// SPDX-License-Identifier: GPL-2.0
#define pr_fmt(fmt) "ASYM-TPM: "fmt
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/seq_file.h>
#include <linux/scatterlist.h>
#include <linux/tpm.h>
#include <linux/tpm_command.h>
#include <crypto/akcipher.h>
#include <crypto/hash.h>
#include <crypto/sha1.h>
#include <asm/unaligned.h>
#include <keys/asymmetric-subtype.h>
#include <keys/trusted_tpm.h>
#include <crypto/asym_tpm_subtype.h>
#include <crypto/public_key.h>

#define TPM_ORD_FLUSHSPECIFIC   186
#define TPM_ORD_LOADKEY2        65
#define TPM_ORD_UNBIND          30
#define TPM_ORD_SIGN            60

#define TPM_RT_KEY                      0x00000001

/*
 * Load a TPM key from the blob provided by userspace
 */
static int tpm_loadkey2(struct tpm_buf *tb,
                        uint32_t keyhandle, unsigned char *keyauth,
                        const unsigned char *keyblob, int keybloblen,
                        uint32_t *newhandle)
{
        unsigned char nonceodd[TPM_NONCE_SIZE];
        unsigned char enonce[TPM_NONCE_SIZE];
        unsigned char authdata[SHA1_DIGEST_SIZE];
        uint32_t authhandle = 0;
        unsigned char cont = 0;
        uint32_t ordinal;
        int ret;

        ordinal = htonl(TPM_ORD_LOADKEY2);

        /* session for loading the key */
        ret = oiap(tb, &authhandle, enonce);
        if (ret < 0) {
                pr_info("oiap failed (%d)\n", ret);
                return ret;
        }

        /* generate odd nonce */
        ret = tpm_get_random(NULL, nonceodd, TPM_NONCE_SIZE);
        if (ret < 0) {
                pr_info("tpm_get_random failed (%d)\n", ret);
                return ret;
        }

        /* calculate authorization HMAC value */
        ret = TSS_authhmac(authdata, keyauth, SHA1_DIGEST_SIZE, enonce,
                           nonceodd, cont, sizeof(uint32_t), &ordinal,
                           keybloblen, keyblob, 0, 0);
        if (ret < 0)
                return ret;

        /* build the request buffer */
        tpm_buf_reset(tb, TPM_TAG_RQU_AUTH1_COMMAND, TPM_ORD_LOADKEY2);
        tpm_buf_append_u32(tb, keyhandle);
        tpm_buf_append(tb, keyblob, keybloblen);
        tpm_buf_append_u32(tb, authhandle);
        tpm_buf_append(tb, nonceodd, TPM_NONCE_SIZE);
        tpm_buf_append_u8(tb, cont);
        tpm_buf_append(tb, authdata, SHA1_DIGEST_SIZE);

        ret = trusted_tpm_send(tb->data, MAX_BUF_SIZE);
        if (ret < 0) {
                pr_info("authhmac failed (%d)\n", ret);
                return ret;
        }

        ret = TSS_checkhmac1(tb->data, ordinal, nonceodd, keyauth,
                             SHA1_DIGEST_SIZE, 0, 0);
        if (ret < 0) {
                pr_info("TSS_checkhmac1 failed (%d)\n", ret);
                return ret;
        }

        *newhandle = LOAD32(tb->data, TPM_DATA_OFFSET);
        return 0;
}

/*
 * Execute the FlushSpecific TPM command
 */
static int tpm_flushspecific(struct tpm_buf *tb, uint32_t handle)
{
        tpm_buf_reset(tb, TPM_TAG_RQU_COMMAND, TPM_ORD_FLUSHSPECIFIC);
        tpm_buf_append_u32(tb, handle);
        tpm_buf_append_u32(tb, TPM_RT_KEY);

