openpgp: Align hashing of compound objects with primitive objects.

3 files changed, 120 insertions, 115 deletions

diff --git a/openpgp/src/cert.rs b/openpgp/src/cert.rs
index f6232bc6..65a47486 100644
--- a/openpgp/src/cert.rs
+++ b/openpgp/src/cert.rs
@@ -1482,9 +1482,12 @@ impl Cert {
                     .into_iter()
                 {
                     // Use hash prefix as heuristic.
-                    match Signature::$hash_method(&sig,
-                                                  self.primary.key(),
-                                                  $($verify_args),*) {
+                    let key = self.primary.key();
+                    match sig.hash_algo().context().and_then(|mut ctx| {
+                        Signature::$hash_method(&mut ctx, &sig, key,
+                                                $($verify_args),*);
+                        ctx.into_digest()
+                    }) {
                       Ok(hash) => {
                         if &sig.digest_prefix()[..] == &hash[..2] {
                             // See if we can get the key for a
@@ -1706,8 +1709,14 @@ impl Cert {
                         }
                     } else {
                         // Use hash prefix as heuristic.
-                        if let Ok(hash) = Signature::$hash_method(
-                            &sig, self.primary.key(), $($verify_args),*) {
+                        let key = self.primary.key();
+                        if let Ok(hash) = sig.hash_algo().context()
+                            .and_then(|mut ctx| {
+                                Signature::$hash_method(&mut ctx, &sig, key,
+                                                        $($verify_args),*);
+                                ctx.into_digest()
+                            })
+                        {
                             if &sig.digest_prefix()[..] == &hash[..2] {
                                 t!("Sig {:02X}{:02X}, {:?} \
                                     was out of place.  Likely belongs to {}.",
diff --git a/openpgp/src/crypto/hash.rs b/openpgp/src/crypto/hash.rs
index 5517d205..9221e070 100644
--- a/openpgp/src/crypto/hash.rs
+++ b/openpgp/src/crypto/hash.rs
@@ -113,6 +113,13 @@ impl Context {
     pub fn digest<D: AsMut<[u8]>>(&mut self, mut digest: D) -> Result<()> {
         self.ctx.digest(digest.as_mut())
     }
+
+    /// Finalizes the hash function and computes the digest.
+    pub fn into_digest(mut self) -> Result<Vec<u8>> {
+        let mut digest = vec![0u8; self.digest_size()];
+        self.digest(&mut digest)?;
+        Ok(digest)
+    }
 }
 
 impl io::Write for Context {
@@ -382,112 +389,81 @@ impl Hash for signature::SignatureFields {
 /// <a name="hashing-functions"></a>
 impl Signature {
     /// Computes the message digest of standalone signatures.
-    pub fn hash_standalone(sig: &signature::SignatureFields)
-        -> Result<Vec<u8>>
+    pub fn hash_standalone(hash: &mut Context,
+                           sig: &signature::SignatureFields)
     {
-        let mut h = sig.hash_algo().context()?;
-
-        sig.hash(&mut h);
-
-        let mut digest = vec![0u8; h.digest_size()];
-        h.digest(&mut digest)?;
-        Ok(digest)
+        sig.hash(hash);
     }
 
     /// Computes the message digest of timestamp signatures.
-    pub fn hash_timestamp(sig: &signature::SignatureFields)
-        -> Result<Vec<u8>>
+    pub fn hash_timestamp(hash: &mut Context,
+                          sig: &signature::SignatureFields)
     {
-        Self::hash_standalone(sig)
+        Self::hash_standalone(hash, sig);
     }
 
     /// Returns the message digest of the direct key signature over
     /// the specified primary key.
-    pub fn hash_direct_key<P>(sig: &signature::SignatureFields,
+    pub fn hash_direct_key<P>(hash: &mut Context,
+                              sig: &signature::SignatureFields,
                               key: &Key<P, key::PrimaryRole>)
-        -> Result<Vec<u8>>
         where P: key::KeyParts,
     {
-
-        let mut h = sig.hash_algo().context()?;
-
-        key.hash(&mut h);
-        sig.hash(&mut h);
-
-        let mut digest = vec![0u8; h.digest_size()];
-        h.digest(&mut digest)?;
-        Ok(digest)
+        key.hash(hash);
+        sig.hash(hash);
     }
 
