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// Copyright 2015-2021 Brian Smith.
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR
// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
#[cfg(feature = "alloc")]
use crate::subject_name::GeneralDnsNameRef;
use crate::{
cert, signed_data, subject_name, verify_cert, CertRevocationList, Error, KeyUsage,
SignatureAlgorithm, SubjectNameRef, Time, TrustAnchor,
};
#[allow(deprecated)]
use crate::{TlsClientTrustAnchors, TlsServerTrustAnchors};
/// An end-entity certificate.
///
/// Server certificate processing in a TLS connection consists of several
/// steps. All of these steps are necessary:
///
/// * `EndEntityCert.verify_is_valid_tls_server_cert`: Verify that the server's
/// certificate is currently valid *for use by a TLS server*.
/// * `EndEntityCert.verify_is_valid_for_subject_name`: Verify that the server's
/// certificate is valid for the host or IP address that is being connected to.
///
/// * `EndEntityCert.verify_signature`: Verify that the signature of server's
/// `ServerKeyExchange` message is valid for the server's certificate.
///
/// Client certificate processing in a TLS connection consists of analogous
/// steps. All of these steps are necessary:
///
/// * `EndEntityCert.verify_is_valid_tls_client_cert`: Verify that the client's
/// certificate is currently valid *for use by a TLS client*.
/// * `EndEntityCert.verify_signature`: Verify that the client's signature in
/// its `CertificateVerify` message is valid using the public key from the
/// client's certificate.
///
/// Although it would be less error-prone to combine all these steps into a
/// single function call, some significant optimizations are possible if the
/// three steps are processed separately (in parallel). It does not matter much
/// which order the steps are done in, but **all of these steps must completed
/// before application data is sent and before received application data is
/// processed**. `EndEntityCert::from` is an inexpensive operation and is
/// deterministic, so if these tasks are done in multiple threads, it is
/// probably best to just call `EndEntityCert::from` multiple times (before each
/// operation) for the same DER-encoded ASN.1 certificate bytes.
pub struct EndEntityCert<'a> {
inner: cert::Cert<'a>,
}
impl<'a> TryFrom<&'a [u8]> for EndEntityCert<'a> {
type Error = Error;
/// Parse the ASN.1 DER-encoded X.509 encoding of the certificate
/// `cert_der`.
fn try_from(cert_der: &'a [u8]) -> Result<Self, Self::Error> {
Ok(Self {
inner: cert::Cert::from_der(
untrusted::Input::from(cert_der),
cert::EndEntityOrCa::EndEntity,
)?,
})
}
}
impl<'a> EndEntityCert<'a> {
pub(super) fn inner(&self) -> &cert::Cert {
&self.inner
}
fn verify_is_valid_cert(
&self,
supported_sig_algs: &[&SignatureAlgorithm],
trust_anchors: &[TrustAnchor],
intermediate_certs: &[&[u8]],
time: Time,
eku: KeyUsage,
crls: &[&dyn CertRevocationList],
) -> Result<(), Error> {
verify_cert::build_chain(
&verify_cert::ChainOptions {
eku,
supported_sig_algs,
trust_anchors,
intermediate_certs,
crls,
},
&self.inner,
time,
)
}
/// Verifies that the end-entity certificate is valid for use against the
/// specified Extended Key Usage (EKU).
///
/// * `supported_sig_algs` is the list of signature algorithms that are
/// trusted for use in certificate signatures; the end-entity certificate's
/// public key is not validated against this list.
/// * `trust_anchors` is the list of root CAs to trust
/// * `intermediate_certs` is the sequence of intermediate certificates that
/// the server sent in the TLS handshake.
/// * `time` is the time for which the validation is effective (usually the
/// current time).
/// * `usage` is the intended usage of the certificate, indicating what kind
/// of usage we're verifying the certificate for.
/// * `crls` is the list of certificate revocation lists to check
/// the certificate against.
pub fn verify_for_usage(
&self,
supported_sig_algs: &[&SignatureAlgorithm],
trust_anchors: &[TrustAnchor],
intermediate_certs: &[&[u8]],
time: Time,
usage: KeyUsage,
crls: &[&dyn CertRevocationList],
) -> Result<(), Error> {
self.verify_is_valid_cert(
supported_sig_algs,
trust_anchors,
intermediate_certs,
time,
usage,
crls,
)
}
/// Verifies that the end-entity certificate is valid for use by a TLS
/// server.
///
/// `supported_sig_algs` is the list of signature algorithms that are
/// trusted for use in certificate signatures; the end-entity certificate's
/// public key is not validated against this list. `trust_anchors` is the
/// list of root CAs to trust. `intermediate_certs` is the sequence of
/// intermediate certificates that the server sent in the TLS handshake.
/// `time` is the time for which the validation is effective (usually the
/// current time).
#[allow(deprecated)]
#[deprecated(
since = "0.101.2",
note = "The per-usage trust anchor representations and verification functions are deprecated in \
favor of the general-purpose `TrustAnchor` type and `EndEntity::verify_for_usage` function. \
The new `verify_for_usage` function expresses trust anchor and end entity purpose with the \
key usage argument."
)]
pub fn verify_is_valid_tls_server_cert(
&self,
supported_sig_algs: &[&SignatureAlgorithm],
&TlsServerTrustAnchors(trust_anchors): &TlsServerTrustAnchors,
intermediate_certs: &[&[u8]],
time: Time,
) -> Result<(), Error> {
self.verify_is_valid_cert(
supported_sig_algs,
trust_anchors,
intermediate_certs,
time,
KeyUsage::server_auth(),
&[],
)
}
/// Verifies that the end-entity certificate is valid for use by a TLS
/// client.
