[Rule Idea] - Validate CC Number using Luhn's (.NET variation)

[re-fox]

Prerequisites

• [x] Put an X between the brackets on this line if you have done all of the following:
  • Checked that your rule idea isn't already filed: search

Summary

Currently, the 2 rules for Luhn's algorithm are built using some x86 specific mnemonics. It would be useful to have a .NET version looking for the same algorithm.

Examples

An implementation can be found in the sample 90140a12763b56ffbbefa1a77fb2fbff7988828e61c7b9730d3a8d84b3c5db9f

private bool IsValidCreditCardNumber(string number)
{
	number = number.Replace("-", string.Empty);
	number = number.Replace(" ", string.Empty);
	int[] array = new int[10] {0,1,2,3,4,-4,-3,-2,-1,0};
	int num = 0;
	char[] array2 = number.ToCharArray();
	for (int num2 = array2.Length - 1; num2 > -1; num2--)
	{
		int num3 = array2[num2] - 48;
		num += num3;
		if ((num2 - array2.Length) % 2 == 0)
		{
			num += array[num3];
		}
	}
	return num % 10 == 0;
}

Features

Using dncil:

Method: IsValidCreditCardNumber
16E4    03                  ldarg.1        
16E5    72 54 04 00 70      ldstr          "-"
16EA    7e 33 00 00 0a      ldsfld         System.String::Empty
16EF    6f a3 00 00 0a      callvirt       System.String::Replace
16F4    10 01               starg.s        argument(0x0001)
16F6    03                  ldarg.1        
16F7    72 58 04 00 70      ldstr          " "
16FC    7e 33 00 00 0a      ldsfld         System.String::Empty
1701    6f a3 00 00 0a      callvirt       System.String::Replace
1706    10 01               starg.s        argument(0x0001)
1708    1f 0a               ldc.i4.s       0xa
170A    8d 6c 00 00 01      newarr         System.Int32
170F    25                  dup            
1710    d0 bb 00 00 04      ldtoken        F364C739E7AD18CDC8D2C2142680F4FBFC38EFD9
1715    28 a4 00 00 0a      call           System.Runtime.CompilerServices.RuntimeHelpers::InitializeArray
171A    0a                  stloc.0        
171B    16                  ldc.i4.0       
171C    0b                  stloc.1        
171D    03                  ldarg.1        
171E    6f a5 00 00 0a      callvirt       System.String::ToCharArray
1723    0c                  stloc.2        
1724    08                  ldloc.2        
1725    8e                  ldlen          
1726    69                  conv.i4        
1727    17                  ldc.i4.1       
1728    59                  sub            
1729    0d                  stloc.3        
172A    2b 21               br.s           0x174d
172C    08                  ldloc.2        
172D    09                  ldloc.3        
172E    93                  ldelem.u2      
172F    1f 30               ldc.i4.s       0x30
1731    59                  sub            
1732    13 04               stloc.s        local(0x0004)
1734    07                  ldloc.1        
1735    11 04               ldloc.s        local(0x0004)
1737    58                  add            
1738    0b                  stloc.1        
1739    09                  ldloc.3        
173A    08                  ldloc.2        
173B    8e                  ldlen          
173C    69                  conv.i4        
173D    59                  sub            
173E    18                  ldc.i4.2       
173F    5d                  rem            
1740    2d 07               brtrue.s       0x1749
1742    07                  ldloc.1        
1743    06                  ldloc.0        
1744    11 04               ldloc.s        local(0x0004)
1746    94                  ldelem.i4      
1747    58                  add            
1748    0b                  stloc.1        
1749    09                  ldloc.3        
174A    17                  ldc.i4.1       
174B    59                  sub            
174C    0d                  stloc.3        
174D    09                  ldloc.3        
174E    15                  ldc.i4.m1      
174F    30 db               bgt.s          0x182c
1751    07                  ldloc.1        
1752    1f 0a               ldc.i4.s       0xa
1754    5d                  rem            
1755    16                  ldc.i4.0       
1756    fe 01               ceq            
1758    2a                  ret            

Additional context

Rule details

Some features that might be leveraged to build a rule:

If the array is exposed as a feature, it should be stored in the form of

    .data cil I_000028A0 = bytearray (
        00 00 00 00 01 00 00 00 02 00 00 00 03 00 00 00
        04 00 00 00 fc ff ff ff fd ff ff ff fe ff ff ff
        ff ff ff ff 00 00 00 00
    )

• Init of newarray that stores the lookup values

170A    8d 6c 00 00 01      newarr         System.Int32

• Sub 0x30 to convert string integer to int

172F    1f 30               ldc.i4.s       0x30
1731    59                  sub     

• Mod 10 before return

1752    1f 0a               ldc.i4.s       0xa
1754    5d                  rem 

(optional)

1756    fe 01               ceq            

Namespace

data-manipulation/checksum/luhn

References

Other rule meta information

mbc Data::Checksum::Luhn [C0032.002]