From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Brian Delwiche <delwiche@google.com>
Date: Tue, 3 Oct 2023 21:27:49 +0000
Subject: [PATCH] Fix timing attack in BTM_BleVerifySignature

BTM_BleVerifySignature uses a stock memcmp, allowing signature contents
to be deduced through a side-channel attack.

Change to CRYPTO_memcmp, which is hardened against this attack, to
eliminate this attack.

Bug: 274478807
Test: atest bluetooth_test_gd_unit
Tag: #security
Ignore-AOSP-First: Security
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:fcd1c44f7c4bf431dd6a6902d74c045174bd00ce)
Merged-In: I41a9b586d663d2ad4694222ae451d2d30a428a3c
Change-Id: I41a9b586d663d2ad4694222ae451d2d30a428a3c
---
 main/Android.bp      | 1 +
 stack/Android.bp     | 1 +
 stack/btm/btm_ble.cc | 3 ++-
 3 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/main/Android.bp b/main/Android.bp
index 9dc5a9866..35df9e6d4 100644
--- a/main/Android.bp
+++ b/main/Android.bp
@@ -48,6 +48,7 @@ cc_library_shared {
         "libutils",
         "libtinyxml2",
         "libz",
+        "libcrypto",
     ],
     static_libs: [
         "libbt-sbc-decoder",
diff --git a/stack/Android.bp b/stack/Android.bp
index 5cb567895..dd0f934f3 100644
--- a/stack/Android.bp
+++ b/stack/Android.bp
@@ -176,6 +176,7 @@ cc_library_static {
     shared_libs: [
         "libcutils",
         "liblog",
+        "libcrypto",
     ],
     required: [
         "libldacBT_enc",
diff --git a/stack/btm/btm_ble.cc b/stack/btm/btm_ble.cc
index 3a67f75ba..b8dfba239 100644
--- a/stack/btm/btm_ble.cc
+++ b/stack/btm/btm_ble.cc
@@ -41,6 +41,7 @@
 #include "hcimsgs.h"
 #include "log/log.h"
 #include "l2c_int.h"
+#include "openssl/mem.h"
 #include "osi/include/log.h"
 #include "osi/include/osi.h"
 #include "smp_api.h"
@@ -2235,7 +2236,7 @@ bool BTM_BleVerifySignature(const RawAddress& bd_addr, uint8_t* p_orig,
 
     if (aes_cipher_msg_auth_code(p_rec->ble.keys.pcsrk, p_orig, len,
                                  BTM_CMAC_TLEN_SIZE, p_mac)) {
-      if (memcmp(p_mac, p_comp, BTM_CMAC_TLEN_SIZE) == 0) {
+      if (CRYPTO_memcmp(p_mac, p_comp, BTM_CMAC_TLEN_SIZE) == 0) {
         btm_ble_increment_sign_ctr(bd_addr, false);
         verified = true;
       }