EAP-pwd: Fix some interoperability issues

The changes are:

  1. the word "and" in the hunting-and-pecking string passed to the KDF
     should be capitalized.
  2. the primebitlen used in the KDF should be a short not an int.
  3. the computation of MK in hostap is based on an older version of the
     draft and is not the way it's specified in the RFC.
  4. the group being passed into computation of the Commit was not in
     network order.

diff --git a/src/eap_common/eap_pwd_common.c b/src/eap_common/eap_pwd_common.c
index 5cd0a943692365991180ae1114448a6f27958452..c24b146cf894eb73fee9d77552444803bd73fd42 100644 (file)
--- a/src/eap_common/eap_pwd_common.c
+++ b/src/eap_common/eap_pwd_common.c
@@ -184,8 +184,8 @@ int compute_password_element(EAP_PWD_group *grp, u16 num,
                BN_bin2bn(pwe_digest, SHA256_DIGEST_LENGTH, rnd);
 
                eap_pwd_kdf(pwe_digest, SHA256_DIGEST_LENGTH,
-                           (unsigned char *) "EAP-pwd Hunting and Pecking",
-                           os_strlen("EAP-pwd Hunting and Pecking"),
+                           (unsigned char *) "EAP-pwd Hunting And Pecking",
+                           os_strlen("EAP-pwd Hunting And Pecking"),
                            prfbuf, primebitlen);
 
                BN_bin2bn(prfbuf, primebytelen, x_candidate);
@@ -264,22 +264,16 @@ int compute_password_element(EAP_PWD_group *grp, u16 num,
 
 
 int compute_keys(EAP_PWD_group *grp, BN_CTX *bnctx, BIGNUM *k,
-                EC_POINT *server_element, EC_POINT *peer_element,
-                BIGNUM *server_scalar, BIGNUM *peer_scalar, u32 *ciphersuite,
-                u8 *msk, u8 *emsk)
+                BIGNUM *peer_scalar, BIGNUM *server_scalar,
+                u8 *commit_peer, u8 *commit_server,
+                u32 *ciphersuite, u8 *msk, u8 *emsk)
 {
-       BIGNUM *scalar_sum, *x;
-       EC_POINT *element_sum;
        HMAC_CTX ctx;
        u8 mk[SHA256_DIGEST_LENGTH], *cruft;
        u8 session_id[SHA256_DIGEST_LENGTH + 1];
        u8 msk_emsk[EAP_MSK_LEN + EAP_EMSK_LEN];
-       int ret = -1;
 
-       if (((cruft = os_malloc(BN_num_bytes(grp->prime))) == NULL) ||
-           ((x = BN_new()) == NULL) ||
-           ((scalar_sum = BN_new()) == NULL) ||
-           ((element_sum = EC_POINT_new(grp->group)) == NULL))
+       if ((cruft = os_malloc(BN_num_bytes(grp->prime))) == NULL)
                return -1;
 
        /*
@@ -295,34 +289,13 @@ int compute_keys(EAP_PWD_group *grp, BN_CTX *bnctx, BIGNUM *k,
        H_Update(&ctx, cruft, BN_num_bytes(grp->order));
        H_Final(&ctx, &session_id[1]);
 
-       /*
-        * then compute MK = H(k | F(elem_p + elem_s) |
-        *                     (scal_p + scal_s) mod r)
-        */
+       /* then compute MK = H(k | commit-peer | commit-server) */
        H_Init(&ctx);
-
-       /* k */
        os_memset(cruft, 0, BN_num_bytes(grp->prime));
        BN_bn2bin(k, cruft);
        H_Update(&ctx, cruft, BN_num_bytes(grp->prime));
-
-       /* x = F(elem_p + elem_s) */
-       if ((!EC_POINT_add(grp->group, element_sum, server_element,
-                          peer_element, bnctx)) ||
-           (!EC_POINT_get_affine_coordinates_GFp(grp->group, element_sum, x,
-                                                 NULL, bnctx)))
-               goto fail;
-
-       os_memset(cruft, 0, BN_num_bytes(grp->prime));
-       BN_bn2bin(x, cruft);
-       H_Update(&ctx, cruft, BN_num_bytes(grp->prime));
-
-       /* (scal_p + scal_s) mod r */
-       BN_add(scalar_sum, server_scalar, peer_scalar);
-       BN_mod(scalar_sum, scalar_sum, grp->order, bnctx);
-       os_memset(cruft, 0, BN_num_bytes(grp->prime));
-       BN_bn2bin(scalar_sum, cruft);
-       H_Update(&ctx, cruft, BN_num_bytes(grp->order));
+       H_Update(&ctx, commit_peer, SHA256_DIGEST_LENGTH);
+       H_Update(&ctx, commit_server, SHA256_DIGEST_LENGTH);
        H_Final(&ctx, mk);
 
