AP MLD: Fix STA Info field parsing in Basic Multi-Link element

The STA Info field is supposed to be extensible. Instead of determined
the length of known components and only accepting that length, make sure
that there is sufficient octets in the received field for whatever we
are parsing and ignore any potential unknown extensions at the end.

In addition, simplify some of the bounds checking by using pointers to
the end of the subelement and the MLE itself instead of trying to track
the remaining lengths and a pointer to the current location
consistently.

Fixes: 5f5db9366cde ("AP: MLO: Process Multi-Link element from (Re)Association Request frame")
Signed-off-by: Jouni Malinen <quic_jouni@quicinc.com>

diff --git a/src/ap/ieee802_11_eht.c b/src/ap/ieee802_11_eht.c
index 2812150260d16331d624dacec36e77570167845c..577fa563b0481283d108399c461b5c3ec16a573d 100644 (file)
--- a/src/ap/ieee802_11_eht.c
+++ b/src/ap/ieee802_11_eht.c
@@ -1166,6 +1166,7 @@ u16 hostapd_process_ml_assoc_req(struct hostapd_data *hapd,
        const u8 *pos, *end;
        int ret = -1;
        u16 ml_control;
+       const u8 *ml_end;
 
        mlbuf = ieee802_11_defrag(elems->basic_mle, elems->basic_mle_len, true);
        if (!mlbuf)
@@ -1173,6 +1174,7 @@ u16 hostapd_process_ml_assoc_req(struct hostapd_data *hapd,
 
        ml = wpabuf_head(mlbuf);
        ml_len = wpabuf_len(mlbuf);
+       ml_end = ((const u8 *) ml) + ml_len;
 
        ml_control = le_to_host16(ml->ml_control);
        if ((ml_control & MULTI_LINK_CONTROL_TYPE_MASK) !=
@@ -1275,19 +1277,19 @@ u16 hostapd_process_ml_assoc_req(struct hostapd_data *hapd,
        /* Parse the Link Info field that starts after the end of the variable
         * length Common Info field. */
        pos = end;
-       ml_len -= sizeof(*ml) + common_info->len;
-       while (ml_len > 2) {
+       while (ml_end - pos > 2) {
                size_t sub_elem_len = *(pos + 1);
                size_t sta_info_len;
                u16 control;
+               const u8 *sub_elem_end;
 
                wpa_printf(MSG_DEBUG, "MLD: sub element len=%zu",
                           sub_elem_len);
 
-               if (2 + sub_elem_len > ml_len) {
+               if (2 + sub_elem_len > (size_t) (ml_end - pos)) {
                        wpa_printf(MSG_DEBUG,
                                   "MLD: Invalid link info len: %zu %zu",
-                                  2 + sub_elem_len, ml_len);
+                                  2 + sub_elem_len, ml_end - pos);
                        goto out;
                }
 
@@ -1296,7 +1298,6 @@ u16 hostapd_process_ml_assoc_req(struct hostapd_data *hapd,
                                   "MLD: Skip vendor specific subelement");
 
                        pos += 2 + sub_elem_len;
-                       ml_len -= 2 + sub_elem_len;
                        continue;
                }
 
@@ -1305,16 +1306,15 @@ u16 hostapd_process_ml_assoc_req(struct hostapd_data *hapd,
                                   "MLD: Skip unknown Multi-Link element subelement ID=%u",
                                   *pos);
                        pos += 2 + sub_elem_len;
-                       ml_len -= 2 + sub_elem_len;
                        continue;
                }
 
                /* Skip the subelement ID and the length */
                pos += 2;
-               ml_len -= 2;
+               sub_elem_end = pos + sub_elem_len;
 
                /* Get the station control field */
-               if (sub_elem_len < 2) {
+               if (sub_elem_end - pos < 2) {
                        wpa_printf(MSG_DEBUG,
                                   "MLD: Too short Per-STA Profile subelement");
                        goto out;
@@ -1323,8 +1323,6 @@ u16 hostapd_process_ml_assoc_req(struct hostapd_data *hapd,
                link_info = &info->links[control &
                                         EHT_PER_STA_CTRL_LINK_ID_MSK];
                pos += 2;
-               ml_len -= 2;
-               sub_elem_len -= 2;
 
                if (!(control & EHT_PER_STA_CTRL_COMPLETE_PROFILE_MSK)) {
                        wpa_printf(MSG_DEBUG,
@@ -1357,15 +1355,19 @@ u16 hostapd_process_ml_assoc_req(struct hostapd_data *hapd,
 
                sta_info_len += link_info->nstr_bitmap_len;
 
-               if (sta_info_len > ml_len || sta_info_len != *pos ||
-                   sta_info_len > sub_elem_len) {
+               if (sta_info_len > (size_t) (sub_elem_end - pos) ||
+                   sta_info_len > *pos ||
+                   *pos > sub_elem_end - pos ||
+                   sta_info_len > (size_t) (sub_elem_end - pos)) {
                        wpa_printf(MSG_DEBUG, "MLD: Invalid STA Info length");
                        goto out;
                }
 
+               sta_info_len = *pos;
+               end = pos + sta_info_len;
+
                /* skip the length */
                pos++;
-               ml_len--;
 
                /* get the link address */
                os_memcpy(link_info->peer_addr, pos, ETH_ALEN);
@@ -1375,27 +1377,20 @@ u16 hostapd_process_ml_assoc_req(struct hostapd_data *hapd,
                           MAC2STR(link_info->peer_addr));
 
                pos += ETH_ALEN;
-               ml_len -= ETH_ALEN;
 
                /* Get the NSTR bitmap */
                if (link_info->nstr_bitmap_len) {
                        os_memcpy(link_info->nstr_bitmap, pos,
                                  link_info->nstr_bitmap_len);
                        pos += link_info->nstr_bitmap_len;
-                       ml_len -= link_info->nstr_bitmap_len;
                }
 
-               sub_elem_len -= sta_info_len;
-
-               wpa_printf(MSG_DEBUG, "MLD: STA Profile len=%zu", sub_elem_len);
-               if (sub_elem_len > ml_len)
-                       goto out;
+               pos = end;
 
-               if (sub_elem_len > 2)
+               if (sub_elem_end - pos >= 2)
                        link_info->capability = WPA_GET_LE16(pos);
 
-               pos += sub_elem_len;
-               ml_len -= sub_elem_len;
+               pos = sub_elem_end;
 
                wpa_printf(MSG_DEBUG, "MLD: link ctrl=0x%x, " MACSTR
                           ", nstr bitmap len=%u",
@@ -1405,12 +1400,6 @@ u16 hostapd_process_ml_assoc_req(struct hostapd_data *hapd,
                link_info->valid = true;
        }
 
-       if (ml_len) {
-               wpa_printf(MSG_DEBUG, "MLD: %zu bytes left after parsing. fail",
-                          ml_len);
-               goto out;
-       }
-
        ret = hostapd_mld_validate_assoc_info(hapd, sta);
 out:
        wpabuf_free(mlbuf);