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

use crate::{Attribute, IntoAttribute};
use leptos_reactive::{use_context, Scope};
use std::{fmt::Display, ops::Deref};

/// A nonce a cryptographic nonce ("number used once") which can be
/// used by Content Security Policy to determine whether or not a given
/// resource will be allowed to load.
///
/// When the `nonce` feature is enabled on one of the server integrations,
/// a nonce is generated during server rendering and added to all inline
/// scripts used for HTML streaming and resource loading.
///
/// The nonce being used during the current server response can be
/// accessed using [`use_nonce`](use_nonce).
///
/// ```rust,ignore
/// #[component]
/// pub fn App(cx: Scope) -> impl IntoView {
///     provide_meta_context(cx);
///
///     view! { cx,
///         // use `leptos_meta` to insert a <meta> tag with the CSP
///         <Meta
///             http_equiv="Content-Security-Policy"
///             content=move || {
///                 // this will insert the CSP with nonce on the server, be empty on client
///                 use_nonce(cx)
///                     .map(|nonce| {
///                         format!(
///                             "default-src 'self'; script-src 'strict-dynamic' 'nonce-{nonce}' \
///                             'wasm-unsafe-eval'; style-src 'nonce-{nonce}';"
///                         )
///                     })
///                     .unwrap_or_default()
///             }
///         />
///         // manually insert nonce during SSR on inline script
///         <script nonce=use_nonce(cx)>"console.log('Hello, world!');"</script>
///         // leptos_meta <Style/> and <Script/> automatically insert the nonce
///         <Style>"body { color: blue; }"</Style>
///         <p>"Test"</p>
///     }
/// }
/// ```
#[derive(Clone, Debug, PartialEq, Eq, Hash)]
pub struct Nonce(pub(crate) String);

impl Deref for Nonce {
    type Target = str;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl Display for Nonce {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.0)
    }
}

impl IntoAttribute for Nonce {
    fn into_attribute(self, _cx: Scope) -> Attribute {
        Attribute::String(self.0.into())
    }

    fn into_attribute_boxed(self: Box<Self>, _cx: Scope) -> Attribute {
        Attribute::String(self.0.into())
    }
}

impl IntoAttribute for Option<Nonce> {
    fn into_attribute(self, cx: Scope) -> Attribute {
        Attribute::Option(cx, self.map(|n| n.0.into()))
    }

    fn into_attribute_boxed(self: Box<Self>, cx: Scope) -> Attribute {
        Attribute::Option(cx, self.map(|n| n.0.into()))
    }
}

/// Accesses the nonce that has been generated during the current
/// server response. This can be added to inline `<script>` and
/// `<style>` tags for compatibility with a Content Security Policy.
///
/// ```rust,ignore
/// #[component]
/// pub fn App(cx: Scope) -> impl IntoView {
///     provide_meta_context(cx);
///
///     view! { cx,
///         // use `leptos_meta` to insert a <meta> tag with the CSP
///         <Meta
///             http_equiv="Content-Security-Policy"
///             content=move || {
///                 // this will insert the CSP with nonce on the server, be empty on client
///                 use_nonce(cx)
///                     .map(|nonce| {
///                         format!(
///                             "default-src 'self'; script-src 'strict-dynamic' 'nonce-{nonce}' \
///                             'wasm-unsafe-eval'; style-src 'nonce-{nonce}';"
///                         )
///                     })
///                     .unwrap_or_default()
///             }
///         />
///         // manually insert nonce during SSR on inline script
///         <script nonce=use_nonce(cx)>"console.log('Hello, world!');"</script>
///         // leptos_meta <Style/> and <Script/> automatically insert the nonce
///         <Style>"body { color: blue; }"</Style>
///         <p>"Test"</p>
///     }
/// }
/// ```
pub fn use_nonce(cx: Scope) -> Option<Nonce> {
    use_context::<Nonce>(cx)
}

#[cfg(all(feature = "ssr", feature = "nonce"))]
pub use generate::*;

#[cfg(all(feature = "ssr", feature = "nonce"))]
mod generate {
    use super::Nonce;
    use base64::{
        alphabet,
        engine::{self, general_purpose},
        Engine,
    };
    use leptos_reactive::{provide_context, Scope};
    use rand::{thread_rng, RngCore};

    const NONCE_ENGINE: engine::GeneralPurpose = engine::GeneralPurpose::new(
        &alphabet::URL_SAFE,
        general_purpose::NO_PAD,
    );

    impl Nonce {
        /// Generates a new nonce from 16 bytes (128 bits) of random data.
        pub fn new() -> Self {
            let mut thread_rng = thread_rng();
            let mut bytes = [0; 16];
            thread_rng.fill_bytes(&mut bytes);
            Nonce(NONCE_ENGINE.encode(bytes))
        }
    }

    impl Default for Nonce {
        fn default() -> Self {
            Self::new()
        }
    }

    /// Generates a nonce and provides it during server rendering.
    pub fn provide_nonce(cx: Scope) {
        provide_context(cx, Nonce::new())
    }
}