of characters terminated by a NUL. The
ASCII NUL character has the numerical value zero. It is normally
represented in C code as '\0'. Here is a typical piece of C code:
*p = '\0';
Consider what happens if there is an unfortunate typo:
*p = '0';
We have changed the meaning of our program and the compiler cannot
diagnose this as an error. Our string is no longer terminated. Bad
things will probably happen. It would be better if the compiler could
help us diagnose this problem.
In C, the type of ''\0'' is in fact int, not char. This provides us
with a simple way to avoid this error. The constant '0' has the same
value and type as the constant ''\0''. However, it is not as vulnerable
to typos. For this reason I normally prefer to use this code:
*p = 0;
File: find-maint.info, Node: Factor Out Repeated Code, Next: Debugging is For Users Too, Prev: Make the Compiler Find the Bugs, Up: Coding Conventions
4.2 Factor Out Repeated Code
============================
Repeated code imposes a greater maintenance burden and increases the
exposure to bugs. For example, if you discover that something you want
to implement has some similarity with an existing piece of code, don't
cut and paste it. Instead, factor the code out. The risk of cutting
and pasting the code, particularly if you do this several times, is that
you end up with several copies of the same code.
If the original code had a bug, you now have N places where this
needs to be fixed. It's all to easy to miss some out when trying to fix
the bug. Equally, it's quite possible that when pasting the code into
some function, the pasted code was not quite adapted correctly to its
new environment. To pick a contrived example, perhaps it modifies a
global variable which it (that [original] code) shouldn't be touching in
its new home. Worse, perhaps it makes some unstated assumption about
the nature of the input arguments which is in fact not true for the
context of the now duplicated code.
A good example of the use of refactoring in findutils is the
'collect_arg' function in 'find/parser.c'. A less clear-cut but larger
example is the factoring out of code which would otherwise have been
duplicated between 'find/oldfind.c' and 'find/ftsfind.c'.
The findutils test suite is comprehensive enough that refactoring
code should not generally be a daunting prospect from a testing point of
view. Nevertheless there are some areas which are only lightly-tested:
1. Tests on the ages of files
2. Code which deals with the values returned by operating system calls
(for example handling of ENOENT)
3. Code dealing with OS limits (for example, limits on path length or
exec arguments)
4. Code relating to features not all systems have (for example Solaris
Doors)
Please exercise caution when working in those areas.
File: find-maint.info, Node: Debugging is For Users Too, Next: Don't Trust the File System Contents, Prev: Factor Out Repeated Code, Up: Coding Conventions
4.3 Debugging is For Users Too
==============================
Debug and diagnostic code is often used to verify that a program is
working in the way its author thinks it should be. But users are often
uncertain about what a program is doing, too. Exposing them a little
more diagnostic information can help. Much of the diagnostic code in
'find', for example, is controlled by the '-D' flag, as opposed to C
preprocessor directives.
Making diagnostic messages available to users also means that the
phrasing of the diagnostic messages becomes important, too.
File: find-maint.info, Node: Don't Trust the File System Contents, Next: The File System Is Being Modified, Prev: Debugging is For Users Too, Up: Coding Conventions
4.4 Don't Trust the File System Contents
========================================
People use 'find' to search in directories created by other people.
Sometimes they do this to check to suspicious activity (for example to
look for new setuid binaries). This means that it would be bad if
'find' were vulnerable to, say, a security problem exploitable by
constructing a specially-crafted filename. The same consideration would
apply to 'locate' and 'updatedb'.
Henry Spencer said this well in his fifth commandment:
Thou shalt check the array bounds of all strings (indeed, all
arrays), for surely where thou typest 'foo' someone someday shall
type 'supercalifragilisticexpialidocious'.
Symbolic links can often be a problem. If 'find' calls 'lstat' on
something and discovers that it is a directory, it's normal for 'find'
to recurse into it. Even if the 'chdir' system call is used
immediately, there is still a window of opportunity between the 'lstat'
and the 'chdir' in which a malicious person could rename the directory
and substitute a symbolic link to some other directory.
File: find-maint.info, Node: The File System Is Being Modified, Prev: Don't Trust the File System Contents, Up: Coding Conventions
4.5 The File System Is Being Modified
=====================================
The filesystem gets modified while you are traversing it. For, example,
it's normal for files to get deleted while 'find' is traversing a
directory. Issuing an error message seems helpful when a file is
deleted from the one directory you are interested in, but if 'find' is
searching 15000 directories, such a message becomes less helpful.
Bear in mind also that it is possible for the directory 'find' is
searching to be concurrently moved elsewhere in the file system, and
that the directory in which 'find' was started could be deleted.
