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![Satya Tangirala](/assets/img/avatar_default.png)
Now that device mapper supports inline encryption, add the ability to evict keys from all underlying devices. When an upper layer requests a key eviction, we simply iterate through all underlying devices and evict that key from each device. Co-developed-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Satya Tangirala <satyat@google.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
412 lines
12 KiB
C
412 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright 2019 Google LLC
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*/
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/*
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* Refer to Documentation/block/inline-encryption.rst for detailed explanation.
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*/
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#define pr_fmt(fmt) "blk-crypto: " fmt
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#include <linux/bio.h>
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#include <linux/blkdev.h>
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#include <linux/keyslot-manager.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include "blk-crypto-internal.h"
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const struct blk_crypto_mode blk_crypto_modes[] = {
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[BLK_ENCRYPTION_MODE_AES_256_XTS] = {
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.cipher_str = "xts(aes)",
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.keysize = 64,
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.ivsize = 16,
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},
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[BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV] = {
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.cipher_str = "essiv(cbc(aes),sha256)",
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.keysize = 16,
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.ivsize = 16,
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},
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[BLK_ENCRYPTION_MODE_ADIANTUM] = {
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.cipher_str = "adiantum(xchacha12,aes)",
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.keysize = 32,
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.ivsize = 32,
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},
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};
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/*
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* This number needs to be at least (the number of threads doing IO
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* concurrently) * (maximum recursive depth of a bio), so that we don't
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* deadlock on crypt_ctx allocations. The default is chosen to be the same
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* as the default number of post read contexts in both EXT4 and F2FS.
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*/
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static int num_prealloc_crypt_ctxs = 128;
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module_param(num_prealloc_crypt_ctxs, int, 0444);
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MODULE_PARM_DESC(num_prealloc_crypt_ctxs,
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"Number of bio crypto contexts to preallocate");
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static struct kmem_cache *bio_crypt_ctx_cache;
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static mempool_t *bio_crypt_ctx_pool;
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static int __init bio_crypt_ctx_init(void)
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{
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size_t i;
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bio_crypt_ctx_cache = KMEM_CACHE(bio_crypt_ctx, 0);
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if (!bio_crypt_ctx_cache)
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goto out_no_mem;
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bio_crypt_ctx_pool = mempool_create_slab_pool(num_prealloc_crypt_ctxs,
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bio_crypt_ctx_cache);
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if (!bio_crypt_ctx_pool)
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goto out_no_mem;
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/* This is assumed in various places. */
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BUILD_BUG_ON(BLK_ENCRYPTION_MODE_INVALID != 0);
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/* Sanity check that no algorithm exceeds the defined limits. */
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for (i = 0; i < BLK_ENCRYPTION_MODE_MAX; i++) {
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BUG_ON(blk_crypto_modes[i].keysize > BLK_CRYPTO_MAX_KEY_SIZE);
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BUG_ON(blk_crypto_modes[i].ivsize > BLK_CRYPTO_MAX_IV_SIZE);
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}
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return 0;
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out_no_mem:
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panic("Failed to allocate mem for bio crypt ctxs\n");
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}
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subsys_initcall(bio_crypt_ctx_init);
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void bio_crypt_set_ctx(struct bio *bio, const struct blk_crypto_key *key,
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const u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE], gfp_t gfp_mask)
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{
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struct bio_crypt_ctx *bc;
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/*
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* The caller must use a gfp_mask that contains __GFP_DIRECT_RECLAIM so
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* that the mempool_alloc() can't fail.
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*/
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WARN_ON_ONCE(!(gfp_mask & __GFP_DIRECT_RECLAIM));
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bc = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
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bc->bc_key = key;
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memcpy(bc->bc_dun, dun, sizeof(bc->bc_dun));
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bio->bi_crypt_context = bc;
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}
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void __bio_crypt_free_ctx(struct bio *bio)
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{
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mempool_free(bio->bi_crypt_context, bio_crypt_ctx_pool);
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bio->bi_crypt_context = NULL;
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}
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int __bio_crypt_clone(struct bio *dst, struct bio *src, gfp_t gfp_mask)
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{
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dst->bi_crypt_context = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
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if (!dst->bi_crypt_context)
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return -ENOMEM;
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*dst->bi_crypt_context = *src->bi_crypt_context;
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return 0;
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}
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EXPORT_SYMBOL_GPL(__bio_crypt_clone);
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/* Increments @dun by @inc, treating @dun as a multi-limb integer. */
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void bio_crypt_dun_increment(u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
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unsigned int inc)
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{
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int i;
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for (i = 0; inc && i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++) {
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dun[i] += inc;
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/*
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* If the addition in this limb overflowed, then we need to
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* carry 1 into the next limb. Else the carry is 0.
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*/
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if (dun[i] < inc)
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inc = 1;
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else
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inc = 0;
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}
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}
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void __bio_crypt_advance(struct bio *bio, unsigned int bytes)
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{
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struct bio_crypt_ctx *bc = bio->bi_crypt_context;
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bio_crypt_dun_increment(bc->bc_dun,
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bytes >> bc->bc_key->data_unit_size_bits);
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}
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/*
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* Returns true if @bc->bc_dun plus @bytes converted to data units is equal to
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* @next_dun, treating the DUNs as multi-limb integers.