     /// Returns the message digest of the subkey binding over the
     /// specified primary key and subkey.
-    pub fn hash_subkey_binding<P, Q>(sig: &signature::SignatureFields,
+    pub fn hash_subkey_binding<P, Q>(hash: &mut Context,
+                                     sig: &signature::SignatureFields,
                                      key: &Key<P, key::PrimaryRole>,
                                      subkey: &Key<Q, key::SubordinateRole>)
-        -> Result<Vec<u8>>
         where P: key::KeyParts,
               Q: key::KeyParts,
     {
-        let mut h = sig.hash_algo().context()?;
-
-        key.hash(&mut h);
-        subkey.hash(&mut h);
-        sig.hash(&mut h);
-
-        let mut digest = vec![0u8; h.digest_size()];
-        h.digest(&mut digest)?;
-        Ok(digest)
+        key.hash(hash);
+        subkey.hash(hash);
+        sig.hash(hash);
     }
 
     /// Returns the message digest of the primary key binding over the
     /// specified primary key and subkey.
-    pub fn hash_primary_key_binding<P, Q>(sig: &signature::SignatureFields,
+    pub fn hash_primary_key_binding<P, Q>(hash: &mut Context,
+                                          sig: &signature::SignatureFields,
                                           key: &Key<P, key::PrimaryRole>,
                                           subkey: &Key<Q, key::SubordinateRole>)
-        -> Result<Vec<u8>>
         where P: key::KeyParts,
               Q: key::KeyParts,
     {
-        Self::hash_subkey_binding(sig, key, subkey)
+        Self::hash_subkey_binding(hash, sig, key, subkey);
     }
 
     /// Returns the message digest of the user ID binding over the
     /// specified primary key, user ID, and signature.
-    pub fn hash_userid_binding<P>(sig: &signature::SignatureFields,
+    pub fn hash_userid_binding<P>(hash: &mut Context,
+                                  sig: &signature::SignatureFields,
                                   key: &Key<P, key::PrimaryRole>,
                                   userid: &UserID)
-        -> Result<Vec<u8>>
         where P: key::KeyParts,
     {
-        let mut h = sig.hash_algo().context()?;
-
-        key.hash(&mut h);
-        userid.hash(&mut h);
-        sig.hash(&mut h);
-
-        let mut digest = vec![0u8; h.digest_size()];
-        h.digest(&mut digest)?;
-        Ok(digest)
+        key.hash(hash);
+        userid.hash(hash);
+        sig.hash(hash);
     }
 
     /// Returns the message digest of the user attribute binding over
     /// the specified primary key, user attribute, and signature.
     pub fn hash_user_attribute_binding<P>(
+        hash: &mut Context,
         sig: &signature::SignatureFields,
         key: &Key<P, key::PrimaryRole>,
         ua: &UserAttribute)
-        -> Result<Vec<u8>>
         where P: key::KeyParts,
     {
-        let mut h = sig.hash_algo().context()?;
-
-        key.hash(&mut h);
-        ua.hash(&mut h);
-        sig.hash(&mut h);
-
-        let mut digest = vec![0u8; h.digest_size()];
-        h.digest(&mut digest)?;
-        Ok(digest)
+        key.hash(hash);
+        ua.hash(hash);
+        sig.hash(hash);
     }
 }
 
