Expose an endpoint with all of the witness keys (#114)

Each of the environments will be configured differently, and thus using the single embedded config on both the client and the server to enumerate the witnesses was brittle/broken.

This change temporarily breaks the client until all distributors are updated to have the new endpoint, but we're still at v0 and I'll get this rolled out within a matter of hours so I'll avoid the tax of doing this the staged way. This is also a breaking change at the code level, but again, this is v0 and we can flex that licence.

api/http.go

@@ -30,4 +30,7 @@ const (
 	// HTTPGetLogs is the path of the URL to get a list of all logs the
 	// distributor is aware of.
 	HTTPGetLogs = "/distributor/v0/logs"
+	// HTTPGetWitnesses is the path of the URL to get a list of all witnesses
+	// that the distributor is aware of.
+	HTTPGetWitnesses = "/distributor/v0/witnesses"
 )

client/client.go

@@ -61,6 +61,24 @@ func (d *RestDistributor) GetLogs() ([]LogID, error) {
 	return r, nil
 }
 
+// GetWitnesses returns the verifier keys for all witnesses that
+// the distributor knows about.
+func (d *RestDistributor) GetWitnesses() ([]string, error) {
+	u, err := url.Parse(d.baseURL + api.HTTPGetWitnesses)
+	if err != nil {
+		return nil, err
+	}
+	r := make([]string, 0)
+	bs, err := d.fetchData(u)
+	if err != nil {
+		return nil, err
+	}
+	if err := json.Unmarshal(bs, &r); err != nil {
+		return nil, err
+	}
+	return r, nil
+}
+
 // GetCheckpointN returns the freshest checkpoint for the log that at least N witnesses
 // have provided signatures for.
 func (d *RestDistributor) GetCheckpointN(l LogID, n uint) ([]byte, error) {

cmd/client/client.go

@@ -40,11 +40,11 @@ var (
 func main() {
 	flag.Parse()
 
-	ls := getLogsOrDie()
-	ws := getWitnessesOrDie()
-
 	d := client.NewRestDistributor(*baseURL, http.DefaultClient)
 
+	ls := getLogsOrDie()
+	ws := getWitnessesOrDie(d)
+
 	logs, err := d.GetLogs()
 	if err != nil {
 		glog.Exitf("❌ Failed to enumerate logs: %v", err)
@@ -91,10 +91,19 @@ func getLogsOrDie() map[string]config.LogInfo {
 	return r
 }
 
-func getWitnessesOrDie() map[uint32]note.Verifier {
-	r, err := config.DefaultWitnesses()
+func getWitnessesOrDie(c *client.RestDistributor) map[uint32]note.Verifier {
+	rawWs, err := c.GetWitnesses()
 	if err != nil {
-		glog.Exitf("Failed to get witness config: %v", err)
+		glog.Exitf("Failed to GetWitnesses() from distributor: %v", err)
 	}
-	return r
+
+	ws := make(map[uint32]note.Verifier)
+	for _, w := range rawWs {
+		wSigV, err := f_note.NewVerifierForCosignatureV1(w)
+		if err != nil {
+			glog.Exitf("Invalid witness public key retrieved from distributor: %v: %v", w, err)
+		}
+		ws[wSigV.KeyHash()] = wSigV
+	}
+	return ws
 }

cmd/internal/distributor/distributor.go

@@ -71,22 +71,31 @@ var (
 // NewDistributor returns a distributor that will accept checkpoints from
 // the given witnesses, for the given logs, and persist its state in the
 // database provided. Callers must call Init() on the returned distributor.
-// `ws` is a map from witness ID (verifier key name) to the note verifier.
+// `ws` is a map from witness raw verifier string to the note verifier.
 // `ls` is a map from log ID (github.com/transparency-dev/formats/log.ID) to log info.
 func NewDistributor(ws map[string]note.Verifier, ls map[string]config.LogInfo, db *sql.DB) (*Distributor, error) {
+	witsByID := make(map[string]note.Verifier, len(ws))
+	rawVKeys := make([]string, 0, len(ws))
+	for k, v := range ws {
+		rawVKeys = append(rawVKeys, k)
+		witsByID[v.Name()] = v
+	}
+	sort.Strings(rawVKeys)
 	d := &Distributor{
-		ws: ws,
-		ls: ls,
-		db: db,
+		ws:      ws,
+		witKeys: rawVKeys,
+		ls:      ls,
+		db:      db,
 	}
 	return d, d.init()
 }
 
 // Distributor persists witnessed checkpoints and allows querying of them.
 type Distributor struct {
-	ws map[string]note.Verifier
-	ls map[string]config.LogInfo
-	db *sql.DB
+	ws      map[string]note.Verifier
+	witKeys []string
+	ls      map[string]config.LogInfo
+	db      *sql.DB
 }
 
 // GetLogs returns a list of all log IDs the distributor is aware of, sorted
@@ -100,6 +109,12 @@ func (d *Distributor) GetLogs(ctx context.Context) ([]string, error) {
 	return r, nil
 }
 
+// GetLogs returns a list of all witness verifier keys that the distributor is
+// aware of, sorted by the key.
+func (d *Distributor) GetWitnesses(ctx context.Context) ([]string, error) {
+	return d.witKeys, nil
+}
+
 // GetCheckpointN gets the largest checkpoint for a given log that has at least `n` signatures.
 func (d *Distributor) GetCheckpointN(ctx context.Context, logID string, n uint32) ([]byte, error) {
 	counterCheckpointGetNRequests.Inc()

cmd/internal/http/server.go

@@ -24,8 +24,8 @@ import (
 	"strconv"
 