        return trusted_tpm_send(tb->data, MAX_BUF_SIZE);
}

/*
 * Decrypt a blob provided by userspace using a specific key handle.
 * The handle is a well known handle or previously loaded by e.g. LoadKey2
 */
static int tpm_unbind(struct tpm_buf *tb,
                        uint32_t keyhandle, unsigned char *keyauth,
                        const unsigned char *blob, uint32_t bloblen,
                        void *out, uint32_t outlen)
{
        unsigned char nonceodd[TPM_NONCE_SIZE];
        unsigned char enonce[TPM_NONCE_SIZE];
        unsigned char authdata[SHA1_DIGEST_SIZE];
        uint32_t authhandle = 0;
        unsigned char cont = 0;
        uint32_t ordinal;
        uint32_t datalen;
        int ret;

        ordinal = htonl(TPM_ORD_UNBIND);
        datalen = htonl(bloblen);

        /* session for loading the key */
        ret = oiap(tb, &authhandle, enonce);
        if (ret < 0) {
                pr_info("oiap failed (%d)\n", ret);
                return ret;
        }

        /* generate odd nonce */
        ret = tpm_get_random(NULL, nonceodd, TPM_NONCE_SIZE);
        if (ret < 0) {
                pr_info("tpm_get_random failed (%d)\n", ret);
                return ret;
        }

        /* calculate authorization HMAC value */
        ret = TSS_authhmac(authdata, keyauth, SHA1_DIGEST_SIZE, enonce,
                           nonceodd, cont, sizeof(uint32_t), &ordinal,
                           sizeof(uint32_t), &datalen,
                           bloblen, blob, 0, 0);
        if (ret < 0)
                return ret;

        /* build the request buffer */
        tpm_buf_reset(tb, TPM_TAG_RQU_AUTH1_COMMAND, TPM_ORD_UNBIND);
        tpm_buf_append_u32(tb, keyhandle);
        tpm_buf_append_u32(tb, bloblen);
        tpm_buf_append(tb, blob, bloblen);
        tpm_buf_append_u32(tb, authhandle);
        tpm_buf_append(tb, nonceodd, TPM_NONCE_SIZE);
        tpm_buf_append_u8(tb, cont);
        tpm_buf_append(tb, authdata, SHA1_DIGEST_SIZE);

        ret = trusted_tpm_send(tb->data, MAX_BUF_SIZE);
        if (ret < 0) {
                pr_info("authhmac failed (%d)\n", ret);
                return ret;
        }

        datalen = LOAD32(tb->data, TPM_DATA_OFFSET);

        ret = TSS_checkhmac1(tb->data, ordinal, nonceodd,
                             keyauth, SHA1_DIGEST_SIZE,
                             sizeof(uint32_t), TPM_DATA_OFFSET,
                             datalen, TPM_DATA_OFFSET + sizeof(uint32_t),
                             0, 0);
        if (ret < 0) {
                pr_info("TSS_checkhmac1 failed (%d)\n", ret);
                return ret;
        }

        memcpy(out, tb->data + TPM_DATA_OFFSET + sizeof(uint32_t),
               min(outlen, datalen));

        return datalen;
}

/*
 * Sign a blob provided by userspace (that has had the hash function applied)
 * using a specific key handle.  The handle is assumed to have been previously
 * loaded by e.g. LoadKey2.
 *
 * Note that the key signature scheme of the used key should be set to
 * TPM_SS_RSASSAPKCS1v15_DER.  This allows the hashed input to be of any size
 * up to key_length_in_bytes - 11 and not be limited to size 20 like the
 * TPM_SS_RSASSAPKCS1v15_SHA1 signature scheme.
 */
static int tpm_sign(struct tpm_buf *tb,
                    uint32_t keyhandle, unsigned char *keyauth,
                    const unsigned char *blob, uint32_t bloblen,
                    void *out, uint32_t outlen)
{
        unsigned char nonceodd[TPM_NONCE_SIZE];
        unsigned char enonce[TPM_NONCE_SIZE];
        unsigned char authdata[SHA1_DIGEST_SIZE];
        uint32_t authhandle = 0;
        unsigned char cont = 0;
        uint32_t ordinal;
        uint32_t datalen;
        int ret;

        ordinal = htonl(TPM_ORD_SIGN);
        datalen = htonl(bloblen);

