actix-mark 0.9.0

Actix-web service for serving Markdown files as HTML
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306

use std::{
    path::{Path, PathBuf},
    sync::Arc,
};

use actix_web::{
    dev::{AppService, HttpServiceFactory, ResourceDef, ServiceRequest, ServiceResponse},
    http::header,
    Error, HttpResponse,
};
use actix_files::NamedFile;
use tokio::fs;

use crate::{markdown, template};

// ---------------------------------------------------------------------------
// Internal path resolution result
// ---------------------------------------------------------------------------

enum ResolvedPath {
    Markdown(PathBuf),
    Static(PathBuf),
}

// ---------------------------------------------------------------------------
// Builder
// ---------------------------------------------------------------------------

/// Actix-web service that serves a directory, rendering `.md` files as HTML.
///
/// # Example
/// ```no_run
/// use actix_mark::MarkdownFiles;
///
/// let svc = MarkdownFiles::new("/docs", "./content")
///     .template("<html><body><markdown></body></html>");
/// ```
pub struct MarkdownFiles {
    mount_path: String,
    dir: PathBuf,
    template: String,
}

impl MarkdownFiles {
    /// Create a new `MarkdownFiles` service.
    ///
    /// - `mount_path`: the URL prefix (e.g. `"/docs"`)
    /// - `dir`: the filesystem directory to serve from
    pub fn new(mount_path: &str, dir: impl Into<PathBuf>) -> Self {
        Self {
            mount_path: mount_path.to_string(),
            dir: dir.into(),
            template: String::new(),
        }
    }

    /// Set the HTML template as a string.
    ///
    /// The template must contain a `<markdown>` (or `<markdown/>`) tag which
    /// will be replaced with the rendered HTML content.
    pub fn template(mut self, tmpl: impl Into<String>) -> Self {
        self.template = tmpl.into();
        self
    }

    /// Load the HTML template from a file.
    ///
    /// The file is read eagerly so errors surface at startup, not at request time.
    pub fn template_file(mut self, path: impl AsRef<Path>) -> std::io::Result<Self> {
        self.template = std::fs::read_to_string(path)?;
        Ok(self)
    }
}

// ---------------------------------------------------------------------------
// HttpServiceFactory
// ---------------------------------------------------------------------------

impl HttpServiceFactory for MarkdownFiles {
    fn register(self, config: &mut AppService) {
        // The pattern ends with `{tail:.*}` to capture everything under the
        // mount path, including nested directories.
        let pattern = if self.mount_path.ends_with('/') {
            format!("{}{}", self.mount_path, "{tail:.*}")
        } else {
            format!("{}/{}", self.mount_path, "{tail:.*}")
        };

        let rdef = ResourceDef::new(pattern);
        let svc = MarkdownFilesService(Arc::new(MarkdownFilesInner {
            dir: self.dir,
            template: self.template,
        }));

        config.register_service(rdef, None, svc, None);
    }
}

// ---------------------------------------------------------------------------
// Inner service data and newtype service handle
// ---------------------------------------------------------------------------

struct MarkdownFilesInner {
    dir: PathBuf,
    template: String,
}

/// Newtype so we can implement foreign traits without hitting the orphan rule.
pub struct MarkdownFilesService(Arc<MarkdownFilesInner>);

// ---------------------------------------------------------------------------
// actix-web Service + ServiceFactory boilerplate
// ---------------------------------------------------------------------------

impl actix_web::dev::ServiceFactory<ServiceRequest> for MarkdownFilesService {
    type Response = ServiceResponse;
    type Error = Error;
    type Config = ();
    type Service = Self;
    type InitError = ();
    type Future = std::future::Ready<Result<Self::Service, Self::InitError>>;

    fn new_service(&self, _: ()) -> Self::Future {
        std::future::ready(Ok(MarkdownFilesService(self.0.clone())))
    }
}

impl actix_web::dev::Service<ServiceRequest> for MarkdownFilesService {
    type Response = ServiceResponse;
    type Error = Error;
    type Future = std::pin::Pin<Box<dyn std::future::Future<Output = Result<Self::Response, Self::Error>>>>;

    fn poll_ready(
        &self,
        _: &mut std::task::Context<'_>,
    ) -> std::task::Poll<Result<(), Self::Error>> {
        std::task::Poll::Ready(Ok(()))
    }

    fn call(&self, req: ServiceRequest) -> Self::Future {
        let inner = self.0.clone();
        Box::pin(async move { inner.handle(req).await })
    }
}

