core/crypto/ed25519: Initial import

core/crypto/ed25519/ed25519.odin

@@ -0,0 +1,314 @@
+/*
+package ed25519 implements the Ed25519 EdDSA signature algorithm.
+
+See:
+- https://datatracker.ietf.org/doc/html/rfc8032
+- https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.186-5.pdf
+- https://eprint.iacr.org/2020/1244.pdf
+*/
+package ed25519
+
+import "core:crypto"
+import grp "core:crypto/_edwards25519"
+import "core:crypto/sha2"
+import "core:mem"
+
+// PRIVATE_KEY_SIZE is the byte-encoded private key size.
+PRIVATE_KEY_SIZE :: 32
+// PUBLIC_KEY_SIZE is the byte-encoded public key size.
+PUBLIC_KEY_SIZE :: 32
+// SIGNATURE_SIZE is the byte-encoded signature size.
+SIGNATURE_SIZE :: 64
+
+@(private)
+NONCE_SIZE :: 32
+
+// Private_Key is an Ed25519 private key.
+Private_Key :: struct {
+	// WARNING: All of the members are to be treated as internal (ie:
+	// the Private_Key structure is intended to be opaque).  There are
+	// subtle vulnerabilities that can be introduced if the internal
+	// values are allowed to be altered.
+	//
+	// See: https://github.com/MystenLabs/ed25519-unsafe-libs
+	_b:              [PRIVATE_KEY_SIZE]byte,
+	_s:              grp.Scalar,
+	_nonce:          [NONCE_SIZE]byte,
+	_pub_key:        Public_Key,
+	_is_initialized: bool,
+}
+
+// Public_Key is an Ed25519 public key.
+Public_Key :: struct {
+	// WARNING: All of the members are to be treated as internal (ie:
+	// the Public_Key structure is intended to be opaque).
+	_b:              [PUBLIC_KEY_SIZE]byte,
+	_neg_A:          grp.Group_Element,
+	_is_valid:       bool,
+	_is_initialized: bool,
+}
+
+// private_key_set_bytes decodes a byte-encoded private key, and returns
+// true iff the operation was successful.
+private_key_set_bytes :: proc(priv_key: ^Private_Key, b: []byte) -> bool {
+	if len(b) != PRIVATE_KEY_SIZE {
+		return false
+	}
+
+	// Derive the private key.
+	ctx: sha2.Context_512 = ---
+	h_bytes: [sha2.DIGEST_SIZE_512]byte = ---
+	sha2.init_512(&ctx)
+	sha2.update(&ctx, b)
+	sha2.final(&ctx, h_bytes[:])
+
+	copy(priv_key._b[:], b)
+	copy(priv_key._nonce[:], h_bytes[32:])
+	grp.sc_set_bytes_rfc8032(&priv_key._s, h_bytes[:32])
+
+	// Derive the corresponding public key.
+	A: grp.Group_Element = ---
+	grp.ge_scalarmult_basepoint(&A, &priv_key._s)
+	grp.ge_bytes(&A, priv_key._pub_key._b[:])
+	grp.ge_negate(&priv_key._pub_key._neg_A, &A)
+	priv_key._pub_key._is_valid = !grp.ge_is_small_order(&A)
+	priv_key._pub_key._is_initialized = true
+
+	priv_key._is_initialized = true
+
+	return true
+}
+
+// private_key_bytes sets dst to byte-encoding of priv_key.
+private_key_bytes :: proc(priv_key: ^Private_Key, dst: []byte) {
+	if !priv_key._is_initialized {
+		panic("crypto/ed25519: uninitialized private key")
+	}
+	if len(dst) != PRIVATE_KEY_SIZE {
+		panic("crypto/ed25519: invalid destination size")
+	}
+
+	copy(dst, priv_key._b[:])
+}
+
+// private_key_clear clears priv_key to the uninitialized state.
+private_key_clear :: proc "contextless" (priv_key: ^Private_Key) {
+	mem.zero_explicit(priv_key, size_of(Private_Key))
+}
+
+// sign writes the signature by priv_key over msg to sig.
+sign :: proc(priv_key: ^Private_Key, msg, sig: []byte) {
+	if !priv_key._is_initialized {
+		panic("crypto/ed25519: uninitialized private key")
+	}
+	if len(sig) != SIGNATURE_SIZE {
+		panic("crypto/ed25519: invalid destination size")
+	}
+
+	// 1. Compute the hash of the private key d, H(d) = (h_0, h_1, ..., h_2b-1)
+	// using SHA-512 for Ed25519.  H(d) may be precomputed.
