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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
use base64;
use net_traits::response::{Response, ResponseBody, ResponseType};
use openssl::hash::{MessageDigest, hash2};
use std::iter::Filter;
use std::str::Split;
use std::sync::MutexGuard;
const SUPPORTED_ALGORITHM: &'static [&'static str] = &[
"sha256",
"sha384",
"sha512",
];
pub type StaticCharVec = &'static [char];
/// A "space character" according to:
///
/// <https://html.spec.whatwg.org/multipage/#space-character>
pub static HTML_SPACE_CHARACTERS: StaticCharVec = &[
'\u{0020}',
'\u{0009}',
'\u{000a}',
'\u{000c}',
'\u{000d}',
];
#[derive(Clone)]
pub struct SriEntry {
pub alg: String,
pub val: String,
// TODO : Current version of spec does not define any option.
// Can be refactored into appropriate datastructure when future
// spec has more details.
pub opt: Option<String>,
}
impl SriEntry {
pub fn new(alg: &str, val: &str, opt: Option<String>) -> SriEntry {
SriEntry {
alg: alg.to_owned(),
val: val.to_owned(),
opt: opt,
}
}
}
/// <https://w3c.github.io/webappsec-subresource-integrity/#parse-metadata>
pub fn parsed_metadata(integrity_metadata: &str) -> Vec<SriEntry> {
// Step 1
let mut result = vec![];
// Step 3
let tokens = split_html_space_chars(integrity_metadata);
for token in tokens {
let parsed_data: Vec<&str> = token.split("-").collect();
if parsed_data.len() > 1 {
let alg = parsed_data[0];
if !SUPPORTED_ALGORITHM.contains(&alg) {
continue;
}
let data: Vec<&str> = parsed_data[1].split("?").collect();
let digest = data[0];
let opt = if data.len() > 1 {
Some(data[1].to_owned())
} else {
None
};
result.push(SriEntry::new(alg, digest, opt));
}
}
return result;
}
/// <https://w3c.github.io/webappsec-subresource-integrity/#getprioritizedhashfunction>
pub fn get_prioritized_hash_function(hash_func_left: &str, hash_func_right: &str) -> Option<String> {
let left_priority = SUPPORTED_ALGORITHM.iter().position(|s| s.to_owned() == hash_func_left).unwrap();
let right_priority = SUPPORTED_ALGORITHM.iter().position(|s| s.to_owned() == hash_func_right).unwrap();
if left_priority == right_priority {
return None;
}
if left_priority > right_priority {
Some(hash_func_left.to_owned())
} else {
Some(hash_func_right.to_owned())
}
}
/// <https://w3c.github.io/webappsec-subresource-integrity/#get-the-strongest-metadata>
pub fn get_strongest_metadata(integrity_metadata_list: Vec<SriEntry>) -> Vec<SriEntry> {
let mut result: Vec<SriEntry> = vec![integrity_metadata_list[0].clone()];
let mut current_algorithm = result[0].alg.clone();
for integrity_metadata in &integrity_metadata_list[1..] {
let prioritized_hash = get_prioritized_hash_function(&integrity_metadata.alg,
&*current_algorithm);
if prioritized_hash.is_none() {
result.push(integrity_metadata.clone());
} else if let Some(algorithm) = prioritized_hash {
if algorithm != current_algorithm {
result = vec![integrity_metadata.clone()];
current_algorithm = algorithm;
}
}
}
result
}
/// <https://w3c.github.io/webappsec-subresource-integrity/#apply-algorithm-to-response>
fn apply_algorithm_to_response(body: MutexGuard<ResponseBody>,
message_digest: MessageDigest)
-> String {
if let ResponseBody::Done(ref vec) = *body {
let response_digest = hash2(message_digest, vec).unwrap(); //Now hash2
base64::encode(&response_digest)
} else {
unreachable!("Tried to calculate digest of incomplete response body")
}
}
/// <https://w3c.github.io/webappsec-subresource-integrity/#is-response-eligible>
fn is_eligible_for_integrity_validation(response: &Response) -> bool {
match response.response_type {
ResponseType::Basic | ResponseType::Default | ResponseType::Cors => true,
_ => false,
}
}
/// <https://w3c.github.io/webappsec-subresource-integrity/#does-response-match-metadatalist>
pub fn is_response_integrity_valid(integrity_metadata: &str, response: &Response) -> bool {
let parsed_metadata_list: Vec<SriEntry> = parsed_metadata(integrity_metadata);
// Step 2 & 4
if parsed_metadata_list.is_empty() {
return true;
}
// Step 3
if !is_eligible_for_integrity_validation(response) {
return false;
}
// Step 5
let metadata: Vec<SriEntry> = get_strongest_metadata(parsed_metadata_list);
for item in metadata {
let body = response.body.lock().unwrap();
let algorithm = item.alg;
let digest = item.val;
let message_digest = match &*algorithm {
"sha256" => MessageDigest::sha256(),
"sha384" => MessageDigest::sha384(),
"sha512" => MessageDigest::sha512(),
_ => continue,
};
if apply_algorithm_to_response(body, message_digest) == digest {
return true;
}
}
false
}
pub fn split_html_space_chars<'a>(s: &'a str) ->
Filter<Split<'a, StaticCharVec>, fn(&&str) -> bool> {
fn not_empty(&split: &&str) -> bool { !split.is_empty() }
s.split(HTML_SPACE_CHARACTERS).filter(not_empty as fn(&&str) -> bool)
}
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