keys: add new key-type encrypted

Define a new kernel key-type called 'encrypted'. Encrypted keys are kernel
generated random numbers, which are encrypted/decrypted with a 'trusted'
symmetric key. Encrypted keys are created/encrypted/decrypted in the kernel.
Userspace only ever sees/stores encrypted blobs.

Changelog:
- bug fix: replaced master-key rcu based locking with semaphore
  (reported by David Howells)
- Removed memset of crypto_shash_digest() digest output
- Replaced verification of 'key-type:key-desc' using strcspn(), with
  one based on string constants.
- Moved documentation to Documentation/keys-trusted-encrypted.txt
- Replace hash with shash (based on comments by David Howells)
- Make lengths/counts size_t where possible (based on comments by David Howells)
  Could not convert most lengths, as crypto expects 'unsigned int'
  (size_t: on 32 bit is defined as unsigned int, but on 64 bit is unsigned long)
- Add 'const' where possible (based on comments by David Howells)
- allocate derived_buf dynamically to support arbitrary length master key
  (fixed by Roberto Sassu)
- wait until late_initcall for crypto libraries to be registered
- cleanup security/Kconfig
- Add missing 'update' keyword (reported/fixed by Roberto Sassu)
- Free epayload on failure to create key (reported/fixed by Roberto Sassu)
- Increase the data size limit (requested by Roberto Sassu)
- Crypto return codes are always 0 on success and negative on failure,
  remove unnecessary tests.
- Replaced kzalloc() with kmalloc()

Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Signed-off-by: David Safford <safford@watson.ibm.com>
Reviewed-by: Roberto Sassu <roberto.sassu@polito.it>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 907 insertions, 0 deletions

diff --git a/security/keys/encrypted_defined.c b/security/keys/encrypted_defined.c
new file mode 100644
index 000000000000..0e558dcad92f
--- /dev/null
+++ b/security/keys/encrypted_defined.c
@@ -0,0 +1,907 @@
+/*
+ * Copyright (C) 2010 IBM Corporation
+ *
+ * Author:
+ * Mimi Zohar <zohar@us.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 2 of the License.
+ *
+ * See Documentation/keys-trusted-encrypted.txt
+ */
+
+#include <linux/uaccess.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/parser.h>
+#include <linux/string.h>
+#include <keys/user-type.h>
+#include <keys/trusted-type.h>
+#include <keys/encrypted-type.h>
+#include <linux/key-type.h>
+#include <linux/random.h>
+#include <linux/rcupdate.h>
+#include <linux/scatterlist.h>
+#include <linux/crypto.h>
+#include <crypto/hash.h>
+#include <crypto/sha.h>
+#include <crypto/aes.h>
+
+#include "encrypted_defined.h"
+
+#define KEY_TRUSTED_PREFIX "trusted:"
+#define KEY_TRUSTED_PREFIX_LEN (sizeof (KEY_TRUSTED_PREFIX) - 1)
+#define KEY_USER_PREFIX "user:"
+#define KEY_USER_PREFIX_LEN (sizeof (KEY_USER_PREFIX) - 1)
+
+#define HASH_SIZE SHA256_DIGEST_SIZE
+#define MAX_DATA_SIZE 4096
+#define MIN_DATA_SIZE  20
+
+static const char hash_alg[] = "sha256";
+static const char hmac_alg[] = "hmac(sha256)";
+static const char blkcipher_alg[] = "cbc(aes)";
+static unsigned int ivsize;
+static int blksize;
+
+struct sdesc {
+        struct shash_desc shash;
+        char ctx[];
+};
+
+static struct crypto_shash *hashalg;
+static struct crypto_shash *hmacalg;
+
+enum {
+        Opt_err = -1, Opt_new, Opt_load, Opt_update
+};
+
+static const match_table_t key_tokens = {
+        {Opt_new, "new"},
+        {Opt_load, "load"},
+        {Opt_update, "update"},
+        {Opt_err, NULL}
+};
+
+static int aes_get_sizes(void)
+{
+        struct crypto_blkcipher *tfm;
+
+        tfm = crypto_alloc_blkcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
+        if (IS_ERR(tfm)) {
+                pr_err("encrypted_key: failed to alloc_cipher (%ld)\n",
+                       PTR_ERR(tfm));
+                return PTR_ERR(tfm);
+        }
+        ivsize = crypto_blkcipher_ivsize(tfm);
+        blksize = crypto_blkcipher_blocksize(tfm);
+        crypto_free_blkcipher(tfm);
+        return 0;
+}
+
+/*
+ * valid_master_desc - verify the 'key-type:desc' of a new/updated master-key
+ *
+ * key-type:= "trusted:" | "encrypted:"
+ * desc:= master-key description
+ *
+ * Verify that 'key-type' is valid and that 'desc' exists. On key update,
+ * only the master key description is permitted to change, not the key-type.
