tor_cert/
encode.rs

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1//! Code for constructing and signing certificates.
2//!
3//! Only available when the crate is built with the `encode` feature.
4
5use crate::{
6    CertEncodeError, CertExt, Ed25519Cert, Ed25519CertConstructor, ExtType, SignedWithEd25519Ext,
7    UnrecognizedExt,
8};
9use std::time::{Duration, SystemTime};
10use tor_bytes::{EncodeResult, Writeable, Writer};
11use tor_llcrypto::pk::ed25519::{self, Ed25519PublicKey, Ed25519SigningKey};
12
13use derive_more::{AsRef, Deref, Into};
14
15/// An encoded ed25519 certificate,
16/// created using [`Ed25519CertConstructor::encode_and_sign`].
17///
18/// The certificate is encoded in the format specified
19/// in Tor's cert-spec.txt.
20///
21/// This certificate has already been validated.
22#[derive(Clone, Debug, PartialEq, Into, AsRef, Deref)]
23#[cfg_attr(docsrs, doc(cfg(feature = "encode")))]
24pub struct EncodedEd25519Cert(Vec<u8>);
25
26impl Ed25519Cert {
27    /// Return a new `Ed25519CertConstructor` to create and return a new signed
28    /// `Ed25519Cert`.
29    pub fn constructor() -> Ed25519CertConstructor {
30        Default::default()
31    }
32}
33
34impl EncodedEd25519Cert {
35    /// Create an `EncodedEd25519Cert` from a byte slice.
36    ///
37    /// **Important**: generally you should not use this function.
38    /// Instead, prefer using [`Ed25519CertConstructor::encode_and_sign`]
39    /// to encode certificates.
40    ///
41    /// This function should only be used if `cert`
42    /// is known to be the byte representation of a valid `EncodedEd25519Cert`
43    /// (for example, after parsing the byte slice using [`Ed25519Cert::decode`],
44    /// and validating its signature and timeliness).
45    #[cfg(feature = "experimental-api")]
46    pub fn dangerously_from_bytes(cert: &[u8]) -> Self {
47        Self(cert.into())
48    }
49}
50
51impl Writeable for CertExt {
52    /// As Writeable::WriteOnto, but may return an error.
53    ///
54    /// TODO: Migrate Writeable to provide this interface.
55    fn write_onto<B: Writer + ?Sized>(&self, w: &mut B) -> EncodeResult<()> {
56        match self {
57            CertExt::SignedWithEd25519(pk) => pk.write_onto(w),
58            CertExt::Unrecognized(u) => u.write_onto(w),
59        }
60    }
61}
62
63impl Writeable for SignedWithEd25519Ext {
64    /// As Writeable::WriteOnto, but may return an error.
65    fn write_onto<B: Writer + ?Sized>(&self, w: &mut B) -> EncodeResult<()> {
66        // body length
67        w.write_u16(32);
68        // Signed-with-ed25519-key-extension
69        w.write_u8(ExtType::SIGNED_WITH_ED25519_KEY.into());
70        // flags = 0.
71        w.write_u8(0);
72        // body
73        w.write_all(self.pk.as_bytes());
74        Ok(())
75    }
76}
77
78impl Writeable for UnrecognizedExt {
79    /// As Writeable::WriteOnto, but may return an error.
80    fn write_onto<B: Writer + ?Sized>(&self, w: &mut B) -> EncodeResult<()> {
81        // We can't use Writer::write_nested_u16len here, since the length field
82        // doesn't include the type or the flags.
83        w.write_u16(
84            self.body
85                .len()
86                .try_into()
87                .map_err(|_| tor_bytes::EncodeError::BadLengthValue)?,
88        );
89        w.write_u8(self.ext_type.into());
90        let flags = u8::from(self.affects_validation);
91        w.write_u8(flags);
92        w.write_all(&self.body[..]);
93        Ok(())
94    }
95}
96
97impl Ed25519CertConstructor {
98    /// Set the approximate expiration time for this certificate.
99    ///
100    /// (The time will be rounded forward to the nearest hour after the epoch.)
101    pub fn expiration(&mut self, expiration: SystemTime) -> &mut Self {
102        /// The number of seconds in an hour.
103        const SEC_PER_HOUR: u64 = 3600;
104        let duration = expiration
105            .duration_since(SystemTime::UNIX_EPOCH)
106            .unwrap_or(Duration::from_secs(0));
107        let exp_hours = duration.as_secs().saturating_add(SEC_PER_HOUR - 1) / SEC_PER_HOUR;
108        self.exp_hours = Some(exp_hours.try_into().unwrap_or(u32::MAX));
109        self
110    }
111
112    /// Set the signing key to be included with this certificate.
113    ///
114    /// This is optional: you don't need to include the signing key at all.  If
115    /// you do, it must match the key that you actually use to sign the
116    /// certificate.
117    pub fn signing_key(&mut self, key: ed25519::Ed25519Identity) -> &mut Self {
118        self.clear_signing_key();
119        self.signed_with = Some(Some(key));
120        self.extensions
121            .get_or_insert_with(Vec::new)
122            .push(CertExt::SignedWithEd25519(SignedWithEd25519Ext { pk: key }));
123
124        self
125    }
126
127    /// Remove any signing key previously set on this Ed25519CertConstructor.
