Use symmetric crypto from rust-bitcoin primitives to prep for 0.7

ohttp/Cargo.toml

@@ -17,16 +17,14 @@ external-sqlite = []
 gecko = ["nss", "mozbuild"]
 nss = ["bindgen", "regex-mess"]
 regex-mess = ["regex", "regex-automata", "regex-syntax"]
-rust-hpke = ["rand", "aead", "aes-gcm", "chacha20poly1305", "hkdf", "sha2", "bitcoin-hpke"]
+rust-hpke = ["rand", "chacha20-poly1305", "bitcoin_hashes", "bitcoin-hpke"]
 server = []
 
 [dependencies]
-aead = {version = "0.4", optional = true, features = ["std"]}
-aes-gcm = {version = "0.9", optional = true}
 byteorder = "1.4"
-chacha20poly1305 = {version = "0.8", optional = true}
+chacha20-poly1305 = {version = "0.2", optional = true, default-features = false}
 hex = "0.4"
-hkdf = {version = "0.11", optional = true}
+bitcoin_hashes = {version = "0.14", optional = true, default-features = false}
 bitcoin-hpke = {version = "0.20.0", optional = true, default-features = false, features = ["std", "secp"]}
 lazy_static = "1.4"
 log = {version = "0.4", default-features = false}
@@ -36,7 +34,6 @@ rand = {version = "0.8", optional = true}
 regex = {version = "~1.9", optional = true}
 regex-automata = {version = "~0.3", optional = true}
 regex-syntax = {version = "~0.7", optional = true}
-sha2 = {version = "0.9", optional = true}
 thiserror = "1"
 
 [build-dependencies]

ohttp/src/err.rs

@@ -4,7 +4,7 @@ use thiserror::Error;
 pub enum Error {
     #[cfg(feature = "rust-hpke")]
     #[error("a problem occurred with the AEAD")]
-    Aead(#[from] aead::Error),
+    Aead,
     #[cfg(feature = "nss")]
     #[error("a problem occurred during cryptographic processing: {0}")]
     Crypto(#[from] crate::nss::Error),

ohttp/src/lib.rs

@@ -395,7 +395,7 @@ mod test {
         match res.unwrap_err() {
             Error::Truncated => {}
             #[cfg(feature = "rust-hpke")]
-            Error::Aead(_) => {}
+            Error::Aead => {}
             #[cfg(feature = "nss")]
             Error::Crypto(_) => {}
             Error::Io(e) => assert_eq!(e.kind(), ErrorKind::UnexpectedEof),

ohttp/src/rh/aead.rs

@@ -1,16 +1,20 @@
 #![allow(dead_code)] // TODO: remove
 
-use super::SymKey;
-use crate::{err::Res, hpke::Aead as AeadId};
-use aead::{AeadMut, Key, NewAead, Nonce, Payload};
-use aes_gcm::{Aes128Gcm, Aes256Gcm};
-use chacha20poly1305::ChaCha20Poly1305;
 use std::convert::TryFrom;
 
+use chacha20_poly1305::{ChaCha20Poly1305, Key, Nonce};
+
+use super::SymKey;
+use crate::{
+    err::{Error, Res},
+    hpke::Aead as AeadId,
+};
+
 /// All the nonces are the same length.  Exploit that.
 pub const NONCE_LEN: usize = 12;
 const COUNTER_LEN: usize = 8;
 const TAG_LEN: usize = 16;
+const KEY_LEN: usize = 32;
 
 type SequenceNumber = u64;
 