Henry Spencer's sixth commandment is also apposite here:
If a function be advertised to return an error code in the event of
difficulties, thou shalt check for that code, yea, even though the
checks triple the size of thy code and produce aches in thy typing
fingers, for if thou thinkest "it cannot happen to me", the gods
shall surely punish thee for thy arrogance.
There are a lot of files out there. They come in all dates and
sizes. There is a condition out there in the real world to exercise
every bit of the code base. So we try to test that code base before
someone falls over a bug.
File: find-maint.info, Node: Tools, Next: Using the GNU Portability Library, Prev: Coding Conventions, Up: Top
5 Tools
*******
Most of the tools required to build findutils are mentioned in the file
'README-hacking'. We also use some other tools:
System call traces
Much of the execution time of find is spent waiting for filesystem
operations. A system call trace (for example, that provided by
'strace') shows what system calls are being made. Using this
information we can work to remove unnecessary file system
operations.
Valgrind
Valgrind is a tool which dynamically verifies the memory accesses a
program makes to ensure that they are valid (for example, that the
behaviour of the program does not in any way depend on the contents
of uninitialized memory).
DejaGnu
DejaGnu is the test framework used to run the findutils test suite
(the 'runtest' program is part of DejaGnu). It would be ideal if
everybody building 'findutils' also ran the test suite, but many
people don't have DejaGnu installed. When changes are made to
findutils, DejaGnu is invoked a lot. *Note Testing::, for more
information.
File: find-maint.info, Node: Using the GNU Portability Library, Next: Documentation, Prev: Tools, Up: Top
6 Using the GNU Portability Library
***********************************
The Gnulib library (<https://www.gnu.org/software/gnulib/>) makes a
variety of systems look more like a GNU/Linux system and also applies a
bunch of automatic bug fixes and workarounds. Some of these also apply
to GNU/Linux systems too. For example, the Gnulib regex implementation
is used when we determine that we are building on a GNU libc system with
a bug in the regex implementation.
6.1 How and Why we Import the Gnulib Code
=========================================
Gnulib does not have a release process which results in a source tarball
you can download. Instead, the code is simply made available by GIT, so
we import gnulib via the submodule feature. The bootstrap script
performs the necessary steps.
Findutils does not use all the Gnulib code. The modules we need are
listed in the file 'bootstrap.conf'.
The upshot of all this is that we can use the findutils git
repository to track which version of Gnulib every findutils release
uses.
A small number of files are installed by automake and will therefore
vary according to which version of automake was used to generate a
release. This includes for example boiler-plate GNU files such as
'ABOUT-NLS', 'INSTALL' and 'COPYING'.
6.2 How We Fix Gnulib Bugs
==========================
Gnulib is used by quite a number of GNU projects, and this means that it
gets plenty of testing. Therefore there are relatively few bugs in the
Gnulib code, but it does happen from time to time.
However, since there is no waiting around for a Gnulib source release
tarball, Gnulib bugs are generally fixed quickly. Here is an outline of
the way we would contribute a fix to Gnulib (assuming you know it is not
already fixed in the current Gnulib git tree):
Check you already completed a copyright assignment for Gnulib
Begin with a vanilla git tree
Download the Findutils source code from git (or use the tree you
have already)
Run the bootstrap script
Run configure
Build findutils
Build findutils and run the test suite, which should pass. In our
example we assume you have just noticed a bug in Gnulib, not that
recent Gnulib changes broke the findutils regression tests.
Write a test case
If in fact Gnulib did break the findutils regression tests, you can
probably skip this step, since you already have a test case
demonstrating the problem. Otherwise, write a findutils test case
for the bug and/or a Gnulib test case.
Fix the Gnulib bug
Make sure your editor follows symbolic links so that your changes
to 'gnulib/...' actually affect the files in the git working
directory you checked out earlier. Observe that your test now
passes.
Prepare a Gnulib patch
In the gnulib subdirectory, use 'git format-patch' to prepare the
patch. Follow the normal usage for checkin comments (take a look
at the output of 'git log'). Check that the patch conforms with
the GNU coding standards, and email it to the Gnulib mailing list.
Wait for the patch to be applied
Once your bug fix has been applied, you can update your gnulib
directory from git, and then check in the change to the submodule
as normal (you can check 'git help submodule' for details).
There is an alternative to the method above; it is possible to store
local diffs to be patched into gnulib beneath the 'gnulib-local'.
Normally however, there is no need for this, since gnulib updates are
very prompt.
