diff options
Diffstat (limited to 'crypto/ctr.c')
| -rw-r--r-- | crypto/ctr.c | 369 |
1 files changed, 369 insertions, 0 deletions
diff --git a/crypto/ctr.c b/crypto/ctr.c new file mode 100644 index 000000000000..810d5ec2d5d2 --- /dev/null +++ b/crypto/ctr.c @@ -0,0 +1,369 @@ +/* + * CTR: Counter mode + * + * (C) Copyright IBM Corp. 2007 - Joy Latten <latten@us.ibm.com> + * + * 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/algapi.h> +#include <linux/err.h> +#include <linux/init.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/random.h> +#include <linux/scatterlist.h> +#include <linux/slab.h> + +struct ctr_instance_ctx { + struct crypto_spawn alg; + unsigned int noncesize; + unsigned int ivsize; +}; + +struct crypto_ctr_ctx { + struct crypto_cipher *child; + u8 *nonce; +}; + +static inline void __ctr_inc_byte(u8 *a, unsigned int size) +{ + u8 *b = (a + size); + u8 c; + + for (; size; size--) { + c = *--b + 1; + *b = c; + if (c) + break; + } +} + +static void ctr_inc_quad(u8 *a, unsigned int size) +{ + __be32 *b = (__be32 *)(a + size); + u32 c; + + for (; size >= 4; size -=4) { + c = be32_to_cpu(*--b) + 1; + *b = cpu_to_be32(c); + if (c) + return; + } + + __ctr_inc_byte(a, size); +} + +static void xor_byte(u8 *a, const u8 *b, unsigned int bs) +{ + for (; bs; bs--) + *a++ ^= *b++; +} + +static void xor_quad(u8 *dst, const u8 *src, unsigned int bs) +{ + u32 *a = (u32 *)dst; + u32 *b = (u32 *)src; + + for (; bs >= 4; bs -= 4) + *a++ ^= *b++; + + xor_byte((u8 *)a, (u8 *)b, bs); +} + +static int crypto_ctr_setkey(struct crypto_tfm *parent, const u8 *key, + unsigned int keylen) +{ + struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(parent); + struct crypto_cipher *child = ctx->child; + struct ctr_instance_ctx *ictx = + crypto_instance_ctx(crypto_tfm_alg_instance(parent)); + unsigned int noncelen = ictx->noncesize; + int err = 0; + + /* the nonce is stored in bytes at end of key */ + if (keylen < noncelen) + return -EINVAL; + + memcpy(ctx->nonce, key + (keylen - noncelen), noncelen); + + keylen -= noncelen; + + crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK); + crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) & + CRYPTO_TFM_REQ_MASK); + err = crypto_cipher_setkey(child, key, keylen); + crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) & + CRYPTO_TFM_RES_MASK); + + return err; +} + +static int crypto_ctr_crypt_segment(struct blkcipher_walk *walk, + struct crypto_cipher *tfm, u8 *ctrblk, + unsigned int countersize) +{ + void (*fn)(struct crypto_tfm *, u8 *, const u8 *) = + crypto_cipher_alg(tfm)->cia_encrypt; + unsigned int bsize = crypto_cipher_blocksize(tfm); + unsigned long alignmask = crypto_cipher_alignmask(tfm); + u8 ks[bsize + alignmask]; + u8 *keystream = (u8 *)ALIGN((unsigned long)ks, alignmask + 1); + u8 *src = walk->src.virt.addr; + u8 *dst = walk->dst.virt.addr; + unsigned int nbytes = walk->nbytes; + + do { + /* create keystream */ + fn(crypto_cipher_tfm(tfm), keystream, ctrblk); + xor_quad(keystream, src, min(nbytes, bsize)); + + /* copy result into dst */ + memcpy(dst, keystream, min(nbytes, bsize)); + + /* increment