diff options
Diffstat (limited to 'net/wireless/util.c')
| -rw-r--r-- | net/wireless/util.c | 52 |
1 files changed, 50 insertions, 2 deletions
diff --git a/net/wireless/util.c b/net/wireless/util.c index ed868c0f7ca8..1ad5a6bdfd75 100644 --- a/net/wireless/util.c +++ b/net/wireless/util.c @@ -820,6 +820,52 @@ bool ieee80211_is_valid_amsdu(struct sk_buff *skb, u8 mesh_hdr) } EXPORT_SYMBOL(ieee80211_is_valid_amsdu); + +/* + * Detects if an MSDU frame was maliciously converted into an A-MSDU + * frame by an adversary. This is done by parsing the received frame + * as if it were a regular MSDU, even though the A-MSDU flag is set. + * + * For non-mesh interfaces, detection involves checking whether the + * payload, when interpreted as an MSDU, begins with a valid RFC1042 + * header. This is done by comparing the A-MSDU subheader's destination + * address to the start of the RFC1042 header. + * + * For mesh interfaces, the MSDU includes a 6-byte Mesh Control field + * and an optional variable-length Mesh Address Extension field before + * the RFC1042 header. The position of the RFC1042 header must therefore + * be calculated based on the mesh header length. + * + * Since this function intentionally parses an A-MSDU frame as an MSDU, + * it only assumes that the A-MSDU subframe header is present, and + * beyond this it performs its own bounds checks under the assumption + * that the frame is instead parsed as a non-aggregated MSDU. + */ +static bool +is_amsdu_aggregation_attack(struct ethhdr *eth, struct sk_buff *skb, + enum nl80211_iftype iftype) +{ + int offset; + + /* Non-mesh case can be directly compared */ + if (iftype != NL80211_IFTYPE_MESH_POINT) + return ether_addr_equal(eth->h_dest, rfc1042_header); + + offset = __ieee80211_get_mesh_hdrlen(eth->h_dest[0]); + if (offset == 6) { + /* Mesh case with empty address extension field */ + return ether_addr_equal(eth->h_source, rfc1042_header); + } else if (offset + ETH_ALEN <= skb->len) { + /* Mesh case with non-empty address extension field */ + u8 temp[ETH_ALEN]; + + skb_copy_bits(skb, offset, temp, ETH_ALEN); + return ether_addr_equal(temp, rfc1042_header); + } + + return false; +} + void ieee80211_amsdu_to_8023s(struct sk_buff *skb, struct sk_buff_head *list, const u8 *addr, enum nl80211_iftype iftype, const unsigned int extra_headroom, @@ -861,8 +907,10 @@ void ieee80211_amsdu_to_8023s(struct sk_buff *skb, struct sk_buff_head *list, /* the last MSDU has no padding */ if (subframe_len > remaining) goto purge; - /* mitigate A-MSDU aggregation injection attacks */ - if (ether_addr_equal(hdr.eth.h_dest, rfc1042_header)) + /* mitigate A-MSDU aggregation injection attacks, to be + * checked when processing first subframe (offset == 0). + */ + if (offset == 0 && is_amsdu_aggregation_attack(&hdr.eth, skb, iftype)) goto purge; offset += sizeof(struct ethhdr); |