libceph: add support for CEPH_CRYPTO_AES256KRB5

This is based on AES256-CTS-HMAC384-192 crypto algorithm per RFC 8009
(i.e. Kerberos 5, hence the name) with custom-defined key usage numbers.
The implementation allows a given key to have/be linked to between one
and three usage numbers.

The existing CEPH_CRYPTO_AES remains in place and unchanged.  The
usage_slot parameter that needed to be added to ceph_crypt() and its
wrappers is simply ignored there.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

6 files changed, 257 insertions, 48 deletions

diff --git a/include/linux/ceph/ceph_fs.h b/include/linux/ceph/ceph_fs.h
index 08e5dbe15ca4..69ac3e55a3fe 100644
--- a/include/linux/ceph/ceph_fs.h
+++ b/include/linux/ceph/ceph_fs.h
@@ -89,8 +89,9 @@ struct ceph_dir_layout {
 } __attribute__ ((packed));
 
 /* crypto algorithms */
-#define CEPH_CRYPTO_NONE 0x0
-#define CEPH_CRYPTO_AES  0x1
+#define CEPH_CRYPTO_NONE       0x0
+#define CEPH_CRYPTO_AES        0x1
+#define CEPH_CRYPTO_AES256KRB5 0x2 /* AES256-CTS-HMAC384-192 */
 
 #define CEPH_AES_IV "cephsageyudagreg"
 
diff --git a/net/ceph/Kconfig b/net/ceph/Kconfig
index ea60e3ef0834..7e2528cde4b9 100644
--- a/net/ceph/Kconfig
+++ b/net/ceph/Kconfig
@@ -6,6 +6,7 @@ config CEPH_LIB
 	select CRYPTO_AES
 	select CRYPTO_CBC
 	select CRYPTO_GCM
+	select CRYPTO_KRB5
 	select CRYPTO_LIB_SHA256
 	select CRYPTO
 	select KEYS
diff --git a/net/ceph/auth_x.c b/net/ceph/auth_x.c
index abdd35be263a..decd2867f8f1 100644
--- a/net/ceph/auth_x.c
+++ b/net/ceph/auth_x.c
@@ -17,6 +17,22 @@
 #include "auth_x.h"
 #include "auth_x_protocol.h"
 
+static const u32 ticket_key_usages[] = {
+	CEPHX_KEY_USAGE_TICKET_SESSION_KEY,
+	CEPHX_KEY_USAGE_TICKET_BLOB,
+	CEPHX_KEY_USAGE_AUTH_CONNECTION_SECRET
+};
+
+static const u32 authorizer_key_usages[] = {
+	CEPHX_KEY_USAGE_AUTHORIZE,
+	CEPHX_KEY_USAGE_AUTHORIZE_CHALLENGE,
+	CEPHX_KEY_USAGE_AUTHORIZE_REPLY
+};
+
+static const u32 client_key_usages[] = {
+	CEPHX_KEY_USAGE_TICKET_SESSION_KEY
+};
+
 static void ceph_x_validate_tickets(struct ceph_auth_client *ac, int *pneed);
 
 static int ceph_x_is_authenticated(struct ceph_auth_client *ac)
@@ -57,6 +73,7 @@ static int ceph_x_encrypt_offset(const struct ceph_crypto_key *key)
 
 /*
  * AES: ciphertext_len | hdr | data... | padding
+ * AES256KRB5: ciphertext_len | confounder | hdr | data... | hmac
  */
 static int ceph_x_encrypt_buflen(const struct ceph_crypto_key *key,
 				 int data_len)
@@ -65,19 +82,19 @@ static int ceph_x_encrypt_buflen(const struct ceph_crypto_key *key,
 	return sizeof(u32) + ceph_crypt_buflen(key, encrypt_len);
 }
 
-static int ceph_x_encrypt(struct ceph_crypto_key *secret, void *buf,
-			  int buf_len, int plaintext_len)
+static int ceph_x_encrypt(const struct ceph_crypto_key *key, int usage_slot,
+			  void *buf, int buf_len, int plaintext_len)
 {
 	struct ceph_x_encrypt_header *hdr;
 	int ciphertext_len;
 	int ret;
 
