/*
 * Copyright (C) 2010 IBM Corporation
 * Copyright (C) 2010 Politecnico di Torino, Italy
 *                    TORSEC group -- http://security.polito.it
 *
 * Authors:
 * Mimi Zohar <zohar@us.ibm.com>
 * Roberto Sassu <roberto.sassu@polito.it>
 *
 * 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/security/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 <linux/err.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 <linux/ctype.h>
#include <crypto/hash.h>
#include <crypto/sha.h>
#include <crypto/aes.h>

#include "encrypted.h"
#include "ecryptfs_format.h"

static const char KEY_TRUSTED_PREFIX[] = "trusted:";
static const char KEY_USER_PREFIX[] = "user:";
static const char hash_alg[] = "sha256";
static const char hmac_alg[] = "hmac(sha256)";
static const char blkcipher_alg[] = "cbc(aes)";
static const char key_format_default[] = "default";
static const char key_format_ecryptfs[] = "ecryptfs";
static unsigned int ivsize;
static int blksize;

#define KEY_TRUSTED_PREFIX_LEN (sizeof (KEY_TRUSTED_PREFIX) - 1)
#define KEY_USER_PREFIX_LEN (sizeof (KEY_USER_PREFIX) - 1)
#define KEY_ECRYPTFS_DESC_LEN 16
#define HASH_SIZE SHA256_DIGEST_SIZE
#define MAX_DATA_SIZE 4096
#define MIN_DATA_SIZE  20

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
};

enum {
        Opt_error = -1, Opt_default, Opt_ecryptfs
};

static const match_table_t key_format_tokens = {
        {Opt_default, "default"},
        {Opt_ecryptfs, "ecryptfs"},
        {Opt_error, NULL}
};

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_ecryptfs_desc - verify the description of a new/loaded encrypted key
 *
 * The description of a encrypted key with format 'ecryptfs' must contain
 * exactly 16 hexadecimal characters.
 *
 */
static int valid_ecryptfs_desc(const char *ecryptfs_desc)
{
        int i;

        if (strlen(ecryptfs_desc) != KEY_ECRYPTFS_DESC_LEN) {
                pr_err("encrypted_key: key description must be %d hexadecimal "
                       "characters long\n", KEY_ECRYPTFS_DESC_LEN);
                return -EINVAL;
        }

        for (i = 0; i < KEY_ECRYPTFS_DESC_LEN; i++) {
                if (!isxdigit(ecryptfs_desc[i])) {
                        pr_err("encrypted_key: key description must contain "
                               "only hexadecimal characters\n");
                        return -EINVAL;
                }
        }

        return 0;
}

/*
 * valid_master_desc - verify the 'key-type:desc' of a new/updated master-key
 *
 * key-type:= "trusted:" | "user:"
 * 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 [<format>] <master-key name> <decrypted data length>
 * load [<format>] <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, const char **format,
                          char **master_desc, char **decrypted_datalen,
                          char **hex_encoded_iv)
{
        substring_t args[MAX_OPT_ARGS];
        int ret = -EINVAL;
        int key_cmd;
        int key_format;
        char *p, *keyword;

        keyword = strsep(&datablob, " \t");
        if (!keyword) {
                pr_info("encrypted_key: insufficient parameters specified\n");
                return ret;
        }
        key_cmd = match_token(keyword, key_tokens, args);

        /* Get optional format: default | ecryptfs */
        p = strsep(&datablob, " \t");
        if (!p) {
                pr_err("encrypted_key: insufficient parameters specified\n");
                return ret;
        }

        key_format = match_token(p, key_format_tokens, args);
        switch (key_format) {
        case Opt_ecryptfs:
        case Opt_default:
                *format = p;
                *master_desc = strsep(&datablob, " \t");
                break;
        case Opt_error:
                *master_desc = p;
                break;
        }

        if (!*master_desc) {
                pr_info("encrypted_key: master key parameter is missing\n");
                goto out;
        }

        if (valid_master_desc(*master_desc, NULL) < 0) {
                pr_info("encrypted_key: master key parameter \'%s\' "
                        "is invalid\n", *master_desc);
                goto out;
        }

