RNG_SystemRNG should fail rather than falling back on rng_systemFromNoise

patches/nss-rtlgenrandom.patch

Index: patches/nss-rtlgenrandom.patch
===================================================================
--- patches/nss-rtlgenrandom.patch	(revision 0)
+++ patches/nss-rtlgenrandom.patch	(revision 0)
@@ -0,0 +1,110 @@
+diff --git a/lib/freebl/win_rand.c b/lib/freebl/win_rand.c
+--- a/lib/freebl/win_rand.c
++++ b/lib/freebl/win_rand.c
+@@ -362,102 +362,37 @@ void RNG_FileForRNG(const char *filename
+     }
+ 
+     nBytes = RNG_GetNoise(buffer, 20);  // get up to 20 bytes
+     RNG_RandomUpdate(buffer, nBytes);
+ }
+ 
+ 
+ /*
+- * CryptoAPI requires Windows NT 4.0 or Windows 95 OSR2 and later.
+- * Until we drop support for Windows 95, we need to emulate some
+- * definitions and declarations in <wincrypt.h> and look up the
+- * functions in advapi32.dll at run time.
+- */
+-
+-#ifndef WIN64
+-typedef unsigned long HCRYPTPROV;
+-#endif
+-
+-#define CRYPT_VERIFYCONTEXT 0xF0000000
+-
+-#define PROV_RSA_FULL 1
+-
+-typedef BOOL
+-(WINAPI *CryptAcquireContextAFn)(
+-    HCRYPTPROV *phProv,
+-    LPCSTR pszContainer,
+-    LPCSTR pszProvider,
+-    DWORD dwProvType,
+-    DWORD dwFlags);
+-
+-typedef BOOL
+-(WINAPI *CryptReleaseContextFn)(
+-    HCRYPTPROV hProv,
+-    DWORD dwFlags);
+-
+-typedef BOOL
+-(WINAPI *CryptGenRandomFn)(
+-    HCRYPTPROV hProv,
+-    DWORD dwLen,
+-    BYTE *pbBuffer);
+-
+-/*
+  * Windows XP and Windows Server 2003 and later have RtlGenRandom,
+  * which must be looked up by the name SystemFunction036.
+  */
+ typedef BOOLEAN
+ (APIENTRY *RtlGenRandomFn)(
+     PVOID RandomBuffer,
+     ULONG RandomBufferLength);
+ 
+ size_t RNG_SystemRNG(void *dest, size_t maxLen)
+ {
+     HMODULE hModule;
+     RtlGenRandomFn pRtlGenRandom;
+-    CryptAcquireContextAFn pCryptAcquireContextA;
+-    CryptReleaseContextFn pCryptReleaseContext;
+-    CryptGenRandomFn pCryptGenRandom;
+-    HCRYPTPROV hCryptProv;
+     size_t bytes = 0;
+ 
+     usedWindowsPRNG = PR_FALSE;
+     hModule = LoadLibrary("advapi32.dll");
+     if (hModule == NULL) {
+-	return rng_systemFromNoise(dest,maxLen);
++	return bytes;
+     }
+     pRtlGenRandom = (RtlGenRandomFn)
+ 	GetProcAddress(hModule, "SystemFunction036");
+-    if (pRtlGenRandom) {
+-	if (pRtlGenRandom(dest, maxLen)) {
+-	    bytes = maxLen;
+-	    usedWindowsPRNG = PR_TRUE;
+-	} else {
+-	    bytes = rng_systemFromNoise(dest,maxLen);
+-	}
+-	goto done;
++    if (pRtlGenRandom && pRtlGenRandom(dest, maxLen)) {
++	bytes = maxLen;
++	usedWindowsPRNG = PR_TRUE;
+     }
+-    pCryptAcquireContextA = (CryptAcquireContextAFn)
+-	GetProcAddress(hModule, "CryptAcquireContextA");
+-    pCryptReleaseContext = (CryptReleaseContextFn)
+-	GetProcAddress(hModule, "CryptReleaseContext");
+-    pCryptGenRandom = (CryptGenRandomFn)
+-	GetProcAddress(hModule, "CryptGenRandom");
+-    if (!pCryptAcquireContextA || !pCryptReleaseContext || !pCryptGenRandom) {
+-	bytes = rng_systemFromNoise(dest,maxLen);
+-	goto done;
+-    }
+-    if (pCryptAcquireContextA(&hCryptProv, NULL, NULL,
+-	PROV_RSA_FULL, CRYPT_VERIFYCONTEXT)) {
+-	if (pCryptGenRandom(hCryptProv, maxLen, dest)) {
+-	    bytes = maxLen;
+-	    usedWindowsPRNG = PR_TRUE;
+-	}
+-	pCryptReleaseContext(hCryptProv, 0);
+-    }
+-    if (bytes == 0) {
+-	bytes = rng_systemFromNoise(dest,maxLen);
+-    }
+-done:
+     FreeLibrary(hModule);
+     return bytes;
+ }
+ #endif  /* is XP_WIN */