// SPDX-License-Identifier: GPL-2.0
/*
 * ECDSA P1363 signature encoding
 *
 * Copyright (c) 2024 Intel Corporation
 */

#include <linux/err.h>
#include <linux/module.h>
#include <crypto/algapi.h>
#include <crypto/sig.h>
#include <crypto/internal/ecc.h>
#include <crypto/internal/sig.h>

struct ecdsa_p1363_ctx {
        struct crypto_sig *child;
};

static int ecdsa_p1363_verify(struct crypto_sig *tfm,
                              const void *src, unsigned int slen,
                              const void *digest, unsigned int dlen)
{
        struct ecdsa_p1363_ctx *ctx = crypto_sig_ctx(tfm);
        unsigned int keylen = DIV_ROUND_UP_POW2(crypto_sig_keysize(ctx->child),
                                                BITS_PER_BYTE);
        unsigned int ndigits = DIV_ROUND_UP_POW2(keylen, sizeof(u64));
        struct ecdsa_raw_sig sig;

        if (slen != 2 * keylen)
                return -EINVAL;

        ecc_digits_from_bytes(src, keylen, sig.r, ndigits);
        ecc_digits_from_bytes(src + keylen, keylen, sig.s, ndigits);

        return crypto_sig_verify(ctx->child, &sig, sizeof(sig), digest, dlen);
}

static unsigned int ecdsa_p1363_key_size(struct crypto_sig *tfm)
{
        struct ecdsa_p1363_ctx *ctx = crypto_sig_ctx(tfm);

        return crypto_sig_keysize(ctx->child);
}

static unsigned int ecdsa_p1363_max_size(struct crypto_sig *tfm)
{
        struct ecdsa_p1363_ctx *ctx = crypto_sig_ctx(tfm);

        return 2 * DIV_ROUND_UP_POW2(crypto_sig_keysize(ctx->child),
                                     BITS_PER_BYTE);
}

static unsigned int ecdsa_p1363_digest_size(struct crypto_sig *tfm)
{
        struct ecdsa_p1363_ctx *ctx = crypto_sig_ctx(tfm);

        return crypto_sig_digestsize(ctx->child);
}

static int ecdsa_p1363_set_pub_key(struct crypto_sig *tfm,
                                   const void *key, unsigned int keylen)
{
        struct ecdsa_p1363_ctx *ctx = crypto_sig_ctx(tfm);

        return crypto_sig_set_pubkey(ctx->child, key, keylen);
}

static int ecdsa_p1363_init_tfm(struct crypto_sig *tfm)
{
        struct sig_instance *inst = sig_alg_instance(tfm);
        struct crypto_sig_spawn *spawn = sig_instance_ctx(inst);
        struct ecdsa_p1363_ctx *ctx = crypto_sig_ctx(tfm);
        struct crypto_sig *child_tfm;

        child_tfm = crypto_spawn_sig(spawn);
        if (IS_ERR(child_tfm))
                return PTR_ERR(child_tfm);

        ctx->child = child_tfm;

        return 0;
}

static void ecdsa_p1363_exit_tfm(struct crypto_sig *tfm)
{
        struct ecdsa_p1363_ctx *ctx = crypto_sig_ctx(tfm);

        crypto_free_sig(ctx->child);
}

static void ecdsa_p1363_free(struct sig_instance *inst)
{
        struct crypto_sig_spawn *spawn = sig_instance_ctx(inst);

        crypto_drop_sig(spawn);
        kfree(inst);
}

static int ecdsa_p1363_create(struct crypto_template *tmpl, struct rtattr **tb)
{
        struct crypto_sig_spawn *spawn;
        struct sig_instance *inst;
        struct sig_alg *ecdsa_alg;
        u32 mask;
        int err;

        err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SIG, &mask);
        if (err)
                return err;

        inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
        if (!inst)
                return -ENOMEM;

        spawn = sig_instance_ctx(inst);

        err = crypto_grab_sig(spawn, sig_crypto_instance(inst),
                              crypto_attr_alg_name(tb[1]), 0, mask);
        if (err)
                goto err_free_inst;

        ecdsa_alg = crypto_spawn_sig_alg(spawn);

        err = -EINVAL;
        if (strncmp(ecdsa_alg->base.cra_name, "ecdsa", 5) != 0)
                goto err_free_inst;

        err = crypto_inst_setname(sig_crypto_instance(inst), tmpl->name,
                                  &ecdsa_alg->base);
        if (err)
                goto err_free_inst;

        inst->alg.base.cra_priority = ecdsa_alg->base.cra_priority;
        inst->alg.base.cra_ctxsize = sizeof(struct ecdsa_p1363_ctx);

        inst->alg.init = ecdsa_p1363_init_tfm;
        inst->alg.exit = ecdsa_p1363_exit_tfm;

        inst->alg.verify = ecdsa_p1363_verify;
        inst->alg.key_size = ecdsa_p1363_key_size;
        inst->alg.max_size = ecdsa_p1363_max_size;
        inst->alg.digest_size = ecdsa_p1363_digest_size;
        inst->alg.set_pub_key = ecdsa_p1363_set_pub_key;

        inst->free = ecdsa_p1363_free;

        err = sig_register_instance(tmpl, inst);
        if (err) {
err_free_inst:
                ecdsa_p1363_free(inst);
        }
        return err;
}

struct crypto_template ecdsa_p1363_tmpl = {
        .name = "p1363",
        .create = ecdsa_p1363_create,
        .module = THIS_MODULE,
};

MODULE_ALIAS_CRYPTO("p1363");