+ * The key-type remains constant.
+ *
+ * On success returns 0, otherwise -EINVAL.
+ */
+static int valid_master_desc(const char *new_desc, const char *orig_desc)
+{
+        if (!memcmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN)) {
+                if (strlen(new_desc) == KEY_TRUSTED_PREFIX_LEN)
+                        goto out;
+                if (orig_desc)
+                        if (memcmp(new_desc, orig_desc, KEY_TRUSTED_PREFIX_LEN))
+                                goto out;
+        } else if (!memcmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN)) {
+                if (strlen(new_desc) == KEY_USER_PREFIX_LEN)
+                        goto out;
+                if (orig_desc)
+                        if (memcmp(new_desc, orig_desc, KEY_USER_PREFIX_LEN))
+                                goto out;
+        } else
+                goto out;
+        return 0;
+out:
+        return -EINVAL;
+}
+
+/*
+ * datablob_parse - parse the keyctl data
+ *
+ * datablob format:
+ * new <master-key name> <decrypted data length>
+ * load <master-key name> <decrypted data length> <encrypted iv + data>
+ * update <new-master-key name>
+ *
+ * Tokenizes a copy of the keyctl data, returning a pointer to each token,
+ * which is null terminated.
+ *
+ * On success returns 0, otherwise -EINVAL.
+ */
+static int datablob_parse(char *datablob, char **master_desc,
+                          char **decrypted_datalen, char **hex_encoded_iv,
+                          char **hex_encoded_data)
+{
+        substring_t args[MAX_OPT_ARGS];
+        int ret = -EINVAL;
+        int key_cmd;
+        char *p;
+
+        p = strsep(&datablob, " \t");
+        if (!p)
+                return ret;
+        key_cmd = match_token(p, key_tokens, args);
+
+        *master_desc = strsep(&datablob, " \t");
+        if (!*master_desc)
+                goto out;
+
+        if (valid_master_desc(*master_desc, NULL) < 0)
+                goto out;
+
+        if (decrypted_datalen) {
+                *decrypted_datalen = strsep(&datablob, " \t");
+                if (!*decrypted_datalen)
+                        goto out;
+        }
+
+        switch (key_cmd) {
+        case Opt_new:
+                if (!decrypted_datalen)
+                        break;
+                ret = 0;
+                break;
+        case Opt_load:
+                if (!decrypted_datalen)
+                        break;
+                *hex_encoded_iv = strsep(&datablob, " \t");
+                if (!*hex_encoded_iv)
+                        break;
+                *hex_encoded_data = *hex_encoded_iv + (2 * ivsize) + 2;
+                ret = 0;
+                break;
+        case Opt_update:
+                if (decrypted_datalen)
+                        break;
+                ret = 0;
+                break;
+        case Opt_err:
+                break;
+        }
+out:
+        return ret;
+}
+
+/*
+ * datablob_format - format as an ascii string, before copying to userspace
+ */
+static char *datablob_format(struct encrypted_key_payload *epayload,
+                             size_t asciiblob_len)
+{
+        char *ascii_buf, *bufp;
+        u8 *iv = epayload->iv;
+        int len;
+        int i;
+
+        ascii_buf = kmalloc(asciiblob_len + 1, GFP_KERNEL);
+        if (!ascii_buf)
+                goto out;
+
+        ascii_buf[asciiblob_len] = '\0';
+
+        /* copy datablob master_desc and datalen strings */
+        len = sprintf(ascii_buf, "%s %s ", epayload->master_desc,
+                      epayload->datalen);
+
+        /* convert the hex encoded iv, encrypted-data and HMAC to ascii */
+        bufp = &ascii_buf[len];
+        for (i = 0; i < (asciiblob_len - len) / 2; i++)
+                bufp = pack_hex_byte(bufp, iv[i]);
+out:
+        return ascii_buf;
+}
+
+/*
+ * request_trusted_key - request the trusted key
+ *
+ * Trusted keys are sealed to PCRs and other metadata. Although userspace
+ * manages both trusted/encrypted key-types, like the encrypted key type
+ * data, trusted key type data is not visible decrypted from userspace.
