Return parsable error codes instead of just a string.

Also
- Check if VSP is closed before /payfee

docs/api.md

@@ -4,8 +4,16 @@
 
 - Success responses use HTTP status 200 and a JSON encoded body.
 
-- Error responses use either HTTP status 500 or 400, and a JSON encoded error
-  in the body, e.g. `{"error":"Description"}`.
+- Error responses use HTTP status 500 to indicate a server error or 400 to
+  indiciate a client error, and will include a JSON body describing the error.
+  For example:
+
+  ```json
+  {"code": 9, "message":"invalid vote choices"}
+  ```
+
+  A full list of error codes can be looked up in
+  [webapi/errors.go](../webapi/errors.go)
 
 - Requests which reference specific tickets need to be properly signed as
   described in [two-way-accountability.md](./two-way-accountability.md).

webapi/errors.go

@@ -0,0 +1,84 @@
+package webapi
+
+import "net/http"
+
+type apiError int
+
+const (
+	errBadRequest apiError = iota
+	errInternalError
+	errVspClosed
+	errFeeAlreadyReceived
+	errInvalidFeeTx
+	errFeeTooSmall
+	errUnknownTicket
+	errTicketCannotVote
+	errFeeExpired
+	errInvalidVoteChoices
+	errBadSignature
+	errInvalidPrivKey
+)
+
+// httpStatus maps application error codes to HTTP status codes.
+func (e apiError) httpStatus() int {
+	switch e {
+	case errBadRequest:
+		return http.StatusBadRequest
+	case errInternalError:
+		return http.StatusInternalServerError
+	case errVspClosed:
+		return http.StatusBadRequest
+	case errFeeAlreadyReceived:
+		return http.StatusBadRequest
+	case errInvalidFeeTx:
+		return http.StatusBadRequest
+	case errFeeTooSmall:
+		return http.StatusBadRequest
+	case errUnknownTicket:
+		return http.StatusBadRequest
+	case errTicketCannotVote:
+		return http.StatusBadRequest
+	case errFeeExpired:
+		return http.StatusBadRequest
+	case errInvalidVoteChoices:
+		return http.StatusBadRequest
+	case errBadSignature:
+		return http.StatusBadRequest
+	case errInvalidPrivKey:
+		return http.StatusBadRequest
+	default:
+		return http.StatusInternalServerError
+	}
+}
+
+// defaultMessage returns a descriptive error string for a given error code.
+func (e apiError) defaultMessage() string {
+	switch e {
+	case errBadRequest:
+		return "bad request"
+	case errInternalError:
+		return "internal error"
+	case errVspClosed:
+		return "vsp is closed"
+	case errFeeAlreadyReceived:
+		return "fee tx already received"
+	case errInvalidFeeTx:
+		return "invalid fee transaction"
+	case errFeeTooSmall:
+		return "fee too small"
+	case errUnknownTicket:
+		return "unknown ticket"
+	case errTicketCannotVote:
+		return "ticket not eligible to vote"
+	case errFeeExpired:
+		return "fee has expired"
+	case errInvalidVoteChoices:
+		return "invalid vote choices"
+	case errBadSignature:
+		return "bad request signature"
+	case errInvalidPrivKey:
+		return "invalid private key"
+	default:
+		return "unknown error"
+	}
+}

webapi/getfeeaddress.go

@@ -1,7 +1,6 @@
 package webapi
 
 import (
-	"net/http"
 	"sync"
 	"time"
 
@@ -70,14 +69,14 @@ func feeAddress(c *gin.Context) {
 	dcrdClient := c.MustGet("DcrdClient").(*rpc.DcrdRPC)
 
 	if cfg.VspClosed {
-		sendErrorResponse("pool is not accepting new tickets", http.StatusBadRequest, c)
+		sendError(errVspClosed, c)
 		return
 	}
 
 	var feeAddressRequest FeeAddressRequest
 	if err := binding.JSON.BindBody(rawRequest, &feeAddressRequest); err != nil {
 		log.Warnf("Bad feeaddress request from %s: %v", c.ClientIP(), err)
-		sendErrorResponse(err.Error(), http.StatusBadRequest, c)
+		sendErrorWithMsg(err.Error(), errBadRequest, c)
 		return
 	}
 
