370 lines
8.9 KiB
C
370 lines
8.9 KiB
C
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/*
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* CTR: Counter mode
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*
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* (C) Copyright IBM Corp. 2007 - Joy Latten <latten@us.ibm.com>
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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/algapi.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/module.h>
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#include <linux/random.h>
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#include <linux/scatterlist.h>
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#include <linux/slab.h>
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struct ctr_instance_ctx {
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struct crypto_spawn alg;
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unsigned int noncesize;
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unsigned int ivsize;
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};
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struct crypto_ctr_ctx {
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struct crypto_cipher *child;
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u8 *nonce;
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};
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static inline void __ctr_inc_byte(u8 *a, unsigned int size)
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{
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u8 *b = (a + size);
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u8 c;
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for (; size; size--) {
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c = *--b + 1;
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*b = c;
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if (c)
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break;
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}
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}
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static void ctr_inc_quad(u8 *a, unsigned int size)
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{
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__be32 *b = (__be32 *)(a + size);
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u32 c;
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for (; size >= 4; size -=4) {
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c = be32_to_cpu(*--b) + 1;
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*b = cpu_to_be32(c);
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if (c)
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return;
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}
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__ctr_inc_byte(a, size);
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}
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static void xor_byte(u8 *a, const u8 *b, unsigned int bs)
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{
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for (; bs; bs--)
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*a++ ^= *b++;
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}
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static void xor_quad(u8 *dst, const u8 *src, unsigned int bs)
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{
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u32 *a = (u32 *)dst;
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u32 *b = (u32 *)src;
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for (; bs >= 4; bs -= 4)
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*a++ ^= *b++;
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xor_byte((u8 *)a, (u8 *)b, bs);
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}
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static int crypto_ctr_setkey(struct crypto_tfm *parent, const u8 *key,
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unsigned int keylen)
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{
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struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(parent);
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struct crypto_cipher *child = ctx->child;
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struct ctr_instance_ctx *ictx =
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crypto_instance_ctx(crypto_tfm_alg_instance(parent));
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unsigned int noncelen = ictx->noncesize;
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int err = 0;
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/* the nonce is stored in bytes at end of key */
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if (keylen < noncelen)
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return -EINVAL;
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memcpy(ctx->nonce, key + (keylen - noncelen), noncelen);
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keylen -= noncelen;
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crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
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crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
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CRYPTO_TFM_REQ_MASK);
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err = crypto_cipher_setkey(child, key, keylen);
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crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
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CRYPTO_TFM_RES_MASK);
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return err;
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}
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static int crypto_ctr_crypt_segment(struct blkcipher_walk *walk,
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struct crypto_cipher *tfm, u8 *ctrblk,
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unsigned int countersize)
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{
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void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
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crypto_cipher_alg(tfm)->cia_encrypt;
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unsigned int bsize = crypto_cipher_blocksize(tfm);
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unsigned long alignmask = crypto_cipher_alignmask(tfm);
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u8 ks[bsize + alignmask];
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u8 *keystream = (u8 *)ALIGN((unsigned long)ks, alignmask + 1);
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u8 *src = walk->src.virt.addr;
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u8 *dst = walk->dst.virt.addr;
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unsigned int nbytes = walk->nbytes;
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do {
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/* create keystream */
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fn(crypto_cipher_tfm(tfm), keystream, ctrblk);
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xor_quad(keystream, src, min(nbytes, bsize));
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/* copy result into dst */
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memcpy(dst, keystream, min(nbytes, bsize));
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/* increment counter in counterblock */
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ctr_inc_quad(ctrblk + (bsize - countersize), countersize);
