Zig 0.17.0-dev (Split by item)

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KeyShare

Client.KeyShare

const KeyShare = struct

File

lib/std/crypto/tls/Client.zig:1358

Code

const KeyShare = struct {
    ml_kem768_kp: crypto.kem.ml_kem.MLKem768.KeyPair,
    secp256r1_kp: crypto.sign.ecdsa.EcdsaP256Sha256.KeyPair,
    secp384r1_kp: crypto.sign.ecdsa.EcdsaP384Sha384.KeyPair,
    x25519_kp: crypto.dh.X25519.KeyPair,
    sk_buf: [sk_max_len]u8,
    sk_len: std.math.IntFittingRange(0, sk_max_len),

    const sk_max_len = @max(
        crypto.dh.X25519.shared_length + crypto.kem.ml_kem.MLKem768.shared_length,
        crypto.ecc.P256.scalar.encoded_length,
        crypto.ecc.P384.scalar.encoded_length,
        crypto.dh.X25519.shared_length,
    );

    fn init(seed: *const [176]u8) error{IdentityElement}!KeyShare {
        return .{
            .ml_kem768_kp = try .generateDeterministic(seed[0..64].*),
            .secp256r1_kp = try .generateDeterministic(seed[64..96].*),
            .secp384r1_kp = try .generateDeterministic(seed[96..144].*),
            .x25519_kp = try .generateDeterministic(seed[144..176].*),
            .sk_buf = undefined,
            .sk_len = 0,
        };
    }

    fn exchange(
        ks: *KeyShare,
        named_group: tls.NamedGroup,
        server_pub_key: []const u8,
    ) error{ TlsIllegalParameter, TlsDecryptFailure }!void {
        switch (named_group) {
            .x25519_ml_kem768 => {
                const hksl = crypto.kem.ml_kem.MLKem768.ciphertext_length;
                const xksl = hksl + crypto.dh.X25519.public_length;
                if (server_pub_key.len != xksl) return error.TlsIllegalParameter;

                const hsk = ks.ml_kem768_kp.secret_key.decaps(server_pub_key[0..hksl]) catch
                    return error.TlsDecryptFailure;
                const xsk = crypto.dh.X25519.scalarmult(ks.x25519_kp.secret_key, server_pub_key[hksl..xksl].*) catch
                    return error.TlsDecryptFailure;
                @memcpy(ks.sk_buf[0..hsk.len], &hsk);
                @memcpy(ks.sk_buf[hsk.len..][0..xsk.len], &xsk);
                ks.sk_len = hsk.len + xsk.len;
            },
            .secp256r1 => {
                const PublicKey = crypto.sign.ecdsa.EcdsaP256Sha256.PublicKey;
                const pk = PublicKey.fromSec1(server_pub_key) catch return error.TlsDecryptFailure;
                const mul = pk.p.mulPublic(ks.secp256r1_kp.secret_key.bytes, .big) catch
                    return error.TlsDecryptFailure;
                const sk = mul.affineCoordinates().x.toBytes(.big);
                @memcpy(ks.sk_buf[0..sk.len], &sk);
                ks.sk_len = sk.len;
            },
            .secp384r1 => {
                const PublicKey = crypto.sign.ecdsa.EcdsaP384Sha384.PublicKey;
                const pk = PublicKey.fromSec1(server_pub_key) catch return error.TlsDecryptFailure;
                const mul = pk.p.mulPublic(ks.secp384r1_kp.secret_key.bytes, .big) catch
                    return error.TlsDecryptFailure;
                const sk = mul.affineCoordinates().x.toBytes(.big);
                @memcpy(ks.sk_buf[0..sk.len], &sk);
                ks.sk_len = sk.len;
            },
            .x25519 => {
                const ksl = crypto.dh.X25519.public_length;
                if (server_pub_key.len != ksl) return error.TlsIllegalParameter;
                const sk = crypto.dh.X25519.scalarmult(ks.x25519_kp.secret_key, server_pub_key[0..ksl].*) catch
                    return error.TlsDecryptFailure;
                @memcpy(ks.sk_buf[0..sk.len], &sk);
                ks.sk_len = sk.len;
            },
            else => return error.TlsIllegalParameter,
        }
    }

    fn getSharedSecret(ks: *const KeyShare) ?[]const u8 {
        return if (ks.sk_len > 0) ks.sk_buf[0..ks.sk_len] else null;
    }
}