-	hdr = buf + sizeof(u32) + ceph_crypt_data_offset(secret);
+	hdr = buf + sizeof(u32) + ceph_crypt_data_offset(key);
 	hdr->struct_v = 1;
 	hdr->magic = cpu_to_le64(CEPHX_ENC_MAGIC);
 
-	ret = ceph_crypt(secret, true, buf + sizeof(u32), buf_len - sizeof(u32),
-			 plaintext_len + sizeof(struct ceph_x_encrypt_header),
+	ret = ceph_crypt(key, usage_slot, true, buf + sizeof(u32),
+			 buf_len - sizeof(u32), plaintext_len + sizeof(*hdr),
 			 &ciphertext_len);
 	if (ret)
 		return ret;
@@ -86,19 +103,19 @@ static int ceph_x_encrypt(struct ceph_crypto_key *secret, void *buf,
 	return sizeof(u32) + ciphertext_len;
 }
 
-static int __ceph_x_decrypt(struct ceph_crypto_key *secret, void *p,
-			    int ciphertext_len)
+static int __ceph_x_decrypt(const struct ceph_crypto_key *key, int usage_slot,
+			    void *p, int ciphertext_len)
 {
 	struct ceph_x_encrypt_header *hdr;
 	int plaintext_len;
 	int ret;
 
-	ret = ceph_crypt(secret, false, p, ciphertext_len, ciphertext_len,
-			 &plaintext_len);
+	ret = ceph_crypt(key, usage_slot, false, p, ciphertext_len,
+			 ciphertext_len, &plaintext_len);
 	if (ret)
 		return ret;
 
-	hdr = p + ceph_crypt_data_offset(secret);
+	hdr = p + ceph_crypt_data_offset(key);
 	if (le64_to_cpu(hdr->magic) != CEPHX_ENC_MAGIC) {
 		pr_err("%s bad magic\n", __func__);
 		return -EINVAL;
@@ -107,7 +124,8 @@ static int __ceph_x_decrypt(struct ceph_crypto_key *secret, void *p,
 	return plaintext_len - sizeof(*hdr);
 }
 
-static int ceph_x_decrypt(struct ceph_crypto_key *secret, void **p, void *end)
+static int ceph_x_decrypt(const struct ceph_crypto_key *key, int usage_slot,
+			  void **p, void *end)
 {
 	int ciphertext_len;
 	int ret;
@@ -115,7 +133,7 @@ static int ceph_x_decrypt(struct ceph_crypto_key *secret, void **p, void *end)
 	ceph_decode_32_safe(p, end, ciphertext_len, e_inval);
 	ceph_decode_need(p, end, ciphertext_len, e_inval);
 
-	ret = __ceph_x_decrypt(secret, *p, ciphertext_len);
+	ret = __ceph_x_decrypt(key, usage_slot, *p, ciphertext_len);
 	if (ret < 0)
 		return ret;
 
@@ -207,7 +225,9 @@ static int process_one_ticket(struct ceph_auth_client *ac,
 
 	/* blob for me */
 	dp = *p + ceph_x_encrypt_offset(secret);
-	ret = ceph_x_decrypt(secret, p, end);
+	ret = ceph_x_decrypt(secret,
+			     0 /* CEPHX_KEY_USAGE_TICKET_SESSION_KEY */,
+			     p, end);
 	if (ret < 0)
 		goto out;
 	dout(" decrypted %d bytes\n", ret);
@@ -221,7 +241,8 @@ static int process_one_ticket(struct ceph_auth_client *ac,
 	if (ret)
 		goto out;
 
-	ret = ceph_crypto_key_prepare(&new_session_key);
+	ret = ceph_crypto_key_prepare(&new_session_key, ticket_key_usages,
+				      ARRAY_SIZE(ticket_key_usages));
 	if (ret)
 		goto out;
 