6.3 How to update Gnulib to latest
==================================
With a non-dirty working tree, the command 'make
update-gnulib-to-latest' (or the shorter alias 'make gnulib-sync'
allows, well, to update the gnulib submodule. In detail, that is:
1. Fetching the latest upstream gnulib reference.
2. Copying the files which should stay in sync like 'bootstrap' from
gnulib into the findutils working tree.
3. And finally showing the 'git status' for the gnulib submodule and
the above copied files.
After that, the maintainer compares if all is correct, if the
findutils build and run correct, and finally commits with the new gnulib
version, e.g. via 'git gui'.
The 'gnulib-sync' target can be run any time - after a 'configure'
run -, and only rejects to run if the working tree is dirty.
File: find-maint.info, Node: Documentation, Next: Testing, Prev: Using the GNU Portability Library, Up: Top
7 Documentation
***************
The findutils git tree includes several different types of
documentation.
7.1 git change log
==================
The git change log for the source tree contains check-in messages which
describe each check-in. These have a standard format:
Summary of the change.
(ChangeLog-style detail)
Here, the format of the detail part follows the standard GNU
ChangeLog style, but without whitespace in the left margin and without
author/date headers. Take a look at the output of 'git log' to see some
examples. The README-hacking file also contains an example with an
explanation.
7.2 User Documentation
======================
User-oriented documentation is provided as manual pages and in Texinfo.
See *note Introduction: (find)Introduction.
Please make sure both sets of documentation are updated if you make a
change to the code. The GNU coding standards do not normally call for
maintaining manual pages on the grounds of effort duplication. However,
the manual page format is more convenient for quick reference, and so
it's worth maintaining both types of documentation. However, the manual
pages are normally rather more terse than the Texinfo documentation.
The manual pages are suitable for reference use, but the Texinfo manual
should also include introductory and tutorial material.
We make the user documentation available on the web, on the GNU
project web site. These web pages are source-controlled via CVS
(still!). If you are a member of the 'findutils' project on Savannah
you should be able to check the web pages out like this ('$USER' is a
placeholder for your Savannah username):
cvs -d :ext:$USER AT cvs.org:/web/findutils checkout findutils/manual
You can automatically update the documentation in this repository
using the script 'build-aux/update-online-manual.sh' in the findutils
Git repository.
7.3 Build Guidance
==================
'ABOUT-NLS'
Describes the Free Translation Project, the translation status of
various GNU projects, and how to participate by translating an
application.
'AUTHORS'
Lists the authors of findutils.
'COPYING'
The copyright license covering findutils; currently, the GNU GPL,
version 3.
'INSTALL'
Generic installation instructions for installing GNU programs.
'README'
Information about how to compile findutils in particular
'README-hacking'
Describes how to build findutils from the code in git.
'THANKS'
Thanks for people who contributed to findutils. Generally, if
someone's contribution was significant enough to need a copyright
assignment, their name should go in here.
'TODO'
Mainly obsolete. Please add bugs to the Savannah bug tracker
instead of adding entries to this file.
7.4 Release Information
=======================
'NEWS'
Enumerates the user-visible change in each release. Typical
changes are fixed bugs, functionality changes and documentation
changes. Include the date when a release is made.
'ChangeLog'
This file enumerates all changes to the findutils source code (with
the possible exception of '.cvsignore' and '.gitignore' changes).
The level of detail used for this file should be sufficient to
answer the questions "what changed?" and "why was it changed?".
The file is generated from the git commit messages during 'make
dist'. If a change fixes a bug, always give the bug reference
number in the 'NEWS' file and of course also in the checkin
message. In general, it should be possible to enumerate all
material changes to a function by searching for its name in
'ChangeLog'. Mention when each release is made.
File: find-maint.info, Node: Testing, Next: Bugs, Prev: Documentation, Up: Top
8 Testing
*********
This chapter will explain the general procedures for adding tests to the
test suite, and the functions defined in the findutils-specific DejaGnu
configuration. Where appropriate references will be made to the DejaGnu
documentation.
File: find-maint.info, Node: Bugs, Next: Distributions, Prev: Testing, Up: Top
9 Bugs
******
Bugs are logged in the Savannah bug tracker
<https://savannah.gnu.org/bugs/?group=findutils>. The tracker offers
several fields but their use is largely obvious. The life-cycle of a
bug is like this:
Open
Someone, usually a maintainer, a distribution maintainer or a user,
creates a bug by filling in the form. They fill in field values as
they see fit. This will generate an email to
<bug-findutils AT gnu.org>.
Triage
The bug hangs around with 'Status=None' until someone begins to
work on it. At that point they set the "Assigned To" field and
will sometimes set the status to 'In Progress', especially if the
bug will take a while to fix.
