crypt32: Fail if MultiByteToWideChar converts 0 characters.

dlls/crypt32/str.c

@@ -455,7 +455,6 @@ BOOL WINAPI CertStrToNameA(DWORD dwCertEncodingType, LPCSTR pszX500,
  DWORD dwStrType, void *pvReserved, BYTE *pbEncoded, DWORD *pcbEncoded,
  LPCSTR *ppszError)
 {
-    LPWSTR x500, errorStr;
     BOOL ret;
     int len;
 
@@ -464,12 +463,16 @@ BOOL WINAPI CertStrToNameA(DWORD dwCertEncodingType, LPCSTR pszX500,
      ppszError);
 
     len = MultiByteToWideChar(CP_ACP, 0, pszX500, -1, NULL, 0);
-    x500 = CryptMemAlloc(len * sizeof(WCHAR));
-    if (x500)
+    if (len)
+    {
+        LPWSTR x500, errorStr;
+
+        if ((x500 = CryptMemAlloc(len * sizeof(WCHAR))))
         {
             MultiByteToWideChar(CP_ACP, 0, pszX500, -1, x500, len);
-        ret = CertStrToNameW(dwCertEncodingType, x500, dwStrType, pvReserved,
-         pbEncoded, pcbEncoded, ppszError ? (LPCWSTR *)&errorStr : NULL);
+            ret = CertStrToNameW(dwCertEncodingType, x500, dwStrType,
+             pvReserved, pbEncoded, pcbEncoded,
+             ppszError ? (LPCWSTR *)&errorStr : NULL);
             if (ppszError)
             {
                 DWORD i;
@@ -481,7 +484,18 @@ BOOL WINAPI CertStrToNameA(DWORD dwCertEncodingType, LPCSTR pszX500,
             CryptMemFree(x500);
         }
         else
+        {
+            SetLastError(ERROR_OUTOFMEMORY);
             ret = FALSE;
+        }
+    }
+    else
+    {
+        SetLastError(CRYPT_E_INVALID_X500_STRING);
+        if (ppszError)
+            *ppszError = pszX500;
+        ret = FALSE;
+    }
     return ret;
 }