Error CryptDecode

franzk 2014.07.29 08:45

Hi,

just trying the new CryptEncode and CryptDecode functions. Everything is working as expected with CryptEncode. However when using the provided example with a slight modification (converting the char array into a string and back to a char array). I am getting the 4029 error.

//+------------------------------------------------------------------+
//| ArrayToHex                                                       |
//+------------------------------------------------------------------+
string ArrayToHex(uchar &arr[],int count=-1)
  {
   string res="";
//--- check
   if(count<0 || count>ArraySize(arr))
      count=ArraySize(arr);
//--- transform to HEX string
   for(int i=0; i<count; i++)
      res+=StringFormat("%.2X",arr[i]);
//---
   return(res);
  }
//+------------------------------------------------------------------+
//| Script program start function                                    |
//+------------------------------------------------------------------+
void OnStart()
  {
   string text="The quick brown fox jumps over the lazy dog";
   string keystr="ABCDEFG";
   uchar src[],dst[],key[];
//--- prepare key
   StringToCharArray(keystr,key);
//--- copy text to source array src[]
   StringToCharArray(text,src);
//--- print initial data
   PrintFormat("Initial data: size=%d, string='%s'",ArraySize(src),CharArrayToString(src));
//--- encrypt src[] with DES 56-bit key in key[]
   int res=CryptEncode(CRYPT_DES,src,key,dst);
//--- check error
   if(res>0)
     {
      //--- print encrypted data
      PrintFormat("Encoded data: size=%d %s",res,ArrayToHex(dst));
      //--- decode dst[] to src[]

//modifications
string dstStr = CharArrayToString(dst);
uchar dst2[],src2[];
StringToCharArray(dstStr,dst2);
res=CryptDecode(CRYPT_DES,dst2,key,src2);
// end modifications

      //--- check error     
      if(res>0)
        {
         //--- print decoded data
         PrintFormat("Decoded data: size=%d, string='%s'",ArraySize(src),CharArrayToString(src));
        }
      else
         Print("Error in CryptDecode. Error code=",GetLastError());
     }
   else
      Print("Error in CryptEncode. Error code=",GetLastError());
  }

qjol 2014.07.29 09:57 #1

what's the purpose of doing this

franzk 2014.07.29 10:57 #2

this obviously has no purpose. It's just for showing the error :)

In the real application I am trying to convert a base64encoded string which is resulting in the same error. In order to decode this string I have to map it to a chararray because CryptDecode only accepts an uchar array as parameter.

Errors, bugs, questions why is CryptDecode not iCustom and parameters

qjol 2014.07.29 11:29 #3

then use

res=CryptDecode(CRYPT_BASE64,dst,key,src);

why all the trouble to convert from CharArrayToString and convert back StringToCharArray

it's the like you were doing:

int a = 10 * 10;
int b = a / 10;

franzk 2014.07.29 11:41 #4

ok ... I didn't make myself clear probably. So another example which hopefully shows my problem better.

string textBase64="VGhlIHF1aWNrIGJyb3duIGZveCBqdW1wcyBvdmVyIHRoZSBsYXp5IGRvZw=="; //The quick brown fox jumps over the lazy dog
string keystr="ABCDEFG";
   
uchar src[],dst[],key[];
//--- prepare key
StringToCharArray(keystr,key);
//--- copy text to source array src[]
StringToCharArray(textBase64,src);

//--- decrypt src[] with base64 key in key[]
int res=CryptDecode(CRYPT_BASE64,src,key,dst);
//--- check error
   if(res>0)
   {
      //--- print decrypted data
      Print(StringConcatenate("Decoded data: ",CharArrayToString(dst)));
   }
   else
      Print("Error in CryptDecode. Error code=",GetLastError());

qjol 2014.07.29 11:51 #5

you have to remove the last char from the string after converting from CharArrayToString

//modifications
string dstStr = CharArrayToString(dst);
string dstStrTrimmed = StringSubstr(dstStr, 0, StringLen(dstStr) -1);
uchar dst2[],src2[];
StringToCharArray(dstStrTrimmed,dst2);
res=CryptDecode(CRYPT_DES,dst2,key,src2);
// end modifications

franzk 2014.07.29 13:17 #6

Thank you so much! This is working perfectly for CRYPT_DES or CRYPT_BASE64.

