/*
 * RSA padding templates.
 *
 * Copyright (c) 2015  Intel Corporation
 *
 * 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; either version 2 of the License, or (at your option)
 * any later version.
 */

#include <crypto/algapi.h>
#include <crypto/akcipher.h>
#include <crypto/internal/akcipher.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/random.h>

/*
 * Hash algorithm OIDs plus ASN.1 DER wrappings [RFC4880 sec 5.2.2].
 */
static const u8 rsa_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 rsa_digest_info_sha1[] = {
        0x30, 0x21, 0x30, 0x09, 0x06, 0x05,
        0x2b, 0x0e, 0x03, 0x02, 0x1a,
        0x05, 0x00, 0x04, 0x14
};

static const u8 rsa_digest_info_rmd160[] = {
        0x30, 0x21, 0x30, 0x09, 0x06, 0x05,
        0x2b, 0x24, 0x03, 0x02, 0x01,
        0x05, 0x00, 0x04, 0x14
};

static const u8 rsa_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 rsa_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 rsa_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 rsa_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 rsa_asn1_template {
        const char      *name;
        const u8        *data;
        size_t          size;
} rsa_asn1_templates[] = {
#define _(X) { #X, rsa_digest_info_##X, sizeof(rsa_digest_info_##X) }
        _(md5),
        _(sha1),
        _(rmd160),
        _(sha256),
        _(sha384),
        _(sha512),
        _(sha224),
        { NULL }
#undef _
};

static const struct rsa_asn1_template *rsa_lookup_asn1(const char *name)
{
        const struct rsa_asn1_template *p;

        for (p = rsa_asn1_templates; p->name; p++)
                if (strcmp(name, p->name) == 0)
                        return p;
        return NULL;
}

struct pkcs1pad_ctx {
        struct crypto_akcipher *child;
        unsigned int key_size;
};

struct pkcs1pad_inst_ctx {
        struct crypto_akcipher_spawn spawn;
        const struct rsa_asn1_template *digest_info;
};

struct pkcs1pad_request {
        struct scatterlist in_sg[2], out_sg[1];
        uint8_t *in_buf, *out_buf;
        struct akcipher_request child_req;
};

static int pkcs1pad_set_pub_key(struct crypto_akcipher *tfm, const void *key,
                unsigned int keylen)
{
        struct pkcs1pad_ctx *ctx = akcipher_tfm_ctx(tfm);
        int err;

        ctx->key_size = 0;

        err = crypto_akcipher_set_pub_key(ctx->child, key, keylen);
        if (err)
                return err;

        /* Find out new modulus size from rsa implementation */
        err = crypto_akcipher_maxsize(ctx->child);
        if (err > PAGE_SIZE)
                return -ENOTSUPP;

        ctx->key_size = err;
        return 0;
}

static int pkcs1pad_set_priv_key(struct crypto_akcipher *tfm, const void *key,
                unsigned int keylen)
{
        struct pkcs1pad_ctx *ctx = akcipher_tfm_ctx(tfm);
        int err;

        ctx->key_size = 0;

        err = crypto_akcipher_set_priv_key(ctx->child, key, keylen);
        if (err)
                return err;

        /* Find out new modulus size from rsa implementation */
        err = crypto_akcipher_maxsize(ctx->child);
        if (err > PAGE_SIZE)
                return -ENOTSUPP;

        ctx->key_size = err;
        return 0;
}

static unsigned int pkcs1pad_get_max_size(struct crypto_akcipher *tfm)
{
        struct pkcs1pad_ctx *ctx = akcipher_tfm_ctx(tfm);

        /*
         * The maximum destination buffer size for the encrypt/sign operations
         * will be the same as for RSA, even though it's smaller for
         * decrypt/verify.
         */

        return ctx->key_size;
}

static void pkcs1pad_sg_set_buf(struct scatterlist *sg, void *buf, size_t len,
                struct scatterlist *next)
{
        int nsegs = next ? 2 : 1;

        sg_init_table(sg, nsegs);
        sg_set_buf(sg, buf, len);

        if (next)
                sg_chain(sg, nsegs, next);
}

static int pkcs1pad_encrypt_sign_complete(struct akcipher_request *req, int err)
{
        struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
        struct pkcs1pad_ctx *ctx = akcipher_tfm_ctx(tfm);
        struct pkcs1pad_request *req_ctx = akcipher_request_ctx(req);
        unsigned int pad_len;
        unsigned int len;
        u8 *out_buf;

        if (err)
                goto out;

        len = req_ctx->child_req.dst_len;
        pad_len = ctx->key_size - len;

