From ee3e12f3228b876b9fff8466b6d9ad3b7ea81816 Mon Sep 17 00:00:00 2001
From: Rasmus Dahlberg <rasmus.dahlberg@kau.se>
Date: Thu, 22 Oct 2020 16:32:15 +0200
Subject: added start on get-entries code path

If the provided range is (mostly) valid the corresponding log entries
are fetched from the Trillian back-end and returned as a JSON object.
---
 handler.go | 39 +++++++++++++++++++++++++++++++++++++--
 type.go    | 28 +++++++++++++++++++++++++++-
 2 files changed, 64 insertions(+), 3 deletions(-)

diff --git a/handler.go b/handler.go
index 6c81d3e..4d2ace8 100644
--- a/handler.go
+++ b/handler.go
@@ -120,9 +120,44 @@ func getEntries(ctx context.Context, i *instance, w http.ResponseWriter, r *http
 	if err := request.Unpack(r); err != nil {
 		return http.StatusBadRequest, err
 	}
-	glog.Infof("valid request: %v", request)
 
-	return http.StatusOK, nil // TODO
+	trillianRequest := trillian.GetLeavesByRangeRequest{
+		LogId:      i.logID,
+		StartIndex: request.Start,
+		Count:      request.End - request.Start + 1,
+	}
+	trillianResponse, err := i.client.GetLeavesByRange(ctx, &trillianRequest)
+	if err != nil {
+		return http.StatusInternalServerError, fmt.Errorf("backend GetLeavesByRange request failed: %v", err)
+	}
+
+	// Santity check
+	if len(trillianResponse.Leaves) > int(request.End-request.Start+1) {
+		return http.StatusInternalServerError, fmt.Errorf("backend GetLeavesByRange returned too many leaves: %d for [%d,%d]", len(trillianResponse.Leaves), request.Start, request.End)
+	}
+	for i, leaf := range trillianResponse.Leaves {
+		if leaf.LeafIndex != request.Start+int64(i) {
+			return http.StatusInternalServerError, fmt.Errorf("backend GetLeavesByRange returned unexpected leaf index: wanted %d, got %d", request.Start+int64(i), leaf.LeafIndex)
+		}
+
+		glog.Infof("Entry(%d) => %v", request.Start+int64(i), leaf.GetLeafValue())
+	}
+	// TODO: use the returned root for tree_size santity checking against start?
+
+	w.Header().Set("Content-Type", "application/json")
+	data, err := NewGetEntriesResponse(trillianResponse.Leaves)
+	if err != nil {
+		return http.StatusInternalServerError, fmt.Errorf("failed createing GetEntriesResponse: %v", err)
+	}
+	json, err := json.Marshal(&data)
+	if err != nil {
+		return http.StatusInternalServerError, fmt.Errorf("failed json-encoding GetEntriesResponse: %v", err)
+	}
+	_, err = w.Write(json)
+	if err != nil {
+		return http.StatusInternalServerError, fmt.Errorf("failed writing get-entries response: %v", err)
+	}
+	return http.StatusOK, nil
 }
 
 // getAnchors provides a list of configured trust anchors
diff --git a/type.go b/type.go
index dcb2a9a..11fafe1 100644
--- a/type.go
+++ b/type.go
@@ -8,6 +8,7 @@ import (
 	"net/http"
 
 	"github.com/google/certificate-transparency-go/tls"
+	"github.com/google/trillian"
 )
 
 // StFormat defines a particular StItem type that is versioned
@@ -104,7 +105,7 @@ type AddEntryRequest struct {
 // GetEntriesRequest is a collection of get-entry input parameters
 type GetEntriesRequest struct {
 	Start int64
-	End int64
+	End   int64
 }
 
 func (r *GetEntriesRequest) Unpack(httpRequest *http.Request) error {
@@ -129,3 +130,28 @@ func (r *GetEntriesRequest) Unpack(httpRequest *http.Request) error {
 	// TODO: check that end is not past the most recent STH. Yes -> truncate
 	return nil
 }
+
+type GetEntryResponse struct {
+	Leaf      string   `json:"leaf"`
+	Signature string   `json:"signature"`
+	Chain     []string `json:chain`
+}
+
+func NewGetEntryResponse(leaf []byte) GetEntryResponse {
+	return GetEntryResponse{
+		Leaf: base64.StdEncoding.EncodeToString(leaf),
+		// TODO: add signature and chain
+	}
+}
+
+type GetEntriesResponse struct {
+	Entries []GetEntryResponse `json:"entries"`
+}
+
+func NewGetEntriesResponse(leaves []*trillian.LogLeaf) (GetEntriesResponse, error) {
+	entries := make([]GetEntryResponse, 0, len(leaves))
+	for _, leaf := range leaves {
+		entries = append(entries, NewGetEntryResponse(leaf.GetLeafValue())) // TODO: add signature and chain
+	}
+	return GetEntriesResponse{entries}, nil
+}
-- 
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