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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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/* * HCTR2 is a length-preserving encryption mode that is efficient on * processors with instructions to accelerate AES and carryless * multiplication, e.g. x86 processors with AES-NI and CLMUL, and ARM * processors with the ARMv8 crypto extensions. * * For more details, see the paper: "Length-preserving encryption with HCTR2" * (https://eprint.iacr.org/2021/1441.pdf) */
#include <crypto/gf128hash.h>#include <crypto/internal/cipher.h>#include <crypto/internal/skcipher.h>#include <crypto/scatterwalk.h>#include <linux/module.h>
#define BLOCKCIPHER_BLOCK_SIZE 16
/* * The specification allows variable-length tweaks, but Linux's crypto API * currently only allows algorithms to support a single length. The "natural" * tweak length for HCTR2 is 16, since that fits into one POLYVAL block for * the best performance. But longer tweaks are useful for fscrypt, to avoid * needing to derive per-file keys. So instead we use two blocks, or 32 bytes. */#define TWEAK_SIZE 32
struct hctr2_instance_ctx { struct crypto_cipher_spawn blockcipher_spawn; struct crypto_skcipher_spawn xctr_spawn;};
struct hctr2_tfm_ctx { struct crypto_cipher *blockcipher; struct crypto_skcipher *xctr; struct polyval_key poly_key; struct polyval_elem hashed_tweaklens[2]; u8 L[BLOCKCIPHER_BLOCK_SIZE];};
struct hctr2_request_ctx { u8 first_block[BLOCKCIPHER_BLOCK_SIZE]; u8 xctr_iv[BLOCKCIPHER_BLOCK_SIZE]; struct scatterlist *bulk_part_dst; struct scatterlist *bulk_part_src; struct scatterlist sg_src[2]; struct scatterlist sg_dst[2]; struct polyval_elem hashed_tweak; /* * skcipher sub-request size is unknown at compile-time, so it needs to * go after the members with known sizes. */ union { struct polyval_ctx poly_ctx; struct skcipher_request xctr_req; } u;};
/* * The input data for each HCTR2 hash step begins with a 16-byte block that * contains the tweak length and a flag that indicates whether the input is evenly * divisible into blocks. Since this implementation only supports one tweak * length, we precompute the two hash states resulting from hashing the two * possible values of this initial block. This reduces by one block the amount of * data that needs to be hashed for each encryption/decryption * * These precomputed hashes are stored in hctr2_tfm_ctx. */static void hctr2_hash_tweaklens(struct hctr2_tfm_ctx *tctx){ struct polyval_ctx ctx;
for (int has_remainder = 0; has_remainder < 2; has_remainder++) { const __le64 tweak_length_block[2] = { cpu_to_le64(TWEAK_SIZE * 8 * 2 + 2 + has_remainder), };
polyval_init(&ctx, &tctx->poly_key); polyval_update(&ctx, (const u8 *)&tweak_length_block, sizeof(tweak_length_block)); static_assert(sizeof(tweak_length_block) == POLYVAL_BLOCK_SIZE); polyval_export_blkaligned( &ctx, &tctx->hashed_tweaklens[has_remainder]); } memzero_explicit(&ctx, sizeof(ctx));}
static int hctr2_setkey(struct crypto_skcipher *tfm, const u8 *key, unsigned int keylen){ struct hctr2_tfm_ctx *tctx = crypto_skcipher_ctx(tfm); u8 hbar[BLOCKCIPHER_BLOCK_SIZE]; int err;
crypto_cipher_clear_flags(tctx->blockcipher, CRYPTO_TFM_REQ_MASK); crypto_cipher_set_flags(tctx->blockcipher, crypto_skcipher_get_flags(tfm) & CRYPTO_TFM_REQ_MASK); err = crypto_cipher_setkey(tctx->blockcipher, key, keylen); if (err) return err;