@@ -238,7 +259,9 @@ static int process_one_ticket(struct ceph_auth_client *ac,
 	if (is_enc) {
 		/* encrypted */
 		tp = *p + ceph_x_encrypt_offset(&th->session_key);
-		ret = ceph_x_decrypt(&th->session_key, p, end);
+		ret = ceph_x_decrypt(&th->session_key,
+				     1 /* CEPHX_KEY_USAGE_TICKET_BLOB */,
+				     p, end);
 		if (ret < 0)
 			goto out;
 		dout(" encrypted ticket, decrypted %d bytes\n", ret);
@@ -341,7 +364,9 @@ static int encrypt_authorizer(struct ceph_x_authorizer *au,
 		msg_b->server_challenge_plus_one = 0;
 	}
 
-	ret = ceph_x_encrypt(&au->session_key, p, end - p, sizeof(*msg_b));
+	ret = ceph_x_encrypt(&au->session_key,
+			     0 /* CEPHX_KEY_USAGE_AUTHORIZE */,
+			     p, end - p, sizeof(*msg_b));
 	if (ret < 0)
 		return ret;
 
@@ -384,7 +409,8 @@ static int ceph_x_build_authorizer(struct ceph_auth_client *ac,
 	if (ret)
 		goto out_au;
 
-	ret = ceph_crypto_key_prepare(&au->session_key);
+	ret = ceph_crypto_key_prepare(&au->session_key, authorizer_key_usages,
+				      ARRAY_SIZE(authorizer_key_usages));
 	if (ret)
 		goto out_au;
 
@@ -542,7 +568,8 @@ static int ceph_x_build_request(struct ceph_auth_client *ac,
 		get_random_bytes(&auth->client_challenge, sizeof(u64));
 		blob->client_challenge = auth->client_challenge;
 		blob->server_challenge = cpu_to_le64(xi->server_challenge);
-		ret = ceph_x_encrypt(&xi->secret, enc_buf, CEPHX_AU_ENC_BUF_LEN,
+		ret = ceph_x_encrypt(&xi->secret, 0 /* dummy */,
+				     enc_buf, CEPHX_AU_ENC_BUF_LEN,
 				     sizeof(*blob));
 		if (ret < 0)
 			return ret;
@@ -656,7 +683,9 @@ static int handle_auth_session_key(struct ceph_auth_client *ac, u64 global_id,
 	dout("%s connection secret blob len %d\n", __func__, len);
 	if (len > 0) {
 		dp = *p + ceph_x_encrypt_offset(&th->session_key);
-		ret = ceph_x_decrypt(&th->session_key, p, *p + len);
+		ret = ceph_x_decrypt(&th->session_key,
+				     2 /* CEPHX_KEY_USAGE_AUTH_CONNECTION_SECRET */,
+				     p, *p + len);
 		if (ret < 0)
 			return ret;
 
@@ -820,7 +849,9 @@ static int decrypt_authorizer_challenge(struct ceph_crypto_key *secret,
 	int ret;
 
 	/* no leading len */
-	ret = __ceph_x_decrypt(secret, challenge, challenge_len);
+	ret = __ceph_x_decrypt(secret,
+			       1 /* CEPHX_KEY_USAGE_AUTHORIZE_CHALLENGE */,
+			       challenge, challenge_len);
 	if (ret < 0)
 		return ret;
 
@@ -873,7 +904,8 @@ static int decrypt_authorizer_reply(struct ceph_crypto_key *secret,
 	int ret;
 
 	dp = *p + ceph_x_encrypt_offset(secret);
-	ret = ceph_x_decrypt(secret, p, end);
+	ret = ceph_x_decrypt(secret, 2 /* CEPHX_KEY_USAGE_AUTHORIZE_REPLY */,
+			     p, end);
 	if (ret < 0)
 		return ret;
 
@@ -1004,8 +1036,9 @@ static int calc_signature(struct ceph_x_authorizer *au, struct ceph_msg *msg,
 		sigblock->middle_crc = msg->footer.middle_crc;
 		sigblock->data_crc =  msg->footer.data_crc;
 
