DPP2: Derive a separate key for enveloped data

Derive a new key from bk to be used as the password for PBKDF2 instead
of using ke for this.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>

diff --git a/src/common/dpp_backup.c b/src/common/dpp_backup.c
index c675c427b384d35d1cf2b64e40415c77f72ecfa2..e12bc6d7ca0f7947dfe60c39612909b44a851157 100644 (file)
--- a/src/common/dpp_backup.c
+++ b/src/common/dpp_backup.c
@@ -275,18 +275,21 @@ dpp_build_pw_recipient_info(struct dpp_authentication *auth, size_t hash_len,
        struct wpabuf *pwri = NULL, *enc_key = NULL, *key_der_alg = NULL,
                *key_enc_alg = NULL, *salt;
        u8 kek[DPP_MAX_HASH_LEN];
-       const u8 *key;
+       u8 key[DPP_MAX_HASH_LEN];
        size_t key_len;
+       int res;
 
        salt = wpabuf_alloc(64);
        if (!salt || os_get_random(wpabuf_put(salt, 64), 64) < 0)
                goto fail;
        wpa_hexdump_buf(MSG_DEBUG, "DPP: PBKDF2 salt", salt);
 
-       /* TODO: For initial testing, use ke as the key. Replace this with a
-        * new key once that has been defined. */
-       key = auth->ke;
        key_len = auth->curve->hash_len;
+       /* password = HKDF-Expand(bk, "Enveloped Data Password", length) */
+       res = dpp_hkdf_expand(key_len, auth->bk, key_len,
+                             "Enveloped Data Password", key, key_len);
+       if (res < 0)
+               goto fail;
        wpa_hexdump_key(MSG_DEBUG, "DPP: PBKDF2 key", key, key_len);
 
        if (dpp_pbkdf2(hash_len, key, key_len, wpabuf_head(salt), 64, 1000,
@@ -1151,7 +1154,7 @@ dpp_parse_dpp_asymmetric_key_package(const u8 *key_pkg, size_t key_pkg_len)
 int dpp_conf_resp_env_data(struct dpp_authentication *auth,
                           const u8 *env_data, size_t env_data_len)
 {
-       const u8 *key;
+       u8 key[DPP_MAX_HASH_LEN];
        size_t key_len;
        u8 kek[DPP_MAX_HASH_LEN];
        u8 cont_encr_key[DPP_MAX_HASH_LEN];
@@ -1167,10 +1170,12 @@ int dpp_conf_resp_env_data(struct dpp_authentication *auth,
        if (dpp_parse_enveloped_data(env_data, env_data_len, &data) < 0)
                return -1;
 
-       /* TODO: For initial testing, use ke as the key. Replace this with a
-        * new key once that has been defined. */
-       key = auth->ke;
        key_len = auth->curve->hash_len;
+       /* password = HKDF-Expand(bk, "Enveloped Data Password", length) */
+       res = dpp_hkdf_expand(key_len, auth->bk, key_len,
+                             "Enveloped Data Password", key, key_len);
+       if (res < 0)
+               return -1;
        wpa_hexdump_key(MSG_DEBUG, "DPP: PBKDF2 key", key, key_len);
 
        if (dpp_pbkdf2(data.prf_hash_len, key, key_len, data.salt, 64, 1000,