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-rw-r--r--crypto/hctr2.c580
1 files changed, 580 insertions, 0 deletions
diff --git a/crypto/hctr2.c b/crypto/hctr2.c
new file mode 100644
index 0000000000..6f4c1884d0
--- /dev/null
+++ b/crypto/hctr2.c
@@ -0,0 +1,580 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * HCTR2 length-preserving encryption mode
+ *
+ * Copyright 2021 Google LLC
+ */
+
+
+/*
+ * 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/internal/cipher.h>
+#include <crypto/internal/hash.h>
+#include <crypto/internal/skcipher.h>
+#include <crypto/polyval.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 crypto_shash_spawn polyval_spawn;
+};
+
+struct hctr2_tfm_ctx {
+ struct crypto_cipher *blockcipher;
+ struct crypto_skcipher *xctr;
+ struct crypto_shash *polyval;
+ u8 L[BLOCKCIPHER_BLOCK_SIZE];
+ int hashed_tweak_offset;
+ /*
+ * This struct is allocated with extra space for two exported hash
+ * states. Since the hash state size is not known at compile-time, we
+ * can't add these to the struct directly.
+ *
+ * hashed_tweaklen_divisible;
+ * hashed_tweaklen_remainder;
+ */
+};
+
+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];
+ /*
+ * Sub-request sizes are unknown at compile-time, so they need to go
+ * after the members with known sizes.
+ */
+ union {
+ struct shash_desc hash_desc;
+ struct skcipher_request xctr_req;
+ } u;
+ /*
+ * This struct is allocated with extra space for one exported hash
+ * state. Since the hash state size is not known at compile-time, we
+ * can't add it to the struct directly.
+ *
+ * hashed_tweak;
+ */
+};
+
+static inline u8 *hctr2_hashed_tweaklen(const struct hctr2_tfm_ctx *tctx,
+ bool has_remainder)
+{
+ u8 *p = (u8 *)tctx + sizeof(*tctx);
+
+ if (has_remainder) /* For messages not a multiple of block length */
+ p += crypto_shash_statesize(tctx->polyval);
+ return p;
+}
+
+static inline u8 *hctr2_hashed_tweak(const struct hctr2_tfm_ctx *tctx,
+ struct hctr2_request_ctx *rctx)
+{
+ return (u8 *)rctx + tctx->hashed_tweak_offset;
+}
+
+/*
+ * 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 int hctr2_hash_tweaklen(struct hctr2_tfm_ctx *tctx, bool has_remainder)
+{
+ SHASH_DESC_ON_STACK(shash, tfm->polyval);
+ __le64 tweak_length_block[2];
+ int err;
+
+ shash->tfm = tctx->polyval;
+ memset(tweak_length_block, 0, sizeof(tweak_length_block));
+
+ tweak_length_block[0] = cpu_to_le64(TWEAK_SIZE * 8 * 2 + 2 + has_remainder);
+ err = crypto_shash_init(shash);
+ if (err)
+ return err;
+ err = crypto_shash_update(shash, (u8 *)tweak_length_block,
+ POLYVAL_BLOCK_SIZE);
+ if (err)
+ return err;
+ return crypto_shash_export(shash, hctr2_hashed_tweaklen(tctx, has_remainder));
+}
+
+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);
+
+ crypto_shash_clear_flags(tctx->polyval, CRYPTO_TFM_REQ_MASK);
+ crypto_shash_set_flags(tctx->polyval, crypto_skcipher_get_flags(tfm) &
+ CRYPTO_TFM_REQ_MASK);
+ err = crypto_shash_setkey(tctx->polyval, hbar, BLOCKCIPHER_BLOCK_SIZE);
+ if (err)
+ return err;
+ memzero_explicit(hbar, sizeof(hbar));
+
+ return hctr2_hash_tweaklen(tctx, true) ?: hctr2_hash_tweaklen(tctx, false);
+}
+
+static int 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 shash_desc *hash_desc = &rctx->u.hash_desc;
+ int err;
+ bool has_remainder = req->cryptlen % POLYVAL_BLOCK_SIZE;
+
+ hash_desc->tfm = tctx->polyval;
+ err = crypto_shash_import(hash_desc, hctr2_hashed_tweaklen(tctx, has_remainder));
+ if (err)
+ return err;
+ err = crypto_shash_update(hash_desc, req->iv, TWEAK_SIZE);
+ if (err)
+ return err;
+
+ // Store the hashed tweak, since we need it when computing both
+ // H(T || N) and H(T || V).
