SPDX and CVE documentation updates

Backporting from master the ones that are applicable to kirkstone.

(From yocto-docs rev: c10d65ef3bbdf4fe3abc03e3aef3d4ca8c2ad87f)

Signed-off-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Signed-off-by: Mikko Rapeli <mikko.rapeli@linaro.org>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 212 insertions, 79 deletions

diff --git a/documentation/dev-manual/common-tasks.rst b/documentation/dev-manual/common-tasks.rst
index 65f94432ab..1b91ada0a1 100644
--- a/documentation/dev-manual/common-tasks.rst
+++ b/documentation/dev-manual/common-tasks.rst
@@ -11426,39 +11426,6 @@ layers (recipes, configuration files, and so forth) enables you to meet
 your requirements to include the scripts to control compilation as well
 as any modifications to the original source.
 
-Providing spdx files
-~~~~~~~~~~~~~~~~~~~~~~~~~
-
-The spdx module has been integrated to a layer named meta-spdxscanner.
-meta-spdxscanner provides several kinds of scanner. If you want to enable
-this function, you have to follow the following steps:
-
-1. Add meta-spdxscanner layer into ``bblayers.conf``. 
-
-2. Refer to the README in meta-spdxscanner to setup the environment (e.g, 
-   setup a fossology server) needed for the scanner.
-
-3. Meta-spdxscanner provides several methods within the bbclass to create spdx files.
-   Please choose one that you want to use and enable the spdx task. You have to
-   add some config options in ``local.conf`` file in your :term:`Build
-   Directory`. Here is an example showing how to generate spdx files
-   during bitbake using the fossology-python.bbclass::
-
-      # Select fossology-python.bbclass.
-      INHERIT += "fossology-python"
-      # For fossology-python.bbclass, TOKEN is necessary, so, after setup a
-      # Fossology server, you have to create a token.
-      TOKEN = "eyJ0eXAiO..."
-      # The fossology server is necessary for fossology-python.bbclass.
-      FOSSOLOGY_SERVER = "http://xx.xx.xx.xx:8081/repo"
-      # If you want to upload the source code to a special folder:
-      FOLDER_NAME = "xxxx" //Optional
-      # If you don't want to put spdx files in tmp/deploy/spdx, you can enable:
-      SPDX_DEPLOY_DIR = "${DEPLOY_DIR}" //Optional
-
-For more usage information refer to :yocto_git:`the meta-spdxscanner repository
-</meta-spdxscanner/>`.
-
 Compliance Limitations with Executables Built from Static Libraries
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
@@ -11499,21 +11466,92 @@ the license from the fetched source::
 Checking for Vulnerabilities
 ============================
 
-Vulnerabilities in images
--------------------------
+Vulnerabilities in Poky and OE-Core
+-----------------------------------
 
 The Yocto Project has an infrastructure to track and address unfixed
 known security vulnerabilities, as tracked by the public
-`Common Vulnerabilities and Exposures (CVE) <https://en.wikipedia.org/wiki/Common_Vulnerabilities_and_Exposures>`__
+:wikipedia:`Common Vulnerabilities and Exposures (CVE) <Common_Vulnerabilities_and_Exposures>`
 database.
 
-To know which packages are vulnerable to known security vulnerabilities,
-add the following setting to your configuration::
+The Yocto Project maintains a `list of known vulnerabilities
+<https://autobuilder.yocto.io/pub/non-release/patchmetrics/>`__
+for packages in Poky and OE-Core, tracking the evolution of the number of
+unpatched CVEs and the status of patches. Such information is available for
+the current development version and for each supported release.
+
+Security is a process, not a product, and thus at any time, a number of security
+issues may be impacting Poky and OE-Core. It is up to the maintainers, users,
+contributors and anyone interested in the issues to investigate and possibly fix them by
+updating software components to newer versions or by applying patches to address them.
+It is recommended to work with Poky and OE-Core upstream maintainers and submit
+patches to fix them, see ":ref:`dev-manual/common-tasks:submitting a change to the yocto project`" for details.
+
+Vulnerability check at build time
+---------------------------------
+
+To enable a check for CVE security vulnerabilities using :ref:`cve-check <ref-classes-cve-check>` in the specific image
+or target you are building, add the following setting to your configuration::
 
    INHERIT += "cve-check"
 