        /* stretch the mk with the session-id to get MSK | EMSK */
@@ -333,13 +306,7 @@ int compute_keys(EAP_PWD_group *grp, BN_CTX *bnctx, BIGNUM *k,
        os_memcpy(msk, msk_emsk, EAP_MSK_LEN);
        os_memcpy(emsk, msk_emsk + EAP_MSK_LEN, EAP_EMSK_LEN);
 
-       ret = 1;
-
-fail:
-       BN_free(x);
-       BN_free(scalar_sum);
-       EC_POINT_free(element_sum);
        os_free(cruft);
 
-       return ret;
+       return 1;
 }

diff --git a/src/eap_common/eap_pwd_common.h b/src/eap_common/eap_pwd_common.h
index 7389894a7c6236c574dee7aec636e57d1bd6e48f..971386d740898daa3bd239b4ff25cbfcb0396d82 100644 (file)
--- a/src/eap_common/eap_pwd_common.h
+++ b/src/eap_common/eap_pwd_common.h
@@ -70,8 +70,8 @@ struct eap_pwd_id {
 /* common routines */
 int compute_password_element(EAP_PWD_group *, u16, u8 *, int, u8 *, int, u8 *,
                             int, u8 *);
-int compute_keys(EAP_PWD_group *, BN_CTX *, BIGNUM *, EC_POINT *, EC_POINT *,
-                 BIGNUM *, BIGNUM *, u32 *, u8 *, u8 *);
+int compute_keys(EAP_PWD_group *, BN_CTX *, BIGNUM *, BIGNUM *, BIGNUM *,
+                u8 *, u8 *, u32 *, u8 *, u8 *);
 void H_Init(HMAC_CTX *);
 void H_Update(HMAC_CTX *, const u8 *, int);
 void H_Final(HMAC_CTX *, u8 *);

diff --git a/src/eap_peer/eap_pwd.c b/src/eap_peer/eap_pwd.c
index 3baca156876f3cc739b70b0818d1c1c3dc4e9405..e4705b7e4e74b7a5e3b01f31c1bdbbb5b8b8b63b 100644 (file)
--- a/src/eap_peer/eap_pwd.c
+++ b/src/eap_peer/eap_pwd.c
@@ -463,14 +463,16 @@ eap_pwd_perform_confirm_exchange(struct eap_sm *sm, struct eap_pwd_data *data,
        BIGNUM *x = NULL, *y = NULL;
        HMAC_CTX ctx;
        u32 cs;
+       u16 grp;
        u8 conf[SHA256_DIGEST_LENGTH], *cruft = NULL, *ptr;
 
        /*
         * first build up the ciphersuite which is group | random_function |
         *      prf
         */
+       grp = htons(data->group_num);
        ptr = (u8 *) &cs;
-       os_memcpy(ptr, &data->group_num, sizeof(u16));
+       os_memcpy(ptr, &grp, sizeof(u16));
        ptr += sizeof(u16);
        *ptr = EAP_PWD_DEFAULT_RAND_FUNC;
        ptr += sizeof(u8);
@@ -620,9 +622,9 @@ eap_pwd_perform_confirm_exchange(struct eap_sm *sm, struct eap_pwd_data *data,
        wpabuf_put_u8(resp, EAP_PWD_OPCODE_CONFIRM_EXCH);
        wpabuf_put_data(resp, conf, SHA256_DIGEST_LENGTH);
 