@@ -86,7 +85,7 @@ func feeAddress(c *gin.Context) {
 	// Respond early if we already have the fee tx for this ticket.
 	if ticket.FeeTxHex != "" {
 		log.Warnf("Fee tx already received from %s: ticketHash=%s", c.ClientIP(), ticket.Hash)
-		sendErrorResponse("fee tx already received", http.StatusBadRequest, c)
+		sendError(errFeeAlreadyReceived, c)
 		return
 	}
 
@@ -94,7 +93,7 @@ func feeAddress(c *gin.Context) {
 	rawTicket, err := dcrdClient.GetRawTransaction(ticketHash)
 	if err != nil {
 		log.Errorf("Could not retrieve tx %s for %s: %v", ticketHash, c.ClientIP(), err)
-		sendErrorResponse(err.Error(), http.StatusInternalServerError, c)
+		sendError(errInternalError, c)
 		return
 	}
 
@@ -102,12 +101,12 @@ func feeAddress(c *gin.Context) {
 	canVote, err := dcrdClient.CanTicketVote(rawTicket, ticketHash, cfg.NetParams)
 	if err != nil {
 		log.Errorf("canTicketVote error: %v", err)
-		sendErrorResponse("error validating ticket", http.StatusInternalServerError, c)
+		sendError(errInternalError, c)
 		return
 	}
 	if !canVote {
 		log.Warnf("Unvotable ticket %s from %s", ticketHash, c.ClientIP())
-		sendErrorResponse("ticket not eligible to vote", http.StatusBadRequest, c)
+		sendError(errTicketCannotVote, c)
 		return
 	}
 
@@ -120,7 +119,7 @@ func feeAddress(c *gin.Context) {
 			newFee, err := getCurrentFee(dcrdClient)
 			if err != nil {
 				log.Errorf("getCurrentFee error: %v", err)
-				sendErrorResponse("fee error", http.StatusInternalServerError, c)
+				sendError(errInternalError, c)
 				return
 			}
 			ticket.FeeExpiration = now.Add(feeAddressExpiration).Unix()
@@ -129,7 +128,7 @@ func feeAddress(c *gin.Context) {
 			err = db.UpdateTicket(ticket)
 			if err != nil {
 				log.Errorf("UpdateTicket error: %v", err)
-				sendErrorResponse("database error", http.StatusInternalServerError, c)
+				sendError(errInternalError, c)
 				return
 			}
 			log.Debugf("Expired fee updated for ticket: newFeeAmt=%f, ticketHash=%s",
@@ -152,7 +151,7 @@ func feeAddress(c *gin.Context) {
 	fee, err := getCurrentFee(dcrdClient)
 	if err != nil {
 		log.Errorf("getCurrentFee error: %v", err)
-		sendErrorResponse("fee error", http.StatusInternalServerError, c)
+		sendError(errInternalError, c)
 		return
 	}
 
@@ -180,7 +179,7 @@ func feeAddress(c *gin.Context) {
 	err = db.InsertNewTicket(dbTicket)
 	if err != nil {
 		log.Errorf("InsertTicket error: %v", err)
-		sendErrorResponse("database error", http.StatusInternalServerError, c)
+		sendError(errInternalError, c)
 		return
 	}
 

webapi/middleware.go

@@ -54,7 +54,7 @@ func withDcrdClient() gin.HandlerFunc {
 		client, err := dcrd.Client(c, cfg.NetParams)
 		if err != nil {
 			log.Error(err)
-			sendErrorResponse("dcrd RPC error", http.StatusInternalServerError, c)
+			sendError(errInternalError, c)
 			return
 		}
 
@@ -69,7 +69,7 @@ func withWalletClients() gin.HandlerFunc {
 		clients, failedConnections := wallets.Clients(c, cfg.NetParams)
 		if len(clients) == 0 {
 			log.Error("Could not connect to any wallets")
-			sendErrorResponse("dcrwallet RPC error", http.StatusInternalServerError, c)
+			sendError(errInternalError, c)
 			return
 		}
 		if failedConnections > 0 {
@@ -93,7 +93,7 @@ func vspAuth() gin.HandlerFunc {
 		reqBytes, err := c.GetRawData()
 		if err != nil {
 			log.Warnf("Error reading request from %s: %v", c.ClientIP(), err)
-			sendErrorResponse(err.Error(), http.StatusBadRequest, c)
+			sendErrorWithMsg(err.Error(), errBadRequest, c)
 			return
 		}
 
