arcature 0.1.1

Arcature: an opinionated full-stack Rust web framework. One package, batteries included.
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

//! Response builders: the safe script-body escaper, the initial-page HTML
//! response, the Inertia JSON page response, and the `Vary: X-Inertia` merge.

use std::sync::Arc;

use axum::body::Body;
use axum::http::{HeaderMap, HeaderValue, StatusCode};
use axum::response::{IntoResponse, Response};

use super::config::{InertiaConfig, ScriptBody};
use super::error::InertiaError;
use super::head::Head;
use super::headers::Headers;
use super::page::Page;
use crate::http::security::CspNonce;

/// Escape `json` for safe embedding inside a `<script type="application/json">`
/// element. A provably-unbreakable superset of the official slash-only escape.
pub(crate) fn escape_script_body(json: &str) -> String {
    if json
        .bytes()
        .all(|b| b != b'<' && b != b'>' && b != b'&' && b != b'/')
    {
        return json.to_string();
    }
    let mut out = String::with_capacity(json.len() + json.len() / 16);
    for character in json.chars() {
        match character {
            '<' => out.push_str(r"\u003c"),
            '>' => out.push_str(r"\u003e"),
            '&' => out.push_str(r"\u0026"),
            '/' => out.push_str(r"\/"),
            other => out.push(other),
        }
    }
    out
}

/// Build a [`ScriptBody`] from a serialized page JSON, the page-element id,
/// this request's Content-Security-Policy nonce and this page's [`Head`].
///
/// The nonce goes on the payload script because that script *is* the
/// application: a policy that blocks `<script data-page>` does not degrade an
/// Inertia page, it leaves a blank `<div>`. With no nonce the markup is
/// byte-for-byte what it was before nonces existed.
///
/// The head goes *beside* the markup rather than into it. It is metadata for
/// the `<head>` element, and only the root document knows where that is --
/// which is the whole reason it travels on the `ScriptBody` instead of being
/// rendered here.
pub(crate) fn build_script_body(
    page_json: &str,
    page_id: &str,
    nonce: Option<CspNonce>,
    head: Option<Head>,
) -> ScriptBody {
    let escaped = escape_script_body(page_json);
    let attribute = nonce.as_ref().map(CspNonce::attribute).unwrap_or_default();
    let html = format!(
        "<script{attribute} data-page=\"{page_id}\" type=\"application/json\">{escaped}</script><div id=\"{page_id}\"></div>"
    );
    ScriptBody::from_escaped(Arc::from(html), nonce, head)
}

/// Serialize a [`Page`] to JSON.
pub(crate) fn serialize(page: &Page) -> Result<String, InertiaError> {
    serde_json::to_string(page).map_err(InertiaError::from)
}

/// Build the initial-page HTML response (for non-Inertia requests).
pub(crate) fn html(
    page: &Page,
    config: &InertiaConfig,
    nonce: Option<CspNonce>,
    head: Option<Head>,
    status: StatusCode,
) -> Result<Response, InertiaError> {
    let page_json = serialize(page)?;
    let script_body = build_script_body(&page_json, config.page_id(), nonce, head);
    let document = config.root_document().render(script_body);

    let mut headers = HeaderMap::new();
    headers.insert(
        axum::http::header::CONTENT_TYPE,
        HeaderValue::from_static("text/html; charset=utf-8"),
    );
    ensure_vary_x_inertia(&mut headers);
    Ok((status, headers, Body::from(document)).into_response())
}

/// Build the Inertia JSON response from a serialized page object.
///
/// `status` is the page's own, which is not always `200`: the client decides
/// a response is an Inertia page from the `X-Inertia` header and treats
/// `>= 400` as an event to raise, not a reason to stop rendering. That is how
/// a 404 keeps the application's layout.
pub(crate) fn json_response(page_json: String, status: StatusCode) -> Response {
    let mut headers = HeaderMap::new();
    headers.insert(
        axum::http::header::CONTENT_TYPE,
        HeaderValue::from_static("application/json"),
    );
    headers.insert(Headers::INERTIA, HeaderValue::from_static("true"));
    ensure_vary_x_inertia(&mut headers);
    (status, headers, Body::from(page_json)).into_response()
}

/// Ensure `Vary: X-Inertia` is present on `headers`, merging into any existing
/// `Vary` value without duplicating or discarding application values.
pub(crate) fn ensure_vary_x_inertia(headers: &mut HeaderMap) {
    if headers.get_all(Headers::VARY).iter().next().is_none() {
        headers.insert(Headers::VARY, HeaderValue::from_static("X-Inertia"));
        return;
    }
    let mut tokens: Vec<&str> = Vec::new();
    let mut has_star = false;
    for value in headers.get_all(Headers::VARY).iter() {
        let Ok(value) = value.to_str() else {
            continue;
        };
        for token in value
            .split(',')
            .map(str::trim)
            .filter(|token| !token.is_empty())
        {
            if token == "*" {
                has_star = true;
            }
            if !tokens
                .iter()
                .any(|existing: &&str| existing.eq_ignore_ascii_case(token))
            {
                tokens.push(token);
            }
        }
    }
    if has_star {
        return;
    }
    if !tokens
        .iter()
        .any(|token| token.eq_ignore_ascii_case(Headers::INERTIA.as_str()))
    {
        tokens.push("X-Inertia");
    }
    let combined = tokens.join(", ");
    if let Ok(value) = HeaderValue::from_str(&combined) {
        headers.insert(Headers::VARY, value);
    }
}