        /* Four billion to one */
        if (likely(!pad_len))
                goto out;

        out_buf = kzalloc(ctx->key_size, GFP_KERNEL);
        err = -ENOMEM;
        if (!out_buf)
                goto out;

        sg_copy_to_buffer(req->dst, sg_nents_for_len(req->dst, len),
                          out_buf + pad_len, len);
        sg_copy_from_buffer(req->dst,
                            sg_nents_for_len(req->dst, ctx->key_size),
                            out_buf, ctx->key_size);
        kfree_sensitive(out_buf);

out:
        req->dst_len = ctx->key_size;

        kfree(req_ctx->in_buf);

        return err;
}

static void pkcs1pad_encrypt_sign_complete_cb(
                struct crypto_async_request *child_async_req, int err)
{
        struct akcipher_request *req = child_async_req->data;
        struct crypto_async_request async_req;

        if (err == -EINPROGRESS)
                return;

        async_req.data = req->base.data;
        async_req.tfm = crypto_akcipher_tfm(crypto_akcipher_reqtfm(req));
        async_req.flags = child_async_req->flags;
        req->base.complete(&async_req,
                        pkcs1pad_encrypt_sign_complete(req, err));
}

static int pkcs1pad_encrypt(struct akcipher_request *req)
{
        struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
        struct pkcs1pad_ctx *ctx = akcipher_tfm_ctx(tfm);
        struct pkcs1pad_request *req_ctx = akcipher_request_ctx(req);
        int err;
        unsigned int i, ps_end;

        if (!ctx->key_size)
                return -EINVAL;

        if (req->src_len > ctx->key_size - 11)
                return -EOVERFLOW;

        if (req->dst_len < ctx->key_size) {
                req->dst_len = ctx->key_size;
                return -EOVERFLOW;
        }

        req_ctx->in_buf = kmalloc(ctx->key_size - 1 - req->src_len,
                                  GFP_KERNEL);
        if (!req_ctx->in_buf)
                return -ENOMEM;

        ps_end = ctx->key_size - req->src_len - 2;
        req_ctx->in_buf[0] = 0x02;
        for (i = 1; i < ps_end; i++)
                req_ctx->in_buf[i] = 1 + prandom_u32_max(255);
        req_ctx->in_buf[ps_end] = 0x00;

        pkcs1pad_sg_set_buf(req_ctx->in_sg, req_ctx->in_buf,
                        ctx->key_size - 1 - req->src_len, req->src);

        req_ctx->out_buf = kmalloc(ctx->key_size, GFP_KERNEL);
        if (!req_ctx->out_buf) {
                kfree(req_ctx->in_buf);
                return -ENOMEM;
        }

        pkcs1pad_sg_set_buf(req_ctx->out_sg, req_ctx->out_buf,
                        ctx->key_size, NULL);

        akcipher_request_set_tfm(&req_ctx->child_req, ctx->child);
        akcipher_request_set_callback(&req_ctx->child_req, req->base.flags,
                        pkcs1pad_encrypt_sign_complete_cb, req);

        /* Reuse output buffer */
        akcipher_request_set_crypt(&req_ctx->child_req, req_ctx->in_sg,
                                   req->dst, ctx->key_size - 1, req->dst_len);

        err = crypto_akcipher_encrypt(&req_ctx->child_req);
        if (err != -EINPROGRESS && err != -EBUSY)
                return pkcs1pad_encrypt_sign_complete(req, err);

        return err;
}

static int pkcs1pad_decrypt_complete(struct akcipher_request *req, int err)
{
        struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
        struct pkcs1pad_ctx *ctx = akcipher_tfm_ctx(tfm);
        struct pkcs1pad_request *req_ctx = akcipher_request_ctx(req);
        unsigned int dst_len;
        unsigned int pos;
        u8 *out_buf;

        if (err)
                goto done;

        err = -EINVAL;
        dst_len = req_ctx->child_req.dst_len;
        if (dst_len < ctx->key_size - 1)
                goto done;

        out_buf = req_ctx->out_buf;
        if (dst_len == ctx->key_size) {
                if (out_buf[0] != 0x00)
                        /* Decrypted value had no leading 0 byte */
                        goto done;

                dst_len--;
                out_buf++;
        }

        if (out_buf[0] != 0x02)
                goto done;

