// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright 2019 Google LLC
 */

/*
 * Refer to Documentation/block/inline-encryption.rst for detailed explanation.
 */

#define pr_fmt(fmt) "blk-crypto: " fmt

#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/keyslot-manager.h>
#include <linux/module.h>
#include <linux/slab.h>

#include "blk-crypto-internal.h"

const struct blk_crypto_mode blk_crypto_modes[] = {
        [BLK_ENCRYPTION_MODE_AES_256_XTS] = {
                .cipher_str = "xts(aes)",
                .keysize = 64,
                .ivsize = 16,
        },
        [BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV] = {
                .cipher_str = "essiv(cbc(aes),sha256)",
                .keysize = 16,
                .ivsize = 16,
        },
        [BLK_ENCRYPTION_MODE_ADIANTUM] = {
                .cipher_str = "adiantum(xchacha12,aes)",
                .keysize = 32,
                .ivsize = 32,
        },
};

/*
 * This number needs to be at least (the number of threads doing IO
 * concurrently) * (maximum recursive depth of a bio), so that we don't
 * deadlock on crypt_ctx allocations. The default is chosen to be the same
 * as the default number of post read contexts in both EXT4 and F2FS.
 */
static int num_prealloc_crypt_ctxs = 128;

module_param(num_prealloc_crypt_ctxs, int, 0444);
MODULE_PARM_DESC(num_prealloc_crypt_ctxs,
                "Number of bio crypto contexts to preallocate");

static struct kmem_cache *bio_crypt_ctx_cache;
static mempool_t *bio_crypt_ctx_pool;

static int __init bio_crypt_ctx_init(void)
{
        size_t i;

        bio_crypt_ctx_cache = KMEM_CACHE(bio_crypt_ctx, 0);
        if (!bio_crypt_ctx_cache)
                goto out_no_mem;

        bio_crypt_ctx_pool = mempool_create_slab_pool(num_prealloc_crypt_ctxs,
                                                      bio_crypt_ctx_cache);
        if (!bio_crypt_ctx_pool)
                goto out_no_mem;

        /* This is assumed in various places. */
        BUILD_BUG_ON(BLK_ENCRYPTION_MODE_INVALID != 0);

        /* Sanity check that no algorithm exceeds the defined limits. */
        for (i = 0; i < BLK_ENCRYPTION_MODE_MAX; i++) {
                BUG_ON(blk_crypto_modes[i].keysize > BLK_CRYPTO_MAX_KEY_SIZE);
                BUG_ON(blk_crypto_modes[i].ivsize > BLK_CRYPTO_MAX_IV_SIZE);
        }

        return 0;
out_no_mem:
        panic("Failed to allocate mem for bio crypt ctxs\n");
}
subsys_initcall(bio_crypt_ctx_init);

void bio_crypt_set_ctx(struct bio *bio, const struct blk_crypto_key *key,
                       const u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE], gfp_t gfp_mask)
{
        struct bio_crypt_ctx *bc;

        /*
         * The caller must use a gfp_mask that contains __GFP_DIRECT_RECLAIM so
         * that the mempool_alloc() can't fail.
         */
        WARN_ON_ONCE(!(gfp_mask & __GFP_DIRECT_RECLAIM));

        bc = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);

        bc->bc_key = key;
        memcpy(bc->bc_dun, dun, sizeof(bc->bc_dun));

        bio->bi_crypt_context = bc;
}

void __bio_crypt_free_ctx(struct bio *bio)
{
        mempool_free(bio->bi_crypt_context, bio_crypt_ctx_pool);
        bio->bi_crypt_context = NULL;
}

int __bio_crypt_clone(struct bio *dst, struct bio *src, gfp_t gfp_mask)
{
        dst->bi_crypt_context = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
        if (!dst->bi_crypt_context)
                return -ENOMEM;
        *dst->bi_crypt_context = *src->bi_crypt_context;
        return 0;
}
EXPORT_SYMBOL_GPL(__bio_crypt_clone);

/* Increments @dun by @inc, treating @dun as a multi-limb integer. */
void bio_crypt_dun_increment(u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
                             unsigned int inc)
{
        int i;

        for (i = 0; inc && i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++) {
                dun[i] += inc;
                /*
                 * If the addition in this limb overflowed, then we need to
                 * carry 1 into the next limb. Else the carry is 0.
                 */
                if (dun[i] < inc)
                        inc = 1;
                else
                        inc = 0;
        }
}

void __bio_crypt_advance(struct bio *bio, unsigned int bytes)
{
        struct bio_crypt_ctx *bc = bio->bi_crypt_context;

        bio_crypt_dun_increment(bc->bc_dun,
                                bytes >> bc->bc_key->data_unit_size_bits);
}