        /* session for loading the key */
        ret = oiap(tb, &authhandle, enonce);
        if (ret < 0) {
                pr_info("oiap failed (%d)\n", ret);
                return ret;
        }

        /* generate odd nonce */
        ret = tpm_get_random(NULL, nonceodd, TPM_NONCE_SIZE);
        if (ret < 0) {
                pr_info("tpm_get_random failed (%d)\n", ret);
                return ret;
        }

        /* calculate authorization HMAC value */
        ret = TSS_authhmac(authdata, keyauth, SHA1_DIGEST_SIZE, enonce,
                           nonceodd, cont, sizeof(uint32_t), &ordinal,
                           sizeof(uint32_t), &datalen,
                           bloblen, blob, 0, 0);
        if (ret < 0)
                return ret;

        /* build the request buffer */
        tpm_buf_reset(tb, TPM_TAG_RQU_AUTH1_COMMAND, TPM_ORD_SIGN);
        tpm_buf_append_u32(tb, keyhandle);
        tpm_buf_append_u32(tb, bloblen);
        tpm_buf_append(tb, blob, bloblen);
        tpm_buf_append_u32(tb, authhandle);
        tpm_buf_append(tb, nonceodd, TPM_NONCE_SIZE);
        tpm_buf_append_u8(tb, cont);
        tpm_buf_append(tb, authdata, SHA1_DIGEST_SIZE);

        ret = trusted_tpm_send(tb->data, MAX_BUF_SIZE);
        if (ret < 0) {
                pr_info("authhmac failed (%d)\n", ret);
                return ret;
        }

        datalen = LOAD32(tb->data, TPM_DATA_OFFSET);

        ret = TSS_checkhmac1(tb->data, ordinal, nonceodd,
                             keyauth, SHA1_DIGEST_SIZE,
                             sizeof(uint32_t), TPM_DATA_OFFSET,
                             datalen, TPM_DATA_OFFSET + sizeof(uint32_t),
                             0, 0);
        if (ret < 0) {
                pr_info("TSS_checkhmac1 failed (%d)\n", ret);
                return ret;
        }

        memcpy(out, tb->data + TPM_DATA_OFFSET + sizeof(uint32_t),
               min(datalen, outlen));

        return datalen;
}

/* Room to fit two u32 zeros for algo id and parameters length. */
#define SETKEY_PARAMS_SIZE (sizeof(u32) * 2)

/*
 * Maximum buffer size for the BER/DER encoded public key.  The public key
 * is of the form SEQUENCE { INTEGER n, INTEGER e } where n is a maximum 2048
 * bit key and e is usually 65537
 * The encoding overhead is:
 * - max 4 bytes for SEQUENCE
 *   - max 4 bytes for INTEGER n type/length
 *     - 257 bytes of n
 *   - max 2 bytes for INTEGER e type/length
 *     - 3 bytes of e
 * - 4+4 of zeros for set_pub_key parameters (SETKEY_PARAMS_SIZE)
 */
#define PUB_KEY_BUF_SIZE (4 + 4 + 257 + 2 + 3 + SETKEY_PARAMS_SIZE)

/*
 * Provide a part of a description of the key for /proc/keys.
 */
static void asym_tpm_describe(const struct key *asymmetric_key,
                              struct seq_file *m)
{
        struct tpm_key *tk = asymmetric_key->payload.data[asym_crypto];

        if (!tk)
                return;

        seq_printf(m, "TPM1.2/Blob");
}

static void asym_tpm_destroy(void *payload0, void *payload3)
{
        struct tpm_key *tk = payload0;

        if (!tk)
                return;

        kfree(tk->blob);
        tk->blob_len = 0;

        kfree(tk);
}

/* How many bytes will it take to encode the length */
static inline uint32_t definite_length(uint32_t len)
{
        if (len <= 127)
                return 1;
        if (len <= 255)
                return 2;
        return 3;
}

static inline uint8_t *encode_tag_length(uint8_t *buf, uint8_t tag,
                                         uint32_t len)
{
        *buf++ = tag;

        if (len <= 127) {
                buf[0] = len;
                return buf + 1;
        }

        if (len <= 255) {
                buf[0] = 0x81;
                buf[1] = len;
                return buf + 2;
        }

        buf[0] = 0x82;
        put_unaligned_be16(len, buf + 1);
        return buf + 3;
}

static uint32_t derive_pub_key(const void *pub_key, uint32_t len, uint8_t *buf)
{
        uint8_t *cur = buf;
        uint32_t n_len = definite_length(len) + 1 + len + 1;
        uint32_t e_len = definite_length(3) + 1 + 3;
        uint8_t e[3] = { 0x01, 0x00, 0x01 };