@@ -104,7 +104,7 @@ func vspAuth() gin.HandlerFunc {
 		var request ticketHashRequest
 		if err := binding.JSON.BindBody(reqBytes, &request); err != nil {
 			log.Warnf("Bad request from %s: %v", c.ClientIP(), err)
-			sendErrorResponse(err.Error(), http.StatusBadRequest, c)
+			sendErrorWithMsg(err.Error(), errBadRequest, c)
 			return
 		}
 		hash := request.TicketHash
@@ -113,7 +113,7 @@ func vspAuth() gin.HandlerFunc {
 		ticket, ticketFound, err := db.GetTicketByHash(hash)
 		if err != nil {
 			log.Errorf("GetTicketByHash error: %v", err)
-			sendErrorResponse("database error", http.StatusInternalServerError, c)
+			sendError(errInternalError, c)
 			return
 		}
 
@@ -127,7 +127,7 @@ func vspAuth() gin.HandlerFunc {
 			commitmentAddress, err = dcrdClient.GetTicketCommitmentAddress(hash, cfg.NetParams)
 			if err != nil {
 				log.Errorf("GetTicketCommitmentAddress error: %v", err)
-				sendErrorResponse(err.Error(), http.StatusInternalServerError, c)
+				sendError(errInternalError, c)
 				return
 			}
 		}
@@ -136,7 +136,7 @@ func vspAuth() gin.HandlerFunc {
 		err = validateSignature(reqBytes, commitmentAddress, c)
 		if err != nil {
 			log.Warnf("Bad signature from %s: %v", c.ClientIP(), err)
-			sendErrorResponse("bad signature", http.StatusBadRequest, c)
+			sendError(errBadSignature, c)
 			return
 		}
 

webapi/payfee.go

@@ -2,7 +2,6 @@ package webapi
 
 import (
 	"encoding/hex"
-	"net/http"
 	"time"
 
 	"github.com/decred/dcrd/dcrec"
@@ -24,23 +23,28 @@ func payFee(c *gin.Context) {
 	knownTicket := c.MustGet("KnownTicket").(bool)
 	dcrdClient := c.MustGet("DcrdClient").(*rpc.DcrdRPC)
 
+	if cfg.VspClosed {
+		sendError(errVspClosed, c)
+		return
+	}
+
 	if !knownTicket {
-		log.Warnf("Invalid ticket from %s", c.ClientIP())
-		sendErrorResponse("invalid ticket", http.StatusBadRequest, c)
+		log.Warnf("Unknown ticket from %s", c.ClientIP())
+		sendError(errUnknownTicket, c)
 		return
 	}
 
 	var payFeeRequest PayFeeRequest
 	if err := binding.JSON.BindBody(rawRequest, &payFeeRequest); err != nil {
 		log.Warnf("Bad payfee request from %s: %v", c.ClientIP(), err)
-		sendErrorResponse(err.Error(), http.StatusBadRequest, c)
+		sendErrorWithMsg(err.Error(), errBadRequest, c)
 		return
 	}
 
 	// Respond early if we already have the fee tx for this ticket.
 	if ticket.FeeTxHex != "" {
 		log.Warnf("Fee tx already received from %s: ticketHash=%s", c.ClientIP(), ticket.Hash)
-		sendErrorResponse("fee tx already received", http.StatusBadRequest, c)
+		sendError(errFeeAlreadyReceived, c)
 		return
 	}
 
@@ -48,7 +52,7 @@ func payFee(c *gin.Context) {
 	rawTicket, err := dcrdClient.GetRawTransaction(ticket.Hash)
 	if err != nil {
 		log.Errorf("Could not retrieve tx %s for %s: %v", ticket.Hash, c.ClientIP(), err)
-		sendErrorResponse(err.Error(), http.StatusInternalServerError, c)
+		sendError(errInternalError, c)
 		return
 	}
 
