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    Subject[PATCH v8 06/17] KEYS: CA link restriction
    Date
    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@oracle.com>
    ---
    v1: Initial version
    v2: Removed secondary keyring references
    v3: Removed restrict_link_by_system_trusted_or_ca
    Simplify restrict_link_by_ca - only see if the key is a CA
    Did not add __init in front of restrict_link_by_ca in case
    restriction could be resued in the future
    v6: Unmodified from v3
    v7: Check for CA restruction in public key
    v8: Fix issue found by build bot when asym keys not defined in the config
    ---
    crypto/asymmetric_keys/restrict.c | 43 +++++++++++++++++++++++++++++++
    include/crypto/public_key.h | 15 +++++++++++
    2 files changed, 58 insertions(+)

    diff --git a/crypto/asymmetric_keys/restrict.c b/crypto/asymmetric_keys/restrict.c
    index 84cefe3b3585..a891c598a2aa 100644
    --- a/crypto/asymmetric_keys/restrict.c
    +++ b/crypto/asymmetric_keys/restrict.c
    @@ -108,6 +108,49 @@ 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_signature *sig;
    + const struct public_key *pkey;
    +
    + if (type != &key_type_asymmetric)
    + return -EOPNOTSUPP;
    +
    + sig = payload->data[asym_auth];
    + if (!sig)
    + return -ENOPKG;
    +
    + if (!sig->auth_ids[0] && !sig->auth_ids[1])
    + return -ENOKEY;
    +
    + pkey = payload->data[asym_crypto];
    + if (!pkey)
    + return -ENOPKG;
    +
    + if (!pkey->key_is_ca)
    + return -ENOKEY;
    +
    + return public_key_verify_signature(pkey, sig);
    +}
    +
    static bool match_either_id(const struct asymmetric_key_ids *pair,
    const struct asymmetric_key_id *single)
    {
    diff --git a/include/crypto/public_key.h b/include/crypto/public_key.h
    index 72dcbc06ef9c..06e34d3340c4 100644
    --- a/include/crypto/public_key.h
    +++ b/include/crypto/public_key.h
    @@ -72,6 +72,21 @@ extern int restrict_link_by_key_or_keyring_chain(struct key *trust_keyring,
    const union key_payload *payload,
    struct key *trusted);

    +#if IS_REACHABLE(CONFIG_ASYMMETRIC_KEY_TYPE)
    +extern int restrict_link_by_ca(struct key *dest_keyring,
    + const struct key_type *type,
    + const union key_payload *payload,
    + struct key *trust_keyring);
    +#else
    +static inline int restrict_link_by_ca(struct key *dest_keyring,
    + const struct key_type *type,
    + const union key_payload *payload,
    + struct key *trust_keyring)
    +{
    + return 0;
    +}
    +#endif
    +
    extern int query_asymmetric_key(const struct kernel_pkey_params *,
    struct kernel_pkey_query *);

    --
    2.18.4
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