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*/
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bool bio_crypt_dun_is_contiguous(const struct bio_crypt_ctx *bc,
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unsigned int bytes,
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const u64 next_dun[BLK_CRYPTO_DUN_ARRAY_SIZE])
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{
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int i;
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unsigned int carry = bytes >> bc->bc_key->data_unit_size_bits;
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for (i = 0; i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++) {
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if (bc->bc_dun[i] + carry != next_dun[i])
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return false;
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/*
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* If the addition in this limb overflowed, then we need to
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* carry 1 into the next limb. Else the carry is 0.
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*/
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if ((bc->bc_dun[i] + carry) < carry)
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carry = 1;
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else
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carry = 0;
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}
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/* If the DUN wrapped through 0, don't treat it as contiguous. */
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return carry == 0;
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}
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/*
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* Checks that two bio crypt contexts are compatible - i.e. that
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* they are mergeable except for data_unit_num continuity.
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*/
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static bool bio_crypt_ctx_compatible(struct bio_crypt_ctx *bc1,
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struct bio_crypt_ctx *bc2)
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{
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if (!bc1)
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return !bc2;
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return bc2 && bc1->bc_key == bc2->bc_key;
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}
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bool bio_crypt_rq_ctx_compatible(struct request *rq, struct bio *bio)
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{
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return bio_crypt_ctx_compatible(rq->crypt_ctx, bio->bi_crypt_context);
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}
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/*
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* Checks that two bio crypt contexts are compatible, and also
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* that their data_unit_nums are continuous (and can hence be merged)
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* in the order @bc1 followed by @bc2.
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*/
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bool bio_crypt_ctx_mergeable(struct bio_crypt_ctx *bc1, unsigned int bc1_bytes,
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struct bio_crypt_ctx *bc2)
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{
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if (!bio_crypt_ctx_compatible(bc1, bc2))
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return false;
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return !bc1 || bio_crypt_dun_is_contiguous(bc1, bc1_bytes, bc2->bc_dun);
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}
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/* Check that all I/O segments are data unit aligned. */
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static bool bio_crypt_check_alignment(struct bio *bio)
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{
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const unsigned int data_unit_size =
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bio->bi_crypt_context->bc_key->crypto_cfg.data_unit_size;
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struct bvec_iter iter;
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struct bio_vec bv;
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bio_for_each_segment(bv, bio, iter) {
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if (!IS_ALIGNED(bv.bv_len | bv.bv_offset, data_unit_size))
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return false;
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}
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return true;
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}
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blk_status_t __blk_crypto_init_request(struct request *rq)
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{
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return blk_ksm_get_slot_for_key(rq->q->ksm, rq->crypt_ctx->bc_key,
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&rq->crypt_keyslot);
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}
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/**
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* __blk_crypto_free_request - Uninitialize the crypto fields of a request.
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*
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* @rq: The request whose crypto fields to uninitialize.
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*
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* Completely uninitializes the crypto fields of a request. If a keyslot has
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* been programmed into some inline encryption hardware, that keyslot is
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* released. The rq->crypt_ctx is also freed.
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*/
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void __blk_crypto_free_request(struct request *rq)
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{
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blk_ksm_put_slot(rq->crypt_keyslot);
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mempool_free(rq->crypt_ctx, bio_crypt_ctx_pool);
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blk_crypto_rq_set_defaults(rq);
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}
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/**
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* __blk_crypto_bio_prep - Prepare bio for inline encryption
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*
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* @bio_ptr: pointer to original bio pointer
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*
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* If the bio crypt context provided for the bio is supported by the underlying
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* device's inline encryption hardware, do nothing.
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*
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* Otherwise, try to perform en/decryption for this bio by falling back to the
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* kernel crypto API. When the crypto API fallback is used for encryption,
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* blk-crypto may choose to split the bio into 2 - the first one that will
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* continue to be processed and the second one that will be resubmitted via
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* submit_bio_noacct. A bounce bio will be allocated to encrypt the contents
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* of the aforementioned "first one", and *bio_ptr will be updated to this
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* bounce bio.
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*
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* Caller must ensure bio has bio_crypt_ctx.
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*
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* Return: true on success; false on error (and bio->bi_status will be set
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* appropriately, and bio_endio() will have been called so bio
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* submission should abort).
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*/
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bool __blk_crypto_bio_prep(struct bio **bio_ptr)
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{
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struct bio *bio = *bio_ptr;
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const struct blk_crypto_key *bc_key = bio->bi_crypt_context->bc_key;
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/* Error if bio has no data. */
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if (WARN_ON_ONCE(!bio_has_data(bio))) {
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bio->bi_status = BLK_STS_IOERR;
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goto fail;
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}
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if (!bio_crypt_check_alignment(bio)) {
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bio->bi_status = BLK_STS_IOERR;
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goto fail;
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}
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/*
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* Success if device supports the encryption context, or if we succeeded
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* in falling back to the crypto API.