@@ -56,19 +60,19 @@ func payFee(c *gin.Context) {
 	canVote, err := dcrdClient.CanTicketVote(rawTicket, ticket.Hash, cfg.NetParams)
 	if err != nil {
 		log.Errorf("canTicketVote error: %v", err)
-		sendErrorResponse("error validating ticket", http.StatusInternalServerError, c)
+		sendError(errInternalError, c)
 		return
 	}
 	if !canVote {
 		log.Warnf("Unvotable ticket %s from %s", ticket.Hash, c.ClientIP())
-		sendErrorResponse("ticket not eligible to vote", http.StatusBadRequest, c)
+		sendError(errTicketCannotVote, c)
 		return
 	}
 
 	// Respond early if the fee for this ticket is expired.
 	if ticket.FeeExpired() {
 		log.Warnf("Expired payfee request from %s", c.ClientIP())
-		sendErrorResponse("fee has expired", http.StatusBadRequest, c)
+		sendError(errFeeExpired, c)
 		return
 	}
 
@@ -77,7 +81,7 @@ func payFee(c *gin.Context) {
 	votingWIF, err := dcrutil.DecodeWIF(votingKey, cfg.NetParams.PrivateKeyID)
 	if err != nil {
 		log.Warnf("Failed to decode WIF: %v", err)
-		sendErrorResponse("error decoding WIF", http.StatusBadRequest, c)
+		sendError(errInvalidPrivKey, c)
 		return
 	}
 
@@ -86,7 +90,7 @@ func payFee(c *gin.Context) {
 	err = isValidVoteChoices(cfg.NetParams, currentVoteVersion(cfg.NetParams), voteChoices)
 	if err != nil {
 		log.Warnf("Invalid votechoices from %s: %v", c.ClientIP(), err)
-		sendErrorResponse(err.Error(), http.StatusBadRequest, c)
+		sendErrorWithMsg(err.Error(), errInvalidVoteChoices, c)
 		return
 	}
 
@@ -94,14 +98,14 @@ func payFee(c *gin.Context) {
 	feeTxBytes, err := hex.DecodeString(payFeeRequest.FeeTx)
 	if err != nil {
 		log.Warnf("Failed to decode tx: %v", err)
-		sendErrorResponse("failed to decode transaction", http.StatusBadRequest, c)
+		sendError(errInvalidFeeTx, c)
 		return
 	}
 
 	feeTx := wire.NewMsgTx()
 	if err = feeTx.FromBytes(feeTxBytes); err != nil {
 		log.Warnf("Failed to deserialize tx: %v", err)
-		sendErrorResponse("unable to deserialize transaction", http.StatusBadRequest, c)
+		sendError(errInvalidFeeTx, c)
 		return
 	}
 
@@ -113,14 +117,14 @@ func payFee(c *gin.Context) {
 findAddress:
 	for _, txOut := range feeTx.TxOut {
 		if txOut.Version != scriptVersion {
-			sendErrorResponse("invalid script version", http.StatusBadRequest, c)
+			sendErrorWithMsg("invalid script version", errInvalidFeeTx, c)
 			return
 		}
 		_, addresses, _, err := txscript.ExtractPkScriptAddrs(scriptVersion,
 			txOut.PkScript, cfg.NetParams)
 		if err != nil {
 			log.Errorf("Extract PK error: %v", err)
-			sendErrorResponse("extract PK error", http.StatusBadRequest, c)
+			sendError(errInternalError, c)
 			return
 		}
 		for _, addr := range addresses {
@@ -133,7 +137,7 @@ findAddress:
 
 	if feePaid == 0 {
 		log.Warnf("FeeTx for ticket %s did not include any payments for address %s", ticket.Hash, ticket.FeeAddress)
-		sendErrorResponse("feetx did not include any payments for fee address", http.StatusBadRequest, c)
+		sendErrorWithMsg("feetx did not include any payments for fee address", errInvalidFeeTx, c)
 		return
 	}
 
@@ -141,7 +145,7 @@ findAddress:
 		dcrec.STEcdsaSecp256k1)
 	if err != nil {
 		log.Errorf("NewAddressPubKeyHash: %v", err)
-		sendErrorResponse("failed to deserialize voting wif", http.StatusInternalServerError, c)
+		sendError(errInvalidPrivKey, c)
 		return
 	}
 