 	"github.com/golang/glog"
-	"github.com/transparency-dev/distributor/api"
 	"github.com/gorilla/mux"
+	"github.com/transparency-dev/distributor/api"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
 )
@@ -35,6 +35,9 @@ type Distributor interface {
 	// GetLogs returns a list of all log IDs the distributor is aware of, sorted
 	// by the ID.
 	GetLogs(ctx context.Context) ([]string, error)
+	// GetWitnesses returns a list of all witness verifier keys the distributor is
+	// aware of, sorted by the ID.
+	GetWitnesses(ctx context.Context) ([]string, error)
 	// GetCheckpointN gets the largest checkpoint for a given log that has at least `n` signatures.
 	GetCheckpointN(ctx context.Context, logID string, n uint32) ([]byte, error)
 	// GetCheckpointWitness gets the largest checkpoint for the log that was witnessed by the given witness.
@@ -115,7 +118,7 @@ func (s *Server) getCheckpointWitness(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
-// getLogs returns a list of all logs the witness is aware of.
+// getLogs returns a list of all logs the distributor is aware of.
 func (s *Server) getLogs(w http.ResponseWriter, r *http.Request) {
 	logs, err := s.d.GetLogs(r.Context())
 	if err != nil {
@@ -133,6 +136,24 @@ func (s *Server) getLogs(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+// getWitnesses returns a list of all witnesses the distributor is aware of.
+func (s *Server) getWitnesses(w http.ResponseWriter, r *http.Request) {
+	witnesses, err := s.d.GetWitnesses(r.Context())
+	if err != nil {
+		http.Error(w, fmt.Sprintf("failed to get witness list: %v", err), http.StatusInternalServerError)
+		return
+	}
+	witnessList, err := json.Marshal(witnesses)
+	if err != nil {
+		http.Error(w, fmt.Sprintf("failed to convert witness list to JSON: %v", err), http.StatusInternalServerError)
+		return
+	}
+	w.Header().Set("Content-Type", "text/json")
+	if _, err := w.Write(witnessList); err != nil {
+		glog.Errorf("w.Write(): %v", err)
+	}
+}
+
 // RegisterHandlers registers HTTP handlers for witness endpoints.
 func (s *Server) RegisterHandlers(r *mux.Router) {
 	logStr := "{logid:[a-zA-Z0-9-]+}"
@@ -141,6 +162,7 @@ func (s *Server) RegisterHandlers(r *mux.Router) {
 	r.HandleFunc(fmt.Sprintf(api.HTTPCheckpointByWitness, logStr, witStr), s.update).Methods("PUT")
 	r.HandleFunc(fmt.Sprintf(api.HTTPCheckpointByWitness, logStr, witStr), s.getCheckpointWitness).Methods("GET")
 	r.HandleFunc(api.HTTPGetLogs, s.getLogs).Methods("GET")
+	r.HandleFunc(api.HTTPGetWitnesses, s.getWitnesses).Methods("GET")
 }
 
 func httpForCode(c codes.Code) int {

cmd/main.go

@@ -193,12 +193,8 @@ func getWitnessesOrDie() map[string]note.Verifier {
 		glog.Exitf("Failed to unmarshal witness config: %v", err)
 	}
 
-	r := make(map[string]note.Verifier, len(w))
-	for _, v := range w {
-		r[v.Name()] = v
-	}
-	glog.Infof("Configured with %d witness keys: %s", len(r), r)
-	return r
+	glog.Infof("Configured with %d witness keys: %s", len(w), w)
+	return w
 }
 
 type witFlags []string

config/config.go

@@ -41,8 +41,8 @@ func DefaultLogs() (map[string]LogInfo, error) {
 }
 
 // DeafultWitnesses returns a parsed representation of the embedded WitnessesYAML config.
-// The returned map is keyed by the witness verifier key hash.
-func DefaultWitnesses() (map[uint32]note.Verifier, error) {
+// The returned map is keyed by the raw verifier key string.
+func DefaultWitnesses() (map[string]note.Verifier, error) {
 	return ParseWitnessesConfig(WitnessesYAML)
 }
 
@@ -80,22 +80,21 @@ func ParseLogConfig(y []byte) (map[string]LogInfo, error) {
 }
 
 // ParseWitnessesConfig parses the passed in witnesses config, and returns a map keyed
-// by witness verified key hash.
-func ParseWitnessesConfig(y []byte) (map[uint32]note.Verifier, error) {
+// by the raw verifier key string.
+func ParseWitnessesConfig(y []byte) (map[string]note.Verifier, error) {
 	witCfg := struct {
 		Witnesses []string `yaml:"Witnesses"`
 	}{}
 	if err := yaml.Unmarshal(y, &witCfg); err != nil {
 		return nil, fmt.Errorf("failed to unmarshal witness config: %v", err)
 	}
-	ws := make(map[uint32]note.Verifier)
+	ws := make(map[string]note.Verifier)
 	for _, w := range witCfg.Witnesses {
 		wSigV, err := f_note.NewVerifierForCosignatureV1(w)
 		if err != nil {
 			return nil, fmt.Errorf("invalid witness public key: %v", err)
 		}
-		ws[wSigV.KeyHash()] = wSigV
+		ws[w] = wSigV
 	}
-
 	return ws, nil
 }