Decryption and encryption of packet using openssl command line

[Riaz Farnaz]

Hi,

 I have a query about how to use the openssl command line to decrypt and encrypt my packet. Below is an ipsec encrypted packet which i decrypt and print on the console. When I try to do the same with openssl command line it gives a different value

Before decryption (below is a complete packet which I have split for understandability)
START
00000000: 4500 0060 9f80 4000 8032 d65e c0a8 01a2  [EMAIL PROTECTED]
00000010: c0a8 019a  ---> IP Packet

                    9e40 cf04 0000 0002 ---> SPI and Sequence number

                                        9971 4c73  [EMAIL PROTECTED]
00000020: 7842 49c1 ---> IV

                    7b13 3576 8c17 21c8 65a9 8d00  xBI.{.5v..!.e...
00000030: 1e99 1b74 3e86 6476 07e7 f8e8 04f0 0e5d  ...t>.dv.......]
00000040: 8d63 41d9 cdb0 1304 c800 0b6e bfbb c069  .cA........n...i
00000050: e594 b4d5  ---> Encrypted packet
                    b330 d80f 84cc 0106 57b8 0eaf  .....0......W... -->
                    Authentication data
END

After Decryption
START
<IP_PACKET> not shown

00000000: 9e40 cf04 0000 0002 ---> SPI and sequence number
                                               9971 4c73 7842 49c1  [EMAIL PROTECTED] ---> IV

START OF DECRYPTED PACKET
00000010: 0def 01bb a8cc c11d d59f 3997 5019 faf0  ..........9.P...
00000020: 7452 0000 1503 0100 1228 ce83 baef 8a8b  tR.......(......
00000030: b4e9 a6b8 03b5 8392 da04 3a

                                                           01 0203 0306  ..........:..... --->
                                     padding, pad length and next header field
END OF DECRYPTED PACKET

00000040: b330 d80f 84cc 0106 57b8 0eaf            .0......W... --->
Authentication data
END

00000000: cbcc d7dc c448 fd53 4dce d67f d2c3 6fe0  .....H.SM.....o.
00000010: 5838 0444 --> Cipher key


The command that I am using for decryption of the packet is

--> openssl enc -des3 -in input_pkt -out out_pkt -nopad -d -K "7de79edfe7046acd223f6a72b6bb354c4a6888f672d61cbb" -iv "43990d51bba59ece

The input packet I am passing as an array in a c file and printing the ascii into a file name input_packet. Below is the code for it

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>

int main()
{
    unsigned char in_packet[]={ 0x7b,0x13,  0x35,0x76,  0x8c,0x17,  0x21,0xc8,  0x65,0xa9,  0x8d,0x00,  0x1e,0x99,  0x1b,0x74,  0x3e,0x86,  0x64,0x76,  0x07,0xe7,  0xf8,0xe8,  0x04,0xf0,  0x0e,0x5d,  0x8d,0x63,  0x41,0xd9,  0xcd,0xd0,  0x13,0x04,  0xc8,0x00,  0x0b,0x6e,  0xbf,0xbb,  0xc0,0x69,  0xe5,0x94,  0xb4, 0xd5};

    unsigned int i=0;
    FILE *fd_d;

    fd_d = fopen("input_pkt","r+");
    printf("sizeof in_packet is : %d\n",sizeof(in_packet));

    if(fd_d == NULL)
    {
        printf("fd not created\n");
        return 1;
    }

    while(i < (sizeof(in_packet)))
    {
        fprintf(fd_d,"%c",in_packet[i]);
        printf("%x",in_packet[i]);
        i++;
    }
    printf("\nvalue of i is %d\n",i);
    fclose(fd_d);
    return 0;
}

Can any one help me out. the packet after decryption should look like the above. I think many of you might have used this functionality and it shouldn't a difficult thing for you folks to answer.

Thanks a lot in advance.