crypto: gcm - fix incompatibility between "gcm" and "gcm_base"
GCM instances can be created by either the "gcm" template, which only
allows choosing the block cipher, e.g. "gcm(aes)"; or by "gcm_base",
which allows choosing the ctr and ghash implementations, e.g.
"gcm_base(ctr(aes-generic),ghash-generic)".
However, a "gcm_base" instance prevents a "gcm" instance from being
registered using the same implementations. Nor will the instance be
found by lookups of "gcm". This can be used as a denial of service.
Moreover, "gcm_base" instances are never tested by the crypto
self-tests, even if there are compatible "gcm" tests.
The root cause of these problems is that instances of the two templates
use different cra_names. Therefore, fix these problems by making
"gcm_base" instances set the same cra_name as "gcm" instances, e.g.
"gcm(aes)" instead of "gcm_base(ctr(aes-generic),ghash-generic)".
This requires extracting the block cipher name from the name of the ctr
algorithm. It also requires starting to verify that the algorithms are
really ctr and ghash, not something else entirely. But it would be
bizarre if anyone were actually using non-gcm-compatible algorithms with
gcm_base, so this shouldn't break anyone in practice.
Fixes: d00aa19b507b ("[CRYPTO] gcm: Allow block cipher parameter")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/crypto/gcm.c b/crypto/gcm.c
index ff49841..33f45a9 100644
--- a/crypto/gcm.c
+++ b/crypto/gcm.c
@@ -597,7 +597,6 @@
static int crypto_gcm_create_common(struct crypto_template *tmpl,
struct rtattr **tb,
- const char *full_name,
const char *ctr_name,
const char *ghash_name)
{
@@ -638,7 +637,8 @@
goto err_free_inst;
err = -EINVAL;
- if (ghash->digestsize != 16)
+ if (strcmp(ghash->base.cra_name, "ghash") != 0 ||
+ ghash->digestsize != 16)
goto err_drop_ghash;
crypto_set_skcipher_spawn(&ctx->ctr, aead_crypto_instance(inst));
@@ -650,24 +650,24 @@
ctr = crypto_spawn_skcipher_alg(&ctx->ctr);
- /* We only support 16-byte blocks. */
+ /* The skcipher algorithm must be CTR mode, using 16-byte blocks. */
err = -EINVAL;
- if (crypto_skcipher_alg_ivsize(ctr) != 16)
- goto out_put_ctr;
-
- /* Not a stream cipher? */
- if (ctr->base.cra_blocksize != 1)
+ if (strncmp(ctr->base.cra_name, "ctr(", 4) != 0 ||
+ crypto_skcipher_alg_ivsize(ctr) != 16 ||
+ ctr->base.cra_blocksize != 1)
goto out_put_ctr;
err = -ENAMETOOLONG;
+ if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
+ "gcm(%s", ctr->base.cra_name + 4) >= CRYPTO_MAX_ALG_NAME)
+ goto out_put_ctr;
+
if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
"gcm_base(%s,%s)", ctr->base.cra_driver_name,
ghash_alg->cra_driver_name) >=
CRYPTO_MAX_ALG_NAME)
goto out_put_ctr;
- memcpy(inst->alg.base.cra_name, full_name, CRYPTO_MAX_ALG_NAME);
-
inst->alg.base.cra_flags = (ghash->base.cra_flags |
ctr->base.cra_flags) & CRYPTO_ALG_ASYNC;
inst->alg.base.cra_priority = (ghash->base.cra_priority +
@@ -709,7 +709,6 @@
{
const char *cipher_name;
char ctr_name[CRYPTO_MAX_ALG_NAME];
- char full_name[CRYPTO_MAX_ALG_NAME];
cipher_name = crypto_attr_alg_name(tb[1]);
if (IS_ERR(cipher_name))
@@ -719,12 +718,7 @@
CRYPTO_MAX_ALG_NAME)
return -ENAMETOOLONG;
- if (snprintf(full_name, CRYPTO_MAX_ALG_NAME, "gcm(%s)", cipher_name) >=
- CRYPTO_MAX_ALG_NAME)
- return -ENAMETOOLONG;
-
- return crypto_gcm_create_common(tmpl, tb, full_name,
- ctr_name, "ghash");
+ return crypto_gcm_create_common(tmpl, tb, ctr_name, "ghash");
}
static int crypto_gcm_base_create(struct crypto_template *tmpl,
@@ -732,7 +726,6 @@
{
const char *ctr_name;
const char *ghash_name;
- char full_name[CRYPTO_MAX_ALG_NAME];
ctr_name = crypto_attr_alg_name(tb[1]);
if (IS_ERR(ctr_name))
@@ -742,12 +735,7 @@
if (IS_ERR(ghash_name))
return PTR_ERR(ghash_name);
- if (snprintf(full_name, CRYPTO_MAX_ALG_NAME, "gcm_base(%s,%s)",
- ctr_name, ghash_name) >= CRYPTO_MAX_ALG_NAME)
- return -ENAMETOOLONG;
-
- return crypto_gcm_create_common(tmpl, tb, full_name,
- ctr_name, ghash_name);
+ return crypto_gcm_create_common(tmpl, tb, ctr_name, ghash_name);
}
static int crypto_rfc4106_setkey(struct crypto_aead *parent, const u8 *key,
