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GAS server: Fix request frame length validation (CID 68098)

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There seemed to be an off-by-one error in the validation of GAS request
frames. If a Public Action frame without the Action code field would
have reached this function, the length could have been passed as
(size_t) -1 which would likely have resulted in a crash due to reading
beyond the buffer. However, it looks like such frame would not be
delivered to hostapd at least with mac80211-based drivers. Anyway, this
function better be more careful with length validation should some other
driver end up reporting invalid Action frames.

In addition, the Action code field is in a fixed location, so the
IEEE80211_HDRLEN can be used here to clean up bounds checking to avoid
false reports from static analyzer.

Signed-off-by: Jouni Malinen <j@w1.fi>
This commit is contained in:
Jouni Malinen 2014-06-12 22:10:43 +03:00
parent 6ec64f3ec8
commit 062833c67c
1 changed files with 3 additions and 5 deletions
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8
src/ap/gas_serv.c
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@ -1213,13 +1213,11 @@ static void gas_serv_rx_public_action(void *ctx, const u8 *buf, size_t len,
{ {
struct hostapd_data *hapd = ctx; struct hostapd_data *hapd = ctx;
const struct ieee80211_mgmt *mgmt; const struct ieee80211_mgmt *mgmt;
size_t hdr_len;
const u8 *sa, *data; const u8 *sa, *data;
int prot; int prot;
mgmt = (const struct ieee80211_mgmt *) buf; mgmt = (const struct ieee80211_mgmt *) buf;
hdr_len = (const u8 *) &mgmt->u.action.u.vs_public_action.action - buf; if (len < IEEE80211_HDRLEN + 2)
if (hdr_len > len)
return; return;
if (mgmt->u.action.category != WLAN_ACTION_PUBLIC && if (mgmt->u.action.category != WLAN_ACTION_PUBLIC &&
mgmt->u.action.category != WLAN_ACTION_PROTECTED_DUAL) mgmt->u.action.category != WLAN_ACTION_PROTECTED_DUAL)
@ -1231,8 +1229,8 @@ static void gas_serv_rx_public_action(void *ctx, const u8 *buf, size_t len,
*/ */
prot = mgmt->u.action.category == WLAN_ACTION_PROTECTED_DUAL; prot = mgmt->u.action.category == WLAN_ACTION_PROTECTED_DUAL;
sa = mgmt->sa; sa = mgmt->sa;
len -= hdr_len; len -= IEEE80211_HDRLEN + 1;
data = &mgmt->u.action.u.public_action.action; data = buf + IEEE80211_HDRLEN + 1;
switch (data[0]) { switch (data[0]) {
case WLAN_PA_GAS_INITIAL_REQ: case WLAN_PA_GAS_INITIAL_REQ:
gas_serv_rx_gas_initial_req(hapd, sa, data + 1, len - 1, prot); gas_serv_rx_gas_initial_req(hapd, sa, data + 1, len - 1, prot);