static void ssl_mac_sha1( unsigned char *secret,
                          unsigned char *buf, size_t len,
                          unsigned char *ctr, int type )
{
    unsigned char header[11];
    unsigned char padding[40];
    sha1_context sha1;

    memcpy( header, ctr, 8 );
    header[ 8] = (unsigned char)  type;
    header[ 9] = (unsigned char)( len >> 8 );
    header[10] = (unsigned char)( len      );

    memset( padding, 0x36, 40 );
    sha1_starts( &sha1 );
    sha1_update( &sha1, secret,  20 );
    sha1_update( &sha1, padding, 40 );
    sha1_update( &sha1, header,  11 );
    sha1_update( &sha1, buf,  len );
    sha1_finish( &sha1, buf + len );

    memset( padding, 0x5C, 40 );
    sha1_starts( &sha1 );
    sha1_update( &sha1, secret,  20 );
    sha1_update( &sha1, padding, 40 );
    sha1_update( &sha1, buf + len, 20 );
    sha1_finish( &sha1, buf + len );
}

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.