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crypto: gcm - make GMAC work when dst and src are different
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The GMAC code assumes that dst==src, which causes problems when trying to add
rfc4543(gcm(aes)) test vectors.

So fix this code to work when source and destination buffer are different.

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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Jussi Kivilinna authored and Herbert Xu committed Apr 25, 2013
1 parent b149a30 commit 9489667
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Showing 2 changed files with 81 additions and 17 deletions.
1 change: 1 addition & 0 deletions crypto/Kconfig
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Original file line number Diff line number Diff line change
Expand Up @@ -198,6 +198,7 @@ config CRYPTO_GCM
select CRYPTO_CTR
select CRYPTO_AEAD
select CRYPTO_GHASH
select CRYPTO_NULL
help
Support for Galois/Counter Mode (GCM) and Galois Message
Authentication Code (GMAC). Required for IPSec.
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97 changes: 80 additions & 17 deletions crypto/gcm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -37,8 +37,14 @@ struct crypto_rfc4106_ctx {
u8 nonce[4];
};

struct crypto_rfc4543_instance_ctx {
struct crypto_aead_spawn aead;
struct crypto_skcipher_spawn null;
};

struct crypto_rfc4543_ctx {
struct crypto_aead *child;
struct crypto_blkcipher *null;
u8 nonce[4];
};

Expand Down Expand Up @@ -1094,20 +1100,20 @@ static int crypto_rfc4543_setauthsize(struct crypto_aead *parent,
}

static struct aead_request *crypto_rfc4543_crypt(struct aead_request *req,
int enc)
bool enc)
{
struct crypto_aead *aead = crypto_aead_reqtfm(req);
struct crypto_rfc4543_ctx *ctx = crypto_aead_ctx(aead);
struct crypto_rfc4543_req_ctx *rctx = crypto_rfc4543_reqctx(req);
struct aead_request *subreq = &rctx->subreq;
struct scatterlist *dst = req->dst;
struct scatterlist *src = req->src;
struct scatterlist *cipher = rctx->cipher;
struct scatterlist *payload = rctx->payload;
struct scatterlist *assoc = rctx->assoc;
unsigned int authsize = crypto_aead_authsize(aead);
unsigned int assoclen = req->assoclen;
struct page *dstp;
u8 *vdst;
struct page *srcp;
u8 *vsrc;
u8 *iv = PTR_ALIGN((u8 *)(rctx + 1) + crypto_aead_reqsize(ctx->child),
crypto_aead_alignmask(ctx->child) + 1);

Expand All @@ -1118,19 +1124,19 @@ static struct aead_request *crypto_rfc4543_crypt(struct aead_request *req,
if (enc)
memset(rctx->auth_tag, 0, authsize);
else
scatterwalk_map_and_copy(rctx->auth_tag, dst,
scatterwalk_map_and_copy(rctx->auth_tag, src,
req->cryptlen - authsize,
authsize, 0);

sg_init_one(cipher, rctx->auth_tag, authsize);

/* construct the aad */
dstp = sg_page(dst);
vdst = PageHighMem(dstp) ? NULL : page_address(dstp) + dst->offset;
srcp = sg_page(src);
vsrc = PageHighMem(srcp) ? NULL : page_address(srcp) + src->offset;

sg_init_table(payload, 2);
sg_set_buf(payload, req->iv, 8);
scatterwalk_crypto_chain(payload, dst, vdst == req->iv + 8, 2);
scatterwalk_crypto_chain(payload, src, vsrc == req->iv + 8, 2);
assoclen += 8 + req->cryptlen - (enc ? 0 : authsize);

sg_init_table(assoc, 2);
Expand All @@ -1147,14 +1153,33 @@ static struct aead_request *crypto_rfc4543_crypt(struct aead_request *req,
return subreq;
}

static int crypto_rfc4543_copy_src_to_dst(struct aead_request *req, bool enc)
{
struct crypto_aead *aead = crypto_aead_reqtfm(req);
struct crypto_rfc4543_ctx *ctx = crypto_aead_ctx(aead);
unsigned int authsize = crypto_aead_authsize(aead);
unsigned int nbytes = req->cryptlen - (enc ? 0 : authsize);
struct blkcipher_desc desc = {
.tfm = ctx->null,
};

return crypto_blkcipher_encrypt(&desc, req->dst, req->src, nbytes);
}

static int crypto_rfc4543_encrypt(struct aead_request *req)
{
struct crypto_aead *aead = crypto_aead_reqtfm(req);
struct crypto_rfc4543_req_ctx *rctx = crypto_rfc4543_reqctx(req);
struct aead_request *subreq;
int err;

subreq = crypto_rfc4543_crypt(req, 1);
if (req->src != req->dst) {
err = crypto_rfc4543_copy_src_to_dst(req, true);
if (err)
return err;
}

subreq = crypto_rfc4543_crypt(req, true);
err = crypto_aead_encrypt(subreq);
if (err)
return err;
Expand All @@ -1167,24 +1192,41 @@ static int crypto_rfc4543_encrypt(struct aead_request *req)

static int crypto_rfc4543_decrypt(struct aead_request *req)
{
req = crypto_rfc4543_crypt(req, 0);
int err;