        if (decrypted_datalen) {
                *decrypted_datalen = strsep(&datablob, " \t");
                if (!*decrypted_datalen) {
                        pr_info("encrypted_key: keylen parameter is missing\n");
                        goto out;
                }
        }

        switch (key_cmd) {
        case Opt_new:
                if (!decrypted_datalen) {
                        pr_info("encrypted_key: keyword \'%s\' not allowed "
                                "when called from .update method\n", keyword);
                        break;
                }
                ret = 0;
                break;
        case Opt_load:
                if (!decrypted_datalen) {
                        pr_info("encrypted_key: keyword \'%s\' not allowed "
                                "when called from .update method\n", keyword);
                        break;
                }
                *hex_encoded_iv = strsep(&datablob, " \t");
                if (!*hex_encoded_iv) {
                        pr_info("encrypted_key: hex blob is missing\n");
                        break;
                }
                ret = 0;
                break;
        case Opt_update:
                if (decrypted_datalen) {
                        pr_info("encrypted_key: keyword \'%s\' not allowed "
                                "when called from .instantiate method\n",
                                keyword);
                        break;
                }
                ret = 0;
                break;
        case Opt_err:
                pr_info("encrypted_key: keyword \'%s\' not recognized\n",
                        keyword);
                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 %s ", epayload->format,
                      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, size_t *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,
                                    size_t *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 *alloc_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, unsigned int keylen,
                     const u8 *buf, unsigned int buflen)
{
        struct sdesc *sdesc;
        int ret;

        sdesc = alloc_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, unsigned int buflen)
{
        struct sdesc *sdesc;
        int ret;

        sdesc = alloc_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, size_t 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,
                               unsigned int key_len, const u8 *iv,
                               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, size_t *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);
                goto out;
        }

        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,
                               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, size_t 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->format + epayload->datablob_len;
        ret = calc_hmac(digest, derived_key, sizeof derived_key,
                        epayload->format, 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 *format, const u8 *master_key,
                                size_t master_keylen)
{
        u8 derived_key[HASH_SIZE];
        u8 digest[HASH_SIZE];
        int ret;
        char *p;
        unsigned short len;

        ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
        if (ret < 0)
                goto out;

        len = epayload->datablob_len;
        if (!format) {
                p = epayload->master_desc;
                len -= strlen(epayload->format) + 1;
        } else
                p = epayload->format;

        ret = calc_hmac(digest, derived_key, sizeof derived_key, p, len);
        if (ret < 0)
                goto out;
        ret = memcmp(digest, epayload->format + epayload->datablob_len,
                     sizeof digest);
        if (ret) {
                ret = -EINVAL;
                dump_hmac("datablob",
                          epayload->format + 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,
                               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,
                   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 *format,
                                                         const char *master_desc,
                                                         const char *datalen)
{
        struct encrypted_key_payload *epayload = NULL;
        unsigned short datablob_len;
        unsigned short decrypted_datalen;
        unsigned short payload_datalen;
        unsigned int encrypted_datalen;
        unsigned int format_len;
        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);

        format_len = (!format) ? strlen(key_format_default) : strlen(format);
        decrypted_datalen = dlen;
        payload_datalen = decrypted_datalen;
        if (format && !strcmp(format, key_format_ecryptfs)) {
                if (dlen != ECRYPTFS_MAX_KEY_BYTES) {
                        pr_err("encrypted_key: keylen for the ecryptfs format "
                               "must be equal to %d bytes\n",
                               ECRYPTFS_MAX_KEY_BYTES);
                        return ERR_PTR(-EINVAL);
                }
                decrypted_datalen = ECRYPTFS_MAX_KEY_BYTES;
                payload_datalen = sizeof(struct ecryptfs_auth_tok);
        }

        encrypted_datalen = roundup(decrypted_datalen, blksize);

        datablob_len = format_len + 1 + strlen(master_desc) + 1
            + strlen(datalen) + 1 + ivsize + 1 + encrypted_datalen;

        ret = key_payload_reserve(key, payload_datalen + datablob_len
                                  + HASH_SIZE + 1);
        if (ret < 0)
                return ERR_PTR(ret);

        epayload = kzalloc(sizeof(*epayload) + payload_datalen +
                           datablob_len + HASH_SIZE + 1, GFP_KERNEL);
        if (!epayload)
                return ERR_PTR(-ENOMEM);

