From 2307347070e40f9106dc3e3ee3b8984e698b52c4 Mon Sep 17 00:00:00 2001
From: basil00 <basil@reqrypt.org>
Date: Fri, 8 Mar 2019 09:24:31 +0800
Subject: [PATCH] Use C-string-friendly chars for filter objects.

---
 dll/windivert_helper.c | 65 +++++++++++++++++++++++++++++++++++-------
 dll/windivert_shared.c | 15 ++++++++--
 2 files changed, 67 insertions(+), 13 deletions(-)

diff --git a/dll/windivert_helper.c b/dll/windivert_helper.c
index 4bec8e0..3355433 100644
--- a/dll/windivert_helper.c
+++ b/dll/windivert_helper.c
@@ -3220,6 +3220,50 @@ static char WinDivertGetChar(PWINDIVERT_STREAM stream)
     return c;
 }
 
+/*
+ * Decode a digit.
+ */
+static BOOL WinDivertDecodeDigit(char c, UINT8 *digit, BOOL *final)
+{
+    if (c >= '0' && c <= '9')
+    {
+        *digit = c - '0';
+        *final = FALSE;
+        return TRUE;
+    }
+    if (c >= 'A' && c <= 'V')
+    {
+        *digit = c - 'A' + 10;
+        *final = FALSE;
+        return TRUE;
+    }
+    if (c >= 'W' && c <= 'Z')
+    {
+        *digit = c - 'W';
+        *final = TRUE;
+        return TRUE;
+    }
+    if (c >= 'a' && c <= 'z')
+    {
+        *digit = c - 'a' + 4;
+        *final = TRUE;
+        return TRUE;
+    }
+    if (c == '+')
+    {
+        *digit = 30;
+        *final = TRUE;
+        return TRUE;
+    }
+    if (c == '=')
+    {
+        *digit = 31;
+        *final = TRUE;
+        return TRUE;
+    }
+    return FALSE;
+}
+
 /*
  * Deserialize a number.
  */
@@ -3227,7 +3271,10 @@ static BOOL WinDivertDeserializeNumber(PWINDIVERT_STREAM stream, UINT max_len,
     UINT32 *result)
 {
     UINT32 i, val = 0;
+    UINT8 digit;
+    BOOL final;
     char c;
+
     for (i = 0; i < max_len; i++)
     {
         if ((val & 0xF8000000) != 0)
@@ -3236,20 +3283,16 @@ static BOOL WinDivertDeserializeNumber(PWINDIVERT_STREAM stream, UINT max_len,
         }
         val <<= 5;
         c = WinDivertGetChar(stream);
-        if (c >= '!' && c <= '!' + 31)
-        {
-            val += (UINT32)(c - '!');
-        }
-        else if (c >= '!' + 32 && c <= '!' + 64)
-        {
-            val += (UINT32)(c - '!' - 32);
-            *result = val;
-            return TRUE;
-        }
-        else
+        if (!WinDivertDecodeDigit(c, &digit, &final))
         {
             return FALSE;
         }
+        val += digit;
+        if (final)
+        {
+            *result = val;
+            return TRUE;
+        }
     }
     return FALSE;
 }
diff --git a/dll/windivert_shared.c b/dll/windivert_shared.c
index 43e0a94..9f1b190 100644
--- a/dll/windivert_shared.c
+++ b/dll/windivert_shared.c
@@ -143,6 +143,16 @@ static void WinDivertPutNul(PWINDIVERT_STREAM stream)
     }
 }
 
+/*
+ * Encode a digit.
+ */
+static char WinDivertEncodeDigit(UINT8 dig, BOOL final)
+{
+    static const char windivert_digits[64+1] =
+        "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz+=";
+    return windivert_digits[(dig & 0x1F) + (final? 32: 0)];
+}
+
 /*
  * Serialize a number.
  */
@@ -150,6 +160,7 @@ static void WinDivertSerializeNumber(PWINDIVERT_STREAM stream, UINT32 val)
 {
     UINT64 mask = 0x00000007C0000000ull;
     UINT dig = 6;
+    UINT8 digit;
     UINT64 val64 = (UINT64)val;
     BOOL final;
 
@@ -161,8 +172,8 @@ static void WinDivertSerializeNumber(PWINDIVERT_STREAM stream, UINT32 val)
     while (TRUE)
     {
         final = (dig == 0);
-        WinDivertPutChar(stream, '!' + (char)((mask & val64) >> (5 * dig)) +
-            (final? 32: 0));
+        digit = (UINT8)((mask & val64) >> (5 * dig));
+        WinDivertPutChar(stream, WinDivertEncodeDigit(digit, final));
         if (final)
         {
             break;