From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Sun, 6 Jan 2008 16:09:19 +1100
Subject: [crypto] chainiv: add chain IV generator
Message-id: E1JBNl9-0001AO-00@gondolin.me.apana.org.au
O-Subject: [PATCH 5/32] [CRYPTO] chainiv: Add chain IV generator
Bugzilla: 253051

[CRYPTO] chainiv: Add chain IV generator

The chain IV generator is the one we've been using in the IPsec stack.
It simply starts out with a random IV, then uses the last block of each
encrypted packet's cipher text as the IV for the next packet.

It can only be used by synchronous ciphers since we have to make sure
that we don't start the encryption of the next packet until the last
one has completed.

It does have the advantage of using very little CPU time since it doesn't
have to generate anything at all.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Acked-by: "David S. Miller" <davem@redhat.com>

diff --git a/crypto/Makefile b/crypto/Makefile
index d3d273c..655475d 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -13,6 +13,7 @@ obj-$(CONFIG_CRYPTO_ALGAPI) += crypto_algapi.o
 crypto_blkcipher-objs := ablkcipher.o
 crypto_blkcipher-objs += blkcipher.o
 obj-$(CONFIG_CRYPTO_BLKCIPHER) += crypto_blkcipher.o
+obj-$(CONFIG_CRYPTO_BLKCIPHER) += chainiv.o
 
