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SubjectRe: [PATCH v1a 1/2] KEYS: validate certificate trust only with selected owner key
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On Thu, 2014-06-12 at 23:17 +0300, Dmitry Kasatkin wrote:
> Instead of allowing public keys, with certificates signed by any
> key on the system trusted keyring, to be added to a trusted keyring,
> this patch further restricts the certificates to those signed by a
> particular key on the system keyring.
>
> This patch defines a new kernel parameter 'keys_ownerid' to specify
> owner's key id which must be used for trust validation of certificates.
>
> Idea belongs to Mimi Zohar.
>
> Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
> ---
> Documentation/kernel-parameters.txt | 5 +++++
> crypto/asymmetric_keys/x509_public_key.c | 23 +++++++++++++++++++++++
> 2 files changed, 28 insertions(+)
>
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index 7116fda..7a810d3 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -1434,6 +1434,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
> use the HighMem zone if it exists, and the Normal
> zone if it does not.
>
> + keys_ownerid=[KEYS] This parameter identifies a specific key(s) on
> + the system trusted keyring to be used for certificate
> + trust validation.
> + format: id:<keyid>
> +
> kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
> Format: <Controller#>[,poll interval]
> The controller # is the number of the ehci usb debug
> diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
> index 7a9b386..d46b790 100644
> --- a/crypto/asymmetric_keys/x509_public_key.c
> +++ b/crypto/asymmetric_keys/x509_public_key.c
> @@ -24,6 +24,19 @@
> #include "public_key.h"
> #include "x509_parser.h"
>
> +static char *owner_keyid;
> +static int __init default_owner_keyid_set(char *str)
> +{
> + if (!str) /* default system keyring */
> + return 1;
> +
> + if (strncmp(str, "id:", 3) == 0)
> + owner_keyid = str; /* owner local key 'id:xxxxxx' */
> +
> + return 1;
> +}
> +__setup("keys_ownerid=", default_owner_keyid_set);
> +
> /*
> * Find a key in the given keyring by issuer and authority.
> */
> @@ -169,6 +182,16 @@ static int x509_validate_trust(struct x509_certificate *cert,
> if (!trust_keyring)
> return -EOPNOTSUPP;
>
> + if (owner_keyid) {
> + /* validate trust only with the owner_keyid if specified */
> + /* partial match of keyid according to the asymmetric_type.c */
> + int idlen = strlen(owner_keyid) - 3; /* - id: */
> + int authlen = strlen(cert->authority);
> + char *auth = cert->authority + authlen - idlen;
> + if (idlen > authlen || strcasecmp(owner_keyid + 3, auth))
> + return -EPERM;
> + }
> +

We shouldn't hard code the test here, but use the key type's match
function. For example, the "KEYS: define an owner trusted keyring" (v4)
patch defined a key_match() function.

thanks,

Mimi

> key = x509_request_asymmetric_key(trust_keyring,
> cert->issuer, strlen(cert->issuer),
> cert->authority,






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