txn: don't try to decode request bodies > raft.SuggestedMaxDataSize

agent/txn_endpoint.go

@@ -4,6 +4,7 @@ import (
 	"encoding/base64"
 	"fmt"
 	"net/http"
+	"strconv"
 	"strings"
 	"time"
 
@@ -98,6 +99,18 @@ func isWrite(op api.KVOp) bool {
 // a boolean, that if false means an error response has been generated and
 // processing should stop.
 func (s *HTTPServer) convertOps(resp http.ResponseWriter, req *http.Request) (structs.TxnOps, int, bool) {
+
+	sizeStr := req.Header.Get("Content-Length")
+	if sizeStr != "" {
+		if size, err := strconv.Atoi(sizeStr); err != nil {
+			fmt.Fprintf(resp, "Failed to parse Content-Length: %v", err)
+			return nil, 0, false
+		} else if size > int(s.agent.config.KVMaxValueSize) {
+			fmt.Fprintf(resp, "Request body too large, max size: %v bytes", s.agent.config.KVMaxValueSize)
+			return nil, 0, false
+		}
+	}
+
 	// Note the body is in API format, and not the RPC format. If we can't
 	// decode it, we will return a 400 since we don't have enough context to
 	// associate the error with a given operation.

agent/txn_endpoint_test.go

@@ -7,6 +7,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"reflect"
+	"strconv"
 	"strings"
 	"testing"
 	"time"
@@ -602,3 +603,50 @@ func TestTxnEndpoint_UpdateCheck(t *testing.T) {
 	}
 	verify.Values(t, "", txnResp, expected)
 }
+
+func TestConvertOps_ContentLength(t *testing.T) {
+	a := NewTestAgent(t, t.Name(), "")
+	defer a.Shutdown()
+
+	jsonBody := `[
+     {
+         "KV": {
+             "Verb": "set",
+             "Key": "key1",
+             "Value": "aGVsbG8gd29ybGQ="
+         }
+     }
+ ]`
+
+	tests := []struct {
+		contentLength string
+		ok            bool
+	}{
+		{"", true},
+		{strconv.Itoa(len(jsonBody)), true},
+		{strconv.Itoa(raft.SuggestedMaxDataSize), true},
+		{strconv.Itoa(raft.SuggestedMaxDataSize + 100), false},
+	}
+
+	for _, tc := range tests {
+		t.Run("contentLength: "+tc.contentLength, func(t *testing.T) {
+			resp := httptest.NewRecorder()
+			var body bytes.Buffer
+
+			// Doesn't matter what the request body size actually is, as we only
+			// check 'Content-Length' header in this test anyway.
+			body.WriteString(jsonBody)
+
+			req := httptest.NewRequest("POST", "http://foo.com", &body)
+			req.Header.Add("Content-Length", tc.contentLength)
+
+			_, _, ok := a.srv.convertOps(resp, req)
+			if ok != tc.ok {
+				t.Fatal("ok != tc.ok")
+			}
+
+		})
+
+	}
+
+}