-		ret = ceph_x_encrypt(&au->session_key, enc_buf,
-				     CEPHX_AU_ENC_BUF_LEN, sizeof(*sigblock));
+		ret = ceph_x_encrypt(&au->session_key, 0 /* dummy */,
+				     enc_buf, CEPHX_AU_ENC_BUF_LEN,
+				     sizeof(*sigblock));
 		if (ret < 0)
 			return ret;
 
@@ -1036,9 +1069,9 @@ static int calc_signature(struct ceph_x_authorizer *au, struct ceph_msg *msg,
 		sigblock->seq_lower_word = *(__le32 *)&msg->hdr.seq;
 
 		/* no leading len, no ceph_x_encrypt_header */
-		ret = ceph_crypt(&au->session_key, true, enc_buf,
-				 CEPHX_AU_ENC_BUF_LEN, sizeof(*sigblock),
-				 &ciphertext_len);
+		ret = ceph_crypt(&au->session_key, 0 /* dummy */,
+				 true, enc_buf, CEPHX_AU_ENC_BUF_LEN,
+				 sizeof(*sigblock), &ciphertext_len);
 		if (ret)
 			return ret;
 
@@ -1130,7 +1163,8 @@ int ceph_x_init(struct ceph_auth_client *ac)
 		goto err_xi;
 	}
 
-	ret = ceph_crypto_key_prepare(&xi->secret);
+	ret = ceph_crypto_key_prepare(&xi->secret, client_key_usages,
+				      ARRAY_SIZE(client_key_usages));
 	if (ret) {
 		pr_err("cannot prepare key: %d\n", ret);
 		goto err_secret;
diff --git a/net/ceph/auth_x_protocol.h b/net/ceph/auth_x_protocol.h
index 9c60feeb1bcb..d097b3651c99 100644
--- a/net/ceph/auth_x_protocol.h
+++ b/net/ceph/auth_x_protocol.h
@@ -6,6 +6,44 @@
 #define CEPHX_GET_PRINCIPAL_SESSION_KEY 0x0200
 #define CEPHX_GET_ROTATING_KEY          0x0400
 
+/* Client <-> AuthMonitor */
+/*
+ * The AUTH session's connection secret: encrypted with the AUTH
+ * ticket session key
+ */
+#define CEPHX_KEY_USAGE_AUTH_CONNECTION_SECRET	0x03
+/*
+ * The ticket's blob for the client ("blob for me", contains the
+ * session key): encrypted with the client's secret key in case of
+ * the AUTH ticket and the AUTH ticket session key in case of other
+ * service tickets
+ */
+#define CEPHX_KEY_USAGE_TICKET_SESSION_KEY	0x04
+/*
+ * The ticket's blob for the service (ceph_x_ticket_blob): possibly
+ * encrypted with the old AUTH ticket session key in case of the AUTH
+ * ticket and not encrypted in case of other service tickets
+ */
+#define CEPHX_KEY_USAGE_TICKET_BLOB		0x05
+
+/* Client <-> Service */
+/*
+ * The client's authorization request (ceph_x_authorize_b):
+ * encrypted with the service ticket session key
+ */
+#define CEPHX_KEY_USAGE_AUTHORIZE		0x10
+/*
+ * The service's challenge (ceph_x_authorize_challenge):
+ * encrypted with the service ticket session key
+ */
+#define CEPHX_KEY_USAGE_AUTHORIZE_CHALLENGE	0x11
+/*
+ * The service's final reply (ceph_x_authorize_reply + the service
+ * session's connection secret): encrypted with the service ticket
+ * session key
+ */
+#define CEPHX_KEY_USAGE_AUTHORIZE_REPLY		0x12
+
 /* common bits */
 struct ceph_x_ticket_blob {
 	__u8 struct_v;
diff --git a/net/ceph/crypto.c b/net/ceph/crypto.c
index 3453dc303315..b54085d8d5f0 100644
--- a/net/ceph/crypto.c
+++ b/net/ceph/crypto.c
@@ -7,6 +7,7 @@
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <crypto/aes.h>
+#include <crypto/krb5.h>
 #include <crypto/skcipher.h>
 #include <linux/key-type.h>
 #include <linux/sched/mm.h>
@@ -22,28 +23,68 @@ static int set_aes_tfm(struct ceph_crypto_key *key)
 	int ret;
 