        /* SEQUENCE */
        cur = encode_tag_length(cur, 0x30, n_len + e_len);
        /* INTEGER n */
        cur = encode_tag_length(cur, 0x02, len + 1);
        cur[0] = 0x00;
        memcpy(cur + 1, pub_key, len);
        cur += len + 1;
        cur = encode_tag_length(cur, 0x02, sizeof(e));
        memcpy(cur, e, sizeof(e));
        cur += sizeof(e);
        /* Zero parameters to satisfy set_pub_key ABI. */
        memzero_explicit(cur, SETKEY_PARAMS_SIZE);

        return cur - buf;
}

/*
 * Determine the crypto algorithm name.
 */
static int determine_akcipher(const char *encoding, const char *hash_algo,
                              char alg_name[CRYPTO_MAX_ALG_NAME])
{
        if (strcmp(encoding, "pkcs1") == 0) {
                if (!hash_algo) {
                        strcpy(alg_name, "pkcs1pad(rsa)");
                        return 0;
                }

                if (snprintf(alg_name, CRYPTO_MAX_ALG_NAME, "pkcs1pad(rsa,%s)",
                             hash_algo) >= CRYPTO_MAX_ALG_NAME)
                        return -EINVAL;

                return 0;
        }

        if (strcmp(encoding, "raw") == 0) {
                strcpy(alg_name, "rsa");
                return 0;
        }

        return -ENOPKG;
}

/*
 * Query information about a key.
 */
static int tpm_key_query(const struct kernel_pkey_params *params,
                         struct kernel_pkey_query *info)
{
        struct tpm_key *tk = params->key->payload.data[asym_crypto];
        int ret;
        char alg_name[CRYPTO_MAX_ALG_NAME];
        struct crypto_akcipher *tfm;
        uint8_t der_pub_key[PUB_KEY_BUF_SIZE];
        uint32_t der_pub_key_len;
        int len;

        /* TPM only works on private keys, public keys still done in software */
        ret = determine_akcipher(params->encoding, params->hash_algo, alg_name);
        if (ret < 0)
                return ret;

        tfm = crypto_alloc_akcipher(alg_name, 0, 0);
        if (IS_ERR(tfm))
                return PTR_ERR(tfm);

        der_pub_key_len = derive_pub_key(tk->pub_key, tk->pub_key_len,
                                         der_pub_key);

        ret = crypto_akcipher_set_pub_key(tfm, der_pub_key, der_pub_key_len);
        if (ret < 0)
                goto error_free_tfm;

        len = crypto_akcipher_maxsize(tfm);

        info->key_size = tk->key_len;
        info->max_data_size = tk->key_len / 8;
        info->max_sig_size = len;
        info->max_enc_size = len;
        info->max_dec_size = tk->key_len / 8;

        info->supported_ops = KEYCTL_SUPPORTS_ENCRYPT |
                              KEYCTL_SUPPORTS_DECRYPT |
                              KEYCTL_SUPPORTS_VERIFY |
                              KEYCTL_SUPPORTS_SIGN;

        ret = 0;
error_free_tfm:
        crypto_free_akcipher(tfm);
        pr_devel("<==%s() = %d\n", __func__, ret);
        return ret;
}