+ */
+static struct key *request_trusted_key(const char *trusted_desc,
+                                       u8 **master_key,
+                                       unsigned int *master_keylen)
+{
+        struct trusted_key_payload *tpayload;
+        struct key *tkey;
+
+        tkey = request_key(&key_type_trusted, trusted_desc, NULL);
+        if (IS_ERR(tkey))
+                goto error;
+
+        down_read(&tkey->sem);
+        tpayload = rcu_dereference(tkey->payload.data);
+        *master_key = tpayload->key;
+        *master_keylen = tpayload->key_len;
+error:
+        return tkey;
+}
+
+/*
+ * request_user_key - request the user key
+ *
+ * Use a user provided key to encrypt/decrypt an encrypted-key.
+ */
+static struct key *request_user_key(const char *master_desc, u8 **master_key,
+                                    unsigned int *master_keylen)
+{
+        struct user_key_payload *upayload;
+        struct key *ukey;
+
+        ukey = request_key(&key_type_user, master_desc, NULL);
+        if (IS_ERR(ukey))
+                goto error;
+
+        down_read(&ukey->sem);
+        upayload = rcu_dereference(ukey->payload.data);
+        *master_key = upayload->data;
+        *master_keylen = upayload->datalen;
+error:
+        return ukey;
+}
+
+static struct sdesc *init_sdesc(struct crypto_shash *alg)
+{
+        struct sdesc *sdesc;
+        int size;
+
+        size = sizeof(struct shash_desc) + crypto_shash_descsize(alg);
+        sdesc = kmalloc(size, GFP_KERNEL);
+        if (!sdesc)
+                return ERR_PTR(-ENOMEM);
+        sdesc->shash.tfm = alg;
+        sdesc->shash.flags = 0x0;
+        return sdesc;
+}
+
+static int calc_hmac(u8 *digest, const u8 *key, const unsigned int keylen,
+                     const u8 *buf, const unsigned int buflen)
+{
+        struct sdesc *sdesc;
+        int ret;
+
+        sdesc = init_sdesc(hmacalg);
+        if (IS_ERR(sdesc)) {
+                pr_info("encrypted_key: can't alloc %s\n", hmac_alg);
+                return PTR_ERR(sdesc);
+        }
+
+        ret = crypto_shash_setkey(hmacalg, key, keylen);
+        if (!ret)
+                ret = crypto_shash_digest(&sdesc->shash, buf, buflen, digest);
+        kfree(sdesc);
+        return ret;
+}
+
+static int calc_hash(u8 *digest, const u8 *buf, const unsigned int buflen)
+{
+        struct sdesc *sdesc;
+        int ret;
+
+        sdesc = init_sdesc(hashalg);
+        if (IS_ERR(sdesc)) {
+                pr_info("encrypted_key: can't alloc %s\n", hash_alg);
+                return PTR_ERR(sdesc);
+        }
+
+        ret = crypto_shash_digest(&sdesc->shash, buf, buflen, digest);
+        kfree(sdesc);
+        return ret;
+}
+
+enum derived_key_type { ENC_KEY, AUTH_KEY };
+
+/* Derive authentication/encryption key from trusted key */
+static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
+                           const u8 *master_key,
+                           const unsigned int master_keylen)
+{
+        u8 *derived_buf;
+        unsigned int derived_buf_len;
+        int ret;
+
+        derived_buf_len = strlen("AUTH_KEY") + 1 + master_keylen;
+        if (derived_buf_len < HASH_SIZE)
+                derived_buf_len = HASH_SIZE;
+
+        derived_buf = kzalloc(derived_buf_len, GFP_KERNEL);
+        if (!derived_buf) {
+                pr_err("encrypted_key: out of memory\n");
+                return -ENOMEM;
+        }
+        if (key_type)
+                strcpy(derived_buf, "AUTH_KEY");
+        else
+                strcpy(derived_buf, "ENC_KEY");
+
+        memcpy(derived_buf + strlen(derived_buf) + 1, master_key,
+               master_keylen);
+        ret = calc_hash(derived_key, derived_buf, derived_buf_len);
+        kfree(derived_buf);
