s390/pkey: Introduce new API for random protected key generation

This patch introduces a new ioctl API and in-kernel API to
generate a random protected key. The protected key is generated
in a way that the effective clear key is never exposed in clear.
Both APIs are described in detail in the header files
arch/s390/include/asm/pkey.h and arch/s390/include/uapi/asm/pkey.h.
Signed-off-by: Ingo Franzki <ifranzki@linux.ibm.com>
Reviewed-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Hendrik Brueckner <brueckner@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/pkey.h

@@ -109,4 +109,12 @@ int pkey_verifykey(const struct pkey_seckey *seckey,
 		   u16 *pcardnr, u16 *pdomain,
 		   u16 *pkeysize, u32 *pattributes);
 
+/*
+ * In-kernel API: Generate (AES) random protected key.
+ * @param keytype one of the PKEY_KEYTYPE values
+ * @param protkey pointer to buffer receiving the protected key
+ * @return 0 on success, negative errno value on failure
+ */
+int pkey_genprotkey(__u32 keytype, struct pkey_protkey *protkey);
+
 #endif /* _KAPI_PKEY_H */

arch/s390/include/uapi/asm/pkey.h

@@ -129,4 +129,14 @@ struct pkey_verifykey {
 #define PKEY_VERIFY_ATTR_AES	   0x00000001  /* key is an AES key */
 #define PKEY_VERIFY_ATTR_OLD_MKVP  0x00000100  /* key has old MKVP value */
 
+/*
+ * Generate (AES) random protected key.
+ */
+struct pkey_genprotk {
+	__u32 keytype;			       /* in: key type to generate */
+	struct pkey_protkey protkey;	       /* out: the protected key   */
+};
+
+#define PKEY_GENPROTK _IOWR(PKEY_IOCTL_MAGIC, 0x08, struct pkey_genprotk)
+
 #endif /* _UAPI_PKEY_H */

drivers/s390/crypto/pkey_api.c

@@ -16,6 +16,7 @@
 #include <linux/slab.h>
 #include <linux/kallsyms.h>
 #include <linux/debugfs.h>
+#include <linux/random.h>
 #include <asm/zcrypt.h>
 #include <asm/cpacf.h>
 #include <asm/pkey.h>
@@ -1051,6 +1052,46 @@ int pkey_verifykey(const struct pkey_seckey *seckey,
 }
 EXPORT_SYMBOL(pkey_verifykey);
 
+/*
+ * Generate a random protected key
+ */
+int pkey_genprotkey(__u32 keytype, struct pkey_protkey *protkey)
+{
+	struct pkey_clrkey clrkey;
+	int keysize;
+	int rc;
+
+	switch (keytype) {
+	case PKEY_KEYTYPE_AES_128:
+		keysize = 16;
+		break;
+	case PKEY_KEYTYPE_AES_192:
+		keysize = 24;
+		break;
+	case PKEY_KEYTYPE_AES_256:
+		keysize = 32;
+		break;
+	default:
+		DEBUG_ERR("%s unknown/unsupported keytype %d\n", __func__,
+			  keytype);
+		return -EINVAL;
+	}
+
+	/* generate a dummy random clear key */
+	get_random_bytes(clrkey.clrkey, keysize);
+
+	/* convert it to a dummy protected key */
+	rc = pkey_clr2protkey(keytype, &clrkey, protkey);
+	if (rc)
+		return rc;
+
+	/* replace the key part of the protected key with random bytes */
+	get_random_bytes(protkey->protkey, keysize);
+
+	return 0;
+}
+EXPORT_SYMBOL(pkey_genprotkey);
+
 /*
  * File io functions
  */
@@ -1167,6 +1208,20 @@ static long pkey_unlocked_ioctl(struct file *filp, unsigned int cmd,
 			return -EFAULT;
 		break;
 	}
+	case PKEY_GENPROTK: {
+		struct pkey_genprotk __user *ugp = (void __user *) arg;
+		struct pkey_genprotk kgp;
+
+		if (copy_from_user(&kgp, ugp, sizeof(kgp)))
+			return -EFAULT;
+		rc = pkey_genprotkey(kgp.keytype, &kgp.protkey);
+		DEBUG_DBG("%s pkey_genprotkey()=%d\n", __func__, rc);
+		if (rc)
+			break;
+		if (copy_to_user(ugp, &kgp, sizeof(kgp)))
+			return -EFAULT;
+		break;
+	}
 	default:
 		/* unknown/unsupported ioctl cmd */
 		return -ENOTTY;