/*
 * Encryption operation is performed with the public key.  Hence it is done
 * in software
 */
static int tpm_key_encrypt(struct tpm_key *tk,
                           struct kernel_pkey_params *params,
                           const void *in, void *out)
{
        char alg_name[CRYPTO_MAX_ALG_NAME];
        struct crypto_akcipher *tfm;
        struct akcipher_request *req;
        struct crypto_wait cwait;
        struct scatterlist in_sg, out_sg;
        uint8_t der_pub_key[PUB_KEY_BUF_SIZE];
        uint32_t der_pub_key_len;
        int ret;

        pr_devel("==>%s()\n", __func__);

        ret = determine_akcipher(params->encoding, params->hash_algo, alg_name);
        if (ret < 0)
                return ret;

        tfm = crypto_alloc_akcipher(alg_name, 0, 0);
        if (IS_ERR(tfm))
                return PTR_ERR(tfm);

        der_pub_key_len = derive_pub_key(tk->pub_key, tk->pub_key_len,
                                         der_pub_key);

        ret = crypto_akcipher_set_pub_key(tfm, der_pub_key, der_pub_key_len);
        if (ret < 0)
                goto error_free_tfm;

        ret = -ENOMEM;
        req = akcipher_request_alloc(tfm, GFP_KERNEL);
        if (!req)
                goto error_free_tfm;

        sg_init_one(&in_sg, in, params->in_len);
        sg_init_one(&out_sg, out, params->out_len);
        akcipher_request_set_crypt(req, &in_sg, &out_sg, params->in_len,
                                   params->out_len);
        crypto_init_wait(&cwait);
        akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
                                      CRYPTO_TFM_REQ_MAY_SLEEP,
                                      crypto_req_done, &cwait);

        ret = crypto_akcipher_encrypt(req);
        ret = crypto_wait_req(ret, &cwait);

        if (ret == 0)
                ret = req->dst_len;

        akcipher_request_free(req);
error_free_tfm:
        crypto_free_akcipher(tfm);
        pr_devel("<==%s() = %d\n", __func__, ret);
        return ret;
}

/*
 * Decryption operation is performed with the private key in the TPM.
 */
static int tpm_key_decrypt(struct tpm_key *tk,
                           struct kernel_pkey_params *params,
                           const void *in, void *out)
{
        struct tpm_buf tb;
        uint32_t keyhandle;
        uint8_t srkauth[SHA1_DIGEST_SIZE];
        uint8_t keyauth[SHA1_DIGEST_SIZE];
        int r;

        pr_devel("==>%s()\n", __func__);

        if (params->hash_algo)
                return -ENOPKG;

        if (strcmp(params->encoding, "pkcs1"))
                return -ENOPKG;

        r = tpm_buf_init(&tb, 0, 0);
        if (r)
                return r;

        /* TODO: Handle a non-all zero SRK authorization */
        memset(srkauth, 0, sizeof(srkauth));

        r = tpm_loadkey2(&tb, SRKHANDLE, srkauth,
                                tk->blob, tk->blob_len, &keyhandle);
        if (r < 0) {
                pr_devel("loadkey2 failed (%d)\n", r);
                goto error;
        }

        /* TODO: Handle a non-all zero key authorization */
        memset(keyauth, 0, sizeof(keyauth));

        r = tpm_unbind(&tb, keyhandle, keyauth,
                       in, params->in_len, out, params->out_len);
        if (r < 0)
                pr_devel("tpm_unbind failed (%d)\n", r);

        if (tpm_flushspecific(&tb, keyhandle) < 0)
                pr_devel("flushspecific failed (%d)\n", r);

error:
        tpm_buf_destroy(&tb);
        pr_devel("<==%s() = %d\n", __func__, r);
        return r;
}

