265 lines
6.3 KiB
C
265 lines
6.3 KiB
C
/*
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* eseqiv: Encrypted Sequence Number IV Generator
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*
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* This generator generates an IV based on a sequence number by xoring it
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* with a salt and then encrypting it with the same key as used to encrypt
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* the plain text. This algorithm requires that the block size be equal
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* to the IV size. It is mainly useful for CBC.
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*
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* Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the Free
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* Software Foundation; either version 2 of the License, or (at your option)
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* any later version.
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*
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*/
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#include <crypto/internal/skcipher.h>
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#include <crypto/scatterwalk.h>
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#include <linux/err.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/module.h>
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#include <linux/random.h>
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#include <linux/scatterlist.h>
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#include <linux/spinlock.h>
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#include <linux/string.h>
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struct eseqiv_request_ctx {
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struct scatterlist src[2];
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struct scatterlist dst[2];
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char tail[];
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};
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struct eseqiv_ctx {
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spinlock_t lock;
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unsigned int reqoff;
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char salt[];
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};
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static void eseqiv_complete2(struct skcipher_givcrypt_request *req)
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{
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struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
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struct eseqiv_request_ctx *reqctx = skcipher_givcrypt_reqctx(req);
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memcpy(req->giv, PTR_ALIGN((u8 *)reqctx->tail,
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crypto_ablkcipher_alignmask(geniv) + 1),
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crypto_ablkcipher_ivsize(geniv));
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}
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static void eseqiv_complete(struct crypto_async_request *base, int err)
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{
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struct skcipher_givcrypt_request *req = base->data;
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if (err)
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goto out;
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eseqiv_complete2(req);
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out:
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skcipher_givcrypt_complete(req, err);
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}
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static void eseqiv_chain(struct scatterlist *head, struct scatterlist *sg,
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int chain)
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{
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if (chain) {
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head->length += sg->length;
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sg = scatterwalk_sg_next(sg);
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}
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if (sg)
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scatterwalk_sg_chain(head, 2, sg);
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else
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sg_mark_end(head);
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}
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static int eseqiv_givencrypt(struct skcipher_givcrypt_request *req)
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{
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struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
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struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
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struct eseqiv_request_ctx *reqctx = skcipher_givcrypt_reqctx(req);
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struct ablkcipher_request *subreq;
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crypto_completion_t complete;
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void *data;
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struct scatterlist *osrc, *odst;
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struct scatterlist *dst;
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struct page *srcp;
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struct page *dstp;
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u8 *giv;
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u8 *vsrc;
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u8 *vdst;
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__be64 seq;
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unsigned int ivsize;
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unsigned int len;
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int err;
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subreq = (void *)(reqctx->tail + ctx->reqoff);
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ablkcipher_request_set_tfm(subreq, skcipher_geniv_cipher(geniv));
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giv = req->giv;
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complete = req->creq.base.complete;
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data = req->creq.base.data;
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osrc = req->creq.src;
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odst = req->creq.dst;
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srcp = sg_page(osrc);
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dstp = sg_page(odst);
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vsrc = PageHighMem(srcp) ? NULL : page_address(srcp) + osrc->offset;
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vdst = PageHighMem(dstp) ? NULL : page_address(dstp) + odst->offset;
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ivsize = crypto_ablkcipher_ivsize(geniv);
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if (vsrc != giv + ivsize && vdst != giv + ivsize) {
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giv = PTR_ALIGN((u8 *)reqctx->tail,
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crypto_ablkcipher_alignmask(geniv) + 1);
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complete = eseqiv_complete;
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data = req;
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}
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ablkcipher_request_set_callback(subreq, req->creq.base.flags, complete,
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data);
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sg_init_table(reqctx->src, 2);
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sg_set_buf(reqctx->src, giv, ivsize);
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eseqiv_chain(reqctx->src, osrc, vsrc == giv + ivsize);