Non-bugs
Quite a lot of reports are not actually bugs; for these the usual
procedure is to explain why the problem is not a bug, set the
status to 'Invalid' and close the bug. Make sure you set the
'Assigned to' field to yourself before closing the bug.
Fixing
When you commit a bug fix into git (or in the case of a contributed
patch, commit the change), mark the bug as 'Fixed'. Make sure you
include a new test case where this is relevant. If you can figure
out which releases are affected, please also set the 'Release'
field to the earliest release which is affected by the bug.
Indicate which source branch the fix is included in (for example,
4.2.x or 4.3.x). Don't close the bug yet.
Release
When a release is made which includes the bug fix, make sure the
bug is listed in the NEWS file. Once the release is made, fill in
the 'Fixed Release' field and close the bug.
File: find-maint.info, Node: Distributions, Next: Internationalisation, Prev: Bugs, Up: Top
10 Distributions
****************
Almost all GNU/Linux distributions include findutils, but only some of
them have a package maintainer who is a member of the mailing list.
Distributions don't often feed back patches to the
<bug-findutils AT gnu.org> list, but on the other hand many of their
patches relate only to standards for file locations and so forth, and
are therefore distribution specific. On an irregular basis I check the
current patches being used by one or two distributions, but the total
number of GNU/Linux distributions is large enough that we could not hope
to cover them all.
Often, bugs are raised against a distribution's bug tracker instead
of GNU's. Periodically (about every six months) I take a look at some
of the more accessible bug trackers to indicate which bugs have been
fixed upstream.
Many distributions include both findutils and the slocate package,
which provides a replacement 'locate'.
File: find-maint.info, Node: Internationalisation, Next: Security, Prev: Distributions, Up: Top
11 Internationalisation
***********************
Translation is essentially automated from the maintainer's point of
view. The TP mails the maintainer when a new PO file is available, and
we just download it and check it in. The 'bootstrap' script copies
'.po' files into the working tree. For more information, please see
<https://translationproject.org/domain/findutils.html>.
File: find-maint.info, Node: Security, Next: Making Releases, Prev: Internationalisation, Up: Top
12 Security
***********
See *note Security Considerations: (find)Security Considerations, for a
full description of the findutils approach to security considerations
and discussion of particular tools.
If someone reports a security bug publicly, we should fix this as
rapidly as possible. If necessary, this can mean issuing a fixed
release containing just the one bug fix. We try to avoid issuing
releases which include both significant security fixes and functional
changes.
Where someone reports a security problem privately, we generally try
to construct and test a patch without pushing the intermediate code to
the public repository.
Once everything has been tested, this allows us to make a release and
push the patch. The advantage of doing things this way is that we avoid
situations where people watching for git commits can figure out and
exploit a security problem before a fixed release is available.
It's important that security problems be fixed promptly, but don't
rush so much that things go wrong. Make sure the new release really
fixes the problem. It's usually best not to include functional changes
in your security-fix release.
If the security problem is serious, send an alert to
<vendor-sec AT lst.de>. The members of the list include most GNU/Linux
distributions. The point of doing this is to allow them to prepare to
release your security fix to their customers, once the fix becomes
available. Here is an example alert:-
GNU findutils heap buffer overrun (potential privilege escalation)
I. BACKGROUND
=============
GNU findutils is a set of programs which search for files on Unix-like
systems. It is maintained by the GNU Project of the Free Software
Foundation. For more information, see
<https://www.gnu.org/software/findutils>.
II. DESCRIPTION
===============
When GNU locate reads filenames from an old-format locate database,
they are read into a fixed-length buffer allocated on the heap.
Filenames longer than the 1026-byte buffer can cause a buffer overrun.
The overrunning data can be chosen by any person able to control the
names of filenames created on the local system. This will normally
include all local users, but in many cases also remote users (for
example in the case of FTP servers allowing uploads).
III. ANALYSIS
=============
Findutils supports three different formats of locate database, its
native format "LOCATE02", the slocate variant of LOCATE02, and a
traditional ("old") format that locate uses on other Unix systems.
When locate reads filenames from a LOCATE02 database (the default
format), the buffer into which data is read is automatically extended
to accommodate the length of the filenames.
This automatic buffer extension does not happen for old-format
databases. Instead a 1026-byte buffer is used. When a longer
pathname appears in the locate database, the end of this buffer is
overrun. The buffer is allocated on the heap (not the stack).
If the locate database is in the default LOCATE02 format, the locate
program does perform automatic buffer extension, and the program is
not vulnerable to this problem. The software used to build the
old-format locate database is not itself vulnerable to the same
attack.