+ return crypto_shash_export(hash_desc, hctr2_hashed_tweak(tctx, rctx));
+}
+
+static int hctr2_hash_message(struct skcipher_request *req,
+ struct scatterlist *sgl,
+ u8 digest[POLYVAL_DIGEST_SIZE])
+{
+ static const u8 padding[BLOCKCIPHER_BLOCK_SIZE] = { 0x1 };
+ struct hctr2_request_ctx *rctx = skcipher_request_ctx(req);
+ struct shash_desc *hash_desc = &rctx->u.hash_desc;
+ const unsigned int bulk_len = req->cryptlen - BLOCKCIPHER_BLOCK_SIZE;
+ struct sg_mapping_iter miter;
+ unsigned int remainder = bulk_len % BLOCKCIPHER_BLOCK_SIZE;
+ int i;
+ int err = 0;
+ 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);
+ err = crypto_shash_update(hash_desc, miter.addr, n);
+ if (err)
+ break;
+ }
+ sg_miter_stop(&miter);
+
+ if (err)
+ return err;
+
+ if (remainder) {
+ err = crypto_shash_update(hash_desc, padding,
+ BLOCKCIPHER_BLOCK_SIZE - remainder);
+ if (err)
+ return err;
+ }
+ return crypto_shash_final(hash_desc, 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);
+ u8 digest[POLYVAL_DIGEST_SIZE];
+ struct shash_desc *hash_desc = &rctx->u.hash_desc;
+ int err;
+
+ // U = UU ^ H(T || V)
+ // or M = MM ^ H(T || N)
+ hash_desc->tfm = tctx->polyval;
+ err = crypto_shash_import(hash_desc, hctr2_hashed_tweak(tctx, rctx));
+ if (err)
+ return err;
+ err = hctr2_hash_message(req, rctx->bulk_part_dst, digest);
+ if (err)
+ return err;
+ 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;
+ int err;
+
+ // 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)
+ err = hctr2_hash_tweak(req);
+ if (err)
+ return err;
+ err = hctr2_hash_message(req, rctx->bulk_part_src, digest);
+ if (err)
+ return err;
+ 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;
+ struct crypto_shash *polyval;
+ unsigned int subreq_size;
+ 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;
+ }
+
+ polyval = crypto_spawn_shash(&ictx->polyval_spawn);
+ if (IS_ERR(polyval)) {
+ err = PTR_ERR(polyval);
+ goto err_free_blockcipher;
+ }
+
+ tctx->xctr = xctr;
+ tctx->blockcipher = blockcipher;
+ tctx->polyval = polyval;
+
+ BUILD_BUG_ON(offsetofend(struct hctr2_request_ctx, u) !=
+ sizeof(struct hctr2_request_ctx));
+ subreq_size = max(sizeof_field(struct hctr2_request_ctx, u.hash_desc) +
+ crypto_shash_descsize(polyval),
+ sizeof_field(struct hctr2_request_ctx, u.xctr_req) +
+ crypto_skcipher_reqsize(xctr));
+
+ tctx->hashed_tweak_offset = offsetof(struct hctr2_request_ctx, u) +
+ subreq_size;
+ crypto_skcipher_set_reqsize(tfm, tctx->hashed_tweak_offset +
+ crypto_shash_statesize(polyval));
+ return 0;
+
+err_free_blockcipher:
+ crypto_free_cipher(blockcipher);
+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);
+ crypto_free_shash(tctx->polyval);
+}
+
+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);
+ crypto_drop_shash(&ictx->polyval_spawn);
+ kfree(inst);
+}
+
+static int hctr2_create_common(struct crypto_template *tmpl,
+ struct rtattr **tb,
+ const char *xctr_name,
+ const char *polyval_name)
+{
+ u32 mask;
+ struct skcipher_instance *inst;
+ struct hctr2_instance_ctx *ictx;
+ struct skcipher_alg *xctr_alg;
+ struct crypto_alg *blockcipher_alg;
+ struct shash_alg *polyval_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(&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;
+
+ /* Polyval ε-∆U hash function */
+ err = crypto_grab_shash(&ictx->polyval_spawn,
+ skcipher_crypto_instance(inst),
+ polyval_name, 0, mask);
+ if (err)
+ goto err_free_inst;
+ polyval_alg = crypto_spawn_shash_alg(&ictx->polyval_spawn);
+
+ /* Ensure Polyval is being used */
+ err = -EINVAL;
+ if (strcmp(polyval_alg->base.cra_name, "polyval") != 0)
+ 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,%s)",
+ xctr_alg->base.cra_driver_name,
+ polyval_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) +
+ polyval_alg->statesize * 2;
+ inst->alg.base.cra_alignmask = xctr_alg->base.cra_alignmask |
+ polyval_alg->base.cra_alignmask;
+ /*
+ * The hash function is called twice, so it is weighted higher than the
+ * xctr and blockcipher.
+ */
+ inst->alg.base.cra_priority = (2 * xctr_alg->base.cra_priority +
+ 4 * polyval_alg->base.cra_priority +
+ blockcipher_alg->cra_priority) / 7;
+
+ 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 = crypto_skcipher_alg_min_keysize(xctr_alg);
+ inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(xctr_alg);
+ 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);
+
+ return hctr2_create_common(tmpl, tb, xctr_name, polyval_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, "polyval");
+}
+
+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));
+}
+
+subsys_initcall(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);
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