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SubjectRe: [PATCH 3/4] KEYS: CA link restriction
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On 3/1/22 12:36, 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@oracle.com>
> ---
> 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 6b1ac5f5896a..49bb2ea7f609 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.

CA = root CA here, right?


> + *
> + * 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)
This function needs to correspond to the key_restrict_link_func_t and
therefore has 4 parameter. Call the unused 'trust_keyring' 'unused' instead?
> +{
> + 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);
> +}
> +

Comparing this to 'restrict_link_by_signature'... looks good.


> static bool match_either_id(const struct asymmetric_key_id **pair,
> const struct asymmetric_key_id *single)
> {
> diff --git a/include/crypto/public_key.h b/include/crypto/public_key.h
> index 0521241764b7..5eadb182a400 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 *);
>

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