Most installations of GNU findutils do not use the old database
format, and so will not be vulnerable.
IV. DETECTION
=============
Software
--------
All existing releases of findutils are affected.
Installations
-------------
To discover the longest path name on a given system, you can use the
following command (requires GNU findutils and GNU coreutils):
find / -print0 | tr -c '\0' 'x' | tr '\0' '\n' | wc -L
V. EXAMPLE
==========
This section includes a shell script which determines which of a list
of locate binaries is vulnerable to the problem. The shell script has
been tested only on glibc based systems having a mktemp binary.
NOTE: This script deliberately overruns the buffer in order to
determine if a binary is affected. Therefore running it on your
system may have undesirable effects. We recommend that you read the
script before running it.
#! /bin/sh
set +m
if vanilla_db="$(mktemp nicedb.XXXXXX)" ; then
if updatedb --prunepaths="" --old-format --localpaths="/tmp" \
--output="$@{vanilla_db@}" ; then
true
else
rm -f "$@{vanilla_db@}"
vanilla_db=""
echo "Failed to create old-format locate database; skipping the sanity checks" >&2
fi
fi
make_overrun_db() @{
# Start with a valid database
cat "$@{vanilla_db@}"
# Make the final entry really long
dd if=/dev/zero bs=1 count=1500 2>/dev/null | tr '\000' 'x'
@}
ulimit -c 0
usage() @{ echo "usage: $0 binary [binary...]" >&2; exit $1; @}
[ $# -eq 0 ] && usage 1
bad=""
good=""
ugly=""
if dbfile="$(mktemp nasty.XXXXXX)"
then
make_overrun_db > "$dbfile"
for locate ; do
ver="$locate = $("$locate" --version | head -1)"
if [ -z "$vanilla_db" ] || "$locate" -d "$vanilla_db" "" >/dev/null ; then
"$locate" -d "$dbfile" "" >/dev/null
if [ $? -gt 128 ] ; then
bad="$bad
vulnerable: $ver"
else
good="$good
good: $ver"
fi
else
# the regular locate failed
ugly="$ugly
buggy, may or may not be vulnerable: $ver"
fi
done
rm -f "$@{dbfile@}" "$@{vanilla_db@}"
# good: unaffected. bad: affected (vulnerable).
# ugly: doesn't even work for a normal old-format database.
echo "$good"
echo "$bad"
echo "$ugly"
else
exit 1
fi
VI. VENDOR RESPONSE
===================
The GNU project discovered the problem while 'locate' was being worked
on; this is the first public announcement of the problem.
The GNU findutils mantainer has issued a patch as p[art of this
announcement. The patch appears below.
A source release of findutils-4.2.31 will be issued on 2007-05-30.
That release will of course include the patch. The patch will be
committed to the public CVS repository at the same time. Public
announcements of the release, including a description of the bug, will
be made at the same time as the release.
A release of findutils-4.3.x will follow and will also include the
patch.
VII. PATCH
==========
This patch should apply to findutils-4.2.23 and later.
Findutils-4.2.23 was released almost two years ago.
Index: locate/locate.c
===================================================================
RCS file: /cvsroot/findutils/findutils/locate/locate.c,v
retrieving revision 1.58.2.2
diff -u -p -r1.58.2.2 locate.c
--- locate/locate.c 22 Apr 2007 16:57:42 -0000 1.58.2.2
+++ locate/locate.c 28 May 2007 10:18:16 -0000
@@@@ -124,9 +124,9 @@@@ extern int errno;
#include "locatedb.h"
#include <getline.h>
-#include "../gnulib/lib/xalloc.h"
-#include "../gnulib/lib/error.h"
-#include "../gnulib/lib/human.h"
+#include "xalloc.h"
+#include "error.h"
+#include "human.h"
#include "dirname.h"
#include "closeout.h"
#include "nextelem.h"
@@@@ -468,10 +468,36 @@@@ visit_justprint_unquoted(struct process_
return VISIT_CONTINUE;
@}
+static void
+toolong (struct process_data *procdata)
+@{
+ error (EXIT_FAILURE, 0,
+ _("locate database %s contains a "
+ "filename longer than locate can handle"),
+ procdata->dbfile);
+@}
+
+static void
+extend (struct process_data *procdata, size_t siz1, size_t siz2)
+@{
+ /* Figure out if the addition operation is safe before performing it. */
+ if (SIZE_MAX - siz1 < siz2)
+ @{
+ toolong (procdata);
+ @}
+ else if (procdata->pathsize < (siz1+siz2))
+ @{
+ procdata->pathsize = siz1+siz2;
+ procdata->original_filename = x2nrealloc (procdata->original_filename,
+ &procdata->pathsize,
+ 1);
+ @}
+@}
+
static int
visit_old_format(struct process_data *procdata, void *context)
@{
- register char *s;
+ register size_t i;
(void) context;
/* Get the offset in the path where this path info starts. */
@@@@ -479,20 +505,35 @@@@ visit_old_format(struct process_data *pr
procdata->count += getw (procdata->fp) - LOCATEDB_OLD_OFFSET;
else
procdata->count += procdata->c - LOCATEDB_OLD_OFFSET;
+ assert(procdata->count > 0);
- /* Overlay the old path with the remainder of the new. */
- for (s = procdata->original_filename + procdata->count;
+ /* Overlay the old path with the remainder of the new. Read
+ * more data until we get to the next filename.