/*
 * Hash algorithm OIDs plus ASN.1 DER wrappings [RFC4880 sec 5.2.2].
 */
static const u8 digest_info_md5[] = {
        0x30, 0x20, 0x30, 0x0c, 0x06, 0x08,
        0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x02, 0x05, /* OID */
        0x05, 0x00, 0x04, 0x10
};

static const u8 digest_info_sha1[] = {
        0x30, 0x21, 0x30, 0x09, 0x06, 0x05,
        0x2b, 0x0e, 0x03, 0x02, 0x1a,
        0x05, 0x00, 0x04, 0x14
};

static const u8 digest_info_rmd160[] = {
        0x30, 0x21, 0x30, 0x09, 0x06, 0x05,
        0x2b, 0x24, 0x03, 0x02, 0x01,
        0x05, 0x00, 0x04, 0x14
};

static const u8 digest_info_sha224[] = {
        0x30, 0x2d, 0x30, 0x0d, 0x06, 0x09,
        0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x04,
        0x05, 0x00, 0x04, 0x1c
};

static const u8 digest_info_sha256[] = {
        0x30, 0x31, 0x30, 0x0d, 0x06, 0x09,
        0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01,
        0x05, 0x00, 0x04, 0x20
};

static const u8 digest_info_sha384[] = {
        0x30, 0x41, 0x30, 0x0d, 0x06, 0x09,
        0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x02,
        0x05, 0x00, 0x04, 0x30
};

static const u8 digest_info_sha512[] = {
        0x30, 0x51, 0x30, 0x0d, 0x06, 0x09,
        0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03,
        0x05, 0x00, 0x04, 0x40
};

static const struct asn1_template {
        const char      *name;
        const u8        *data;
        size_t          size;
} asn1_templates[] = {
#define _(X) { #X, digest_info_##X, sizeof(digest_info_##X) }
        _(md5),
        _(sha1),
        _(rmd160),
        _(sha256),
        _(sha384),
        _(sha512),
        _(sha224),
        { NULL }
#undef _
};

static const struct asn1_template *lookup_asn1(const char *name)
{
        const struct asn1_template *p;

        for (p = asn1_templates; p->name; p++)
                if (strcmp(name, p->name) == 0)
                        return p;
        return NULL;
}

/*
 * Sign operation is performed with the private key in the TPM.
 */
static int tpm_key_sign(struct tpm_key *tk,
                        struct kernel_pkey_params *params,
                        const void *in, void *out)
{
        struct tpm_buf tb;
        uint32_t keyhandle;
        uint8_t srkauth[SHA1_DIGEST_SIZE];
        uint8_t keyauth[SHA1_DIGEST_SIZE];
        void *asn1_wrapped = NULL;
        uint32_t in_len = params->in_len;
        int r;

        pr_devel("==>%s()\n", __func__);

        if (strcmp(params->encoding, "pkcs1"))
                return -ENOPKG;

        if (params->hash_algo) {
                const struct asn1_template *asn1 =
                                                lookup_asn1(params->hash_algo);

                if (!asn1)
                        return -ENOPKG;

                /* request enough space for the ASN.1 template + input hash */
                asn1_wrapped = kzalloc(in_len + asn1->size, GFP_KERNEL);
                if (!asn1_wrapped)
                        return -ENOMEM;

                /* Copy ASN.1 template, then the input */
                memcpy(asn1_wrapped, asn1->data, asn1->size);
                memcpy(asn1_wrapped + asn1->size, in, in_len);

                in = asn1_wrapped;
                in_len += asn1->size;
        }

        if (in_len > tk->key_len / 8 - 11) {
                r = -EOVERFLOW;
                goto error_free_asn1_wrapped;
        }

        r = tpm_buf_init(&tb, 0, 0);
        if (r)
                goto error_free_asn1_wrapped;

        /* TODO: Handle a non-all zero SRK authorization */
        memset(srkauth, 0, sizeof(srkauth));

        r = tpm_loadkey2(&tb, SRKHANDLE, srkauth,
                         tk->blob, tk->blob_len, &keyhandle);
        if (r < 0) {
                pr_devel("loadkey2 failed (%d)\n", r);
                goto error_free_tb;
        }

        /* TODO: Handle a non-all zero key authorization */
        memset(keyauth, 0, sizeof(keyauth));

        r = tpm_sign(&tb, keyhandle, keyauth, in, in_len, out, params->out_len);
        if (r < 0)
                pr_devel("tpm_sign failed (%d)\n", r);

        if (tpm_flushspecific(&tb, keyhandle) < 0)
                pr_devel("flushspecific failed (%d)\n", r);

error_free_tb:
        tpm_buf_destroy(&tb);
error_free_asn1_wrapped:
        kfree(asn1_wrapped);
        pr_devel("<==%s() = %d\n", __func__, r);
        return r;
}

