diff --git a/Cargo.toml b/Cargo.toml index 4dd0e4e..3342366 100644 --- a/Cargo.toml +++ b/Cargo.toml @@ -20,7 +20,7 @@ exclude = [ travis-ci = { repository = "dalek-cryptography/x25519-dalek", branch = "master"} [dependencies.curve25519-dalek] -version = "^1.0.0-pre.1" +version = "1" default-features = false [dependencies.rand_core] diff --git a/benches/x25519.rs b/benches/x25519.rs index 9a8238b..e1e5818 100644 --- a/benches/x25519.rs +++ b/benches/x25519.rs @@ -32,7 +32,7 @@ fn bench_diffie_hellman(c: &mut Criterion) { c.bench_function("diffie_hellman", move |b| { b.iter_with_setup( || EphemeralSecret::new(&mut csprng), - |alice_secret| EphemeralSecret::diffie_hellman(alice_secret, &bob_public), + |alice_secret| alice_secret.diffie_hellman(&bob_public), ) }); } diff --git a/src/x25519.rs b/src/x25519.rs index ec3630f..31b3f71 100644 --- a/src/x25519.rs +++ b/src/x25519.rs @@ -22,7 +22,6 @@ use rand_core::RngCore; use rand_core::CryptoRng; /// A DH ephemeral public key. -#[repr(C)] pub struct EphemeralPublic(pub (crate) MontgomeryPoint); impl From<[u8; 32]> for EphemeralPublic { @@ -34,8 +33,6 @@ impl From<[u8; 32]> for EphemeralPublic { } /// A DH ephemeral secret key. -#[repr(C)] -#[derive(Default)] // we derive Default in order to use the clear() method in Drop pub struct EphemeralSecret(pub (crate) Scalar); /// Overwrite ephemeral secret key material with null bytes when it goes out of scope. @@ -46,13 +43,11 @@ impl Drop for EphemeralSecret { } impl EphemeralSecret { - /// The diffie_hellman function performs scalar multipication on a montegomery point. - /// This is the implementation for the x25519 function, as specified in RFC7748. + /// Utility function to make it easier to call `x25519()` with + /// an ephemeral secret key and montegomery point as input and + /// a shared secret as the output. pub fn diffie_hellman(self, their_public: &EphemeralPublic) -> SharedSecret { - let k: Scalar = clamp_scalar(self.0.as_bytes()); - let point: MontgomeryPoint = MontgomeryPoint(*their_public.0.as_bytes()); - - SharedSecret(k * point) + SharedSecret(self.0 * their_public.0) } /// Generate an x25519 `EphemeralSecret` key. @@ -63,7 +58,7 @@ impl EphemeralSecret { csprng.fill_bytes(&mut bytes); - EphemeralSecret(clamp_scalar(&bytes)) + EphemeralSecret(clamp_scalar(bytes)) } } @@ -78,7 +73,6 @@ impl<'a> From<&'a EphemeralSecret> for EphemeralPublic { } /// A DH SharedSecret -#[repr(C)] pub struct SharedSecret(pub (crate) MontgomeryPoint); /// Overwrite shared secret material with null bytes when it goes out of scope. @@ -105,7 +99,7 @@ impl SharedSecret { /// # Returns /// /// A `Scalar`. -fn clamp_scalar(scalar: &[u8; 32]) -> Scalar { +fn clamp_scalar(scalar: [u8; 32]) -> Scalar { let mut s: [u8; 32] = scalar.clone(); s[0] &= 248; @@ -115,58 +109,63 @@ fn clamp_scalar(scalar: &[u8; 32]) -> Scalar { Scalar::from_bits(s) } +/// The x25519 function, as specified in RFC7748. +pub fn x25519(k: [u8; 32], u: [u8; 32]) -> [u8; 32] { + (clamp_scalar(k) * MontgomeryPoint(u)).to_bytes() +} + #[cfg(test)] mod test { use super::*; - fn do_rfc7748_ladder_test1(input_scalar: &Scalar, - input_point: &MontgomeryPoint, - expected: &[u8; 32]) { - let result = EphemeralSecret::diffie_hellman(EphemeralSecret(*input_scalar), &EphemeralPublic(*input_point)); + fn do_rfc7748_ladder_test1(input_scalar: [u8; 32], + input_point: [u8; 32], + expected: [u8; 32]) { + let result = x25519(input_scalar, input_point); - assert_eq!(result.0, MontgomeryPoint(*expected)); + assert_eq!(result, expected); } #[test] fn rfc7748_ladder_test1_vectorset1() { - let input_scalar: Scalar = Scalar::from_bits([ + let input_scalar: [u8; 32] = [ 0xa5, 0x46, 0xe3, 0x6b, 0xf0, 0x52, 0x7c, 0x9d, 0x3b, 0x16, 0x15, 0x4b, 0x82, 0x46, 0x5e, 0xdd, 0x62, 0x14, 0x4c, 0x0a, 0xc1, 0xfc, 0x5a, 0x18, - 0x50, 0x6a, 0x22, 0x44, 0xba, 0x44, 0x9a, 0xc4, ]); - let input_point: MontgomeryPoint = MontgomeryPoint([ + 0x50, 0x6a, 0x22, 0x44, 0xba, 0x44, 0x9a, 0xc4, ]; + let input_point: [u8; 32] = [ 0xe6, 0xdb, 0x68, 0x67, 0x58, 0x30, 0x30, 0xdb, 0x35, 0x94, 0xc1, 0xa4, 0x24, 0xb1, 0x5f, 0x7c, 0x72, 0x66, 0x24, 0xec, 0x26, 0xb3, 0x35, 0x3b, - 0x10, 0xa9, 0x03, 0xa6, 0xd0, 0xab, 0x1c, 0x4c, ]); + 0x10, 0xa9, 0x03, 0xa6, 0xd0, 0xab, 0x1c, 0x4c, ]; let expected: [u8; 32] = [ 0xc3, 0xda, 0x55, 0x37, 0x9d, 0xe9, 0xc6, 0x90, 0x8e, 0x94, 0xea, 0x4d, 0xf2, 0x8d, 0x08, 0x4f, 0x32, 0xec, 0xcf, 0x03, 0x49, 0x1c, 0x71, 0xf7, 0x54, 0xb4, 0x07, 0x55, 0x77, 0xa2, 0x85, 0x52, ]; - do_rfc7748_ladder_test1(&input_scalar, &input_point, &expected); + do_rfc7748_ladder_test1(input_scalar, input_point, expected); } #[test] fn rfc7748_ladder_test1_vectorset2() { - let input_scalar: Scalar = Scalar::from_bits([ + let input_scalar: [u8; 32] = [ 0x4b, 0x66, 0xe9, 0xd4, 0xd1, 0xb4, 0x67, 0x3c, 0x5a, 0xd2, 0x26, 0x91, 0x95, 0x7d, 0x6a, 0xf5, 0xc1, 0x1b, 0x64, 0x21, 0xe0, 0xea, 0x01, 0xd4, - 0x2c, 0xa4, 0x16, 0x9e, 0x79, 0x18, 0xba, 0x0d, ]); - let input_point: MontgomeryPoint = MontgomeryPoint([ + 0x2c, 0xa4, 0x16, 0x9e, 0x79, 0x18, 0xba, 0x0d, ]; + let input_point: [u8; 32] = [ 0xe5, 0x21, 0x0f, 0x12, 0x78, 0x68, 0x11, 0xd3, 0xf4, 0xb7, 0x95, 0x9d, 0x05, 0x38, 0xae, 0x2c, 0x31, 0xdb, 0xe7, 0x10, 0x6f, 0xc0, 0x3c, 0x3e, - 0xfc, 0x4c, 0xd5, 0x49, 0xc7, 0x15, 0xa4, 0x93, ]); + 0xfc, 0x4c, 0xd5, 0x49, 0xc7, 0x15, 0xa4, 0x93, ]; let expected: [u8; 32] = [ 0x95, 0xcb, 0xde, 0x94, 0x76, 0xe8, 0x90, 0x7d, 0x7a, 0xad, 0xe4, 0x5c, 0xb4, 0xb8, 0x73, 0xf8, 0x8b, 