-This way, at build time, BitBake will warn you about known CVEs
-as in the example below::
+The CVE database contains some old incomplete entries which have been
+deemed not to impact Poky or OE-Core. These CVE entries can be excluded from the
+check using build configuration::
+
+   include conf/distro/include/cve-extra-exclusions.inc
+
+With this CVE check enabled, BitBake build will try to map each compiled software component
+recipe name and version information to the CVE database and generate recipe and
+image specific reports. These reports will contain:
+
+-  metadata about the software component like names and versions
+
+-  metadata about the CVE issue such as description and NVD link
+
+-  for each software component, a list of CVEs which are possibly impacting this version
+
+-  status of each CVE: ``Patched``, ``Unpatched`` or ``Ignored``
+
+The status ``Patched`` means that a patch file to address the security issue has been
+applied. ``Unpatched`` status means that no patches to address the issue have been
+applied and that the issue needs to be investigated. ``Ignored`` means that after
+analysis, it has been deemed to ignore the issue as it for example affects
+the software component on a different operating system platform.
+
+After a build with CVE check enabled, reports for each compiled source recipe will be
+found in ``build/tmp/deploy/cve``.
+
+For example the CVE check report for the ``flex-native`` recipe looks like::
+
+   $ cat poky/build/tmp/deploy/cve/flex-native
+   LAYER: meta
+   PACKAGE NAME: flex-native
+   PACKAGE VERSION: 2.6.4
+   CVE: CVE-2016-6354
+   CVE STATUS: Patched
+   CVE SUMMARY: Heap-based buffer overflow in the yy_get_next_buffer function in Flex before 2.6.1 might allow context-dependent attackers to cause a denial of service or possibly execute arbitrary code via vectors involving num_to_read.
+   CVSS v2 BASE SCORE: 7.5
+   CVSS v3 BASE SCORE: 9.8
+   VECTOR: NETWORK
+   MORE INFORMATION: https://nvd.nist.gov/vuln/detail/CVE-2016-6354
+
+   LAYER: meta
+   PACKAGE NAME: flex-native
+   PACKAGE VERSION: 2.6.4
+   CVE: CVE-2019-6293
+   CVE STATUS: Ignored
+   CVE SUMMARY: An issue was discovered in the function mark_beginning_as_normal in nfa.c in flex 2.6.4. There is a stack exhaustion problem caused by the mark_beginning_as_normal function making recursive calls to itself in certain scenarios involving lots of '*' characters. Remote attackers could leverage this vulnerability to cause a denial-of-service.
+   CVSS v2 BASE SCORE: 4.3
+   CVSS v3 BASE SCORE: 5.5
+   VECTOR: NETWORK
+   MORE INFORMATION: https://nvd.nist.gov/vuln/detail/CVE-2019-6293
+
+For images, a summary of all recipes included in the image and their CVEs is also
+generated in textual and JSON formats. These ``.cve`` and ``.json`` reports can be found
+in the ``tmp/deploy/images`` directory for each compiled image.
+
+At build time CVE check will also throw warnings about ``Unpatched`` CVEs::
 
    WARNING: flex-2.6.4-r0 do_cve_check: Found unpatched CVE (CVE-2019-6293), for more information check /poky/build/tmp/work/core2-64-poky-linux/flex/2.6.4-r0/temp/cve.log
    WARNING: libarchive-3.5.1-r0 do_cve_check: Found unpatched CVE (CVE-2021-36976), for more information check /poky/build/tmp/work/core2-64-poky-linux/libarchive/3.5.1-r0/temp/cve.log
@@ -11522,21 +11560,46 @@ It is also possible to check the CVE status of individual packages as follows::
 
    bitbake -c cve_check flex libarchive
 
-Note that OpenEmbedded-Core keeps a list of known unfixed CVE issues which can
-be ignored. You can pass this list to the check as follows::
+Fixing CVE product name and version mappings
+--------------------------------------------
+
+By default, :ref:`cve-check <ref-classes-cve-check>` uses the recipe name :term:`BPN` as CVE
+product name when querying the CVE database. If this mapping contains false positives, e.g.
+some reported CVEs are not for the software component in question, or false negatives like
+some CVEs are not found to impact the recipe when they should, then the problems can be
+in the recipe name to CVE product mapping. These mapping issues can be fixed by setting
+the :term:`CVE_PRODUCT` variable inside the recipe. This defines the name of the software component in the
+upstream `NIST CVE database <https://nvd.nist.gov/>`__.
 
-   bitbake -c cve_check libarchive -R conf/distro/include/cve-extra-exclusions.inc
+The variable supports using vendor and product names like this::
 
-Enabling vulnerabily tracking in recipes
-----------------------------------------
+   CVE_PRODUCT = "flex_project:flex"
 
-The :term:`CVE_PRODUCT` variable defines the name used to match the recipe name
-against the name in the upstream `NIST CVE database <https://nvd.nist.gov/>`__.
+In this example the vendor name used in the CVE database is ``flex_project`` and the
+product is ``flex``. With this setting the ``flex`` recipe only maps to this specific
+product and not products from other vendors with same name ``flex``.
 
