recognize wildcard names

Author: Geal

src/name.rs

@@ -24,6 +24,26 @@ use std::string::String;
 #[cfg(feature = "std")]
 use std::vec::Vec;
 
+/// A DNS Name suitable for use in the TLS Server Name Indication (SNI)
+/// extension and/or for use as the reference hostname for which to verify a
+/// certificate.
+pub enum GeneralDNSNameRef<'name> {
+    /// a valid DNS name
+    DNSName(DNSNameRef<'name>),
+    /// a DNS name containing a wildcard
+    Wildcard(WildcardDNSNameRef<'name>),
+}
+
+impl<'a> From<GeneralDNSNameRef<'a>> for &'a str {
+    fn from(d: GeneralDNSNameRef<'a>) -> Self {
+        match d {
+            GeneralDNSNameRef::DNSName(name) => name.into(),
+            GeneralDNSNameRef::Wildcard(name) => name.into(),
+        }
+    }
+}
+
+
 /// A DNS Name suitable for use in the TLS Server Name Indication (SNI)
 /// extension and/or for use as the reference hostname for which to verify a
 /// certificate.
@@ -132,6 +152,104 @@ impl<'a> From<DNSNameRef<'a>> for &'a str {
     }
 }
 
+/// A reference to a DNS Name suitable for use in the TLS Server Name Indication
+/// (SNI) extension and/or for use as the reference hostname for which to verify
+/// a certificate. Compared to `DNSName`, this one will store domain names containing
+/// a wildcard.
+///
+/// A `WildcardDNSName` is guaranteed to be syntactically valid. The validity rules are
+/// specified in [RFC 5280 Section 7.2], except that underscores are also
+/// allowed, and following [RFC 6125].
+///
+/// `WildcardDNSName` stores a copy of the input it was constructed from in a `String`
+/// and so it is only available when the `std` default feature is enabled.
+///
+/// `Eq`, `PartialEq`, etc. are not implemented because name comparison
+/// frequently should be done case-insensitively and/or with other caveats that
+/// depend on the specific circumstances in which the comparison is done.
+///
+/// [RFC 5280 Section 7.2]: https://tools.ietf.org/html/rfc5280#section-7.2
+/// [RFC 6125]: https://tools.ietf.org/html/rfc6125
+#[cfg(feature = "std")]
+#[derive(Clone, Debug, Eq, PartialEq, Hash)]
+pub struct WildcardDNSName(String);
+
+#[cfg(feature = "std")]
+impl WildcardDNSName {
+    /// Returns a `WildcardDNSNameRef` that refers to this `WildcardDNSName`.
+    pub fn as_ref(&self) -> WildcardDNSNameRef { WildcardDNSNameRef(self.0.as_bytes()) }
+}
+
+#[cfg(feature = "std")]
+impl AsRef<str> for WildcardDNSName {
+    fn as_ref(&self) -> &str { self.0.as_ref() }
+}
+
+// Deprecated
+#[cfg(feature = "std")]
+impl From<WildcardDNSNameRef<'_>> for WildcardDNSName {
+    fn from(dns_name: WildcardDNSNameRef) -> Self { dns_name.to_owned() }
+}
+
+/// A reference to a DNS Name suitable for use in the TLS Server Name Indication
+/// (SNI) extension and/or for use as the reference hostname for which to verify
+/// a certificate.
+///
+/// A `WildcardDNSNameRef` is guaranteed to be syntactically valid. The validity rules
+/// are specified in [RFC 5280 Section 7.2], except that underscores are also
+/// allowed.
+///
+/// `Eq`, `PartialEq`, etc. are not implemented because name comparison
+/// frequently should be done case-insensitively and/or with other caveats that
+/// depend on the specific circumstances in which the comparison is done.
+///
+/// [RFC 5280 Section 7.2]: https://tools.ietf.org/html/rfc5280#section-7.2
+#[derive(Clone, Copy)]
+pub struct WildcardDNSNameRef<'a>(&'a[u8]);
+
+impl<'a> WildcardDNSNameRef<'a> {
+    /// Constructs a `WildcardDNSNameRef` from the given input if the input is a
+    /// syntactically-valid DNS name.
+    pub fn try_from_ascii(dns_name: &'a[u8]) -> Result<Self, InvalidDNSNameError> {
+        if !is_valid_wildcard_dns_id(untrusted::Input::from(dns_name)) {
+            return Err(InvalidDNSNameError);
+        }
+
+        Ok(Self(dns_name))
+    }
+
+    /// Constructs a `WildcardDNSNameRef` from the given input if the input is a
+    /// syntactically-valid DNS name.
+    pub fn try_from_ascii_str(dns_name: &'a str) -> Result<Self, InvalidDNSNameError> {
+        Self::try_from_ascii(dns_name.as_bytes())
+    }
+
+    /// Constructs a `WildcardDNSName` from this `WildcardDNSNameRef`
+    #[cfg(feature = "std")]
+    pub fn to_owned(&self) -> WildcardDNSName {
+        // WildcardDNSNameRef is already guaranteed to be valid ASCII, which is a
+        // subset of UTF-8.
+        let s: &str = self.clone().into();
+        WildcardDNSName(s.to_ascii_lowercase())
+    }
+}
+
+#[cfg(feature = "std")]
+impl core::fmt::Debug for WildcardDNSNameRef<'_> {
+    fn fmt(&self, f: &mut core::fmt::Formatter) -> Result<(), core::fmt::Error> {
+        let lowercase = self.clone().to_owned();
+        f.debug_tuple("WildcardDNSNameRef").field(&lowercase.0).finish()
+    }
+}
+
+impl<'a> From<WildcardDNSNameRef<'a>> for &'a str {
+    fn from(WildcardDNSNameRef(d): WildcardDNSNameRef<'a>) -> Self {
+        // The unwrap won't fail because DNSNameRefs are guaranteed to be ASCII
+        // and ASCII is a subset of UTF-8.
+        core::str::from_utf8(d).unwrap()
+    }
+}
+
 pub fn verify_cert_dns_name(
     cert: &super::EndEntityCert, DNSNameRef(dns_name): DNSNameRef,
 ) -> Result<(), Error> {
@@ -163,14 +281,15 @@ pub fn verify_cert_dns_name(
 