128    pub fn clear_signing_key(&mut self) -> &mut Self {
129        self.signed_with = None;
130        self.extensions
131            .get_or_insert_with(Vec::new)
132            .retain(|ext| !matches!(ext, CertExt::SignedWithEd25519(_)));
133        self
134    }
135
136    /// Encode a certificate into a new vector, signing the result
137    /// with `skey`.
138    ///
139    /// This function exists in lieu of a `build()` function, since we have a rule that
140    /// we don't produce an `Ed25519Cert` except if the certificate is known to be
141    /// valid.
142    pub fn encode_and_sign<S>(&self, skey: &S) -> Result<EncodedEd25519Cert, CertEncodeError>
143    where
144        S: Ed25519PublicKey + Ed25519SigningKey,
145    {
146        let Ed25519CertConstructor {
147            exp_hours,
148            cert_type,
149            cert_key,
150            extensions,
151            signed_with,
152        } = self;
153
154        // As long as there is no setter for Ed25519Cert::signed_with, this is unreachable
155        if let Some(Some(signer)) = &signed_with {
156            if *signer != skey.public_key().into() {
157                return Err(CertEncodeError::KeyMismatch);
158            }
159        }
160
161        let mut w = Vec::new();
162        w.write_u8(1); // Version
163        w.write_u8(
164            cert_type
165                .ok_or(CertEncodeError::MissingField("cert_type"))?
166                .into(),
167        );
168        w.write_u32(exp_hours.ok_or(CertEncodeError::MissingField("expiration"))?);
169        let cert_key = cert_key
170            .clone()
171            .ok_or(CertEncodeError::MissingField("cert_key"))?;
172        w.write_u8(cert_key.key_type().into());
173        w.write_all(cert_key.as_bytes());
174        let extensions = extensions.as_ref().map(Vec::as_slice).unwrap_or(&[]);
175        w.write_u8(
176            extensions
177                .len()
178                .try_into()
179                .map_err(|_| CertEncodeError::TooManyExtensions)?,
180        );
181
182        for e in extensions.iter() {
183            e.write_onto(&mut w)?;
184        }
185
186        let signature = skey.sign(&w[..]);
187        w.write(&signature)?;
188        Ok(EncodedEd25519Cert(w))
189    }
190}
191
192#[cfg(test)]
193#[allow(clippy::unwrap_used)]
194mod test {
195    // @@ begin test lint list maintained by maint/add_warning @@
196    #![allow(clippy::bool_assert_comparison)]
197    #![allow(clippy::clone_on_copy)]
198    #![allow(clippy::dbg_macro)]
199    #![allow(clippy::mixed_attributes_style)]
200    #![allow(clippy::print_stderr)]
201    #![allow(clippy::print_stdout)]
202    #![allow(clippy::single_char_pattern)]
203    #![allow(clippy::unwrap_used)]
204    #![allow(clippy::unchecked_duration_subtraction)]
205    #![allow(clippy::useless_vec)]
206    #![allow(clippy::needless_pass_by_value)]
207    //! <!-- @@ end test lint list maintained by maint/add_warning @@ -->
208    use super::*;
209    use crate::CertifiedKey;
210    use tor_checkable::{SelfSigned, Timebound};
211
212    #[test]
213    fn signed_cert_without_key() {
214        let mut rng = rand::rng();
215        let keypair = ed25519::Keypair::generate(&mut rng);
216        let now = SystemTime::now();
217        let day = Duration::from_secs(86400);
218        let encoded = Ed25519Cert::constructor()
219            .expiration(now + day * 30)
220            .cert_key(CertifiedKey::Ed25519(keypair.verifying_key().into()))
221            .cert_type(7.into())
222            .encode_and_sign(&keypair)
223            .unwrap();
224
225        let decoded = Ed25519Cert::decode(&encoded).unwrap(); // Well-formed?
226        let validated = decoded
227            .should_be_signed_with(&keypair.verifying_key().into())
228            .unwrap()
229            .check_signature()
230            .unwrap(); // Well-signed?
231        let cert = validated.check_valid_at(&(now + day * 20)).unwrap();
232        assert_eq!(cert.cert_type(), 7.into());
233        if let CertifiedKey::Ed25519(found) = cert.subject_key() {
234            assert_eq!(found, &keypair.verifying_key().into());
235        } else {
236            panic!("wrong key type");
237        }
238        assert!(cert.signing_key() == Some(&keypair.verifying_key().into()));
239    }
240
241    #[test]
242    fn unrecognized_ext() {
243        use hex_literal::hex;
244        use tor_bytes::Reader;
245
246        let mut reader = Reader::from_slice(&hex!("0001 2A 00 2A"));
247        let ext: CertExt = reader.extract().unwrap();
248
249        let mut encoded: Vec<u8> = Vec::new();
250        encoded.write(&ext).unwrap();
251
252        assert_eq!(encoded, hex!("0001 2A 00 2A"));
253    }
254}
tor_cert/encode.rs

tor_cert/
encode.rs
