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 70f149b9a1/examples/examples_util.h (L19-L28)

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

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

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

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>
 )