// ---------------------------------------------------------------------------
// Request handling
// ---------------------------------------------------------------------------

impl MarkdownFilesInner {
    async fn handle(&self, req: ServiceRequest) -> Result<ServiceResponse, Error> {
        let tail = req
            .match_info()
            .get("tail")
            .unwrap_or("")
            .to_string();

        match self.resolve_path(&tail) {
            Some(ResolvedPath::Markdown(path)) => self.serve_markdown(req, &path).await,
            Some(ResolvedPath::Static(path)) => self.serve_static(req, &path),
            None => {
                let (req, _) = req.into_parts();
                Ok(ServiceResponse::new(req, HttpResponse::NotFound().finish()))
            }
        }
    }

    fn resolve_path(&self, tail: &str) -> Option<ResolvedPath> {
        let rel = tail.trim_start_matches('/');
        let candidate = self.dir.join(rel);

        // Safety check first — bail if the candidate escapes the base dir.
        if !is_safe(&self.dir, &candidate) {
            return None;
        }

        // Directory → try index.md
        if candidate.is_dir() {
            let index = candidate.join("index.md");
            if index.is_file() {
                return Some(ResolvedPath::Markdown(index));
            }
            return None;
        }

        // Exact .md file
        if candidate.extension().is_some_and(|e| e == "md") && candidate.is_file() {
            return Some(ResolvedPath::Markdown(candidate));
        }

        // Extension-less path → try appending .md
        if candidate.extension().is_none() {
            let with_md = candidate.with_extension("md");
            if with_md.is_file() {
                return Some(ResolvedPath::Markdown(with_md));
            }
        }

        // Anything else that exists → static file
        if candidate.is_file() {
            return Some(ResolvedPath::Static(candidate));
        }

        None
    }

    async fn serve_markdown(
        &self,
        req: ServiceRequest,
        path: &Path,
    ) -> Result<ServiceResponse, Error> {
        let source = fs::read_to_string(path).await.map_err(|e| {
            actix_web::error::ErrorInternalServerError(e)
        })?;

        let html_body = markdown::to_html(&source);
        let page = template::render(&self.template, &html_body);

        let (req, _) = req.into_parts();
        let resp = HttpResponse::Ok()
            .insert_header((header::CONTENT_TYPE, "text/html; charset=utf-8"))
            .body(page);

        Ok(ServiceResponse::new(req, resp))
    }

    fn serve_static(
        &self,
        req: ServiceRequest,
        path: &Path,
    ) -> Result<ServiceResponse, Error> {
        let file = NamedFile::open(path).map_err(actix_web::error::ErrorInternalServerError)?;
        let (http_req, _) = req.into_parts();
        let resp = file.into_response(&http_req);
        Ok(ServiceResponse::new(http_req, resp))
    }
}

// ---------------------------------------------------------------------------
// Path traversal guard
// ---------------------------------------------------------------------------

fn is_safe(base: &Path, target: &Path) -> bool {
    // Canonicalize the base; for the target we build a canonical-like path
    // without requiring it to exist yet (to handle .md extension probing).
    let Ok(canon_base) = base.canonicalize() else {
        return false;
    };

    // Normalize the target by canonicalizing its existing prefix.
    // We walk up until we find a component that exists, then re-attach the rest.
    let mut existing = target.to_path_buf();
    let mut suffix = vec![];
    loop {
        if existing.exists() {
            break;
        }
        match existing.file_name() {
            Some(name) => {
                suffix.push(name.to_os_string());
                existing.pop();
            }
            None => return false,
        }
    }
    let Ok(mut canon) = existing.canonicalize() else {
        return false;
    };
    for component in suffix.into_iter().rev() {
        canon.push(component);
    }

    canon.starts_with(&canon_base)
}

// ---------------------------------------------------------------------------
// URL helpers exposed for the example/tests
// ---------------------------------------------------------------------------

/// Returns the URL path a browser should use to reach a given `.md` file,
/// stripping the `.md` extension.
pub fn md_url(base_url: &str, rel_path: &str) -> String {
    let stripped = rel_path
        .strip_suffix(".md")
        .unwrap_or(rel_path);
    format!("{}/{}", base_url.trim_end_matches('/'), stripped.trim_start_matches('/'))
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn safe_path_within_base() {
        let base = PathBuf::from(".");
        let target = PathBuf::from("./src/lib.rs");
        assert!(is_safe(&base, &target));
    }

    #[test]
    fn traversal_is_rejected() {
        let base = PathBuf::from("./src");
        let target = PathBuf::from("./src/../../Cargo.toml");
        assert!(!is_safe(&base, &target));
    }
}