crypto_skcipher_clear_flags(tctx->xctr, CRYPTO_TFM_REQ_MASK); crypto_skcipher_set_flags(tctx->xctr, crypto_skcipher_get_flags(tfm) & CRYPTO_TFM_REQ_MASK); err = crypto_skcipher_setkey(tctx->xctr, key, keylen); if (err) return err;
memset(hbar, 0, sizeof(hbar)); crypto_cipher_encrypt_one(tctx->blockcipher, hbar, hbar);
memset(tctx->L, 0, sizeof(tctx->L)); tctx->L[0] = 0x01; crypto_cipher_encrypt_one(tctx->blockcipher, tctx->L, tctx->L);
static_assert(sizeof(hbar) == POLYVAL_BLOCK_SIZE); polyval_preparekey(&tctx->poly_key, hbar); memzero_explicit(hbar, sizeof(hbar));
hctr2_hash_tweaklens(tctx); return 0;}
static void hctr2_hash_tweak(struct skcipher_request *req){ struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); const struct hctr2_tfm_ctx *tctx = crypto_skcipher_ctx(tfm); struct hctr2_request_ctx *rctx = skcipher_request_ctx(req); struct polyval_ctx *poly_ctx = &rctx->u.poly_ctx; bool has_remainder = req->cryptlen % POLYVAL_BLOCK_SIZE;
polyval_import_blkaligned(poly_ctx, &tctx->poly_key, &tctx->hashed_tweaklens[has_remainder]); polyval_update(poly_ctx, req->iv, TWEAK_SIZE);
// Store the hashed tweak, since we need it when computing both // H(T || N) and H(T || V). static_assert(TWEAK_SIZE % POLYVAL_BLOCK_SIZE == 0); polyval_export_blkaligned(poly_ctx, &rctx->hashed_tweak);}
static void hctr2_hash_message(struct skcipher_request *req, struct scatterlist *sgl, u8 digest[POLYVAL_DIGEST_SIZE]){ static const u8 padding = 0x1; struct hctr2_request_ctx *rctx = skcipher_request_ctx(req); struct polyval_ctx *poly_ctx = &rctx->u.poly_ctx; const unsigned int bulk_len = req->cryptlen - BLOCKCIPHER_BLOCK_SIZE; struct sg_mapping_iter miter; int i; int n = 0;
sg_miter_start(&miter, sgl, sg_nents(sgl), SG_MITER_FROM_SG | SG_MITER_ATOMIC); for (i = 0; i < bulk_len; i += n) { sg_miter_next(&miter); n = min_t(unsigned int, miter.length, bulk_len - i); polyval_update(poly_ctx, miter.addr, n); } sg_miter_stop(&miter);
if (req->cryptlen % BLOCKCIPHER_BLOCK_SIZE) polyval_update(poly_ctx, &padding, 1); polyval_final(poly_ctx, digest);}
static int hctr2_finish(struct skcipher_request *req){ struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); const struct hctr2_tfm_ctx *tctx = crypto_skcipher_ctx(tfm); struct hctr2_request_ctx *rctx = skcipher_request_ctx(req); struct polyval_ctx *poly_ctx = &rctx->u.poly_ctx; u8 digest[POLYVAL_DIGEST_SIZE];
// U = UU ^ H(T || V) // or M = MM ^ H(T || N) polyval_import_blkaligned(poly_ctx, &tctx->poly_key, &rctx->hashed_tweak); hctr2_hash_message(req, rctx->bulk_part_dst, digest); crypto_xor(rctx->first_block, digest, BLOCKCIPHER_BLOCK_SIZE);
// Copy U (or M) into dst scatterlist scatterwalk_map_and_copy(rctx->first_block, req->dst, 0, BLOCKCIPHER_BLOCK_SIZE, 1); return 0;}
static void hctr2_xctr_done(void *data, int err){ struct skcipher_request *req = data;
if (!err) err = hctr2_finish(req);
skcipher_request_complete(req, err);}
static int hctr2_crypt(struct skcipher_request *req, bool enc){ struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); const struct hctr2_tfm_ctx *tctx = crypto_skcipher_ctx(tfm); struct hctr2_request_ctx *rctx = skcipher_request_ctx(req); u8 digest[POLYVAL_DIGEST_SIZE]; int bulk_len = req->cryptlen - BLOCKCIPHER_BLOCK_SIZE;
// Requests must be at least one block if (req->cryptlen < BLOCKCIPHER_BLOCK_SIZE) return -EINVAL;