/*
 * Returns true if @bc->bc_dun plus @bytes converted to data units is equal to
 * @next_dun, treating the DUNs as multi-limb integers.
 */
bool bio_crypt_dun_is_contiguous(const struct bio_crypt_ctx *bc,
                                 unsigned int bytes,
                                 const u64 next_dun[BLK_CRYPTO_DUN_ARRAY_SIZE])
{
        int i;
        unsigned int carry = bytes >> bc->bc_key->data_unit_size_bits;

        for (i = 0; i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++) {
                if (bc->bc_dun[i] + carry != next_dun[i])
                        return false;
                /*
                 * If the addition in this limb overflowed, then we need to
                 * carry 1 into the next limb. Else the carry is 0.
                 */
                if ((bc->bc_dun[i] + carry) < carry)
                        carry = 1;
                else
                        carry = 0;
        }

        /* If the DUN wrapped through 0, don't treat it as contiguous. */
        return carry == 0;
}

/*
 * Checks that two bio crypt contexts are compatible - i.e. that
 * they are mergeable except for data_unit_num continuity.
 */
static bool bio_crypt_ctx_compatible(struct bio_crypt_ctx *bc1,
                                     struct bio_crypt_ctx *bc2)
{
        if (!bc1)
                return !bc2;

        return bc2 && bc1->bc_key == bc2->bc_key;
}

bool bio_crypt_rq_ctx_compatible(struct request *rq, struct bio *bio)
{
        return bio_crypt_ctx_compatible(rq->crypt_ctx, bio->bi_crypt_context);
}

/*
 * Checks that two bio crypt contexts are compatible, and also
 * that their data_unit_nums are continuous (and can hence be merged)
 * in the order @bc1 followed by @bc2.
 */
bool bio_crypt_ctx_mergeable(struct bio_crypt_ctx *bc1, unsigned int bc1_bytes,
                             struct bio_crypt_ctx *bc2)
{
        if (!bio_crypt_ctx_compatible(bc1, bc2))
                return false;

        return !bc1 || bio_crypt_dun_is_contiguous(bc1, bc1_bytes, bc2->bc_dun);
}

/* Check that all I/O segments are data unit aligned. */
static bool bio_crypt_check_alignment(struct bio *bio)
{
        const unsigned int data_unit_size =
                bio->bi_crypt_context->bc_key->crypto_cfg.data_unit_size;
        struct bvec_iter iter;
        struct bio_vec bv;

        bio_for_each_segment(bv, bio, iter) {
                if (!IS_ALIGNED(bv.bv_len | bv.bv_offset, data_unit_size))
                        return false;
        }

        return true;
}

blk_status_t __blk_crypto_init_request(struct request *rq)
{
        return blk_ksm_get_slot_for_key(rq->q->ksm, rq->crypt_ctx->bc_key,
                                        &rq->crypt_keyslot);
}

/**
 * __blk_crypto_free_request - Uninitialize the crypto fields of a request.
 *
 * @rq: The request whose crypto fields to uninitialize.
 *
 * Completely uninitializes the crypto fields of a request. If a keyslot has
 * been programmed into some inline encryption hardware, that keyslot is
 * released. The rq->crypt_ctx is also freed.
 */
void __blk_crypto_free_request(struct request *rq)
{
        blk_ksm_put_slot(rq->crypt_keyslot);
        mempool_free(rq->crypt_ctx, bio_crypt_ctx_pool);
        blk_crypto_rq_set_defaults(rq);
}

/**
 * __blk_crypto_bio_prep - Prepare bio for inline encryption
 *
 * @bio_ptr: pointer to original bio pointer
 *
 * If the bio crypt context provided for the bio is supported by the underlying
 * device's inline encryption hardware, do nothing.
 *
 * Otherwise, try to perform en/decryption for this bio by falling back to the
 * kernel crypto API. When the crypto API fallback is used for encryption,
 * blk-crypto may choose to split the bio into 2 - the first one that will
 * continue to be processed and the second one that will be resubmitted via
 * submit_bio_noacct. A bounce bio will be allocated to encrypt the contents
 * of the aforementioned "first one", and *bio_ptr will be updated to this
 * bounce bio.
 *
 * Caller must ensure bio has bio_crypt_ctx.
 *
 * Return: true on success; false on error (and bio->bi_status will be set
 *         appropriately, and bio_endio() will have been called so bio
 *         submission should abort).
 */
bool __blk_crypto_bio_prep(struct bio **bio_ptr)
{
        struct bio *bio = *bio_ptr;
        const struct blk_crypto_key *bc_key = bio->bi_crypt_context->bc_key;

        /* Error if bio has no data. */
        if (WARN_ON_ONCE(!bio_has_data(bio))) {
                bio->bi_status = BLK_STS_IOERR;
                goto fail;
        }

        if (!bio_crypt_check_alignment(bio)) {
                bio->bi_status = BLK_STS_IOERR;
                goto fail;
        }

