[PATCH v1a 0/2] KEYS: validate key trust with owner and builtin keys only

[PATCH v1a 0/2] KEYS: validate key trust with owner and builtin keys only

[Dmitry Kasatkin]

This is a repost of the patchset cleanly on the top of linux-integrity
next-trusted-keys branch.

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
set further restricts the certificates to those signed by a particular key
or builtin keys on the system keyring.

This patch defines a new kernel parameter 'keys_ownerid={id:xxx | builtin}'
to use specific key or any builtin key.

Thanks,
Dmitry

Dmitry Kasatkin (2):
  KEYS: validate certificate trust only with selected owner key
  KEYS: validate certificate trust only with builtin keys

 Documentation/kernel-parameters.txt      |  5 +++++
 crypto/asymmetric_keys/x509_public_key.c | 32 ++++++++++++++++++++++++++++++--
 include/linux/key.h                      |  1 +
 kernel/system_keyring.c                  |  1 +
 4 files changed, 37 insertions(+), 2 deletions(-)

-- 
1.9.1

[PATCH v1a 1/2] KEYS: validate certificate trust only with selected owner key

[Dmitry Kasatkin]

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;
+	}
+
 	key = x509_request_asymmetric_key(trust_keyring,
 					  cert->issuer, strlen(cert->issuer),
 					  cert->authority,
-- 
1.9.1

[PATCH v1a 2/2] KEYS: validate certificate trust only with builtin keys

[Dmitry Kasatkin]

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 only by
builtin keys on the system keyring.

This patch defines a new option 'builtin' for the kernel parameter
'keys_ownerid' to allow trust validation using builtin keys.

Idea belongs to Mimi Zohar.

Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
---
 Documentation/kernel-parameters.txt      | 2 +-
 crypto/asymmetric_keys/x509_public_key.c | 9 +++++++--
 include/linux/key.h                      | 1 +
 kernel/system_keyring.c                  | 1 +
 4 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 7a810d3..336dabe 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1437,7 +1437,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 	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>
+			format: { id:<keyid> | builtin }
 
 	kgdbdbgp=	[KGDB,HW] kgdb over EHCI usb debug port.
 			Format: <Controller#>[,poll interval]
diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
index d46b790..c3805a8 100644
--- a/crypto/asymmetric_keys/x509_public_key.c
+++ b/crypto/asymmetric_keys/x509_public_key.c
@@ -24,6 +24,7 @@
 #include "public_key.h"
 #include "x509_parser.h"
 
+static bool builtin_keys;
 static char *owner_keyid;
 static int __init default_owner_keyid_set(char *str)
 {
@@ -32,6 +33,8 @@ static int __init default_owner_keyid_set(char *str)
 
 	if (strncmp(str, "id:", 3) == 0)
 		owner_keyid = str;	/* owner local key 'id:xxxxxx' */
+	else if (strcmp(str, "builtin") == 0)
+		builtin_keys = true;
 
 	return 1;
 }
@@ -197,8 +200,10 @@ static int x509_validate_trust(struct x509_certificate *cert,
 					  cert->authority,
 					  strlen(cert->authority));
 	if (!IS_ERR(key))  {
-		pk = key->payload.data;
-		ret = x509_check_signature(pk, cert);
+		if (!builtin_keys || test_bit(KEY_FLAG_BUILTIN, &key->flags)) {
+			pk = key->payload.data;
+			ret = x509_check_signature(pk, cert);
+		}
 		key_put(key);
 	}
 	return ret;
diff --git a/include/linux/key.h b/include/linux/key.h
index cd0abb8..67c8e7e 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -170,6 +170,7 @@ struct key {
 #define KEY_FLAG_INVALIDATED	7	/* set if key has been invalidated */
 #define KEY_FLAG_TRUSTED	8	/* set if key is trusted */
 #define KEY_FLAG_TRUSTED_ONLY	9	/* set if keyring only accepts links to trusted keys */
+#define KEY_FLAG_BUILTIN	10	/* set if key is builtin */
 
 	/* the key type and key description string
 	 * - the desc is used to match a key against search criteria
diff --git a/kernel/system_keyring.c b/kernel/system_keyring.c
index 52ebc70..875f64e 100644
--- a/kernel/system_keyring.c
+++ b/kernel/system_keyring.c
@@ -89,6 +89,7 @@ static __init int load_system_certificate_list(void)
 			pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
 			       PTR_ERR(key));
 		} else {
+			set_bit(KEY_FLAG_BUILTIN, &key_ref_to_ptr(key)->flags);
 			pr_notice("Loaded X.509 cert '%s'\n",
 				  key_ref_to_ptr(key)->description);
 			key_ref_put(key);
-- 
1.9.1

Re: [PATCH v1a 1/2] KEYS: validate certificate trust only with selected owner key

[Mimi Zohar]

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,

Re: [PATCH v1a 2/2] KEYS: validate certificate trust only with builtin keys

[Mimi Zohar]

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 only by
> builtin keys on the system keyring.
> 
> This patch defines a new option 'builtin' for the kernel parameter
> 'keys_ownerid' to allow trust validation using builtin keys.