 obj-$(CONFIG_CRYPTO_API) += crypto_api.o
 obj-$(CONFIG_CRYPTO_MANAGER) += cryptomgr.o
diff --git a/crypto/chainiv.c b/crypto/chainiv.c
new file mode 100644
index 0000000..a1d545a
--- /dev/null
+++ b/crypto/chainiv.c
@@ -0,0 +1,329 @@
+/*
+ * chainiv: Chain IV Generator
+ *
+ * Generate IVs simply be using the last block of the previous encryption.
+ * This is mainly useful for CBC with a synchronous algorithm.
+ *
+ * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
+ *
+ * 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/internal/skcipher.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/random.h>
+#include <linux/spinlock.h>
+#include <linux/string.h>
+#include <linux/workqueue.h>
+
+enum {
+	CHAINIV_STATE_INUSE = 0,
+};
+
+struct chainiv_ctx {
+	spinlock_t lock;
+	char iv[];
+};
+
+struct async_chainiv_ctx {
+	unsigned long state;
+
+	spinlock_t lock;
+	int err;
+
+	struct crypto_queue queue;
+	struct work_struct postponed;
+
+	char iv[];
+};
+
+static int chainiv_givencrypt(struct skcipher_givcrypt_request *req)
+{
+	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
+	struct chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
+	struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req);
+	unsigned int ivsize;
+	int err;
+
+	ablkcipher_request_set_tfm(subreq, skcipher_geniv_cipher(geniv));
+	ablkcipher_request_set_callback(subreq, req->creq.base.flags &
+						~CRYPTO_TFM_REQ_MAY_SLEEP,
+					req->creq.base.complete,
+					req->creq.base.data);
+	ablkcipher_request_set_crypt(subreq, req->creq.src, req->creq.dst,
+				     req->creq.nbytes, req->creq.info);
+
+	spin_lock_bh(&ctx->lock);
+
+	ivsize = crypto_ablkcipher_ivsize(geniv);
+
+	memcpy(req->giv, ctx->iv, ivsize);
+	memcpy(subreq->info, ctx->iv, ivsize);
+
+	err = crypto_ablkcipher_encrypt(subreq);
+	if (err)
+		goto unlock;
+
+	memcpy(ctx->iv, subreq->info, ivsize);
+
+unlock:
+	spin_unlock_bh(&ctx->lock);
+
+	return err;
+}
+
+static int chainiv_givencrypt_first(struct skcipher_givcrypt_request *req)
+{
+	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
+	struct chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
+
+	spin_lock_bh(&ctx->lock);
+	if (crypto_ablkcipher_crt(geniv)->givencrypt !=
+	    chainiv_givencrypt_first)
+		goto unlock;
+
+	crypto_ablkcipher_crt(geniv)->givencrypt = chainiv_givencrypt;
+	get_random_bytes(ctx->iv, crypto_ablkcipher_ivsize(geniv));
+
+unlock:
+	spin_unlock_bh(&ctx->lock);
+
+	return chainiv_givencrypt(req);
+}
+
+static int chainiv_init_common(struct ncrypto_tfm *tfm)
+{
+	tfm->crt_ablkcipher.reqsize = sizeof(struct ablkcipher_request);
+
+	return skcipher_geniv_init(tfm);
+}
+
+static int chainiv_init(struct ncrypto_tfm *tfm)
+{
+	struct chainiv_ctx *ctx = ncrypto_tfm_ctx(tfm);
+
+	spin_lock_init(&ctx->lock);
+
+	return chainiv_init_common(tfm);
+}
+
+static int async_chainiv_schedule_work(struct async_chainiv_ctx *ctx)
+{
+	int queued;
+
+	if (!ctx->queue.qlen) {
+		smp_mb__before_clear_bit();
+		clear_bit(CHAINIV_STATE_INUSE, &ctx->state);
+
+		if (!ctx->queue.qlen ||
+		    test_and_set_bit(CHAINIV_STATE_INUSE, &ctx->state))
+			goto out;
+	}
+
+	queued = schedule_work(&ctx->postponed);
+	BUG_ON(!queued);
+
+out:
+	return ctx->err;
+}
+
+static int async_chainiv_postpone_request(struct skcipher_givcrypt_request *req)
+{
+	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
+	struct async_chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
+	int err;
+
+	spin_lock_bh(&ctx->lock);
+	err = skcipher_enqueue_givcrypt(&ctx->queue, req);
+	spin_unlock_bh(&ctx->lock);
+
+	if (test_and_set_bit(CHAINIV_STATE_INUSE, &ctx->state))
+		return err;
+
+	ctx->err = err;
+	return async_chainiv_schedule_work(ctx);
+}
+
+static int async_chainiv_givencrypt_tail(struct skcipher_givcrypt_request *req)
+{
+	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
+	struct async_chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
+	struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req);
+	unsigned int ivsize = crypto_ablkcipher_ivsize(geniv);
+
+	memcpy(req->giv, ctx->iv, ivsize);
+	memcpy(subreq->info, ctx->iv, ivsize);
+
+	ctx->err = crypto_ablkcipher_encrypt(subreq);
+	if (ctx->err)
+		goto out;