 	noio_flag = memalloc_noio_save();
-	key->tfm = crypto_alloc_sync_skcipher("cbc(aes)", 0, 0);
+	key->aes_tfm = crypto_alloc_sync_skcipher("cbc(aes)", 0, 0);
 	memalloc_noio_restore(noio_flag);
-	if (IS_ERR(key->tfm)) {
-		ret = PTR_ERR(key->tfm);
-		key->tfm = NULL;
+	if (IS_ERR(key->aes_tfm)) {
+		ret = PTR_ERR(key->aes_tfm);
+		key->aes_tfm = NULL;
 		return ret;
 	}
 
-	ret = crypto_sync_skcipher_setkey(key->tfm, key->key, key->len);
+	ret = crypto_sync_skcipher_setkey(key->aes_tfm, key->key, key->len);
 	if (ret)
 		return ret;
 
 	return 0;
 }
 
-int ceph_crypto_key_prepare(struct ceph_crypto_key *key)
+static int set_krb5_tfms(struct ceph_crypto_key *key, const u32 *key_usages,
+			 int key_usage_cnt)
+{
+	struct krb5_buffer TK = { .len = key->len, .data = key->key };
+	unsigned int noio_flag;
+	int ret = 0;
+	int i;
+
+	if (WARN_ON_ONCE(key_usage_cnt > ARRAY_SIZE(key->krb5_tfms)))
+		return -EINVAL;
+
+	key->krb5_type = crypto_krb5_find_enctype(
+			     KRB5_ENCTYPE_AES256_CTS_HMAC_SHA384_192);
+	if (!key->krb5_type)
+		return -ENOPKG;
+
+	/*
+	 * Despite crypto_krb5_prepare_encryption() taking a gfp mask,
+	 * crypto_alloc_aead() inside of it allocates with GFP_KERNEL.
+	 */
+	noio_flag = memalloc_noio_save();
+	for (i = 0; i < key_usage_cnt; i++) {
+		key->krb5_tfms[i] = crypto_krb5_prepare_encryption(
+					key->krb5_type, &TK, key_usages[i],
+					GFP_NOIO);
+		if (IS_ERR(key->krb5_tfms[i])) {
+			ret = PTR_ERR(key->krb5_tfms[i]);
+			key->krb5_tfms[i] = NULL;
+			goto out_flag;
+		}
+	}
+
+out_flag:
+	memalloc_noio_restore(noio_flag);
+	return ret;
+}
+
+int ceph_crypto_key_prepare(struct ceph_crypto_key *key,
+			    const u32 *key_usages, int key_usage_cnt)
 {
 	switch (key->type) {
 	case CEPH_CRYPTO_NONE:
 		return 0; /* nothing to do */
 	case CEPH_CRYPTO_AES:
 		return set_aes_tfm(key);
+	case CEPH_CRYPTO_AES256KRB5:
+		return set_krb5_tfms(key, key_usages, key_usage_cnt);
 	default:
 		return -ENOTSUPP;
 	}
@@ -123,12 +164,25 @@ int ceph_crypto_key_unarmor(struct ceph_crypto_key *key, const char *inkey)
 