///
/// `supported_sig_algs` is the list of signature algorithms that are
/// trusted for use in certificate signatures; the end-entity certificate's
/// public key is not validated against this list. `trust_anchors` is the
/// list of root CAs to trust. `intermediate_certs` is the sequence of
/// intermediate certificates that the client sent in the TLS handshake.
/// `cert` is the purported end-entity certificate of the client. `time` is
/// the time for which the validation is effective (usually the current
/// time).
#[allow(deprecated)]
#[deprecated(
since = "0.101.2",
note = "The per-usage trust anchor representations and verification functions are deprecated in \
favor of the general-purpose `TrustAnchor` type and `EndEntity::verify_for_usage` function. \
The new `verify_for_usage` function expresses trust anchor and end entity purpose with the \
key usage argument."
)]
pub fn verify_is_valid_tls_client_cert(
&self,
supported_sig_algs: &[&SignatureAlgorithm],
&TlsClientTrustAnchors(trust_anchors): &TlsClientTrustAnchors,
intermediate_certs: &[&[u8]],
time: Time,
crls: &[&dyn CertRevocationList],
) -> Result<(), Error> {
self.verify_is_valid_cert(
supported_sig_algs,
trust_anchors,
intermediate_certs,
time,
KeyUsage::client_auth(),
crls,
)
}
/// Verifies that the certificate is valid for the given Subject Name.
pub fn verify_is_valid_for_subject_name(
&self,
subject_name: SubjectNameRef,
) -> Result<(), Error> {
subject_name::verify_cert_subject_name(self, subject_name)
}
/// Verifies the signature `signature` of message `msg` using the
/// certificate's public key.
///
/// `signature_alg` is the algorithm to use to
/// verify the signature; the certificate's public key is verified to be
/// compatible with this algorithm.
///
/// For TLS 1.2, `signature` corresponds to TLS's
/// `DigitallySigned.signature` and `signature_alg` corresponds to TLS's
/// `DigitallySigned.algorithm` of TLS type `SignatureAndHashAlgorithm`. In
/// TLS 1.2 a single `SignatureAndHashAlgorithm` may map to multiple
/// `SignatureAlgorithm`s. For example, a TLS 1.2
/// `SignatureAndHashAlgorithm` of (ECDSA, SHA-256) may map to any or all
/// of {`ECDSA_P256_SHA256`, `ECDSA_P384_SHA256`}, depending on how the TLS
/// implementation is configured.
///
/// For current TLS 1.3 drafts, `signature_alg` corresponds to TLS's
/// `algorithm` fields of type `SignatureScheme`. There is (currently) a
/// one-to-one correspondence between TLS 1.3's `SignatureScheme` and
/// `SignatureAlgorithm`.
pub fn verify_signature(
&self,
signature_alg: &SignatureAlgorithm,
msg: &[u8],
signature: &[u8],
) -> Result<(), Error> {
signed_data::verify_signature(
signature_alg,
self.inner.spki.value(),
untrusted::Input::from(msg),
untrusted::Input::from(signature),
)
}
/// Returns a list of the DNS names provided in the subject alternative names extension
///
/// This function must not be used to implement custom DNS name verification.
/// Verification functions are already provided as `verify_is_valid_for_dns_name`
/// and `verify_is_valid_for_at_least_one_dns_name`.
#[cfg(feature = "alloc")]
#[cfg_attr(docsrs, doc(cfg(feature = "alloc")))]
pub fn dns_names(&'a self) -> Result<impl Iterator<Item = GeneralDnsNameRef<'a>>, Error> {
subject_name::list_cert_dns_names(self)
}
}
#[cfg(feature = "alloc")]
#[cfg(test)]
mod tests {
use super::*;
use crate::test_utils;
// This test reproduces https://github.com/rustls/webpki/issues/167 --- an
// end-entity cert where the common name is a `PrintableString` rather than
// a `UTF8String` cannot iterate over its subject alternative names.
#[test]
fn printable_string_common_name() {
const DNS_NAME: &str = "test.example.com";
let issuer = test_utils::make_issuer("Test", None);
let ee_cert_der = {
let mut params = rcgen::CertificateParams::new(vec![DNS_NAME.to_string()]);
// construct a certificate that uses `PrintableString` as the
// common name value, rather than `UTF8String`.
params.distinguished_name.push(
rcgen::DnType::CommonName,
rcgen::DnValue::PrintableString("example.com".to_string()),
);
params.is_ca = rcgen::IsCa::ExplicitNoCa;
params.alg = test_utils::RCGEN_SIGNATURE_ALG;
let cert = rcgen::Certificate::from_params(params)
.expect("failed to make ee cert (this is a test bug)");
cert.serialize_der_with_signer(&issuer)
.expect("failed to serialize signed ee cert (this is a test bug)")
};
expect_dns_name(&ee_cert_der, DNS_NAME);
}
// This test reproduces https://github.com/rustls/webpki/issues/167 --- an
// end-entity cert where the common name is an empty SEQUENCE.
#[test]
fn empty_sequence_common_name() {
// handcrafted cert DER produced using `ascii2der`, since `rcgen` is
// unwilling to generate this particular weird cert.
let ee_cert_der = include_bytes!("../tests/misc/empty_sequence_common_name.der").as_slice();
expect_dns_name(ee_cert_der, "example.com");
}
fn expect_dns_name(der: &[u8], name: &str) {
let cert =
EndEntityCert::try_from(der).expect("should parse end entity certificate correctly");
let mut names = cert
.dns_names()
.expect("should get all DNS names correctly for end entity cert");
assert_eq!(names.next().map(<&str>::from), Some(name));
assert_eq!(names.next().map(<&str>::from), None);
}
}