staging: rtl8723bs: fix WEP length underflow and OOB read in OnAuth()

Overview

In the Linux kernel, the following vulnerability has been resolved:

staging: rtl8723bs: fix WEP length underflow and OOB read in OnAuth()

OnAuth() has two bugs in the shared-key authentication path.

When the Privacy bit is set, rtw_wep_decrypt() is called without verifying that the frame is long enough to contain a valid WEP IV and ICV. Inside rtw_wep_decrypt(), length is computed as:

length = len - WLAN_HDR_A3_LEN - iv_len

and then passed as (length - 4) to crc32_le(). If len is less than WLAN_HDR_A3_LEN + iv_len + icv_len (32 bytes), length - 4 is negative and, after the implicit cast to size_t, causes crc32_le() to read far beyond the frame buffer. Add a minimum length check before accessing the IV field and calling the decryption path.

When processing a seq=3 response, rtw_get_ie() stores the Challenge Text IE length in ie_len, but the subsequent memcmp() always reads 128 bytes regardless of ie_len. IEEE 802.11 mandates a challenge text of exactly 128 bytes; reject any IE whose length field differs, matching the check already applied to OnAuthClient().

Affected

• Linux >= 554c0a3abf216c991c5ebddcdb2c08689ecd290b < 665e1ecb68b4e8419604e70a33f02d1c8b0222c6
• Linux >= 554c0a3abf216c991c5ebddcdb2c08689ecd290b < 87cccc2a767f17dcab71e3b9fe5ae29b5516c5ce
• Linux >= 554c0a3abf216c991c5ebddcdb2c08689ecd290b < c9000c93078e5c0a5a651b077c0ec92a4bc7d580
• Linux >= 554c0a3abf216c991c5ebddcdb2c08689ecd290b < 1f6c9d255bdda41216b6e34c96aa2b1abee0bb84
• Linux >= 554c0a3abf216c991c5ebddcdb2c08689ecd290b < 3e44a7665f3abd320a80d9c64ee4a93317041b8b
• Linux >= 554c0a3abf216c991c5ebddcdb2c08689ecd290b < 64ec4192d9c10e96922245d4a6747304cc76b19d
• Linux >= 554c0a3abf216c991c5ebddcdb2c08689ecd290b < d90b9f39f375c9826ef145605dfe97765d0ecb91
• Linux >= 554c0a3abf216c991c5ebddcdb2c08689ecd290b < a1fc19d61f661d47204f095b593de507884849f7
• Linux 4.12

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.