[CRYPTO] seqiv: Add Sequence Number IV Generator

This generator generates an IV based on a sequence number by xoring it
with a salt.  This algorithm is mainly useful for CTR and similar modes.

This patch also sets it as the default IV generator for ctr.

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

1 files changed, 186 insertions, 0 deletions

diff --git a/crypto/seqiv.c b/crypto/seqiv.c
new file mode 100644
index 000000000000..9c2d80d77a0a
--- /dev/null
+++ b/crypto/seqiv.c
@@ -0,0 +1,186 @@
+/*
+ * seqiv: Sequence Number IV Generator
+ *
+ * This generator generates an IV based on a sequence number by xoring it
+ * with a salt.  This algorithm is mainly useful for CTR and similar modes.
+ *
+ * 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>
+
+struct seqiv_ctx {
+        spinlock_t lock;
+        u8 salt[] __attribute__ ((aligned(__alignof__(u32))));
+};
+
+static void seqiv_complete2(struct skcipher_givcrypt_request *req, int err)
+{
+        struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req);
+        struct crypto_ablkcipher *geniv;
+
+        if (err == -EINPROGRESS)
+                return;
+
+        if (err)
+                goto out;
+
+        geniv = skcipher_givcrypt_reqtfm(req);
+        memcpy(req->creq.info, subreq->info, crypto_ablkcipher_ivsize(geniv));
+
+out:
+        kfree(subreq->info);
+}
+
+static void seqiv_complete(struct crypto_async_request *base, int err)
+{
+        struct skcipher_givcrypt_request *req = base->data;
+
+        seqiv_complete2(req, err);
+        skcipher_givcrypt_complete(req, err);
+}
+
+static int seqiv_givencrypt(struct skcipher_givcrypt_request *req)
+{
+        struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
+        struct seqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
+        struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req);
+        crypto_completion_t complete;
+        void *data;
+        u8 *info;
+        __be64 seq;
+        unsigned int ivsize;
+        unsigned int len;
+        int err;
+
+        ablkcipher_request_set_tfm(subreq, skcipher_geniv_cipher(geniv));
+
+        complete = req->creq.base.complete;
+        data = req->creq.base.data;
+        info = req->creq.info;
+
+        ivsize = crypto_ablkcipher_ivsize(geniv);
+
+        if (unlikely(!IS_ALIGNED((unsigned long)info,
+                                 crypto_ablkcipher_alignmask(geniv) + 1))) {
+                info = kmalloc(ivsize, req->creq.base.flags &
+                                       CRYPTO_TFM_REQ_MAY_SLEEP ? GFP_KERNEL:
+                                                                  GFP_ATOMIC);
+                if (!info)
+                        return -ENOMEM;
+
+                complete = seqiv_complete;
+                data = req;
+        }
+
+        ablkcipher_request_set_callback(subreq, req->creq.base.flags, complete,
+                                        data);
+        ablkcipher_request_set_crypt(subreq, req->creq.src, req->creq.dst,
+                                     req->creq.nbytes, info);
+
+        len = ivsize;
+        if (ivsize > sizeof(u64)) {
+                memset(info, 0, ivsize - sizeof(u64));
+                len = sizeof(u64);
+        }
+        seq = cpu_to_be64(req->seq);
+        memcpy(info + ivsize - len, &seq, len);
+        crypto_xor(info, ctx->salt, ivsize);
+
+        memcpy(req->giv, info, ivsize);
+
+        err = crypto_ablkcipher_encrypt(subreq);
+        if (unlikely(info != req->creq.info))
+                seqiv_complete2(req, err);
+        return err;
+}
+
+static int seqiv_givencrypt_first(struct skcipher_givcrypt_request *req)
+{
+        struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
+        struct seqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
+
+        spin_lock_bh(&ctx->lock);
+        if (crypto_ablkcipher_crt(geniv)->givencrypt != seqiv_givencrypt_first)
+                goto unlock;
+
+        crypto_ablkcipher_crt(geniv)->givencrypt = seqiv_givencrypt;
+        get_random_bytes(ctx->salt, crypto_ablkcipher_ivsize(geniv));
+
+unlock:
+        spin_unlock_bh(&ctx->lock);
+
+        return seqiv_givencrypt(req);
+}
+
+static int seqiv_init(struct crypto_tfm *tfm)
+{
+        struct crypto_ablkcipher *geniv = __crypto_ablkcipher_cast(tfm);
+        struct seqiv_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 seqiv_tmpl;
+
+static struct crypto_instance *seqiv_alloc(struct rtattr **tb)
+{
+        struct crypto_instance *inst;
+
+        inst = skcipher_geniv_alloc(&seqiv_tmpl, tb, 0, 0);
+        if (IS_ERR(inst))
+                goto out;
+
+        inst->alg.cra_ablkcipher.givencrypt = seqiv_givencrypt_first;
+
+        inst->alg.cra_init = seqiv_init;
+        inst->alg.cra_exit = skcipher_geniv_exit;
+
+        inst->alg.cra_alignmask |= __alignof__(u32) - 1;
+
+        inst->alg.cra_ctxsize = sizeof(struct seqiv_ctx);
+        inst->alg.cra_ctxsize += inst->alg.cra_ablkcipher.ivsize;
+
+out:
+        return inst;
+}
+
+static struct crypto_template seqiv_tmpl = {
+        .name = "seqiv",
+        .alloc = seqiv_alloc,
+        .free = skcipher_geniv_free,
+        .module = THIS_MODULE,
+};
+
+static int __init seqiv_module_init(void)
+{
+        return crypto_register_template(&seqiv_tmpl);
+}
+
+static void __exit seqiv_module_exit(void)
+{
+        crypto_unregister_template(&seqiv_tmpl);
+}
+
+module_init(seqiv_module_init);
+module_exit(seqiv_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Sequence Number IV Generator");