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*/
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if (blk_ksm_crypto_cfg_supported(bio->bi_bdev->bd_disk->queue->ksm,
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&bc_key->crypto_cfg))
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return true;
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if (blk_crypto_fallback_bio_prep(bio_ptr))
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return true;
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fail:
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bio_endio(*bio_ptr);
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return false;
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}
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int __blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
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gfp_t gfp_mask)
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{
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if (!rq->crypt_ctx) {
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rq->crypt_ctx = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
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if (!rq->crypt_ctx)
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return -ENOMEM;
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}
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*rq->crypt_ctx = *bio->bi_crypt_context;
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return 0;
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}
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/**
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* blk_crypto_init_key() - Prepare a key for use with blk-crypto
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* @blk_key: Pointer to the blk_crypto_key to initialize.
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* @raw_key: Pointer to the raw key. Must be the correct length for the chosen
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* @crypto_mode; see blk_crypto_modes[].
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* @crypto_mode: identifier for the encryption algorithm to use
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* @dun_bytes: number of bytes that will be used to specify the DUN when this
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* key is used
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* @data_unit_size: the data unit size to use for en/decryption
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*
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* Return: 0 on success, -errno on failure. The caller is responsible for
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* zeroizing both blk_key and raw_key when done with them.
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*/
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int blk_crypto_init_key(struct blk_crypto_key *blk_key, const u8 *raw_key,
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enum blk_crypto_mode_num crypto_mode,
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unsigned int dun_bytes,
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unsigned int data_unit_size)
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{
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const struct blk_crypto_mode *mode;
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memset(blk_key, 0, sizeof(*blk_key));
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if (crypto_mode >= ARRAY_SIZE(blk_crypto_modes))
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return -EINVAL;
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mode = &blk_crypto_modes[crypto_mode];
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if (mode->keysize == 0)
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return -EINVAL;
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if (dun_bytes == 0 || dun_bytes > BLK_CRYPTO_MAX_IV_SIZE)
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return -EINVAL;
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if (!is_power_of_2(data_unit_size))
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return -EINVAL;
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blk_key->crypto_cfg.crypto_mode = crypto_mode;
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blk_key->crypto_cfg.dun_bytes = dun_bytes;
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blk_key->crypto_cfg.data_unit_size = data_unit_size;
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blk_key->data_unit_size_bits = ilog2(data_unit_size);
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blk_key->size = mode->keysize;
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memcpy(blk_key->raw, raw_key, mode->keysize);
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return 0;
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}
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/*
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* Check if bios with @cfg can be en/decrypted by blk-crypto (i.e. either the
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* request queue it's submitted to supports inline crypto, or the
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* blk-crypto-fallback is enabled and supports the cfg).
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*/
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bool blk_crypto_config_supported(struct request_queue *q,
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const struct blk_crypto_config *cfg)
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{
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return IS_ENABLED(CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK) ||
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blk_ksm_crypto_cfg_supported(q->ksm, cfg);
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}
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/**
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* blk_crypto_start_using_key() - Start using a blk_crypto_key on a device
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* @key: A key to use on the device
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* @q: the request queue for the device
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*
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* Upper layers must call this function to ensure that either the hardware
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* supports the key's crypto settings, or the crypto API fallback has transforms
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* for the needed mode allocated and ready to go. This function may allocate
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* an skcipher, and *should not* be called from the data path, since that might
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* cause a deadlock
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*
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* Return: 0 on success; -ENOPKG if the hardware doesn't support the key and
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* blk-crypto-fallback is either disabled or the needed algorithm
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* is disabled in the crypto API; or another -errno code.
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*/
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int blk_crypto_start_using_key(const struct blk_crypto_key *key,
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struct request_queue *q)
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{
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if (blk_ksm_crypto_cfg_supported(q->ksm, &key->crypto_cfg))
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return 0;
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return blk_crypto_fallback_start_using_mode(key->crypto_cfg.crypto_mode);
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}
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/**
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* blk_crypto_evict_key() - Evict a key from any inline encryption hardware
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* it may have been programmed into
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* @q: The request queue who's associated inline encryption hardware this key
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* might have been programmed into
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* @key: The key to evict
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*
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* Upper layers (filesystems) must call this function to ensure that a key is
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* evicted from any hardware that it might have been programmed into. The key
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* must not be in use by any in-flight IO when this function is called.
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*
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* Return: 0 on success or if key is not present in the q's ksm, -err on error.
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*/
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int blk_crypto_evict_key(struct request_queue *q,
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const struct blk_crypto_key *key)
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{
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if (blk_ksm_crypto_cfg_supported(q->ksm, &key->crypto_cfg))
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return blk_ksm_evict_key(q->ksm, key);
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/*
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* If the request queue's associated inline encryption hardware didn't
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* have support for the key, then the key might have been programmed
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* into the fallback keyslot manager, so try to evict from there.
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*/
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return blk_crypto_fallback_evict_key(key);
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}
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EXPORT_SYMBOL_GPL(blk_crypto_evict_key);
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