0x59, 0x5a, 0x68, 0x79, 0x9f, 0xa1, 0x52, 0xe6, 0xf8, 0xf7, 0x64, 0x7a, 0xac, 0x79, 0x57, ]; - do_rfc7748_ladder_test1(&input_scalar, &input_point, &expected); + do_rfc7748_ladder_test1(input_scalar, input_point, expected); } #[test] @@ -174,14 +173,14 @@ mod test { fn rfc7748_ladder_test2() { use curve25519_dalek::constants::X25519_BASEPOINT; - let mut k: Scalar = Scalar::from_bits(X25519_BASEPOINT.0); - let mut u: MontgomeryPoint = X25519_BASEPOINT; - let mut result: SharedSecret; + let mut k: [u8; 32] = X25519_BASEPOINT.0; + let mut u: [u8; 32] = X25519_BASEPOINT.0; + let mut result: [u8; 32]; macro_rules! do_iterations { ($n:expr) => ( for _ in 0..$n { - result = EphemeralSecret::diffie_hellman(EphemeralSecret(k), &EphemeralPublic(u)); + result = x25519(k, u); // OBVIOUS THING THAT I'M GOING TO NOTE ANYWAY BECAUSE I'VE // SEEN PEOPLE DO THIS WITH GOLANG'S STDLIB AND YOU SURE AS // HELL SHOULDN'T DO HORRIBLY STUPID THINGS LIKE THIS WITH @@ -190,8 +189,8 @@ mod test { // NEVER EVER TREAT SCALARS AS POINTS AND/OR VICE VERSA. // // ↓↓ DON'T DO THIS ↓↓ - u = MontgomeryPoint(k.as_bytes().clone()); - k = Scalar::from_bits(result.0.to_bytes()); + u = k.clone(); + k = result; } ) } @@ -204,19 +203,19 @@ mod test { // 7c3911e0ab2586fd864497297e575e6f3bc601c0883c30df5f4dd2d24f665424 do_iterations!(1); - assert_eq!(k.as_bytes(), &[ 0x42, 0x2c, 0x8e, 0x7a, 0x62, 0x27, 0xd7, 0xbc, - 0xa1, 0x35, 0x0b, 0x3e, 0x2b, 0xb7, 0x27, 0x9f, - 0x78, 0x97, 0xb8, 0x7b, 0xb6, 0x85, 0x4b, 0x78, - 0x3c, 0x60, 0xe8, 0x03, 0x11, 0xae, 0x30, 0x79, ]); + assert_eq!(k, [ 0x42, 0x2c, 0x8e, 0x7a, 0x62, 0x27, 0xd7, 0xbc, + 0xa1, 0x35, 0x0b, 0x3e, 0x2b, 0xb7, 0x27, 0x9f, + 0x78, 0x97, 0xb8, 0x7b, 0xb6, 0x85, 0x4b, 0x78, + 0x3c, 0x60, 0xe8, 0x03, 0x11, 0xae, 0x30, 0x79, ]); do_iterations!(999); - assert_eq!(k.as_bytes(), &[ 0x68, 0x4c, 0xf5, 0x9b, 0xa8, 0x33, 0x09, 0x55, - 0x28, 0x00, 0xef, 0x56, 0x6f, 0x2f, 0x4d, 0x3c, - 0x1c, 0x38, 0x87, 0xc4, 0x93, 0x60, 0xe3, 0x87, - 0x5f, 0x2e, 0xb9, 0x4d, 0x99, 0x53, 0x2c, 0x51, ]); + assert_eq!(k, [ 0x68, 0x4c, 0xf5, 0x9b, 0xa8, 0x33, 0x09, 0x55, + 0x28, 0x00, 0xef, 0x56, 0x6f, 0x2f, 0x4d, 0x3c, + 0x1c, 0x38, 0x87, 0xc4, 0x93, 0x60, 0xe3, 0x87, + 0x5f, 0x2e, 0xb9, 0x4d, 0x99, 0x53, 0x2c, 0x51, ]); do_iterations!(999_000); - assert_eq!(k.as_bytes(), &[ 0x7c, 0x39, 0x11, 0xe0, 0xab, 0x25, 0x86, 0xfd, - 0x86, 0x44, 0x97, 0x29, 0x7e, 0x57, 0x5e, 0x6f, - 0x3b, 0xc6, 0x01, 0xc0, 0x88, 0x3c, 0x30, 0xdf, - 0x5f, 0x4d, 0xd2, 0xd2, 0x4f, 0x66, 0x54, 0x24, ]); + assert_eq!(k, [ 0x7c, 0x39, 0x11, 0xe0, 0xab, 0x25, 0x86, 0xfd, + 0x86, 0x44, 0x97, 0x29, 0x7e, 0x57, 0x5e, 0x6f, + 0x3b, 0xc6, 0x01, 0xc0, 0x88, 0x3c, 0x30, 0xdf, + 0x5f, 0x4d, 0xd2, 0xd2, 0x4f, 0x66, 0x54, 0x24, ]); } }