Struct Host

pub struct Host<'a>(/* private fields */);

A domain and port identified by a client as the server being messaged.

For requests made via HTTP/1.1, a host is identified via the HOST header. In HTTP/2 and HTTP/3, this information is instead communicated via the :authority and :port pseudo-header request fields. It is a client-controlled value via which the client communicates to the server the domain name and port it is attempting to communicate with. The following diagram illustrates the syntactic structure of a Host:

some.domain.foo:8088
|-------------| |--|
     domain     port

Only the domain part is required. Its value is case-insensitive.

URI Construction

A Host is not a Uri, and none of Rocket’s APIs will accept a Host value as such. This is because doing so would facilitate the construction of URIs to internal routes in a manner controllable by an attacker, inevitably leading to “HTTP Host header attacks”.

Instead, a Host must be checked before being converted to a [Uri] value. The Host::to_authority and Host::to_absolute methods provide these mechanisms:

use rocket::http::uri::Host;

// A sensitive URI we want to prefix with safe hosts.
#[get("/token?<secret>")]
fn token(secret: Token) { /* .. */ }

// Whitelist of known hosts. In a real setting, you might retrieve this
// list from config at ignite-time using tools like `AdHoc::config()`.
const WHITELIST: [Host<'static>; 4] = [
    Host::new(uri!("rocket.rs")),
    Host::new(uri!("rocket.rs:443")),
    Host::new(uri!("guide.rocket.rs")),
    Host::new(uri!("guide.rocket.rs:443")),
];

// Use `Host::to_absolute()` to case-insensitively check a host against a
// whitelist, returning an `Absolute` usable as a `uri!()` prefix.
let host = Host::new(uri!("guide.ROCKET.rs"));
let prefix = host.to_absolute("https", &WHITELIST);

// Since `guide.rocket.rs` is in the whitelist, `prefix` is `Some`.
assert!(prefix.is_some());
if let Some(prefix) = prefix {
    // We can use this prefix to safely construct URIs.
    let uri = uri!(prefix, token("some-secret-token"));
    assert_eq!(uri, "https://guide.ROCKET.rs/token?secret=some-secret-token");
}

(De)serialization

Host is both Serialize and Deserialize:

use serde::{Serialize, Deserialize};
use rocket::http::uri::Host;

#[derive(Deserialize, Serialize)]
struct UriOwned {
    uri: Host<'static>,
}

#[derive(Deserialize, Serialize)]
struct UriBorrowed<'a> {
    uri: Host<'a>,
}

Implementations

impl<'a> Host<'a>

pub const fn new(authority: Authority<'a>) -> Host<'a>

Create a new Host from an Authority. Only the host and port parts are preserved.

use rocket::http::uri::Host;

let host = Host::new(uri!("developer.mozilla.org"));
assert_eq!(host.to_string(), "developer.mozilla.org");

let host = Host::new(uri!("foo:bar@developer.mozilla.org:1234"));
assert_eq!(host.to_string(), "developer.mozilla.org:1234");

let host = Host::new(uri!("rocket.rs:443"));
assert_eq!(host.to_string(), "rocket.rs:443");

pub fn parse(string: &'a str) -> Result<Host<'a>, Error<'a>>

Parses the string string into a Host. Parsing will never allocate. Returns an Error if string is not a valid authority URI, meaning that this parser accepts a user_info part for compatibility but discards it.

Example

use rocket::http::uri::Host;

// Parse from a valid authority URI.
let host = Host::parse("user:pass@domain").expect("valid host");
assert_eq!(host.domain(), "domain");
assert_eq!(host.port(), None);

// Parse from a valid host.
let host = Host::parse("domain:311").expect("valid host");
assert_eq!(host.domain(), "doMaIN");
assert_eq!(host.port(), Some(311));

// Invalid hosts fail to parse.
Host::parse("https://rocket.rs").expect_err("invalid host");

// Prefer to use `uri!()` when the input is statically known:
let host = Host::new(uri!("domain"));
assert_eq!(host.domain(), "domain");
assert_eq!(host.port(), None);

pub fn parse_owned(string: String) -> Result<Host<'static>, Error<'static>>

Parses the string string into an Host. Parsing never allocates on success. May allocate on error.

This method should be used instead of Host::parse() when the source is already a String. Returns an Error if string is not a valid authority URI, meaning that this parser accepts a user_info part for compatibility but discards it.

Example

use rocket::http::uri::Host;

let source = format!("rocket.rs:8000");
let host = Host::parse_owned(source).expect("valid host");
assert_eq!(host.domain(), "rocket.rs");
assert_eq!(host.port(), Some(8000));

pub fn domain(&self) -> &UncasedStr

Returns the case-insensitive domain part of the host.

Example

use rocket::http::uri::Host;

let host = Host::new(uri!("domain.com:123"));
assert_eq!(host.domain(), "domain.com");

let host = Host::new(uri!("username:password@domain:123"));
assert_eq!(host.domain(), "domain");

let host = Host::new(uri!("[1::2]:123"));
assert_eq!(host.domain(), "[1::2]");

pub fn port(&self) -> Option<u16>

Returns the port part of the host, if there is one.

