crypto: gcm - make GMAC work when dst and src are different

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>

2 files changed, 81 insertions, 17 deletions

diff --git a/crypto/Kconfig b/crypto/Kconfig
index a654b13ae004..6cc27f111551 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -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.
diff --git a/crypto/gcm.c b/crypto/gcm.c
index 137ad1ec5438..4ff213997fbd 100644
--- a/crypto/gcm.c
+++ b/crypto/gcm.c
@@ -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];
 };
 
@@ -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);
 
@@ -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);
@@ -1147,6 +1153,19 @@ 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);
@@ -1154,7 +1173,13 @@ static int crypto_rfc4543_encrypt(struct aead_request *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;
@@ -1167,7 +1192,15 @@ 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);
 }
@@ -1175,16 +1208,25 @@ static int crypto_rfc4543_decrypt(struct aead_request *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);
@@ -1194,6 +1236,10 @@ 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)
@@ -1201,6 +1247,7 @@ 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)
@@ -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;
 
@@ -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));
@@ -1236,15 +1285,23 @@ 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,
@@ -1252,7 +1309,7 @@ static struct crypto_instance *crypto_rfc4543_alloc(struct rtattr **tb)
             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;
@@ -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:
@@ -1289,7 +1348,11 @@ out_free_inst:
 
 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);
 }