@@ -20,67 +24,29 @@ pub enum Mode {
     Decrypt,
 }
 
-enum AeadEngine {
-    Aes128Gcm(Box<Aes128Gcm>),
-    Aes256Gcm(Box<Aes256Gcm>),
-    ChaCha20Poly1305(Box<ChaCha20Poly1305>),
-}
-
-// Dispatch functions; this just shows how janky that this sort of abstraction can be.
-// If this grows too much, this is fairly clearly responsive to using a macro.
-impl AeadEngine {
-    fn encrypt(&mut self, nonce: &[u8], pt: Payload) -> Res<Vec<u8>> {
-        let tag = match self {
-            Self::Aes128Gcm(e) => e.encrypt(Nonce::<Aes128Gcm>::from_slice(nonce), pt)?,
-            Self::Aes256Gcm(e) => e.encrypt(Nonce::<Aes256Gcm>::from_slice(nonce), pt)?,
-            Self::ChaCha20Poly1305(e) => {
-                e.encrypt(Nonce::<ChaCha20Poly1305>::from_slice(nonce), pt)?
-            }
-        };
-        Ok(tag)
-    }
-    fn decrypt(&mut self, nonce: &[u8], pt: Payload) -> Res<Vec<u8>> {
-        let tag = match self {
-            Self::Aes128Gcm(e) => e.decrypt(Nonce::<Aes128Gcm>::from_slice(nonce), pt)?,
-            Self::Aes256Gcm(e) => e.decrypt(Nonce::<Aes256Gcm>::from_slice(nonce), pt)?,
-            Self::ChaCha20Poly1305(e) => {
-                e.decrypt(Nonce::<ChaCha20Poly1305>::from_slice(nonce), pt)?
-            }
-        };
-        Ok(tag)
-    }
-}
-
-/// A switch-hitting AEAD that uses a selected primitive.
+/// ChaCha20-Poly1305, the only AEAD this crate implements. `bitcoin-hpke` dropped
+/// the AES-GCM schemes in 0.13.0, so the GCM suites were never usable end to end.
 pub struct Aead {
     mode: Mode,
-    engine: AeadEngine,
+    key: [u8; KEY_LEN],
     nonce_base: [u8; NONCE_LEN],
     seq: SequenceNumber,
 }
 
 impl Aead {
-    #[allow(clippy::unnecessary_wraps)]
     pub fn new(
         mode: Mode,
         algorithm: AeadId,
         key: &SymKey,
         nonce_base: [u8; NONCE_LEN],
     ) -> Res<Self> {
-        let aead = match algorithm {
-            AeadId::Aes128Gcm => AeadEngine::Aes128Gcm(Box::new(Aes128Gcm::new(
-                Key::<Aes128Gcm>::from_slice(key.as_ref()),
-            ))),
-            AeadId::Aes256Gcm => AeadEngine::Aes256Gcm(Box::new(Aes256Gcm::new(
-                Key::<Aes256Gcm>::from_slice(key.as_ref()),
-            ))),
-            AeadId::ChaCha20Poly1305 => AeadEngine::ChaCha20Poly1305(Box::new(
-                ChaCha20Poly1305::new(Key::<ChaCha20Poly1305>::from_slice(key.as_ref())),
-            )),
-        };
+        if algorithm != AeadId::ChaCha20Poly1305 {
+            return Err(Error::Unsupported);
+        }
+        let key = <[u8; KEY_LEN]>::try_from(key.as_ref()).map_err(|_| Error::Unsupported)?;
         Ok(Self {
             mode,
-            engine: aead,
+            key,
             nonce_base,
             seq: 0,
         })
@@ -92,27 +58,41 @@ impl Aead {
         Ok(SymKey::from(k))
     }
 
-    fn nonce(&self, seq: SequenceNumber) -> Vec<u8> {
-        let mut nonce = Vec::from(self.nonce_base);
+    fn nonce(&self, seq: SequenceNumber) -> [u8; NONCE_LEN] {
+        let mut nonce = self.nonce_base;
         for (i, n) in nonce.iter_mut().rev().take(COUNTER_LEN).enumerate() {
             *n ^= u8::try_from((seq >> (8 * i)) & 0xff).unwrap();
         }
         nonce
     }
 
+    fn cipher(&self, nonce: [u8; NONCE_LEN]) -> ChaCha20Poly1305 {
+        ChaCha20Poly1305::new(Key::new(self.key), Nonce::new(nonce))
+    }
+
+    #[allow(clippy::unnecessary_wraps)] // Res is part of the interface shared with the NSS backend
     pub fn seal(&mut self, aad: &[u8], pt: &[u8]) -> Res<Vec<u8>> {
         assert_eq!(self.mode, Mode::Encrypt);
-        // A copy for the nonce generator to write into.  But we don't use the value.
         let nonce = self.nonce(self.seq);
         self.seq += 1;
-        let ct = self.engine.encrypt(&nonce, Payload { msg: pt, aad })?;
+        let mut ct = pt.to_vec();
+        let tag = self.cipher(nonce).encrypt(&mut ct, Some(aad));
+        ct.extend_from_slice(&tag);
         Ok(ct)
     }
 