+        return ret;
+}
+
+static int init_blkcipher_desc(struct blkcipher_desc *desc, const u8 *key,
+                               const unsigned int key_len, const u8 *iv,
+                               const unsigned int ivsize)
+{
+        int ret;
+
+        desc->tfm = crypto_alloc_blkcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
+        if (IS_ERR(desc->tfm)) {
+                pr_err("encrypted_key: failed to load %s transform (%ld)\n",
+                       blkcipher_alg, PTR_ERR(desc->tfm));
+                return PTR_ERR(desc->tfm);
+        }
+        desc->flags = 0;
+
+        ret = crypto_blkcipher_setkey(desc->tfm, key, key_len);
+        if (ret < 0) {
+                pr_err("encrypted_key: failed to setkey (%d)\n", ret);
+                crypto_free_blkcipher(desc->tfm);
+                return ret;
+        }
+        crypto_blkcipher_set_iv(desc->tfm, iv, ivsize);
+        return 0;
+}
+
+static struct key *request_master_key(struct encrypted_key_payload *epayload,
+                                      u8 **master_key,
+                                      unsigned int *master_keylen)
+{
+        struct key *mkey = NULL;
+
+        if (!strncmp(epayload->master_desc, KEY_TRUSTED_PREFIX,
+                     KEY_TRUSTED_PREFIX_LEN)) {
+                mkey = request_trusted_key(epayload->master_desc +
+                                           KEY_TRUSTED_PREFIX_LEN,
+                                           master_key, master_keylen);
+        } else if (!strncmp(epayload->master_desc, KEY_USER_PREFIX,
+                            KEY_USER_PREFIX_LEN)) {
+                mkey = request_user_key(epayload->master_desc +
+                                        KEY_USER_PREFIX_LEN,
+                                        master_key, master_keylen);
+        } else
+                goto out;
+
+        if (IS_ERR(mkey))
+                pr_info("encrypted_key: key %s not found",
+                        epayload->master_desc);
+        if (mkey)
+                dump_master_key(*master_key, *master_keylen);
+out:
+        return mkey;
+}
+
+/* Before returning data to userspace, encrypt decrypted data. */
+static int derived_key_encrypt(struct encrypted_key_payload *epayload,
+                               const u8 *derived_key,
+                               const unsigned int derived_keylen)
+{
+        struct scatterlist sg_in[2];
+        struct scatterlist sg_out[1];
+        struct blkcipher_desc desc;
+        unsigned int encrypted_datalen;
+        unsigned int padlen;
+        char pad[16];
+        int ret;
+
+        encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
+        padlen = encrypted_datalen - epayload->decrypted_datalen;
+
+        ret = init_blkcipher_desc(&desc, derived_key, derived_keylen,
+                                  epayload->iv, ivsize);
+        if (ret < 0)
+                goto out;
+        dump_decrypted_data(epayload);
+
+        memset(pad, 0, sizeof pad);
+        sg_init_table(sg_in, 2);
+        sg_set_buf(&sg_in[0], epayload->decrypted_data,
+                   epayload->decrypted_datalen);
+        sg_set_buf(&sg_in[1], pad, padlen);
+
+        sg_init_table(sg_out, 1);
+        sg_set_buf(sg_out, epayload->encrypted_data, encrypted_datalen);
+
+        ret = crypto_blkcipher_encrypt(&desc, sg_out, sg_in, encrypted_datalen);
+        crypto_free_blkcipher(desc.tfm);
+        if (ret < 0)
+                pr_err("encrypted_key: failed to encrypt (%d)\n", ret);
+        else
+                dump_encrypted_data(epayload, encrypted_datalen);
+out:
+        return ret;
+}
+
+static int datablob_hmac_append(struct encrypted_key_payload *epayload,
+                                const u8 *master_key,
