Re: [PATCH 3/3] oe.gpg_sign: support obs-signd

Mark Hatle
2016-01-11T16:33:31Z

On 1/11/16 10:13 AM, Markus Lehtonen wrote:
> Implement support for remote signing using obs-signd. It is now possible
> to sign both RPM packages and package feeds with this method. The user
> just needs to set RPM_GPG_BACKEND and/or PACKAGE_FEED_GPG_BACKEND
> variables to 'obssign' in the bitbake config. Of course, in addition,
> one needs to setup the signing server and the configure the 'sign'
> client command on the build host. The *_PASSPHRASE_FILE settings are not
> used when the obssign backend is enabled.
>
> [YOCTO #8755]
>
> Signed-off-by: Markus Lehtonen <markus.lehtonen@linux.intel.com>
> ---
> meta/classes/sign_package_feed.bbclass | 5 +++-
> meta/classes/sign_rpm.bbclass | 5 +++-
> meta/lib/oe/gpg_sign.py | 48 ++++++++++++++++++++++++++++++++++
> 3 files changed, 56 insertions(+), 2 deletions(-)
>
> diff --git a/meta/classes/sign_package_feed.bbclass b/meta/classes/sign_package_feed.bbclass
> index d5df8af..953fa85 100644
> --- a/meta/classes/sign_package_feed.bbclass
> +++ b/meta/classes/sign_package_feed.bbclass
> @@ -24,7 +24,10 @@ PACKAGE_FEED_GPG_BACKEND ?= 'local'
>
> python () {
> # Check sanity of configuration
> - for var in ('PACKAGE_FEED_GPG_NAME', 'PACKAGE_FEED_GPG_PASSPHRASE_FILE'):
> + required = ['PACKAGE_FEED_GPG_NAME']
> + if d.getVar('PACKAGE_FEED_GPG_BACKEND', True) != 'obssign':
> + required.append('PACKAGE_FEED_GPG_PASSPHRASE_FILE')
> + for var in required:
> if not d.getVar(var, True):
> raise_sanity_error("You need to define %s in the config" % var, d)
>
> diff --git a/meta/classes/sign_rpm.bbclass b/meta/classes/sign_rpm.bbclass
> index 8bcabee..8be1c35 100644
> --- a/meta/classes/sign_rpm.bbclass
> +++ b/meta/classes/sign_rpm.bbclass
> @@ -23,7 +23,10 @@ RPM_GPG_BACKEND ?= 'local'
>
> python () {
> # Check configuration
> - for var in ('RPM_GPG_NAME', 'RPM_GPG_PASSPHRASE_FILE'):
> + required = ['RPM_GPG_NAME']
> + if d.getVar('RPM_GPG_BACKEND', True) != 'obssign':
> + required.append('RPM_GPG_PASSPHRASE_FILE')
> + for var in required:
> if not d.getVar(var, True):
> raise_sanity_error("You need to define %s in the config" % var, d)
>
> diff --git a/meta/lib/oe/gpg_sign.py b/meta/lib/oe/gpg_sign.py
> index 55abad8..d8ab816 100644
> --- a/meta/lib/oe/gpg_sign.py
> +++ b/meta/lib/oe/gpg_sign.py
> @@ -66,11 +66,59 @@ class LocalSigner(object):
> (input_file, output))
>
>
> +class ObsSigner(object):
> + """Class for handling signing with obs-signd"""
> + def __init__(self, keyid):
> + self.keyid = keyid
> + self.rpm_bin = bb.utils.which(os.getenv('PATH'), "rpm")
> +
> + def export_pubkey(self, output_file):
> + """Export GPG public key to a file"""
> + cmd = "sign -u '%s' -p" % self.keyid
> + status, output = oe.utils.getstatusoutput(cmd)
> + if status:
> + raise bb.build.FuncFailed('Failed to export gpg public key (%s): %s' %
> + (self.keyid, output))
> + with open(output_file, 'w') as fobj:
> + fobj.write(output)
> + fobj.write('\n')
> +
> + def sign_rpms(self, files):
> + """Sign RPM files"""
> + import pexpect
> +
> + # Remove existing signatures
> + cmd = "%s --delsign %s" % (self.rpm_bin, ' '.join(files))

Why are you removing existing signatures? I believe for many cases this is
actually incorrect.

RPM (5) has the ability to have an endless number of signatures within a given
package. The package SHOULD included the internal non-repudiable signature...

(to refresh memory) all RPM 5 packages include an internal non-repudiable
signature. Think of this as an extended md5sum, sha256sum, etc. It doesn't
change that a package is 'authentic' in any way (often the purpose of signatures
like what this code is doing), but instead keeps a high reliability way to sign
and verify the package is signed properly.

This is used for validation if the system doing the install does not have the
public key that the package was signed with.

... as well as one or more repudiable signatures that can be used to verify that
it's "authentic" in some way. A system could very easily have OSV, OEM, and ISV
keys install on them. You can program RPM in such a way that it will refused to
install packages with unknown authentication keys or the non-repudiable key as well.

So, I believe running delsign is wrong. If the obs-signd can't handle ADDING
signatures to packages, then I'd say it is broken and should be fixed in some
way -- or at least the signature deletion code should be optional.

> + status, output = oe.utils.getstatusoutput(cmd)
> + if status:
> + raise bb.build.FuncFailed("Failed to remove RPM signatures: %s" %
> + output)
> + # Sign packages
> + cmd = "sign -u '%s' -r %s" % (self.keyid, ' '.join(files))
> + status, output = oe.utils.getstatusoutput(cmd)
> + if status:
> + raise bb.build.FuncFailed("Failed to sign RPM packages: %s" %
> + output)
> +
> + def detach_sign(self, input_file):
> + """Create a detached signature of a file"""
> + cmd = "sign -u '%s' -d %s" % (self.keyid, input_file)
> + status, output = oe.utils.getstatusoutput(cmd)
> + if status:
> + raise bb.build.FuncFailed("Failed to create signature for '%s': %s" %
> + (input_file, output))
> +
> +
> def get_signer(d, backend, keyid, passphrase_file):
> """Get signer object for the specified backend"""
> # Use local signing by default
> if backend == 'local':
> return LocalSigner(d, keyid, passphrase_file)
> + elif backend == 'obssign':
> + if passphrase_file:
> + bb.note("GPG passphrase file setting not used when 'obssign' "
> + "backend is used.")
> + return ObsSigner(keyid)
> else:
> bb.fatal("Unsupported signing backend '%s'" % backend)
>
>