Example

use rocket::http::uri::Host;

// With a port.
let host = Host::new(uri!("domain:123"));
assert_eq!(host.port(), Some(123));

let host = Host::new(uri!("domain.com:8181"));
assert_eq!(host.port(), Some(8181));

// Without a port.
let host = Host::new(uri!("domain.foo.bar.tld"));
assert_eq!(host.port(), None);

pub fn to_authority<'h, W>(&self, whitelist: W) -> Option<Authority<'a>>

where W: IntoIterator<Item = &'h Host<'h>>,

Checks self against whitelist. If self is in whitelist, returns an Authority URI representing self. Otherwise, returns None. Domain comparison is case-insensitive.

See URI construction for more.

Example

use rocket::http::uri::Host;

let whitelist = &[Host::new(uri!("domain.tld"))];

// A host in the whitelist returns `Some`.
let host = Host::new(uri!("domain.tld"));
let uri = host.to_authority(whitelist);
assert!(uri.is_some());
assert_eq!(uri.unwrap().to_string(), "domain.tld");

let host = Host::new(uri!("foo:bar@doMaIN.tLd"));
let uri = host.to_authority(whitelist);
assert!(uri.is_some());
assert_eq!(uri.unwrap().to_string(), "doMaIN.tLd");

// A host _not_ in the whitelist returns `None`.
let host = Host::new(uri!("domain.tld:1234"));
let uri = host.to_authority(whitelist);
assert!(uri.is_none());

pub fn to_absolute<'h, W>( &self, scheme: &'a str, whitelist: W, ) -> Option<Absolute<'a>>

where W: IntoIterator<Item = &'h Host<'h>>,

Checks self against whitelist. If self is in whitelist, returns an Absolute URI representing self with scheme scheme. Otherwise, returns None. Domain comparison is case-insensitive.

See URI construction for more.

Example

use rocket::http::uri::Host;

let whitelist = &[Host::new(uri!("domain.tld:443"))];

// A host in the whitelist returns `Some`.
let host = Host::new(uri!("user@domain.tld:443"));
let uri = host.to_absolute("http", whitelist);
assert!(uri.is_some());
assert_eq!(uri.unwrap().to_string(), "http://domain.tld:443");

let host = Host::new(uri!("domain.TLD:443"));
let uri = host.to_absolute("https", whitelist);
assert!(uri.is_some());
assert_eq!(uri.unwrap().to_string(), "https://domain.TLD:443");

// A host _not_ in the whitelist returns `None`.
let host = Host::new(uri!("domain.tld"));
let uri = host.to_absolute("http", whitelist);
assert!(uri.is_none());

Trait Implementations

impl<'a> Clone for Host<'a>

fn clone(&self) -> Host<'a>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'a> Debug for Host<'a>

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<'a, 'de> Deserialize<'de> for Host<'a>

fn deserialize<D>( deserializer: D, ) -> Result<Host<'a>, <D as Deserializer<'de>>::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Display for Host<'_>

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<'a> From<Authority<'a>> for Host<'a>

fn from(auth: Authority<'a>) -> Host<'a>

Converts to this type from the input type.

impl<'r> FromRequest<'r> for &'r Host<'r>

type Error = Infallible

The associated error to be returned if derivation fails.

fn from_request<'life0, 'async_trait>( request: &'r Request<'life0>, ) -> Pin<Box<dyn Future<Output = Outcome<Self, Infallible>> + Send + 'async_trait>>

where Self: 'async_trait, 'r: 'async_trait, 'life0: 'async_trait,

Derives an instance of Self from the incoming request metadata.

impl Hash for Host<'_>

fn hash<H>(&self, state: &mut H)

where H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl IntoOwned for Host<'_>

type Owned = Host<'static>

The owned version of the type.

fn into_owned(self) -> Host<'static>

Converts self into an owned version of itself.

impl PartialEq<&str> for Host<'_>

fn eq(&self, other: &&str) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialEq<Host<'_>> for str

fn eq(&self, other: &Host<'_>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<'a, 'b> PartialEq<Host<'b>> for Host<'a>

fn eq(&self, other: &Host<'b>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialEq<str> for Host<'_>

fn eq(&self, string: &str) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<'a> Serialize for Host<'a>

fn serialize<S>( &self, serializer: S, ) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.

impl<'a> TryFrom<&'a String> for Host<'a>

type Error = Error<'a>

The type returned in the event of a conversion error.

fn try_from( value: &'a String, ) -> Result<Host<'a>, <Host<'a> as TryFrom<&'a String>>::Error>

Performs the conversion.

impl<'a> TryFrom<&'a str> for Host<'a>

type Error = Error<'a>

The type returned in the event of a conversion error.

fn try_from( value: &'a str, ) -> Result<Host<'a>, <Host<'a> as TryFrom<&'a str>>::Error>

Performs the conversion.

impl TryFrom<String> for Host<'static>

type Error = Error<'static>

The type returned in the event of a conversion error.

fn try_from( value: String, ) -> Result<Host<'static>, <Host<'static> as TryFrom<String>>::Error>

Performs the conversion.

impl Eq for Host<'_>