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DPP: Move PKEX Exchange Response building to a helper function

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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>
This commit is contained in:
Jouni Malinen 2017-11-02 21:13:43 +02:00 committed by Jouni Malinen
parent 60b9dd86fd
commit a5c3b41b2f
1 changed files with 67 additions and 51 deletions
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118
src/common/dpp.c
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@ -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);