-Editing recipes to fix vulnerabilities
---------------------------------------
+Similarly, when the recipe version :term:`PV` is not compatible with software versions used by
+the upstream software component releases and the CVE database, these can be fixed using
+the :term:`CVE_VERSION` variable.
+
+Note that if the CVE entries in the NVD database contain bugs or have missing or incomplete
+information, it is recommended to fix the information there directly instead of working
+around the issues possibly for a long time in Poky and OE-Core side recipes. Feedback to
+NVD about CVE entries can be provided through the `NVD contact form <https://nvd.nist.gov/info/contact-form>`__.
+
+Fixing vulnerabilities in recipes
+---------------------------------
+
+If a CVE security issue impacts a software component, it can be fixed by updating to a newer
+version of the software component or by applying a patch. For Poky and OE-Core master branches, updating
+to a newer software component release with fixes is the best option, but patches can be applied
+if releases are not yet available.
 
-To fix a given known vulnerability, you need to add a patch file to your recipe. Here's
+For stable branches, it is preferred to apply patches for the issues. For some software
+components minor version updates can also be applied if they are backwards compatible.
+
+Here is an example of fixing CVE security issues with patch files,
 an example from the :oe_layerindex:`ffmpeg recipe</layerindex/recipe/47350>`::
 
    SRC_URI = "https://www.ffmpeg.org/releases/${BP}.tar.xz \
@@ -11548,31 +11611,21 @@ an example from the :oe_layerindex:`ffmpeg recipe</layerindex/recipe/47350>`::
               file://fix-CVE-2020-22033-CVE-2020-22019.patch \
               file://fix-CVE-2021-33815.patch \
 
-The :ref:`cve-check <ref-classes-cve-check>` class defines two ways of
-supplying a patch for a given CVE. The first
-way is to use a patch filename that matches the below pattern::
-
-   cve_file_name_match = re.compile(".*([Cc][Vv][Ee]\-\d{4}\-\d+)")
-
-As shown in the example above, multiple CVE IDs can appear in a patch filename,
-but the :ref:`cve-check <ref-classes-cve-check>` class will only consider
-the last CVE ID in the filename as patched.
-
-The second way to recognize a patched CVE ID is when a line matching the
-below pattern is found in any patch file provided by the recipe::
+A good practice is to include the CVE identifier in both the patch file name
+and inside the patch file commit message using the format::
 
-  cve_match = re.compile("CVE:( CVE\-\d{4}\-\d+)+")
+   CVE: CVE-2020-22033
 
-This allows a single patch file to address multiple CVE IDs at the same time.
+CVE checker will then capture this information and change the CVE status to ``Patched``
+in the generated reports.
 
-Of course, another way to fix vulnerabilities is to upgrade to a version
-of the package which is not impacted, typically a more recent one.
-The NIST database knows which versions are vulnerable and which ones
-are not.
+If analysis shows that the CVE issue does not impact the recipe due to configuration, platform,
+version or other reasons, the CVE can be marked as ``Ignored`` using the :term:`CVE_CHECK_IGNORE` variable.
+As mentioned previously, if data in the CVE database is wrong, it is recommend to fix those
+issues in the CVE database directly.
 
-Last but not least, you can choose to ignore vulnerabilities through
-the :term:`CVE_CHECK_SKIP_RECIPE` and :term:`CVE_CHECK_IGNORE`
-variables.
+Recipes can be completely skipped by CVE check by including the recipe name in
+the :term:`CVE_CHECK_SKIP_RECIPE` variable.
 
 Implementation details
 ----------------------
@@ -11589,24 +11642,104 @@ file. The found CVE IDs are also considered as patched.
 Then, the code looks up all the CVE IDs in the NIST database for all the
 products defined in :term:`CVE_PRODUCT`. Then, for each found CVE:
 
- - If the package name (:term:`PN`) is part of
-   :term:`CVE_CHECK_SKIP_RECIPE`, it is considered as patched.
+-  If the package name (:term:`PN`) is part of
+   :term:`CVE_CHECK_SKIP_RECIPE`, it is considered as ``Patched``.
 
- - If the CVE ID is part of :term:`CVE_CHECK_IGNORE`, it is
-   considered as patched too.
+-  If the CVE ID is part of :term:`CVE_CHECK_IGNORE`, it is
+   set as ``Ignored``.
 
