add endpoint to retrieve public key

CHANGELOG.md

@@ -41,6 +41,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 signer sub module
 * [#31](https://github.com/babylonlabs-io/covenant-emulator/pull/31/) Bump docker workflow
 version, fix some Dockerfile issue
+* [#36](https://github.com/babylonlabs-io/covenant-emulator/pull/36) Add public key
+endpoint to the remote signer
 
 ## v0.8.0
 

covenant-signer/itest/e2etest.go → covenant-signer/itest/e2e_test.go

@@ -129,6 +129,17 @@ func buildDataToSign(t *testing.T, covnenantPublicKey *btcec.PublicKey) signerap
 	}
 }
 
+func TestGetPublicKey(t *testing.T) {
+	tm := StartManager(t, 100)
+
+	pubKey, err := signerservice.GetPublicKey(context.Background(), tm.SigningServerUrl(), 10*time.Second)
+	require.NoError(t, err)
+	require.NotNil(t, pubKey)
+
+	pubKeyBytes := pubKey.SerializeCompressed()
+	require.Equal(t, hex.EncodeToString(pubKeyBytes), hex.EncodeToString(tm.covenantPrivKey.PubKey().SerializeCompressed()))
+}
+
 func TestSigningTransactions(t *testing.T) {
 	tm := StartManager(t, 100)
 

covenant-signer/signerapp/signer.go

@@ -44,7 +44,6 @@ func (s *SignerApp) SignTransactions(
 	ctx context.Context,
 	req *ParsedSigningRequest,
 ) (*ParsedSigningResponse, error) {
-
 	privKey, err := s.pkr.PrivKey(ctx)
 
 	defer func() {
@@ -77,7 +76,16 @@ func (s *SignerApp) SignTransactions(
 		UnbondingSig:              unbondingSig,
 		SlashUnbondingAdaptorSigs: slashUnbondingSigs,
 	}, nil
+}
+
+func (s *SignerApp) PubKey(ctx context.Context) (*btcec.PublicKey, error) {
+	privKey, err := s.pkr.PrivKey(ctx)
+	if err != nil {
+		return nil, err
+	}
+	defer privKey.Zero()
 
+	return privKey.PubKey(), nil
 }
 
 func slashUnbondSig(

covenant-signer/signerservice/client.go

@@ -3,6 +3,7 @@ package signerservice
 import (
 	"bytes"
 	"context"
+	"encoding/hex"
 	"encoding/json"
 	"fmt"
 	"io"
@@ -12,6 +13,7 @@ import (
 	"github.com/babylonlabs-io/covenant-emulator/covenant-signer/signerapp"
 	"github.com/babylonlabs-io/covenant-emulator/covenant-signer/signerservice/handlers"
 	"github.com/babylonlabs-io/covenant-emulator/covenant-signer/signerservice/types"
+	"github.com/btcsuite/btcd/btcec/v2"
 )
 
 const (
@@ -79,3 +81,46 @@ func RequestCovenantSignaure(
 
 	return types.ToParsedSigningResponse(&response.Data)
 }
+
+func GetPublicKey(ctx context.Context, signerUrl string, timeout time.Duration) (*btcec.PublicKey, error) {
+	route := fmt.Sprintf("%s/v1/public-key", signerUrl)
+
+	httpRequest, err := http.NewRequestWithContext(ctx, "GET", route, nil)
+
+	if err != nil {
+		return nil, err
+	}
+
+	client := http.Client{Timeout: timeout}
+	res, err := client.Do(httpRequest)
+
+	if err != nil {
+		return nil, err
+	}
+
+	defer res.Body.Close()
+
+	maxSizeReader := http.MaxBytesReader(nil, res.Body, maxResponseSize)
+
+	resBody, err := io.ReadAll(maxSizeReader)
+
+	if err != nil {
+		return nil, err
+	}
+
+	if res.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("public key request failed. status code: %d, message: %s", res.StatusCode, string(resBody))
+	}
+
+	var response handlers.PublicResponse[types.GetPublicKeyResponse]
+	if err := json.Unmarshal(resBody, &response); err != nil {
+		return nil, err
+	}
+
+	pubKey, err := hex.DecodeString(response.Data.PublicKey)
+	if err != nil {
+		return nil, err
+	}
+
+	return btcec.ParsePubKey(pubKey)
+}

covenant-signer/signerservice/handlers/signtransactions.go

@@ -1,6 +1,7 @@
 package handlers
 
 import (
+	"encoding/hex"
 	"encoding/json"
 	"net/http"
 
@@ -40,3 +41,16 @@ func (h *Handler) SignTransactions(request *http.Request) (*Result, *types.Error
 
 	return NewResult(resp), nil
 }
+
+func (h *Handler) GetPublicKey(request *http.Request) (*Result, *types.Error) {
+	pubKey, err := h.s.PubKey(request.Context())
+	if err != nil {
+		return nil, types.NewErrorWithMsg(http.StatusInternalServerError, types.InternalServiceError, err.Error())
+	}
+
+	resp := &types.GetPublicKeyResponse{
+		PublicKey: hex.EncodeToString(pubKey.SerializeCompressed()),
+	}
+
+	return NewResult(resp), nil
+}

covenant-signer/signerservice/server.go

@@ -23,6 +23,7 @@ type SigningServer struct {
 func (a *SigningServer) SetupRoutes(r *chi.Mux) {
 	handler := a.handler
 	r.Post("/v1/sign-transactions", registerHandler(handler.SignTransactions))
+	r.Get("/v1/public-key", registerHandler(handler.GetPublicKey))
 }
 
 func New(

covenant-signer/signerservice/types/publickey.go

@@ -0,0 +1,6 @@
+package types
+
+type GetPublicKeyResponse struct {
+	// hex encoded 33 byte public key
+	PublicKey string `json:"public_key_hex"`
+}