 void ceph_crypto_key_destroy(struct ceph_crypto_key *key)
 {
-	if (key) {
-		kfree_sensitive(key->key);
-		key->key = NULL;
-		if (key->tfm) {
-			crypto_free_sync_skcipher(key->tfm);
-			key->tfm = NULL;
+	int i;
+
+	if (!key)
+		return;
+
+	kfree_sensitive(key->key);
+	key->key = NULL;
+
+	if (key->type == CEPH_CRYPTO_AES) {
+		if (key->aes_tfm) {
+			crypto_free_sync_skcipher(key->aes_tfm);
+			key->aes_tfm = NULL;
+		}
+	} else if (key->type == CEPH_CRYPTO_AES256KRB5) {
+		for (i = 0; i < ARRAY_SIZE(key->krb5_tfms); i++) {
+			if (key->krb5_tfms[i]) {
+				crypto_free_aead(key->krb5_tfms[i]);
+				key->krb5_tfms[i] = NULL;
+			}
 		}
 	}
 }
@@ -208,7 +262,7 @@ static void teardown_sgtable(struct sg_table *sgt)
 static int ceph_aes_crypt(const struct ceph_crypto_key *key, bool encrypt,
 			  void *buf, int buf_len, int in_len, int *pout_len)
 {
-	SYNC_SKCIPHER_REQUEST_ON_STACK(req, key->tfm);
+	SYNC_SKCIPHER_REQUEST_ON_STACK(req, key->aes_tfm);
 	struct sg_table sgt;
 	struct scatterlist prealloc_sg;
 	char iv[AES_BLOCK_SIZE] __aligned(8);
@@ -224,7 +278,7 @@ static int ceph_aes_crypt(const struct ceph_crypto_key *key, bool encrypt,
 		return ret;
 
 	memcpy(iv, aes_iv, AES_BLOCK_SIZE);
-	skcipher_request_set_sync_tfm(req, key->tfm);
+	skcipher_request_set_sync_tfm(req, key->aes_tfm);
 	skcipher_request_set_callback(req, 0, NULL, NULL);
 	skcipher_request_set_crypt(req, sgt.sgl, sgt.sgl, crypt_len, iv);
 
