s390/crypto: enable clear key values for paes ciphers

With this patch the paes ciphers do accept AES clear key values of
size 16, 24 or 32 byte. The key value is internal rearranged to form a
paes clear key token so that the pkey kernel module recognizes and
handles this key material as source for protected keys.

Using clear key material as a source for protected keys is a security
risc as the raw key material is kept in memory. However, so the AES
selftests provided with the testmanager can be run during registration
of the paes ciphers.

Signed-off-by: Harald Freudenberger <[e-mail]>
Signed-off-by: Vasily Gorbik <[e-mail]>

arch/s390/crypto/paes_s390.c

···
  * is called. As paes can handle different kinds of key blobs
  * and padding is also possible, the limits need to be generous.
  */
-#define PAES_MIN_KEYSIZE 64
+#define PAES_MIN_KEYSIZE 16
 #define PAES_MAX_KEYSIZE 256
 
 static u8 *ctrblk;
···
 	unsigned int keylen;
 };
 
-static inline int _copy_key_to_kb(struct key_blob *kb,
-				  const u8 *key,
-				  unsigned int keylen)
+static inline int _key_to_kb(struct key_blob *kb,
+			     const u8 *key,
+			     unsigned int keylen)
 {
-	if (keylen <= sizeof(kb->keybuf))
+	struct clearkey_header {
+		u8  type;
+		u8  res0[3];
+		u8  version;
+		u8  res1[3];
+		u32 keytype;
+		u32 len;
+	} __packed * h;
+
+	switch (keylen) {
+	case 16:
+	case 24:
+	case 32:
+		/* clear key value, prepare pkey clear key token in keybuf */
+		memset(kb->keybuf, 0, sizeof(kb->keybuf));
+		h = (struct clearkey_header *) kb->keybuf;
+		h->version = 0x02; /* TOKVER_CLEAR_KEY */
+		h->keytype = (keylen - 8) >> 3;
+		h->len = keylen;
+		memcpy(kb->keybuf + sizeof(*h), key, keylen);
+		kb->keylen = sizeof(*h) + keylen;
 		kb->key = kb->keybuf;
-	else {
-		kb->key = kmalloc(keylen, GFP_KERNEL);
-		if (!kb->key)
-			return -ENOMEM;
+		break;
+	default:
+		/* other key material, let pkey handle this */
+		if (keylen <= sizeof(kb->keybuf))
+			kb->key = kb->keybuf;
+		else {
+			kb->key = kmalloc(keylen, GFP_KERNEL);
+			if (!kb->key)
+				return -ENOMEM;
+		}
+		memcpy(kb->key, key, keylen);
+		kb->keylen = keylen;
+		break;
 	}
-	memcpy(kb->key, key, keylen);
-	kb->keylen = keylen;
 
 	return 0;
 }
···
 	struct s390_paes_ctx *ctx = crypto_skcipher_ctx(tfm);
 
 	_free_kb_keybuf(&ctx->kb);
-	rc = _copy_key_to_kb(&ctx->kb, in_key, key_len);
+	rc = _key_to_kb(&ctx->kb, in_key, key_len);
 	if (rc)
 		return rc;
 
···
 	struct s390_paes_ctx *ctx = crypto_skcipher_ctx(tfm);
 
 	_free_kb_keybuf(&ctx->kb);
-	rc = _copy_key_to_kb(&ctx->kb, in_key, key_len);
+	rc = _key_to_kb(&ctx->kb, in_key, key_len);
 	if (rc)
 		return rc;
 
···
 
 	_free_kb_keybuf(&ctx->kb[0]);
 	_free_kb_keybuf(&ctx->kb[1]);
-	rc = _copy_key_to_kb(&ctx->kb[0], in_key, key_len);
+	rc = _key_to_kb(&ctx->kb[0], in_key, key_len);
 	if (rc)
 		return rc;
-	rc = _copy_key_to_kb(&ctx->kb[1], in_key + key_len, key_len);
+	rc = _key_to_kb(&ctx->kb[1], in_key + key_len, key_len);
 	if (rc)
 		return rc;
 
···
 	struct s390_paes_ctx *ctx = crypto_skcipher_ctx(tfm);
 
 	_free_kb_keybuf(&ctx->kb);
-	rc = _copy_key_to_kb(&ctx->kb, in_key, key_len);
+	rc = _key_to_kb(&ctx->kb, in_key, key_len);
 	if (rc)
 		return rc;
 
···
 
 static void paes_s390_fini(void)
 {
-	if (ctrblk)
-		free_page((unsigned long) ctrblk);
 	__crypto_unregister_skcipher(&ctr_paes_alg);
 	__crypto_unregister_skcipher(&xts_paes_alg);
 	__crypto_unregister_skcipher(&cbc_paes_alg);
 	__crypto_unregister_skcipher(&ecb_paes_alg);
+	if (ctrblk)
+		free_page((unsigned long) ctrblk);
 }
 
 static int __init paes_s390_init(void)
···
 	if (cpacf_test_func(&kmctr_functions, CPACF_KMCTR_PAES_128) ||
 	    cpacf_test_func(&kmctr_functions, CPACF_KMCTR_PAES_192) ||
 	    cpacf_test_func(&kmctr_functions, CPACF_KMCTR_PAES_256)) {
-		ret = crypto_register_skcipher(&ctr_paes_alg);
-		if (ret)
-			goto out_err;
 		ctrblk = (u8 *) __get_free_page(GFP_KERNEL);
 		if (!ctrblk) {
 			ret = -ENOMEM;
 			goto out_err;
 		}
+		ret = crypto_register_skcipher(&ctr_paes_alg);
+		if (ret)
+			goto out_err;
 	}
 
 	return 0;