[v2] security-manual: Add information about how security is handled in builds

We have no information about how security is handled within the builds
themselves. Start to document this.

[YOCTO #16102]

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
---
 .../build-process-security.rst                | 49 +++++++++++++++++++
 documentation/security-manual/index.rst       |  1 +
 2 files changed, 50 insertions(+)
 create mode 100644 documentation/security-manual/build-process-security.rst

On Tue, 11 Aug 2026, Richard Purdie via lists.yoctoproject.org wrote:

> We have no information about how security is handled within the builds
> themselves. Start to document this.
>
> [YOCTO #16102]
>
> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
> ---
>  .../build-process-security.rst                | 49 +++++++++++++++++++
>  documentation/security-manual/index.rst       |  1 +
>  2 files changed, 50 insertions(+)
>  create mode 100644 documentation/security-manual/build-process-security.rst
>
> diff --git a/documentation/security-manual/build-process-security.rst b/documentation/security-manual/build-process-security.rst
> new file mode 100644
> index 000000000..1335e1d08
> --- /dev/null
> +++ b/documentation/security-manual/build-process-security.rst
> @@ -0,0 +1,49 @@
> +.. SPDX-License-Identifier: CC-BY-SA-2.0-UK
> +
> +**********************
> +Build Process Security
> +**********************
> +
> +The :term:`OpenEmbedded Build System` is used to run the builds and careful
> +consideration has gone into 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.
> +
> +   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

                                  significant

> +   contamination of the output but it is certainly possible, especially maliciously.
> +
> +   See the :ref:`system-requirements-supported-distros` section of the Yocto
> +   Project Reference Manual for more information on supported host distributions.
> +
> +-  The builds assume :term:`DL_DIR` is a safe location. Once things enter that
> +   location there are not repeatedly re-verified. A user could edit the git trees or
               ^^^^
               they?

> +   tarballs there in ways the build might not detect.
> +
> +-  The builds assume things from :term:`SSTATE_DIR` or from a configured sstate mirror

  The catch-all word "things" in various places should be replaced by
a more specific phrase relevant to what is being referred to.

> +   are safe (with :doc:`signature checks </security-manual/sstate-signing>` if configured).
> +
> +-  The core build tool, :term:`BitBake`, is a execution engine and will execute code both
> +   during builds and when parsing recipes. This is not a security issue, it is an
> +   essential part of it's function and purpose.
> +
> +-  :term:`OpenEmbedded-Core (OE-Core)` is well tested for reproducibility issues but other
> +   layers and their recipes and code may not be as well tested. Those reproducibility tests
> +   are 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

            set up

> +   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..ab1ef445c 100644
> --- a/documentation/security-manual/index.rst
> +++ b/documentation/security-manual/index.rst
> @@ -11,6 +11,7 @@ Yocto Project Security Manual
>     :numbered:
>
>     intro
> +   build-process-security
>     securing-images
>     vulnerabilities
>     read-only-rootfs
>