@@ -503,10 +479,13 @@ mod test {
             let mut userid_sigs = 0;
             for (i, binding) in cert.userids().enumerate() {
                 for selfsig in binding.self_signatures() {
-                    let h = Signature::hash_userid_binding(
+                    let mut hash = selfsig.hash_algo().context().unwrap();
+                    Signature::hash_userid_binding(
+                        &mut hash,
                         selfsig,
                         cert.primary_key().key(),
-                        binding.userid()).unwrap();
+                        binding.userid());
+                    let h = hash.into_digest().unwrap();
                     if &h[..2] != selfsig.digest_prefix() {
                         eprintln!("{:?}: {:?} / {:?}",
                                   i, binding.userid(), selfsig);
@@ -520,10 +499,13 @@ mod test {
             for (i, a) in cert.user_attributes().enumerate()
             {
                 for selfsig in a.self_signatures() {
-                    let h = Signature::hash_user_attribute_binding(
+                    let mut hash = selfsig.hash_algo().context().unwrap();
+                    Signature::hash_user_attribute_binding(
+                        &mut hash,
                         selfsig,
                         cert.primary_key().key(),
-                        a.user_attribute()).unwrap();
+                        a.user_attribute());
+                    let h = hash.into_digest().unwrap();
                     if &h[..2] != selfsig.digest_prefix() {
                         eprintln!("{:?}: {:?} / {:?}",
                                   i, a.user_attribute(), selfsig);
@@ -536,10 +518,13 @@ mod test {
             let mut subkey_sigs = 0;
             for (i, binding) in cert.subkeys().enumerate() {
                 for selfsig in binding.self_signatures() {
-                    let h = Signature::hash_subkey_binding(
+                    let mut hash = selfsig.hash_algo().context().unwrap();
+                    Signature::hash_subkey_binding(
+                        &mut hash,
                         selfsig,
                         cert.primary_key().key(),
-                        binding.key()).unwrap();
+                        binding.key());
+                    let h = hash.into_digest().unwrap();
                     if &h[..2] != selfsig.digest_prefix() {
                         eprintln!("{:?}: {:?}", i, binding);
                         eprintln!("  Hash: {:?}", h);
diff --git a/openpgp/src/packet/signature.rs b/openpgp/src/packet/signature.rs
index 07ba1098..e0cf5d37 100644
--- a/openpgp/src/packet/signature.rs
+++ b/openpgp/src/packet/signature.rs
@@ -577,9 +577,9 @@ impl SignatureBuilder {
 
         self = self.pre_sign(signer)?;
 
-        let digest = Signature::hash_standalone(&self)?;
-
-        self.sign(signer, digest)
+        let mut hash = self.hash_algo().context()?;
+        Signature::hash_standalone(&mut hash, &self);
+        self.sign(signer, hash.into_digest()?)
     }
 
     /// Generates a Timestamp Signature.
@@ -690,9 +690,9 @@ impl SignatureBuilder {
 
         self = self.pre_sign(signer)?;
 
-        let digest = Signature::hash_timestamp(&self)?;
-
-        self.sign(signer, digest)
+        let mut hash = self.hash_algo().context()?;
+        Signature::hash_timestamp(&mut hash, &self);
+        self.sign(signer, hash.into_digest()?)
     }
 
     /// Generates a Direct Key Signature.
@@ -813,9 +813,9 @@ impl SignatureBuilder {
 
         self = self.pre_sign(signer)?;
 
-        let digest = Signature::hash_direct_key(&self, pk)?;
-
-        self.sign(signer, digest)
+        let mut hash = self.hash_algo().context()?;
+        Signature::hash_direct_key(&mut hash, &self, pk);
+        self.sign(signer, hash.into_digest()?)
     }
 
     /// Generates a User ID binding signature.
@@ -950,9 +950,9 @@ impl SignatureBuilder {
 
         self = self.pre_sign(signer)?;
 
-        let digest = Signature::hash_userid_binding(&self, key, userid)?;
-
-        self.sign(signer, digest)
+        let mut hash = self.hash_algo().context()?;
+        Signature::hash_userid_binding(&mut hash, &self, key, userid);
+        self.sign(signer, hash.into_digest()?)
     }
 