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

    #[test]
    fn escape_no_special_chars_unchanged() {
        assert_eq!(escape_script_body(r#"{"a":1}"#), r#"{"a":1}"#);
    }

    #[test]
    fn escape_breakout_neutralized() {
        let escaped = escape_script_body(r#"{"u":"</script>"}"#);
        assert!(!escaped.contains("</script>"));
        let parsed: serde_json::Value = serde_json::from_str(&escaped).unwrap();
        assert_eq!(parsed["u"], "</script>");
    }

    #[test]
    fn escape_comment_breakout_neutralized() {
        let hostile = r#"{"x":"<!--<script>"}"#;
        let escaped = escape_script_body(hostile);
        assert!(!escaped.contains("<!--"));
        let parsed: serde_json::Value = serde_json::from_str(&escaped).unwrap();
        assert_eq!(parsed["x"], "<!--<script>");
    }

    #[test]
    fn the_payload_script_carries_the_nonce_when_there_is_one() {
        // A `script-src 'nonce-X'` policy with an un-nonced payload script
        // does not harden the page, it leaves a blank mount point.
        let nonce = CspNonce::generate().expect("OS RNG");
        let body = build_script_body(r#"{"a":1}"#, "app", Some(nonce.clone()), None).to_string();
        assert!(
            body.starts_with(&format!("<script nonce=\"{nonce}\" data-page=\"app\"")),
            "unexpected markup: {body}"
        );
    }

    #[test]
    fn the_payload_script_is_unchanged_when_there_is_no_nonce() {
        let body = build_script_body(r#"{"a":1}"#, "app", None, None).to_string();
        assert_eq!(
            body,
            "<script data-page=\"app\" type=\"application/json\">{\"a\":1}</script>\
             <div id=\"app\"></div>"
        );
        assert!(!body.contains("nonce"));
    }

    #[test]
    fn a_root_document_can_read_the_nonce_off_the_script_body() {
        // The documented path for a hand-written `RootDocument` that emits
        // scripts of its own, which the framework never sees.
        let nonce = CspNonce::generate().expect("OS RNG");
        let body = build_script_body("{}", "app", Some(nonce.clone()), None);
        assert_eq!(body.nonce().map(CspNonce::as_str), Some(nonce.as_str()));
        assert_eq!(body.nonce_attribute(), format!(" nonce=\"{nonce}\""));

        let none = build_script_body("{}", "app", None, None);
        assert!(none.nonce().is_none());
        assert_eq!(none.nonce_attribute(), "");
    }

    #[test]
    fn a_root_document_can_read_the_head_off_the_script_body() {
        // The head reaches the root document beside the markup, not inside
        // it: the `<head>` element belongs to the document, and only the
        // document knows where it is.
        let head = Head::new()
            .with_title("Quarterly report")
            .with_og_image("/og.png");
        let body = build_script_body("{}", "app", None, Some(head));
        assert_eq!(body.head().and_then(Head::title), Some("Quarterly report"));
        assert!(
            body.head()
                .is_some_and(|h| h.to_html().contains("og:image"))
        );

        // Every application written before heads existed sets none, and its
        // root document sees exactly what it saw before.
        assert!(build_script_body("{}", "app", None, None).head().is_none());
    }

    #[test]
    fn the_head_does_not_leak_into_the_payload_markup() {
        // Escaped or not, metadata in the body is metadata a scraper reading
        // `<head>` never sees and a parser in `<body>` may act on.
        let head = Head::new().with_title("Quarterly report");
        let markup = build_script_body("{}", "app", None, Some(head)).to_string();
        assert!(
            !markup.contains("Quarterly report"),
            "unexpected markup: {markup}"
        );
        assert!(!markup.contains("<title"), "unexpected markup: {markup}");
    }

    #[test]
    fn a_page_response_keeps_the_status_the_page_asked_for() {
        // `isInertiaResponse` keys on the header, not the status, so a 404
        // page object still renders -- inside the application's own layout
        // rather than the browser's error page.
        let response = json_response("{}".to_string(), StatusCode::NOT_FOUND);
        assert_eq!(response.status(), StatusCode::NOT_FOUND);
        assert_eq!(response.headers()[Headers::INERTIA], "true");
        assert_eq!(response.headers()[Headers::VARY], "X-Inertia");
    }

    #[test]
    fn vary_merges_into_existing() {
        let mut h = HeaderMap::new();
        h.insert(Headers::VARY, HeaderValue::from_static("Cookie"));
        ensure_vary_x_inertia(&mut h);
        assert_eq!(h.get(Headers::VARY).unwrap(), "Cookie, X-Inertia");
    }

    #[test]
    fn vary_does_not_duplicate() {
        let mut h = HeaderMap::new();
        h.insert(Headers::VARY, HeaderValue::from_static("X-Inertia"));
        ensure_vary_x_inertia(&mut h);
        assert_eq!(h.get(Headers::VARY).unwrap(), "X-Inertia");
    }
}