Thanks, this patch works without a separate 'owned' trusted keyring, but
we need to wait until the UEFI key patches are upstreamed.

thanks,

Mimi 

> Idea belongs to Mimi Zohar.
> 
> Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
> ---
>  Documentation/kernel-parameters.txt      | 2 +-
>  crypto/asymmetric_keys/x509_public_key.c | 9 +++++++--
>  include/linux/key.h                      | 1 +
>  kernel/system_keyring.c                  | 1 +
>  4 files changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index 7a810d3..336dabe 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -1437,7 +1437,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
>  	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>
> +			format: { id:<keyid> | builtin }
> 
>  	kgdbdbgp=	[KGDB,HW] kgdb over EHCI usb debug port.
>  			Format: <Controller#>[,poll interval]
> diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
> index d46b790..c3805a8 100644
> --- a/crypto/asymmetric_keys/x509_public_key.c
> +++ b/crypto/asymmetric_keys/x509_public_key.c
> @@ -24,6 +24,7 @@
>  #include "public_key.h"
>  #include "x509_parser.h"
> 
> +static bool builtin_keys;
>  static char *owner_keyid;
>  static int __init default_owner_keyid_set(char *str)
>  {
> @@ -32,6 +33,8 @@ static int __init default_owner_keyid_set(char *str)
> 
>  	if (strncmp(str, "id:", 3) == 0)
>  		owner_keyid = str;	/* owner local key 'id:xxxxxx' */
> +	else if (strcmp(str, "builtin") == 0)
> +		builtin_keys = true;
> 
>  	return 1;
>  }
> @@ -197,8 +200,10 @@ static int x509_validate_trust(struct x509_certificate *cert,
>  					  cert->authority,
>  					  strlen(cert->authority));
>  	if (!IS_ERR(key))  {
> -		pk = key->payload.data;
> -		ret = x509_check_signature(pk, cert);
> +		if (!builtin_keys || test_bit(KEY_FLAG_BUILTIN, &key->flags)) {
> +			pk = key->payload.data;
> +			ret = x509_check_signature(pk, cert);
> +		}
>  		key_put(key);
>  	}
>  	return ret;
> diff --git a/include/linux/key.h b/include/linux/key.h
> index cd0abb8..67c8e7e 100644
> --- a/include/linux/key.h
> +++ b/include/linux/key.h
> @@ -170,6 +170,7 @@ struct key {
>  #define KEY_FLAG_INVALIDATED	7	/* set if key has been invalidated */
>  #define KEY_FLAG_TRUSTED	8	/* set if key is trusted */
>  #define KEY_FLAG_TRUSTED_ONLY	9	/* set if keyring only accepts links to trusted keys */
> +#define KEY_FLAG_BUILTIN	10	/* set if key is builtin */
> 
>  	/* the key type and key description string
>  	 * - the desc is used to match a key against search criteria
> diff --git a/kernel/system_keyring.c b/kernel/system_keyring.c
> index 52ebc70..875f64e 100644
> --- a/kernel/system_keyring.c
> +++ b/kernel/system_keyring.c
> @@ -89,6 +89,7 @@ static __init int load_system_certificate_list(void)
>  			pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
>  			       PTR_ERR(key));
>  		} else {
> +			set_bit(KEY_FLAG_BUILTIN, &key_ref_to_ptr(key)->flags);
>  			pr_notice("Loaded X.509 cert '%s'\n",
>  				  key_ref_to_ptr(key)->description);
>  			key_ref_put(key);

Re: [PATCH v1a 1/2] KEYS: validate certificate trust only with selected owner key

[Dmitry Kasatkin]

On 16/06/14 14:43, Mimi Zohar wrote:
> 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,

Right.

I addressed this in the following patchset.

Thanks.


>
> Mimi
>
>>  	key = x509_request_asymmetric_key(trust_keyring,
>>  					  cert->issuer, strlen(cert->issuer),
>>  					  cert->authority,
>
>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-security-module" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>