@@ -149,13 +153,13 @@ findAddress:
 	ticketBytes, err := hex.DecodeString(rawTicket.Hex)
 	if err != nil {
 		log.Warnf("Failed to decode tx: %v", err)
-		sendErrorResponse("failed to decode transaction", http.StatusBadRequest, c)
+		sendError(errInternalError, c)
 		return
 	}
 	ticketTx := wire.NewMsgTx()
 	if err = ticketTx.FromBytes(ticketBytes); err != nil {
 		log.Errorf("Failed to deserialize tx: %v", err)
-		sendErrorResponse("unable to deserialize transaction", http.StatusInternalServerError, c)
+		sendError(errInternalError, c)
 		return
 	}
 
@@ -163,12 +167,12 @@ findAddress:
 	_, votingAddr, _, err := txscript.ExtractPkScriptAddrs(scriptVersion, ticketTx.TxOut[0].PkScript, cfg.NetParams)
 	if err != nil {
 		log.Errorf("ExtractPK error: %v", err)
-		sendErrorResponse("extract PK error", http.StatusInternalServerError, c)
+		sendError(errInternalError, c)
 		return
 	}
 	if len(votingAddr) == 0 {
 		log.Error("No voting address found for ticket %s", ticket.Hash)
-		sendErrorResponse("no voting address found", http.StatusInternalServerError, c)
+		sendError(errInternalError, c)
 		return
 	}
 
@@ -176,21 +180,21 @@ findAddress:
 	if votingAddr[0].Address() != wifAddr.Address() {
 		log.Warnf("Voting address does not match provided private key: "+
 			"votingAddr=%+v, wifAddr=%+v", votingAddr[0], wifAddr)
-		sendErrorResponse("voting address does not match provided private key",
-			http.StatusBadRequest, c)
+		sendErrorWithMsg("voting address does not match provided private key",
+			errInvalidPrivKey, c)
 		return
 	}
 
 	minFee, err := dcrutil.NewAmount(ticket.FeeAmount)
 	if err != nil {
 		log.Errorf("dcrutil.NewAmount: %v", err)
-		sendErrorResponse("fee error", http.StatusInternalServerError, c)
+		sendError(errInternalError, c)
 		return
 	}
 
 	if feePaid < minFee {
 		log.Warnf("Fee too small from %s: was %v, expected %v", c.ClientIP(), feePaid, minFee)
-		sendErrorResponse("fee too small", http.StatusInternalServerError, c)
+		sendError(errFeeTooSmall, c)
 		return
 	}
 
@@ -205,7 +209,7 @@ findAddress:
 	err = db.UpdateTicket(ticket)
 	if err != nil {
 		log.Errorf("InsertTicket failed: %v", err)
-		sendErrorResponse("database error", http.StatusInternalServerError, c)
+		sendError(errInternalError, c)
 		return
 	}
 
@@ -216,7 +220,7 @@ findAddress:
 		feeTxHash, err := dcrdClient.SendRawTransaction(payFeeRequest.FeeTx)
 		if err != nil {
 			log.Errorf("SendRawTransaction failed: %v", err)
-			sendErrorResponse("dcrwallet RPC error", http.StatusInternalServerError, c)
+			sendError(errInternalError, c)
 			return
 		}
 		ticket.FeeTxHash = feeTxHash
@@ -224,7 +228,7 @@ findAddress:
 		err = db.UpdateTicket(ticket)
 		if err != nil {
 			log.Errorf("InsertTicket failed: %v", err)
-			sendErrorResponse("database error", http.StatusInternalServerError, c)
+			sendError(errInternalError, c)
 			return
 		}
 

webapi/setvotechoices.go

@@ -1,7 +1,6 @@
 package webapi
 
 import (
-	"net/http"
 	"time"
 
 	"github.com/decred/vspd/database"
@@ -20,8 +19,8 @@ func setVoteChoices(c *gin.Context) {
 	walletClients := c.MustGet("WalletClients").([]*rpc.WalletRPC)
 
 	if !knownTicket {
-		log.Warnf("Invalid ticket from %s", c.ClientIP())
-		sendErrorResponse("invalid ticket", http.StatusBadRequest, c)
+		log.Warnf("Unknown ticket from %s", c.ClientIP())
+		sendError(errUnknownTicket, c)
 		return
 	}
 
