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[Bluez,v4,0/4] Check the signature of att packets

Message ID 20200407085610.231013-1-apusaka@google.com
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Series Check the signature of att packets | expand

Message

Archie Pusaka April 7, 2020, 8:56 a.m. UTC 
From: Archie Pusaka <apusaka@chromium.org>

According to bluetooth spec Ver 5.1, Vol 3, Part C (GAP), 10.4.2
A device receiving signed data shall authenticate it by performing
the Signing Algorithm. The signed data shall be authenticated by
performing the Signing Algorithm where m is the Data PDU to be
authenticated, k is the stored CSRK and the SignCounter is the
received counter value. If the MAC computed by the Signing
Algorithm does not match the received MAC, the verification fails
and the Host shall ignore the received Data PDU.

Currently bluez ignore the signature of received signed att
packets, as the function bt_crypto_sign_att() only generates the
signature, and not actually make any check about the genuineness
of the signature itself.

This patch also fix a wrong boolean condition which prevents
handle_signed() to be called.

Tested to pass these BT certification test
SM/MAS/SIGN/BV-03-C
SM/MAS/SIGN/BI-01-C

Changes in v4:
- Fix wrong variable assignment
- Fixing test-gatt.c

Changes in v3:
- Add check for the case where pdu_len < ATT_SIGN_LEN
- Add unit test
- Separate into three patches

Changes in v2:
- Move the signature verification part to crypto.c
- Attempt not to copy the whole pdu while verifying the signature
  by not separating the opcode from the rest of pdu too early, so
  we don't have to rejoin them later.

Archie Pusaka (4):
  shared/crypto: Add bt_crypto_verify_att_sign
  unit/test-crypto: test for bt_crypto_verify_att_sign
  shared/att: Check the signature of att packets
  unit/test-gatt: Fix unknown request with signed bit

 src/shared/att.c    | 25 +++++++++----------
 src/shared/crypto.c | 28 +++++++++++++++++++--
 src/shared/crypto.h |  2 ++
 unit/test-crypto.c  | 59 +++++++++++++++++++++++++++++++++++++++++++++
 unit/test-gatt.c    | 32 ++++++++++++++++++++----
 5 files changed, 126 insertions(+), 20 deletions(-)