transbeam/src/download.rs

use std::{fs::File, os::unix::fs::MetadataExt, time::SystemTime};

use actix_web::{
    body::{self, BoxBody, SizedStream},
    http::{
        header::{
            self, ContentDisposition, DispositionParam, DispositionType, EntityTag, HeaderValue,
            HttpDate, IfMatch, IfModifiedSince, IfNoneMatch, IfUnmodifiedSince,
        },
        StatusCode,
    },
    HttpMessage, HttpRequest, HttpResponse, Responder,
};

use actix_files::HttpRange;

use crate::DownloadableFile;

// This is copied substantially from actix-files, with some tweaks

pub(crate) struct DownloadingFile {
    pub(crate) file: File,
    pub(crate) info: DownloadableFile,
}

impl DownloadingFile {
    fn etag(&self) -> EntityTag {
        let ino = self.file.metadata().map(|md| md.ino()).unwrap_or_default();
        EntityTag::new_strong(format!(
            "{:x}:{:x}:{:x}:{:x}",
            ino,
            self.info.size,
            self.info.modtime.unix_timestamp() as u64,
            self.info.modtime.nanosecond(),
        ))
    }

    /// Creates an `HttpResponse` with file as a streaming body.
    pub fn into_response(self, req: &HttpRequest) -> HttpResponse<BoxBody> {
        let etag = self.etag();
        let last_modified = HttpDate::from(SystemTime::from(self.info.modtime));

        let precondition_failed = precondition_failed(req, &etag, &last_modified);
        let not_modified = not_modified(req, &etag, &last_modified);

        let mut res = HttpResponse::build(StatusCode::OK);

        res.insert_header((header::CONTENT_SECURITY_POLICY, "sandbox"));
        res.insert_header((header::CONTENT_TYPE, mime::APPLICATION_OCTET_STREAM));
        res.insert_header((
            header::CONTENT_DISPOSITION,
            ContentDisposition {
                disposition: DispositionType::Attachment,
                parameters: vec![DispositionParam::Filename(self.info.name)],
            },
        ));
        res.insert_header((header::LAST_MODIFIED, last_modified));
        res.insert_header((header::ETAG, etag));
        res.insert_header((header::ACCEPT_RANGES, "bytes"));

        let mut length = self.info.size;
        let mut offset = 0;

        // check for range header
        if let Some(ranges) = req.headers().get(header::RANGE) {
            if let Ok(ranges_header) = ranges.to_str() {
                if let Ok(ranges) = HttpRange::parse(ranges_header, length) {
                    length = ranges[0].length;
                    offset = ranges[0].start;

                    // don't allow compression middleware to modify partial content
                    res.insert_header((
                        header::CONTENT_ENCODING,
                        HeaderValue::from_static("identity"),
                    ));

                    res.insert_header((
                        header::CONTENT_RANGE,
                        format!(
                            "bytes {}-{}/{}",
                            offset,
                            offset + length - 1,
                            self.info.size
                        ),
                    ));
                } else {
                    res.insert_header((header::CONTENT_RANGE, format!("bytes */{}", length)));
                    return res.status(StatusCode::RANGE_NOT_SATISFIABLE).finish();
                };
            } else {
                return res.status(StatusCode::BAD_REQUEST).finish();
            };
        };

        if precondition_failed {
            return res.status(StatusCode::PRECONDITION_FAILED).finish();
        } else if not_modified {
            return res
                .status(StatusCode::NOT_MODIFIED)
                .body(body::None::new())
                .map_into_boxed_body();
        }

        let reader = crate::file::new_live_reader(length, offset, self.file, self.info.uploader);

        if offset != 0 || length != self.info.size {
            res.status(StatusCode::PARTIAL_CONTENT);
        }

        res.body(SizedStream::new(length, reader))
    }
}

fn precondition_failed(req: &HttpRequest, etag: &EntityTag, last_modified: &HttpDate) -> bool {
    if let Some(IfMatch::Items(ref items)) = req.get_header() {
        if !items.iter().any(|item| item.strong_eq(etag)) {
            return true;
        }
    }
    if let Some(IfUnmodifiedSince(ref since)) = req.get_header() {
        if last_modified > since {
            return true;
        }
    }
    false
}

fn not_modified(req: &HttpRequest, etag: &EntityTag, last_modified: &HttpDate) -> bool {
    match req.get_header::<IfNoneMatch>() {
        Some(IfNoneMatch::Any) => {
            return true;
        }
        Some(IfNoneMatch::Items(ref items)) => {
            return items.iter().any(|item| item.weak_eq(etag));
        }
        None => (),
    }
    if let Some(IfModifiedSince(ref since)) = req.get_header() {
        if last_modified < since {
            return true;
        }
    }
    false
}

impl Responder for DownloadingFile {
    type Body = BoxBody;

    fn respond_to(self, req: &HttpRequest) -> HttpResponse<Self::Body> {
        self.into_response(req)
    }
}