+ */
+ for (i=procdata->count;
(procdata->c = getc (procdata->fp)) > LOCATEDB_OLD_ESCAPE;)
- if (procdata->c < 0200)
- *s++ = procdata->c; /* An ordinary character. */
- else
- @{
- /* Bigram markers have the high bit set. */
- procdata->c &= 0177;
- *s++ = procdata->bigram1[procdata->c];
- *s++ = procdata->bigram2[procdata->c];
- @}
- *s-- = '\0';
+ @{
+ if (procdata->c < 0200)
+ @{
+ /* An ordinary character. */
+ extend (procdata, i, 1u);
+ procdata->original_filename[i++] = procdata->c;
+ @}
+ else
+ @{
+ /* Bigram markers have the high bit set. */
+ extend (procdata, i, 2u);
+ procdata->c &= 0177;
+ procdata->original_filename[i++] = procdata->bigram1[procdata->c];
+ procdata->original_filename[i++] = procdata->bigram2[procdata->c];
+ @}
+ @}
+
+ /* Consider the case where we executed the loop body zero times; we
+ * still need space for the terminating null byte.
+ */
+ extend (procdata, i, 1u);
+ procdata->original_filename[i] = 0;
procdata->munged_filename = procdata->original_filename;
VIII. THANKS
============
Thanks to Rob Holland <rob AT inversepath.com> and Tavis Ormandy.
VIII. CVE INFORMATION
=====================
No CVE candidate number has yet been assigned for this vulnerability.
If someone provides one, I will include it in the public announcement
and change logs.
The original announcement above was sent out with a cleartext PGP
signature, of course, but that has been omitted from the example.
Once a fixed release is available, announce the new release using the
normal channels. Any CVE number assigned for the problem should be
included in the 'ChangeLog' and 'NEWS' entries. See
<https://cve.mitre.org/> for an explanation of CVE numbers.
File: find-maint.info, Node: Making Releases, Next: GNU Free Documentation License, Prev: Security, Up: Top
13 Making Releases
******************
This section will explain how to make a findutils release. For the time
being here is a terse description of the main steps:
1. Commit changes; make sure your working directory has no uncommitted
changes.
2. Update translation files; re-run bootstrap to download the newest
'.po' files.
3. Make sure compiler warnings would block the release; re-run
'configure' with the options '--enable-compiler-warnings
--enable-compiler-warnings-are-errors'.
4. Test; make sure that all changes you have made have tests, and that
the tests pass. Verify this with 'env RUN_EXPENSIVE_TESTS=yes make
distcheck'.
5. Bugs; make sure all Savannah bug entries fixed in this release are
marked as fixed in Savannah. Optionally close them too to save
duplicate work (otherwise, close them after the release is
uploaded).
6. Add new release in Savannah field values; see the 'Bugs > Edit
Field Values' menu item. Add a field value for the release you are
about to make so that users can report bugs in it.
7. Update version; make sure that the NEWS file is updated with the
new release number (and checked in).
8. Tag the release; findutils releases are tagged like this for
example: v4.5.5. You can create a tag with the a command like
this:
git tag -s -m "Findutils release X.Y.Z" vX.Y.Z
9. Build the release tarball; do this with 'make distcheck'. Copy the
tarball somewhere safe.
10. Merge; if the release (and signed tag) were made on a local
branch, merge the branch to your local master.
11. Push; push your master to origin/master.
12. Push the new release tag; assuming that the name of your remote is
'origin', this is:
git push origin tag vX.Y.Z
13. Prepare the upload and upload it. You can do this with
build-aux/gnupload --to ftp.gnu.org:findutils findutils-X.Y.Z.tar.xz
Use 'alpha.gnu.org:findutils' for an alpha or beta release. *Note
Automated FTP Uploads: (maintain)Automated FTP Uploads, for
detailed upload instructions.
