From: Eric Biggers ebiggers@google.com

[This is essentially the same as the corresponding patch to GCM.]

CCM instances can be created by either the "ccm" template, which only allows choosing the block cipher, e.g. "ccm(aes)"; or by "ccm_base", which allows choosing the ctr and cbcmac implementations, e.g. "ccm_base(ctr(aes-generic),cbcmac(aes-generic))".

However, a "ccm_base" instance prevents a "ccm" instance from being registered using the same implementations. Nor will the instance be found by lookups of "ccm". This can be used as a denial of service. Moreover, "ccm_base" instances are never tested by the crypto self-tests, even if there are compatible "ccm" tests.

The root cause of these problems is that instances of the two templates use different cra_names. Therefore, fix these problems by making "ccm_base" instances set the same cra_name as "ccm" instances, e.g. "ccm(aes)" instead of "ccm_base(ctr(aes-generic),cbcmac(aes-generic))".

This requires extracting the block cipher name from the name of the ctr algorithm, which means starting to require that the stream cipher really be ctr and not something else. But it would be pretty bizarre if anyone was actually relying on being able to use a non-ctr stream cipher here.

Fixes: 4a49b499dfa0 ("[CRYPTO] ccm: Added CCM mode") Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers ebiggers@google.com --- crypto/ccm.c | 38 ++++++++++++-------------------------- 1 file changed, 12 insertions(+), 26 deletions(-)

diff --git a/crypto/ccm.c b/crypto/ccm.c index 50df8f001c1c9..3bb49776450b7 100644 --- a/crypto/ccm.c +++ b/crypto/ccm.c @@ -458,7 +458,6 @@ static void crypto_ccm_free(struct aead_instance *inst)

static int crypto_ccm_create_common(struct crypto_template *tmpl, struct rtattr **tb, - const char *full_name, const char *ctr_name, const char *mac_name) { @@ -509,23 +508,22 @@ static int crypto_ccm_create_common(struct crypto_template *tmpl,

ctr = crypto_spawn_skcipher_alg(&ictx->ctr);

- /* Not a stream cipher? */ + /* Must be CTR mode with 16-byte blocks. */ err = -EINVAL; - if (ctr->base.cra_blocksize != 1) + if (strncmp(ctr->base.cra_name, "ctr(", 4) != 0 || + crypto_skcipher_alg_ivsize(ctr) != 16) goto err_drop_ctr;

- /* We want the real thing! */ - if (crypto_skcipher_alg_ivsize(ctr) != 16) + err = -ENAMETOOLONG; + if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME, + "ccm(%s", ctr->base.cra_name + 4) >= CRYPTO_MAX_ALG_NAME) goto err_drop_ctr;

- err = -ENAMETOOLONG; if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME, "ccm_base(%s,%s)", ctr->base.cra_driver_name, mac->base.cra_driver_name) >= CRYPTO_MAX_ALG_NAME) goto err_drop_ctr;

- memcpy(inst->alg.base.cra_name, full_name, CRYPTO_MAX_ALG_NAME); - inst->alg.base.cra_flags = ctr->base.cra_flags & CRYPTO_ALG_ASYNC; inst->alg.base.cra_priority = (mac->base.cra_priority + ctr->base.cra_priority) / 2; @@ -567,7 +565,6 @@ static int crypto_ccm_create(struct crypto_template *tmpl, struct rtattr **tb) const char *cipher_name; char ctr_name[CRYPTO_MAX_ALG_NAME]; char mac_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)) @@ -581,35 +578,24 @@ static int crypto_ccm_create(struct crypto_template *tmpl, struct rtattr **tb) cipher_name) >= CRYPTO_MAX_ALG_NAME) return -ENAMETOOLONG;

- if (snprintf(full_name, CRYPTO_MAX_ALG_NAME, "ccm(%s)", cipher_name) >= - CRYPTO_MAX_ALG_NAME) - return -ENAMETOOLONG; - - return crypto_ccm_create_common(tmpl, tb, full_name, ctr_name, - mac_name); + return crypto_ccm_create_common(tmpl, tb, ctr_name, mac_name); }

static int crypto_ccm_base_create(struct crypto_template *tmpl, struct rtattr **tb) { const char *ctr_name; - const char *cipher_name; - char full_name[CRYPTO_MAX_ALG_NAME]; + const char *mac_name;

ctr_name = crypto_attr_alg_name(tb[1]); if (IS_ERR(ctr_name)) return PTR_ERR(ctr_name);

- cipher_name = crypto_attr_alg_name(tb[2]); - if (IS_ERR(cipher_name)) - return PTR_ERR(cipher_name); - - if (snprintf(full_name, CRYPTO_MAX_ALG_NAME, "ccm_base(%s,%s)", - ctr_name, cipher_name) >= CRYPTO_MAX_ALG_NAME) - return -ENAMETOOLONG; + mac_name = crypto_attr_alg_name(tb[2]); + if (IS_ERR(mac_name)) + return PTR_ERR(mac_name);

- return crypto_ccm_create_common(tmpl, tb, full_name, ctr_name, - cipher_name); + return crypto_ccm_create_common(tmpl, tb, ctr_name, mac_name); }

static int crypto_rfc4309_setkey(struct crypto_aead *parent, const u8 *key,