+	//
+	// 2. Using the second half of the digest hdigest2 = hb || ... || h2b-1,
+	// define:
+	//
+	// 2.1 For Ed25519, r = SHA-512(hdigest2 || M); Interpret r as a
+	// 64-octet little-endian integer.
+	ctx: sha2.Context_512 = ---
+	digest_bytes: [sha2.DIGEST_SIZE_512]byte = ---
+	sha2.init_512(&ctx)
+	sha2.update(&ctx, priv_key._nonce[:])
+	sha2.update(&ctx, msg)
+	sha2.final(&ctx, digest_bytes[:])
+
+	r: grp.Scalar = ---
+	grp.sc_set_bytes_wide(&r, &digest_bytes)
+
+	// 3. Compute the point [r]G. The octet string R is the encoding of
+	// the point [r]G.
+	R: grp.Group_Element = ---
+	R_bytes := sig[:32]
+	grp.ge_scalarmult_basepoint(&R, &r)
+	grp.ge_bytes(&R, R_bytes)
+
+	// 4. Derive s from H(d) as in the key pair generation algorithm.
+	// Use octet strings R, Q, and M to define:
+	//
+	// 4.1 For Ed25519, digest = SHA-512(R || Q || M).
+	// Interpret digest as a little-endian integer.
+	sha2.init_512(&ctx)
+	sha2.update(&ctx, R_bytes)
+	sha2.update(&ctx, priv_key._pub_key._b[:]) // Q in NIST terminology.
+	sha2.update(&ctx, msg)
+	sha2.final(&ctx, digest_bytes[:])
+
+	sc: grp.Scalar = --- // `digest` in NIST terminology.
+	grp.sc_set_bytes_wide(&sc, &digest_bytes)
+
+	// 5. Compute S = (r + digest × s) mod n. The octet string S is the
+	// encoding of the resultant integer.
+	grp.sc_mul(&sc, &sc, &priv_key._s)
+	grp.sc_add(&sc, &sc, &r)
+
+	// 6. Form the signature as the concatenation of the octet strings
+	// R and S.
+	grp.sc_bytes(sig[32:], &sc)
+
+	grp.sc_clear(&r)
+}
+
+// public_key_set_bytes decodes a byte-encoded public key, and returns
+// true iff the operation was successful.
+public_key_set_bytes :: proc "contextless" (pub_key: ^Public_Key, b: []byte) -> bool {
+	if len(b) != PUBLIC_KEY_SIZE {
+		return false
+	}
+
+	A: grp.Group_Element = ---
+	if !grp.ge_set_bytes(&A, b) {
+		return false
+	}
+
+	copy(pub_key._b[:], b)
+	grp.ge_negate(&pub_key._neg_A, &A)
+	pub_key._is_valid = !grp.ge_is_small_order(&A)
+	pub_key._is_initialized = true
+
+	return true
+}
+
+// public_key_set_priv sets pub_key to the public component of priv_key.
+public_key_set_priv :: proc(pub_key: ^Public_Key, priv_key: ^Private_Key) {
+	if !priv_key._is_initialized {
+		panic("crypto/ed25519: uninitialized public key")
+	}
+
+	src := &priv_key._pub_key
+	copy(pub_key._b[:], src._b[:])
+	grp.ge_set(&pub_key._neg_A, &src._neg_A)
+	pub_key._is_valid = src._is_valid
+	pub_key._is_initialized = src._is_initialized
+}
+
+// public_key_bytes sets dst to byte-encoding of pub_key.
+public_key_bytes :: proc(pub_key: ^Public_Key, dst: []byte) {
+	if !pub_key._is_initialized {
+		panic("crypto/ed25519: uninitialized public key")
+	}
+	if len(dst) != PUBLIC_KEY_SIZE {
+		panic("crypto/ed25519: invalid destination size")
+	}
+
+	copy(dst, pub_key._b[:])
+}
+
+// public_key_equal returns true iff pub_key is equal to other.
+public_key_equal :: proc(pub_key, other: ^Public_Key) -> bool {
+	if !pub_key._is_initialized || !other._is_initialized {
+		panic("crypto/ed25519: uninitialized public key")
+	}
+
+	return crypto.compare_constant_time(pub_key._b[:], other._b[:]) == 1
+}
+
+// verify returns true iff sig is a valid signature by pub_key over msg.
+//
+// The optional `allow_small_order_A` parameter will make this
+// implementation strictly compatible with FIPS 186-5, at the expense of
+// SBS-security.  Doing so is NOT recommended, and the disallowed
+// public keys all have a known discrete-log.