// Copy M (or U) into a temporary buffer scatterwalk_map_and_copy(rctx->first_block, req->src, 0, BLOCKCIPHER_BLOCK_SIZE, 0);
// Create scatterlists for N and V rctx->bulk_part_src = scatterwalk_ffwd(rctx->sg_src, req->src, BLOCKCIPHER_BLOCK_SIZE); rctx->bulk_part_dst = scatterwalk_ffwd(rctx->sg_dst, req->dst, BLOCKCIPHER_BLOCK_SIZE);
// MM = M ^ H(T || N) // or UU = U ^ H(T || V) hctr2_hash_tweak(req); hctr2_hash_message(req, rctx->bulk_part_src, digest); crypto_xor(digest, rctx->first_block, BLOCKCIPHER_BLOCK_SIZE);
// UU = E(MM) // or MM = D(UU) if (enc) crypto_cipher_encrypt_one(tctx->blockcipher, rctx->first_block, digest); else crypto_cipher_decrypt_one(tctx->blockcipher, rctx->first_block, digest);
// S = MM ^ UU ^ L crypto_xor(digest, rctx->first_block, BLOCKCIPHER_BLOCK_SIZE); crypto_xor_cpy(rctx->xctr_iv, digest, tctx->L, BLOCKCIPHER_BLOCK_SIZE);
// V = XCTR(S, N) // or N = XCTR(S, V) skcipher_request_set_tfm(&rctx->u.xctr_req, tctx->xctr); skcipher_request_set_crypt(&rctx->u.xctr_req, rctx->bulk_part_src, rctx->bulk_part_dst, bulk_len, rctx->xctr_iv); skcipher_request_set_callback(&rctx->u.xctr_req, req->base.flags, hctr2_xctr_done, req); return crypto_skcipher_encrypt(&rctx->u.xctr_req) ?: hctr2_finish(req);}
static int hctr2_encrypt(struct skcipher_request *req){ return hctr2_crypt(req, true);}
static int hctr2_decrypt(struct skcipher_request *req){ return hctr2_crypt(req, false);}
static int hctr2_init_tfm(struct crypto_skcipher *tfm){ struct skcipher_instance *inst = skcipher_alg_instance(tfm); struct hctr2_instance_ctx *ictx = skcipher_instance_ctx(inst); struct hctr2_tfm_ctx *tctx = crypto_skcipher_ctx(tfm); struct crypto_skcipher *xctr; struct crypto_cipher *blockcipher; int err;
xctr = crypto_spawn_skcipher(&ictx->xctr_spawn); if (IS_ERR(xctr)) return PTR_ERR(xctr);
blockcipher = crypto_spawn_cipher(&ictx->blockcipher_spawn); if (IS_ERR(blockcipher)) { err = PTR_ERR(blockcipher); goto err_free_xctr; }
tctx->xctr = xctr; tctx->blockcipher = blockcipher;
BUILD_BUG_ON(offsetofend(struct hctr2_request_ctx, u) != sizeof(struct hctr2_request_ctx)); crypto_skcipher_set_reqsize( tfm, max(sizeof(struct hctr2_request_ctx), offsetofend(struct hctr2_request_ctx, u.xctr_req) + crypto_skcipher_reqsize(xctr))); return 0;
err_free_xctr: crypto_free_skcipher(xctr); return err;}
static void hctr2_exit_tfm(struct crypto_skcipher *tfm){ struct hctr2_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
crypto_free_cipher(tctx->blockcipher); crypto_free_skcipher(tctx->xctr);}
static void hctr2_free_instance(struct skcipher_instance *inst){ struct hctr2_instance_ctx *ictx = skcipher_instance_ctx(inst);
crypto_drop_cipher(&ictx->blockcipher_spawn); crypto_drop_skcipher(&ictx->xctr_spawn); kfree(inst);}
static int hctr2_create_common(struct crypto_template *tmpl, struct rtattr **tb, const char *xctr_name){ struct skcipher_alg_common *xctr_alg; u32 mask; struct skcipher_instance *inst; struct hctr2_instance_ctx *ictx; struct crypto_alg *blockcipher_alg; char blockcipher_name[CRYPTO_MAX_ALG_NAME]; int len; int err;
err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask); if (err) return err;
inst = kzalloc(sizeof(*inst) + sizeof(*ictx), GFP_KERNEL); if (!inst) return -ENOMEM; ictx = skcipher_instance_ctx(inst);
/* Stream cipher, xctr(block_cipher) */ err = crypto_grab_skcipher(&ictx->xctr_spawn, skcipher_crypto_instance(inst), xctr_name, 0, mask); if (err) goto err_free_inst; xctr_alg = crypto_spawn_skcipher_alg_common(&ictx->xctr_spawn);
