[PATCH v4] binman: x509_cert: add PKCS#11/HSM signing support

[Simon Glass]

Hi Sergio,

On 2026-05-13T17:56:34, Sergio Prado <sergio.prado at e-labworks.com> wrote:
> binman: x509_cert: add PKCS#11/HSM signing support
>
> Allow X509 certificates used for TI K3 secure boot to be signed via an
> HSM using the PKCS#11 standard, so that the private key never leaves
> the hardware token.
>
> A new make variable BINMAN_X509_KEY_URI is introduced. When set, it is
> forwarded to binman as the x509-key-uri entry argument, overriding the
> keyfile property at signing time:
>
>   make BINMAN_X509_KEY_URI="pkcs11:token=mytk;object=mykey;type=private" \
>        OPENSSL_CONF=/path/to/openssl.cnf
>
> The OpenSSL pkcs11 provider or engine and the PKCS#11 module must be
> configured externally via openssl.cnf. Two URI forms are supported on
> OpenSSL 3.x:
>
>  - Provider path: pkcs11:token=...;object=...;type=private
>  - Engine path:   org.openssl.engine:pkcs11:pkcs11:token=...;...
>
> [...]
>
> Makefile                            |   1 +
>  tools/binman/binman.rst             |  50 +++++++++++++++
>  tools/binman/etype/ti_secure.py     |   5 ++
>  tools/binman/etype/ti_secure_rom.py |   5 ++
>  tools/binman/etype/x509_cert.py     |  52 ++++++++++++++--
>  tools/binman/ftest.py               | 118 ++++++++++++++++++++++++++++++++++++
>  6 files changed, 226 insertions(+), 5 deletions(-)

Reviewed-by: Simon Glass <sjg at chromium.org>

Thoughts below

> diff --git a/tools/binman/ftest.py b/tools/binman/ftest.py
> @@ -6905,6 +6906,123 @@ fdt         fdtmap                Extract the devicetree blob from the fdtmap
> +        # Find the softhsm2 library path via p11-kit
> +        p11_kit_config = configparser.ConfigParser()
> +        p11_kit_config.read_string(tools.run('p11-kit', 'print-config'))
> +        softhsm2_lib = p11_kit_config.get('softhsm2', 'module', fallback=None)
> +        if softhsm2_lib is None:
> +            self.skipTest('softhsm2 module not found in p11-kit config')
> +
> +        # Find the OpenSSL pkcs11 provider module via the modules dir
> +        # reported by 'openssl version -m'. This handles multiarch paths
> +        # like /usr/lib/x86_64-linux-gnu/ossl-modules on Debian/Ubuntu,
> +        # which OPENSSLDIR does not point at.
> +        m = re.search(r'MODULESDIR: '([^']+)"',
> +                      tools.run('openssl', 'version', '-m'))

You construct the bintool instances above (openssl, softhsm2_util,
pkcs11_tool, p11_kit) but then call tools.run() directly. Commit
08bcf962c5f routed the existing eight call sites through
<bintool>.run_cmd(), at Quentin's suggestion. Can you do the same
here? - p11_kit.run_cmd('print-config'), openssl.run_cmd('version',
'-m'), and the softhsm2_util.run_cmd()/pkcs11_tool.run_cmd() calls
below.

> diff --git a/tools/binman/etype/x509_cert.py b/tools/binman/etype/x509_cert.py
> @@ -168,3 +198,15 @@ class Entry_x509_cert(Entry_collection):
> +    @staticmethod
> +    def _build_pkcs11_key(uri, pin):
> +        """Append pin-value to a PKCS#11 URI when a PIN is provided.
> +
> +        Uses '&' as separator if the URI already contains '?', else '?'.
> +        Returns the URI unchanged when pin is None or empty.
> +        """
> +        if not pin:
> +            return uri
> +        sep = '&' if '?' in uri else '?'
> +        return f'{uri}{sep}pin-value={pin}'

The PIN is concatenated raw, but RFC 7512 says the query component is
percent-encoded.Wouldn't it be better to use urllib.parse.quote() on
the PIN before appending? You could add a simple test for that.

> diff --git a/tools/binman/etype/x509_cert.py b/tools/binman/etype/x509_cert.py
> @@ -18,7 +18,25 @@ class Entry_x509_cert(Entry_collection):
>      """An entry which contains an X509 certificate
>
>      Properties / Entry arguments:
> -        - content: List of phandles to entries to sign
> +        - content: List of phandles to entries to sign.
> +        - keyfile: Filename of the PEM key file used to sign the binary.
> +        - x509-key-uri: URI of a key to use for signing instead of the PEM

...
> +        - cert-ca: Common Name (CN) embedded in the certificate. Used when
> +            generating a generic x509 certificate.
> +        - cert-revision-int: Integer certificate revision number. Used when
> +            generating a generic x509 certificate. Defaults to 0.
> +        - sw-rev: Software revision number embedded in the certificate by
> +            the sysfw/rom variants used by the TI K3 secure boot subclasses.
> +            Defaults to 1.

Ideally this would go into a separate preparatory commit.

Regards,
Simon