Re: [openssl-users] base64 decode in C

[Prashant Bapat]

Hi Dave and Walter,

Thanks for our reply.

I'm not doing anything different for the ssh pubkey. I'm able to decode it
using the "openssl enc -base64 -d -A" command. But not using the C program.

Attaching my entire code here. After getting the base64 decoded I'm
calculating the MD5 sum and printing it. This works for a regular string
but not for SSH pubkey.

Thanks again.

--Prashant

On 18 March 2015 at 18:04, Walter H. <walte...@mathemainzel.info> wrote:

> Hi,
>
> before calling this function,
> remove any whitespace;
>
> Walter
>
>
>
> _______________________________________________
> openssl-users mailing list
> To unsubscribe: https://mta.openssl.org/mailman/listinfo/openssl-users
>
>

#include <openssl/md5.h>
#include <openssl/sha.h>
#include <openssl/hmac.h>
#include <openssl/evp.h>
#include <openssl/bio.h>
#include <openssl/buffer.h>
#include <string.h>
#include <stdio.h>

char *b64_decode(unsigned char *input, int length);
char* md5_digest(char *string);

int main()
{
    char *str = "AAAAB3NzaC1yc2EAAAADAQABAAABAQC/KdcFv09+f+tJK9IZ8I+L0zG7dUINClI5v8FlHJsBPSM3DDO2DpwIg/KqZKCRH9y6lEO+QAJt2DTEq/LBZcBUCdeiX1TXPFRorX+VdZigj7av/S/UHkq2EH6hfkJB3oLA5ZOZioMOAuDv1ng/DE4pRBr+KZ2oVhGjf3wa0hWi21vTZqb3s7vh+bPf6C2eUmAQJKHvFhtBK8Xx7FxN0b7igsGbk7ObwcItfMxdzkMvuiuU/UnthFVpa8wZIObFDi3MxJuf3/R+h6R1lFMvEIrU6CWRupS7Pqkm4X3qWQfhAWbdgdbD5KAk5JLA2eWIPQQA5Uay5CeH+GXz8gCa4zaz";

    printf("Base64 decoded string is : %s\n", b64_decode(str, strlen(str))); // This should print binary for a ssh key.
    printf("MD5 Sum of the decoded string is : %s\n", md5_digest(b64_decode(str, strlen(str))));
    
    return 0;
}

char *b64_decode(unsigned char *input, int length)
{
    BIO *b64, *bmem;
    char *buffer = (char *)malloc(length);
    memset(buffer, 0, length);
    b64 = BIO_new(BIO_f_base64());
    bmem = BIO_new_mem_buf((void*)input, length);
    bmem = BIO_push(b64, bmem);
    BIO_set_flags(bmem, BIO_FLAGS_BASE64_NO_NL);
    BIO_read(bmem, buffer, length);
    BIO_free_all(bmem);
    return buffer;
}

char* md5_digest(char *string)
{
  int i;
  unsigned char result[MD5_DIGEST_LENGTH];

  // Length of MD5 signature is 32 !
  char * md5_sig = (char *) malloc(33);
  
  MD5(string, strlen(string), result);

  // output
  for(i = 0; i < MD5_DIGEST_LENGTH; i++){
        sprintf( &md5_sig[i*2], "%02x", result[i]);
    }
  return md5_sig;
}

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