/*
 * Do encryption, decryption and signing ops.
 */
static int tpm_key_eds_op(struct kernel_pkey_params *params,
                          const void *in, void *out)
{
        struct tpm_key *tk = params->key->payload.data[asym_crypto];
        int ret = -EOPNOTSUPP;

        /* Perform the encryption calculation. */
        switch (params->op) {
        case kernel_pkey_encrypt:
                ret = tpm_key_encrypt(tk, params, in, out);
                break;
        case kernel_pkey_decrypt:
                ret = tpm_key_decrypt(tk, params, in, out);
                break;
        case kernel_pkey_sign:
                ret = tpm_key_sign(tk, params, in, out);
                break;
        default:
                BUG();
        }

        return ret;
}

/*
 * Verify a signature using a public key.
 */
static int tpm_key_verify_signature(const struct key *key,
                                    const struct public_key_signature *sig)
{
        const struct tpm_key *tk = key->payload.data[asym_crypto];
        struct crypto_wait cwait;
        struct crypto_akcipher *tfm;
        struct akcipher_request *req;
        struct scatterlist src_sg[2];
        char alg_name[CRYPTO_MAX_ALG_NAME];
        uint8_t der_pub_key[PUB_KEY_BUF_SIZE];
        uint32_t der_pub_key_len;
        int ret;

        pr_devel("==>%s()\n", __func__);

        BUG_ON(!tk);
        BUG_ON(!sig);
        BUG_ON(!sig->s);

        if (!sig->digest)
                return -ENOPKG;

        ret = determine_akcipher(sig->encoding, sig->hash_algo, alg_name);
        if (ret < 0)
                return ret;

        tfm = crypto_alloc_akcipher(alg_name, 0, 0);
        if (IS_ERR(tfm))
                return PTR_ERR(tfm);

        der_pub_key_len = derive_pub_key(tk->pub_key, tk->pub_key_len,
                                         der_pub_key);

        ret = crypto_akcipher_set_pub_key(tfm, der_pub_key, der_pub_key_len);
        if (ret < 0)
                goto error_free_tfm;

        ret = -ENOMEM;
        req = akcipher_request_alloc(tfm, GFP_KERNEL);
        if (!req)
                goto error_free_tfm;

        sg_init_table(src_sg, 2);
        sg_set_buf(&src_sg[0], sig->s, sig->s_size);
        sg_set_buf(&src_sg[1], sig->digest, sig->digest_size);
        akcipher_request_set_crypt(req, src_sg, NULL, sig->s_size,
                                   sig->digest_size);
        crypto_init_wait(&cwait);
        akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
                                      CRYPTO_TFM_REQ_MAY_SLEEP,
                                      crypto_req_done, &cwait);
        ret = crypto_wait_req(crypto_akcipher_verify(req), &cwait);

        akcipher_request_free(req);
error_free_tfm:
        crypto_free_akcipher(tfm);
        pr_devel("<==%s() = %d\n", __func__, ret);
        if (WARN_ON_ONCE(ret > 0))
                ret = -EINVAL;
        return ret;
}

/*
 * Parse enough information out of TPM_KEY structure:
 * TPM_STRUCT_VER -> 4 bytes
 * TPM_KEY_USAGE -> 2 bytes
 * TPM_KEY_FLAGS -> 4 bytes
 * TPM_AUTH_DATA_USAGE -> 1 byte
 * TPM_KEY_PARMS -> variable
 * UINT32 PCRInfoSize -> 4 bytes
 * BYTE* -> PCRInfoSize bytes
 * TPM_STORE_PUBKEY
 * UINT32 encDataSize;
 * BYTE* -> encDataSize;
 *
 * TPM_KEY_PARMS:
 * TPM_ALGORITHM_ID -> 4 bytes
 * TPM_ENC_SCHEME -> 2 bytes
 * TPM_SIG_SCHEME -> 2 bytes
 * UINT32 parmSize -> 4 bytes
 * BYTE* -> variable
 */
static int extract_key_parameters(struct tpm_key *tk)
{
        const void *cur = tk->blob;
        uint32_t len = tk->blob_len;
        const void *pub_key;
        uint32_t sz;
        uint32_t key_len;

        if (len < 11)
                return -EBADMSG;