How about CRYPT_AES128 or CRYPT_AES256. There I am still getting the 4029 error. Do you have a hint on that one also? :)

Error 4029 Invalid array Slope Direction Line problem Arrow Code Function

franzk 2014.07.30 05:23 #7

Sorry gjol ... your solution is also working for CRYPT_AES128+. I just forgot to adapt the key. Need to use a 32 long keystring.

Thanks again foir your help!

franzk 2014.07.30 09:26 #8

ok ... me again. Was a little quick with reporting success ;)

The result of the workaround provided by gjol is totally different depending on the used coding method.

- It is working with CRYPT_BASE64
- with CRYPT_AES128 I am still getting the 4029 error
- with CRYPT_DES or CRYPT_AES256 the 4029 error is gone ... however the result is not as expected. See below (using CRYPT_AES256):

   string text="The quick brown fox jumps over the lazy dog";
   string keystr="9ADE769DE7B2D51F6EBBC3CC7F744ZY5";

   uchar src[],dst[],key[];
//--- prepare key
   StringToCharArray(keystr,key);
//--- copy text to source array src[]
   StringToCharArray(text,src);
//--- print initial data
   PrintFormat("Initial data: size=%d, string='%s'",ArraySize(src),CharArrayToString(src));
//--- encrypt src[] with DES 56-bit key in key[]
   int res=CryptEncode(CRYPT_AES256,src,key,dst);
//--- check error
   if(res>0)
     {
      //--- print encrypted data
      PrintFormat("Encoded data: size=%d %s",res,ArrayToHex(dst));
      //--- decode dst[] to src[]

//modifications
string dstStr = CharArrayToString(dst);
uchar dst2[],src2[];
StringToCharArray(StringSubstr(dstStr,0,StringLen(dstStr)-1),dst2);
//StringToCharArray(dstStr,dst2);
res=CryptDecode(CRYPT_AES256,dst2,key,src2);
// end modifications

      //--- check error     
      if(res>0)
        {
         //--- print decoded data
         PrintFormat("Decoded data: size=%d, string='%s'",ArraySize(src2),CharArrayToString(src2));
        }
      else
         Print("Error in CryptDecode. Error code=",GetLastError());
     }
   else
      Print("Error in CryptEncode. Error code=",GetLastError());

results in:

Decoded data: size=48, string='The quick brown fox jumps over tñ×vc&TÌ³oQb°/'
Encoded data: size=48 A7417057F2FD37D3E7DC5CC7A4998C438995CE5A502D7C5E0AD7E65D18B57003C112834D8FB717B3EC8B7EE4B7B1F577
Initial data: size=44, string='The quick brown fox jumps over the lazy dog'

This whole thing is totally confusing for me.

Ontester() ...Error, it is Support Resistance EA - Error 4756 but the

Rashid Umarov 2014.07.30 11:24 #9

franzk:

ok ... me again. Was a little quick with reporting success ;)

You should print out values of dst2[47] и dst[47] in order to understand nature of difference and then fix your errors in this awful code. But generally speaking this code must be rewritten from scratch. It is so bad....

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franzk 2014.07.30 12:43 #10

Thank you for your response. The code actually comes from the example provided in the documentation for CrpytEncode() here: https://docs.mql4.com/common/cryptencode

It should just point out where my problem is.

Seems I have to add this workaround in order to make it work

uchar dst3[];
ArrayCopy(dst3,dst2,0,0,(ArraySize(dst2)-1));

using dst3 for decrypting afterwards because after converting the string to an array it is adding a "0" character to the array messing with the arraysize CryptDecode is expecting. Looks like a bug in StringToCharArray() maybe? In my real code I am now calling the function below instead of StringToCharArray()

int StringToCharArrayWrap(string _str, uchar& _arr[])
{
uchar _tmpChar[];
int z=0;

StringToCharArray(_str,_tmpChar);
   if(ArraySize(_tmpChar)>StringLen(_str))
      z=1;
ArrayCopy(_arr,_tmpChar,0,0,(ArraySize(_tmpChar)-z));
return(ArraySize(_arr));   
}

All solved now (hopefully) ;)

Thanks again everyone!

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