14. Check the FTP upload worked; you can look for an email from the
robot or check the contents of the actual FTP site.
15. Make a release announcement; include an extract from the NEWS file
which explains what's changed. Announcements for test releases
should just go to <bug-findutils AT gnu.org>. Announcements for
stable releases should go to <info-gnu AT gnu.org> as well.
16. Post-release administrativa: add a new dummy release header in
NEWS:
'* Major changes in release ?.?.?, YYYY-MM-DD'
and update the 'old_NEWS_hash' in 'cfg.mk' with 'make
update-NEWS-hash'. Commit both changes.
17. Close bugs; any bugs recorded on Savannah which were fixed in this
release should now be marked as closed if there were not already.
Update the 'Fixed Release' field of these bugs appropriately and
make sure the 'Assigned to' field is populated.
File: find-maint.info, Node: GNU Free Documentation License, Prev: Making Releases, Up: Top
Appendix A GNU Free Documentation License
*****************************************
Version 1.3, 3 November 2008
Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
<https://fsf.org/>
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
0. PREAMBLE
The purpose of this License is to make a manual, textbook, or other
functional and useful document "free" in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it,
with or without modifying it, either commercially or
noncommercially. Secondarily, this License preserves for the
author and publisher a way to get credit for their work, while not
being considered responsible for modifications made by others.
This License is a kind of "copyleft", which means that derivative
works of the document must themselves be free in the same sense.
It complements the GNU General Public License, which is a copyleft
license designed for free software.
We have designed this License in order to use it for manuals for
free software, because free software needs free documentation: a
free program should come with manuals providing the same freedoms
that the software does. But this License is not limited to
software manuals; it can be used for any textual work, regardless
of subject matter or whether it is published as a printed book. We
recommend this License principally for works whose purpose is
instruction or reference.
1. APPLICABILITY AND DEFINITIONS
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that contains a notice placed by the copyright holder saying it can
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"Document", below, refers to any such manual or work. Any member
of the public is a licensee, and is addressed as "you". You accept
the license if you copy, modify or distribute the work in a way
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A "Modified Version" of the Document means any work containing the
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A "Secondary Section" is a named appendix or a front-matter section
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You may also lend copies, under the same conditions stated above,
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3. COPYING IN QUANTITY
If you publish printed copies (or copies in media that commonly
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If the required texts for either cover are too voluminous to fit
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If you publish or distribute Opaque copies of the Document
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through your agents or retailers) of that edition to the public.
It is requested, but not required, that you contact the authors of
the Document well before redistributing any large number of copies,
to give them a chance to provide you with an updated version of the
Document.
4. MODIFICATIONS
You may copy and distribute a Modified Version of the Document
under the conditions of sections 2 and 3 above, provided that you
release the Modified Version under precisely this License, with the
Modified Version filling the role of the Document, thus licensing
distribution and modification of the Modified Version to whoever
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the Modified Version:
A. Use in the Title Page (and on the covers, if any) a title
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History section of the Document). You may use the same title
as a previous version if the original publisher of that
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B. List on the Title Page, as authors, one or more persons or
entities responsible for authorship of the modifications in
the Modified Version, together with at least five of the
principal authors of the Document (all of its principal
authors, if it has fewer than five), unless they release you
from this requirement.
C. State on the Title page the name of the publisher of the
Modified Version, as the publisher.
D. Preserve all the copyright notices of the Document.
E. Add an appropriate copyright notice for your modifications
adjacent to the other copyright notices.
F. Include, immediately after the copyright notices, a license
notice giving the public permission to use the Modified
Version under the terms of this License, in the form shown in
the Addendum below.
G. Preserve in that license notice the full lists of Invariant
Sections and required Cover Texts given in the Document's
license notice.
H. Include an unaltered copy of this License.
I. Preserve the section Entitled "History", Preserve its Title,
and add to it an item stating at least the title, year, new
authors, and publisher of the Modified Version as given on the
Title Page. If there is no section Entitled "History" in the
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publisher of the Document as given on its Title Page, then add
an item describing the Modified Version as stated in the
previous sentence.
J. Preserve the network location, if any, given in the Document
for public access to a Transparent copy of the Document, and
likewise the network locations given in the Document for
previous versions it was based on. These may be placed in the
"History" section. You may omit a network location for a work
that was published at least four years before the Document
itself, or if the original publisher of the version it refers
to gives permission.
K. For any section Entitled "Acknowledgements" or "Dedications",
Preserve the Title of the section, and preserve in the section
all the substance and tone of each of the contributor
acknowledgements and/or dedications given therein.