        /*
         * Success if device supports the encryption context, or if we succeeded
         * in falling back to the crypto API.
         */
        if (blk_ksm_crypto_cfg_supported(bio->bi_bdev->bd_disk->queue->ksm,
                                         &bc_key->crypto_cfg))
                return true;

        if (blk_crypto_fallback_bio_prep(bio_ptr))
                return true;
fail:
        bio_endio(*bio_ptr);
        return false;
}

int __blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
                             gfp_t gfp_mask)
{
        if (!rq->crypt_ctx) {
                rq->crypt_ctx = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
                if (!rq->crypt_ctx)
                        return -ENOMEM;
        }
        *rq->crypt_ctx = *bio->bi_crypt_context;
        return 0;
}

/**
 * blk_crypto_init_key() - Prepare a key for use with blk-crypto
 * @blk_key: Pointer to the blk_crypto_key to initialize.
 * @raw_key: Pointer to the raw key. Must be the correct length for the chosen
 *           @crypto_mode; see blk_crypto_modes[].
 * @crypto_mode: identifier for the encryption algorithm to use
 * @dun_bytes: number of bytes that will be used to specify the DUN when this
 *             key is used
 * @data_unit_size: the data unit size to use for en/decryption
 *
 * Return: 0 on success, -errno on failure.  The caller is responsible for
 *         zeroizing both blk_key and raw_key when done with them.
 */
int blk_crypto_init_key(struct blk_crypto_key *blk_key, const u8 *raw_key,
                        enum blk_crypto_mode_num crypto_mode,
                        unsigned int dun_bytes,
                        unsigned int data_unit_size)
{
        const struct blk_crypto_mode *mode;

        memset(blk_key, 0, sizeof(*blk_key));

        if (crypto_mode >= ARRAY_SIZE(blk_crypto_modes))
                return -EINVAL;

        mode = &blk_crypto_modes[crypto_mode];
        if (mode->keysize == 0)
                return -EINVAL;

        if (dun_bytes == 0 || dun_bytes > mode->ivsize)
                return -EINVAL;

        if (!is_power_of_2(data_unit_size))
                return -EINVAL;

        blk_key->crypto_cfg.crypto_mode = crypto_mode;
        blk_key->crypto_cfg.dun_bytes = dun_bytes;
        blk_key->crypto_cfg.data_unit_size = data_unit_size;
        blk_key->data_unit_size_bits = ilog2(data_unit_size);
        blk_key->size = mode->keysize;
        memcpy(blk_key->raw, raw_key, mode->keysize);

        return 0;
}

/*
 * Check if bios with @cfg can be en/decrypted by blk-crypto (i.e. either the
 * request queue it's submitted to supports inline crypto, or the
 * blk-crypto-fallback is enabled and supports the cfg).
 */
bool blk_crypto_config_supported(struct request_queue *q,
                                 const struct blk_crypto_config *cfg)
{
        return IS_ENABLED(CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK) ||
               blk_ksm_crypto_cfg_supported(q->ksm, cfg);
}

/**
 * blk_crypto_start_using_key() - Start using a blk_crypto_key on a device
 * @key: A key to use on the device
 * @q: the request queue for the device
 *
 * Upper layers must call this function to ensure that either the hardware
 * supports the key's crypto settings, or the crypto API fallback has transforms
 * for the needed mode allocated and ready to go. This function may allocate
 * an skcipher, and *should not* be called from the data path, since that might
 * cause a deadlock
 *
 * Return: 0 on success; -ENOPKG if the hardware doesn't support the key and
 *         blk-crypto-fallback is either disabled or the needed algorithm
 *         is disabled in the crypto API; or another -errno code.
 */
int blk_crypto_start_using_key(const struct blk_crypto_key *key,
                               struct request_queue *q)
{
        if (blk_ksm_crypto_cfg_supported(q->ksm, &key->crypto_cfg))
                return 0;
        return blk_crypto_fallback_start_using_mode(key->crypto_cfg.crypto_mode);
}

/**
 * blk_crypto_evict_key() - Evict a key from any inline encryption hardware
 *                          it may have been programmed into
 * @q: The request queue who's associated inline encryption hardware this key
 *     might have been programmed into
 * @key: The key to evict
 *
 * Upper layers (filesystems) must call this function to ensure that a key is
 * evicted from any hardware that it might have been programmed into.  The key
 * must not be in use by any in-flight IO when this function is called.
 *
 * Return: 0 on success or if key is not present in the q's ksm, -err on error.
 */
int blk_crypto_evict_key(struct request_queue *q,
                         const struct blk_crypto_key *key)
{
        if (blk_ksm_crypto_cfg_supported(q->ksm, &key->crypto_cfg))
                return blk_ksm_evict_key(q->ksm, key);

        /*
         * If the request queue's associated inline encryption hardware didn't
         * have support for the key, then the key might have been programmed
         * into the fallback keyslot manager, so try to evict from there.
         */
        return blk_crypto_fallback_evict_key(key);
}
EXPORT_SYMBOL_GPL(blk_crypto_evict_key);