if (req->src != req->dst) {
err = crypto_rfc4543_copy_src_to_dst(req, false);
if (err)
return err;
}

req = crypto_rfc4543_crypt(req, false);

return crypto_aead_decrypt(req);
}

static int crypto_rfc4543_init_tfm(struct crypto_tfm *tfm)
{
struct crypto_instance *inst = (void *)tfm->__crt_alg;
struct crypto_aead_spawn *spawn = crypto_instance_ctx(inst);
struct crypto_rfc4543_instance_ctx *ictx = crypto_instance_ctx(inst);
struct crypto_aead_spawn *spawn = &ictx->aead;
struct crypto_rfc4543_ctx *ctx = crypto_tfm_ctx(tfm);
struct crypto_aead *aead;
struct crypto_blkcipher *null;
unsigned long align;
int err = 0;

aead = crypto_spawn_aead(spawn);
if (IS_ERR(aead))
return PTR_ERR(aead);

null = crypto_spawn_blkcipher(&ictx->null.base);
err = PTR_ERR(null);
if (IS_ERR(null))
goto err_free_aead;

ctx->child = aead;
ctx->null = null;

align = crypto_aead_alignmask(aead);
align &= ~(crypto_tfm_ctx_alignment() - 1);
Expand All @@ -1194,13 +1236,18 @@ static int crypto_rfc4543_init_tfm(struct crypto_tfm *tfm)
align + 16;

return 0;

err_free_aead:
crypto_free_aead(aead);
return err;
}

static void crypto_rfc4543_exit_tfm(struct crypto_tfm *tfm)
{
struct crypto_rfc4543_ctx *ctx = crypto_tfm_ctx(tfm);

crypto_free_aead(ctx->child);
crypto_free_blkcipher(ctx->null);
}

static struct crypto_instance *crypto_rfc4543_alloc(struct rtattr **tb)
Expand All @@ -1209,6 +1256,7 @@ static struct crypto_instance *crypto_rfc4543_alloc(struct rtattr **tb)
struct crypto_instance *inst;
struct crypto_aead_spawn *spawn;
struct crypto_alg *alg;
struct crypto_rfc4543_instance_ctx *ctx;
const char *ccm_name;
int err;

Expand All @@ -1223,11 +1271,12 @@ static struct crypto_instance *crypto_rfc4543_alloc(struct rtattr **tb)
if (IS_ERR(ccm_name))
return ERR_CAST(ccm_name);

inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
if (!inst)
return ERR_PTR(-ENOMEM);

spawn = crypto_instance_ctx(inst);
ctx = crypto_instance_ctx(inst);
spawn = &ctx->aead;
crypto_set_aead_spawn(spawn, inst);
err = crypto_grab_aead(spawn, ccm_name, 0,
crypto_requires_sync(algt->type, algt->mask));
Expand All @@ -1236,23 +1285,31 @@ static struct crypto_instance *crypto_rfc4543_alloc(struct rtattr **tb)

alg = crypto_aead_spawn_alg(spawn);

crypto_set_skcipher_spawn(&ctx->null, inst);
err = crypto_grab_skcipher(&ctx->null, "ecb(cipher_null)", 0,
CRYPTO_ALG_ASYNC);
if (err)
goto out_drop_alg;

crypto_skcipher_spawn_alg(&ctx->null);

err = -EINVAL;

/* We only support 16-byte blocks. */
if (alg->cra_aead.ivsize != 16)
goto out_drop_alg;
goto out_drop_ecbnull;

/* Not a stream cipher? */
if (alg->cra_blocksize != 1)
goto out_drop_alg;
goto out_drop_ecbnull;

err = -ENAMETOOLONG;
if (snprintf(inst->alg.cra_name, CRYPTO_MAX_ALG_NAME,
"rfc4543(%s)", alg->cra_name) >= CRYPTO_MAX_ALG_NAME ||
snprintf(inst->alg.cra_driver_name, CRYPTO_MAX_ALG_NAME,
"rfc4543(%s)", alg->cra_driver_name) >=
CRYPTO_MAX_ALG_NAME)
goto out_drop_alg;
goto out_drop_ecbnull;

inst->alg.cra_flags = CRYPTO_ALG_TYPE_AEAD;
inst->alg.cra_flags |= alg->cra_flags & CRYPTO_ALG_ASYNC;
Expand All @@ -1279,6 +1336,8 @@ static struct crypto_instance *crypto_rfc4543_alloc(struct rtattr **tb)
out:
return inst;

out_drop_ecbnull:
crypto_drop_skcipher(&ctx->null);
out_drop_alg:
crypto_drop_aead(spawn);
out_free_inst:
Expand All @@ -1289,7 +1348,11 @@ static struct crypto_instance *crypto_rfc4543_alloc(struct rtattr **tb)

static void crypto_rfc4543_free(struct crypto_instance *inst)
{
crypto_drop_spawn(crypto_instance_ctx(inst));
struct crypto_rfc4543_instance_ctx *ctx = crypto_instance_ctx(inst);

crypto_drop_aead(&ctx->aead);
crypto_drop_skcipher(&ctx->null);

kfree(inst);
}

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