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Signed-off-by: Leah Rowe <leah@libreboot.org>
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Leah Rowe
2026-03-26 05:13:46 +00:00
parent fe259bd042
commit 4d4285e63c
1 changed files with 31 additions and 26 deletions
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util/libreboot-utils/README.md
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@@ -1,14 +1,34 @@
Mkhtemp - Hardened mktemp
-------------------------
Create new files and directories randomly as determined by
the user's TMPDIR, or fallback. Portable to Linux and BSD.
Just like normal mktemp, but hardened.
NOTE: on Linux, it uses openat2 for i/o, which is more
secure. BSDs only have the older openat for now, so
mkhtemp uses that there. However, even there, there are
several ways in which mkhtemp is better than every
previous mktemp.
Create new files and directories randomly as determined by
the user's TMPDIR, or fallback. These temporary files and
directories can be generated from e.g. shell scripts, running
mkhtemp. There is also a library that you could use in your
program. Portable to Linux and BSD. **WORK IN PROGRESS.
This is a very new project. Expect bugs - a stable release
will be announced, when the code has matured.**
A brief summary of *why* mkhtemp is more secure (more
details provided later in this readme - please also
read the source code):
Detect and mitigate symlink attacks, directory access
race conditions, unsecure TMPDIR (e.g. bad enforce sticky
bit policy on world writeable dirs), implement in user
space a virtual sandbox (block directory escape and resolve
paths by walking from `/` manually instead of relying on
the kernel/system), voluntarily error out (halt all
operation) if accessing files you don't own - that's why
sticky bits are checked for example, even when you're root.
Mkhtemp is designed to be the most secure implementation
possible, of mktemp, offering a heavy amount of hardening
over traditional mktemp.
i.e. please read the source code
```
/*
@@ -18,6 +38,10 @@ previous mktemp.
* when it's ready. Read the src.
*
* What you see is an early beta.
*
* Please do not merge this in
* your Linux distro package repo
* yet (unless maybe you're AUR).
*/
```
@@ -51,25 +75,6 @@ development. A stable release will be announced when ready.
### What does mkhtemp do differently?
#### Short version:
Detect and mitigate symlink attacks, directory access
race conditions, unsecure TMPDIR (e.g. bad enforce sticky
bit policy on world writeable dirs), implement in user
space a virtual sandbox (block directory escape and resolve
paths by walking from `/` manually instead of relying on
the kernel/system), voluntarily error out (halt all
operation) if accessing files you don't own - that's why
sticky bits are checked for example, even when you're root.
Mkhtemp is designed to be the most secure implementation
possible, of mktemp, offering a heavy amount of hardening
over traditional mktemp.
i.e. please read the source code
#### Long version:
This software attempts to provide mitigation against
several TOCTOU-based
attacks e.g. directory rename / symlink / re-mount, and