 #[cfg(feature = "std")]
 pub fn list_cert_dns_names<'names>(cert: &super::EndEntityCert<'names>)
-                                   -> Result<Vec<DNSNameRef<'names>>, Error> {
+                                   -> Result<Vec<GeneralDNSNameRef<'names>>, Error> {
     let cert = &cert.inner;
     let names = std::cell::RefCell::new(Vec::new());
 
     iterate_names(cert.subject, cert.subject_alt_name, Ok(()), &|name| {
         match name {
             GeneralName::DNSName(presented_id) => {
-                match DNSNameRef::try_from_ascii(presented_id) {
+                match DNSNameRef::try_from_ascii(presented_id.as_slice_less_safe()).map(GeneralDNSNameRef::DNSName)
+                    .or_else(|_| WildcardDNSNameRef::try_from_ascii(presented_id.as_slice_less_safe()).map(GeneralDNSNameRef::Wildcard)) {
                     Ok(name) => names.borrow_mut().push(name),
                     Err(_) => { /* keep going */ },
                 };
@@ -783,6 +902,10 @@ fn is_valid_reference_dns_id(hostname: untrusted::Input) -> bool {
     is_valid_dns_id(hostname, IDRole::ReferenceID, AllowWildcards::No)
 }
 
+fn is_valid_wildcard_dns_id(hostname: untrusted::Input) -> bool {
+    is_valid_dns_id(hostname, IDRole::ReferenceID, AllowWildcards::Yes)
+}
+
 // https://tools.ietf.org/html/rfc5280#section-4.2.1.6:
 //
 //   When the subjectAltName extension contains a domain name system

src/webpki.rs

@@ -60,7 +60,7 @@ pub mod trust_anchor_util;
 mod verify_cert;
 
 pub use error::Error;
-pub use name::{DNSNameRef, InvalidDNSNameError};
+pub use name::{GeneralDNSNameRef, DNSNameRef, WildcardDNSNameRef, InvalidDNSNameError};
 
 #[cfg(feature = "std")]
 pub use name::DNSName;
@@ -251,7 +251,7 @@ impl<'a> EndEntityCert<'a> {
     /// Requires the `std` default feature; i.e. this isn't available in
     /// `#![no_std]` configurations.
     #[cfg(feature = "std")]
-    pub fn dns_names(&self) -> Result<Vec<DNSNameRef<'a>>, Error> {
+    pub fn dns_names(&self) -> Result<Vec<GeneralDNSNameRef<'a>>, Error> {
         name::list_cert_dns_names(&self)
     }
 }

tests/integration.rs

@@ -161,7 +161,7 @@ pub fn wildcard_subject_alternative_names()
 
     expect_cert_dns_names(data, &[
         "account.netflix.com",
-        // NOT "c*.netflix.com",
+        "*.netflix.com",
         "netflix.ca",
         "netflix.com",
         "signup.netflix.com",
@@ -180,8 +180,7 @@ fn expect_cert_dns_names(data: &[u8], expected_names: &[&str])
 {
     use std::iter::FromIterator;
 
-    let input = untrusted::Input::from(data);
-    let cert = webpki::EndEntityCert::from(input)
+    let cert = webpki::EndEntityCert::from(data)
       .expect("should parse end entity certificate correctly");
 
     let expected_names =
@@ -207,8 +206,7 @@ pub fn no_subject_alt_names()
 {
     let data = include_bytes!("misc/no_subject_alternative_name.der");
 
-    let input = untrusted::Input::from(data);
-    let cert = webpki::EndEntityCert::from(input)
+    let cert = webpki::EndEntityCert::from(data)
       .expect("should parse end entity certificate correctly");
 
     let names = cert.dns_names().expect("we should get a result even without subjectAltNames");