        /* Ensure this is a legacy key */
        if (get_unaligned_be16(cur + 4) != 0x0015)
                return -EBADMSG;

        /* Skip to TPM_KEY_PARMS */
        cur += 11;
        len -= 11;

        if (len < 12)
                return -EBADMSG;

        /* Make sure this is an RSA key */
        if (get_unaligned_be32(cur) != 0x00000001)
                return -EBADMSG;

        /* Make sure this is TPM_ES_RSAESPKCSv15 encoding scheme */
        if (get_unaligned_be16(cur + 4) != 0x0002)
                return -EBADMSG;

        /* Make sure this is TPM_SS_RSASSAPKCS1v15_DER signature scheme */
        if (get_unaligned_be16(cur + 6) != 0x0003)
                return -EBADMSG;

        sz = get_unaligned_be32(cur + 8);
        if (len < sz + 12)
                return -EBADMSG;

        /* Move to TPM_RSA_KEY_PARMS */
        len -= 12;
        cur += 12;

        /* Grab the RSA key length */
        key_len = get_unaligned_be32(cur);

        switch (key_len) {
        case 512:
        case 1024:
        case 1536:
        case 2048:
                break;
        default:
                return -EINVAL;
        }

        /* Move just past TPM_KEY_PARMS */
        cur += sz;
        len -= sz;

        if (len < 4)
                return -EBADMSG;

        sz = get_unaligned_be32(cur);
        if (len < 4 + sz)
                return -EBADMSG;

        /* Move to TPM_STORE_PUBKEY */
        cur += 4 + sz;
        len -= 4 + sz;

        /* Grab the size of the public key, it should jive with the key size */
        sz = get_unaligned_be32(cur);
        if (sz > 256)
                return -EINVAL;

        pub_key = cur + 4;

        tk->key_len = key_len;
        tk->pub_key = pub_key;
        tk->pub_key_len = sz;

        return 0;
}

/* Given the blob, parse it and load it into the TPM */
struct tpm_key *tpm_key_create(const void *blob, uint32_t blob_len)
{
        int r;
        struct tpm_key *tk;

        r = tpm_is_tpm2(NULL);
        if (r < 0)
                goto error;

        /* We don't support TPM2 yet */
        if (r > 0) {
                r = -ENODEV;
                goto error;
        }

        r = -ENOMEM;
        tk = kzalloc(sizeof(struct tpm_key), GFP_KERNEL);
        if (!tk)
                goto error;

        tk->blob = kmemdup(blob, blob_len, GFP_KERNEL);
        if (!tk->blob)
                goto error_memdup;

        tk->blob_len = blob_len;

        r = extract_key_parameters(tk);
        if (r < 0)
                goto error_extract;

        return tk;

error_extract:
        kfree(tk->blob);
        tk->blob_len = 0;
error_memdup:
        kfree(tk);
error:
        return ERR_PTR(r);
}
EXPORT_SYMBOL_GPL(tpm_key_create);

/*
 * TPM-based asymmetric key subtype
 */
struct asymmetric_key_subtype asym_tpm_subtype = {
        .owner                  = THIS_MODULE,
        .name                   = "asym_tpm",
        .name_len               = sizeof("asym_tpm") - 1,
        .describe               = asym_tpm_describe,
        .destroy                = asym_tpm_destroy,
        .query                  = tpm_key_query,
        .eds_op                 = tpm_key_eds_op,
        .verify_signature       = tpm_key_verify_signature,
};
EXPORT_SYMBOL_GPL(asym_tpm_subtype);

MODULE_DESCRIPTION("TPM based asymmetric key subtype");
MODULE_AUTHOR("Intel Corporation");
MODULE_LICENSE("GPL v2");