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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Buffers.Binary;
using System.Diagnostics;
using System.Numerics;
using System.Runtime.CompilerServices;
namespace System.Net
{
internal static partial class IPv4AddressHelper
{
internal const long Invalid = -1;
private const long MaxIPv4Value = uint.MaxValue; // the native parser cannot handle MaxIPv4Value, only MaxIPv4Value - 1
private const int Octal = 8;
private const int Decimal = 10;
private const int Hex = 16;
private const int NumberOfLabels = 4;
[MethodImpl(MethodImplOptions.AggressiveInlining)]
internal static ushort ToUShort<TChar>(TChar value)
where TChar : unmanaged, IBinaryInteger<TChar>
{
Debug.Assert(typeof(TChar) == typeof(char) || typeof(TChar) == typeof(byte));
return typeof(TChar) == typeof(char)
? (char)(object)value
: (byte)(object)value;
}
// Only called from the IPv6Helper, only parse the canonical format
internal static int ParseHostNumber<TChar>(ReadOnlySpan<TChar> str, int start, int end)
where TChar : unmanaged, IBinaryInteger<TChar>
{
Debug.Assert(typeof(TChar) == typeof(char) || typeof(TChar) == typeof(byte));
Span<byte> numbers = stackalloc byte[NumberOfLabels];
for (int i = 0; i < numbers.Length; ++i)
{
int b = 0;
int ch;
for (; (start < end) && (ch = ToUShort(str[start])) != '.' && ch != ':'; ++start)
{
b = (b * 10) + ch - '0';
}
numbers[i] = (byte)b;
++start;
}
return BinaryPrimitives.ReadInt32BigEndian(numbers);
}
//
// IsValid
//
// Performs IsValid on a substring. Updates the index to where we
// believe the IPv4 address ends
//
// Inputs:
// <argument> name
// string containing possible IPv4 address
//
// <argument> start
// offset in <name> to start checking for IPv4 address
//
// <argument> end
// offset in <name> of the last character we can touch in the check
//
// Outputs:
// <argument> end
// index of last character in <name> we checked
//
// <argument> allowIPv6
// enables parsing IPv4 addresses embedded in IPv6 address literals
//
// <argument> notImplicitFile
// do not consider this URI holding an implicit filename
//
// <argument> unknownScheme
// the check is made on an unknown scheme (suppress IPv4 canonicalization)
//
// Assumes:
// The address string is terminated by either
// end of the string, characters ':' '/' '\' '?'
//
//
// Returns:
// bool
//
// Throws:
// Nothing
//
//Remark: MUST NOT be used unless all input indexes are verified and trusted.
internal static unsafe bool IsValid<TChar>(TChar* name, int start, ref int end, bool allowIPv6, bool notImplicitFile, bool unknownScheme)
where TChar : unmanaged, IBinaryInteger<TChar>
{
// IPv6 can only have canonical IPv4 embedded. Unknown schemes will not attempt parsing of non-canonical IPv4 addresses.
if (allowIPv6 || unknownScheme)
{
return IsValidCanonical(name, start, ref end, allowIPv6, notImplicitFile);
}
else
{
return ParseNonCanonical(name, start, ref end, notImplicitFile) != Invalid;
}
}
//
// IsValidCanonical
//
// Checks if the substring is a valid canonical IPv4 address or an IPv4 address embedded in an IPv6 literal
// This is an attempt to parse ABNF productions from RFC3986, Section 3.2.2:
// IP-literal = "[" ( IPv6address / IPvFuture ) "]"
// IPv4address = dec-octet "." dec-octet "." dec-octet "." dec-octet
// dec-octet = DIGIT ; 0-9
// / %x31-39 DIGIT ; 10-99
// / "1" 2DIGIT ; 100-199
// / "2" %x30-34 DIGIT ; 200-249
// / "25" %x30-35 ; 250-255
//
internal static unsafe bool IsValidCanonical<TChar>(TChar* name, int start, ref int end, bool allowIPv6, bool notImplicitFile)
where TChar : unmanaged, IBinaryInteger<TChar>
{
Debug.Assert(typeof(TChar) == typeof(char) || typeof(TChar) == typeof(byte));
int dots = 0;
long number = 0;
bool haveNumber = false;
bool firstCharIsZero = false;
while (start < end)
{
int ch = ToUShort(name[start]);
if (allowIPv6)
{
// For an IPv4 address nested inside an IPv6 address, the terminator is either the IPv6 address terminator (']'), prefix ('/') or ScopeId ('%')
if (ch == ']' || ch == '/' || ch == '%')
{
break;
}
}
else if (ch == '/' || ch == '\\' || (notImplicitFile && (ch == ':' || ch == '?' || ch == '#')))
{
// For a normal IPv4 address, the terminator is the prefix ('/' or its counterpart, '\'). If notImplicitFile is set, the terminator
// is one of the characters which signify the start of the rest of the URI - the port number (':'), query string ('?') or fragment ('#')
break;
}
// An explicit cast to an unsigned integer forces character values preceding '0' to underflow, eliminating one comparison below.
uint parsedCharacter = (uint)(ch - '0');
if (parsedCharacter < IPv4AddressHelper.Decimal)
{
// A number starting with zero should be interpreted in base 8 / octal
if (!haveNumber && parsedCharacter == 0)
{
if ((start + 1 < end) && name[start + 1] == TChar.CreateTruncating('0'))
{
// 00 is not allowed as a prefix.
return false;
}
firstCharIsZero = true;
}
haveNumber = true;
number = number * IPv4AddressHelper.Decimal + parsedCharacter;
if (number > byte.MaxValue)
{
return false;
}
}
else if (ch == '.')
