[1/2] public key: IMA signer logging: Add support for querying public key from a given key

Commit Message

Lakshmi Ramasubramanian May 14, 2019, 5:14 p.m. UTC

Added a new interface method namely query_public_key
to asymmetric_key_subtype interface.

Defined public_key_query_public_key method that returns the public key
of the given key. This method is called when the query_public_key
interface method in asymmetric_key_subtype interface is invoked.

This change will be used by IMA signer logger (described in
PATCH 2/2: public key: IMA signer logging: Add support for querying 
public key from a given key) that logs the signer of the IMA signature 
of a file.

IMA will verify the IMA signature of the file when loading the file.
IMA will query the public key of the key that was used to generate
the IMA signature and measure that into the IMA log.

An attestation service, for instance, would use the public key to attest
that the system files loaded on the machine were signed by valid and
trusted keys. To attest that the system files loaded on the client were
signed by valid and trusted keys, the service would just have to maintain
a list of valid public keys. Using the data in the IMA log the service
can attest the system files loaded on the client machine.

Signed-off-by: Lakshmi <[e-mail]>
---
  Documentation/crypto/asymmetric-keys.txt |  1 +
  crypto/asymmetric_keys/public_key.c      |  7 +++++++
  crypto/asymmetric_keys/signature.c       | 24 ++++++++++++++++++++++++
  include/crypto/public_key.h              |  1 +
  include/keys/asymmetric-subtype.h        |  3 +++
  5 files changed, 36 insertions(+)

Patch

diff --git a/Documentation/crypto/asymmetric-keys.txt 
b/Documentation/crypto/asymmetric-keys.txt
index 8763866b11cf..50f79dd54ab6 100644
--- a/Documentation/crypto/asymmetric-keys.txt
+++ b/Documentation/crypto/asymmetric-keys.txt
@@ -189,6 +189,7 @@  and looks like the following:
  			      const void *in, void *out);
  		int (*verify_signature)(const struct key *key,
  					const struct public_key_signature *sig);
+		const struct public_key* (*query_public_key)(const struct key *key);
  	};

  Asymmetric keys point to this with their payload[asym_subtype] member.
diff --git a/crypto/asymmetric_keys/public_key.c 
b/crypto/asymmetric_keys/public_key.c
index f5d85b47fcc6..991096fae2a8 100644
--- a/crypto/asymmetric_keys/public_key.c
+++ b/crypto/asymmetric_keys/public_key.c
@@ -311,6 +311,12 @@  static int public_key_verify_signature_2(const 
struct key *key,
  	return public_key_verify_signature(pk, sig);
  }

+static const struct public_key *public_key_query_public_key(
+					const struct key *key)
+{
+	return key->payload.data[asym_crypto];
+}
+
  /*
   * Public key algorithm asymmetric key subtype
   */
@@ -323,5 +329,6 @@  struct asymmetric_key_subtype public_key_subtype = {
  	.query			= software_key_query,
  	.eds_op			= software_key_eds_op,
  	.verify_signature	= public_key_verify_signature_2,
+	.query_public_key	= public_key_query_public_key,
  };
  EXPORT_SYMBOL_GPL(public_key_subtype);
diff --git a/crypto/asymmetric_keys/signature.c 
b/crypto/asymmetric_keys/signature.c
index ad95a58c6642..7db14f8f3ddd 100644
--- a/crypto/asymmetric_keys/signature.c
+++ b/crypto/asymmetric_keys/signature.c
@@ -161,3 +161,27 @@  int verify_signature(const struct key *key,
  	return ret;
  }
  EXPORT_SYMBOL_GPL(verify_signature);
+
+const struct public_key *query_public_key(const struct key *key)
+{
+	const struct public_key *pk;
+	const struct asymmetric_key_subtype *subtype;
+
+	pr_devel("==>%s()\n", __func__);
+
+	if (key->type != &key_type_asymmetric)
+		return NULL;
+	subtype = asymmetric_key_subtype(key);
+	if (!subtype ||
+	    !key->payload.data[0])
+		return NULL;
+	if (!subtype->query_public_key)
+		return NULL;
+
+	pk = subtype->query_public_key(key);
+
+	pr_devel("<==%s()\n", __func__);
+
+	return pk;
+}
+EXPORT_SYMBOL_GPL(query_public_key);
diff --git a/include/crypto/public_key.h b/include/crypto/public_key.h
index be626eac9113..e93014e516af 100644
--- a/include/crypto/public_key.h
+++ b/include/crypto/public_key.h
@@ -77,6 +77,7 @@  extern int decrypt_blob(struct kernel_pkey_params *, 
const void *, void *);
  extern int create_signature(struct kernel_pkey_params *, const void *, 
void *);
  extern int verify_signature(const struct key *,
  			    const struct public_key_signature *);
+extern const struct public_key *query_public_key(const struct key *key);

  int public_key_verify_signature(const struct public_key *pkey,
  				const struct public_key_signature *sig);
diff --git a/include/keys/asymmetric-subtype.h 
b/include/keys/asymmetric-subtype.h
index 9ce2f0fae57e..8e1cbeed4d54 100644
--- a/include/keys/asymmetric-subtype.h
+++ b/include/keys/asymmetric-subtype.h
@@ -46,6 +46,9 @@  struct asymmetric_key_subtype {
  	/* Verify the signature on a key of this subtype (optional) */
  	int (*verify_signature)(const struct key *key,
  				const struct public_key_signature *sig);
+
+	/* Query public key of the given key */
+	const struct public_key *(*query_public_key)(const struct key *key);
  };

  /**