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if (nbytes < bsize)
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break;
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src += bsize;
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dst += bsize;
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nbytes -= bsize;
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} while (nbytes);
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return 0;
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}
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static int crypto_ctr_crypt_inplace(struct blkcipher_walk *walk,
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struct crypto_cipher *tfm, u8 *ctrblk,
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unsigned int countersize)
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{
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void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
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crypto_cipher_alg(tfm)->cia_encrypt;
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unsigned int bsize = crypto_cipher_blocksize(tfm);
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unsigned long alignmask = crypto_cipher_alignmask(tfm);
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unsigned int nbytes = walk->nbytes;
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u8 *src = walk->src.virt.addr;
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u8 ks[bsize + alignmask];
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u8 *keystream = (u8 *)ALIGN((unsigned long)ks, alignmask + 1);
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do {
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/* create keystream */
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fn(crypto_cipher_tfm(tfm), keystream, ctrblk);
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xor_quad(src, keystream, min(nbytes, bsize));
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/* increment counter in counterblock */
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ctr_inc_quad(ctrblk + (bsize - countersize), countersize);
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if (nbytes < bsize)
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break;
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src += bsize;
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nbytes -= bsize;
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} while (nbytes);
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return 0;
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}
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static int crypto_ctr_crypt(struct blkcipher_desc *desc,
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struct scatterlist *dst, struct scatterlist *src,
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unsigned int nbytes)
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{
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struct blkcipher_walk walk;
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struct crypto_blkcipher *tfm = desc->tfm;
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struct crypto_ctr_ctx *ctx = crypto_blkcipher_ctx(tfm);
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struct crypto_cipher *child = ctx->child;
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unsigned int bsize = crypto_cipher_blocksize(child);
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struct ctr_instance_ctx *ictx =
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crypto_instance_ctx(crypto_tfm_alg_instance(&tfm->base));
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unsigned long alignmask = crypto_cipher_alignmask(child);
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u8 cblk[bsize + alignmask];
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u8 *counterblk = (u8 *)ALIGN((unsigned long)cblk, alignmask + 1);
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unsigned int countersize;
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int err;
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blkcipher_walk_init(&walk, dst, src, nbytes);
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err = blkcipher_walk_virt_block(desc, &walk, bsize);
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/* set up counter block */
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memset(counterblk, 0 , bsize);
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memcpy(counterblk, ctx->nonce, ictx->noncesize);
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memcpy(counterblk + ictx->noncesize, walk.iv, ictx->ivsize);
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/* initialize counter portion of counter block */
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countersize = bsize - ictx->noncesize - ictx->ivsize;
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ctr_inc_quad(counterblk + (bsize - countersize), countersize);
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while (walk.nbytes) {
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if (walk.src.virt.addr == walk.dst.virt.addr)
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nbytes = crypto_ctr_crypt_inplace(&walk, child,
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counterblk,
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countersize);
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else
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nbytes = crypto_ctr_crypt_segment(&walk, child,
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counterblk,
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countersize);
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err = blkcipher_walk_done(desc, &walk, nbytes);
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}
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return err;
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}
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static int crypto_ctr_init_tfm(struct crypto_tfm *tfm)
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{
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struct crypto_instance *inst = (void *)tfm->__crt_alg;
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struct ctr_instance_ctx *ictx = crypto_instance_ctx(inst);
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struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);
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struct crypto_cipher *cipher;
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ctx->nonce = kzalloc(ictx->noncesize, GFP_KERNEL);
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if (!ctx->nonce)
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return -ENOMEM;
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cipher = crypto_spawn_cipher(&ictx->alg);
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if (IS_ERR(cipher))
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return PTR_ERR(cipher);
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ctx->child = cipher;
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return 0;
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}
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static void crypto_ctr_exit_tfm(struct crypto_tfm *tfm)
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{
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struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);
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kfree(ctx->nonce);
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crypto_free_cipher(ctx->child);
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}
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static struct crypto_instance *crypto_ctr_alloc(struct rtattr **tb)
