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DPP2: PFS for PTK derivation

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Use Diffie-Hellman key exchange to derivate additional material for
PMK-to-PTK derivation to get PFS. The Diffie-Hellman Parameter element
(defined in OWE RFC 8110) is used in association frames to exchange the
DH public keys. For backwards compatibility, ignore missing
request/response DH parameter and fall back to no PFS in such cases.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
This commit is contained in:
Jouni Malinen 2019-03-17 23:51:53 +02:00 • committed by Jouni Malinen
parent ecacd9ccd4
commit 10ec6a5f38
17 changed files with 330 additions and 2 deletions
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84
src/common/dpp.c
View file

@ -8131,3 +8131,87 @@ fail:
goto out;
}
#endif /* CONFIG_TESTING_OPTIONS */
#ifdef CONFIG_DPP2
struct dpp_pfs * dpp_pfs_init(const u8 *net_access_key,
size_t net_access_key_len)
{
struct wpabuf *pub = NULL;
EVP_PKEY *own_key;
struct dpp_pfs *pfs;
pfs = os_zalloc(sizeof(*pfs));
if (!pfs)
return NULL;
own_key = dpp_set_keypair(&pfs->curve, net_access_key,
net_access_key_len);
if (!own_key) {
wpa_printf(MSG_ERROR, "DPP: Failed to parse own netAccessKey");
goto fail;
}
EVP_PKEY_free(own_key);
pfs->ecdh = crypto_ecdh_init(pfs->curve->ike_group);
if (!pfs->ecdh)
goto fail;
pub = crypto_ecdh_get_pubkey(pfs->ecdh, 0);
pub = wpabuf_zeropad(pub, pfs->curve->prime_len);
if (!pub)
goto fail;
pfs->ie = wpabuf_alloc(5 + wpabuf_len(pub));
if (!pfs->ie)
goto fail;
wpabuf_put_u8(pfs->ie, WLAN_EID_EXTENSION);
wpabuf_put_u8(pfs->ie, 1 + 2 + wpabuf_len(pub));
wpabuf_put_u8(pfs->ie, WLAN_EID_EXT_OWE_DH_PARAM);
wpabuf_put_le16(pfs->ie, pfs->curve->ike_group);
wpabuf_put_buf(pfs->ie, pub);
wpabuf_free(pub);
wpa_hexdump_buf(MSG_DEBUG, "DPP: Diffie-Hellman Parameter element",
pfs->ie);
return pfs;
fail:
wpabuf_free(pub);
dpp_pfs_free(pfs);
return NULL;
}
int dpp_pfs_process(struct dpp_pfs *pfs, const u8 *peer_ie, size_t peer_ie_len)
{
if (peer_ie_len < 2)
return -1;
if (WPA_GET_LE16(peer_ie) != pfs->curve->ike_group) {
wpa_printf(MSG_DEBUG, "DPP: Peer used different group for PFS");
return -1;
}
pfs->secret = crypto_ecdh_set_peerkey(pfs->ecdh, 0, peer_ie + 2,
peer_ie_len - 2);
pfs->secret = wpabuf_zeropad(pfs->secret, pfs->curve->prime_len);
if (!pfs->secret) {
wpa_printf(MSG_DEBUG, "DPP: Invalid peer DH public key");
return -1;
}
wpa_hexdump_buf_key(MSG_DEBUG, "DPP: DH shared secret", pfs->secret);
return 0;
}
void dpp_pfs_free(struct dpp_pfs *pfs)
{
if (!pfs)
return;
crypto_ecdh_deinit(pfs->ecdh);
wpabuf_free(pfs->ie);
wpabuf_clear_free(pfs->secret);
os_free(pfs);
}
#endif /* CONFIG_DPP2 */