Re: [docs] [PATCH] security-manual: Add information about how security is handled in builds

["Antonin Godard" <antonin.godard@bootlin.com>]

Hi,

On Fri Aug 7, 2026 at 6:43 PM CEST, Richard Purdie via lists.yoctoproject.org wrote:
> We have no information about how security is handled within the builds
> themselves. Start to document this.
>
> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
> ---
>  .../security-manual/build-security.rst        | 41 +++++++++++++++++++
>  documentation/security-manual/index.rst       |  1 +
>  2 files changed, 42 insertions(+)
>  create mode 100644 documentation/security-manual/build-security.rst
>
> diff --git a/documentation/security-manual/build-security.rst b/documentation/security-manual/build-security.rst
> new file mode 100644
> index 000000000..5f15d5f64
> --- /dev/null
> +++ b/documentation/security-manual/build-security.rst
> @@ -0,0 +1,41 @@
> +.. SPDX-License-Identifier: CC-BY-SA-2.0-UK
> +
> +**************
> +Build Security

I suggest renaming it to "OpenEmbedded Build System Security", as "Build" alone
could be interpreted in many different ways, including builds for specific
software components, etc.

> +**************
> +
> +OpenEmbedded is used to run the builds and careful consideration has gone into

When you say "OpenEmbedded" I guess you mean the community? Or the build system?

We have a :term:`OpenEmbedded Build System` that could be used here if relevant.

> +how it does this with the aim of being both secure and reproducible. Like any
> +system, it does need to be used carefully and in keeping with the design for
> +that to be true. Users of the system should consider that:
> +
> +-  The builds generally aim for any input into the build process being verified in
> +   some form. For source code tarballs, these would have a checksum. Git source
> +   trees would have a specific git revision. Metadata would also usually be
> +   under source control and also have revisions.

Add a link to our fetching documentation here?

"""
See the :doc:`bitbake:bitbake-user-manual/bitbake-user-manual-fetching` section
of the BitBake User Manual for more information.
"""

> +
> +-  Some elements that can influence the build are not verified. It is assumed
> +   that the operating system running the system is secure and of a known setup and
> +   version. The system goes to signififant lengths to isolate against host
> +   contamination of the output but it is certainly possible, especially malicously.

typo: maliciously

Link to our supported distros here?

"""
See the :ref:`system-requirements-supported-distros` section of the Yocto
Project Reference Manual for more information on supported host distributions.
"""

> +
> +-  The builds assume DL_DIR is a safe location. Once things enter that location

s/DL_DIR/:term:`DL_DIR`/

> +   there are not repeatedly re-verified. A user could edit the git trees or
> +   tarballs there in ways the build might not detect.

I guess this will be better detailed with
https://bugzilla.yoctoproject.org/show_bug.cgi?id=16102. Maybe the documentation
coming from this bug should be linked here then.

> +
> +-  The builds assume things from SSTATE_DIR or from a configured sstate mirror

s/SSTATE_DIR/:term:`SSTATE_DIR`/

s/sstate mirror/:doc:`sstate mirror </dev-manual/sstate-mirrors-setup>`

> +   are safe (with signature checks if configured).

s/signature checks/:doc:`signature checks </security-manual/sstate-signing>`/

> +-  The core build tool, BitBake is a execution engine and will execute code both

"""
The core build tool, :term:`BitBake`, ...
"""

> +   during builds and when parsing recipes. This is not a security issue, it is an
> +   essential part of it's function and purpose.
> +
> +-  OE-Core is well tested for reproducibility issues but other layers and their

s/OE-Core/:term:`OpenEmbedded-Core (OE-Core)`/

> +   recipes and code may not be as well tested. Those reproducilbity tests are

typo: reproducibility

> +   available for others to run against their own layers and code.
> +
> +-  The builds combine many different software components and we take it on trust
> +   that there aren't issues in those code bases. We'd recommend build environments
> +   being setup in such a way that if such an issue were ever discovered, which at
> +   some point could happen, the build environments themselves could be simply
> +   destroyed and rebuilt cleanly, i.e. they're disposable.
> diff --git a/documentation/security-manual/index.rst b/documentation/security-manual/index.rst
> index a767cd9c6..328265be2 100644
> --- a/documentation/security-manual/index.rst
> +++ b/documentation/security-manual/index.rst
> @@ -11,6 +11,7 @@ Yocto Project Security Manual
>     :numbered:
>  
>     intro
> +   build-security
>     securing-images
>     vulnerabilities
>     read-only-rootfs

Thanks,
Antonin