+verify :: proc(pub_key: ^Public_Key, msg, sig: []byte, allow_small_order_A := false) -> bool {
+	switch {
+	case !pub_key._is_initialized:
+		return false
+	case len(sig) != SIGNATURE_SIZE:
+		return false
+	}
+
+	// TLDR: Just use ristretto255.
+	//
+	// While there are two "standards" for EdDSA, existing implementations
+	// diverge (sometimes dramatically).  This implementation opts for
+	// "Algorithm 2" from "Taming the Many EdDSAs", which provides the
+	// strongest notion of security (SUF-CMA + SBS).
+	//
+	// The relevant properties are:
+	// - Reject non-canonical S.
+	// - Reject non-canonical A/R.
+	// - Reject small-order A (Extra non-standard check).
+	// - Cofactored verification equation.
+	//
+	// There are 19 possible non-canonical group element encodings of
+	// which:
+	// - 2 are small order
+	// - 10 are mixed order
+	// - 7 are not on the curve
+	//
+	// While historical implementations have been lax about enforcing
+	// that A/R are canonically encoded, that behavior is mandated by
+	// both the RFC and FIPS specification.  No valid key generation
+	// or sign implementation will ever produce non-canonically encoded
+	// public keys or signatures.
+	//
+	// There are 8 small-order group elements, 1 which is in the
+	// prime-order sub-group, and thus the probability that a properly
+	// generated A is small-order is cryptographically insignificant.
+	//
+	// While both the RFC and FIPS standard allow for either the
+	// cofactored or non-cofactored equation.  It is possible to
+	// artificially produce signatures that are valid for the former
+	// but not the latter.  This will NEVER occur with a valid sign
+	// implementation.  The choice of the latter is to be compatible
+	// with ABGLSV-Pornin, batch verification, and FROST (among other
+	// things).
+
+	s_bytes, r_bytes := sig[32:], sig[:32]
+
+	// 1. Reject the signature if S is not in the range [0, L).
+	s: grp.Scalar = ---
+	if !grp.sc_set_bytes(&s, s_bytes) {
+		return false
+	}
+
+	// 2. Reject the signature if the public key A is one of 8 small
+	// order points.
+	//
+	// As this check is optional and not part of the standard, we allow
+	// the caller to bypass it if desired.  Disabling the check makes
+	// the scheme NOT SBS-secure.
+	if !pub_key._is_valid && !allow_small_order_A {
+		return false
+	}
+
+	// 3. Reject the signature if A or R are non-canonical.
+	//
+	// Note: All initialized public keys are guaranteed to be canonical.
+	neg_R: grp.Group_Element = ---
+	if !grp.ge_set_bytes(&neg_R, r_bytes) {
+		return false
+	}
+	grp.ge_negate(&neg_R, &neg_R)
+
+	// 4. Compute the hash SHA512(R||A||M) and reduce it mod L to get a
+	// scalar h.
+	ctx: sha2.Context_512 = ---
+	h_bytes: [sha2.DIGEST_SIZE_512]byte = ---
+	sha2.init_512(&ctx)
+	sha2.update(&ctx, r_bytes)
+	sha2.update(&ctx, pub_key._b[:])
+	sha2.update(&ctx, msg)
+	sha2.final(&ctx, h_bytes[:])
+
+	h: grp.Scalar = ---
+	grp.sc_set_bytes_wide(&h, &h_bytes)
+
+	// 5. Accept if 8(s * G) - 8R - 8(h * A) = 0
+	//
+	// > first compute V = SB − R − hA and then accept if V is one of
+	// > 8 small order points (or alternatively compute 8V with 3
+	// > doublings and check against the neutral element)
+	V: grp.Group_Element = ---
+	grp.ge_double_scalarmult_basepoint_vartime(&V, &h, &pub_key._neg_A, &s)
+	grp.ge_add(&V, &V, &neg_R)
+
+	return grp.ge_is_small_order(&V)
+}

examples/all/all_main.odin

@@ -29,6 +29,7 @@ import blake2s          "core:crypto/blake2s"
 import chacha20         "core:crypto/chacha20"
 import chacha20poly1305 "core:crypto/chacha20poly1305"
 import crypto_hash      "core:crypto/hash"
+import ed25519          "core:crypto/ed25519"
 import hkdf             "core:crypto/hkdf"
 import hmac             "core:crypto/hmac"
 import kmac             "core:crypto/kmac"
@@ -152,6 +153,7 @@ _ :: blake2b
 _ :: blake2s
 _ :: chacha20
 _ :: chacha20poly1305
+_ :: ed25519
 _ :: hmac
 _ :: hkdf
 _ :: kmac