- - If the CVE ID is part of the patched CVE for the recipe, it is
-   already considered as patched.
+-  If the CVE ID is part of the patched CVE for the recipe, it is
+   already considered as ``Patched``.
 
- - Otherwise, the code checks whether the recipe version (:term:`PV`)
+-  Otherwise, the code checks whether the recipe version (:term:`PV`)
    is within the range of versions impacted by the CVE. If so, the CVE
-   is considered as unpatched.
+   is considered as ``Unpatched``.
 
 The CVE database is stored in :term:`DL_DIR` and can be inspected using
 ``sqlite3`` command as follows::
 
    sqlite3 downloads/CVE_CHECK/nvdcve_1.1.db .dump | grep CVE-2021-37462
 
+When analyzing CVEs, it is recommended to:
+
+-  study the latest information in `CVE database <https://nvd.nist.gov/vuln/search>`__.
+
+-  check how upstream developers of the software component addressed the issue, e.g.
+   what patch was applied, which upstream release contains the fix.
+
+-  check what other Linux distributions like `Debian <https://security-tracker.debian.org/tracker/>`__
+   did to analyze and address the issue.
+
+-  follow security notices from other Linux distributions.
+
+-  follow public `open source security mailing lists <https://oss-security.openwall.org/wiki/mailing-lists>`__ for
+   discussions and advance notifications of CVE bugs and software releases with fixes.
+
+Creating a Software Bill of Materials
+=====================================
+
+Once you are able to build an image for your project, once the licenses for
+each software component are all identified (see
+":ref:`dev-manual/common-tasks:working with licenses`") and once vulnerability
+fixes are applied (see ":ref:`dev-manual/common-tasks:checking
+for vulnerabilities`"), the OpenEmbedded build system can generate
+a description of all the components you used, their licenses, their dependencies,
+the changes that were applied and the known vulnerabilities that were fixed.
+
+This description is generated in the form of a *Software Bill of Materials*
+(:term:`SBOM`), using the :term:`SPDX` standard.
+
+When you release software, this is the most standard way to provide information
+about the Software Supply Chain of your software image and SDK. The
+:term:`SBOM` tooling is often used to ensure open source license compliance by
+providing the license texts used in the product which legal departments and end
+users can read in standardized format.
+
+:term:`SBOM` information is also critical to performing vulnerability exposure
+assessments, as all the components used in the Software Supply Chain are listed.
+
+The OpenEmbedded build system doesn't generate such information by default.
+To make this happen, you must inherit the
+:ref:`create-spdx <ref-classes-create-spdx>` class from a configuration file::
+
+   INHERIT += "create-spdx"
+
+You then get :term:`SPDX` output in JSON format as an
+``IMAGE-MACHINE.spdx.json`` file in ``tmp/deploy/images/MACHINE/`` inside the
+:term:`Build Directory`.
+
+This is a toplevel file accompanied by an ``IMAGE-MACHINE.spdx.index.json``
+containing an index of JSON :term:`SPDX` files for individual recipes, together
+with an ``IMAGE-MACHINE.spdx.tar.zst`` compressed archive containing all such
+files.
+
+The :ref:`create-spdx <ref-classes-create-spdx>` class offers options to include
+more information in the output :term:`SPDX` data, such as adding compressed
+archives of the files in the generated target packages
+(:term:`SPDX_ARCHIVE_PACKAGED`), adding a description of the source files
+handled by the target recipes (:term:`SPDX_INCLUDE_SOURCES`) and adding archives
+of these source files themselves (:term:`SPDX_ARCHIVE_SOURCES`).
+
+Though the toplevel :term:`SPDX` output is available in
+``tmp/deploy/images/MACHINE/`` inside the :term:`Build Directory`, ancillary
+generated files are available in ``tmp/deploy/spdx/MACHINE`` too, such as:
+
+-  The individual :term:`SPDX` JSON files in the ``IMAGE-MACHINE.spdx.tar.zst``
+   archive.
+
+-  Compressed archives of the files in the generated target packages,
+   in ``packages/packagename.tar.zst`` (when :term:`SPDX_ARCHIVE_PACKAGED`
+   is set).
+
+-  Compressed archives of the source files used to build the host tools
+   and the target packages in ``recipes/recipe-packagename.tar.zst``
+   (when :term:`SPDX_ARCHIVE_SOURCES` is set). Those are needed to fulfill
+   "source code access" license requirements.
+
+See the `tools page <https://spdx.dev/resources/tools/>`__ on the :term:`SPDX`
+project website for a list of tools to consume and transform the :term:`SPDX`
+data generated by the OpenEmbedded build system.
+
 Using the Error Reporting Tool
 ==============================