@@ -30,7 +29,7 @@ func setVoteChoices(c *gin.Context) {
 	var setVoteChoicesRequest SetVoteChoicesRequest
 	if err := binding.JSON.BindBody(rawRequest, &setVoteChoicesRequest); err != nil {
 		log.Warnf("Bad setvotechoices request from %s: %v", c.ClientIP(), err)
-		sendErrorResponse(err.Error(), http.StatusBadRequest, c)
+		sendErrorWithMsg(err.Error(), errBadRequest, c)
 		return
 	}
 
@@ -38,7 +37,7 @@ func setVoteChoices(c *gin.Context) {
 	err := isValidVoteChoices(cfg.NetParams, currentVoteVersion(cfg.NetParams), voteChoices)
 	if err != nil {
 		log.Warnf("Invalid votechoices from %s: %v", c.ClientIP(), err)
-		sendErrorResponse(err.Error(), http.StatusBadRequest, c)
+		sendErrorWithMsg(err.Error(), errInvalidVoteChoices, c)
 		return
 	}
 
@@ -48,7 +47,7 @@ func setVoteChoices(c *gin.Context) {
 	err = db.UpdateTicket(ticket)
 	if err != nil {
 		log.Errorf("UpdateTicket error: %v", err)
-		sendErrorResponse("database error", http.StatusInternalServerError, c)
+		sendError(errInternalError, c)
 		return
 	}
 

webapi/ticketstatus.go

@@ -1,7 +1,6 @@
 package webapi
 
 import (
-	"net/http"
 	"time"
 
 	"github.com/decred/vspd/database"
@@ -18,15 +17,15 @@ func ticketStatus(c *gin.Context) {
 	knownTicket := c.MustGet("KnownTicket").(bool)
 
 	if !knownTicket {
-		log.Warnf("Invalid ticket from %s", c.ClientIP())
-		sendErrorResponse("invalid ticket", http.StatusBadRequest, c)
+		log.Warnf("Unknown ticket from %s", c.ClientIP())
+		sendError(errUnknownTicket, c)
 		return
 	}
 
 	var ticketStatusRequest TicketStatusRequest
 	if err := binding.JSON.BindBody(rawRequest, &ticketStatusRequest); err != nil {
 		log.Warnf("Bad ticketstatus request from %s: %v", c.ClientIP(), err)
-		sendErrorResponse(err.Error(), http.StatusBadRequest, c)
+		sendErrorWithMsg(err.Error(), errBadRequest, c)
 		return
 	}
 

webapi/webapi.go

@@ -221,7 +221,7 @@ func sendJSONResponse(resp interface{}, c *gin.Context) {
 	dec, err := json.Marshal(resp)
 	if err != nil {
 		log.Errorf("JSON marshal error: %v", err)
-		sendErrorResponse("failed to marshal json", http.StatusInternalServerError, c)
+		sendError(errInternalError, c)
 		return
 	}
 
@@ -231,8 +231,22 @@ func sendJSONResponse(resp interface{}, c *gin.Context) {
 	c.AbortWithStatusJSON(http.StatusOK, resp)
 }
 
-func sendErrorResponse(errMsg string, code int, c *gin.Context) {
-	resp := gin.H{"error": errMsg}
+// sendError returns an error response to the client using the default error
+// message.
+func sendError(e apiError, c *gin.Context) {
+	msg := e.defaultMessage()
+	sendErrorWithMsg(msg, e, c)
+}
+
+// sendErrorWithMsg returns an error response to the client using the provided
+// error message.
+func sendErrorWithMsg(msg string, e apiError, c *gin.Context) {
+	status := e.httpStatus()
+
+	resp := gin.H{
+		"code":    int(e),
+		"message": msg,
+	}
 
 	// Try to sign the error response. If it fails, send it without a signature.
 	dec, err := json.Marshal(resp)
@@ -243,5 +257,5 @@ func sendErrorResponse(errMsg string, code int, c *gin.Context) {
 		c.Writer.Header().Set("VSP-Server-Signature", hex.EncodeToString(sig))
 	}
 
-	c.AbortWithStatusJSON(code, resp)
+	c.AbortWithStatusJSON(status, resp)
 }