+                                const unsigned int master_keylen)
+{
+        u8 derived_key[HASH_SIZE];
+        u8 *digest;
+        int ret;
+
+        ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
+        if (ret < 0)
+                goto out;
+
+        digest = epayload->master_desc + epayload->datablob_len;
+        ret = calc_hmac(digest, derived_key, sizeof derived_key,
+                        epayload->master_desc, epayload->datablob_len);
+        if (!ret)
+                dump_hmac(NULL, digest, HASH_SIZE);
+out:
+        return ret;
+}
+
+/* verify HMAC before decrypting encrypted key */
+static int datablob_hmac_verify(struct encrypted_key_payload *epayload,
+                                const u8 *master_key,
+                                const unsigned int master_keylen)
+{
+        u8 derived_key[HASH_SIZE];
+        u8 digest[HASH_SIZE];
+        int ret;
+
+        ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
+        if (ret < 0)
+                goto out;
+
+        ret = calc_hmac(digest, derived_key, sizeof derived_key,
+                        epayload->master_desc, epayload->datablob_len);
+        if (ret < 0)
+                goto out;
+        ret = memcmp(digest, epayload->master_desc + epayload->datablob_len,
+                     sizeof digest);
+        if (ret) {
+                ret = -EINVAL;
+                dump_hmac("datablob",
+                          epayload->master_desc + epayload->datablob_len,
+                          HASH_SIZE);
+                dump_hmac("calc", digest, HASH_SIZE);
+        }
+out:
+        return ret;
+}
+
+static int derived_key_decrypt(struct encrypted_key_payload *epayload,
+                               const u8 *derived_key,
+                               const unsigned int derived_keylen)
+{
+        struct scatterlist sg_in[1];
+        struct scatterlist sg_out[2];
+        struct blkcipher_desc desc;
+        unsigned int encrypted_datalen;
+        char pad[16];
+        int ret;
+
+        encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
+        ret = init_blkcipher_desc(&desc, derived_key, derived_keylen,
+                                  epayload->iv, ivsize);
+        if (ret < 0)
+                goto out;
+        dump_encrypted_data(epayload, encrypted_datalen);
+
+        memset(pad, 0, sizeof pad);
+        sg_init_table(sg_in, 1);
+        sg_init_table(sg_out, 2);
+        sg_set_buf(sg_in, epayload->encrypted_data, encrypted_datalen);
+        sg_set_buf(&sg_out[0], epayload->decrypted_data,
+                   (unsigned int)epayload->decrypted_datalen);
+        sg_set_buf(&sg_out[1], pad, sizeof pad);
+
+        ret = crypto_blkcipher_decrypt(&desc, sg_out, sg_in, encrypted_datalen);
+        crypto_free_blkcipher(desc.tfm);
+        if (ret < 0)
+                goto out;
+        dump_decrypted_data(epayload);
+out:
+        return ret;
+}
+
+/* Allocate memory for decrypted key and datablob. */
+static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
+                                                         const char *master_desc,
+                                                         const char *datalen)
+{
+        struct encrypted_key_payload *epayload = NULL;
+        unsigned short datablob_len;
+        unsigned short decrypted_datalen;
+        unsigned int encrypted_datalen;
+        long dlen;
+        int ret;
+
+        ret = strict_strtol(datalen, 10, &dlen);
+        if (ret < 0 || dlen < MIN_DATA_SIZE || dlen > MAX_DATA_SIZE)
+                return ERR_PTR(-EINVAL);
+
+        decrypted_datalen = dlen;
+        encrypted_datalen = roundup(decrypted_datalen, blksize);
+
+        datablob_len = strlen(master_desc) + 1 + strlen(datalen) + 1
+            + ivsize + 1 + encrypted_datalen;
