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
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
// 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.

use crate::{
    cert, name, signed_data, verify_cert, DnsNameRef, Error, SignatureAlgorithm, Time,
    TlsClientTrustAnchors, TlsServerTrustAnchors,
};

#[cfg(feature = "alloc")]
use alloc::vec::Vec;

/// 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_dns_name`: Verify that the server's
///   certificate is valid for the host 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_is_valid_for_dns_name` or
///   `EndEntityCert.verify_is_valid_for_at_least_one_dns_name`: Verify that the
///   client's certificate is valid for the identity or identities used to
///   identify the client. (Currently client authentication only works when the
///   client is identified by one or more DNS hostnames.)
/// * `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> core::convert::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::parse_cert(
                untrusted::Input::from(cert_der),
                cert::EndEntityOrCa::EndEntity,
            )?,
        })
    }
}

impl<'a> EndEntityCert<'a> {
    pub(super) fn inner(&self) -> &cert::Cert {
        &self.inner
    }

    /// 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).
    pub fn verify_is_valid_tls_server_cert(
        &self,
        supported_sig_algs: &[&SignatureAlgorithm],
        &TlsServerTrustAnchors(trust_anchors): &TlsServerTrustAnchors,
        intermediate_certs: &[&[u8]],
        time: Time,
    ) -> Result<(), Error> {
        verify_cert::build_chain(
            verify_cert::EKU_SERVER_AUTH,
            supported_sig_algs,
            trust_anchors,
            intermediate_certs,
            &self.inner,
            time,
            0,
        )
    }

    /// Verifies that the end-entity certificate is valid for use by a TLS
    /// client.
    ///
    /// If the certificate is not valid for any of the given names then this
    /// fails with `Error::CertNotValidForName`.
    ///
    /// `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).
    pub fn verify_is_valid_tls_client_cert(
        &self,
        supported_sig_algs: &[&SignatureAlgorithm],
        &TlsClientTrustAnchors(trust_anchors): &TlsClientTrustAnchors,
        intermediate_certs: &[&[u8]],
        time: Time,
    ) -> Result<(), Error> {
        verify_cert::build_chain(
            verify_cert::EKU_CLIENT_AUTH,
            supported_sig_algs,
            trust_anchors,
            intermediate_certs,
            &self.inner,
            time,
            0,
        )
    }

    /// Verifies that the certificate is valid for the given DNS host name.
    pub fn verify_is_valid_for_dns_name(&self, dns_name: DnsNameRef) -> Result<(), Error> {
        name::verify_cert_dns_name(&self, dns_name)
    }

    /// Verifies that the certificate is valid for at least one of the given DNS
    /// host names.
    ///
    /// If the certificate is not valid for any of the given names then this
    /// fails with `Error::CertNotValidForName`. Otherwise the DNS names for
    /// which the certificate is valid are returned.
    ///
    /// Requires the `alloc` default feature; i.e. this isn't available in
    /// `#![no_std]` configurations.
    #[cfg(feature = "alloc")]
    pub fn verify_is_valid_for_at_least_one_dns_name<'names, Names>(
        &self,
        dns_names: Names,
    ) -> Result<Vec<DnsNameRef<'names>>, Error>
    where
        Names: Iterator<Item = DnsNameRef<'names>>,
    {
        let result: Vec<DnsNameRef<'names>> = dns_names
            .filter(|n| self.verify_is_valid_for_dns_name(*n).is_ok())
            .collect();
        if result.is_empty() {
            return Err(Error::CertNotValidForName);
        }
        Ok(result)
    }

    /// 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
    /// `ignatureAndHashAlgorithm` 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),
        )
    }
}