        for (pos = 1; pos < dst_len; pos++)
                if (out_buf[pos] == 0x00)
                        break;
        if (pos < 9 || pos == dst_len)
                goto done;
        pos++;

        err = 0;

        if (req->dst_len < dst_len - pos)
                err = -EOVERFLOW;
        req->dst_len = dst_len - pos;

        if (!err)
                sg_copy_from_buffer(req->dst,
                                sg_nents_for_len(req->dst, req->dst_len),
                                out_buf + pos, req->dst_len);

done:
        kfree_sensitive(req_ctx->out_buf);

        return err;
}

static void pkcs1pad_decrypt_complete_cb(
                struct crypto_async_request *child_async_req, int err)
{
        struct akcipher_request *req = child_async_req->data;
        struct crypto_async_request async_req;

        if (err == -EINPROGRESS)
                return;

        async_req.data = req->base.data;
        async_req.tfm = crypto_akcipher_tfm(crypto_akcipher_reqtfm(req));
        async_req.flags = child_async_req->flags;
        req->base.complete(&async_req, pkcs1pad_decrypt_complete(req, err));
}

static int pkcs1pad_decrypt(struct akcipher_request *req)
{
        struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
        struct pkcs1pad_ctx *ctx = akcipher_tfm_ctx(tfm);
        struct pkcs1pad_request *req_ctx = akcipher_request_ctx(req);
        int err;

        if (!ctx->key_size || req->src_len != ctx->key_size)
                return -EINVAL;

        req_ctx->out_buf = kmalloc(ctx->key_size, GFP_KERNEL);
        if (!req_ctx->out_buf)
                return -ENOMEM;

        pkcs1pad_sg_set_buf(req_ctx->out_sg, req_ctx->out_buf,
                            ctx->key_size, NULL);

        akcipher_request_set_tfm(&req_ctx->child_req, ctx->child);
        akcipher_request_set_callback(&req_ctx->child_req, req->base.flags,
                        pkcs1pad_decrypt_complete_cb, req);

        /* Reuse input buffer, output to a new buffer */
        akcipher_request_set_crypt(&req_ctx->child_req, req->src,
                                   req_ctx->out_sg, req->src_len,
                                   ctx->key_size);

        err = crypto_akcipher_decrypt(&req_ctx->child_req);
        if (err != -EINPROGRESS && err != -EBUSY)
                return pkcs1pad_decrypt_complete(req, err);

        return err;
}

static int pkcs1pad_sign(struct akcipher_request *req)
{
        struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
        struct pkcs1pad_ctx *ctx = akcipher_tfm_ctx(tfm);
        struct pkcs1pad_request *req_ctx = akcipher_request_ctx(req);
        struct akcipher_instance *inst = akcipher_alg_instance(tfm);
        struct pkcs1pad_inst_ctx *ictx = akcipher_instance_ctx(inst);
        const struct rsa_asn1_template *digest_info = ictx->digest_info;
        int err;
        unsigned int ps_end, digest_size = 0;

        if (!ctx->key_size)
                return -EINVAL;

        digest_size = digest_info->size;

        if (req->src_len + digest_size > ctx->key_size - 11)
                return -EOVERFLOW;

        if (req->dst_len < ctx->key_size) {
                req->dst_len = ctx->key_size;
                return -EOVERFLOW;
        }

        req_ctx->in_buf = kmalloc(ctx->key_size - 1 - req->src_len,
                                  GFP_KERNEL);
        if (!req_ctx->in_buf)
                return -ENOMEM;

        ps_end = ctx->key_size - digest_size - req->src_len - 2;
        req_ctx->in_buf[0] = 0x01;
        memset(req_ctx->in_buf + 1, 0xff, ps_end - 1);
        req_ctx->in_buf[ps_end] = 0x00;

        memcpy(req_ctx->in_buf + ps_end + 1, digest_info->data,
               digest_info->size);

        pkcs1pad_sg_set_buf(req_ctx->in_sg, req_ctx->in_buf,
                        ctx->key_size - 1 - req->src_len, req->src);

        akcipher_request_set_tfm(&req_ctx->child_req, ctx->child);
        akcipher_request_set_callback(&req_ctx->child_req, req->base.flags,
                        pkcs1pad_encrypt_sign_complete_cb, req);