+
+        ret = key_payload_reserve(key, decrypted_datalen + datablob_len
+                                  + HASH_SIZE + 1);
+        if (ret < 0)
+                return ERR_PTR(ret);
+
+        epayload = kzalloc(sizeof(*epayload) + decrypted_datalen +
+                           datablob_len + HASH_SIZE + 1, GFP_KERNEL);
+        if (!epayload)
+                return ERR_PTR(-ENOMEM);
+
+        epayload->decrypted_datalen = decrypted_datalen;
+        epayload->datablob_len = datablob_len;
+        return epayload;
+}
+
+static int encrypted_key_decrypt(struct encrypted_key_payload *epayload,
+                                 const char *hex_encoded_iv,
+                                 const char *hex_encoded_data)
+{
+        struct key *mkey;
+        u8 derived_key[HASH_SIZE];
+        u8 *master_key;
+        u8 *hmac;
+        unsigned int master_keylen;
+        unsigned int encrypted_datalen;
+        int ret;
+
+        encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
+        hex2bin(epayload->iv, hex_encoded_iv, ivsize);
+        hex2bin(epayload->encrypted_data, hex_encoded_data, encrypted_datalen);
+
+        hmac = epayload->master_desc + epayload->datablob_len;
+        hex2bin(hmac, hex_encoded_data + (encrypted_datalen * 2), HASH_SIZE);
+
+        mkey = request_master_key(epayload, &master_key, &master_keylen);
+        if (IS_ERR(mkey))
+                return PTR_ERR(mkey);
+
+        ret = datablob_hmac_verify(epayload, master_key, master_keylen);
+        if (ret < 0) {
+                pr_err("encrypted_key: bad hmac (%d)\n", ret);
+                goto out;
+        }
+
+        ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
+        if (ret < 0)
+                goto out;
+
+        ret = derived_key_decrypt(epayload, derived_key, sizeof derived_key);
+        if (ret < 0)
+                pr_err("encrypted_key: failed to decrypt key (%d)\n", ret);
+out:
+        up_read(&mkey->sem);
+        key_put(mkey);
+        return ret;
+}
+
+static void __ekey_init(struct encrypted_key_payload *epayload,
+                        const char *master_desc, const char *datalen)
+{
+        epayload->master_desc = epayload->decrypted_data
+            + epayload->decrypted_datalen;
+        epayload->datalen = epayload->master_desc + strlen(master_desc) + 1;
+        epayload->iv = epayload->datalen + strlen(datalen) + 1;
+        epayload->encrypted_data = epayload->iv + ivsize + 1;
+
+        memcpy(epayload->master_desc, master_desc, strlen(master_desc));
+        memcpy(epayload->datalen, datalen, strlen(datalen));
+}
+
+/*
+ * encrypted_init - initialize an encrypted key
+ *
+ * For a new key, use a random number for both the iv and data
+ * itself.  For an old key, decrypt the hex encoded data.
+ */
+static int encrypted_init(struct encrypted_key_payload *epayload,
+                          const char *master_desc, const char *datalen,
+                          const char *hex_encoded_iv,
+                          const char *hex_encoded_data)
+{
+        int ret = 0;
+
+        __ekey_init(epayload, master_desc, datalen);
+        if (!hex_encoded_data) {
+                get_random_bytes(epayload->iv, ivsize);
+
+                get_random_bytes(epayload->decrypted_data,
+                                 epayload->decrypted_datalen);
+        } else
+                ret = encrypted_key_decrypt(epayload, hex_encoded_iv,
+                                            hex_encoded_data);
+        return ret;
+}
+
+/*
+ * encrypted_instantiate - instantiate an encrypted key
+ *
+ * Decrypt an existing encrypted datablob or create a new encrypted key
+ * based on a kernel random number.
+ *
+ * On success, return 0. Otherwise return errno.