     /// Generates a subkey binding signature.
@@ -1070,9 +1070,9 @@ impl SignatureBuilder {
 
         self = self.pre_sign(signer)?;
 
-        let digest = Signature::hash_subkey_binding(&self, primary, subkey)?;
-
-        self.sign(signer, digest)
+        let mut hash = self.hash_algo().context()?;
+        Signature::hash_subkey_binding(&mut hash, &self, primary, subkey);
+        self.sign(signer, hash.into_digest()?)
     }
 
     /// Generates a primary key binding signature.
@@ -1218,10 +1218,9 @@ impl SignatureBuilder {
 
         self = self.pre_sign(subkey_signer)?;
 
-        let digest =
-            Signature::hash_primary_key_binding(&self, primary, subkey)?;
-
-        self.sign(subkey_signer, digest)
+        let mut hash = self.hash_algo().context()?;
+        Signature::hash_primary_key_binding(&mut hash, &self, primary, subkey);
+        self.sign(subkey_signer, hash.into_digest()?)
     }
 
 
@@ -1353,10 +1352,9 @@ impl SignatureBuilder {
 
         self = self.pre_sign(signer)?;
 
-        let digest =
-            Signature::hash_user_attribute_binding(&self, key, ua)?;
-
-        self.sign(signer, digest)
+        let mut hash = self.hash_algo().context()?;
+        Signature::hash_user_attribute_binding(&mut hash, &self, key, ua);
+        self.sign(signer, hash.into_digest()?)
     }
 
     /// Generates a signature.
@@ -2419,8 +2417,9 @@ impl Signature {
 
         // Standalone signatures are like binary-signatures over the
         // zero-sized string.
-        let digest = Signature::hash_standalone(self)?;
-        self.verify_digest(key, &digest[..])
+        let mut hash = self.hash_algo().context()?;
+        Signature::hash_standalone(&mut hash, &self);
+        self.verify_digest(key, &hash.into_digest()?[..])
     }
 
     /// Verifies the timestamp signature using `key`.
@@ -2446,8 +2445,9 @@ impl Signature {
 
         // Timestamp signatures are like binary-signatures over the
         // zero-sized string.
-        let digest = Signature::hash_timestamp(self)?;
-        self.verify_digest(key, &digest[..])
+        let mut hash = self.hash_algo().context()?;
+        Signature::hash_timestamp(&mut hash, &self);
+        self.verify_digest(key, &hash.into_digest()?[..])
     }
 
     /// Verifies the direct key signature.
@@ -2481,8 +2481,9 @@ impl Signature {
             return Err(Error::UnsupportedSignatureType(self.typ()).into());
         }
 
-        let hash = Signature::hash_direct_key(self, pk)?;
-        self.verify_digest(signer, &hash[..])
+        let mut hash = self.hash_algo().context()?;
+        Signature::hash_direct_key(&mut hash, &self, pk);
+        self.verify_digest(signer, &hash.into_digest()?[..])
     }
 
     /// Verifies the primary key revocation certificate.
@@ -2516,8 +2517,9 @@ impl Signature {
             return Err(Error::UnsupportedSignatureType(self.typ()).into());
         }
 
-        let hash = Signature::hash_direct_key(self, pk)?;
-        self.verify_digest(signer, &hash[..])
+        let mut hash = self.hash_algo().context()?;
+        Signature::hash_direct_key(&mut hash, &self, pk);
+        self.verify_digest(signer, &hash.into_digest()?[..])
     }
 
     /// Verifies the subkey binding.
@@ -2559,8 +2561,9 @@ impl Signature {
             return Err(Error::UnsupportedSignatureType(self.typ()).into());
         }
 
-        let hash = Signature::hash_subkey_binding(self, pk, subkey)?;
-        self.verify_digest(signer, &hash[..])?;
+        let mut hash = self.hash_algo().context()?;
+        Signature::hash_subkey_binding(&mut hash, &self, pk, subkey);
+        self.verify_digest(signer, &hash.into_digest()?[..])?;
 
