From 6b4bcc16234575108bb691c15c3532198d9bf98a Mon Sep 17 00:00:00 2001
From: David Gumberg <davidzgumberg@gmail.com>
Date: Thu, 1 May 2025 16:36:24 -0700
Subject: [PATCH] random: Use modern Windows randomness functions

The old randomness API has been deprecated and may be removed soon.[^1]

For reference on `BCryptGenRandom`, see: https://learn.microsoft.com/en-us/windows/win32/api/bcrypt/nf-bcrypt-bcryptgenrandom.

`STATUS_SUCCESS`[^2] gets defined here since including `ntstatus.h` is
more trouble than it's worth. [^3]

[^1]: https://learn.microsoft.com/en-us/windows/win32/api/wincrypt/nf-wincrypt-cryptacquirecontextw & https://learn.microsoft.com/en-us/windows/win32/api/wincrypt/nf-wincrypt-cryptgenrandom
[^2]: https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-erref/596a1078-e883-4972-9bbc-49e60bebca55
[^3]: See https://github.com/bitcoin-core/secp256k1/blob/70f149b9a1bf4ed3266f97774d0ae9577534bf40/examples/examples_util.h#L19-L28
---
 contrib/guix/symbol-check.py |  3 ++-
 src/kernel/CMakeLists.txt    |  1 +
 src/random.cpp               | 18 ++++++++----------
 src/util/CMakeLists.txt      |  1 +
 4 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/contrib/guix/symbol-check.py b/contrib/guix/symbol-check.py
index 9bb5322e170..bf102e911e6 100755
--- a/contrib/guix/symbol-check.py
+++ b/contrib/guix/symbol-check.py
@@ -153,7 +153,8 @@ MACHO_ALLOWED_LIBRARIES = {
 }
 
 PE_ALLOWED_LIBRARIES = {
-'ADVAPI32.dll', # security & registry
+'ADVAPI32.dll', # legacy security & registry
+'bcrypt.dll', # newer security and identity API
 'IPHLPAPI.DLL', # IP helper API
 'KERNEL32.dll', # win32 base APIs
 'msvcrt.dll', # C standard library for MSVC
diff --git a/src/kernel/CMakeLists.txt b/src/kernel/CMakeLists.txt
index b9f37969d37..52e91671dd0 100644
--- a/src/kernel/CMakeLists.txt
+++ b/src/kernel/CMakeLists.txt
@@ -87,6 +87,7 @@ target_link_libraries(bitcoinkernel
     bitcoin_crypto
     leveldb
     secp256k1
+    $<$<PLATFORM_ID:Windows>:bcrypt>
     $<TARGET_NAME_IF_EXISTS:USDT::headers>
   PUBLIC
     Boost::headers
diff --git a/src/random.cpp b/src/random.cpp
index fa3d8ec3f1e..bd17f6f590f 100644
--- a/src/random.cpp
+++ b/src/random.cpp
@@ -27,8 +27,7 @@
 #include <thread>
 
 #ifdef WIN32
-#include <windows.h>
-#include <wincrypt.h>
+#include <bcrypt.h>
 #else
 #include <fcntl.h>
 #include <sys/time.h>
@@ -287,16 +286,15 @@ void Strengthen(const unsigned char (&seed)[32], SteadyClock::duration dur, CSHA
 void GetOSRand(unsigned char *ent32)
 {
 #if defined(WIN32)
-    HCRYPTPROV hProvider;
-    int ret = CryptAcquireContextW(&hProvider, nullptr, nullptr, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
-    if (!ret) {
+    constexpr uint32_t STATUS_SUCCESS{0x00000000};
+    NTSTATUS status = BCryptGenRandom(/*hAlgorithm=*/NULL,
+                                      /*pbBuffer=*/ent32,
+                                      /*cbBuffer=*/NUM_OS_RANDOM_BYTES,
+                                      /*dwFlags=*/BCRYPT_USE_SYSTEM_PREFERRED_RNG);
+
+    if (status != STATUS_SUCCESS) {
         RandFailure();
     }
-    ret = CryptGenRandom(hProvider, NUM_OS_RANDOM_BYTES, ent32);
-    if (!ret) {
-        RandFailure();
-    }
-    CryptReleaseContext(hProvider, 0);
 #elif defined(HAVE_GETRANDOM)
     /* Linux. From the getrandom(2) man page:
      * "If the urandom source has been initialized, reads of up to 256 bytes
diff --git a/src/util/CMakeLists.txt b/src/util/CMakeLists.txt
index 4999dbf13f0..9953956f277 100644
--- a/src/util/CMakeLists.txt
+++ b/src/util/CMakeLists.txt
@@ -43,4 +43,5 @@ target_link_libraries(bitcoin_util
     bitcoin_crypto
     $<$<PLATFORM_ID:Windows>:ws2_32>
     $<$<PLATFORM_ID:Windows>:iphlpapi>
+    $<$<PLATFORM_ID:Windows>:bcrypt>
 )