s390/pkey: Add support for key blob with clear key value

This patch adds support for a new key blob format to the
pkey kernel module. The new key blob comprises a clear
key value together with key type information.

The implementation tries to derive an protected key
from the blob with the clear key value inside with
1) the PCKMO instruction. This may fail as the LPAR
   profile may disable this way.
2) Generate an CCA AES secure data key with exact the
   clear key value. This requires to have a working
   crypto card in CCA Coprocessor mode. Then derive
   an protected key from the CCA AES secure key again
   with the help of a working crypto card in CCA mode.
If both way fail, the transformation of the clear key
blob into a protected key will fail. For the PAES cipher
this would result in a failure at setkey() invocation.

A clear key value exposed in main memory is a security
risk. The intention of this new 'clear key blob' support
for pkey is to provide self-tests for the PAES cipher key
implementation. These known answer tests obviously need
to be run with well known key values. So with the clear
key blob format there is a way to provide knwon answer
tests together with an pkey clear key blob for the
in-kernel self tests done at cipher registration.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

1 files changed, 54 insertions, 6 deletions

diff --git a/drivers/s390/crypto/pkey_api.c b/drivers/s390/crypto/pkey_api.c
index d78d77686d7b..3ecb6a255a0c 100644
--- a/drivers/s390/crypto/pkey_api.c
+++ b/drivers/s390/crypto/pkey_api.c
@@ -71,6 +71,17 @@ struct protaeskeytoken {
 	u8  protkey[MAXPROTKEYSIZE]; /* the protected key blob */
 } __packed;
 
+/* inside view of a clear key token (type 0x00 version 0x02) */
+struct clearaeskeytoken {
+	u8  type;	 /* 0x00 for PAES specific key tokens */
+	u8  res0[3];
+	u8  version;	 /* 0x02 for clear AES key token */
+	u8  res1[3];
+	u32 keytype;	 /* key type, one of the PKEY_KEYTYPE values */
+	u32 len;	 /* bytes actually stored in clearkey[] */
+	u8  clearkey[0]; /* clear key value */
+} __packed;
+
 /*
  * Create a protected key from a clear key value.
  */
@@ -305,26 +316,63 @@ static int pkey_verifyprotkey(const struct pkey_protkey *protkey)
 static int pkey_nonccatok2pkey(const u8 *key, u32 keylen,
 			       struct pkey_protkey *protkey)
 {
+	int rc = -EINVAL;
 	struct keytoken_header *hdr = (struct keytoken_header *)key;
-	struct protaeskeytoken *t;
 
 	switch (hdr->version) {
-	case TOKVER_PROTECTED_KEY:
-		if (keylen != sizeof(struct protaeskeytoken))
-			return -EINVAL;
+	case TOKVER_PROTECTED_KEY: {
+		struct protaeskeytoken *t;
 
+		if (keylen != sizeof(struct protaeskeytoken))
+			goto out;
 		t = (struct protaeskeytoken *)key;
 		protkey->len = t->len;
 		protkey->type = t->keytype;
 		memcpy(protkey->protkey, t->protkey,
 		       sizeof(protkey->protkey));
+		rc = pkey_verifyprotkey(protkey);
+		break;
+	}
+	case TOKVER_CLEAR_KEY: {
+		struct clearaeskeytoken *t;
+		struct pkey_clrkey ckey;
+		struct pkey_seckey skey;
 
-		return pkey_verifyprotkey(protkey);
+		if (keylen < sizeof(struct clearaeskeytoken))
+			goto out;
+		t = (struct clearaeskeytoken *)key;
+		if (keylen != sizeof(*t) + t->len)
+			goto out;
+		if ((t->keytype == PKEY_KEYTYPE_AES_128 && t->len == 16)
+		    || (t->keytype == PKEY_KEYTYPE_AES_192 && t->len == 24)
+		    || (t->keytype == PKEY_KEYTYPE_AES_256 && t->len == 32))
+			memcpy(ckey.clrkey, t->clearkey, t->len);
+		else
+			goto out;
+		/* try direct way with the PCKMO instruction */
+		rc = pkey_clr2protkey(t->keytype, &ckey, protkey);
+		if (rc == 0)
+			break;
+		/* PCKMO failed, so try the CCA secure key way */
+		rc = cca_clr2seckey(0xFFFF, 0xFFFF, t->keytype,
+				    ckey.clrkey, skey.seckey);
+		if (rc == 0)
+			rc = pkey_skey2pkey(skey.seckey, protkey);
+		/* now we should really have an protected key */
+		if (rc == 0)
+			break;
+		DEBUG_ERR("%s unable to build protected key from clear",
+			  __func__);
+		break;
+	}
 	default:
 		DEBUG_ERR("%s unknown/unsupported non-CCA token version %d\n",
 			  __func__, hdr->version);
-		return -EINVAL;
+		rc = -EINVAL;
 	}
+
+out:
+	return rc;
 }
 
 /*