crypto: dh - make crypto_dh_encode_key() make robust

Make it return -EINVAL if crypto_dh_key_len() is incorrect rather than
overflowing the buffer.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/crypto/dh_helper.c b/crypto/dh_helper.c
index db9b2d9..edacda5 100644 (file)
--- a/crypto/dh_helper.c
+++ b/crypto/dh_helper.c
@@ -16,8 +16,10 @@
 
 #define DH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + 4 * sizeof(int))
 
-static inline u8 *dh_pack_data(void *dst, const void *src, size_t size)
+static inline u8 *dh_pack_data(u8 *dst, u8 *end, const void *src, size_t size)
 {
+       if (!dst || size > end - dst)
+               return NULL;
        memcpy(dst, src, size);
        return dst + size;
 }
@@ -42,27 +44,27 @@ EXPORT_SYMBOL_GPL(crypto_dh_key_len);
 int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params)
 {
        u8 *ptr = buf;
+       u8 * const end = ptr + len;
        struct kpp_secret secret = {
                .type = CRYPTO_KPP_SECRET_TYPE_DH,
                .len = len
        };
 
-       if (unlikely(!buf))
+       if (unlikely(!len))
                return -EINVAL;
 
-       if (len != crypto_dh_key_len(params))
+       ptr = dh_pack_data(ptr, end, &secret, sizeof(secret));
+       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;
-
-       ptr = dh_pack_data(ptr, &secret, sizeof(secret));
-       ptr = dh_pack_data(ptr, &params->key_size, sizeof(params->key_size));
-       ptr = dh_pack_data(ptr, &params->p_size, sizeof(params->p_size));
-       ptr = dh_pack_data(ptr, &params->q_size, sizeof(params->q_size));
-       ptr = dh_pack_data(ptr, &params->g_size, sizeof(params->g_size));
-       ptr = dh_pack_data(ptr, params->key, params->key_size);
-       ptr = dh_pack_data(ptr, params->p, params->p_size);
-       ptr = dh_pack_data(ptr, params->q, params->q_size);
-       dh_pack_data(ptr, params->g, params->g_size);
-
        return 0;
 }
 EXPORT_SYMBOL_GPL(crypto_dh_encode_key);