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dst = reqctx->src;
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if (osrc != odst) {
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sg_init_table(reqctx->dst, 2);
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sg_set_buf(reqctx->dst, giv, ivsize);
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eseqiv_chain(reqctx->dst, odst, vdst == giv + ivsize);
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dst = reqctx->dst;
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}
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ablkcipher_request_set_crypt(subreq, reqctx->src, dst,
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req->creq.nbytes, req->creq.info);
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memcpy(req->creq.info, ctx->salt, ivsize);
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len = ivsize;
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if (ivsize > sizeof(u64)) {
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memset(req->giv, 0, ivsize - sizeof(u64));
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len = sizeof(u64);
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}
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seq = cpu_to_be64(req->seq);
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memcpy(req->giv + ivsize - len, &seq, len);
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err = crypto_ablkcipher_encrypt(subreq);
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if (err)
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goto out;
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eseqiv_complete2(req);
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out:
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return err;
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}
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static int eseqiv_givencrypt_first(struct skcipher_givcrypt_request *req)
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{
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struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
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struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
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spin_lock_bh(&ctx->lock);
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if (crypto_ablkcipher_crt(geniv)->givencrypt != eseqiv_givencrypt_first)
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goto unlock;
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crypto_ablkcipher_crt(geniv)->givencrypt = eseqiv_givencrypt;
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get_random_bytes(ctx->salt, crypto_ablkcipher_ivsize(geniv));
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unlock:
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spin_unlock_bh(&ctx->lock);
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return eseqiv_givencrypt(req);
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}
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static int eseqiv_init(struct crypto_tfm *tfm)
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{
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struct crypto_ablkcipher *geniv = __crypto_ablkcipher_cast(tfm);
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struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
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unsigned long alignmask;
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unsigned int reqsize;
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spin_lock_init(&ctx->lock);
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alignmask = crypto_tfm_ctx_alignment() - 1;
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reqsize = sizeof(struct eseqiv_request_ctx);
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if (alignmask & reqsize) {
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alignmask &= reqsize;
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alignmask--;
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}
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alignmask = ~alignmask;
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alignmask &= crypto_ablkcipher_alignmask(geniv);
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reqsize += alignmask;
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reqsize += crypto_ablkcipher_ivsize(geniv);
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reqsize = ALIGN(reqsize, crypto_tfm_ctx_alignment());
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ctx->reqoff = reqsize - sizeof(struct eseqiv_request_ctx);
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tfm->crt_ablkcipher.reqsize = reqsize +
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sizeof(struct ablkcipher_request);
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return skcipher_geniv_init(tfm);
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}
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static struct crypto_template eseqiv_tmpl;
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static struct crypto_instance *eseqiv_alloc(struct rtattr **tb)
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{
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struct crypto_instance *inst;
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int err;
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inst = skcipher_geniv_alloc(&eseqiv_tmpl, tb, 0, 0);
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if (IS_ERR(inst))
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goto out;
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err = -EINVAL;
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if (inst->alg.cra_ablkcipher.ivsize != inst->alg.cra_blocksize)
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goto free_inst;
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inst->alg.cra_ablkcipher.givencrypt = eseqiv_givencrypt_first;
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inst->alg.cra_init = eseqiv_init;
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inst->alg.cra_exit = skcipher_geniv_exit;
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inst->alg.cra_ctxsize = sizeof(struct eseqiv_ctx);
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inst->alg.cra_ctxsize += inst->alg.cra_ablkcipher.ivsize;
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out:
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return inst;
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free_inst:
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skcipher_geniv_free(inst);
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inst = ERR_PTR(err);
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goto out;
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}
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static struct crypto_template eseqiv_tmpl = {
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.name = "eseqiv",
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.alloc = eseqiv_alloc,
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.free = skcipher_geniv_free,
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.module = THIS_MODULE,
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};
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static int __init eseqiv_module_init(void)
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{
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return crypto_register_template(&eseqiv_tmpl);
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}
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static void __exit eseqiv_module_exit(void)
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{
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crypto_unregister_template(&eseqiv_tmpl);
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}
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module_init(eseqiv_module_init);
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module_exit(eseqiv_module_exit);
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("Encrypted Sequence Number IV Generator");
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