L. Preserve all the Invariant Sections of the Document, unaltered
in their text and in their titles. Section numbers or the
equivalent are not considered part of the section titles.
M. Delete any section Entitled "Endorsements". Such a section
may not be included in the Modified Version.
N. Do not retitle any existing section to be Entitled
"Endorsements" or to conflict in title with any Invariant
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O. Preserve any Warranty Disclaimers.
If the Modified Version includes new front-matter sections or
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5. COMBINING DOCUMENTS
You may combine the Document with other documents released under
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by adding at the end of it, in parentheses, the name of the
original author or publisher of that section if known, or else a
unique number. Make the same adjustment to the section titles in
the list of Invariant Sections in the license notice of the
combined work.
In the combination, you must combine any sections Entitled
"History" in the various original documents, forming one section
Entitled "History"; likewise combine any sections Entitled
"Acknowledgements", and any sections Entitled "Dedications". You
must delete all sections Entitled "Endorsements."
6. COLLECTIONS OF DOCUMENTS
You may make a collection consisting of the Document and other
documents released under this License, and replace the individual
copies of this License in the various documents with a single copy
that is included in the collection, provided that you follow the
rules of this License for verbatim copying of each of the documents
in all other respects.
You may extract a single document from such a collection, and
distribute it individually under this License, provided you insert
a copy of this License into the extracted document, and follow this
License in all other respects regarding verbatim copying of that
document.
7. AGGREGATION WITH INDEPENDENT WORKS
A compilation of the Document or its derivatives with other
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storage or distribution medium, is called an "aggregate" if the
copyright resulting from the compilation is not used to limit the
legal rights of the compilation's users beyond what the individual
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License does not apply to the other works in the aggregate which
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If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half
of the entire aggregate, the Document's Cover Texts may be placed
on covers that bracket the Document within the aggregate, or the
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the whole aggregate.
8. TRANSLATION
Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section
4. Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
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translation of this License, and all the license notices in the
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include the original English version of this License and the
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this License or a notice or disclaimer, the original version will
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If a section in the Document is Entitled "Acknowledgements",
"Dedications", or "History", the requirement (section 4) to
Preserve its Title (section 1) will typically require changing the
actual title.
9. TERMINATION
You may not copy, modify, sublicense, or distribute the Document
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10. FUTURE REVISIONS OF THIS LICENSE
The Free Software Foundation may publish new, revised versions of
the GNU Free Documentation License from time to time. Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns. See
<https://www.gnu.org/licenses/>.
Each version of the License is given a distinguishing version
number. If the Document specifies that a particular numbered
version of this License "or any later version" applies to it, you
have the option of following the terms and conditions either of
that specified version or of any later version that has been
published (not as a draft) by the Free Software Foundation. If the
Document does not specify a version number of this License, you may
choose any version ever published (not as a draft) by the Free
Software Foundation. If the Document specifies that a proxy can
decide which future versions of this License can be used, that
proxy's public statement of acceptance of a version permanently
authorizes you to choose that version for the Document.
11. RELICENSING
"Massive Multiauthor Collaboration Site" (or "MMC Site") means any
World Wide Web server that publishes copyrightable works and also
provides prominent facilities for anybody to edit those works. A
public wiki that anybody can edit is an example of such a server.
A "Massive Multiauthor Collaboration" (or "MMC") contained in the
site means any set of copyrightable works thus published on the MMC
site.
"CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
license published by Creative Commons Corporation, a not-for-profit
corporation with a principal place of business in San Francisco,
California, as well as future copyleft versions of that license
published by that same organization.
"Incorporate" means to publish or republish a Document, in whole or
in part, as part of another Document.
An MMC is "eligible for relicensing" if it is licensed under this
License, and if all works that were first published under this
License somewhere other than this MMC, and subsequently
incorporated in whole or in part into the MMC, (1) had no cover
texts or invariant sections, and (2) were thus incorporated prior
to November 1, 2008.
The operator of an MMC Site may republish an MMC contained in the
site under CC-BY-SA on the same site at any time before August 1,
2009, provided the MMC is eligible for relicensing.
ADDENDUM: How to use this License for your documents
====================================================
To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and license
notices just after the title page:
Copyright (C) YEAR YOUR NAME.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
Texts. A copy of the license is included in the section entitled ``GNU
Free Documentation License''.
If you have Invariant Sections, Front-Cover Texts and Back-Cover
Texts, replace the "with...Texts." line with this:
with the Invariant Sections being LIST THEIR TITLES, with
the Front-Cover Texts being LIST, and with the Back-Cover Texts
being LIST.
If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.
If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of free
software license, such as the GNU General Public License, to permit
their use in free software.
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