-       if (compute_keys(data->grp, data->bnctx, data->k, data->server_element,
-                        data->my_element, data->server_scalar,
-                        data->my_scalar, &cs, data->msk, data->emsk) < 0) {
+       if (compute_keys(data->grp, data->bnctx, data->k,
+                        data->my_scalar, data->server_scalar, conf, ptr,
+                        &cs, data->msk, data->emsk) < 0) {
                wpa_printf(MSG_INFO, "EAP-PWD (peer): unable to compute MSK | "
                           "EMSK");
                goto fin;

diff --git a/src/eap_server/eap_server_pwd.c b/src/eap_server/eap_server_pwd.c
index 512817b6fdea6cb707d9e8515bdd5f39c08a2df5..dd2557a83e235a19e02d23f5114193e50853d0fa 100644 (file)
--- a/src/eap_server/eap_server_pwd.c
+++ b/src/eap_server/eap_server_pwd.c
@@ -40,6 +40,8 @@ struct eap_pwd_data {
        EC_POINT *my_element;
        EC_POINT *peer_element;
 
+       u8 my_confirm[SHA256_DIGEST_LENGTH];
+
        u8 msk[EAP_MSK_LEN];
        u8 emsk[EAP_EMSK_LEN];
 
@@ -286,6 +288,7 @@ eap_pwd_build_confirm_req(struct eap_sm *sm, struct eap_pwd_data *data, u8 id)
        BIGNUM *x = NULL, *y = NULL;
        HMAC_CTX ctx;
        u8 conf[SHA256_DIGEST_LENGTH], *cruft = NULL, *ptr;
+       u16 grp;
 
        wpa_printf(MSG_DEBUG, "EAP-pwd: Confirm/Request");
 
@@ -356,9 +359,10 @@ eap_pwd_build_confirm_req(struct eap_sm *sm, struct eap_pwd_data *data, u8 id)
        H_Update(&ctx, cruft, BN_num_bytes(data->grp->order));
 
        /* ciphersuite */
+       grp = htons(data->group_num);
        os_memset(cruft, 0, BN_num_bytes(data->grp->prime));
        ptr = cruft;
-       os_memcpy(ptr, &data->group_num, sizeof(u16));
+       os_memcpy(ptr, &grp, sizeof(u16));
        ptr += sizeof(u16);
        *ptr = EAP_PWD_DEFAULT_RAND_FUNC;
        ptr += sizeof(u8);
@@ -368,6 +372,7 @@ eap_pwd_build_confirm_req(struct eap_sm *sm, struct eap_pwd_data *data, u8 id)
 
        /* all done with the random function */
        H_Final(&ctx, conf);
+       os_memcpy(data->my_confirm, conf, SHA256_DIGEST_LENGTH);
 
        req = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PWD,
                            sizeof(struct eap_pwd_hdr) + SHA256_DIGEST_LENGTH,
@@ -617,11 +622,13 @@ eap_pwd_process_confirm_resp(struct eap_sm *sm, struct eap_pwd_data *data,
        BIGNUM *x = NULL, *y = NULL;
        HMAC_CTX ctx;
        u32 cs;
+       u16 grp;
        u8 conf[SHA256_DIGEST_LENGTH], *cruft = NULL, *ptr;
 
        /* build up the ciphersuite: group | random_function | prf */
+       grp = htons(data->group_num);
        ptr = (u8 *) &cs;
-       os_memcpy(ptr, &data->group_num, sizeof(u16));
+       os_memcpy(ptr, &grp, sizeof(u16));
        ptr += sizeof(u16);
        *ptr = EAP_PWD_DEFAULT_RAND_FUNC;
        ptr += sizeof(u8);
@@ -701,9 +708,9 @@ eap_pwd_process_confirm_resp(struct eap_sm *sm, struct eap_pwd_data *data,
        }
 
        wpa_printf(MSG_DEBUG, "EAP-pwd (server): confirm verified");
-       if (compute_keys(data->grp, data->bnctx, data->k, data->my_element,
-                        data->peer_element, data->my_scalar,
-                        data->peer_scalar, &cs, data->msk, data->emsk) < 0)
+       if (compute_keys(data->grp, data->bnctx, data->k,
+                        data->peer_scalar, data->my_scalar, conf,
+                        data->my_confirm, &cs, data->msk, data->emsk) < 0)
                eap_pwd_state(data, FAILURE);
        else
                eap_pwd_state(data, SUCCESS);