+ */
+static int encrypted_instantiate(struct key *key, const void *data,
+                                 size_t datalen)
+{
+        struct encrypted_key_payload *epayload = NULL;
+        char *datablob = NULL;
+        char *master_desc = NULL;
+        char *decrypted_datalen = NULL;
+        char *hex_encoded_iv = NULL;
+        char *hex_encoded_data = NULL;
+        int ret;
+
+        if (datalen <= 0 || datalen > 32767 || !data)
+                return -EINVAL;
+
+        datablob = kmalloc(datalen + 1, GFP_KERNEL);
+        if (!datablob)
+                return -ENOMEM;
+        datablob[datalen] = 0;
+        memcpy(datablob, data, datalen);
+        ret = datablob_parse(datablob, &master_desc, &decrypted_datalen,
+                             &hex_encoded_iv, &hex_encoded_data);
+        if (ret < 0)
+                goto out;
+
+        epayload = encrypted_key_alloc(key, master_desc, decrypted_datalen);
+        if (IS_ERR(epayload)) {
+                ret = PTR_ERR(epayload);
+                goto out;
+        }
+        ret = encrypted_init(epayload, master_desc, decrypted_datalen,
+                             hex_encoded_iv, hex_encoded_data);
+        if (ret < 0) {
+                kfree(epayload);
+                goto out;
+        }
+
+        rcu_assign_pointer(key->payload.data, epayload);
+out:
+        kfree(datablob);
+        return ret;
+}
+
+static void encrypted_rcu_free(struct rcu_head *rcu)
+{
+        struct encrypted_key_payload *epayload;
+
+        epayload = container_of(rcu, struct encrypted_key_payload, rcu);
+        memset(epayload->decrypted_data, 0, epayload->decrypted_datalen);
+        kfree(epayload);
+}
+
+/*
+ * encrypted_update - update the master key description
+ *
+ * Change the master key description for an existing encrypted key.
+ * The next read will return an encrypted datablob using the new
+ * master key description.
+ *
+ * On success, return 0. Otherwise return errno.
+ */
+static int encrypted_update(struct key *key, const void *data, size_t datalen)
+{
+        struct encrypted_key_payload *epayload = key->payload.data;
+        struct encrypted_key_payload *new_epayload;
+        char *buf;
+        char *new_master_desc = NULL;
+        int ret = 0;
+
+        if (datalen <= 0 || datalen > 32767 || !data)
+                return -EINVAL;
+
+        buf = kmalloc(datalen + 1, GFP_KERNEL);
+        if (!buf)
+                return -ENOMEM;
+
+        buf[datalen] = 0;
+        memcpy(buf, data, datalen);
+        ret = datablob_parse(buf, &new_master_desc, NULL, NULL, NULL);
+        if (ret < 0)
+                goto out;
+
+        ret = valid_master_desc(new_master_desc, epayload->master_desc);
+        if (ret < 0)
+                goto out;
+
+        new_epayload = encrypted_key_alloc(key, new_master_desc,
+                                           epayload->datalen);
+        if (IS_ERR(new_epayload)) {
+                ret = PTR_ERR(new_epayload);
+                goto out;
+        }
+
+        __ekey_init(new_epayload, new_master_desc, epayload->datalen);
+
+        memcpy(new_epayload->iv, epayload->iv, ivsize);
+        memcpy(new_epayload->decrypted_data, epayload->decrypted_data,
+               epayload->decrypted_datalen);
+
+        rcu_assign_pointer(key->payload.data, new_epayload);
+        call_rcu(&epayload->rcu, encrypted_rcu_free);
+out:
+        kfree(buf);
+        return ret;
+}
+
+/*
+ * encrypted_read - format and copy the encrypted data to userspace
+ *
+ * The resulting datablob format is:
+ * <master-key name> <decrypted data length> <encrypted iv> <encrypted data>
+ *
+ * On success, return to userspace the encrypted key datablob size.