     pub fn open(&mut self, aad: &[u8], seq: SequenceNumber, ct: &[u8]) -> Res<Vec<u8>> {
         assert_eq!(self.mode, Mode::Decrypt);
+        if ct.len() < TAG_LEN {
+            return Err(Error::Truncated);
+        }
+        let (body, tag) = ct.split_at(ct.len() - TAG_LEN);
+        let tag = <[u8; TAG_LEN]>::try_from(tag).map_err(|_| Error::Truncated)?;
         let nonce = self.nonce(seq);
-        let pt = self.engine.decrypt(&nonce, Payload { msg: ct, aad })?;
+        let mut pt = body.to_vec();
+        self.cipher(nonce)
+            .decrypt(&mut pt, tag, Some(aad))
+            .map_err(|_| Error::Aead)?;
         Ok(pt)
     }
 }
@@ -161,73 +141,8 @@ mod test {
         assert_eq!(&plaintext[..], pt);
     }
 
-    /// This tests the AEAD in QUIC in combination with the HKDF code.
-    /// This is an AEAD-only example.
-    #[test]
-    fn quic_retry() {
-        const KEY: &[u8] = &[
-            0xbe, 0x0c, 0x69, 0x0b, 0x9f, 0x66, 0x57, 0x5a, 0x1d, 0x76, 0x6b, 0x54, 0xe3, 0x68,
-            0xc8, 0x4e,
-        ];
-        const NONCE: &[u8; NONCE_LEN] = &[
-            0x46, 0x15, 0x99, 0xd3, 0x5d, 0x63, 0x2b, 0xf2, 0x23, 0x98, 0x25, 0xbb,
-        ];
-        const AAD: &[u8] = &[
-            0x08, 0x83, 0x94, 0xc8, 0xf0, 0x3e, 0x51, 0x57, 0x08, 0xff, 0x00, 0x00, 0x00, 0x01,
-            0x00, 0x08, 0xf0, 0x67, 0xa5, 0x50, 0x2a, 0x42, 0x62, 0xb5, 0x74, 0x6f, 0x6b, 0x65,
-            0x6e,
-        ];
-        const CT: &[u8] = &[
-            0x04, 0xa2, 0x65, 0xba, 0x2e, 0xff, 0x4d, 0x82, 0x90, 0x58, 0xfb, 0x3f, 0x0f, 0x24,
-            0x96, 0xba,
-        ];
-        check0(AeadId::Aes128Gcm, KEY, NONCE, AAD, &[], CT);
-    }
-
-    #[test]
-    fn quic_server_initial() {
-        const ALG: AeadId = AeadId::Aes128Gcm;
-        const KEY: &[u8] = &[
-            0xcf, 0x3a, 0x53, 0x31, 0x65, 0x3c, 0x36, 0x4c, 0x88, 0xf0, 0xf3, 0x79, 0xb6, 0x06,
-            0x7e, 0x37,
-        ];
-        const NONCE_BASE: &[u8; NONCE_LEN] = &[
-            0x0a, 0xc1, 0x49, 0x3c, 0xa1, 0x90, 0x58, 0x53, 0xb0, 0xbb, 0xa0, 0x3e,
-        ];
-        // Note that this integrates the sequence number of 1 from the example,
-        // otherwise we can't use a sequence number of 0 to encrypt.
-        const NONCE: &[u8; NONCE_LEN] = &[
-            0x0a, 0xc1, 0x49, 0x3c, 0xa1, 0x90, 0x58, 0x53, 0xb0, 0xbb, 0xa0, 0x3f,
-        ];
-        const AAD: &[u8] = &[
-            0xc1, 0x00, 0x00, 0x00, 0x01, 0x00, 0x08, 0xf0, 0x67, 0xa5, 0x50, 0x2a, 0x42, 0x62,
-            0xb5, 0x00, 0x40, 0x75, 0x00, 0x01,
-        ];
