Initial build

1 files changed, 152 insertions, 0 deletions

diff --git a/src/serve.rs b/src/serve.rs
new file mode 100644
index 0000000..c5d2efd
--- /dev/null
+++ b/src/serve.rs
@@ -0,0 +1,152 @@
+use std::env;
+use std::fs;
+use std::io::{self, Write};
+use std::path::{Component, Path, PathBuf};
+use std::process::ExitCode;
+
+use crate::render;
+
+pub fn run() -> ExitCode {
+    let Ok(document_root) = env::var("DOCUMENT_ROOT") else {
+        return respond_error(500, "DOCUMENT_ROOT is not set");
+    };
+
+    let Some(raw_request) = request_path() else {
+        return respond_error(500, "no request path available");
+    };
+
+    let request = strip_query(&raw_request);
+
+    let Some(target) = safe_join(Path::new(&document_root), request) else {
+        return respond_error(404, "not found");
+    };
+
+    let Ok(metadata) = fs::metadata(&target) else {
+        return respond_error(404, "not found");
+    };
+
+    if !metadata.is_file() {
+        return respond_error(404, "not found");
+    }
+
+    let Ok(bytes) = fs::read(&target) else {
+        return respond_error(500, "read error");
+    };
+
+    let Ok(text) = String::from_utf8(bytes) else {
+        return respond_error(404, "not found");
+    };
+
+    let html = render::page(&target, &text);
+    let body = html.as_bytes();
+
+    let header = format!(
+        "Status: 200 OK\nContent-Type: text/html; charset=utf-8\nContent-Length: {}\n\n",
+        body.len()
+    );
+
+    let stdout = io::stdout();
+    let mut handle = stdout.lock();
+    if handle.write_all(header.as_bytes()).is_err() {
+        return ExitCode::from(1);
+    }
+    if handle.write_all(body).is_err() {
+        return ExitCode::from(1);
+    }
+
+    ExitCode::SUCCESS
+}
+
+fn request_path() -> Option<String> {
+    env::var("DOCUMENT_URI")
+        .or_else(|_| env::var("PATH_INFO"))
+        .ok()
+}
+
+fn strip_query(s: &str) -> &str {
+    let s = s.split('?').next().unwrap_or(s);
+    s.split('#').next().unwrap_or(s)
+}
+
+// Only top-level, non-dotfile names are servable: rejects paths with
+// `..`, with subdirectories, and with names starting with `.`.
+fn safe_join(root: &Path, request: &str) -> Option<PathBuf> {
+    let mut name = None;
+    for component in Path::new(request).components() {
+        match component {
+            Component::Normal(c) => {
+                if name.is_some() {
+                    return None;
+                }
+                if c.as_encoded_bytes().first() == Some(&b'.') {
+                    return None;
+                }
+                name = Some(c);
+            }
+            Component::RootDir | Component::CurDir => {}
+            Component::ParentDir | Component::Prefix(_) => return None,
+        }
+    }
+    name.map(|n| root.join(n))
+}
+
+fn respond_error(code: u16, message: &str) -> ExitCode {
+    let status = match code {
+        400 => "400 Bad Request",
+        403 => "403 Forbidden",
+        404 => "404 Not Found",
+        _ => "500 Internal Server Error",
+    };
+
+    println!("Status: {status}");
+    println!("Content-Type: text/plain; charset=utf-8");
+    println!();
+    println!("{message}");
+
+    ExitCode::SUCCESS
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn safe_join_normal() {
+        let r = safe_join(Path::new("/srv/p"), "/x.txt").unwrap();
+        assert_eq!(r, PathBuf::from("/srv/p/x.txt"));
+    }
+
+    #[test]
+    fn safe_join_rejects_subdirectories() {
+        assert!(safe_join(Path::new("/srv/p"), "/sub/x.txt").is_none());
+        assert!(safe_join(Path::new("/srv/p"), "/a/b/c").is_none());
+    }
+
+    #[test]
+    fn safe_join_rejects_dotfiles() {
+        assert!(safe_join(Path::new("/srv/p"), "/.ssh").is_none());
+        assert!(safe_join(Path::new("/srv/p"), "/.bashrc").is_none());
+        assert!(safe_join(Path::new("/srv/p"), ".env").is_none());
+    }
+
+    #[test]
+    fn safe_join_rejects_parent() {
+        assert!(safe_join(Path::new("/srv/p"), "/../etc/passwd").is_none());
+        assert!(safe_join(Path::new("/srv/p"), "../etc/passwd").is_none());
+        assert!(safe_join(Path::new("/srv/p"), "/sub/../../etc").is_none());
+    }
+
+    #[test]
+    fn safe_join_rejects_empty() {
+        assert!(safe_join(Path::new("/srv/p"), "").is_none());
+        assert!(safe_join(Path::new("/srv/p"), "/").is_none());
+    }
+
+    #[test]
+    fn strip_query_removes_query_and_fragment() {
+        assert_eq!(strip_query("/x.txt?foo=bar"), "/x.txt");
+        assert_eq!(strip_query("/x.txt#frag"), "/x.txt");
+        assert_eq!(strip_query("/x.txt?a=b#frag"), "/x.txt");
+        assert_eq!(strip_query("/x.txt"), "/x.txt");
+    }
+}