{
// If the current character is not an integer, it may be the IPv4 component separator ('.')
if (!haveNumber || (number > 0 && firstCharIsZero))
{
// 0 is not allowed to prefix a number.
return false;
}
++dots;
haveNumber = false;
number = 0;
firstCharIsZero = false;
}
else
{
return false;
}
++start;
}
bool res = (dots == 3) && haveNumber;
if (res)
{
end = start;
}
return res;
}
// Parse any canonical or noncanonical IPv4 formats and return a long between 0 and MaxIPv4Value.
// Return Invalid (-1) for failures.
// If the address has less than three dots, only the rightmost section is assumed to contain the combined value for
// the missing sections: 0xFF00FFFF == 0xFF.0x00.0xFF.0xFF == 0xFF.0xFFFF
internal static unsafe long ParseNonCanonical<TChar>(TChar* name, int start, ref int end, bool notImplicitFile)
where TChar : unmanaged, IBinaryInteger<TChar>
{
Debug.Assert(typeof(TChar) == typeof(char) || typeof(TChar) == typeof(byte));
int numberBase = IPv4AddressHelper.Decimal;
int ch = 0;
Span<long> parts = stackalloc long[3]; // One part per octet. Final octet doesn't have a terminator, so is stored in currentValue.
long currentValue = 0;
bool atLeastOneChar = false;
// Parse one dotted section at a time
int dotCount = 0; // Limit 3
int current = start;
for (; current < end; current++)
{
ch = ToUShort(name[current]);
currentValue = 0;
// Figure out what base this section is in, default to base 10.
// A number starting with zero should be interpreted in base 8 / octal
// If the number starts with 0x, it should be interpreted in base 16 / hex
numberBase = IPv4AddressHelper.Decimal;
if (ch == '0')
{
current++;
atLeastOneChar = true;
if (current < end)
{
ch = ToUShort(name[current]);
if (ch == 'x' || ch == 'X')
{
numberBase = IPv4AddressHelper.Hex;
current++;
atLeastOneChar = false;
}
else
{
numberBase = IPv4AddressHelper.Octal;
}
}
}
// Parse this section
for (; current < end; current++)
{
ch = ToUShort(name[current]);
int digitValue = HexConverter.FromChar(ch);
if (digitValue >= numberBase)
{
break; // Invalid/terminator
}
currentValue = (currentValue * numberBase) + digitValue;
if (currentValue > MaxIPv4Value) // Overflow
{
return Invalid;
}
atLeastOneChar = true;
}
if (current < end && ch == '.')
{
if (dotCount >= 3 // Max of 3 dots and 4 segments
|| !atLeastOneChar // No empty segments: 1...1
// Only the last segment can be more than 255 (if there are less than 3 dots)
|| currentValue > 0xFF)
{
return Invalid;
}
parts[dotCount] = currentValue;
dotCount++;
atLeastOneChar = false;
continue;
}
// We don't get here unless we find an invalid character or a terminator
break;
}
// Terminators
if (!atLeastOneChar)
{
return Invalid; // Empty trailing segment: 1.1.1.
}
else if (current >= end)
{
// end of string, allowed
}
else if (ch == '/' || ch == '\\' || (notImplicitFile && (ch == ':' || ch == '?' || ch == '#')))
{
// For a normal IPv4 address, the terminator is the prefix ('/' or its counterpart, '\'). If notImplicitFile is set, the terminator
// is one of the characters which signify the start of the rest of the URI - the port number (':'), query string ('?') or fragment ('#')
end = current;
}
else
{
// not a valid terminating character
return Invalid;
}
// Parsed, reassemble and check for overflows in the last part. Previous parts have already been checked in the loop
switch (dotCount)
{
case 0: // 0xFFFFFFFF
return currentValue;
case 1: // 0xFF.0xFFFFFF
Debug.Assert(parts[0] <= 0xFF);
if (currentValue > 0xffffff)
{
return Invalid;
}
return (parts[0] << 24) | currentValue;
case 2: // 0xFF.0xFF.0xFFFF
Debug.Assert(parts[0] <= 0xFF);
Debug.Assert(parts[1] <= 0xFF);
if (currentValue > 0xffff)
{
return Invalid;
}
return (parts[0] << 24) | (parts[1] << 16) | currentValue;
case 3: // 0xFF.0xFF.0xFF.0xFF
Debug.Assert(parts[0] <= 0xFF);
Debug.Assert(parts[1] <= 0xFF);
Debug.Assert(parts[2] <= 0xFF);
if (currentValue > 0xff)
{
return Invalid;
}
return (parts[0] << 24) | (parts[1] << 16) | (parts[2] << 8) | currentValue;
default:
return Invalid;
}
}
}
}
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