linux-kernel - Re: [PATCH v5 5/6] KEYS: CA link restriction

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Date:   Mon, 20 Mar 2023 17:35:05 +0000
From:   Eric Snowberg <eric.snowberg@...cle.com>
To:     Jarkko Sakkinen <jarkko@...nel.org>
CC:     Mimi Zohar <zohar@...ux.ibm.com>,
        David Howells <dhowells@...hat.com>,
        David Woodhouse <dwmw2@...radead.org>,
        "herbert@...dor.apana.org.au" <herbert@...dor.apana.org.au>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "dmitry.kasatkin@...il.com" <dmitry.kasatkin@...il.com>,
        "paul@...l-moore.com" <paul@...l-moore.com>,
        "jmorris@...ei.org" <jmorris@...ei.org>,
        "serge@...lyn.com" <serge@...lyn.com>,
        "pvorel@...e.cz" <pvorel@...e.cz>,
        Kanth Ghatraju <kanth.ghatraju@...cle.com>,
        Konrad Wilk <konrad.wilk@...cle.com>,
        "erpalmer@...ux.vnet.ibm.com" <erpalmer@...ux.vnet.ibm.com>,
        "coxu@...hat.com" <coxu@...hat.com>,
        "keyrings@...r.kernel.org" <keyrings@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH v5 5/6] KEYS: CA link restriction



> On Mar 11, 2023, at 3:10 PM, Jarkko Sakkinen <jarkko@...nel.org> wrote:
> 
> On Thu, Mar 02, 2023 at 11:46:51AM -0500, Eric Snowberg wrote:
>> Add a new link restriction.  Restrict the addition of keys in a keyring
>> based on the key to be added being a CA.
>> 
>> Signed-off-by: Eric Snowberg <eric.snowberg@...cle.com>
>> Reviewed-by: Mimi Zohar <zohar@...ux.ibm.com>
>> ---
>> crypto/asymmetric_keys/restrict.c | 38 +++++++++++++++++++++++++++++++
>> include/crypto/public_key.h       | 15 ++++++++++++
>> 2 files changed, 53 insertions(+)
>> 
>> diff --git a/crypto/asymmetric_keys/restrict.c b/crypto/asymmetric_keys/restrict.c
>> index 6b1ac5f5896a..48457c6f33f9 100644
>> --- a/crypto/asymmetric_keys/restrict.c
>> +++ b/crypto/asymmetric_keys/restrict.c
>> @@ -108,6 +108,44 @@ int restrict_link_by_signature(struct key *dest_keyring,
>> 	return ret;
>> }
>> 
>> +/**
>> + * restrict_link_by_ca - Restrict additions to a ring of CA keys
>> + * @dest_keyring: Keyring being linked to.
>> + * @type: The type of key being added.
>> + * @payload: The payload of the new key.
>> + * @trust_keyring: Unused.
>> + *
>> + * Check if the new certificate is a CA. If it is a CA, then mark the new
>> + * certificate as being ok to link.
>> + *
>> + * Returns 0 if the new certificate was accepted, -ENOKEY if the
>> + * certificate is not a CA. -ENOPKG if the signature uses unsupported
>> + * crypto, or some other error if there is a matching certificate but
>> + * the signature check cannot be performed.
>> + */
>> +int restrict_link_by_ca(struct key *dest_keyring,
>> +			const struct key_type *type,
>> +			const union key_payload *payload,
>> +			struct key *trust_keyring)
>> +{
>> +	const struct public_key *pkey;
>> +
>> +	if (type != &key_type_asymmetric)
>> +		return -EOPNOTSUPP;
>> +
>> +	pkey = payload->data[asym_crypto];
>> +	if (!pkey)
>> +		return -ENOPKG;
>> +	if (!test_bit(KEY_EFLAG_CA, &pkey->key_eflags))
>> +		return -ENOKEY;
>> +	if (!test_bit(KEY_EFLAG_KEYCERTSIGN, &pkey->key_eflags))
>> +		return -ENOKEY;
>> +	if (test_bit(KEY_EFLAG_DIGITALSIG, &pkey->key_eflags))
>> +		return -ENOKEY;
> 
> nit: would be more readable, if conditions were separated by
> empty lines.

Ok, I will make this change in the next round.  Thanks.