@@ -269,7 +323,68 @@ out_sgt:
 	return ret;
 }
 
-int ceph_crypt(const struct ceph_crypto_key *key, bool encrypt,
+static int ceph_krb5_encrypt(const struct ceph_crypto_key *key, int usage_slot,
+			     void *buf, int buf_len, int in_len, int *pout_len)
+{
+	struct sg_table sgt;
+	struct scatterlist prealloc_sg;
+	int ret;
+
+	if (WARN_ON_ONCE(usage_slot >= ARRAY_SIZE(key->krb5_tfms)))
+		return -EINVAL;
+
+	ret = setup_sgtable(&sgt, &prealloc_sg, buf, buf_len);
+	if (ret)
+		return ret;
+
+	ret = crypto_krb5_encrypt(key->krb5_type, key->krb5_tfms[usage_slot],
+				  sgt.sgl, sgt.nents, buf_len, AES_BLOCK_SIZE,
+				  in_len, false);
+	if (ret < 0) {
+		pr_err("%s encrypt failed: %d\n", __func__, ret);
+		goto out_sgt;
+	}
+
+	*pout_len = ret;
+	ret = 0;
+
+out_sgt:
+	teardown_sgtable(&sgt);
+	return ret;
+}
+
+static int ceph_krb5_decrypt(const struct ceph_crypto_key *key, int usage_slot,
+			     void *buf, int buf_len, int in_len, int *pout_len)
+{
+	struct sg_table sgt;
+	struct scatterlist prealloc_sg;
+	size_t data_off = 0;
+	size_t data_len = in_len;
+	int ret;
+
+	if (WARN_ON_ONCE(usage_slot >= ARRAY_SIZE(key->krb5_tfms)))
+		return -EINVAL;
+
+	ret = setup_sgtable(&sgt, &prealloc_sg, buf, in_len);
+	if (ret)
+		return ret;
+
+	ret = crypto_krb5_decrypt(key->krb5_type, key->krb5_tfms[usage_slot],
+				  sgt.sgl, sgt.nents, &data_off, &data_len);
+	if (ret) {
+		pr_err("%s decrypt failed: %d\n", __func__, ret);
+		goto out_sgt;
+	}
+
+	WARN_ON(data_off != AES_BLOCK_SIZE);
+	*pout_len = data_len;
+
+out_sgt:
+	teardown_sgtable(&sgt);
+	return ret;
+}
+
+int ceph_crypt(const struct ceph_crypto_key *key, int usage_slot, bool encrypt,
 	       void *buf, int buf_len, int in_len, int *pout_len)
 {
 	switch (key->type) {
@@ -279,6 +394,12 @@ int ceph_crypt(const struct ceph_crypto_key *key, bool encrypt,
 	case CEPH_CRYPTO_AES:
 		return ceph_aes_crypt(key, encrypt, buf, buf_len, in_len,
 				      pout_len);
+	case CEPH_CRYPTO_AES256KRB5:
+		return encrypt ?
+		    ceph_krb5_encrypt(key, usage_slot, buf, buf_len, in_len,
+				      pout_len) :
+		    ceph_krb5_decrypt(key, usage_slot, buf, buf_len, in_len,
+				      pout_len);
 	default:
 		return -ENOTSUPP;
 	}
@@ -290,6 +411,9 @@ int ceph_crypt_data_offset(const struct ceph_crypto_key *key)
 	case CEPH_CRYPTO_NONE:
 	case CEPH_CRYPTO_AES:
 		return 0;
+	case CEPH_CRYPTO_AES256KRB5:
+		/* confounder */
+		return AES_BLOCK_SIZE;
 	default:
 		BUG();
 	}
@@ -304,6 +428,9 @@ int ceph_crypt_buflen(const struct ceph_crypto_key *key, int data_len)
 		/* PKCS#7 padding at the end */
 		return data_len + AES_BLOCK_SIZE -
 		       (data_len & (AES_BLOCK_SIZE - 1));
+	case CEPH_CRYPTO_AES256KRB5:
+		/* confounder at the beginning and 192-bit HMAC at the end */
+		return AES_BLOCK_SIZE + data_len + 24;
 	default:
 		BUG();
 	}
diff --git a/net/ceph/crypto.h b/net/ceph/crypto.h
index 2b8f8f68ff7a..2c37c54d0f56 100644
--- a/net/ceph/crypto.h
+++ b/net/ceph/crypto.h
@@ -5,7 +5,7 @@
 #include <linux/ceph/types.h>
 #include <linux/ceph/buffer.h>
 
-#define CEPH_MAX_KEY_LEN		16
+#define CEPH_MAX_KEY_LEN		32
 #define CEPH_MAX_CON_SECRET_LEN		64
 
 /*
@@ -16,10 +16,18 @@ struct ceph_crypto_key {
 	struct ceph_timespec created;
 	int len;
 	void *key;
-	struct crypto_sync_skcipher *tfm;
+
+	union {
+		struct crypto_sync_skcipher *aes_tfm;
+		struct {
+			const struct krb5_enctype *krb5_type;
+			struct crypto_aead *krb5_tfms[3];
+		};
+	};
 };
 
-int ceph_crypto_key_prepare(struct ceph_crypto_key *key);
+int ceph_crypto_key_prepare(struct ceph_crypto_key *key,
+			    const u32 *key_usages, int key_usage_cnt);
 int ceph_crypto_key_clone(struct ceph_crypto_key *dst,
 			  const struct ceph_crypto_key *src);
 int ceph_crypto_key_decode(struct ceph_crypto_key *key, void **p, void *end);
@@ -27,7 +35,7 @@ int ceph_crypto_key_unarmor(struct ceph_crypto_key *key, const char *in);
 void ceph_crypto_key_destroy(struct ceph_crypto_key *key);
 
 /* crypto.c */
-int ceph_crypt(const struct ceph_crypto_key *key, bool encrypt,
+int ceph_crypt(const struct ceph_crypto_key *key, int usage_slot, bool encrypt,
 	       void *buf, int buf_len, int in_len, int *pout_len);
 int ceph_crypt_data_offset(const struct ceph_crypto_key *key);
 int ceph_crypt_buflen(const struct ceph_crypto_key *key, int data_len);