It seems simple you just give an OS program the URI necessary. The program then performs the download and tags it with the relevant metadata.
The example you give would be a bit more complicated, but you would just rewrite curl to attach metadata to file descriptors. Then the OS can have some restrictions about certain programs reading from file descriptors with metadata it deems untrustworthy.
The example you give would be a bit more complicated, but you would just rewrite curl to attach metadata to file descriptors. Then the OS can have some restrictions about certain programs reading from file descriptors with metadata it deems untrustworthy.