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{
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struct crypto_instance *inst;
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struct crypto_alg *alg;
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struct ctr_instance_ctx *ictx;
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unsigned int noncesize;
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unsigned int ivsize;
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int err;
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err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
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if (err)
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return ERR_PTR(err);
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alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
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CRYPTO_ALG_TYPE_MASK);
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if (IS_ERR(alg))
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return ERR_PTR(PTR_ERR(alg));
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err = crypto_attr_u32(tb[2], &noncesize);
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if (err)
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goto out_put_alg;
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err = crypto_attr_u32(tb[3], &ivsize);
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if (err)
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goto out_put_alg;
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/* verify size of nonce + iv + counter */
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err = -EINVAL;
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if ((noncesize + ivsize) >= alg->cra_blocksize)
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goto out_put_alg;
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inst = kzalloc(sizeof(*inst) + sizeof(*ictx), GFP_KERNEL);
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err = -ENOMEM;
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if (!inst)
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goto out_put_alg;
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err = -ENAMETOOLONG;
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if (snprintf(inst->alg.cra_name, CRYPTO_MAX_ALG_NAME,
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"ctr(%s,%u,%u)", alg->cra_name, noncesize,
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ivsize) >= CRYPTO_MAX_ALG_NAME) {
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goto err_free_inst;
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}
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if (snprintf(inst->alg.cra_driver_name, CRYPTO_MAX_ALG_NAME,
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"ctr(%s,%u,%u)", alg->cra_driver_name, noncesize,
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ivsize) >= CRYPTO_MAX_ALG_NAME) {
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goto err_free_inst;
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}
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ictx = crypto_instance_ctx(inst);
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ictx->noncesize = noncesize;
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ictx->ivsize = ivsize;
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err = crypto_init_spawn(&ictx->alg, alg, inst,
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CRYPTO_ALG_TYPE_MASK | CRYPTO_ALG_ASYNC);
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if (err)
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goto err_free_inst;
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err = 0;
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inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
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inst->alg.cra_priority = alg->cra_priority;
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inst->alg.cra_blocksize = 1;
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inst->alg.cra_alignmask = 3;
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inst->alg.cra_type = &crypto_blkcipher_type;
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inst->alg.cra_blkcipher.ivsize = ivsize;
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inst->alg.cra_blkcipher.min_keysize = alg->cra_cipher.cia_min_keysize
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+ noncesize;
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inst->alg.cra_blkcipher.max_keysize = alg->cra_cipher.cia_max_keysize
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+ noncesize;
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inst->alg.cra_ctxsize = sizeof(struct crypto_ctr_ctx);
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inst->alg.cra_init = crypto_ctr_init_tfm;
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inst->alg.cra_exit = crypto_ctr_exit_tfm;
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inst->alg.cra_blkcipher.setkey = crypto_ctr_setkey;
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inst->alg.cra_blkcipher.encrypt = crypto_ctr_crypt;
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inst->alg.cra_blkcipher.decrypt = crypto_ctr_crypt;
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err_free_inst:
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if (err)
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kfree(inst);
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out_put_alg:
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crypto_mod_put(alg);
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if (err)
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inst = ERR_PTR(err);
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return inst;
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}
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static void crypto_ctr_free(struct crypto_instance *inst)
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{
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struct ctr_instance_ctx *ictx = crypto_instance_ctx(inst);
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crypto_drop_spawn(&ictx->alg);
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kfree(inst);
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}
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static struct crypto_template crypto_ctr_tmpl = {
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.name = "ctr",
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.alloc = crypto_ctr_alloc,
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.free = crypto_ctr_free,
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.module = THIS_MODULE,
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};
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static int __init crypto_ctr_module_init(void)
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{
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return crypto_register_template(&crypto_ctr_tmpl);
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}
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static void __exit crypto_ctr_module_exit(void)
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{
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crypto_unregister_template(&crypto_ctr_tmpl);
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}
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module_init(crypto_ctr_module_init);
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module_exit(crypto_ctr_module_exit);
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("CTR Counter block mode");
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