1 files changed, 139 insertions, 0 deletions
diff --git a/crypto/chainiv.c b/crypto/chainiv.c
new file mode 100644
index 0000000..38868d1
--- /dev/null
+++ b/crypto/chainiv.c
@@ -0,0 +1,139 @@
+/*
+ * 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/module.h>
+#include <linux/random.h>
+#include <linux/spinlock.h>
+#include <linux/string.h>
+
+struct chainiv_ctx {
+	spinlock_t lock;
+	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(struct crypto_tfm *tfm)
+{
+	struct crypto_ablkcipher *geniv = __crypto_ablkcipher_cast(tfm);
+	struct chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
+
+	spin_lock_init(&ctx->lock);
+
+	tfm->crt_ablkcipher.reqsize = sizeof(struct ablkcipher_request);
+
+	return skcipher_geniv_init(tfm);
+}
+
+static struct crypto_template chainiv_tmpl;
+
+static struct crypto_instance *chainiv_alloc(struct rtattr **tb)
+{
+	struct crypto_instance *inst;
+
+	inst = skcipher_geniv_alloc(&chainiv_tmpl, tb, 0,
+				    CRYPTO_ALG_ASYNC);
+	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) +
+				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");