DPP: Move PKEX Exchange Response building to a helper function

This cleans up dpp_pkex_rx_exchange_req() a bit and makes it easier to
add protocol testing functionality to PKEX exchange similarly to the
previously added DPP Authentication case.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>

diff --git a/src/common/dpp.c b/src/common/dpp.c
index 4996d5cdd2e8fd5cb9e392e86c481a7a8e7be4a7..c1ec2d04128b84d4a15c7aec4703c7ca256845fa 100644 (file)
--- a/src/common/dpp.c
+++ b/src/common/dpp.c
@@ -5615,6 +5615,70 @@ fail:
 }
 
 
+static struct wpabuf * dpp_pkex_build_exchange_resp(struct dpp_pkex *pkex,
+                                                   const char *identifier,
+                                                   const BIGNUM *Nx,
+                                                   const BIGNUM *Ny)
+{
+       struct wpabuf *msg = NULL;
+       size_t attr_len;
+       int num_bytes, offset;
+       const struct dpp_curve_params *curve = pkex->own_bi->curve;
+
+       /* Initiator -> Responder: DPP Status, [identifier,] N */
+       attr_len = 4 + 1;
+       if (identifier)
+               attr_len += 4 + os_strlen(identifier);
+       attr_len += 4 + 2 * curve->prime_len;
+       msg = dpp_alloc_msg(DPP_PA_PKEX_EXCHANGE_RESP, attr_len);
+       if (!msg)
+               goto fail;
+
+       /* DPP Status */
+       wpabuf_put_le16(msg, DPP_ATTR_STATUS);
+       wpabuf_put_le16(msg, 1);
+       wpabuf_put_u8(msg, DPP_STATUS_OK);
+
+       /* Code Identifier attribute */
+       if (pkex->identifier) {
+               wpabuf_put_le16(msg, DPP_ATTR_CODE_IDENTIFIER);
+               wpabuf_put_le16(msg, os_strlen(pkex->identifier));
+               wpabuf_put_str(msg, pkex->identifier);
+       }
+
+       /* N in Encrypted Key attribute */
+       wpabuf_put_le16(msg, DPP_ATTR_ENCRYPTED_KEY);
+       wpabuf_put_le16(msg, 2 * curve->prime_len);
+
+       num_bytes = BN_num_bytes(Nx);
+       if ((size_t) num_bytes > curve->prime_len)
+               goto fail;
+       if (curve->prime_len > (size_t) num_bytes)
+               offset = curve->prime_len - num_bytes;
+       else
+               offset = 0;
+       os_memset(wpabuf_put(msg, offset), 0, offset);
+       BN_bn2bin(Nx, wpabuf_put(msg, num_bytes));
+       os_memset(pkex->Nx, 0, offset);
+       BN_bn2bin(Nx, pkex->Nx + offset);
+
+       num_bytes = BN_num_bytes(Ny);
+       if ((size_t) num_bytes > curve->prime_len)
+               goto fail;
+       if (curve->prime_len > (size_t) num_bytes)
+               offset = curve->prime_len - num_bytes;
+       else
+               offset = 0;
+       os_memset(wpabuf_put(msg, offset), 0, offset);
+       BN_bn2bin(Ny, wpabuf_put(msg, num_bytes));
+
+       return msg;
+fail:
+       wpabuf_free(msg);
+       return NULL;
+}
+
+
 struct dpp_pkex * dpp_pkex_rx_exchange_req(void *msg_ctx,
                                           struct dpp_bootstrap_info *bi,
                                           const u8 *own_mac,
@@ -5635,9 +5699,6 @@ struct dpp_pkex * dpp_pkex_rx_exchange_req(void *msg_ctx,
        EC_KEY *Y_ec = NULL, *X_ec = NULL;;
        const EC_POINT *Y_point;
        BIGNUM *Nx = NULL, *Ny = NULL;
-       struct wpabuf *msg = NULL;
-       size_t attr_len;
-       int num_bytes, offset;
 
        attr_id = dpp_get_attr(buf, len, DPP_ATTR_CODE_IDENTIFIER,
                               &attr_id_len);
@@ -5756,59 +5817,14 @@ struct dpp_pkex * dpp_pkex_rx_exchange_req(void *msg_ctx,
            EC_POINT_get_affine_coordinates_GFp(group, N, Nx, Ny, bnctx) != 1)
                goto fail;
 
-       /* Initiator -> Responder: DPP Status, [identifier,] N */
-       attr_len = 4 + 1;
-       if (identifier)
-               attr_len += 4 + os_strlen(identifier);
-       attr_len += 4 + 2 * curve->prime_len;
-       msg = dpp_alloc_msg(DPP_PA_PKEX_EXCHANGE_RESP, attr_len);
-       if (!msg)
+       pkex->exchange_resp = dpp_pkex_build_exchange_resp(pkex, identifier,
+                                                          Nx, Ny);
+       if (!pkex->exchange_resp)
                goto fail;
 
-       /* DPP Status */
-       wpabuf_put_le16(msg, DPP_ATTR_STATUS);
-       wpabuf_put_le16(msg, 1);
-       wpabuf_put_u8(msg, DPP_STATUS_OK);
-
-       /* Code Identifier attribute */
-       if (pkex->identifier) {
-               wpabuf_put_le16(msg, DPP_ATTR_CODE_IDENTIFIER);
-               wpabuf_put_le16(msg, os_strlen(pkex->identifier));
-               wpabuf_put_str(msg, pkex->identifier);
-       }
-
-       /* N in Encrypted Key attribute */
-       wpabuf_put_le16(msg, DPP_ATTR_ENCRYPTED_KEY);
-       wpabuf_put_le16(msg, 2 * curve->prime_len);
-
-       num_bytes = BN_num_bytes(Nx);
-       if ((size_t) num_bytes > curve->prime_len)
-               goto fail;
-       if (curve->prime_len > (size_t) num_bytes)
-               offset = curve->prime_len - num_bytes;
-       else
-               offset = 0;
-       os_memset(wpabuf_put(msg, offset), 0, offset);
-       BN_bn2bin(Nx, wpabuf_put(msg, num_bytes));
-       os_memset(pkex->Nx, 0, offset);
-       BN_bn2bin(Nx, pkex->Nx + offset);
-
-       num_bytes = BN_num_bytes(Ny);
-       if ((size_t) num_bytes > curve->prime_len)
-               goto fail;
-       if (curve->prime_len > (size_t) num_bytes)
-               offset = curve->prime_len - num_bytes;
-       else
-               offset = 0;
-       os_memset(wpabuf_put(msg, offset), 0, offset);
-       BN_bn2bin(Ny, wpabuf_put(msg, num_bytes));
-
-       pkex->exchange_resp = msg;
-       msg = NULL;
        pkex->exchange_done = 1;
 
 out:
-       wpabuf_free(msg);
        BN_CTX_free(bnctx);
        EC_POINT_free(Qi);
        EC_POINT_free(Qr);