From c1b8a4815f6046308660fe9418ff9d87e9d3717b Mon Sep 17 00:00:00 2001
From: Leonard Lyubich <leonard@nspcc.ru>
Date: Wed, 13 Jan 2021 15:49:46 +0300
Subject: [PATCH] [#306] private: Implement server of gRPC private node service

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
---
 pkg/services/private/server/healthcheck.go | 35 ++++++++++++++
 pkg/services/private/server/server.go      | 53 +++++++++++++++++++++
 pkg/services/private/server/sign.go        | 54 ++++++++++++++++++++++
 3 files changed, 142 insertions(+)
 create mode 100644 pkg/services/private/server/healthcheck.go
 create mode 100644 pkg/services/private/server/server.go
 create mode 100644 pkg/services/private/server/sign.go

diff --git a/pkg/services/private/server/healthcheck.go b/pkg/services/private/server/healthcheck.go
new file mode 100644
index 0000000000..daf41aa55e
--- /dev/null
+++ b/pkg/services/private/server/healthcheck.go
@@ -0,0 +1,35 @@
+package private
+
+import (
+	"context"
+
+	"github.com/nspcc-dev/neofs-node/pkg/services/private"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+)
+
+// HealthCheck returns health status of the local node.
+//
+// If request is unsigned or signed by disallowed key, permission error returns.
+func (s *Server) HealthCheck(_ context.Context, req *private.HealthCheckRequest) (*private.HealthCheckResponse, error) {
+	// verify request
+	if err := s.isValidRequest(req); err != nil {
+		return nil, status.Error(codes.PermissionDenied, err.Error())
+	}
+
+	// create and fill response
+	resp := new(private.HealthCheckResponse)
+
+	body := new(private.HealthCheckResponse_Body)
+	resp.SetBody(body)
+
+	// FIXME: calculate the status
+	body.SetStatus(private.HealthStatus_ONLINE)
+
+	// sign the response
+	if err := SignMessage(s.key, resp); err != nil {
+		return nil, status.Error(codes.Internal, err.Error())
+	}
+
+	return resp, nil
+}
diff --git a/pkg/services/private/server/server.go b/pkg/services/private/server/server.go
new file mode 100644
index 0000000000..0272267225
--- /dev/null
+++ b/pkg/services/private/server/server.go
@@ -0,0 +1,53 @@
+package private
+
+import (
+	"crypto/ecdsa"
+)
+
+// Server is an entity that serves
+// Private service on storage node.
+type Server struct {
+	*cfg
+}
+
+// Option of the Server's constructor.
+type Option func(*cfg)
+
+type cfg struct {
+	key *ecdsa.PrivateKey
+
+	allowedKeys [][]byte
+}
+
+func defaultCfg() *cfg {
+	return &cfg{}
+}
+
+// New creates, initializes and returns new Server instance.
+func New(opts ...Option) *Server {
+	c := defaultCfg()
+
+	for _, opt := range opts {
+		opt(c)
+	}
+
+	return &Server{
+		cfg: c,
+	}
+}
+
+// WithKey returns option to set private key
+// used for signing responses.
+func WithKey(key *ecdsa.PrivateKey) Option {
+	return func(c *cfg) {
+		c.key = key
+	}
+}
+
+// WithAllowedKeys returns option to add list of public
+// keys that have rights to use private service.
+func WithAllowedKeys(keys [][]byte) Option {
+	return func(c *cfg) {
+		c.allowedKeys = append(c.allowedKeys, keys...)
+	}
+}
diff --git a/pkg/services/private/server/sign.go b/pkg/services/private/server/sign.go
new file mode 100644
index 0000000000..56c0ebdd35
--- /dev/null
+++ b/pkg/services/private/server/sign.go
@@ -0,0 +1,54 @@
+package private
+
+import (
+	"bytes"
+	"crypto/ecdsa"
+	"errors"
+
+	"github.com/nspcc-dev/neofs-api-go/util/signature"
+	"github.com/nspcc-dev/neofs-node/pkg/services/private"
+)
+
+// SignedMessage is an interface of Private service message.
+type SignedMessage interface {
+	signature.DataSource
+	GetSignature() *private.Signature
+	SetSignature(*private.Signature)
+}
+
+var errDisallowedKey = errors.New("key is not in the allowed list")
+
+func (s *Server) isValidRequest(req SignedMessage) error {
+	var (
+		sign    = req.GetSignature()
+		key     = sign.GetKey()
+		allowed = false
+	)
+
+	// check if key is allowed
+	for i := range s.allowedKeys {
+		if allowed = bytes.Equal(s.allowedKeys[i], key); allowed {
+			break
+		}
+	}
+
+	if !allowed {
+		return errDisallowedKey
+	}
+
+	// verify signature
+	return signature.VerifyDataWithSource(req, func() ([]byte, []byte) {
+		return key, sign.GetSign()
+	})
+}
+
+// SignMessage signs Private service message with private key.
+func SignMessage(key *ecdsa.PrivateKey, msg SignedMessage) error {
+	return signature.SignDataWithHandler(key, msg, func(key []byte, sig []byte) {
+		s := new(private.Signature)
+		s.SetKey(key)
+		s.SetSign(sig)
+
+		msg.SetSignature(s)
+	})
+}