        /* Reuse output buffer */
        akcipher_request_set_crypt(&req_ctx->child_req, req_ctx->in_sg,
                                   req->dst, ctx->key_size - 1, req->dst_len);

        err = crypto_akcipher_decrypt(&req_ctx->child_req);
        if (err != -EINPROGRESS && err != -EBUSY)
                return pkcs1pad_encrypt_sign_complete(req, err);

        return err;
}

static int pkcs1pad_verify_complete(struct akcipher_request *req, int err)
{
        struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
        struct pkcs1pad_ctx *ctx = akcipher_tfm_ctx(tfm);
        struct pkcs1pad_request *req_ctx = akcipher_request_ctx(req);
        struct akcipher_instance *inst = akcipher_alg_instance(tfm);
        struct pkcs1pad_inst_ctx *ictx = akcipher_instance_ctx(inst);
        const struct rsa_asn1_template *digest_info = ictx->digest_info;
        unsigned int dst_len;
        unsigned int pos;
        u8 *out_buf;

        if (err)
                goto done;

        err = -EINVAL;
        dst_len = req_ctx->child_req.dst_len;
        if (dst_len < ctx->key_size - 1)
                goto done;

        out_buf = req_ctx->out_buf;
        if (dst_len == ctx->key_size) {
                if (out_buf[0] != 0x00)
                        /* Decrypted value had no leading 0 byte */
                        goto done;

                dst_len--;
                out_buf++;
        }

        err = -EBADMSG;
        if (out_buf[0] != 0x01)
                goto done;

        for (pos = 1; pos < dst_len; pos++)
                if (out_buf[pos] != 0xff)
                        break;

        if (pos < 9 || pos == dst_len || out_buf[pos] != 0x00)
                goto done;
        pos++;

        if (crypto_memneq(out_buf + pos, digest_info->data, digest_info->size))
                goto done;

        pos += digest_info->size;

        err = 0;

        if (req->dst_len < dst_len - pos)
                err = -EOVERFLOW;
        req->dst_len = dst_len - pos;

        if (!err)
                sg_copy_from_buffer(req->dst,
                                sg_nents_for_len(req->dst, req->dst_len),
                                out_buf + pos, req->dst_len);
done:
        kfree_sensitive(req_ctx->out_buf);

        return err;
}

static void pkcs1pad_verify_complete_cb(
                struct crypto_async_request *child_async_req, int err)
{
        struct akcipher_request *req = child_async_req->data;
        struct crypto_async_request async_req;

        if (err == -EINPROGRESS)
                return;

        async_req.data = req->base.data;
        async_req.tfm = crypto_akcipher_tfm(crypto_akcipher_reqtfm(req));
        async_req.flags = child_async_req->flags;
        req->base.complete(&async_req, pkcs1pad_verify_complete(req, err));
}

/*
 * The verify operation is here for completeness similar to the verification
 * defined in RFC2313 section 10.2 except that block type 0 is not accepted,
 * as in RFC2437.  RFC2437 section 9.2 doesn't define any operation to
 * retrieve the DigestInfo from a signature, instead the user is expected
 * to call the sign operation to generate the expected signature and compare
 * signatures instead of the message-digests.
 */
static int pkcs1pad_verify(struct akcipher_request *req)
{
        struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
        struct pkcs1pad_ctx *ctx = akcipher_tfm_ctx(tfm);
        struct pkcs1pad_request *req_ctx = akcipher_request_ctx(req);
        int err;

        if (!ctx->key_size || req->src_len < ctx->key_size)
                return -EINVAL;

        req_ctx->out_buf = kmalloc(ctx->key_size, GFP_KERNEL);
        if (!req_ctx->out_buf)
                return -ENOMEM;

        pkcs1pad_sg_set_buf(req_ctx->out_sg, req_ctx->out_buf,
                            ctx->key_size, NULL);

        akcipher_request_set_tfm(&req_ctx->child_req, ctx->child);
        akcipher_request_set_callback(&req_ctx->child_req, req->base.flags,
                        pkcs1pad_verify_complete_cb, req);