        epayload->payload_datalen = payload_datalen;
        epayload->decrypted_datalen = decrypted_datalen;
        epayload->datablob_len = datablob_len;
        return epayload;
}

static int encrypted_key_decrypt(struct encrypted_key_payload *epayload,
                                 const char *format, const char *hex_encoded_iv)
{
        struct key *mkey;
        u8 derived_key[HASH_SIZE];
        u8 *master_key;
        u8 *hmac;
        const char *hex_encoded_data;
        unsigned int encrypted_datalen;
        size_t master_keylen;
        size_t asciilen;
        int ret;

        encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
        asciilen = (ivsize + 1 + encrypted_datalen + HASH_SIZE) * 2;
        if (strlen(hex_encoded_iv) != asciilen)
                return -EINVAL;

        hex_encoded_data = hex_encoded_iv + (2 * ivsize) + 2;
        hex2bin(epayload->iv, hex_encoded_iv, ivsize);
        hex2bin(epayload->encrypted_data, hex_encoded_data, encrypted_datalen);

        hmac = epayload->format + 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, format, 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 *format, const char *master_desc,
                        const char *datalen)
{
        unsigned int format_len;

        format_len = (!format) ? strlen(key_format_default) : strlen(format);
        epayload->format = epayload->payload_data + epayload->payload_datalen;
        epayload->master_desc = epayload->format + format_len + 1;
        epayload->datalen = epayload->master_desc + strlen(master_desc) + 1;
        epayload->iv = epayload->datalen + strlen(datalen) + 1;
        epayload->encrypted_data = epayload->iv + ivsize + 1;
        epayload->decrypted_data = epayload->payload_data;

        if (!format)
                memcpy(epayload->format, key_format_default, format_len);
        else {
                if (!strcmp(format, key_format_ecryptfs))
                        epayload->decrypted_data =
                                ecryptfs_get_auth_tok_key((struct ecryptfs_auth_tok *)epayload->payload_data);

                memcpy(epayload->format, format, format_len);
        }

        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 *key_desc, const char *format,
                          const char *master_desc, const char *datalen,
                          const char *hex_encoded_iv)
{
        int ret = 0;

        if (format && !strcmp(format, key_format_ecryptfs)) {
                ret = valid_ecryptfs_desc(key_desc);
                if (ret < 0)
                        return ret;

                ecryptfs_fill_auth_tok((struct ecryptfs_auth_tok *)epayload->payload_data,
                                       key_desc);
        }

        __ekey_init(epayload, format, master_desc, datalen);
        if (!hex_encoded_iv) {
                get_random_bytes(epayload->iv, ivsize);

                get_random_bytes(epayload->decrypted_data,
                                 epayload->decrypted_datalen);
        } else
                ret = encrypted_key_decrypt(epayload, format, hex_encoded_iv);
        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;
        const char *format = NULL;
        char *master_desc = NULL;
        char *decrypted_datalen = NULL;
        char *hex_encoded_iv = 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, &format, &master_desc,
                             &decrypted_datalen, &hex_encoded_iv);
        if (ret < 0)
                goto out;

        epayload = encrypted_key_alloc(key, format, master_desc,
                                       decrypted_datalen);
        if (IS_ERR(epayload)) {
                ret = PTR_ERR(epayload);
                goto out;
        }
        ret = encrypted_init(epayload, key->description, format, master_desc,
                             decrypted_datalen, hex_encoded_iv);
        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;
        const char *format = 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, &format, &new_master_desc, 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, epayload->format,
                                           new_master_desc, epayload->datalen);
        if (IS_ERR(new_epayload)) {
                ret = PTR_ERR(new_epayload);
                goto out;
        }

        __ekey_init(new_epayload, epayload->format, new_master_desc,
                    epayload->datalen);

        memcpy(new_epayload->iv, epayload->iv, ivsize);
        memcpy(new_epayload->payload_data, epayload->payload_data,
               epayload->payload_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;
        size_t master_keylen;
        char derived_key[HASH_SIZE];
        char *ascii_buf;
        size_t asciiblob_len;
        int ret;

        epayload = rcu_dereference_key(key);

        /* 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");