err = -EINVAL; if (strncmp(xctr_alg->base.cra_name, "xctr(", 5)) goto err_free_inst; len = strscpy(blockcipher_name, xctr_alg->base.cra_name + 5, sizeof(blockcipher_name)); if (len < 1) goto err_free_inst; if (blockcipher_name[len - 1] != ')') goto err_free_inst; blockcipher_name[len - 1] = 0;
/* Block cipher, e.g. "aes" */ err = crypto_grab_cipher(&ictx->blockcipher_spawn, skcipher_crypto_instance(inst), blockcipher_name, 0, mask); if (err) goto err_free_inst; blockcipher_alg = crypto_spawn_cipher_alg(&ictx->blockcipher_spawn);
/* Require blocksize of 16 bytes */ err = -EINVAL; if (blockcipher_alg->cra_blocksize != BLOCKCIPHER_BLOCK_SIZE) goto err_free_inst;
/* Instance fields */
err = -ENAMETOOLONG; if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME, "hctr2(%s)", blockcipher_alg->cra_name) >= CRYPTO_MAX_ALG_NAME) goto err_free_inst; if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME, "hctr2_base(%s,polyval-lib)", xctr_alg->base.cra_driver_name) >= CRYPTO_MAX_ALG_NAME) goto err_free_inst;
inst->alg.base.cra_blocksize = BLOCKCIPHER_BLOCK_SIZE; inst->alg.base.cra_ctxsize = sizeof(struct hctr2_tfm_ctx); inst->alg.base.cra_alignmask = xctr_alg->base.cra_alignmask; inst->alg.base.cra_priority = (2 * xctr_alg->base.cra_priority + blockcipher_alg->cra_priority) / 3;
inst->alg.setkey = hctr2_setkey; inst->alg.encrypt = hctr2_encrypt; inst->alg.decrypt = hctr2_decrypt; inst->alg.init = hctr2_init_tfm; inst->alg.exit = hctr2_exit_tfm; inst->alg.min_keysize = xctr_alg->min_keysize; inst->alg.max_keysize = xctr_alg->max_keysize; inst->alg.ivsize = TWEAK_SIZE;
inst->free = hctr2_free_instance;
err = skcipher_register_instance(tmpl, inst); if (err) {err_free_inst: hctr2_free_instance(inst); } return err;}
static int hctr2_create_base(struct crypto_template *tmpl, struct rtattr **tb){ const char *xctr_name; const char *polyval_name;
xctr_name = crypto_attr_alg_name(tb[1]); if (IS_ERR(xctr_name)) return PTR_ERR(xctr_name);
polyval_name = crypto_attr_alg_name(tb[2]); if (IS_ERR(polyval_name)) return PTR_ERR(polyval_name); if (strcmp(polyval_name, "polyval") != 0 && strcmp(polyval_name, "polyval-lib") != 0) return -ENOENT;
return hctr2_create_common(tmpl, tb, xctr_name);}
static int hctr2_create(struct crypto_template *tmpl, struct rtattr **tb){ const char *blockcipher_name; char xctr_name[CRYPTO_MAX_ALG_NAME];
blockcipher_name = crypto_attr_alg_name(tb[1]); if (IS_ERR(blockcipher_name)) return PTR_ERR(blockcipher_name);
if (snprintf(xctr_name, CRYPTO_MAX_ALG_NAME, "xctr(%s)", blockcipher_name) >= CRYPTO_MAX_ALG_NAME) return -ENAMETOOLONG;
return hctr2_create_common(tmpl, tb, xctr_name);}
static struct crypto_template hctr2_tmpls[] = { { /* hctr2_base(xctr_name, polyval_name) */ .name = "hctr2_base", .create = hctr2_create_base, .module = THIS_MODULE, }, { /* hctr2(blockcipher_name) */ .name = "hctr2", .create = hctr2_create, .module = THIS_MODULE, }};
static int __init hctr2_module_init(void){ return crypto_register_templates(hctr2_tmpls, ARRAY_SIZE(hctr2_tmpls));}
static void __exit hctr2_module_exit(void){ return crypto_unregister_templates(hctr2_tmpls, ARRAY_SIZE(hctr2_tmpls));}
module_init(hctr2_module_init);module_exit(hctr2_module_exit);
MODULE_DESCRIPTION("HCTR2 length-preserving encryption mode");MODULE_LICENSE("GPL v2");MODULE_ALIAS_CRYPTO("hctr2");MODULE_IMPORT_NS("CRYPTO_INTERNAL");