crypto: dh - remove struct dh's ->q member

The only current user of the DH KPP algorithm, the
keyctl(KEYCTL_DH_COMPUTE) syscall, doesn't set the domain parameter ->q
in struct dh. Remove it and any associated (de)serialization code in
crypto_dh_encode_key() and crypto_dh_decode_key. Adjust the encoded
->secret values in testmgr's DH test vectors accordingly.

Note that the dh-generic implementation would have initialized its
struct dh_ctx's ->q from the decoded struct dh's ->q, if present. If this
struct dh_ctx's ->q would ever have been non-NULL, it would have enabled a
full key validation as specified in NIST SP800-56A in dh_is_pubkey_valid().
However, as outlined above, ->q is always NULL in practice and the full key
validation code is effectively dead. A later patch will make
dh_is_pubkey_valid() to calculate Q from P on the fly, if possible, so
don't remove struct dh_ctx's ->q now, but leave it there until that has
happened.

Signed-off-by: Nicolai Stange <nstange@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 4 insertions, 13 deletions

diff --git a/crypto/dh_helper.c b/crypto/dh_helper.c
index 9fd5a42eea15..aabc91e4f63f 100644
--- a/crypto/dh_helper.c
+++ b/crypto/dh_helper.c
@@ -10,7 +10,7 @@
 #include <crypto/dh.h>
 #include <crypto/kpp.h>
 
-#define DH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + 4 * sizeof(int))
+#define DH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + 3 * sizeof(int))
 
 static inline u8 *dh_pack_data(u8 *dst, u8 *end, const void *src, size_t size)
 {
@@ -28,7 +28,7 @@ static inline const u8 *dh_unpack_data(void *dst, const void *src, size_t size)
 
 static inline unsigned int dh_data_size(const struct dh *p)
 {
-	return p->key_size + p->p_size + p->q_size + p->g_size;
+	return p->key_size + p->p_size + p->g_size;
 }
 
 unsigned int crypto_dh_key_len(const struct dh *p)
@@ -53,11 +53,9 @@ int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params)
 	ptr = dh_pack_data(ptr, end, &params->key_size,
 			   sizeof(params->key_size));
 	ptr = dh_pack_data(ptr, end, &params->p_size, sizeof(params->p_size));
-	ptr = dh_pack_data(ptr, end, &params->q_size, sizeof(params->q_size));
 	ptr = dh_pack_data(ptr, end, &params->g_size, sizeof(params->g_size));
 	ptr = dh_pack_data(ptr, end, params->key, params->key_size);
 	ptr = dh_pack_data(ptr, end, params->p, params->p_size);
-	ptr = dh_pack_data(ptr, end, params->q, params->q_size);
 	ptr = dh_pack_data(ptr, end, params->g, params->g_size);
 	if (ptr != end)
 		return -EINVAL;
@@ -79,7 +77,6 @@ int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
 
 	ptr = dh_unpack_data(&params->key_size, ptr, sizeof(params->key_size));
 	ptr = dh_unpack_data(&params->p_size, ptr, sizeof(params->p_size));
-	ptr = dh_unpack_data(&params->q_size, ptr, sizeof(params->q_size));
 	ptr = dh_unpack_data(&params->g_size, ptr, sizeof(params->g_size));
 	if (secret.len != crypto_dh_key_len(params))
 		return -EINVAL;
@@ -89,7 +86,7 @@ int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
 	 * some drivers assume otherwise.
 	 */
 	if (params->key_size > params->p_size ||
-	    params->g_size > params->p_size || params->q_size > params->p_size)
+	    params->g_size > params->p_size)
 		return -EINVAL;
 
 	/* Don't allocate memory. Set pointers to data within
@@ -97,9 +94,7 @@ int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
 	 */
 	params->key = (void *)ptr;
 	params->p = (void *)(ptr + params->key_size);
-	params->q = (void *)(ptr + params->key_size + params->p_size);
-	params->g = (void *)(ptr + params->key_size + params->p_size +
-			     params->q_size);
+	params->g = (void *)(ptr + params->key_size + params->p_size);
 
 	/*
 	 * Don't permit 'p' to be 0.  It's not a prime number, and it's subject
@@ -109,10 +104,6 @@ int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
 	if (memchr_inv(params->p, 0, params->p_size) == NULL)
 		return -EINVAL;
 
-	/* It is permissible to not provide Q. */
-	if (params->q_size == 0)
-		params->q = NULL;
-
 	return 0;
 }
 EXPORT_SYMBOL_GPL(crypto_dh_decode_key);