        /* Reuse input buffer, output to a new buffer */
        akcipher_request_set_crypt(&req_ctx->child_req, req->src,
                                   req_ctx->out_sg, req->src_len,
                                   ctx->key_size);

        err = crypto_akcipher_encrypt(&req_ctx->child_req);
        if (err != -EINPROGRESS && err != -EBUSY)
                return pkcs1pad_verify_complete(req, err);

        return err;
}

static int pkcs1pad_init_tfm(struct crypto_akcipher *tfm)
{
        struct akcipher_instance *inst = akcipher_alg_instance(tfm);
        struct pkcs1pad_inst_ctx *ictx = akcipher_instance_ctx(inst);
        struct pkcs1pad_ctx *ctx = akcipher_tfm_ctx(tfm);
        struct crypto_akcipher *child_tfm;

        child_tfm = crypto_spawn_akcipher(&ictx->spawn);
        if (IS_ERR(child_tfm))
                return PTR_ERR(child_tfm);

        ctx->child = child_tfm;
        return 0;
}

static void pkcs1pad_exit_tfm(struct crypto_akcipher *tfm)
{
        struct pkcs1pad_ctx *ctx = akcipher_tfm_ctx(tfm);

        crypto_free_akcipher(ctx->child);
}

static void pkcs1pad_free(struct akcipher_instance *inst)
{
        struct pkcs1pad_inst_ctx *ctx = akcipher_instance_ctx(inst);
        struct crypto_akcipher_spawn *spawn = &ctx->spawn;

        crypto_drop_akcipher(spawn);
        kfree(inst);
}

static int pkcs1pad_create(struct crypto_template *tmpl, struct rtattr **tb)
{
        const struct rsa_asn1_template *digest_info;
        struct crypto_attr_type *algt;
        struct akcipher_instance *inst;
        struct pkcs1pad_inst_ctx *ctx;
        struct crypto_akcipher_spawn *spawn;
        struct akcipher_alg *rsa_alg;
        const char *rsa_alg_name;
        const char *hash_name;
        int err;

        algt = crypto_get_attr_type(tb);
        if (IS_ERR(algt))
                return PTR_ERR(algt);

        if ((algt->type ^ CRYPTO_ALG_TYPE_AKCIPHER) & algt->mask)
                return -EINVAL;

        rsa_alg_name = crypto_attr_alg_name(tb[1]);
        if (IS_ERR(rsa_alg_name))
                return PTR_ERR(rsa_alg_name);

        hash_name = crypto_attr_alg_name(tb[2]);
        if (IS_ERR(hash_name))
                return PTR_ERR(hash_name);

        digest_info = rsa_lookup_asn1(hash_name);
        if (!digest_info)
                return -EINVAL;

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

        ctx = akcipher_instance_ctx(inst);
        spawn = &ctx->spawn;
        ctx->digest_info = digest_info;

        crypto_set_spawn(&spawn->base, akcipher_crypto_instance(inst));
        err = crypto_grab_akcipher(spawn, rsa_alg_name, 0,
                        crypto_requires_sync(algt->type, algt->mask));
        if (err)
                goto out_free_inst;

        rsa_alg = crypto_spawn_akcipher_alg(spawn);

        err = -ENAMETOOLONG;

        if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
                     "pkcs1pad(%s,%s)", rsa_alg->base.cra_name, hash_name) >=
            CRYPTO_MAX_ALG_NAME ||
            snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
                     "pkcs1pad(%s,%s)",
                     rsa_alg->base.cra_driver_name, hash_name) >=
            CRYPTO_MAX_ALG_NAME)
                goto out_drop_alg;

        inst->alg.base.cra_flags = rsa_alg->base.cra_flags & CRYPTO_ALG_ASYNC;
        inst->alg.base.cra_priority = rsa_alg->base.cra_priority;
        inst->alg.base.cra_ctxsize = sizeof(struct pkcs1pad_ctx);

        inst->alg.init = pkcs1pad_init_tfm;
        inst->alg.exit = pkcs1pad_exit_tfm;

        inst->alg.encrypt = pkcs1pad_encrypt;
        inst->alg.decrypt = pkcs1pad_decrypt;
        inst->alg.sign = pkcs1pad_sign;
        inst->alg.verify = pkcs1pad_verify;
        inst->alg.set_pub_key = pkcs1pad_set_pub_key;
        inst->alg.set_priv_key = pkcs1pad_set_priv_key;
        inst->alg.max_size = pkcs1pad_get_max_size;
        inst->alg.reqsize = sizeof(struct pkcs1pad_request) + rsa_alg->reqsize;

        inst->free = pkcs1pad_free;

        err = akcipher_register_instance(tmpl, inst);
        if (err)
                goto out_drop_alg;

        return 0;

out_drop_alg:
        crypto_drop_akcipher(spawn);
out_free_inst:
        kfree(inst);
        return err;
}

struct crypto_template rsa_pkcs1pad_tmpl = {
        .name = "pkcs1pad",
        .create = pkcs1pad_create,
        .module = THIS_MODULE,
};