-        const PT: &[u8] = &[
-            0x02, 0x00, 0x00, 0x00, 0x00, 0x06, 0x00, 0x40, 0x5a, 0x02, 0x00, 0x00, 0x56, 0x03,
-            0x03, 0xee, 0xfc, 0xe7, 0xf7, 0xb3, 0x7b, 0xa1, 0xd1, 0x63, 0x2e, 0x96, 0x67, 0x78,
-            0x25, 0xdd, 0xf7, 0x39, 0x88, 0xcf, 0xc7, 0x98, 0x25, 0xdf, 0x56, 0x6d, 0xc5, 0x43,
-            0x0b, 0x9a, 0x04, 0x5a, 0x12, 0x00, 0x13, 0x01, 0x00, 0x00, 0x2e, 0x00, 0x33, 0x00,
-            0x24, 0x00, 0x1d, 0x00, 0x20, 0x9d, 0x3c, 0x94, 0x0d, 0x89, 0x69, 0x0b, 0x84, 0xd0,
-            0x8a, 0x60, 0x99, 0x3c, 0x14, 0x4e, 0xca, 0x68, 0x4d, 0x10, 0x81, 0x28, 0x7c, 0x83,
-            0x4d, 0x53, 0x11, 0xbc, 0xf3, 0x2b, 0xb9, 0xda, 0x1a, 0x00, 0x2b, 0x00, 0x02, 0x03,
-            0x04,
-        ];
-        const CT: &[u8] = &[
-            0x5a, 0x48, 0x2c, 0xd0, 0x99, 0x1c, 0xd2, 0x5b, 0x0a, 0xac, 0x40, 0x6a, 0x58, 0x16,
-            0xb6, 0x39, 0x41, 0x00, 0xf3, 0x7a, 0x1c, 0x69, 0x79, 0x75, 0x54, 0x78, 0x0b, 0xb3,
-            0x8c, 0xc5, 0xa9, 0x9f, 0x5e, 0xde, 0x4c, 0xf7, 0x3c, 0x3e, 0xc2, 0x49, 0x3a, 0x18,
-            0x39, 0xb3, 0xdb, 0xcb, 0xa3, 0xf6, 0xea, 0x46, 0xc5, 0xb7, 0x68, 0x4d, 0xf3, 0x54,
-            0x8e, 0x7d, 0xde, 0xb9, 0xc3, 0xbf, 0x9c, 0x73, 0xcc, 0x3f, 0x3b, 0xde, 0xd7, 0x4b,
-            0x56, 0x2b, 0xfb, 0x19, 0xfb, 0x84, 0x02, 0x2f, 0x8e, 0xf4, 0xcd, 0xd9, 0x37, 0x95,
-            0xd7, 0x7d, 0x06, 0xed, 0xbb, 0x7a, 0xaf, 0x2f, 0x58, 0x89, 0x18, 0x50, 0xab, 0xbd,
-            0xca, 0x3d, 0x20, 0x39, 0x8c, 0x27, 0x64, 0x56, 0xcb, 0xc4, 0x21, 0x58, 0x40, 0x7d,
-            0xd0, 0x74, 0xee,
-        ];
-        check0(ALG, KEY, NONCE, AAD, PT, CT);
-        decrypt(ALG, KEY, NONCE_BASE, 1, AAD, PT, CT);
-    }
-
+    /// The QUIC ChaCha20-Poly1305 sample (RFC 9001 A.5). Pins the AEAD to a published
+    /// vector so a cipher swap cannot silently change the wire format.
     #[test]
     fn quic_chacha() {
         const ALG: AeadId = AeadId::ChaCha20Poly1305;
@@ -254,4 +169,14 @@ mod test {
         // Now use the real nonce and sequence number from the example.
         decrypt(ALG, KEY, NONCE_BASE, 654_360_564, AAD, PT, CT);
     }
+
+    /// The AES-GCM suites were never implementable here, so construction must fail
+    /// cleanly rather than half-work.
+    #[test]
+    fn aes_gcm_unsupported() {
+        init();
+        let k = Aead::import_key(AeadId::ChaCha20Poly1305, &[0; 32]).unwrap();
+        assert!(Aead::new(Mode::Encrypt, AeadId::Aes128Gcm, &k, [0; NONCE_LEN]).is_err());
+        assert!(Aead::new(Mode::Encrypt, AeadId::Aes256Gcm, &k, [0; NONCE_LEN]).is_err());
+    }
 }