counter in counterblock */ + ctr_inc_quad(ctrblk + (bsize - countersize), countersize); + + if (nbytes < bsize) + break; + + src += bsize; + dst += bsize; + nbytes -= bsize; + + } while (nbytes); + + return 0; +} + +static int crypto_ctr_crypt_inplace(struct blkcipher_walk *walk, + struct crypto_cipher *tfm, u8 *ctrblk, + unsigned int countersize) +{ + void (*fn)(struct crypto_tfm *, u8 *, const u8 *) = + crypto_cipher_alg(tfm)->cia_encrypt; + unsigned int bsize = crypto_cipher_blocksize(tfm); + unsigned long alignmask = crypto_cipher_alignmask(tfm); + unsigned int nbytes = walk->nbytes; + u8 *src = walk->src.virt.addr; + u8 ks[bsize + alignmask]; + u8 *keystream = (u8 *)ALIGN((unsigned long)ks, alignmask + 1); + + do { + /* create keystream */ + fn(crypto_cipher_tfm(tfm), keystream, ctrblk); + xor_quad(src, keystream, min(nbytes, bsize)); + + /* increment counter in counterblock */ + ctr_inc_quad(ctrblk + (bsize - countersize), countersize); + + if (nbytes < bsize) + break; + + src += bsize; + nbytes -= bsize; + + } while (nbytes); + + return 0; +} + +static int crypto_ctr_crypt(struct blkcipher_desc *desc, + struct scatterlist *dst, struct scatterlist *src, + unsigned int nbytes) +{ + struct blkcipher_walk walk; + struct crypto_blkcipher *tfm = desc->tfm; + struct crypto_ctr_ctx *ctx = crypto_blkcipher_ctx(tfm); + struct crypto_cipher *child = ctx->child; + unsigned int bsize = crypto_cipher_blocksize(child); + struct ctr_instance_ctx *ictx = + crypto_instance_ctx(crypto_tfm_alg_instance(&tfm->base)); + unsigned long alignmask = crypto_cipher_alignmask(child); + u8 cblk[bsize + alignmask]; + u8 *counterblk = (u8 *)ALIGN((unsigned long)cblk, alignmask + 1); + unsigned int countersize; + int err; + + blkcipher_walk_init(&walk, dst, src, nbytes); + err = blkcipher_walk_virt_block(desc, &walk, bsize); + + /* set up counter block */ + memset(counterblk, 0 , bsize); + memcpy(counterblk, ctx->nonce, ictx->noncesize); + memcpy(counterblk + ictx->noncesize, walk.iv, ictx->ivsize); + + /* initialize counter portion of counter block */ + countersize = bsize - ictx->noncesize - ictx->ivsize; + ctr_inc_quad(counterblk + (bsize - countersize), countersize); + + while (walk.nbytes) { + if (walk.src.virt.addr == walk.dst.virt.addr) + nbytes = crypto_ctr_crypt_inplace(&walk, child, + counterblk, + countersize); + else + nbytes = crypto_ctr_crypt_segment(&walk, child, + counterblk, + countersize); + + err = blkcipher_walk_done(desc, &walk, nbytes); + } + return err; +} + +static int crypto_ctr_init_tfm(struct crypto_tfm *tfm) +{ + struct crypto_instance *inst = (void *)tfm->__crt_alg; + struct ctr_instance_ctx *ictx = crypto_instance_ctx(inst); + struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm); + struct crypto_cipher *cipher; + + ctx->nonce = kzalloc(ictx->noncesize, GFP_KERNEL); + if (!ctx->nonce) + return -ENOMEM; + + cipher = crypto_spawn_cipher(&ictx->alg); + if (IS_ERR(cipher)) + return PTR_ERR(cipher); + + ctx->child = cipher; + + return 0; +} + +static void crypto_ctr_exit_tfm(struct crypto_tfm *tfm) +{ + struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm); + + kfree(ctx->nonce); + crypto_free_cipher(ctx->child); +} + +static struct crypto_instance *crypto_ctr_alloc(struct rtattr **tb) +{ + struct crypto_instance *inst; + struct crypto_alg *alg; + struct ctr_instance_ctx *ictx; + unsigned int noncesize; + unsigned int ivsize; + int err; + + err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER); + if (err) + return ERR_PTR(err); + + alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER, + CRYPTO_ALG_TYPE_MASK); + if (IS_ERR(alg)) + return ERR_PTR(PTR_ERR(alg)); + + err = crypto_attr_u32(tb[2], &noncesize); + if (err) + goto out_put_alg; + + err = crypto_attr_u32(tb[3], &ivsize); + if (err) + goto out_put_alg; + + /* verify size of nonce + iv + counter */ + err = -EINVAL; + if ((noncesize + ivsize) >= alg->cra_blocksize) + goto out_put_alg; + + inst = kzalloc(sizeof(*inst) + sizeof(*ictx), GFP_KERNEL); + err = -ENOMEM; + if (!inst) + goto out_put_alg; + + err = -ENAMETOOLONG; + if (snprintf(inst->alg.cra_name, CRYPTO_MAX_ALG_NAME, + "ctr(%s,%u,%u)", alg->cra_name, noncesize, + ivsize) >= CRYPTO_MAX_ALG_NAME) { + goto err_free_inst; + } + + if (snprintf(inst->alg.cra_driver_name, CRYPTO_MAX_ALG_NAME, + "ctr(%s,%u,%u)", alg->cra_driver_name, noncesize, + ivsize) >= CRYPTO_MAX_ALG_NAME) { + goto err_free_inst; + } + + ictx = crypto_instance_ctx(inst); + ictx->noncesize = noncesize; + ictx->ivsize = ivsize; + + err = crypto_init_spawn(&ictx->alg, alg, inst, + CRYPTO_ALG_TYPE_MASK | CRYPTO_ALG_ASYNC); + if (err) + goto err_free_inst; + + err = 0; + inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER; + inst->alg.cra_priority = alg->cra_priority; + inst->alg.cra_blocksize = 1; + inst->alg.cra_alignmask = 3; + inst->alg.cra_type = &crypto_blkcipher_type; + + inst->alg.cra_blkcipher.ivsize = ivsize; + inst->alg.cra_blkcipher.min_keysize = alg->cra_cipher.cia_min_keysize + + noncesize; + inst->alg.cra_blkcipher.max_keysize = alg->cra_cipher.cia_max_keysize + + noncesize; + + inst->alg.cra_ctxsize = sizeof(struct crypto_ctr_ctx); + + inst->alg.cra_init = crypto_ctr_init_tfm; + inst->alg.cra_exit = crypto_ctr_exit_tfm; + + inst->alg.cra_blkcipher.setkey = crypto_ctr_setkey; + inst->alg.cra_blkcipher.encrypt = crypto_ctr_crypt; + inst->alg.cra_blkcipher.decrypt = crypto_ctr_crypt; + +err_free_inst: + if (err) + kfree(inst); + +out_put_alg: + crypto_mod_put(alg); + + if (err) + inst = ERR_PTR(err); + + return inst; +} + +static void crypto_ctr_free(struct crypto_instance *inst) +{ + struct ctr_instance_ctx *ictx = crypto_instance_ctx(inst); + + crypto_drop_spawn(&ictx->alg); + kfree(inst); +} + +static struct crypto_template crypto_ctr_tmpl = { + .name = "ctr", + .alloc = crypto_ctr_alloc, + .free = crypto_ctr_free, + .module = THIS_MODULE, +}; + +static int __init crypto_ctr_module_init(void) +{ + return crypto_register_template(&crypto_ctr_tmpl); +} + +static void __exit crypto_ctr_module_exit(void) +{ + crypto_unregister_template(&crypto_ctr_tmpl); +} + +module_init(crypto_ctr_module_init); +module_exit(crypto_ctr_module_exit); + +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("CTR Counter block mode"); |