+ */
+static long encrypted_read(const struct key *key, char __user *buffer,
+                           size_t buflen)
+{
+        struct encrypted_key_payload *epayload;
+        struct key *mkey;
+        u8 *master_key;
+        unsigned int master_keylen;
+        char derived_key[HASH_SIZE];
+        char *ascii_buf;
+        size_t asciiblob_len;
+        int ret;
+
+        epayload = rcu_dereference_protected(key->payload.data,
+                                  rwsem_is_locked(&((struct key *)key)->sem));
+
+        /* returns the hex encoded iv, encrypted-data, and hmac as ascii */
+        asciiblob_len = epayload->datablob_len + ivsize + 1
+            + roundup(epayload->decrypted_datalen, blksize)
+            + (HASH_SIZE * 2);
+
+        if (!buffer || buflen < asciiblob_len)
+                return asciiblob_len;
+
+        mkey = request_master_key(epayload, &master_key, &master_keylen);
+        if (IS_ERR(mkey))
+                return PTR_ERR(mkey);
+
+        ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
+        if (ret < 0)
+                goto out;
+
+        ret = derived_key_encrypt(epayload, derived_key, sizeof derived_key);
+        if (ret < 0)
+                goto out;
+
+        ret = datablob_hmac_append(epayload, master_key, master_keylen);
+        if (ret < 0)
+                goto out;
+
+        ascii_buf = datablob_format(epayload, asciiblob_len);
+        if (!ascii_buf) {
+                ret = -ENOMEM;
+                goto out;
+        }
+
+        up_read(&mkey->sem);
+        key_put(mkey);
+
+        if (copy_to_user(buffer, ascii_buf, asciiblob_len) != 0)
+                ret = -EFAULT;
+        kfree(ascii_buf);
+
+        return asciiblob_len;
+out:
+        up_read(&mkey->sem);
+        key_put(mkey);
+        return ret;
+}
+
+/*
+ * encrypted_destroy - before freeing the key, clear the decrypted data
+ *
+ * Before freeing the key, clear the memory containing the decrypted
+ * key data.
+ */
+static void encrypted_destroy(struct key *key)
+{
+        struct encrypted_key_payload *epayload = key->payload.data;
+
+        if (!epayload)
+                return;
+
+        memset(epayload->decrypted_data, 0, epayload->decrypted_datalen);
+        kfree(key->payload.data);
+}
+
+struct key_type key_type_encrypted = {
+        .name = "encrypted",
+        .instantiate = encrypted_instantiate,
+        .update = encrypted_update,
+        .match = user_match,
+        .destroy = encrypted_destroy,
+        .describe = user_describe,
+        .read = encrypted_read,
+};
+EXPORT_SYMBOL_GPL(key_type_encrypted);
+
+static void encrypted_shash_release(void)
+{
+        if (hashalg)
+                crypto_free_shash(hashalg);
+        if (hmacalg)
+                crypto_free_shash(hmacalg);
+}
+
+static int __init encrypted_shash_alloc(void)
+{
+        int ret;
+
+        hmacalg = crypto_alloc_shash(hmac_alg, 0, CRYPTO_ALG_ASYNC);
+        if (IS_ERR(hmacalg)) {
+                pr_info("encrypted_key: could not allocate crypto %s\n",
+                        hmac_alg);
+                return PTR_ERR(hmacalg);
+        }
+
+        hashalg = crypto_alloc_shash(hash_alg, 0, CRYPTO_ALG_ASYNC);
+        if (IS_ERR(hashalg)) {
+                pr_info("encrypted_key: could not allocate crypto %s\n",
+                        hash_alg);
+                ret = PTR_ERR(hashalg);
+                goto hashalg_fail;
+        }
+
+        return 0;
+
+hashalg_fail:
+        crypto_free_shash(hmacalg);
+        return ret;
+}
+
+static int __init init_encrypted(void)
+{
+        int ret;
+
+        ret = encrypted_shash_alloc();
+        if (ret < 0)
+                return ret;
+        ret = register_key_type(&key_type_encrypted);
+        if (ret < 0)
+                goto out;
+        return aes_get_sizes();
+out:
+        encrypted_shash_release();
+        return ret;
+
+}
+
+static void __exit cleanup_encrypted(void)
+{
+        encrypted_shash_release();
+        unregister_key_type(&key_type_encrypted);
+}
+
+late_initcall(init_encrypted);
+module_exit(cleanup_encrypted);
+
+MODULE_LICENSE("GPL");