         // The signature is good, but we may still need to verify the
         // back sig.
@@ -2622,8 +2625,9 @@ impl Signature {
             return Err(Error::UnsupportedSignatureType(self.typ()).into());
         }
 
-        let hash = Signature::hash_primary_key_binding(self, pk, subkey)?;
-        self.verify_digest(subkey, &hash[..])
+        let mut hash = self.hash_algo().context()?;
+        Signature::hash_primary_key_binding(&mut hash, &self, pk, subkey);
+        self.verify_digest(subkey, &hash.into_digest()?[..])
     }
 
     /// Verifies the subkey revocation.
@@ -2660,8 +2664,9 @@ impl Signature {
             return Err(Error::UnsupportedSignatureType(self.typ()).into());
         }
 
-        let hash = Signature::hash_subkey_binding(self, pk, subkey)?;
-        self.verify_digest(signer, &hash[..])
+        let mut hash = self.hash_algo().context()?;
+        Signature::hash_subkey_binding(&mut hash, &self, pk, subkey);
+        self.verify_digest(signer, &hash.into_digest()?[..])
     }
 
     /// Verifies the user id binding.
@@ -2699,8 +2704,9 @@ impl Signature {
             return Err(Error::UnsupportedSignatureType(self.typ()).into());
         }
 
-        let hash = Signature::hash_userid_binding(self, pk, userid)?;
-        self.verify_digest(signer, &hash[..])
+        let mut hash = self.hash_algo().context()?;
+        Signature::hash_userid_binding(&mut hash, &self, pk, userid);
+        self.verify_digest(signer, &hash.into_digest()?[..])
     }
 
     /// Verifies the user id revocation certificate.
@@ -2735,8 +2741,9 @@ impl Signature {
             return Err(Error::UnsupportedSignatureType(self.typ()).into());
         }
 
-        let hash = Signature::hash_userid_binding(self, pk, userid)?;
-        self.verify_digest(signer, &hash[..])
+        let mut hash = self.hash_algo().context()?;
+        Signature::hash_userid_binding(&mut hash, &self, pk, userid);
+        self.verify_digest(signer, &hash.into_digest()?[..])
     }
 
     /// Verifies the user attribute binding.
@@ -2774,8 +2781,9 @@ impl Signature {
             return Err(Error::UnsupportedSignatureType(self.typ()).into());
         }
 
-        let hash = Signature::hash_user_attribute_binding(self, pk, ua)?;
-        self.verify_digest(signer, &hash[..])
+        let mut hash = self.hash_algo().context()?;
+        Signature::hash_user_attribute_binding(&mut hash, &self, pk, ua);
+        self.verify_digest(signer, &hash.into_digest()?[..])
     }
 
     /// Verifies the user attribute revocation certificate.
@@ -2811,8 +2819,9 @@ impl Signature {
             return Err(Error::UnsupportedSignatureType(self.typ()).into());
         }
 
-        let hash = Signature::hash_user_attribute_binding(self, pk, ua)?;
-        self.verify_digest(signer, &hash[..])
+        let mut hash = self.hash_algo().context()?;
+        Signature::hash_user_attribute_binding(&mut hash, &self, pk, ua);
+        self.verify_digest(signer, &hash.into_digest()?[..])
     }
 
     /// Verifies a signature of a message.
@@ -3267,7 +3276,9 @@ mod test {
         let p = Packet::from_bytes(crate::tests::file(
             "contrib/gnupg/timestamp-signature-by-alice.asc")).unwrap();
         if let Packet::Signature(mut sig) = p {
-            let digest = Signature::hash_standalone(&sig).unwrap();
+            let mut hash = sig.hash_algo().context().unwrap();
+            Signature::hash_standalone(&mut hash, &sig);
+            let digest = hash.into_digest().unwrap();
             eprintln!("{}", crate::fmt::hex::encode(&digest));
             sig.verify_timestamp(alpha.primary_key().key()).unwrap();
         } else {