+
+	memcpy(ctx->iv, subreq->info, ivsize);
+
+out:
+	return async_chainiv_schedule_work(ctx);
+}
+
+static int async_chainiv_givencrypt(struct skcipher_givcrypt_request *req)
+{
+	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
+	struct async_chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
+	struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req);
+
+	ablkcipher_request_set_tfm(subreq, skcipher_geniv_cipher(geniv));
+	ablkcipher_request_set_callback(subreq, req->creq.base.flags,
+					req->creq.base.complete,
+					req->creq.base.data);
+	ablkcipher_request_set_crypt(subreq, req->creq.src, req->creq.dst,
+				     req->creq.nbytes, req->creq.info);
+
+	if (test_and_set_bit(CHAINIV_STATE_INUSE, &ctx->state))
+		goto postpone;
+
+	if (ctx->queue.qlen) {
+		clear_bit(CHAINIV_STATE_INUSE, &ctx->state);
+		goto postpone;
+	}
+
+	return async_chainiv_givencrypt_tail(req);
+
+postpone:
+	return async_chainiv_postpone_request(req);
+}
+
+static int async_chainiv_givencrypt_first(struct skcipher_givcrypt_request *req)
+{
+	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
+	struct async_chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
+
+	if (test_and_set_bit(CHAINIV_STATE_INUSE, &ctx->state))
+		goto out;
+
+	if (crypto_ablkcipher_crt(geniv)->givencrypt !=
+	    async_chainiv_givencrypt_first)
+		goto unlock;
+
+	crypto_ablkcipher_crt(geniv)->givencrypt = async_chainiv_givencrypt;
+	get_random_bytes(ctx->iv, crypto_ablkcipher_ivsize(geniv));
+
+unlock:
+	clear_bit(CHAINIV_STATE_INUSE, &ctx->state);
+
+out:
+	return async_chainiv_givencrypt(req);
+}
+
+static void async_chainiv_do_postponed(void *data)
+{
+	struct async_chainiv_ctx *ctx = data;
+	struct skcipher_givcrypt_request *req;
+	struct ablkcipher_request *subreq;
+
+	/* Only handle one request at a time to avoid hogging keventd. */
+	spin_lock_bh(&ctx->lock);
+	req = skcipher_dequeue_givcrypt(&ctx->queue);
+	spin_unlock_bh(&ctx->lock);
+
+	if (!req) {
+		async_chainiv_schedule_work(ctx);
+		return;
+	}
+
+	subreq = skcipher_givcrypt_reqctx(req);
+	subreq->base.flags |= CRYPTO_TFM_REQ_MAY_SLEEP;
+
+	async_chainiv_givencrypt_tail(req);
+}
+
+static int async_chainiv_init(struct ncrypto_tfm *tfm)
+{
+	struct async_chainiv_ctx *ctx = ncrypto_tfm_ctx(tfm);
+
+	spin_lock_init(&ctx->lock);
+
+	crypto_init_queue(&ctx->queue, 100);
+	INIT_WORK(&ctx->postponed, async_chainiv_do_postponed, ctx);
+
+	return chainiv_init_common(tfm);
+}
+
+static void async_chainiv_exit(struct ncrypto_tfm *tfm)
+{
+	struct async_chainiv_ctx *ctx = ncrypto_tfm_ctx(tfm);
+
+	BUG_ON(test_bit(CHAINIV_STATE_INUSE, &ctx->state) || ctx->queue.qlen);
+
+	skcipher_geniv_exit(tfm);
+}
+
+static struct crypto_template chainiv_tmpl;
+
+static struct crypto_instance *chainiv_alloc(struct rtattr **tb)
+{
+	struct crypto_attr_type *algt;
+	struct crypto_instance *inst;
+	int err;
+
+	algt = crypto_get_attr_type(tb);
+	err = PTR_ERR(algt);
+	if (IS_ERR(algt))
+		return ERR_PTR(err);
+
+	inst = skcipher_geniv_alloc(&chainiv_tmpl, tb, 0, 0);
+	if (IS_ERR(inst))
+		goto out;
+
+	inst->alg.cra_ablkcipher.givencrypt = chainiv_givencrypt_first;
+
+	inst->alg.cra_init = chainiv_init;
+	inst->alg.cra_exit = skcipher_geniv_exit;
+
+	inst->alg.cra_ctxsize = sizeof(struct chainiv_ctx);
+
+	if (!crypto_requires_sync(algt->type, algt->mask)) {
+		inst->alg.cra_flags |= NCRYPTO_ALG_ASYNC;
+
+		inst->alg.cra_ablkcipher.givencrypt =
+			async_chainiv_givencrypt_first;
+
+		inst->alg.cra_init = async_chainiv_init;
+		inst->alg.cra_exit = async_chainiv_exit;
+
+		inst->alg.cra_ctxsize = sizeof(struct async_chainiv_ctx);
+	}
+
+	inst->alg.cra_ctxsize += inst->alg.cra_ablkcipher.ivsize;
+
+out:
+	return inst;
+}
+
+static struct crypto_template chainiv_tmpl = {
+	.name = "chainiv",
+	.alloc = chainiv_alloc,
+	.free = skcipher_geniv_free,
+	.module = THIS_MODULE,
+};
+
+static int __init chainiv_module_init(void)
+{
+	return crypto_register_template(&chainiv_tmpl);
+}
+
+static void __exit chainiv_module_exit(void)
+{
+	crypto_unregister_template(&chainiv_tmpl);
+}
+
+module_init(chainiv_module_init);
+module_exit(chainiv_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Chain IV Generator");