I am trying to base64 decode a string with openssl but the string returned isnt valid

Question

This is the code that i am using and the string i am trying to base64 decode is below which is a from the chrome localstate file,DPAPI key.

RFBBUEkBAAAA0Iyd3wEV0RGMegDAT8KX6wEAAADi+GGk7DWzQpfcOpvrA5QBAAAAAAIAAAAAABBmAAAAAQAAIAAAAB71Yux67n+/BdPaKkGQcjERQXhrLPqH+5oIpE0adTRXAAAAAA6AAAAAAgAAIAAAADw0+h5r3BV2XvQ5Dxou4g8lLEs+r7rMr4urasiaUVbLMAAAAIvSN/H/Q04j/4gknX3tPi/jPFo5zqEqsNFOqq3iMvVoAK5ZpYWdc5WBxzR+gXb+7UAAAAC6hU4zxFN3wWaxxwk1YVIB+ePgEFoe9SYynAXhkUIlxSheodOTXxCFij2DPCvxH8eAze6qw6lxHNC4NVHt7Yvu

/* A BASE-64 ENCODER AND DECODER USING OPENSSL */

#include <openssl/pem.h>
#include <string.h> //Only needed for strlen().


unsigned char *base64decode (const void *b64_decode_this, int decode_this_many_bytes){
    BIO *b64_bio, *mem_bio;      //Declares two OpenSSL BIOs: a base64 filter and a memory BIO.
    unsigned char *base64_decoded = calloc( (decode_this_many_bytes*3)/4+1, sizeof(char) ); //+1 = null.
    b64_bio = BIO_new(BIO_f_base64());                      //Initialize our base64 filter BIO.
    mem_bio = BIO_new(BIO_s_mem());                         //Initialize our memory source BIO.
    BIO_write(mem_bio, b64_decode_this, decode_this_many_bytes); //Base64 data saved in source.
    BIO_push(b64_bio, mem_bio);          //Link the BIOs by creating a filter-source BIO chain.
    BIO_set_flags(b64_bio, BIO_FLAGS_BASE64_NO_NL);          //Don't require trailing newlines.
    int decoded_byte_index = 0;   //Index where the next base64_decoded byte should be written.
    while ( 0 < BIO_read(b64_bio, base64_decoded+decoded_byte_index, 1) ){ //Read byte-by-byte.
        decoded_byte_index++; //Increment the index until read of BIO decoded data is complete.
    } //Once we're done reading decoded data, BIO_read returns -1 even though there's no error.
    BIO_free_all(b64_bio);  //Destroys all BIOs in chain, starting with b64 (i.e. the 1st one).
    return base64_decoded;        //Returns base-64 decoded data with trailing null terminator.
}


int main(void){

    char data_to_decode[]="RFBBUEkBAAAA0Iyd3wEV0RGMegDAT8KX6wEAAADi+GGk7DWzQpfcOpvrA5QBAAAAAAIAAAAAABBmAAAAAQAAIAAAAB71Yux67n+/BdPaKkGQcjERQXhrLPqH+5oIpE0adTRXAAAAAA6AAAAAAgAAIAAAADw0+h5r3BV2XvQ5Dxou4g8lLEs+r7rMr4urasiaUVbLMAAAAIvSN/H/Q04j/4gknX3tPi/jPFo5zqEqsNFOqq3iMvVoAK5ZpYWdc5WBxzR+gXb+7UAAAAC6hU4zxFN3wWaxxwk1YVIB+ePgEFoe9SYynAXhkUIlxSheodOTXxCFij2DPCvxH8eAze6qw6lxHNC4NVHt7Yvu";
    int bytes_to_decode = strlen(data_to_decode); //Number of bytes in string to base64 decode.
    unsigned char *base64_decoded = base64decode(data_to_decode, bytes_to_decode);   //Base-64 decoding.


    printf("Base-64 decoded string is: %s\n", base64_decoded);  //Prints base64 decoded string.
    printf("LENGHT:%d",strlen(base64_decoded));
    int i=0;
    while(base64_decoded[i]!='\0')
    {
        printf("\n%i",i);
        i++;
    }

}

This is the string returned when i run it through gdb

"but the string returned isnt valid". You are looking at your "string" with a wrong tool. It's not a string to begin with. It's an array of binary data. — n. m. could be an AI, May 24 '20 at 11:39
Also please don't post images of text. Your console has text in it, not a picture. Post text as text. — n. m. could be an AI, May 24 '20 at 11:42
You view it as you view any other kind of array. You need to know the length of the array. Since your decoder function hides the length, you may want to change it. — n. m. could be an AI, May 25 '20 at 06:55

score 1 · Answer 1 · answered May 25 '20 at 07:39

1

I was able to solve it by viewing the memory contents by gdb x /bx command and not p(print) since the print wont work because it is binary data and a null terminator would terminate the string when printing,thanks to commenter.

answered May 25 '20 at 07:39

yeah_well

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I am trying to base64 decode a string with openssl but the string returned isnt valid

1 Answers1