ohttp/src/rh/hkdf.rs

@@ -5,9 +5,57 @@ use crate::{
     err::{Error, Res},
     hpke::{Aead, Kdf},
 };
-use hkdf::Hkdf as HkdfImpl;
+use bitcoin_hashes::{Hash, HashEngine, Hmac, HmacEngine, sha256, sha384, sha512};
 use log::trace;
-use sha2::{Sha256, Sha384, Sha512};
+
+/// One HMAC-Hash invocation over `data` keyed with `key`.
+fn hmac<T: Hash>(key: &[u8], data: &[u8]) -> Vec<u8>
+where
+    <T as Hash>::Bytes: AsRef<[u8]>,
+{
+    let mut engine = HmacEngine::<T>::new(key);
+    engine.input(data);
+    Hmac::<T>::from_engine(engine)
+        .as_byte_array()
+        .as_ref()
+        .to_vec()
+}
+
+/// RFC 5869 HKDF-Extract. An empty salt and a HashLen-of-zeros salt are equivalent
+/// here, since HMAC zero-pads the key to the block size either way.
+fn extract_with<T: Hash>(salt: &[u8], ikm: &[u8]) -> Vec<u8>
+where
+    <T as Hash>::Bytes: AsRef<[u8]>,
+{
+    hmac::<T>(salt, ikm)
+}
+
+/// RFC 5869 HKDF-Expand. Errors if `len` would need more than 255 blocks.
+fn expand_with<T: Hash>(prk: &[u8], info: &[u8], len: usize) -> Res<Vec<u8>>
+where
+    <T as Hash>::Bytes: AsRef<[u8]>,
+{
+    let mut okm: Vec<u8> = Vec::with_capacity(len);
+    let mut block: Vec<u8> = Vec::new();
+    let mut counter: u8 = 1;
+    while okm.len() < len {
+        let mut engine = HmacEngine::<T>::new(prk);
+        engine.input(&block);
+        engine.input(info);
+        engine.input(&[counter]);
+        block = Hmac::<T>::from_engine(engine)
+            .as_byte_array()
+            .as_ref()
+            .to_vec();
+        okm.extend_from_slice(&block);
+        if okm.len() >= len {
+            break;
+        }
+        counter = counter.checked_add(1).ok_or(Error::Internal)?;
+    }
+    okm.truncate(len);
+    Ok(okm)
+}
 
 #[derive(Clone, Copy)]
 pub enum KeyMechanism {
@@ -48,17 +96,14 @@ impl Hkdf {
 
     #[allow(clippy::unnecessary_wraps)]
     pub fn extract(&self, salt: &[u8], ikm: &SymKey) -> Res<SymKey> {
-        let prk = match self {
-            Self::Sha256 => {
-                SymKey::from(HkdfImpl::<Sha256>::extract(Some(salt), &ikm.0).0.as_slice())
-            }
-            Self::Sha384 => {
-                SymKey::from(HkdfImpl::<Sha384>::extract(Some(salt), &ikm.0).0.as_slice())
+        let prk = SymKey::from(
+            match self {
+                Self::Sha256 => extract_with::<sha256::Hash>(salt, &ikm.0),
+                Self::Sha384 => extract_with::<sha384::Hash>(salt, &ikm.0),
+                Self::Sha512 => extract_with::<sha512::Hash>(salt, &ikm.0),
             }
-            Self::Sha512 => {
-                SymKey::from(HkdfImpl::<Sha512>::extract(Some(salt), &ikm.0).0.as_slice())
-            }
-        };
+            .as_slice(),
+        );
         trace!(
             "HKDF extract: salt={} ikm={:?} prk={:?}",
             hex::encode(salt),
@@ -80,21 +125,11 @@ impl Hkdf {
     }
 
     pub fn expand_data(&self, prk: &SymKey, info: &[u8], len: usize) -> Res<Vec<u8>> {
-        let mut okm = vec![0; len];
-        match self {
-            Self::Sha256 => {
-                let h = HkdfImpl::<Sha256>::from_prk(&prk.0).map_err(|_| Error::Internal)?;
-                h.expand(info, &mut okm).map_err(|_| Error::Internal)?;
-            }
-            Self::Sha384 => {
-                let h = HkdfImpl::<Sha384>::from_prk(&prk.0).map_err(|_| Error::Internal)?;
-                h.expand(info, &mut okm).map_err(|_| Error::Internal)?;
-            }
-            Self::Sha512 => {
-                let h = HkdfImpl::<Sha512>::from_prk(&prk.0).map_err(|_| Error::Internal)?;
-                h.expand(info, &mut okm).map_err(|_| Error::Internal)?;
-            }
-        }
+        let okm = match self {
+            Self::Sha256 => expand_with::<sha256::Hash>(&prk.0, info, len)?,
+            Self::Sha384 => expand_with::<sha384::Hash>(&prk.0, info, len)?,
+            Self::Sha512 => expand_with::<sha512::Hash>(&prk.0, info, len)?,
+        };
         trace!(
             "HKDF expand_data: prk={:?} info={} len={} okm={:?}",
             prk,