How to find the size of decoded base64 data in C

Question

I have an function which decodes the encoded base64 data in binary data but I dont know how to find the length of decoded data. I use the BIO functions in openssl.

unsigned char *unbase64(unsigned char *input, int length)
{
    BIO *b64, *bmem;

    unsigned char *buffer = (unsigned char *)malloc(length);
    memset(buffer, 0, length);

    b64 = BIO_new(BIO_f_base64());
    bmem = BIO_new_mem_buf(input, length);
    bmem = BIO_push(b64, bmem);

    BIO_read(bmem, buffer, length);

    BIO_free_all(bmem);

    return buffer;
}

Answer 1

BIO_read will return the number of bytes read. You should check for return values throughout, anyway.