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Bluetooth: RFCOMM: check the validity of received frame #74640

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Jun 25, 2024
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Bluetooth: RFCOMM: check the validity of received frame #74640

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33 changes: 22 additions & 11 deletions subsys/bluetooth/host/classic/rfcomm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1494,10 +1494,13 @@ static int rfcomm_recv(struct bt_l2cap_chan *chan, struct net_buf *buf)
{
struct bt_rfcomm_session *session = RFCOMM_SESSION(chan);
struct bt_rfcomm_hdr *hdr = (void *)buf->data;
struct bt_rfcomm_hdr_ext *hdr_ext = (void *)buf->data;
uint8_t dlci, frame_type, fcs, fcs_len;
uint16_t msg_len;
uint16_t hdr_len;

/* Need to consider FCS also*/
if (buf->len < (sizeof(*hdr) + 1)) {
if (buf->len < (sizeof(*hdr) + sizeof(fcs))) {
LOG_ERR("Too small RFCOMM Frame");
return 0;
}
Expand All @@ -1507,19 +1510,28 @@ static int rfcomm_recv(struct bt_l2cap_chan *chan, struct net_buf *buf)

LOG_DBG("session %p dlci %x type %x", session, dlci, frame_type);

fcs_len = (frame_type == BT_RFCOMM_UIH) ? BT_RFCOMM_FCS_LEN_UIH :
BT_RFCOMM_FCS_LEN_NON_UIH;
fcs = *(net_buf_tail(buf) - 1);
if (BT_RFCOMM_LEN_EXTENDED(hdr->length)) {
msg_len = BT_RFCOMM_GET_LEN_EXTENDED(hdr_ext->hdr.length, hdr_ext->second_length);
hdr_len = sizeof(*hdr_ext);
} else {
msg_len = BT_RFCOMM_GET_LEN(hdr->length);
hdr_len = sizeof(*hdr);
}

if (buf->len < (hdr_len + msg_len + sizeof(fcs))) {
LOG_ERR("Too small RFCOMM information (%d < %d)", buf->len,
hdr_len + msg_len + sizeof(fcs));
return 0;
}

fcs_len = (frame_type == BT_RFCOMM_UIH) ? BT_RFCOMM_FCS_LEN_UIH : hdr_len;
fcs = *(net_buf_tail(buf) - sizeof(fcs));
if (!rfcomm_check_fcs(fcs_len, buf->data, fcs)) {
LOG_ERR("FCS check failed");
return 0;
}

if (BT_RFCOMM_LEN_EXTENDED(hdr->length)) {
net_buf_pull(buf, sizeof(*hdr) + 1);
} else {
net_buf_pull(buf, sizeof(*hdr));
}
net_buf_pull(buf, hdr_len);

switch (frame_type) {
case BT_RFCOMM_SABM:
Expand All @@ -1529,8 +1541,7 @@ static int rfcomm_recv(struct bt_l2cap_chan *chan, struct net_buf *buf)
if (!dlci) {
rfcomm_handle_msg(session, buf);
} else {
rfcomm_handle_data(session, buf, dlci,
BT_RFCOMM_GET_PF(hdr->control));
rfcomm_handle_data(session, buf, dlci, BT_RFCOMM_GET_PF(hdr->control));
}
break;
case BT_RFCOMM_DISC:
Expand Down
20 changes: 13 additions & 7 deletions subsys/bluetooth/host/classic/rfcomm_internal.h
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Original file line number Diff line number Diff line change
Expand Up @@ -49,6 +49,11 @@ struct bt_rfcomm_hdr {
uint8_t length;
} __packed;

struct bt_rfcomm_hdr_ext {
struct bt_rfcomm_hdr hdr;
uint8_t second_length;
} __packed;

#define BT_RFCOMM_SABM 0x2f
#define BT_RFCOMM_UA 0x63
#define BT_RFCOMM_UIH 0xef
Expand Down Expand Up @@ -137,13 +142,14 @@ struct bt_rfcomm_rpn {
sizeof(struct bt_rfcomm_hdr) + 1 + (mtu) + \
BT_RFCOMM_FCS_SIZE)

#define BT_RFCOMM_GET_DLCI(addr) (((addr) & 0xfc) >> 2)
#define BT_RFCOMM_GET_FRAME_TYPE(ctrl) ((ctrl) & 0xef)
#define BT_RFCOMM_GET_MSG_TYPE(type) (((type) & 0xfc) >> 2)
#define BT_RFCOMM_GET_MSG_CR(type) (((type) & 0x02) >> 1)
#define BT_RFCOMM_GET_LEN(len) (((len) & 0xfe) >> 1)
#define BT_RFCOMM_GET_CHANNEL(dlci) ((dlci) >> 1)
#define BT_RFCOMM_GET_PF(ctrl) (((ctrl) & 0x10) >> 4)
#define BT_RFCOMM_GET_DLCI(addr) (((addr) & 0xfc) >> 2)
#define BT_RFCOMM_GET_FRAME_TYPE(ctrl) ((ctrl) & 0xef)
#define BT_RFCOMM_GET_MSG_TYPE(type) (((type) & 0xfc) >> 2)
#define BT_RFCOMM_GET_MSG_CR(type) (((type) & 0x02) >> 1)
#define BT_RFCOMM_GET_LEN(len) (((len) & 0xfe) >> 1)
#define BT_RFCOMM_GET_LEN_EXTENDED(first, second) ((((first) & 0xfe) >> 1) | ((second) << 7))
#define BT_RFCOMM_GET_CHANNEL(dlci) ((dlci) >> 1)
#define BT_RFCOMM_GET_PF(ctrl) (((ctrl) & 0x10) >> 4)

#define BT_RFCOMM_SET_ADDR(dlci, cr) ((((dlci) & 0x3f) << 2) | \
((cr) << 1) | 0x01)
Expand Down
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